Valvular heart disease refers to all inherited and acquired abnormalities impairing the function of one or more of the four cardiac valves. Pathology may be of the valve leaflets themselves, of the subvalvular apparatus or of the annulus or other surrounding structures that influences valve function. This paper examines the most common valve lesions, with specific reference to a military population; it focuses on detection and initial management of valve disease in a young adult population and specifically describes how the diagnosis and treatment of valve disease impacts military medical grading.
- Occupational cardiology
- Military medicine
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In the young military population mild congenital valve disease, missed at recruit entry and exposed by strenuous exertion, is over-represented.
Bicuspid aortic valve (prevalence 1%) is by far the most common congenital defect and confers a risk of early aortic regurgitation, aortic stenosis and endocarditis.
Valve intervention is based on integrated assessment of symptoms, left ventricular function, haemodynamic complications such as pulmonary hypertension and implications of anticoagulation.
Intervention should be targeted at the time when the risk of non-intervention exceeds that of intervention.
Decisions should be made by a multidisciplinary team. They should include the views of the serviceman and input from a military cardiologist and occupational physician.
Valvular heart disease is important to the military physician because, although it is infrequent, it typically follows a progressive course and has serious complications including heart failure, arrhythmia and thromboembolism which are likely to have a negative impact on the serviceman's health and combat effectiveness. Valve disease frequently requires intervention and the intervention itself, or the associated anticoagulation, will restrict military employment and deployability. Service physicians have the opportunity to detect valve disease before it leads to life-threatening or operation-threatening complications. Valve lesions may be diagnosed on application to join the services at recruit medical, incidentally during routine age/career-related medicals or with complications of the valve disease itself. In view of the health and military cost of missing the diagnosis, it is critical that all service physicians are equipped to ascertain the features, which reveal a valve lesion and know the appropriate initial management and the occupational restrictions that must be observed.
A 35-year-old sergeant (chef) presents to his unit medical officer for a routine, age-related medical. When questioned about symptoms, he describes a reduction in his performance on mandatory fitness testing (1.5 mile unloaded run) despite efforts to improve his aerobic fitness. On further questioning he confirms that he is more short of breath on exertion. He has not noticed any impact on his duties as a chef.
He denies any chest pain, palpitations, syncope, presyncope, cough or wheeze at rest or on exertion. He reports no sweats, fevers or recent febrile illness. He has no history of exposure to industrial chemicals or asbestos. He has no pets and has never smoked. He has no personal or family history of cardiovascular disease. There is no history of sudden or unexplained death in his family. He has always been in the top 20% for fitness in his unit. He completed a local half marathon in 1 hr 42 min at age 29 years. He continues to exercise routinely for more than 45 min, at least four times per week. His body mass index (BMI) is 23.
The medical officer asks about respiratory, gastrointestinal and rheumatological complaints, finding nothing of concern. The sergeant has no past medical history of note. He has no allergies or hay fever and takes no regular medication, supplements or recreational drugs. He drinks 12 units of alcohol per week. He adds that he has recently passed a compulsory drug test. The medical officer feels that the exertional shortness of breath, in the absence of cough or wheeze, is most likely to be cardiovascular in origin, however respiratory causes and anaemia are plausible differentials.
History taking for valve disease
The history must target symptoms objectively. Humans are adept at modifying their activity to match their limitations and frequently under-report symptoms. It is therefore important to ask about a reduction in exercise ability even without overt symptoms. Objective measures of exercise tolerance (running distances and times) and their rate of change are very useful.
Shortness of breath, syncope or presyncope, palpitations and chest pain must be specifically assessed and are fundamental to prognosis; in severe aortic stenosis (AS), for example, the mortality is 50% at 2 years after the onset of overt symptoms.1
It is also essential to explore potential aetiology such as rheumatic fever, hypertension or infective endocarditis, and comorbidity. Comorbid illness such as renal impairment, lung disease or type 2 diabetes, worsens prognosis and will increase the risk of valve intervention.
Rheumatic heart disease is rare in industrially developed nations but is a significant burden in the industrially underdeveloped world. The military physician is still likely to encounter patients and/or servicemen and women who grew up in a rheumatic fever endemic region.
