Can Left Ventricular Abnormalities Occur with Incomplete RBBB and Pulmonary Hypertension?
Yes, left ventricular hypertrophy (LVH) and dysfunction can absolutely coexist with incomplete right bundle branch block (RBBB) and pulmonary hypertension, though the ECG diagnosis of LVH becomes more challenging in this setting. 1
Clinical Context and Pathophysiology
Pulmonary hypertension frequently causes left ventricular involvement through multiple mechanisms:
- In pulmonary hypertension due to left heart disease (PH-LHD), which represents 65-80% of all PH cases, left ventricular dysfunction is the primary driver of the pulmonary hypertension 2
- Even in pulmonary arterial hypertension (PAH), left ventricular diastolic dysfunction can develop as a consequence of ventricular interdependence and septal shift 1, 2
- The distinction between pre-capillary PAH and post-capillary PH-LHD requires careful hemodynamic assessment, as a pulmonary capillary wedge pressure (PCWP) >15 mmHg excludes pre-capillary PAH and indicates left heart involvement 1
ECG Findings in This Clinical Scenario
Incomplete RBBB is commonly observed in pulmonary hypertension and does not exclude LVH:
- A documented case of a 24-year-old with pulmonary hypertension showed both right ventricular hypertrophy AND incomplete RBBB pattern on ECG, demonstrating these findings frequently coexist 1
- Incomplete RBBB is common in young athletes and represents a spectrum of physiological cardiac remodeling, but in the context of pulmonary hypertension it typically reflects pathological right ventricular changes 1
- The presence of ECG signs of right ventricular hypertrophy/strain has 100% specificity for distinguishing PAH from PH due to left ventricular diastolic dysfunction, though sensitivity is lower 3
Diagnostic Approach to LVH in the Presence of Incomplete RBBB
Modified ECG criteria should be applied when incomplete RBBB is present:
- Standard voltage criteria remain reasonably reliable: SV1 ≥2 mm, RV5 or V6 >15 mm, and QRS axis <-30° can be used for LVH detection even with RBBB 4, 5
- The combination of RV6 > RV5 AND S III + (R+S) maximum precordial lead ≥30 mm provides 57% sensitivity with 100% specificity for LVH in the presence of right bundle branch block 5
- RBBB reduces S wave amplitude in right precordial leads, which decreases sensitivity for detecting LVH using standard Sokolow-Lyon criteria 6
Essential Diagnostic Workup
Echocardiography is mandatory to definitively assess both ventricles:
- ECG alone is insufficient—echocardiography directly visualizes left ventricular wall thickness, chamber dimensions, systolic function, and diastolic parameters 1, 6
- Right heart catheterization may be required to measure PCWP and distinguish pre-capillary from post-capillary pulmonary hypertension, which directly determines whether left ventricular dysfunction is present 1
- In cases where PCWP is borderline (12-15 mmHg) or "pseudo-normal" due to diuretic therapy, exercise hemodynamic challenge can unmask left ventricular diastolic dysfunction 1
Critical Clinical Pitfalls
Do not assume incomplete RBBB excludes left heart disease:
- The most common cause of pulmonary hypertension is left heart disease, not isolated pulmonary arterial hypertension 2
- Heart failure with preserved ejection fraction (HFpEF) and diastolic dysfunction is a particularly challenging differential diagnosis, as PCWP may be only mildly elevated or appear normal at rest 1
- An elevated transpulmonary gradient (mean PAP - PCWP) >12 mmHg suggests intrinsic pulmonary vascular changes superimposed on passive congestion from left heart disease 1
The presence of right ventricular changes does not exclude concurrent left ventricular pathology:
- Patients can have combined post- and pre-capillary PH with both left ventricular dysfunction and secondary pulmonary vascular remodeling 2
- The natural history of heart failure often involves evolution from a "left ventricular phenotype" to a "right ventricular phenotype" as pulmonary hypertension and RV dysfunction develop 2