A 32-year-old woman from rural Maharashtra presents with progressive dyspnea and palpitations over 6 months. She has a history of severe, recurrent hypertension (BP 160/100 mmHg today) for 3 years, managed irregularly with antihypertensives. On examination, she has a sustained apical impulse displaced 2 cm lateral to the midclavicular line. Echocardiography shows left ventricular wall thickness of 16 mm (normal <11 mm), normal chamber dimensions, and normal ejection fraction. Cardiac catheterization reveals elevated left ventricular end-diastolic pressure. Which cellular adaptation best explains the cardiac pathology observed in this patient?

Explanation

## Diagnosis: Concentric Left Ventricular Hypertrophy **Key Point:** The clinical presentation—chronic hypertension, increased wall thickness with normal chamber size, and preserved ejection fraction—is pathognomonic for **concentric left ventricular hypertrophy (LVH)**, a form of cellular hypertrophy, not hyperplasia. ## Pathophysiology of Hypertrophy in This Case 1. **Chronic pressure overload** from sustained hypertension increases wall stress on cardiomyocytes. 2. **Mechanotransduction** activates growth signaling pathways (PI3K/Akt, MAPK) within individual myocytes. 3. **Individual cardiomyocytes enlarge** (increase in cell size and protein content), not increase in number. 4. **Result:** Thickened ventricular wall with normal or reduced chamber volume—concentric hypertrophy. ## Hypertrophy vs. Hyperplasia | Feature | Hypertrophy | Hyperplasia | |---------|-------------|-------------| | **Cell number** | Unchanged | Increased | | **Cell size** | Increased | Normal or slightly ↑ | | **Mechanism** | Increased protein synthesis | Cell division (mitosis) | | **In adult heart** | ✓ Primary response to load | ✗ Cardiomyocytes rarely divide | | **Reversibility** | Partial (with load removal) | Partial | **High-Yield:** Adult cardiomyocytes are terminally differentiated and have minimal mitotic capacity. Cardiac adaptation to chronic load is **hypertrophy only**, not hyperplasia. ## Concentric vs. Eccentric Hypertrophy ```mermaid flowchart TD A[Cardiac Hypertrophy]:::outcome --> B{Type of Load?}:::decision B -->|Pressure overload<br/>Hypertension, AS| C[Concentric LVH]:::action B -->|Volume overload<br/>AR, MR, dilated CM| D[Eccentric LVH]:::action C --> E[↑ Wall thickness<br/>Normal/↓ chamber size<br/>Preserved EF initially]:::outcome D --> F[↑ Wall thickness<br/>↑ Chamber size<br/>↓ EF]:::outcome ``` **Clinical Pearl:** The **displaced apical impulse** (2 cm lateral to midclavicular line) indicates ventricular enlargement in the anteroposterior dimension, but the normal chamber size on echo confirms this is concentric (not eccentric) hypertrophy—the wall is thick, but the cavity is not dilated. ## Why Ejection Fraction Remains Normal Initially - Hypertrophied myocardium maintains contractility initially. - Increased wall thickness compensates for increased wall stress (LaPlace's law: $\sigma = \frac{PR}{2h}$, where ↑*h* reduces stress). - With prolonged hypertension, diastolic dysfunction develops (impaired relaxation, elevated LVEDP), as seen here. **Mnemonic:** **CHOP** = **C**oncentric hypertrophy from **H**ypertension/pressure **O**verload, **P**reserved EF (initially).