RV Basal Diameter of 4.6 cm is Abnormal
A right ventricular basal diameter of 4.6 cm (46 mm) indicates RV enlargement, as it exceeds the upper limit of normal (41 mm) established by the 2015 ASE/EACVI guidelines 1.
Normal Reference Values
The most authoritative guidelines from the American Society of Echocardiography and European Association of Cardiovascular Imaging (2015) establish clear cutoffs for RV dimensions 1:
- RV basal diameter normal range: 25-41 mm (mean 33 ± 4 mm)
- RV mid-cavity diameter normal range: 19-35 mm (mean 27 ± 4 mm)
Your measurement of 46 mm is 5 mm above the upper limit of normal, representing approximately 12% enlargement beyond the normal threshold.
Clinical Interpretation
RV dilatation is defined as a basal diameter >41 mm and mid-cavity diameter >35 mm in the RV-focused apical four-chamber view 1. This measurement should be obtained at end-diastole using the inner-edge-to-inner-edge method, with the maximal transversal dimension measured in the basal one-third of the RV inflow 1.
Important Considerations for Accuracy:
- Measurement technique matters: The diameter must be measured in a dedicated RV-focused view, not a standard four-chamber view, to avoid underestimation 1
- Body size indexing: Recent evidence suggests RV dimensions should ideally be indexed to body surface area (BSA), particularly when comparing across different body sizes 2. When indexed to BSA, normal values are approximately 18.4 mm/m² (16.5-20.3) for basal diameter
- Sex differences: Men typically have larger absolute RV dimensions than women, though these differences normalize when indexed to BSA 2
Clinical Significance
RV enlargement at this magnitude warrants investigation for underlying causes, including:
- Pulmonary hypertension (most common)
- Volume overload conditions (tricuspid regurgitation, atrial septal defect)
- RV cardiomyopathy
- Chronic lung disease
The finding should prompt comprehensive RV assessment including: RV function parameters (TAPSE, S' velocity, fractional area change), estimation of pulmonary artery pressures, and evaluation for the underlying etiology 1.
Common Pitfall to Avoid:
Do not rely solely on qualitative visual estimation. The guidelines emphasize that quantitative measurements are essential because visual assessment frequently underestimates RV size 1, 3. Your measured value of 46 mm provides objective evidence of enlargement that requires clinical correlation and likely further workup.