Summary Valvular heart disease involves either stenosis , a narrowing that impedes forward blood flow and causes pressure overload, or regurgitation , a valve's
Summary Valvular heart disease involves either stenosis , a narrowing that impedes forward blood flow and causes pressure overload, or regurgitation , a valve's inability to fully close leading to backward blood leakage and volume overload. The left-sided mitral and aortic valves are most frequently affected due to higher systemic pressures. Common etiologies include rheumatic heart disease , calcific degeneration , infective endocarditis , and mitral valve prolapse , each presenting with characteristic pathophysiological consequences and clinical signs, often progressing to heart failure or systemic complications like stroke. Key Points - Stenosis is characterized by a narrowed valve opening, leading to pressure overload and hypertrophy of the chamber behind the affected valve. - Regurgitation results from a valve failing to close completely, causing blood to leak backward, leading to volume overload and dilation of the affected chamber. - Rheumatic heart disease is the predominant cause of mitral stenosis , resulting in fibrosed, fused leaflets with a classic "fish mouth" appearance. - Mitral regurgitation is commonly associated with mitral valve prolapse or papillary muscle rupture post-MI, causing both left atrial and left ventricular enlargement . - Aortic stenosis in the elderly is primarily calcific/degenerative , leading to concentric left ventricular hypertrophy and manifesting clinically as the SAD triad ( Syncope, Angina, Dyspnea ). - Aortic regurgitation results in significant left ventricular dilation and hypertrophy due to chronic volume overload, leading to a characteristic wide pulse pressure and various peripheral signs. - Infective endocarditis involves bacterial vegetations on heart valves, with Staph aureus being common in acute cases (e.g., IV drug users, often affecting the tricuspid valve ) and Strep viridans in subacute cases (e.g., dental procedures, damaged valves). - Acute Rheumatic Fever , caused by Group A Strep , triggers an autoimmune response leading to pancarditis and Aschoff bodies , often progressing to chronic rheumatic heart disease predominantly affecting the mitral valve . Detailed Notes The Heart Has 4 Chambers Blood flows sequentially through the heart's chambers: RIGHT ATRIUM → RIGHT VENTRICLE → LUNGS → LEFT ATRIUM → LEFT VENTRICLE → BODY . The 4 Valves & Their Positions The heart contains four valves, each positioned to ensure unidirectional blood flow: - Between Right Atrium & Right Ventricle → TRICUSPID VALVE (3 leaflets) - Between Right Ventricle & Pulmonary Artery → PULMONIC VALVE - Between Left Atrium & Left Ventricle → MITRAL VALVE (2 leaflets) - Between Left Ventricle & Aorta → AORTIC VALVE Why Left Side Gets Damaged More The left side of the heart pumps blood to the ENTIRE body , handling approximately 5 times more pressure than the right side. Consequently, its valves experience greater wear and tear, making them more susceptible to damage and disease. Two Types of Valve Problems Valvular heart disease generally falls into two categories based on the functional deficit: Type Definition Effect on Heart --- --- --- Stenosis Valve opening is NARROWED Chamber BEHIND valve works harder → Pressure overload → Hypertrophy Regurgitation/Insufficiency Valve doesn't close properly → blood leaks BACK Chamber BEHIND valve overfills → Volume overload → Dilation Pressure Overload vs Volume Overload In stenosis , the chamber pushes against resistance, causing its walls to get THICK ( Hypertrophy ), similar to a weightlifter's muscles. Conversely, in regurgitation , the chamber fills with extra blood, leading to the chamber becoming BIG and DILATED , akin to a balloon being overfilled. PART 2: MITRAL STENOSIS (MS) Definition Mitral stenosis (MS) is the narrowing of the mitral valve opening. The normal valve area is 4-6 cm² , with symptoms typically beginning when it drops below 2 cm² , and becoming critical at 1 