A 58-year-old man from Delhi presents to the emergency department with acute-onset chest pain radiating to the left arm for 2 hours. On examination, blood pressure is 95/60 mmHg, heart rate 110 bpm, and JVP is elevated at 8 cm H₂O. Auscultation reveals a new pansystolic murmur best heard at the apex. Chest X-ray shows pulmonary edema. Echocardiography confirms acute mitral regurgitation secondary to papillary muscle rupture. During the cardiac cycle, at which point does the regurgitant jet occur?

Explanation

## Understanding Mitral Regurgitation in the Cardiac Cycle **Key Point:** Mitral regurgitation (MR) occurs whenever there is a pressure gradient from the left ventricle to the left atrium, which happens exclusively during ventricular systole (ventricular ejection phase). ### Timing of Mitral Regurgitation During the cardiac cycle, the mitral valve normally closes at the onset of ventricular contraction (isovolumetric contraction phase). In acute MR due to papillary muscle rupture: 1. **Isovolumetric contraction** — valve begins to close; minimal regurgitation 2. **Ventricular ejection (systole)** — LV pressure >> LA pressure; blood flows backward through the incompetent valve into the atrium 3. **Isovolumetric relaxation** — ventricular pressure falls rapidly; regurgitation ceases 4. **Ventricular filling** — mitral valve is open; no regurgitation **Clinical Pearl:** The pansystolic (holosystolic) murmur in MR extends throughout systole because the pressure gradient persists from the moment of valve closure through the entire ejection phase. This contrasts with ejection murmurs (aortic stenosis) which are crescendo-decrescendo. ### Why This Patient Has Acute Severe MR Papillary muscle rupture (often following inferior MI) causes sudden, complete loss of leaflet support. The posterior papillary muscle is particularly vulnerable due to its single blood supply from the right coronary artery. **High-Yield:** Acute severe MR presents with: - Pansystolic murmur (best at apex, radiates to axilla) - Rapid rise in LA pressure → pulmonary edema - Hypotension (cardiogenic shock in severe cases) - Elevated JVP (right heart strain from acute pulmonary hypertension) ### Cardiac Cycle Phases and Valve Events | Phase | Duration | Valve Status | Pressure Gradient | MR Present? | |-------|----------|--------------|-------------------|-------------| | Isovolumetric contraction | 0.05 s | Mitral closing | LV > LA (minimal) | Minimal | | Ventricular ejection (systole) | 0.25 s | Mitral open (incompetent) | LV >> LA | **YES** | | Isovolumetric relaxation | 0.08 s | Aortic closing, mitral opening | LV < LA | No | | Ventricular filling (diastole) | 0.50 s | Mitral open | LA ≥ LV | No | **Mnemonic: IVCE** — **I**sovolumetric **V**entricular **C**ontraction then **E**jection (systole is when MR occurs). [cite:Harrison 21e Ch 297]