A 58-year-old man with a 20-year history of poorly controlled hypertension (BP 160–180/100–110 mmHg) presents with dyspnea and fatigue. Physical examination reveals a sustained apical impulse and an S4 gallop. Echocardiography shows a small left ventricular cavity with marked wall thickening (interventricular septum 18 mm), normal ejection fraction, and diastolic dysfunction. Histopathology of a myocardial biopsy specimen would most likely reveal which cellular adaptation?

Explanation

## Clinical Scenario Analysis This patient has **chronic hypertension** causing sustained **increased afterload** (pressure overload) on the left ventricle. The echocardiographic findings are classic for concentric hypertrophy: - Small LV cavity - Marked wall thickening - Normal ejection fraction (initially preserved) - Diastolic dysfunction (due to reduced compliance) ## Pathophysiology of Concentric Hypertrophy **Key Point:** Concentric hypertrophy is the adaptive response to **increased afterload (pressure overload)**. It is characterized by: 1. **Mechanism:** Addition of sarcomeres **in parallel** (side-by-side) 2. **Result:** Increased myocyte width and wall thickness 3. **Chamber geometry:** Normal or reduced cavity size 4. **Wall-to-radius ratio:** Increased (maintains wall stress) 5. **Function:** Ejection fraction preserved initially; diastolic dysfunction develops **High-Yield:** The S4 gallop in this patient reflects **reduced ventricular compliance** — a hallmark of concentric hypertrophy. The stiff, thickened ventricle resists filling, causing forceful atrial contraction (audible as S4). ## Comparison: Concentric vs. Eccentric Hypertrophy | Feature | Concentric | Eccentric | |---------|-----------|------------| | **Stimulus** | Pressure overload (afterload ↑) | Volume overload (preload ↑) | | **Sarcomere arrangement** | In parallel | In series | | **Wall thickness** | ↑↑ | Normal or ↓ | | **Chamber size** | Normal/small | Dilated | | **Wall-to-radius ratio** | ↑ | ↓ | | **Ejection fraction** | Preserved (initially) | Reduced | | **Diastolic function** | ↓ (stiff) | ↓ (dilated) | | **Common causes** | HTN, AS, HCM | Anemia, AR, MR, DCM | | **Prognosis** | Better initially | Worse | **Clinical Pearl:** Concentric hypertrophy is an **initially adaptive** response that maintains ejection fraction despite increased pressure. However, over time, the thickened myocardium becomes stiff, diastolic dysfunction worsens, and eventually systolic dysfunction may develop ("burnt-out" hypertensive heart disease). ## Histopathologic Findings in Concentric Hypertrophy - Enlarged myocyte nuclei (polyploidy common) - Increased myofibril density - Minimal interstitial fibrosis (initially) - Normal or reduced capillary density (relative ischemia) - Organized sarcomere arrangement