Family history should include questioning for sudden or unexplained death, unexplained heart failure and valvular, structural or ischaemic heart disease.
On physical examination there is visible pulsation of the carotid arteries (Corrigan's sign). The radial pulse is 74 and regular. The pulse is collapsing on elevation of the arm. Right brachial BP is 143/63. There is no conjunctival pallor or jaundice. The jugular venous pressure (JVP) is not elevated. Central pulses are of increased volume. The apex beat is dynamic but undisplaced. On auscultation the heart sounds are normal. There is an early diastolic murmur at the left sternal edge and an ejection systolic murmur radiating to the carotids. The lung fields are clear. The respiratory rate is 14 breaths per minute. Oxygen saturations by pulse oximetry are 98% on room air. There is no peripheral oedema and no peripheral stigmata of embolic/vasculitic disease. The urine dip is negative for blood.
Examination in valvular heart disease
Although the full characterisation of valve disease requires cardiac ultrasound (echocardiography), the acumen of the physician is essential to recognise the symptoms and then to confirm the signs of potential valve disease with targeted examination.
The following specific features of valve disease should be assessed:
AS: Narrow pulse pressure (if not in the 50% of the elderly population who have isolated systolic hypertension) and slow rising pulse. A quiet second heart sound (S2) is specific but not sensitive for severe AS. A long ejection systolic murmur is the audible correlate of a slow rising pulse and indicates a severe lesion. Increased afterload may lead initially to a pressure-loaded apex beat and, in advanced disease, to signs of heart failure. The amplitude of an ejection systolic murmur is not reliably correlated to severity.
Aortic regurgitation (AR): Wide pulse pressure, low diastolic pressure and collapsing pulse (technically a collapsing pulse is defined as pulse pressure >diastolic pressure). Diastolic BP in severe AR is <70 mm Hg and may be as low as 30–40 mm Hg. These signs are caused by an increased stroke volume (necessary to compensate for the regurgitant volume) and low resistance to blood rapidly flowing back through the regurgitant valve. This accounts for the rapid increase (systole) and decrease (diastole) in arterial diameter palpated beneath the clinician's fingers—the clinical collapsing pulse. The length of the diastolic murmur is proportional to the severity of the lesion although in severe decompensated AR and acute AR the murmur is short because of high left ventricular (LV) end-diastolic pressure. Because AR leads to an increased stroke volume, a systolic flow murmur (which conducts to the carotids) is the rule, rather than the exception. There may also be the mid-diastolic Austin Flint murmur as a result of functional mitral stenosis (MS) because of the AR jet impinging on the anterior mitral leaflet. An associated third filling sound is also often heard.
Severe, life-threatening AR is marked by a holodiastolic murmur, very low diastolic pressure and signs of left heart failure. While the apex beat is often displaced in chronic AR, it may not be displaced in hyperacute AR, with insufficient time for the ventricle to dilate.
Mitral regurgitation (MR): Atrial arrhythmias, such as atrial fibrillation, are common sequelae of left atrial dilatation. The cardiac apex may be diffuse and laterally displaced. MR causes a pansystolic murmur, which radiates to the axilla. A third heart sound is the result of increased volume of ventricular filling and decreased ventricular compliance. Due to reduced duration of LV ejection, there may be wide splitting of S2 in severe MR (early A2). Other signs of severe MR include a mid-diastolic flow murmur due to increased volume of LV filling and pulmonary congestion.
Mitral valve prolapse (MVP) may cause a ‘crescendo’ late systolic murmur sometimes preceded by a systolic click or a pansystolic murmur as for any other cause of MR.
MS: Atrial arrhythmias, such as atrial fibrillation, are common sequelae of left atrial dilatation. Prolonged pulmonary congestion is believed to release vasoactive factors that account for the flushed-cheek mitral facies. Once established, this sign persists even after correction of the stenosis. The low frequency, mid-diastolic murmur radiates to the axilla. It begins earlier as valve pathology progresses. Severe MS is marked by a long diastolic murmur commencing soon after S2. This reflects the pathologically raised left atrial pressure. The apex is usually undisplaced. If long-standing secondary pulmonary hypertension develops, this leads to right ventricular dilatation and a parasternal heave will be felt. In severe MS pulmonary hypertension may also delay the closure of the pulmonary valve causing similar increased splitting of the second heart sound to that of MR but from a distinct mechanism (late P2 rather than early A2).
