Prognostic and Pathophysiological Insights in Untreated Biventricular Systolic Dysfunction with Restrictive Filling and Hypertrophic Cardiomyopathy

Clinical Trajectories of Disease Progression

Sudden cardiac death can occur from unpredictable ventricular tachyarrhythmias, most often in patients younger than 35 years. [American College of Cardiology] 1
Progressive heart failure manifests as exertional dyspnea (with or without chest pain) and may evolve from initially preserved systolic function to end‑stage left‑ventricular remodeling and systolic dysfunction due to extensive myocardial scarring. [American College of Cardiology] [1][2]3
Atrial fibrillation (paroxysmal or chronic) frequently develops, increasing the risk of systemic thromboembolism and both fatal and non‑fatal stroke. [American College of Cardiology] [1][2]3

Severe hypertrophy and increased myocardial stiffness produce diastolic dysfunction that markedly reduces ventricular cavity size and stroke volume, creating a restrictive filling physiology. [Circulation] 5
Impaired ventricular relaxation makes ventricular filling highly dependent on atrial contraction, so patients poorly tolerate atrial fibrillation. [Circulation] 5
Elevated left‑ventricular diastolic and left‑atrial pressures lead to atrial enlargement, raised pulmonary venous pressures, and overt heart‑failure symptoms. [Circulation Research] 6; [Journal of the American College of Cardiology] 7
Progressive left‑ventricular diastolic dysfunction results in higher filling pressures, pulmonary congestion, and severe exercise intolerance. [Circulation Research] 6; [Journal of the American College of Cardiology] 7

Dyspnea and fatigue severely limit exercise capacity and overall quality of life in this population. [Journal of the American College of Cardiology] 8
Frequent hospital admissions for clinical stabilization are common, reflecting advanced (Stage D) heart‑failure status. [Journal of the American College of Cardiology] 8; [Circulation] 9

Ventricular tachyarrhythmias remain unpredictable and can occur even in asymptomatic patients, contributing to sudden cardiac death. [American College of Cardiology] [1][3]4

In hypertrophic cardiomyopathy patients with atrial fibrillation, the stroke risk is sufficiently high that oral anticoagulation should be considered the default therapy regardless of CHA₂DS₂‑VASc score. [American College of Cardiology] 11
Rapid atrial fibrillation is often poorly tolerated because ventricular filling relies heavily on atrial systole. [American College of Cardiology] 11

End‑stage heart failure may be preceded by left‑ventricular remodeling and systolic dysfunction caused by extensive myocardial scarring. [American College of Cardiology] [1][2]3
Collagen accumulation between hypertrophied myocytes and fascicles markedly increases myocardial stiffness. [Circulation Research] 6
Progressive extracellular protein deposition and fibrosis are directly linked to heightened left‑ventricular stiffness and represent a key structural milestone in the transition from compensated disease to symptomatic heart failure. [Circulation Research] 6

Hypertrophic cardiomyopathy predisposes to myocardial ischemia due to a mismatch between oxygen supply and demand. [Circulation] 5
Microvascular dysfunction—characterized by impaired coronary flow reserve, medial hypertrophy, and reduced intramural arteriole density—is common. [Circulation] 5
These microvascular abnormalities are amplified by hyperdynamic systolic function and left‑ventricular outflow‑tract obstruction, which generate high intracavitary pressures. [Circulation] 5

The natural history of hypertrophic cardiomyopathy can be modified by implantable cardioverter‑defibrillators, appropriate pharmacologic therapy, septal reduction procedures, and heart transplantation. [American College of Cardiology] [1][2][3][4]