A 58-year-old man with hypertension and diabetes mellitus presents with palpitations and dyspnea. ECG confirms atrial fibrillation with rapid ventricular response. What is the most common structural cardiac cause of atrial fibrillation in this patient?

Explanation

## Most Common Structural Cause of AF in Developed Countries **Key Point:** Left ventricular hypertrophy (LVH) secondary to hypertension is the single most common structural cardiac cause of atrial fibrillation in India and developed nations. ### Pathophysiology of LVH-Induced AF 1. Chronic pressure overload → myocardial hypertrophy 2. Increased atrial wall tension and stretch 3. Atrial fibrosis and diastolic dysfunction 4. Altered atrial conduction and refractoriness 5. Substrate for re-entrant circuits ### Epidemiology in Indian Population | Cause | Prevalence in AF | Notes | |-------|------------------|-------| | Hypertension (LVH) | 40–50% | Most common in non-rheumatic AF | | Rheumatic mitral disease | 20–30% | Still significant in India; declining in developed nations | | Dilated cardiomyopathy | 10–15% | Ischemic or non-ischemic | | Hyperthyroidism | 5–10% | Functional cause; reversible | | Lone AF | 10–15% | No structural disease | | Atrial myxoma | <1% | Rare; usually presents with systemic symptoms | **High-Yield:** In a hypertensive patient with AF, LVH is the presumed mechanism until proven otherwise. Echocardiography will show increased LV mass index (>115 g/m² in men, >95 g/m² in women). **Clinical Pearl:** The combination of hypertension, diabetes, and AF in this patient creates a high-risk phenotype for stroke (CHA₂DS₂-VASc score ≥2), mandating anticoagulation regardless of AF pattern. ### Why LVH Predisposes to AF - **Mechanical stretch** → activation of stretch-sensitive ion channels (TREK-1, SAC) - **Atrial fibrosis** → slowed conduction and heterogeneous refractoriness - **Diastolic dysfunction** → elevated atrial filling pressures - **Autonomic imbalance** → increased sympathetic tone **Mnemonic: CHADS** (Common causes of AF in Hypertensives) - **C**orinary artery disease (ischemia) - **H**ypertension (LVH) - **A**lcohol (dilated cardiomyopathy) - **D**ilated cardiomyopathy - **S**tenosis (mitral, aortic) [cite:Harrison 21e Ch 226]