The medical officer obtains an urgent 12-lead ECG. He notes that the patient is in sinus rhythm. The ECG has a normal axis and no conduction abnormality. There are no pathological Q-waves, ST or T wave abnormalities to indicate ischaemic heart disease. He observes LV hypertrophy by voltage criteria. He is careful to exclude a prolonged PR interval.
The ECG in valve disease
The ECG can detect atrial arrhythmia as a complication of valve disease especially in MS and less often in MR. Large voltages may occur in AS and AR, but can be normal in a young, slim, athletic population. It can also reveal atrial enlargement. A prolonged PR interval or higher grade atrioventricular block in endocarditis is a sign of abscess but may also occur in AS with calcific involvement of the conduction tissues. The ECG can occasionally be useful for aetiology such as evidence of previous myocardial infarction.
In view of the history, examination findings and ECG the medical officer considers whether there is aortic valve pathology or hypertrophic cardiomyopathy with LV outflow tract obstruction. An outpatient CXR and echocardiogram is arranged at the local hospital. A blood test is taken during the medical to exclude anaemia and inflammation and to check kidney function. The medical officer ascertains that the sergeant is neither a military diver nor aircrew, but is aware from JSP 950 6-7-5 annex C that Royal Navy and Royal Air Force guidance is applicable to these specialist occupations.2 ,3 Pending investigation, the sergeant is temporarily medically downgraded and declared ‘unfit strenuous exercise’.4 A plan is made to refer to a cardiologist with the result of the echocardiogram.
Echocardiography in heart valve disease
Echocardiography is the key investigation for heart valve disease.5 It confirms the diagnosis, assesses severity and determines the left-sided and right-sided ventricular response to the valve defect. It is also essential in determining aetiology (eg, endocarditis or structural heart disease) and complications such as LV dilatation or reduced systolic function. Taken together, these findings inform an accurate estimate of prognosis.
The assessment of stenotic lesions requires the integration of appearance (eg, calcification and mobility), valve area estimation and flow-dependent measures such as mean pressure drop (mm Hg) and maximal velocity (m/s). The latter, although dependent on LV function, provides important prognostic information.
Regurgitation assessment combines visual assessment, such as the appearance of colour Doppler jet, with objective numerical parameters such as vena contracta width (the width of regurgitant jet at its narrowest point, mm) and effective regurgitant orifice area (mm2).6–8 Flow reversal at the arch is useful in AR especially when the jet at the valve is eccentric as is common with bicuspid valves.
Echocardiography measurements should be indexed to body surface area (m2). This is particularly important for small adults. Indexing to body size should be discontinued in severely obese patients (BMI >35).
Echocardiography is highly dependent on user expertise and should be performed by experienced operators in high volume centres. It is very important that a diagnosis of ‘severe’ valve disease is not missed or wrongly given in mild or moderate disease in view of the central importance of this label as a criterion for surgical intervention.
Transthoracic echocardiogram report:
LV is at the upper limit of the normal range (left ventricular EDD=5.9 cm).
LV systolic function is normal (>55%) with a left ventricular ejection fraction (LVEF) of 63%.
Aortic valve is bicuspid (fusion of right coronary and non-coronary cusps) with associated severe AR.
Pressure half time of the regurgitant jet is 235 ms (<250 ms is severe).
Regurgitant fraction is 53% (>50% is severe).
Vena contracta width is 0.7 cm (>0.6 cm is severe).
Diastolic flow reversal in the distal aortic arch (an echo sign of severe AR).
No evidence of infective endocarditis (transthoracic echo cannot reliably exclude infective endocarditis and alternative imaging should be employed if clinically indicated).
Aortic root and ascending aortic dimensions are normal with no coarctation.
Right heart is normal in size and function and there is no evidence of pulmonary hypertension or other valve disease.
Other investigations in heart valve disease
Exercise testing can reveal occult symptoms not present at rest and can also assist with decisions regarding limitation of physical activity.
