Causes of Right Ventricular Enlargement
Right ventricular enlargement results from three primary mechanisms: pressure overload, volume overload, and intrinsic myocardial disease, with pulmonary hypertension and left heart failure being the most common culprits in clinical practice. 1
Primary Mechanisms and Causes
Pressure Overload Conditions
The RV responds to increased afterload with initial hypertrophy, followed by progressive dilation as decompensation occurs 1. Key causes include:
- Pulmonary hypertension (all forms - precapillary and postcapillary)
- Pulmonary arterial hypertension (PAH)
- Chronic thromboembolic disease
- Left heart disease causing postcapillary PH 2
- Chronic lung disease
- Pulmonic stenosis (valvular or subvalvular) 1
- Massive pulmonary embolism 1
Critical pitfall: In advanced pressure overload, declining pulmonary artery pressure despite persistent elevated pulmonary vascular resistance is an ominous sign indicating RV decompensation, not improvement 1.
Volume Overload Conditions
Volume overload causes disproportionate dilation along the RV free wall-to-septum axis, resulting in a more spherical (less elliptical) RV geometry 3. Primary causes:
- Tricuspid regurgitation (primary or secondary) 1
- Atrial septal defects (including sinus venosus type) 4
- Pulmonary regurgitation (post-repair tetralogy of Fallot, native disease) 5
- Ventricular septal defects with left-to-right shunt
- Anomalous pulmonary venous return 4
Left Heart Failure
RV dysfunction occurs in 48% of patients with heart failure with reduced ejection fraction (HFrEF), making it one of the most common causes of RV enlargement 1. The mechanisms are multifactorial:
- Postcapillary pulmonary hypertension from elevated left ventricular end-diastolic pressure
- Volume overload from functional tricuspid regurgitation
- Arrhythmias
- Direct involvement of the RV by the underlying cardiomyopathy process 1
Important distinction: Nonischemic dilated cardiomyopathy shows higher RV involvement (65%) compared to ischemic cardiomyopathy (16%), likely due to genetic predisposition affecting both ventricles 1.
Intrinsic RV Myocardial Disease
- RV myocardial infarction (typically from right coronary artery occlusion) 1
- Arrhythmogenic right ventricular cardiomyopathy
- Myocarditis with RV involvement 1
- Infiltrative cardiomyopathies (sarcoidosis, amyloidosis)
Heart Failure with Preserved Ejection Fraction (HFpEF)
RV dysfunction occurs in 33-50% of HFpEF patients, though distinguishing primary RV pathology from secondary changes due to pulmonary hypertension can be challenging given the afterload dependency of RV function 1.
Pathophysiologic Consequences
As RV enlargement progresses, ventricular interdependence becomes critical: RV dilation with pericardial constraint causes leftward septal shift, compressing the LV and impairing LV diastolic filling 1. This reduces cardiac output through both decreased RV forward flow and impaired LV preload 1.
The combination of RV systolic dysfunction and biventricular diastolic dysfunction creates a vicious cycle: reduced cardiac output impairs coronary blood flow (including RV perfusion), while elevated right-sided filling pressures cause coronary sinus congestion, potentially provoking RV ischemia even without coronary artery disease 1.
Clinical Significance
The presence of RV enlargement universally predicts worse outcomes across all etiologies. In HFrEF patients with RV dysfunction, there is a 2.4-fold increased risk of mortality, urgent transplantation, or LVAD placement at 90 days compared to those without RV involvement 1. RV dysfunction is the principal cause of death in pulmonary arterial hypertension and the primary cause of death in massive pulmonary embolism and RV infarction 1.