How does increased left ventricular (LV) workload improve right ventricular (RV) systolic function?

From the Guidelines

Increasing left ventricular (LV) work improves right ventricular (RV) systolic function primarily through ventricular interdependence mechanisms, as evidenced by the most recent and highest quality study from 2018 1. When LV contractility increases, the shared interventricular septum shifts toward the LV, creating more favorable geometry for RV contraction. This mechanical coupling allows the RV to generate higher pressures with less myocardial work. Additionally, improved LV function enhances cardiac output, which reduces pulmonary vascular resistance and RV afterload, further supporting RV performance. Some key points to consider in this context include:

• Ventricular interdependence in right-sided heart failure, where pathological increases in RV filling pressures are transmitted to the interventricular septum, altering LV geometry and contributing to reduced cardiac output 1.
• The importance of considering RV volume overload, dilated RV, and compressed LV, as well as increased pericardial constraint in the pathophysiology of right-sided heart failure 1. Clinically, this principle is applied when using inotropes like dobutamine or milrinone to support both ventricles in heart failure. Vasopressors such as norepinephrine can also help by increasing LV afterload and shifting the septum, improving RV function. This relationship explains why treating left-sided heart failure often results in improvement of right-sided heart failure symptoms, as the interventricular dependence means that strengthening one ventricle positively affects the other. It is also worth noting that RV failure can result in reduced LV preload, whereas the increase in RV-end-diastolic pressure reverses the diastolic trans-septal pressure gradient, resulting in diastolic ventricular interdependence and decreased LV end-diastolic volume, further constrained by the increased pericardial pressure, as described in earlier studies 1. However, the most recent and highest quality evidence from 2018 1 takes precedence in guiding clinical decision-making. Key considerations in clinical practice include:
• Using inotropes and vasopressors to support both ventricles in heart failure
• Monitoring for signs of RV volume overload and increased pericardial constraint
• Optimizing LV function to enhance cardiac output and reduce pulmonary vascular resistance.

From the Research

Mechanisms of Improved RV Systolic Function

• Increasing left ventricular work can improve right ventricular (RV) systolic function through ventricular interdependence, as suggested by studies 2, 3, 4.
• The left ventricle contributes significantly to RV systolic function, with experimental studies indicating that 20-40% of RV systolic pressure and volume outflow result from left ventricular contraction 3, 4.
• The mechanism of ventricular interdependence is not solely explained by the septum and its position, but rather by the balance of forces at the interventricular sulcus, material properties, and cardiac dimensions 4.

Clinical Implications

• In patients with postcardiotomy low cardiac output syndromes, RV failure can develop in approximately 25% of patients receiving left ventricular assist device support, highlighting the importance of considering ventricular interdependence in clinical practice 2.
• The use of non-invasive methods, such as right ventricular myocardial work, can provide valuable insights into RV function and its relationship with left ventricular function 5.
• Optimization of guideline-directed medical therapy, including the use of beta-blockers, can improve survival in patients with advanced heart failure 6.

Key Findings

• Studies have consistently shown that left ventricular function has a significant impact on RV systolic function, with the left ventricle contributing to RV systolic pressure and volume outflow 2, 3, 4.
• The relationship between left ventricular and RV function is complex and influenced by various factors, including ventricular interdependence, cardiac dimensions, and material properties 4.
• Further research is needed to fully understand the mechanisms underlying the improvement in RV systolic function with increased left ventricular work and to explore the clinical implications of these findings 2, 5, 3, 4.