Exercise echocardiography requires specific expertise. It can be an aid in identifying cardiac causes of shortness of breath by uncovering exertional alterations in valve gradients, degree of regurgitation and pulmonary pressures. It can be diagnostic in transient ischaemic MR and can supply indications for surgical intervention in AS (by demonstrating mean valve gradient >40 mm Hg) and MR (by revealing severe regurgitation not present at rest or systolic pulmonary pressure >60 mm Hg).5
Other cardiac imaging such as cardiac MRI or CT can contribute to assessment of valve lesion severity. MRI is particularly useful for assessing regurgitant valves for which it is the gold standard assessment for ventricular volumes and systolic function and aortic dimensions. Cardiac CT is helpful for assessing AS and aortic dimensions. CT coronary angiography provides high negative predictive value for normal coronary arteries in low-risk patients. CT confers an additional lifetime risk of cancer due to radiation exposure and can precipitate renal injury if contrast is used. Cardiac MRI is contraindicated with implantable cardiac defibrillators and older pacemaker systems, has limited availability and is expensive; however it is safe, reliable and sensitive. Serial assessment (eg, of aortic root diameter in moderate AR) should be conducted using the same imaging modality.
Assessment of the coronary arteries is indicated when surgery is anticipated in all men over 40 years, all postmenopausal women and all patients with one or more cardiovascular risk factors.5 Cardiac catheterisation pressure studies are no longer routine and are limited to instances when other non-invasive modalities are inconclusive or contradictory.
The basis for intervention in valve disease is determined by the patient's symptoms, disease severity, the adaptation of the LV and the resulting prognosis. Decision-making is best performed by an experienced and expert multidisciplinary team (comprising: cardiothoracic surgeons, cardiologist imaging specialists and cardiac anaesthetists) for all patients.5 In the military context an occupational physician is an essential addition to this team.9 ,10
Bicuspid aortic valve
Bicuspid aortic valve (BAV) has 1% prevalence in the population with a 2–3:1 male/female preponderance; among male military conscripts in Italy the prevalence is reported as 0.8%.11 It is an autosomal dominant condition with incomplete penetrance and cases may also be sporadic. It occurs most commonly as fusion of two cusps in a morphologically tricuspid valve but can also occur as a true, symmetrical, bicuspid valve. BAVs are more prone to developing stenosis, regurgitation and infective endocarditis than normal native valves. A third of individuals will develop complications.12 BAV is associated with coarctation and aortic root dilatation which has implications for the intervention that is offered (eg, aortic root and valve replacement) and the physical limitations that are placed on an individual (Table 1).13
Transthoracic echocardiography has a high sensitivity for detecting BAV (92%) whereas transoesophageal echo detects nearly 100% of lesions.14 Echo can also characterise the function and morphology of the valve, detect calcification and assess the aortic root, ascending aorta arch and descending thoracic aorta (for coarctation).
AR has been estimated to have a prevalence of 0.5%15 and is caused by primary disease of the valve leaflets, by aortic root dilatation or by a combination of both. In the developed world, BAV and degenerative aortic root disease are the leading causes, whereas in the developing world, rheumatic heart disease remains the principal aetiology. Acute severe AR usually presents as an emergency with haemodynamic instability, which is most commonly caused by infective endocarditis or aortic dissection. From a military perspective, it is important to note that it can also occur secondary to traumatic injury. Symptoms of chronic AR include breathlessness, impaired exercise tolerance and fatigue; after development of symptoms, chronic severe AR has an annual mortality of 10–20%.13
Surgical valve replacement is the most common intervention for severe AR, though the use of aortic valve repair for selected patients in some specialist centres is increasing. The European Society of Cardiology (ESC) guidelines present indications for surgical intervention in all cases of valve disease using Classes of Recommendations (Table 2) consistent with those also used by the American College of Cardiology (ACC) and American Heart Association (AHA) and common to all their guidelines. For AR: surgery is indicated (class I) in symptomatic severe AR; in asymptomatic severe AR with LV dysfunction (EF ≤50%) and in patients undergoing cardiac surgery for another indication (coronary artery bypass grafting (CABG), other valve or aorta). Surgery should be considered (class IIa) in asymptomatic severe AR with EF >50% but with severe LV dilatation (LVEDD >70 mm, left ventricular end systolic diameter (LVESD) >50 mm or LVESD >25 mm/m2).5 ,16
Surgical intervention for aortic dilatation is based on comorbidity, which determines aortic dimension thresholds for operation: surgery is indicated (class I) in Marfan syndrome and aortic root ≥50 mm; surgery should be considered (class IIa) in patients with Marfan syndrome and aortic root ≥45 mm in the presence of other risk factors (family history of dissection, ≥2 mm/year dilatation, severe AR or MR) or desire for pregnancy; surgery should be considered (class IIa) in patients with BAV and aortic root ≥50 mm in the presence of other risk factors (family history of dissection, ≥2 mm/year dilatation, hypertension or coarctation); surgery should be considered (class IIa) in all other patients with aortic root ≥55 mm.5
In Marfan syndrome or in patients with an enlarged aorta on echocardiography, CT or MRI is recommended for detailed evaluation and serial imaging of the aorta. ACE inhibitors or angiotensin receptor blockers (ARBs) are indicated in severe heart failure before surgery or to manage hypertension and heart failure where surgery is contraindicated. There is no evidence that these drugs can delay surgery in asymptomatic individuals. β-blockers and ARBs reduce the rate of aortic root dilatation in Marfan syndrome.
