What is the significance of an altered left to right ventricle ratio in assessing heart health?

Left-to-Right Ventricle Ratio in Heart Health Assessment

An altered left-to-right ventricular volume ratio (LRVR) is a critical marker of cardiac remodeling and prognosis, with values outside the balanced range of 0.8-1.3 (or 1.0-1.3 depending on context) predicting increased risk of heart failure, atrial fibrillation, and mortality, even when individual chamber volumes appear normal.

Clinical Significance and Prognostic Value

The LRVR provides an individualized assessment of ventricular balance that overcomes limitations of traditional single-chamber measurements, which are heavily influenced by body size, sex, and age 1. This ratio-based approach reveals pathologic remodeling that may be missed when evaluating chambers in isolation.

Predictive Value for Adverse Outcomes

In individuals without cardiovascular disease, an elevated LRVR (>1.3) independently predicts:

• Heart failure with a hazard ratio of 2.54 2
• Atrial fibrillation with a hazard ratio of 1.57 2
• All-cause mortality with a hazard ratio of 1.62 2

Critically, these associations persist even when both right and left ventricular volumes fall within normal reference ranges, demonstrating that the imbalance itself carries prognostic significance independent of absolute chamber size 2.

Heart Failure with Preserved Ejection Fraction

In HFpEF populations, LRVR values outside the 1.0-1.3 range identify high-risk patients:

• LRVR <1.0 confers a 5.95-fold increased risk of death or heart failure hospitalization 3
• LRVR ≥1.4 confers a 4.10-fold increased risk of the same composite outcome 3

This U-shaped relationship indicates that both relative right ventricular predominance and left ventricular predominance signal adverse prognosis 3.

Disease-Specific Applications

Valvular Heart Disease

In chronic aortic regurgitation, the LRVR serves as a reliable marker of disease severity and LV remodeling:

• The ratio correlates more strongly with regurgitant fraction (r=0.67) than conventional LV measures 1
• An LRVR ≥1.5 provides balanced sensitivity (71-84%) and specificity (75-77%) for identifying significant AR 1
• An LRVR ≥1.8 rules in significant AR with 91% specificity 1
• The LRVR remains consistent across age and sex subgroups, providing truly individualized assessment 1

Congenital Heart Disease

In pediatric populations, chamber volume ratios guide critical management decisions:

• For septal defects, indirect signs of volume overload (including chamber dimension ratios) are more reliable than defect size measurements alone for assessing shunt severity 4
• An RV inflow/LV end-diastolic dimension ratio >0.9 on echocardiography suggests pathologic RV enlargement in suspected arrhythmogenic cardiomyopathy 4
• 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 4
• An LV-to-RV end-diastolic area ratio ≥1.3 in four-chamber view predicts need for intervention in suspected coarctation of the aorta with high accuracy (AUC 0.97) 4

Right Ventricular Infarction

In the setting of inferior myocardial infarction, RV involvement creates hemodynamic derangements related to altered interventricular dependence and the restraining effect of the pericardium 4. The severity correlates with the extent of RV ischemia and its impact on the shared interventricular septum, leading to reduced LV preload and stroke volume 4.

Measurement Considerations

Imaging Modality Selection

Cardiac MRI provides the gold standard for volumetric assessment, with the LRVR calculated as the ratio of LV end-diastolic volume index to RV end-diastolic volume index 2, 1, 3. Echocardiography offers a practical alternative using chamber dimensions or areas, though 3D echocardiography is preferred for abnormally shaped ventricles 4.

Technical Pitfalls to Avoid

• Do not rely on fixed cutoff values in children without considering body size and relation to other cardiac structures 4
• Avoid using 2D measurements alone for complex geometries where 3D assessment is superior 4
• Index all measurements to body surface area in cardiomyopathy evaluations to prevent misdiagnosis 4
• Recognize that RV dimensions alone are insufficient in athletes; functional measures and regional wall motion must be assessed concurrently 4

Clinical Decision Algorithm

For risk stratification in patients without known cardiovascular disease:

1. Calculate LRVR from end-diastolic volumes
2. Balanced ratio (0.8-1.3): Standard risk assessment
3. High ratio (>1.3): Increased surveillance for heart failure, atrial fibrillation, and mortality risk 2
4. Low ratio (<0.8): Consider right heart pathology, though prognostic significance less established 2

For chronic aortic regurgitation severity assessment:

1. LRVR <1.5: Likely mild-moderate AR
2. LRVR 1.5-1.8: Possible significant AR, correlate with other parameters
3. LRVR ≥1.8: Highly specific for significant AR (≥grade 3 or regurgitant fraction ≥33%) 1

For HFpEF prognostication:

1. LRVR 1.0-1.3: Reference risk category
2. LRVR <1.0 or ≥1.4: High-risk phenotype requiring intensified management 3

Important Caveats

The LRVR does not predict mortality in severe sepsis or septic shock, where acute hemodynamic factors predominate over chronic structural remodeling 5. In acute pulmonary embolism, while RV/LV ratios >0.9 predict mortality, axial and reformatted four-chamber measurements perform equivalently, so the simpler axial approach suffices 6.

For athletes, up to 30-60% may have RV dimensions meeting minor or even major Task Force criteria for arrhythmogenic cardiomyopathy, emphasizing that dimensional criteria must be combined with functional assessment and clinical context 4.