A 35-year-old woman from rural India presents with progressive exertional dyspnea and orthopnea for 2 years. She has a history of acute rheumatic fever at age 15. On examination, she has an irregular pulse, a loud S1, and a low-pitched diastolic rumble at the apex. Echocardiography confirms mitral stenosis with a valve area of 1.2 cm². The pathological specimen shows that the structure marked **C** (thickened chordae tendineae) is shortened, fused, and restricts leaflet motion. Which of the following best explains the hemodynamic consequence of this pathological change?

Explanation

## Why "Obstruction to left ventricular filling with elevated left atrial pressure and pulmonary venous hypertension" is right The thickened, shortened, and fused chordae tendineae (marked **C**) are a cardinal pathological feature of rheumatic mitral stenosis. These changes, along with commissural fusion and leaflet thickening, create a funnel-shaped, restrictive valve that obstructs diastolic flow from the left atrium to the left ventricle. This obstruction prevents normal LV filling, causing blood to back up into the left atrium, elevating LA pressure. The elevated LA pressure is transmitted retrograde through the pulmonary veins, causing pulmonary venous hypertension, which leads to pulmonary edema, dyspnea, orthopnea, and eventually pulmonary hypertension and right heart failure. This is the defining hemodynamic abnormality of mitral stenosis (Robbins 10e Ch 12; Harrison 21e Ch 263). ## Why each distractor is wrong - **Reduced left atrial pressure and decreased pulmonary venous congestion**: This is the opposite of what occurs. Stenosis causes LA pressure to *rise*, not fall, because the narrowed valve prevents adequate emptying of the LA into the LV. - **Increased mitral regurgitation with volume overload of the left ventricle**: While some degree of mitral regurgitation may coexist, the primary pathology is stenosis (obstruction), not regurgitation. The fused chordae and commissures create a restrictive, stenotic lesion, not an incompetent one. - **Reduced aortic valve closure pressure and early diastolic murmur**: The pathology is at the mitral valve, not the aortic valve. The diastolic murmur in mitral stenosis is low-pitched and heard at the apex, not early diastolic at the left sternal border. **High-Yield:** Rheumatic mitral stenosis in India is almost always due to chronic post-streptococcal sequelae; the fused, thickened chordae create a funnel-shaped valve that obstructs LV filling and raises LA pressure—the key hemodynamic derangement. [cite: Robbins 10e Ch 12; Harrison 21e Ch 263]