The prevalence of AS is 0.4% 15 and the leading cause of AS is age-related calcification, its prevalence increasing to 2–7% if over 65 years. 17 The degeneration and calcification process of ageing is accelerated in the presence of BAV. In the West, congenital AS has overtaken rheumatic fever as the second most common aetiology.
AS is defined by valve area. Severe AS: valve area <1 cm2 (or <0.6 cm/m2 in small adults). Echocardiographic estimation of valve area by use of the continuity principle (Left ventricular outflow tract (LVOT) areameasured×LVOT velocitymeasured=aortic areacalculated×aortic velocitymeasured) is a flow-independent measure. This means that it is unaffected by LV function and is theoretically superior to measures of aortic valve flow velocity. However, in practice there is considerable interoperator variability of continuity measurements. Doppler measurements of aortic valve flow velocity are, by contrast, much more reproducible and so continue to provide an important element of the integrative ultrasound assessment. In cases where valve gradients are thought to have been underestimated secondary to poor LV function, a low-dose dobutamine infusion may be used to stimulate contraction and assess the valve gradient. If the mean gradient exceeds 40mmHg the stenosis is severe.
Symptoms include exertional chest pain, presyncope, syncope and shortness of breath. Exercise testing can be very useful to expose symptoms and objectively measure external work (as metabolic equivalents). Severe AS can remain asymptomatic for many years. This is of key prognostic significance as the annual mortality of <1% in asymptomatic patients rises precipitously to 10% in the first 6 months following symptom onset. Five-year survival ranges from 15–50%. Surgical intervention is therefore targeted to be as soon as possible after the development of severe, symptomatic AS or ideally just before by revealing latent symptoms on treadmill or bicycle exercise or by detecting a reduction in exercise capacity on questioning.
Surgical intervention is indicated (class I) for severe AS causing symptoms; for severe AS where other cardiac surgery is taking place; for asymptomatic severe AS causing LVEF <50% and asymptomatic severe AS with Vmax >5.0 m/s.5
In cases of severe, symptomatic AS in elderly or multiply comorbid patients unsuitable for AV replacement, a radiologically guided transcatheter aortic valve implant (TAVI) is indicated (class I). This decision should be guided by a multidisciplinary ‘heart team’ and must be undertaken at a centre with cardiac surgery (class I).5 One-year survival following TAVI is up to 80%18 ,19 and early 3–5-year data are encouraging. In adults, balloon aortic valvuloplasty has a high complication rate (>10%) and limited life span, with poor results at 1 year post procedure. It may be used as a bridge to surgery/TAVI or for palliation.
Medical treatment is reserved for patients awaiting, or not suitable for, intervention. angiotensin converting enzyme inhibitors (ACEis) improve symptoms and outcome in those not suitable for surgery.12 ACEIs, ARBs, digoxin and diuretics are appropriate for symptoms of heart failure. Statins do not slow the progress of AS, but may be appropriate secondary prevention for associated coronary disease. Nitrates are generally contraindicated, as they reduce preload and may precipitate hypotensive collapse.
