Left-to-Right Ventricle Ratio in Cardiac Health
Clinical Significance
An abnormal left-to-right ventricular volume ratio (LRVR) is a powerful independent predictor of heart failure, atrial fibrillation, and mortality, even when individual chamber volumes fall within normal ranges. 1
The LRVR is calculated as the ratio of left ventricular end-diastolic volume index to right ventricular end-diastolic volume index (LVEDVi/RVEDVi), with cardiac MRI providing the gold standard measurement. 2 Echocardiography offers a practical alternative using chamber dimensions or areas from the apical four-chamber view. 2
Normal Reference Values and Thresholds
A balanced LRVR ranges from 0.8 to 1.3, with values outside this range conferring significantly increased cardiovascular risk. 1
High LRVR (>1.3) indicates disproportionate left ventricular enlargement relative to the right ventricle and is associated with:
Low LRVR (<0.8) suggests relative right ventricular enlargement and carries similar prognostic implications in certain populations 1
In heart failure with preserved ejection fraction (HFpEF), an LRVR <1.0 or ≥1.4 predicts worse outcomes, with hazard ratios exceeding 5.0 for cardiovascular death or heart failure hospitalization 3
Disease-Specific Applications
Arrhythmogenic Cardiomyopathy
An RV inflow/LV end-diastolic dimension ratio >0.9 on echocardiography suggests pathologic RV enlargement. 2 A ratio of RV end-diastolic volume to LV end-diastolic volume >1.2 on cardiac MRI supports the diagnosis of arrhythmogenic cardiomyopathy over physiologic athletic adaptation. 2
Congenital Heart Disease
In pediatric populations with septal defects, the LRVR provides more reliable assessment of shunt severity than defect size measurements alone. 2 An LV-to-RV end-diastolic area ratio ≥1.3 in four-chamber view predicts the need for intervention in suspected coarctation of the aorta with high accuracy (AUC 0.97). 2
In fetal echocardiography, left-to-right ventricular size discrepancy with disproportionately smaller left ventricle identifies fetuses requiring neonatal intervention for critical arch obstruction, with aortic arch measurement ≤3 mm being the most sensitive predictor. 4
Heart Failure Assessment
The LRVR provides prognostic information independent of left ventricular ejection fraction across the spectrum of heart failure. 5 In HFpEF specifically, LRVR values <1.0 or ≥1.4 remain predictive of adverse outcomes even in patients without dilation of either ventricle. 3
Right ventricular dysfunction reflects the inability of the RV to support optimal circulation in the presence of adequate preload, and assessment of RV dimensions and function is mandatory when evaluating heart failure. 5
Measurement Methodology
Cardiac MRI (Gold Standard)
Normal reference ranges for adults aged 20-80 years: 5
- LV end-diastolic volume index: 56-96 mL/m² (women), with values >116 mL/m² considered severely abnormal
- RV end-diastolic volume index: 48-112 mL/m² (women, ages 20-68), with values >144 mL/m² considered severely abnormal
Papillary muscles should be included in LV mass and excluded from volumes, while RV papillary muscles should be included in RV volume. 5
Echocardiography
Standard American Society of Echocardiography criteria for chamber sizes are applicable in most adult patients, particularly those with simple or moderately complex disease. 5 However, 2D measurements alone should be avoided for complex geometries where 3D assessment is superior. 2
For the RV, linear or area measures from multiple views using anatomic landmarks (RV base in four-chamber view, RVOT in short-axis) provide more reproducible measurements than single-view assessments. 5 Measures of longitudinal RV function such as tricuspid annular plane systolic excursion (TAPSE) and RV free wall velocity by tissue Doppler are more accurate than visual assessment. 5
Critical Pitfalls to Avoid
Fixed cutoff values should not be applied in children without considering body size and relation to other cardiac structures. 2 All measurements must be indexed to body surface area in cardiomyopathy evaluations to prevent misdiagnosis. 2
In athletes, RV dimensions alone are insufficient—functional measures and regional wall motion must be assessed concurrently to distinguish physiologic adaptation from pathology. 2
TAPSE and systolic velocity measurements are less accurate in patients with severe tricuspid regurgitation and may not reflect true RV myocardial function. 5 Less load-dependent parameters such as 2D longitudinal strain may be more useful in this setting. 5
Ventricular shape, interventricular septal motion, conduction abnormalities, surgical scars, and RV pacing can all complicate interpretation of wall motion abnormalities and chamber ratios. 5
In septic shock and severe sepsis, an increased RV/LV ratio (≥0.9) does not predict mortality, highlighting the importance of clinical context when interpreting chamber ratios. 6
Integration with Other Cardiac Parameters
Assessment of the LRVR should be integrated with evaluation of atrial volumes, ventricular function, valvular disease, and hemodynamic parameters. 5
The left atrium and right ventricle serve as supporting chambers to the failing left ventricle, with LA enlargement accommodating rises in filling pressures that can transfer to the RV via pulmonary circulation. 7 The left-to-right atrial volume ratio (LARA) provides complementary prognostic information, with high LARA (>2) predicting heart failure and atrial fibrillation, particularly in patients with LRVR <1.3. 1
Right atrial dilation indicates elevation of right atrial or RV end-diastolic pressure or chronic volume overload. 5 Evaluation of RV dimensions and function, RA volume, inferior vena cava diameter, and pulmonary arterial systolic pressure is mandatory when tricuspid regurgitation is more than mild. 5