Valvular Heart Disease

The four valves (tricuspid, pulmonary, mitral, aortic) open and close to keep blood moving in one direction; if one does not open or close correctly, flow is disturbed and the heart is strained. There are two functional lesions. In stenosis the flaps become thick, stiff, or fused so the valve cannot open all the way. In regurgitation the flaps fail to seal and blood leaks backward — when the flaps bulge or flop back into the chamber behind them, that is prolapse, most often of the mitral valve. A valve can be both stenotic and regurgitant at once, and a congenital valve with no opening at all is atresia.

The ventricle behind each lesion remodels according to the load it is handed, and that fork organizes the whole topic. Stenosis is pressure overload: the ventricle pumps against a fixed obstruction, so the wall thickens inward — concentric hypertrophy — as in the concentric LV hypertrophy of aortic stenosis. Regurgitation is volume overload: each beat the ventricle must handle the regurgitant volume plus the forward volume, so the chamber stretches and dilates with eccentric hypertrophy, as in chronic aortic regurgitation, where eccentric hypertrophy develops and chamber dilation ensues, and chronic mitral regurgitation, where volume overload dilates the ventricle.

Turbulent flow across a failed valve is what you hear. A murmur is the blowing, whooshing, or rasping sound of rapid, choppy blood flow, and its timing tells you which lesion is present: a systolic murmur falls between S1 and S2 (holosystolic = throughout systole), a diastolic murmur falls after S2 and before S1. Intensity is graded I–VI: grade I is faint and barely audible, grade III is easily audible without a thrill, and grade IV is easily audible with a palpable thrill (V and VI are heard with the stethoscope barely touching or off the chest). Not every murmur is disease — innocent flow murmurs are mid-systolic, come from increased cardiac output in childhood and pregnancy, cause no symptoms, and resolve on their own.

Aortic stenosis (AS) obstructs left-ventricular outflow — a jet velocity of at least 2 m/s across the valve separates true stenosis from mere sclerosis (thickening without a gradient). The cascade runs: obstruction → higher LV systolic pressure and a prolonged ejection time → increased afterload → concentric LV hypertrophy → diastolic dysfunction and fibrosis. The hypertrophied wall demands more oxygen (higher pressure, more mass, longer ejection) while its perfusion time shrinks, so LV function deteriorates with rising oxygen consumption and falling supply. That mismatch explains the classic triad. Angina: the thick myocardium needs more oxygen than compressed coronaries can deliver, with or without coronary disease. Syncope: on exertion the body vasodilates, but the stenotic valve passes only a fixed cardiac output, so arterial pressure falls and the brain is under-perfused. Dyspnea: the stiff ventricle raises its end-diastolic pressure, which transmits backward as pulmonary venous hypertension and pulmonary edema.

The sound of AS is a mid-systolic crescendo-decrescendo ejection murmur heard best at the second right intercostal space, radiating to the right neck and carotids, with a slow-rising, late-peaking, low-amplitude carotid upstroke (pulsus parvus et tardus) in severe disease and an S4 from the hypertrophied ventricle. The trap that matters at the bedside: murmur intensity softens when the LV fails or stroke volume falls — a quieter murmur with a falling blood pressure is a failing ventricle, not improvement. Under 70 the usual cause is a congenital bicuspid valve (present in about 1% of the population); over 70 it is calcific degeneration of a normal three-leaflet valve, which is why AS affects up to 10% of people past 80. The latent period lasts roughly 10–20 years, and then the symptoms arrive together with the prognosis: without valve replacement, mortality after symptom onset exceeds 90% within a few years, with average survival of only about 1–3 years, and the risk of sudden cardiac death climbs. No drug slows AS; the only fix is a new valve.

Aortic regurgitation (AR) is the mirror image: blood runs back from the aorta into the LV during diastole. Chronically, the regurgitant volume raises end-diastolic volume, the LV hypertrophies eccentrically and dilates, and for years a huge stroke volume keeps the patient well. That big stroke volume distends the peripheral arteries and raises systolic pressure while diastolic run-off back into the ventricle drops diastolic pressure — the wide pulse pressure with a low diastolic BP and the bounding, collapsing water-hammer (Corrigan) pulse, head bobbing (de Musset), and nail-bed pulsation (Quincke). The murmur is a high-frequency early diastolic decrescendo blowing murmur at the third-to-fourth left intercostal space (longer means more severe); in severe AR the regurgitant jet strikes the anterior mitral leaflet and produces the Austin Flint murmur, a low-pitched mid-to-late diastolic rumble at the apex — which mimics mitral stenosis but has no opening snap. When compensation fails, sarcomeres are maximally stretched and fibrosis drops LV compliance. Acute AR (aortic dissection, endocarditis, trauma) is different and deadly: a non-dilated LV cannot accept the sudden volume, end-diastolic pressure spikes, the mitral valve closes prematurely, and pulmonary edema and cardiogenic shock follow — a surgical emergency in which the intra-aortic balloon pump is contraindicated because balloon inflation raises aortic diastolic pressure and worsens the leak.