The overall prevalence of MR is 1.7%15 and accounts for 31% of valve disease in Europe. It is the second most frequent lesion that requires surgery.17 The surgical treatment recommendations for MR have changed to favour valve repair over valve replacement where possible.5 Surgical repair should be undertaken by specialist surgeons operating in high-volume centres. Primary MR describes cases in which the pathology is of the mitral valve annulus, leaflets or subvalvular apparatus and is distinct from secondary (or ‘functional’) MR, in which LV dilatation or regional wall motion abnormality causes dysfunction of an anatomically intact valve. Acute MR, caused by papillary muscle rupture, infective endocarditis or trauma, is a separate category, with ominous prognosis, that requires immediate surgical intervention. Patients may require intubation and ventilation, inotropes, diuretics and circulatory assistance with an intra-aortic balloon pump to stabilise them for emergency surgery.
As the incidence of rheumatic heart disease has fallen, valve degeneration has become the most prevalent cause of primary MR in developed nations, ahead of rheumatic heart disease and infective endocarditis.17 Rarely, systemic lupus erythematosus, radiation, anorectic serotonin agonists (eg, fenfluramine), cabergoline and MDMA/ecstasy may cause valve degeneration. Rheumatic heart disease is the leading cause of MR in the developing world.
Severe MR may be asymptomatic or associated with breathlessness, impaired exercise tolerance, orthopnoea and fatigue. Complications include atrial arrhythmias caused by left atrial dilatation, which can worsen dyspnoea and confer a high risk of stroke requiring anticoagulation. MR has been implicated in up to 30% of cases of infective endocarditis.20 Five-year mortality in asymptomatic, severe MR is 22%.21
The criteria for surgical intervention are complex and depend on the aetiology, cardiac function and comorbid pathology. Symptoms, age, new-onset atrial fibrillation, LV function, pulmonary hypertension and suitability of valve for repair are all predictors of outcome that can influence the decision to proceed to surgical intervention. This decision should be made by a multidisciplinary ‘heart team’.
The ESC guidelines list the following indications for severe, primary MR surgery: Mitral valve repair is preferred (class I) where the repair is predicted to be durable; surgery is indicated (class I) in patients with symptomatic, severe MR without severe LV dysfunction (LV EF >30% and LVESD <55 mm); surgery is indicated (class I) in asymptomatic, severe MR with LV dysfunction (LV EF <60% and/or LVESD >45 mm (American Heart Association/American College of Cardiology guidelines use a lower threshold cut-off: >40 mm)); surgery should be considered (class IIa) in asymptomatic patients with preserved LV function, high likelihood of durable repair for flail leaflet and LVESD >40 mm.5
Percutaneous, catheter-based interventions are constantly improving. The MitraClip is the currently favoured method and is felt to be relatively safe and well tolerated in patients mainly with functional MR even in poor surgical candidates. It is currently recommended in inoperable or high-risk surgical candidates who have a life expectancy greater than 1 year. The EVEREST study reported a 75% success rate of catheter-based techniques for MR in patients with poor clinical condition,22 but 20% of patients have required reintervention within 1 year in the EVEREST II study.
ACE inhibitors have no role in chronic MR without heart failure. Where heart failure has developed in candidates not suitable for intervention, or where heart failure persists following intervention, they are indicated. In these groups, β-blockers may reduce symptoms and should be considered, along with mineralocorticoid receptor antagonists such as spironolactone.
Secondary (‘functional’) MR
Secondary MR is not primary valve pathology. It results from distortion of the mitral annulus or subvalvular apparatus due to LV enlargement or regional wall motion abnormality. This may be secondary to cardiomyopathy or coronary artery disease and confers a poor prognosis. Functional MR of ischaemic aetiology in particular may be minimal at rest. Exercise echocardiography may be helpful in revealing severe MR on stress, for example by unmasking exercise-induced posterior wall motion abnormality, leading to tethering of the posterolateral papillary muscle and restricting posterior leaflet closure.
Medical management is first line therapy and should be given as directed by heart failure guidelines: ACE inhibitors, β-blockers and mineralocorticoid receptor antagonists. Diuretics should be used for symptomatic relief of fluid overload. Cardiac resynchronisation therapy may provide an immediate improvement through improved coordination of papillary muscles and then longer-term improvement through beneficial reverse remodelling of the LV.
