A 32-year-old woman from rural Maharashtra presents with progressive dyspnea on exertion and orthopnea for 6 months. She has a history of recurrent severe anemia (Hb 6–7 g/dL) managed with transfusions and iron supplementation. On examination, she has a hyperdynamic precordium and a systolic flow murmur. Chest X-ray shows cardiomegaly with pulmonary congestion. Echocardiography reveals a dilated left ventricle with increased wall thickness and normal ejection fraction initially, but progressive decline. Which cellular adaptation in the myocardium is the primary pathologic mechanism underlying her cardiac dysfunction?

Explanation

## Clinical Context This patient has chronic severe anemia causing high-output cardiac stress. The heart must increase stroke volume to maintain oxygen delivery, resulting in volume overload (increased preload) rather than pressure overload. ## Pathophysiology of Cardiac Adaptation **Key Point:** Eccentric hypertrophy occurs in response to **increased preload** (volume overload), while concentric hypertrophy occurs with **increased afterload** (pressure overload). In chronic anemia: - Reduced oxygen-carrying capacity → compensatory increase in cardiac output - Increased venous return → dilation of the left ventricle - Myocytes lengthen (sarcomeres added in series) → eccentric hypertrophy - Wall thickness may increase, but the ratio of wall thickness to chamber radius decreases **Clinical Pearl:** Eccentric hypertrophy is characteristic of dilated cardiomyopathy and is seen in: - Chronic anemia - Aortic regurgitation - Mitral regurgitation - Dilated cardiomyopathy - High-output states (hyperthyroidism, pregnancy, AV fistula) ## Distinction: Eccentric vs. Concentric Hypertrophy | Feature | Eccentric | Concentric | |---------|-----------|------------| | **Stimulus** | Increased preload (volume) | Increased afterload (pressure) | | **Mechanism** | Sarcomeres in series | Sarcomeres in parallel | | **Chamber shape** | Dilated | Normal or small | | **Wall thickness** | Normal or ↓ | ↑↑ | | **Wall/radius ratio** | ↓ | ↑ | | **Examples** | Anemia, AR, MR | Hypertension, AS | | **Prognosis** | Worse (dilates further) | Better (maintains function longer) | **High-Yield:** The progressive decline in ejection fraction in this case indicates that eccentric hypertrophy is maladaptive in the long term — the ventricle dilates beyond its optimal length-tension relationship, leading to systolic dysfunction. ## Why Not the Other Options? - **Concentric hypertrophy** occurs with pressure overload (e.g., hypertension, aortic stenosis), not volume overload from anemia. - **Hyperplasia** (cell division) does NOT occur in adult cardiomyocytes; they are terminally differentiated and adapt only by hypertrophy. - **Atrophy** is not the primary mechanism here; the ventricle is dilating, not shrinking.