Valvular Heart Disease: An Approach to Murmurs

Introduction

The four cardiac valves keep blood moving in one direction. A valve can fail in two ways: it can fail to open properly (stenosis), obstructing forward flow and imposing a pressure load on the chamber behind it; or it can fail to close properly (regurgitation), allowing backward flow and imposing a volume load.

That distinction explains nearly everything downstream. Pressure overload produces concentric hypertrophy - a thick-walled, non-dilated chamber, as in aortic stenosis. Volume overload produces eccentric hypertrophy - a dilated chamber, as in aortic or mitral regurgitation. The pattern determines the symptoms, the examination findings and the timing of surgery.

Valvular disease affects over 10% of people above 75 in the UK and is becoming more common as the population ages. It is also one of the highest-yield examination topics, because the diagnosis can genuinely be made at the bedside.

Aetiology

Clinical features

Valvular disease is often silent for years, because the ventricle compensates. Symptoms appear when compensation fails, and their onset is a critical point in the natural history - in aortic stenosis it is the trigger for surgery.

• Breathlessness on exertion, then orthopnoea and paroxysmal nocturnal dyspnoea - the commonest symptom of most lesions
• Chest pain - typically in aortic stenosis, from increased myocardial demand with reduced coronary perfusion
• Syncope or pre-syncope on exertion - a red flag, classically in severe aortic stenosis
• Palpitations - atrial fibrillation is common, particularly in mitral disease where the left atrium dilates
• Fatigue and reduced exercise tolerance
• Ankle swelling and abdominal distension - right-sided lesions or advanced left-sided disease
• Haemoptysis - classically in mitral stenosis, from raised pulmonary venous pressure

Ask specifically about rheumatic fever or frequent sore throats in childhood, intravenous drug use, previous valve surgery, dental care, and a family history of sudden death or connective tissue disease.

Examining a murmur

A systematic approach makes murmurs far more tractable than they first appear. Work through: timing, site, radiation, character, intensity, and what changes it.

Where to listen

Timing narrows it to two

The logic is simple: in systole the ventricles contract, so blood should be leaving through the aortic and pulmonary valves and the mitral and tricuspid valves should be shut. A systolic murmur therefore means either an obstructed outflow valve or a leaking inflow valve. Diastole reverses the pairing.

Grading intensity

The Levine scale grades murmurs 1 to 6. Grade 1 is barely audible; grade 2 is quiet but clearly heard; grade 3 is moderately loud with no thrill; grade 4 is the first with a palpable thrill; grade 5 is audible with the stethoscope barely touching the chest; grade 6 is audible with it lifted off. The presence of a thrill is the reproducible landmark - and intensity correlates poorly with severity, since a critically stenotic valve may generate a quiet murmur because so little blood is crossing it.

Investigations

• Transthoracic echocardiography - the definitive investigation. It identifies which valve, whether stenosis or regurgitation, grades severity, and measures the consequences: chamber sizes, ejection fraction and pulmonary pressures.
• Transoesophageal echocardiography (TOE) - better views of the mitral valve, prosthetic valves and vegetations; used where transthoracic images are inadequate and in suspected endocarditis
• ECG - left ventricular hypertrophy in aortic stenosis; left atrial enlargement (P mitrale) and atrial fibrillation in mitral disease; right ventricular hypertrophy in pulmonary and tricuspid disease
• Chest X-ray - cardiomegaly, pulmonary congestion, a calcified valve, and left atrial enlargement
• Bloods - FBC and inflammatory markers, blood cultures if endocarditis is suspected, U&Es, and NT-proBNP
• Cardiac CT or MRI - valve calcium scoring, aortic root assessment, and quantifying regurgitation
• Coronary angiography - performed before valve surgery in anyone with risk factors, since coexisting coronary disease is common and can be grafted at the same operation
• Exercise testing - carefully used in apparently asymptomatic severe aortic stenosis to unmask symptoms

Management

No drug reverses valvular disease. Medical therapy manages the consequences - heart failure, atrial fibrillation, hypertension - while the definitive question is whether and when to intervene.

Surveillance

Asymptomatic patients with mild or moderate disease are followed with serial echocardiography, the interval depending on the lesion and its severity - typically every 3-5 years for mild disease and annually for severe. The purpose is to catch the transition to symptoms or to ventricular decompensation before irreversible damage occurs.

Deciding to intervene

Two triggers dominate across all lesions: the onset of symptoms, and evidence that the ventricle is failing - a falling ejection fraction or progressive dilatation - even in a patient who feels well. Decisions are made by a multidisciplinary heart team.

Choosing a prosthetic valve

Complications

• Heart failure - the common endpoint of every untreated significant lesion
• Atrial fibrillation - particularly with mitral disease and left atrial dilatation, bringing its own stroke risk
• Infective endocarditis - abnormal and prosthetic valves are both at increased risk
• Pulmonary hypertension and right heart failure - from chronically raised left-sided pressures
• Systemic embolism - from left atrial thrombus in mitral stenosis with atrial fibrillation, or from valve vegetations
• Sudden cardiac death - notably in severe aortic stenosis, especially once symptomatic
• Prosthetic valve complications - thrombosis, structural degeneration, paravalvular leak, haemolysis and endocarditis

Red flags

Prognosis

Prognosis varies enormously with the lesion, its severity and whether it has been corrected. Mild asymptomatic disease may never progress to needing intervention; severe symptomatic aortic stenosis left untreated has an outlook worse than many cancers.

The general rule is that valve replacement performed before the ventricle decompensates restores a near-normal life expectancy, whereas surgery performed after irreversible ventricular damage does not. This is why asymptomatic patients are followed with serial imaging rather than discharged, and why a falling ejection fraction is an indication to operate even in someone who feels well.

The arrival of transcatheter techniques has substantially changed the outlook for older and frailer patients, many of whom were previously offered nothing because open surgery was too risky.