Surgery in this group carries higher perisurgical mortality and has not been proven to extend life expectancy. 23 One randomised study of CABG versus CABG plus mitral valve repair showed a short-term benefit in LV size, ejection fraction and functional class. This study was not powered to provide a mortality comparison and all patients were of moderate MR severity. There is a significant rate of recurrence of MR after valve repair in secondary MR.
Mitral valve prolapse
MVP is diagnosed by imaging prolapse of the mitral leaflet coaptation point 2 mm through the valve plane into the left atrium in the four-chamber view or movement of any part of the valve leaflet over 2 mm into the atrium on other views.
It may be a normal variant or the result of degenerative disease, divided into myxomatous infiltration which are generally genetically predisposed, such as Marfan syndrome and Ehler-Danlos syndrome type IV or fibroelastic deficiency which is a senescent process.
There is no established association between MVP and stroke except where it leads to MR, atrial dilatation and atrial fibrillation (AF),24 However, the risk of infective endocarditis rises fivefold.25 There is no indication for endocarditis prophylaxis, except where there is a history of previous endocarditis.26 MVP does not cause symptoms unless there is associated MR (7% of cases). Where MVP leads to severe MR there is a 30% 10-year incidence of AF and annual 1–2.5% risk of sudden death.
Treatment for MVP is directed only at cases causing severe MR. The arguments in favour of early surgical repair versus watchful waiting are the same as in primary MR.
The prevalence of MS is 0.1%15 and this reduction reflects the decline in rheumatic heart disease in the developed world. The burden in the developing world is much greater. Percutaneous mitral commissurotomy (PMC), a catheter-mounted balloon technique, has revolutionised valve intervention for MS.
MS is defined by a reduction in the cross-sectional area of the mitral valve orifice during diastole below 2 cm2 (normal 4–6 cm2). Symptoms of exertional breathlessness and fatigue do not usually occur until the valve area has reached this threshold and symptoms at rest are rare until <1.5 cm2. Raised left atrial pressures cause left atrial dilatation and blood ‘pooling’. A combination of atrial fibrillation and this thrombogenic substrate results in an 18-fold increase in the risk of stroke.27 Raised left atrial pressure leads to pulmonary congestion causing orthopnoea and paroxysmal nocturnal dyspnoea. Prolonged pulmonary venous hypertension ultimately leads to irreversible pulmonary vascular remodelling and pulmonary hypertension; this, in turn, causes right heart failure.
Investigation is by echocardiography. Valve planimetry (two-dimensional tracing of the maximum valve area), pressure half-time and mean pressure gradient are used to grade severity. Importantly, echo is also used to objectively score the suitability of the valve for PMC, based on calcification, valve leaflet thickening and valve mobility, commissural involvement and subvalvular deformation. It may also reveal other diseased valves (common in rheumatic aetiology) and complications including left atrial thrombus and pulmonary hypertension. Exercise testing may elicit exertional symptoms and exercise echo may expose haemodynamic pathology not present at rest.
In common with many valve lesions, there is a marked worsening in prognosis after symptom onset. Intervention is indicated (class I) in symptomatic patients with a valve area ≤1.5 cm2. PMC is indicated as the preferred intervention (class I) in all patients with favourable clinical and anatomical (echo score) characteristics. PMC should also be considered (class IIa) where clinical characteristics are favourable though anatomy is not. PMC should also be considered (class IIa) in asymptomatic patients if they have a high risk of thromboembolism or haemodynamic decompensation. PMC is contraindicated where valve area >1.5 cm2; in the presence of left atrial thrombus; if there is >mild MR; severe calcification; or there is an existing indication for cardiac surgery (eg, CABG for CAD).5
Valve replacement in MS is reserved for restenosis following earlier commissurotomy, if the valve morphology is not suitable, non-rheumatic aetiology or coexistent severe MR or aortic disease.
Asymptomatic patients are observed for evidence of deterioration or complication. Sudden deterioration is common and is usually due to atrial fibrillation, embolism or pregnancy (typically at 20 weeks). Paradoxically, symptoms may appear to improve with development of right heart failure due to the subsequent reduction of left atrial filling pressures. This is an indicator of advanced, inoperable, end-stage disease.
