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Paul D. Thompson, M.D.
Introduction
Aortic stenosis (AS) was implicated in 8% of the nontraumatic, exertion-related deaths reported by Jokl and Melzer in their review of medical reports published between 1921 and 1939.1 Unfortunately, despite the widespread appreciation of the dangers of exertion with valvular AS, this entity remains an important cause of exercise-related cardiac events and still accounts for 4% of sudden deaths among young athletes.2,3 Furthermore, the evaluation of cardiac murmurs and valvular abnormalities remains a frequent reason for cardiology consultation. This paper will address the evaluation and management of valvular heart disease in competitive and recreational athletes.
Evaluating valvular heart disease in athletes is not easy. The physiologic cardiac adaptations to exercise training create innocent flow murmurs which are difficult to differentiate from normal. Blood flow is laminar and without turbulence until a critical Reynolds number (Re) is exceeded. Re is determined by the following formula
|
Re = Average Velocity x tube diameter x fluid density Fluid viscosity 4 |
Further complicating the treatment of valvular disease in athletes is the lack of studies evaluating various management strategies in such patients. Indeed, there are few trials of valvular heart disease treatment approaches in nonathletic populations, and much of the available literature is based on single center reports.7 An additional problem is that athletes, because of their exercise activity, may present at an earlier disease stage than other patients. This is a major issue because the appearance of symptoms is an important indicator that valvular repair or replacement may be necessary. Physicians do not want to intervene too soon in athletes with symptoms produced by extreme exertion because of the immediate risk of surgery, the finite life of many valvular protheses, and the need for life-long anticoagulant therapy after some valve replacements.
The athlete's attitude can also complicate the decision. Some athletes deny symptoms and try to avoid surgery even with life-threatening conditions. Others prefer early intervention if waiting would mean restricted physical activity or reduced athletic performance. The latter patients need to understand the immediate risks of surgery vs its long-term benefits and also the fact that few valvular repair procedures produce the performance characteristics of a normal native valve. In the final analysis there is no substitute for a sympathetic explanation and definitive recommendations as to how and why the athlete should proceed in his or her best interest. We often recommend second opinions if the athlete seems reluctant to follow a recommended plan. We provide referrals and scheduling assistance to ensure the athlete is evaluated by a reputable physician at a recognized institution.
The Cardiac Examination of Athletes for Valvular Heart Disease
A complete description of the cardiac examination of athletes is beyond the scope of this paper. The following section emphasizes clinical principles useful in evaluating athletes for suspected valvular disease.
The examination of athletes with possible valvular disease is more complete than the often cursory examination routinely performed as part of the preparticipation physical. All cardiac evaluations should start with an accurate blood pressure measurement in both arms. The blood pressure should be measured by someone trained to avoid the digit selection and rounding to tens that is common in most blood pressure "determinations." The average systolic pressure is several millimeters higher in the right arm probably because of the more direct course of the pulse wave to the innominate and right subclavian arteries. A systolic pressure >15 mm higher in the right arm, if associated with a systolic ejection murmur, suggests supravalvular AS8 which is an occasional cause of exercise-related sudden cardiac death.3 A widened pulse pressure suggests a regurgitant murmur such as aortic insufficiency (AI). The high-pitched diastolic murmur of AI can be difficult to hear without special attention, but a pulse pressure >40 mm Hg should prompt a careful search for this murmur with the patient leaning forward and holding his or her breath at end expiration. The AI murmur is often best heard over the sternum because bone transmits the high-frequency murmur more readily.
Elevated blood pressure in a young athlete requires simultaneous palpation of the radial and femoral pulses to exclude a radial-femoral pulse delay suggestive of aortic coarctation. It is often incorrectly assumed that the mere presence of a femoral pulse excludes coarctation, but some patients can reconstitute a palpable femoral pulse via collaterals. In these patients it is the delayed impulse between the radial (or brachial) and femoral pulse that suggests the diagnosis.9
Evaluating the carotid pulse is the most important palpation maneuver in athletes because AS remains a frequent, easily identified cause of sudden cardiac death. A carotid pulse that is low volume, has a slow upstroke, or is difficult to locate should increase suspicion of important AS.
Cardiac auscultation is an important part of evaluating valvular disease in athletes even in the present era of echocardiography. It is possible to both over and under-estimate the severity of valvular lesions with either echocardiography or the physical examination. The best decisions are made when the results of several examination techniques are compared for agreement or discrepancies. The physician should avoid relying exclusively on clinical, echocardiographic, or catheterization data alone. Consequently the physical examination is a key component both in deciding who requires further study and in evaluating the additional data.
During cardiac auscultation the examiner should ignore any obvious murmur and proceed with a sequential systematic examination of the heart sounds, possible gallops and clicks, diastolic murmurs, and finally systolic murmurs. If too much attention is given initially to any obvious finding, such as a systolic murmur, it is often difficult to appreciate more subtle findings that can contribute to the correct diagnosis. The auscultatory examination should start with an assessment of the intensity of S1 which is produced by closure of the mitral and tricuspid valves. The intensity of S1 is partly determined by the degree of leaflet separation at the onset of ventricular contraction. If the leaflets are widely separated to accommodate delayed ventricular filling such as with mitral stenosis, the valve leaflets travel farther at the onset of systole and S1 is loud. In contrast, if the leaflets have been partially closed by the regurgitant jet of AI, S1 is soft. Both AI and isolated mitral stenosis (MS) are notoriously difficult to hear and often require special maneuvers. The intensity of S1 helps indicate when these additional maneuvers are required.
