cardiac murmur

**Pathophysiology:** Murmurs arise from turbulent (non-laminar) blood flow, favored by high flow velocity, low blood viscosity (anemia), or structural abnormalities (stenotic or regurgitant valves, shunts). Reynolds number rises with velocity and vessel diameter and falls with viscosity.

**Classification by timing** - *Systolic (between S1 and S2)* - Ejection (crescendo-decrescendo): aortic stenosis (AS), pulmonic stenosis, HOCM, innocent flow murmurs, ASD (via increased flow across the pulmonic valve). - Holosystolic (pansystolic): mitral regurgitation (MR), tricuspid regurgitation (TR), VSD. - Late systolic with midsystolic click: mitral valve prolapse (MVP). - *Diastolic (between S2 and S1)*: almost always pathologic. - Early diastolic decrescendo: aortic regurgitation (AR), pulmonic regurgitation (Graham Steell murmur in pulmonary HTN). - Mid-diastolic rumble: mitral stenosis (MS) after opening snap, tricuspid stenosis, Austin Flint murmur (severe AR), atrial myxoma ("tumor plop"). - *Continuous*: PDA ("machinery" murmur), AV fistula, venous hum.

**Key valve lesions** - **AS:** harsh crescendo-decrescendo at the right upper sternal border, radiates to carotids; pulsus parvus et tardus; syncope, angina, dyspnea (SAD). Causes: calcific degeneration, bicuspid valve, rheumatic disease. Softens with Valsalva or standing and louder with squatting (increased preload). - **MR:** holosystolic apical murmur radiating to the axilla. Causes: MVP, rheumatic heart disease, ischemic papillary muscle dysfunction or rupture, endocarditis, LV dilation. Louder with handgrip (increased afterload). - **MVP:** midsystolic click followed by a late systolic murmur. Murmur and click occur earlier with Valsalva or standing (decreased preload). Associated with Marfan and Ehlers-Danlos syndromes. - **HOCM:** systolic ejection murmur at the left sternal border. It *increases* with Valsalva or standing (decreased preload) and *decreases* with squatting or handgrip. It is the exception to the general rule. - **AR:** early diastolic blowing decrescendo murmur at the left sternal border, with a wide pulse pressure and a water-hammer pulse. Also causes de Musset sign, Quincke pulse, and Austin Flint murmur. Causes: aortic root dilation, bicuspid valve, endocarditis, Marfan syndrome, syphilis, aortic dissection. - **MS:** opening snap followed by a low-pitched mid-diastolic rumble at the apex, with a long murmur as stenosis worsens (shorter S2-opening snap interval). Almost always due to rheumatic heart disease. Complications: left atrial enlargement, AF, and Ortner syndrome. - **VSD:** holosystolic harsh murmur at the left lower sternal border. Smaller defects are louder. Eisenmenger syndrome reverses the shunt (right to left) and the murmur disappears. - **PDA:** continuous machinery murmur. Associated with congenital rubella and prematurity. Treat with indomethacin to close, and PGE1 to keep it open in ductal-dependent lesions.

**Maneuvers (high yield)** - Inspiration increases right-sided murmurs (Carvallo sign for TR); expiration increases left-sided murmurs. - Valsalva phase II and standing decrease venous return (preload): most murmurs soften, except HOCM and MVP, which get louder. - Squatting and passive leg raise increase preload and afterload: most murmurs get louder, while HOCM and MVP soften. - Handgrip increases afterload: MR, AR, and VSD get louder; AS and HOCM get softer.

**Intensity grading (systolic):** 1 faint; 2 soft but readily audible; 3 louder, no thrill; 4 palpable thrill; 5 audible with the stethoscope barely on the chest; 6 audible without the stethoscope touching the chest. A thrill is present at grade 4 or higher.

**Innocent (functional) murmurs:** soft (≤2/6), midsystolic, short, no radiation, no associated symptoms, and they vary with position. Common in children, pregnancy, fever, anemia, and hyperthyroidism (high-flow states). Still's murmur is a classic pediatric example (vibratory, LLSB).

**Clinical approach:** Red flags include a diastolic or continuous murmur, grade ≥3, a holosystolic murmur, a new murmur, syncope, chest pain, a click, a thrill, or symptoms of heart failure. Next step is a transthoracic echocardiogram. Treatment is directed at the underlying cause: valve repair or replacement for severe symptomatic disease (TAVR/SAVR for AS), endocarditis prophylaxis only for high-risk patients (prosthetic valve, prior endocarditis, certain congenital heart disease, transplant valvulopathy), and anticoagulation if there is AF with MS.

**Associations to remember:** Rheumatic fever leads to MS (most common) and MR. Endocarditis leads to acute MR/AR/TR; IV drug use classically involves the tricuspid valve. Carcinoid syndrome causes right-sided lesions (TR and pulmonic stenosis). Turner syndrome is associated with bicuspid aortic valve and coarctation.