Long acting nitrates and diuretics provide short-lived relief from breathlessness. β-blockers and rate-limiting calcium channel blockers can improve exertional symptoms. Anticoagulation is essential in all grades of atrial fibrillation. It should be considered in sinus rhythm if there has been previous embolic disease, prior left atrial thrombus, or where echocardiography demonstrates an enlarged left atrium or dense spontaneous echo-contrast.
Prophylaxis against endocarditis
In view of an absence of scientific evidence of the efficacy of antibiotic prophylaxis, the indications for prophylaxis in exposure-prone procedures have been substantially reduced in recent guidance. The ESC recommends prophylaxis only for patients with prosthetic valves or intracardiac prosthetic material, a history of previous endocarditis or cyanotic congenital heart disease. Procedures requiring prophylaxis include dental treatment with manipulation of the periapical region of the teeth or gingiva or perforation of the oral or respiratory tract mucosa. No other procedures require prophylaxis.26 Prophylaxis is given 30–60 min pre-procedure and comprises a single dose of amoxicillin or ampicillin 2–3 g orally/intravenously. In cases of penicillin allergy, the alternative is clindamycin 600 mg orally/intravenously. NICE, unlike the European and American societies, no longer recommends antibiotic prophylaxis.28
The service cardiologist confirms a diagnosis of severe AR secondary to BAV disease. This serviceman, who is symptomatic and career-limited by his condition, has severe AR. The service cardiologist recognises the clear indication for surgical intervention and refers the sergeant to a cardiothoracic surgical centre for multidisciplinary workup. Pending surgical intervention, he is instructed not to participate in competitive sports. The cardiologist endorses the temporary restriction of ‘unfit strenuous exertion’ and recommends medically limiting his ability to deploy, pending definitive management.
No medical therapy is indicated in this case as there is no evidence of heart failure. Because of his young age and military occupation, he is referred to a specialist centre that is able to offer native valve repair and high-complexity valve replacement procedures. He elects for a valve repair procedure understanding that there is a 25% chance he will require a valve replacement within 10 years. In the event of requiring aortic valve replacement, he is aware that he would be offered a mechanical valve, in preference to a bioprosthetic valve, owing to its greater longevity.
He understands that a mechanical valve would require lifelong anticoagulation with warfarin and regular international normalised ratio (INR) testing. He would be at an increased bleeding risk and this would be incompatible with operational military service
Valve disease and the military practitioner
British military guidance states that applicants for entry to service are unfit if they have established heart disease.29 The exceptions to this are: recruits who have ‘undergone successful correction of patent ductus arteriosus, atrial septal defect or ventricular septal defect’, recruits who have ‘benign physiological murmurs’ or have ‘uncomplicated, functionally acceptable mitral valve prolapse requiring no treatment’. Other valvular conditions, including BAVs, are incompatible for selection to the services.29
In a military population, pre-existing, symptomatic valvular heart disease is likely to be screened out by entry medical, selection and fitness requirements. Therefore, the military practitioner is most likely to encounter mild, asymptomatic (and previously undiagnosed) congenital valve disease that has worsened with age. It is also possible that undetected MS may present (usually second trimester) in pregnancy.
In this young population, regurgitation or stenosis complicating congenital BAV will be over-represented. Rarer, acquired causes of valve disease (including infective endocarditis, thrombotic and autoimmune disease) are differentials to consider in this group.
Awareness and understanding of valvular heart disease is important for military practitioners because undiagnosed valvular lesions in our service personnel may develop complications that can potentially impact on their health and threaten their combat effectiveness.
Without the vigilance and clinical acumen of military generalists, heart disease in soldiers, sailors and airmen may be missed. Servicemen with valve disease may be diagnosed at routine screening medical, incidentally when presenting with another complaint, or when presenting with a problem precipitated by their valve pathology.
Where there is suspicion of valvular heart disease, the military patient should be referred to a military cardiologist for occupational opinion and further management.
Correction notice This article has been corrected since it was published Online First. The order of the authorship has changed.
Contributors DAH structured and wrote the manuscript with assistance from JM. JC gave his comments based on many years of valve disease work. SJ and AW gave their comments based on their military occupational experience.
Competing interests None declared.
Provenance and peer review Commissioned; internally peer reviewed.