S2 is produced by closure of the aortic followed by the pulmonic valves. During inspiration, filling of the right ventricle is augmented. The larger volume of blood in the right ventricle shifts the intraventricular septum leftward, compromises (LV) filling, and reduces the LV stroke volume.10 This hastens aortic closure so that the aortic valve closes earlier in the cardiac cycle during inspiration. On the right side, the larger right ventricular volume delays pulmonic valve closure. Both the earlier aortic closure and the delayed pulmonic closure increase the splitting of S2 during inspiration. This is best appreciated in the seated position. In the supine position venous return from the legs can nearly maximize right ventricular filling so that any additional increase in the splitting of S2 is difficult to detect. This is especially true in endurance athletes whose plasma volume can average 800 ml larger than comparison subjects.11 Part of this increased plasma volume shifts to the central circulation in the supine position. During the expiratory phase of the cardiac cycle, aortic and pulmonic closure occur almost simultaneously and S2 should be single or nearly so. If there is an intracardiac connection between the right and left sides of the heart, such as an atrial septal defect (ASD), there is no or little differential in right and left cardiac filling during respiration. Right ventricular filling is also increased from left to right intracardiac shunting which increases the right ventricular stroke volume. S2, therefore, is often widely split, does not move during respiration, and fails to close during expiration. ASD's often are accompanied by a systolic murmur that has many of the characteristics of a pulmonic flow murmur. The behavior of S2 is useful in separating these two conditions.
The examiner should then listen in diastole for an S3 or S4 gallop and in systole for any ejection clicks suggestive of pulmonic or aortic valvular stenosis or any midsystolic clicks suggestive of mitral valve prolapse. Many athletes have S3 and S4 gallops which are of no importance unless the gallops are loud or associated with other abnormalities. The examiner should then listen in diastole for the murmurs of AI and MS and finally to any systolic murmurs. Systole should be examined last because these murmurs are usually the most obvious.
The initial auscultatory exam is performed with the athlete seated. As discussed above this reduces the chance of producing a flow murmur, facilitates hearing AI, and maximizes splitting of the second sound. In addition, the upright position reduces ventricular volume and increases the chance of detecting a murmur in obstructive hypertrophic cardiomyopathy. The sequence of auscultation is then repeated in the supine and left lateral positions. The later position facilitates detecting the murmurs of mitral stenosis and regurgitation. If there is any suspicion of either hypertrophic cardiomyopathy or mitral valve prolapse, the athletes should also be examined standing and squatting. Variations in ventricular volume alter the timing of midsystolic clicks in mitral valve prolapse and thereby facilitate its identification. Squatting increases ventricular afterload which decrease the murmur of obstructive hypertrophic cardiomyopathy whereas standing often increases the murmur if obstruction is present.
The electrocardiogram (ECG) in athletes is often not useful in following those with valvular abnormalities because athletes may normally show evidence of right ventricular and LV enlargement, T wave abnormalities, and atrial abnormalities. Nevertheless, the ECG is a low-cost alternative in following asymptomatic or mildly symptomatic athletes between routine echocardiographic studies. Charting the ECG voltage in leads V5 and V6 as well as the T wave configuration in athletes with AI or mitral regurgitation (MR) helps identify changes in the cardiac status. Any changes in ECG voltage or T wave orientation should prompt repeat echocardiographic examination to ensure that the lesion has not progressed unexpectedly.
Doppler echocardiography is both the primary mechanism used to evaluate valvular lesions at presentation and to follow these conditions over time. Most cardiologists routinely refer athletes with possible valvular involvement for echocardiography unless the murmur is unquestionably a flow murmur on careful physical examination. Flow murmurs in young and older athletes are generally grade 1 or 2 in intensity, systolic, associated with normal splitting of S2, not associated with other abnormal sounds or diastolic murmurs, and not altered by the Valsalva maneuver.7 The major limitation with Doppler echocar-diography is that it is often too sensitive and detects trivial MR in 69% of athletes and trivial Tricuspio regurgitation in 76%.12 Physicians unaware of this fact and uncertain of the findings on physical examination may overestimate the importance of the echocardiographic results.
The Management of Athletes with Valvular Disease
The American College of Cardiology and the American Heart Association published "Guidelines for the Management of Patients with Valvular Heart Disease" in 1998. This document provides an excellent summary 7 on how to manage the general patient with this problem. "Recommendations for Determining Eligibility for Competition in Athletes with Cardiovascular Abnormalities, the 26th Bethesda Conference" were published by the same two organizations in 1994 and included a section on athletes with acquired valvular heart disease.13 The following section will summarize issues from these two documents and provide additional information relevant to physicians caring for athletes.