cm² . Cause Rheumatic Heart Disease is responsible for nearly 99% of all MS cases . Rarely, other causes include congenital defects, carcinoid syndrome, or lupus. Pathogenesis — Step by Step The development of mitral stenosis is a multi-step process: - Acute Rheumatic Fever: A Group A Streptococcus ( Strep pyogenes ) throat infection triggers the immune system to make antibodies against Strep M-protein . This M-protein LOOKS LIKE cardiac proteins ( molecular mimicry ), causing the antibodies to attack the HEART by mistake. This leads to inflammation of all heart layers, termed PANCARDITIS , and the mitral valve leaflets become inflamed, forming small vegetations. - Chronic Scarring (Years Later): Repeated episodes of rheumatic fever cause the leaflets to become FIBROSED and FUSED at the commissures. Concurrently, the chordae tendineae become SHORTENED and THICKENED . This process narrows the valve opening, leading to STENOSIS , which gives the valve a classic " FISH MOUTH " or " BUTTONHOLE " appearance. - Consequences of Obstruction: The narrowed mitral valve obstructs the free flow of blood from the Left Atrium (LA) to the Left Ventricle (LV) . Blood then backs up into the Left Atrium , causing LA pressure to rise and the LA to DILATE (enlarge). This increased LA pressure further backs up into the pulmonary veins, leading to pulmonary venous hypertension and eventually PULMONARY EDEMA (manifesting as dyspnea ). Chronic pulmonary hypertension subsequently causes RIGHT HEART STRAIN , leading to right ventricular hypertrophy and ultimately RIGHT HEART FAILURE . - Atrial Fibrillation: As the LA dilates and stretches, its electrical pathways become disrupted, leading to the development of ATRIAL FIBRILLATION . Blood then pools and stagnates in the LA (particularly in the LA appendage), which promotes THROMBUS FORMATION . If a thrombus breaks off, it can cause SYSTEMIC EMBOLISM , most dangerously resulting in a STROKE . Gross Pathology The following findings are characteristic in the gross pathology of mitral stenosis : Finding Description --- --- Leaflet fusion Commissures fused → " fish mouth " valve Leaflet thickening Fibrosis and calcification Short chordae Pulled down, thickened, fused LA enlargement Massive — can compress esophagus LA thrombus Especially in LA appendage Clinical Features Symptoms Patients with mitral stenosis exhibit a range of symptoms due to the pathophysiological changes: Symptom Mechanism --- --- Dyspnea on exertion Pulmonary venous hypertension Orthopnea/PND Pulmonary edema when lying flat Hemoptysis Rupture of bronchial veins from high pressure Palpitations Atrial fibrillation Stroke LA thrombus embolization Hoarse voice Enlarged LA compresses recurrent laryngeal nerve Dysphagia Enlarged LA compresses esophagus Signs Physical examination of mitral stenosis reveals distinct signs: Sign Description --- --- Malar flush Pinkish-purple cheeks from low cardiac output Loud S1 Valve snaps shut from being held open Opening snap Stiff leaflets snap open in diastole Mid-diastolic rumble Turbulent flow through narrow valve CXR Findings Chest X-ray in mitral stenosis typically shows: - Enlarged LA (double density sign, splaying of carina) - Pulmonary venous congestion (upper lobe diversion) - Kerley B lines (pulmonary edema) - Calcified mitral valve - Normal LV size ( LV is actually SMALL/normal in pure MS ) Key MCQ Facts - The most common cause of mitral stenosis is Rheumatic heart disease . - The most common valve affected in rheumatic disease is the Mitral valve , followed by the Aortic valve , then the Tricuspid valve (the pulmonic valve is almost never affected). - The most common complication of mitral stenosis is Atrial fibrillation . - The most dangerous complication is Stroke from LA thrombus . - The LV is NORMAL in pure mitral stenosis ; only the LA enlarges. - Mitral stenosis is the only valvular lesion more common in WOMEN than men . PART 3: MITRAL REGURGITATION (MR) Definition Mitral regurgitation (MR) occurs when the mitral valve fails to close completely during systole, causing bl