Mitral stenosis (MS) narrows the mitral orifice, impairing LV filling, raising left atrial pressure, and producing progressive pulmonary congestion. The normal mitral annulus is about 4–6 cm²; flow is impeded once the area falls below 2 cm². The stenotic valve passes blood only in diastole, so anything that shortens diastole — tachycardia, atrial fibrillation, pregnancy, fever, anemia, exertion — raises the transmitral gradient and the left atrial pressure behind it; symptoms appear or worsen with anything that raises the heart rate. Three chains follow. Rhythm: chronic pressure stretches and enlarges the left atrium, which breeds atrial fibrillation; AF removes the atrial kick that a stenotic valve depends on for LV filling, so new AF can precipitate sudden congestive heart failure, and blood pooling in the enlarged atrium forms thrombus — the embolic stroke that makes anticoagulation part of MS care. Lungs: left atrial pressure transmits backward as pulmonary venous hypertension, pulmonary edema, and exertional dyspnea; engorged bronchial veins rupture and cause hemoptysis; reactive pulmonary hypertension eventually fails the right ventricle (JVD, hepatomegaly, ascites, peripheral edema).

The exam of MS is a set piece: a loud S1, an opening snap shortly after A2 (the abrupt tensing of the stenotic valve — the A2–snap interval shortens as stenosis worsens), and a low-pitched mid-diastolic rumbling murmur with presystolic accentuation, heard best with the bell at the apex in the left lateral decubitus position. The presystolic accentuation disappears once AF removes atrial contraction. Blood pressure is most often normal. Worldwide the cause is rheumatic heart disease — commissural fusion, leaflet thickening, subvalvular fibrosis — developing years to decades after the rheumatic episode (commonly 10–20 years, sometimes as early as 5–10), most often in women; in developed nations degenerative mitral annular calcification also causes it. Once pulmonary hypertension develops, average survival without intervention is about 3 years, whereas valve replacement gives roughly 80% survival at 10 years.

Mitral regurgitation (MR) sends blood backward from the LV into the LA during systole, producing a holosystolic blowing murmur at the apex that radiates to the left axilla, often with an S3 and a displaced apical impulse. Primary (organic) MR is structural leaflet, chordal, or papillary disease — most commonly mitral valve prolapse from myxomatous degeneration, which gives a mid-systolic click and a murmur that gets longer and louder on standing (less preload, earlier prolapse). Secondary (functional) MR is a structurally normal valve pulled open by a dilated, dysfunctional ventricle after ischemic or dilated cardiomyopathy. Chronic MR is a positive-feedback loop: volume overload dilates the ventricle, dilation widens the annulus, the wider annulus worsens leaflet coaptation, and the leak grows. The ejection fraction rises at first because the LV unloads into the low-pressure atrium — so a "normal" EF of 60% in MR already means LV dysfunction — and later LA enlargement, AF, and LV failure follow. Acute MR (papillary muscle rupture in 1–2% of patients after MI, chordal rupture, endocarditis) hits a non-compliant atrium that cannot buffer the volume: a precipitous fall in cardiac output, flash pulmonary edema, and cardiogenic shock — a new holosystolic murmur after an MI is papillary rupture until proven otherwise.

Acute rheumatic fever (ARF) is an abnormal immune response to group A Streptococcus infection, most commonly pharyngitis, arriving about 2–4 weeks after the strep infection. The mechanism is molecular mimicry: streptococcal M protein and related antigens cross-react with cardiac myosin, a type 2 hypersensitivity reaction that leaves Aschoff nodules in the heart. Carditis occurs in 50–80% of ARF, the mitral valve is involved in 50–60% with regurgitation usually the earliest lesion, the aortic valve in about 20%, the tricuspid in about 10% (only alongside left-sided disease), and the pulmonary valve rarely. ARF strikes mainly children aged 5–15; rheumatic heart disease (RHD) then peaks diagnostically in young adults aged 20–39, with the highest burden in Oceania, sub-Saharan Africa, and South Asia, and roughly 470,000 new ARF cases and 233,000 attributable deaths each year. Diagnosis uses the revised Jones criteria (2015): two major, or one major plus two minor, plus evidence of preceding strep infection (ASO or anti-DNase B titers, throat culture, or rapid antigen test) — major criteria are carditis, polyarthritis, Sydenham chorea, erythema marginatum, and subcutaneous nodules; minor are fever, arthralgia, elevated ESR/CRP, and a prolonged PR interval.

RHD is preventable at two points. Primary prevention is treating strep pharyngitis promptly — the WHO 2024 guideline strongly recommends penicillin (intramuscular or oral) as first line. Secondary prevention stops recurrences that scar the valve further: benzathine penicillin G 1.2 million units IM every 4 weeks (every 3 weeks in high-risk populations) or oral penicillin V, continued for 5 years or until age 21 without carditis, 10 years or until 21 after carditis without residual disease, and 10 years or until age 40 when carditis left residual valve disease. WHO names IM benzathine penicillin the preferred first-line approach for anyone with prior RF or RHD — the only cost-effective one.

A diseased or prosthetic valve is also the surface infective endocarditis (IE) needs. Turbulent flow across the abnormal valve injures the endothelium, platelets and fibrin lay down a sterile vegetation, and a transient bacteremia — oral flora after dental manipulation, IV lines, injection drug use — seeds it into a bacterial biofilm shielded from immune defenses. The people at highest risk are exactly the ones who get dental prophylaxis: prosthetic valves and prosthetic repair material (including TAVR valves), prior IE, unrepaired cyanotic congenital heart disease, and transplant valvulopathy. On a valve patient, fever plus a new or changed murmur is IE until the cultures say otherwise, and a new conduction block means a perivalvular abscess. Prosthetic valve endocarditis carries the highest mortality of any IE — one more reason the dentist comes before the new valve.