Valvular Aortic Stenosis (AS)
Valvular aortic stenosis (AS) remains a frequent cause of exertion-related sudden death in young athletes and an occasional cause of exercise-related deaths in adults. The normal aortic valve orifice is approximately 3 cm to 4 cm2 and must be reduced by 75% of normal before causing significant hemodynamic obstruction.7 Mild, moderate, and severe AS are classified as an aortic valve area >1.5, 1-1.5, and <1.0 cm2 respectively. Severe AS should produce a mean resting gradient of at least 50 mm Hg if cardiac output is normal. These values are not normalized for body surface area. The hemodynamic significance of any specified aortic valve area depends on the cardiac output. Since muscle mass is a determinant of resting cardiac output, larger individuals may have more severe hemodynamic impairment despite a larger absolute aortic valve area. This may be an issue in athletes with an increased body size and muscle mass. Consequently, the calculated aortic valve area and classification of the severity of disease should be considered as only estimates and must be correlated with other findings.
AS is typified by a long asymptomatic period. Common symptoms of severe AS when they do occur include angina, syncope or near syncope, and heart failure. Sudden cardiac death may also be the first symptom, but this is rare. This presentation is more frequent in younger subjects with congenital AS, but does occur in adults. The incidence of sudden death without prior symptoms is estimated to be <1% of AS patients per year.7 The rate of narrowing of the aortic valve in individual patients is highly variable and unpredictable. Over 50% of patients with AS show little or no progression over 3 to 9 years, but the average rate of aortic valve narrowing is 0.12 cm2 per year.7 Consequently, patients with AS, once identified, require careful follow-up.
The initial evaluation of AS patients requires a physical examination, ECG, and Doppler echocardiographic study. Estimation of the severity of AS is based on an evaluation of the results from all three examination modalities although the aortic valve area is based primarily on the Doppler echocardiographic results. Cardiac catheterization is required to help clarify the severity of the AS if the noninvasive testing and clinical evaluations are contradictory. Even cardiac catheterization can incorrectly asses the aortic valve area especially if the oxygen uptake value used to calculate the Fick cardiac output is estimated from body size and not directly measured by expired gas collection. In addition, the degree of stenosis can be overestimated by gradient calculations with concomitant AI since the regurgitant volume increases stoke volume beyond that measured by the Fick calculation as forward flow. Coronary angiography is required before valve surgery to detect any coronary artery disease.
Athletes with mild AS can participate in all competitive sports if they are asymptomatic and have a normal exercise response.13 Athletes with moderate AS should be restricted to sports with low static and dynamic requirements (See Table for Examples of Intensity Classifications) although selected athletes can participate in moderate static and dynamic intensity sports provided they have a normal ST segment, cardiac rhythm, and blood pressure response to exercise testing and are not symptomatic. Athletes with severe AS should be restricted from competitive athletics even if they are asymptomatic. Exercise testing in these athletes is useful in documenting that they are truly without symptoms and to ensure that they do not develop exercise-induced hypotension. Exercise-induced hypotension is a bad prognostic sign and should prompt consideration for aortic valve surgery even in the absence of symptoms.
|
Table 1. Examples of the Classification of Sports | |||
|
Low Dynamic |
Moderate Dynamic |
High Dynamic | |
|
Low static: |
Bowling |
Baseball |
Distance Running |
|
Moderate static: |
Motocross |
Sprinting |
Basketball |
|
High static: |
Rock climbing |
Wrestling |
Boxing |
|
This table is modified from that of Mitchell et al. 29 Dynamic exercise refers to "aerobic" activities whereas Static refers to exercise requiring sustained muscle contraction. Any rigid separation of sports into dynamic and static components is arbitrary because modern training for most sports requires both static and dynamic exertion. | |||
Aortic valve replacement is advocated for patients with severe AS once symptoms appear. This decision can be more difficult in athletes; they are at an undefined, but definite risk of sudden death during exercise, and they may present with symptoms earlier in their disease course because vigorous exercise provokes symptoms. There are no studies to address the issue as to whether valve replacement can be delayed if symptoms occur only with extreme exertion. Clinicians must balance the immediate and delayed risk of valve replacement against the risks of not proceeding. Despite such considerations, our bias is to proceed fairly promptly to surgery in athletes with severe AS at the onset of symptoms. There is little additional benefit to waiting since surgery is inevitable in this situation. Also, there is the risk inherent in waiting and the possibility that LV hypertrophy will develop or worsen. LV hypertrophy is in its own right a risk factor for sudden cardiac death in the general population and among athletes.14
The decision is considerably more complex in athletes who are asymptomatic and yet have severe AS. It is generally thought that the immediate risk of surgery and the risks associated with a valvular prosthesis such as anticoagulation outweigh the benefits of proceeding. Among the asymptomatic patient group, those with exercise-induced hypotension, systolic dysfunction, and marked LV hypertrophy are probably at increased risk and should be considered for valve replacement. Some experts also consider exercise ST depression to represent an additional risk factor and suggest that sudden death is extremely rare in children with aortic stenosis who have no ST depression with exercise. 15 Asymptomatic athletes with severe AS should undergo exercise testing to document their lack of symptoms and should be restricted from competing and training. Our bias even in these asymptomatic athletes is to proceed to aortic valve replacement in the near future for the following reasons: surgery has relatively low risk in healthy subjects; prolonged pressure overload has deleterious effects on the left ventricle; many active patients are reluctant to avoid vigorous exercise for a prolonged period of time.
Chronic Aortic Insufficiency (AI)
Chronic AI represents a combined volume and pressure overload on the left ventricle. Chronic AI can be well-tolerated for decades, but many patients with moderate and severe regurgitation experience a gradual progression from normal to abnormal LV function characterized by LV enlargement, reduced contractility, and decreased ejection fraction. Most patients developing LV dysfunction present with early symptoms of heart failure including exercise intolerance, dyspnea, and exercise-induced presyncope before LV function is severe. Some patients, however, do not develop sentinel symptoms and present with marked LV enlargement and a severely dysfunctional left ventricle.7
Early in the course of left ventricular dysfunction the left ventricle (LV) can recover after aortic valve replacement probably because the dysfunction was primarily due to volume overload. If the volume overload has been persistent and produced severe chamber enlargement with LV dysfunction, the myocardial dysfunction is not wholly reversible despite correction of the valvular lesion. Consequently, the severity of LV dilatation and dysfunction are the key determinants of postoperative ventricular function and survival.
Athletes with AI should be carefully questioned for exercise-induced signs of early heart failure. The physical examination should include a search for stigmata of Marfan syndrome since many Marfan patients have important AI. They should also have a baseline ECG, echocardiogram with careful measurement of LV and left atrial diameters, and an exercise stress test. The baseline ECG is used to evaluate LV voltage and T wave changes over time. The exercise test is to document functional capacity and the absence of symptoms and exercise-induced arrhythmia. It is useful to chart the ECG voltage and T waves in leads II, AVL, V5, and V6 as well as the echocardiographic LV and left atrial dimensions. These can then be followed sequentially for evidence of early LV dysfunction.
The general population of patients with moderate to severe AI, no symptoms, and normal LV function has a reasonably good near-term prognosis. Among seven studies including 490 patients who were followed for a mean of 6.4 years, sudden death occurred in only six and progression to symptoms or LV dysfunction occurred at a rate of 4.3% per annum.7 This is not a trivial rate of progression, however, since 21% of patients worsened over five years. It is not clear how exercise training would affect these results. Dynamic exercise acutely increases heart rate which shortens diastole and the time available for aortic regurgitation. On the other hand, exercise training in normals induces bradycardia which prolongs AI and theoretically hastens LV dysfunction. We are unaware of studies that have examined the effects of endurance training in AI patients so the ultimate effect of athletic training and competition on AI has not been determined. Patients with important AI are routinely advised to avoid static exertion because the increased afterload acutely increases aortic regurgitation, although if static effort actually affects prognosis has not been examined.
Athletes with mild or moderate AI, minimal LV enlargement,They should be cautioned to report any new symptoms and they should have a repeat echocardiogram six to 12 months after the initial visit to document disease stability and then every two to three years thereafter.7
Selected athletes with moderate AI and moderate LV enlargement can participate in sports requiring moderate static and high dynamic effort.13 These patients should also be cautioned to report new symptoms, have a repeat echocardiogram six months after the initial visit to document stability, and repeat evaluations yearly thereafter.7
Asymptomatic athletes with severe AI should be restricted from competition and training and followed closely.13 They should have a repeat echocardiogram three months after the initial visit and every six to 12 months subsequently. Asymptomatic athletes with moderate to severe AI and LV dysfunction or marked dilatation due to the AI should undergo valve replacement.7 LV dysfunction is defined as an ejection fraction (LVEF) of <50%.7 Marked enlargement is defined as a LV end diastolic volume >75 mm or and end systolic volume >55.7 Women with AI develop symptoms with less severe LV dysfunction and enlargement than men7 suggesting that smaller individuals may require valve replacement at smaller ventricular volumes. Aortic valve replacement should be strongly considered if there is progressive LV dilation and dysfunction in asymptomatic patients even if the LV does not achieve the above parameters. A LVEF of 50% already represents considerable LV dysfunction in AI patients because the normal ventricular response to AI is to increase the LVEF above the normal 55 to 65%. Also, once the LV is markedly dilated there is the possibility that the LV has been permanently altered and will not return to normal function.
Athletes with severe AI who are symptomatic should undergo AVR. The timing of the AVR can be varied depending on the effort level required to produce symptoms as well as LV function and dimensions.
It is generally recommended that patients with moderate to severe AI and systolic hypertension should be treated with afterload reducing agents such as hydralazine, nifedipine, or angiotensin converting enzyme (ACE) inhibitors to achieve a normal systolic pressure. There is no conclusive evidence that treating normotensive patients with AI is beneficial. Nevertheless, we routinely place patients with moderate to severe AI on ACE inhibitors in the hope of delaying the development of LV dysfunction.
Aortic Valve Replacement in Athletes
The management of athletes after valvular replacement was discussed in the 26th Bethesda Conference.13 In general athletes with normal LV function after aortic valve replacement can participate in low intensity sports with selected athletes participating in moderate intensity static and dynamic sports. Athletes taking anticoagulants should not engage in sports with any risk of bodily contact. These recommendations13 reflect concern about the aortic valve replacement techniques commonly available at that time. Until recently nearly all aortic valve replacements were performed using a porcine heterograph, a cadaveric homograph, or a mechanical prosthesis. The mechanical prostheses required life-long anticoagulation and had an effective valve area of only 1.2 to 3.2 cm2 .16 Both the hetero and homographs required anticoagulation for only three months unless there were other factors predisposing to systemic embolization. Unfortunately, the techniques to preserve these bioprostheses affected their durability and 30% of heterographs and 10-20% of homographs had to be replaced in 10-20 years.16 Bioprosthesis failures were most frequent in patients under age 40 years.16
In 1967 Ross described an autograft approach to aortic valve replacement in which the normal pulmonic valve was used to replace the diseased aortic valve. There was a fairly high early mortality rate to the operation of 7.4% over the first 24 years of its use.17 Ross attributed this to the steep learning curve required for the operation.17 In 1976 the procedure was altered to using the pulmonic valve with the pulmonic trunk in the replacement. This advancement eliminated many of the technical problems inherent in the earlier technique and helped reduce the current mortality rate to <1%.17 The Ross procedure has multiple advantages over other aortic valve replacement techniques. The tissue used is viable because it had not been subjected to sterilization and preservation procedures required for hetero and homographs. This viability means that the replacement should last indefinitely and the new aortic root can actually enlarge with somatic growth of the child.18 As with heterografts and homografts, long-term anticoagulation is not required and the hemodynamic performance of the autograft is equal or superior to all other replacements.17 These advantages have lead many surgeons to conclude that the Ross procedure is the treatment of choice in otherwise healthy subjects with more than a 20-year life expectancy.17 The procedure is especially attractive in athletes. Several high-profile athletes have competed successfully after a Ross replacement including Jesse Sapolo, the center of the San Francisco 49ers American football team.19
There are limitations to this operation. It is not indicated for Marfan syndrome patients or other patients with connective tissue disorders since the same process could affect the pulmonic valve in the aortic position. The operation is complicated and quite often long since it is really a "double valve procedure for a single valve disease"17 and in addition requires reimplantation of the coronary arteries into the autograft. Finally it has not been widely used and few surgeons have extensive experience with the technique. It is not clear that the excellent published mortality results will be replicated by less experienced surgeons. Nevertheless, if performed by an experienced operating team, the Ross procedure is probably the aortic valve replacement of choice for children, physiologically young adults, and athletes.
Mitral Stenosis (MS)
Mitral stenosis (MS) is almost always a consequence of rheumatic fever. Severe MS is rarely seen in competitive athletes. The increase in heart rate with exercise decreases the ventricular diastolic filling time, increasing left atrial, pulmonary capillary wedge, and pulmonary artery pressures. This produces exercise dyspnea and rarely exercise-induced pulmonary edema.
Once MS is suspected the evaluation of severity is primarily based on symptoms and Doppler echocardio-graphic results. Doppler echocardiography can accurately estimate mitral valve area in isolated MS and can also estimate pulmonary artery systolic pressure from the velocity of the tricuspid regurgitant jet. The same technique can be used with exercise to determine changes in pulmonary artery pressure with exertion. The echocardio-graphic study is also used to evaluate the approach to operative intervention. Catheter valvotomy using a venous approach across the atrial septum is often possible if the mitral leaflets are pliable and have minimal subvalvular commissural fusion.7 A mitral valve that appears favorable to percutaneous valvotomy generally permits a more aggressive approach in patients with Doppler evidence of important MS and mild symptoms.
The normal mitral valve area is 4 to 5 cm2 . A reduction to 2.5 cm2 is required for symptoms.7 MS is generally classified as follows13 :
|
Valve |
Pulmonary Arterial | |
|
Mild |
>1.5 |
<35 |
|
Moderate |
1.1-1.4 |
<50 |
|
Severe |
<1.1 |
>50 |
The Bethesda Conference recommends that athletes in normal sinus rhythm with mild MS and no symptoms can participate in all sports.13 Athletes with mild MS and atrial fibrillation or with moderate MS can participate in moderate static and dynamic sports as long as their exercise pulmonary systolic pressure remains below 50 mm Hg. If the pulmonary pressure exceeds 50, these athletes should be restricted to moderate static and low dynamic sports. Patients with moderate or severe MS plus symptoms on moderate exertion should be considered for percutaneous valvotomy if they have suitable anatomy or open valve repair or replacement if their anatomy appears unfavorable for a percutaneous approach.7 Athletes with mild MS and symptoms appearing with vigorous exertion could also be considered for percutaneous valve repair depending on the clinical circumstances. There is no evidence that this will improve their long-term prognosis. It is also possible that percutaneous valvotomy will produce significant MR and make a minimally symptomatic patient more symptomatic.
Chronic Mitral Regurgitation (MR)
In contrast to MS, the common etiologies of chronic MR are multiple and include mitral valve prolapse, healed endocarditis, rheumatic heart disease, Marfan syndrome, and ischemic papillary muscle dysfunction. The LV adapts to chronic MR by increasing its end diastolic volume, but sustained volume overload in severe MR eventually leads to LV systolic dysfunction. The LV afterload in chronic MR is reduced because the LV can "unload" into the relatively low resistance left atrium. This reduced afterload can mask LV dysfunction because the LV ejection fraction may be near normal. In chronic MR, however, the "normal" LV ejection fraction (LVEF) should be in excess of 60%. Mitral valve repair or replacement removes this low pressure escape for LV ejection and may unmask a dysfunctional left ventricle. Survival after mitral valve repair is reduced in patients whose preoperative LVEF is <60%.7
The evaluation of patients with MR includes a history, a physical examination, an ECG, a Doppler echocardio-gram, and a stress test. The history and exercise test should attempt to elicit symptoms of early heart failure since there is consensus that patients with symptoms should proceed to corrective surgery. Doppler echocardiography study is useful in defining LV dimensions and performance, left atrial size, pulmonary systolic pressure, and the severity of the MR. The Doppler echocardiographic study alone is not sufficient to determine the MR severity since the regurgitant jet can be missed and the interpretation is somewhat subjective. Consequently, the echo results should be correlated with other findings. An exercise echocardiographic study may be especially useful in athletes with symptoms and mild to moderate MR at rest. The increased heart rate during exercise increases the frequency of regurgitation and decreases LV diastolic filling time. Both factors may increase exercise pulmonary pressure and account for the symptoms.
Symptomatic athletes with moderate or severe MR should undergo corrective surgery. The timing of the operation can vary depending on the severity of the symptoms and cardiac dysfunction, but there is little benefit in waiting once symptoms have appeared and can be unequivocally attributed to the MR. Athletes with normal sinus rhythm and normal LV function may participate in all sports.13 They should have a repeat echo in six months to document stability of the MR and then every one to two years thereafter. Asymptomatic athletes with normal LV function and mild LV enlargement can participate in moderate static and moderate dynamic activities. Selected athletes with these characteristics can participate in all sports. All patients with mild LV enlargement should be echoed in three months to establish a stable clinical course and then yearly thereafter.
Mitral valve repair is the procedure of choice since it avoids long-term anticoagulation and preserves the mitral valve apparatus. Preserving the papillary muscles and chordal structures helps preserve LV function.7 The next best choice is valve replacement preserving the valve apparatus.
Athletes with LV dysfunction or significant LV enlargement should proceed to corrective surgery. The standard criteria for LV function and surgical repair are an LVEF <60% or a LV end systolic diameter >45mm.7 Nevertheless, athletes with progressive increases in their LV dimensions or decreases in LVEF should also be referred for surgery. Many centers recommend mitral repair for severe MR even in asymptomatic patients without LV changes if there is a high chance the valve can be repaired.20 Similarly, some centers strongly consider mitral valve surgery if atrial fibrillation has occurred even transiently.7 The appearance of atrial fibrillation indicates left atrial dysfunction. Atrial fibrillation may also become permanent if the left atrium continues to face a volume and pressure overload. Chronic atrial fibrillation requires long-term anticoagulation thereby eliminating one of the benefits of valvular repair.
The decision to intervene in severe MR with no or minimal symptoms depends greatly on the skill in valve repair of the surgeon. Valve repair has many benefits over replacement, but failure of the repair almost always leads to replacement. Consequently, the ability of available surgeons influences the decision when to proceed to surgery.
There is only theoretical support for the use of afterload reducing agents in normotensive patients with moderate to severe MR. Despite this we routinely recommend ACE inhibitors to such patients in the hope of preserving normal LV function until corrective surgery.
Exercise After Mitral Valve Surgery
Athletes with mitral valve replacements with normal ventricular function who are not taking anticoagulant medications can participate in moderate dynamic and static sports.13 Athletes on anticoagulant medications should avoid sports with a high risk of bodily collision.13 Athletes who have undergone mitral valve repair can participate in all competitive sports if they have no or minimal MR and normal LV function. Since many of the young athletes who require mitral repair have mitral valve prolapse and since bodily collision can rupture elongated chordae tendinae, we prohibit contact sports in mitral valve prolapse patients who have undergone valvular repair.
Mitral Valve Prolapse (MVP)
Mitral valve prolapse (MVP) is the most common cause of significant MR in the United States and affects approximately 4% to 6% of the population.7 MVP has also been one of the most frequently over-diagnosed cardiac conditions although this is changing with the use of stricter diagnostic echocardiographic criteria. The prognosis of MVP is generally benign. It is a rare cause of sudden cardiac death in the general population and responsible for only 1% of exercise-related cardiac deaths among high school and college athletes.3 Atypical chest discomfort is a common complaint in individuals eventually diagnosed with mitral valve prolapse, but rarely has important sequelae. Palpitations from premature atrial or ventricular beats are also frequent in MVP patients. The important cardiac complications associated with MVP include cardiac arrhythmia, syncope, and sudden death; endocarditis; and significant MR usually produced by chordal rupture. Neurological events can also occur in MVP patients probably from cardiac emboli.21, 22 The serious cardiac complications are more frequent in patients with more extensive valvular pathology including redundant and thickened valve leaflets, a systolic murmur, and left atrial enlargement.23, 24
MVP is usually detected during a routine physical examination or in a patient undergoing echocardiography as part of an evaluation for chest pain or palpitations. The characteristic auscultatory findings include a midsystolic click and/or a late systolic murmur. Classically the click and murmur are variable with position, respiration, and other maneuvers. This variability often leads to the diagnosis. Maneuvers that reduce ventricular volume such as standing move the click and the start of the murmur earlier in systole whereas maneuvers that increase ventricular volume delay the onset of the click and murmur. Since MVP is common in Marfan syndrome, the physical examination of patients with MVP should include a search for stigmata of this condition. There is no requirement for echocardiographic confirmation of MVP if the findings are classic, the murmur does not indicate severe regurgitation, and the patient is asymptomatic. Some authorities recommend echocardiography in all subjects to detect valvular abnormalities associated with a more serious prognosis.7 If echocardiography is performed at baseline, patients with moderate MR, left atrial enlargement, and thick or redundant leaflets should have the study repeated at one to two year intervals. Patients without evidence of serious valvular pathology should be restudied approximately every five years.
The management of athletes with MVP depends on the severity of the MR, the presence of symptoms, and the pathological appearance of the valve. Athletes with moderate or severe MR should be evaluated and followed as discussed in the section on MR. According to the Bethesda Conference,25 the usual athlete with MVP can participate in all competitive sports. Athletes with MVP and arrhythmogenic syncope, a family history of sudden cardiac death associated with MVP, repetitive supraventricular or ventricular arrhythmia, or prior embolic events should be restricted to low intensity dynamic and static sports.25 Athletes with supraventricular arrhythmia can usually be well-managed with low- dose beta adrenergic blockade or with a strong chronotropic calcium channel blocker such as verapamil. Athletes with nonthreatening ventricular arrhythmia can similarly be managed with beta blockade. Such athletes should undergo exercise stress testing and should be cautioned to report any change in symptoms. The general recommendation is that patients with MVP and prior neurological events should be placed on aspirin therapy.7 Although the risk of a stroke is extremely low, we recommend that all patients with MVP use at least an 80 mg aspirin daily. The cost and risk of aspirin therapy is low, and the potential benefit is great.
Tricuspid Regurgitation (TR) and Stenosis (TS)
Trivial tricuspid regurgitation (TR) may be detected by Doppler echocardiography in up to 76% of athletes and is not associated with any valvular pathology.12 The most frequent cause of important TR among young adults in most medical centers is valvular damage secondary to acute endocarditis associated with intravenous drug use.7 Congenital valvular abnormalities is the most frequent cause of TR in children and is often produced by Ebstein's anomaly of the tricuspid valve. TR can also be caused by rheumatic heart disease and by right ventricular dilatation from volume or pressure overload. There is no evidence that isolated TR increases the risk of exercise and the effect of exercise training on the prognosis in TR has not been examined to our knowledge. Nevertheless, athletes with isolated TR and without markedly elevated right atrial pressures determined by neck vein examination can participate in all sports.
Tricuspid stenosis (TS) is generally produced by rheumatic fever and is almost always associated with MS. Recommendations for sports participation in athletes with TR and MS should be based on the severity of the MS.
Pulmonic Stenosis (PS) and Pulmonic Regurgitation (PR)
Valvular pulmonic stenosis (PS) and pulmonic regurgitation (PR) are almost always congenital in origin. Children and adolescents with PS are often asymptomatic even with severe obstruction.7 Adults and some children may have symptoms of exertional dyspnea, syncope, and presyncope although exercise-related sudden death is rare. Doppler echocardiography is used to determine the severity of PS. A peak pulmonary valve gradient <40 mm Hg implies mild PS. Peak values of 40 to 70 and >70 mm Hg indicate moderate and severe PS respectively.26
Athletes with peak systolic gradient <50 and normal right ventricular function can participate in all sports. 26 They should be re-evaluated annually and undergo repeat echocardiographic studies every two to three years. Athletes with gradients >50 should be referred for valvuloplasty.
PR is usually due to congenital idiopathic dilation of the pulmonary artery.7 Symptoms or exercise limitation are unusual from PR alone, although a rare patient may develop right ventricular enlargement and require pulmonic valve replacement. No exercise restrictions are placed on asymptomatic athletes with PR.
Other Considerations
Endocarditis Prophylaxis: Subacute bacterial endocarditis is most frequent in valvular lesions where high velocity blood flow enters a lower pressure chamber. High velocity flow into a lower pressure chamber disrupts laminar blood flow and creates areas of platelet, fibrin, and bacterial deposition. This physiologic profile applies to all of the valvular lesions discussed above with the exception of pure MS. Antibiotic endocarditis prophylaxis should be prescribed for all athletes with valvular heart disease. The only exception is in athletes with tricuspid or pulmonic regurgitation when a murmur is not detected. Right-sided pressures are lower than left-sided pressures which reduces the risk of bacterial deposition. Furthermore, tricuspid and pulmonary regurgitation detected only by Doppler is common. We provide athletes with the wallet sized instruction cards available in bulk at minimal cost from the Heart Association, 7272 Greenville Avenue, Dallas, TX 75231-4596.
The role of endocarditis prophylaxis in MVP has also been controversial. Antibiotic prophylaxis is generally recommended only if a murmur is present.7 In patients with only a midsystolic click, the general recommendation is to use endocarditis prophylaxis only in the presence of signs of severe valvular pathology as discussed above.7 Our approach is to place all patients with definite MVP on endocarditis prophylaxis before procedures associated with bacteremia. MR is often intermittent in patients with MVP and can be missed on a single examination. Also as many as 33% of patients with MVP, but without MR at rest, can induce MR with exercise.27 The cost and risk of endocarditis prophylaxis in MVP patients is small and the potential benefit, if endocarditis is prevented, great.
Rheumatic Fever Prophylaxis: Guidelines for the prevention of rheumatic fever have been published.28 Rheumatic fever prophylaxis is extremely important in patients who have had rheumatic carditis. Recurrent episodes of rheumatic carditis exacerbate the valvular injury, increase the severity of the valvular lesion and may hasten the need for valvular surgery. Patients with prior rheumatic fever who develop streptococcal pharyngitis are at high risk for recurrent rheumatic fever, and the infection need not be symptomatic to restart the carditis. Also, rheumatic fever can occur after a streptococcal infection even when the infection is treated promptly and correctly. Individuals exposed to groups, such as athletes on athletic teams and their coaches, are more likely to acquire a streptococcal infection. For all of these reasons, any athlete or coach with documented rheumatic valvular disease should receive antibiotic prophylaxis until at least age 40 and probably for life if the athlete continues to be exposed to groups of athletes.
The best prophylactic treatment is 1.2 million units of benzathine penicillin G intramuscularly every three weeks.28 Oral treatment with 250 mg of penicillin V twice a day is acceptable, but much less dependable as prophylaxis because of reduced compliance. Patients allergic to penicillin can be treated with sulfadiazine 1 gm daily or erythromycin 250 mg twice daily. Erythromycin is usually a better choice in athletes because of the photosensitivity that can occur with sulfur containing compounds.
Summary
Knowledge of the evaluation and management of active individuals with valvular heart disease is a critical component of sports cardiology. Valvular aortic stenosis continues to account for approximately 4% of exercise-related sudden deaths among young athletes. The presence of a cardiac murmur or the possibility of cardiac symptoms among young athletes is a frequent reason for cardiac referral. The most common cause of cardiac murmurs in athletes is a flow murmur across the pulmonic valve related to the cardiovascular adaptations that occur with exercise training. In adults, physiologic flow murmurs are often related to aortic sclerosis, but this condition may not be as benign as flow murmurs in children because aortic sclerosis is accompanied by other risk factors for atherosclerosis such as hyperlipidemia.
Severe AS may present with exercise-induced syncope, angina, heart failure, and rarely sudden death. Athletes with severe AS should be restricted from competition and encouraged to undergo aortic valve replacement. Active subjects with moderate to severe AI require careful follow-up and periodic echocardiograms to detect early signs of heart failure or progressive LV dilatation. Surgical repair should be performed with the onset of symptoms, marked cardiac enlargement, or progressive LV dilatation. Athletes with moderate or severe MR should be followed in a fashion similar to that for AI and repair performed for symptoms or progressive LV dilatation. Active individuals with MS should undergo mitral valvuloplasty with the onset of symptoms. All athletes with valvular heart disease should receive antibiotic prophylaxis for endocarditis. Athletes whose valvular disease is secondary to rheumatic fever should receive streptococcal infection prophylaxis until age 40 or for as long as they are exposed to possible infection.
Personal Perspective
Athletes and active people referred for evaluation of valvular abnormalities generally fall into three groups. Those in whom the examination and additional studies reveal a physiological flow murmur; those with severe valvular disease or symptoms who require valve surgery; and those in whom the decision to proceed with repair or activity restriction is not clear. We find the most useful approach with such patients is to perform a careful history specifically eliciting information about competitive performance changes and subtle exercise intolerance. It is useful in this situation to have had some competitive athletic experience to understand symptoms that are a normal part of athletics. It is also extremely useful in valvular cases to retrieve old echocardiograms and to chart cardiac dimensions over time since this often reveals progressive chamber enlargement. It most instances this indicates that surgery will be inevitable and that the only issue is when. When there is still doubt with the patient or the physician as to how or when to proceed, one rarely makes a mistake by waiting briefly and following the patient closely. Even in severe AS the incidence of unheralded sudden death is rare although we do restrict athletic participation if severe AS is possible. Oftentimes a brief period of delay helps the patient, and even the physician, become more comfortable with the decision. On the other hand, if there is no doubt that a valve lesion is severe and will require surgery, we encourage the athlete to proceed with repair promptly to allow resumption of as active a lifestyle as possible.
Equally difficult is the decision as to whether the patient should have a valve repair or replacement and with which prosthesis or technique. This decision is based on the patient's wishes, the need for long-term anticoagulation, and most importantly, on the skill of the surgeon. The physician should never hesitate to refer patients to other institutions when more complex surgery or newer techniques, such as the Ross Procedure, are most appropriate and yet not performed frequently locally.
Acknowledgements
The author thanks Drs. Daniel Fram and Francis Kiernan who critiqued drafts of the manuscript.
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Paul D. Thompson, M.D., Director of Preventive Cardiology, Hartford Hospital, Hartford. This article is reproduced with permission from The Textbook of Exercise and Sports Cardiology to be published by McGraw-Hill and edited by Dr. Thompson.