From the Guidelines
Squatting decreases right ventricular (RV) afterload by increasing systemic vascular resistance and left ventricular filling, which indirectly affects the right side of the heart. When a person squats, there is an immediate increase in venous return from the lower extremities to the heart, which increases preload to both ventricles. While this initially increases RV workload, the subsequent increase in systemic vascular resistance causes blood to be temporarily pooled in the pulmonary circulation. This pooling effect, combined with improved left ventricular function from increased preload, leads to more efficient emptying of the pulmonary circulation, ultimately reducing pulmonary vascular resistance. The reduced pulmonary vascular resistance translates to decreased RV afterload, as noted in the context of managing hemodynamics in patients with acute respiratory distress syndrome (ARDS), where mechanical ventilation and underlying lung pathology can increase RV afterload 1. Key factors to consider in this context include:
- Increased venous return and systemic vascular resistance during squatting
- Temporary pooling of blood in the pulmonary circulation
- Improved left ventricular function and reduced pulmonary vascular resistance
- Decreased RV afterload as a result of these physiological changes. In clinical practice, understanding the effects of squatting on RV afterload can inform the management of patients with certain cardiac conditions, such as hypertrophic cardiomyopathy, where optimizing loading conditions can improve cardiac output 1.
From the Research
Effect of Squatting on Right Ventricle (RV) Afterload
- The effect of squatting on RV afterload is not directly addressed in the provided studies 2, 3, 4, 5, 6.
- However, study 3 examines the hemodynamic responses to squatting in normal individuals and heart transplantation recipients, and finds that squatting produces a prompt increase in cardiac output and arterial blood pressure, which could potentially affect RV afterload.
- Study 4 discusses the concept of afterload in the context of left-sided heart failure, and notes that afterload is most often modeled to consist of three components: pulmonary vascular resistance (PVR), pulmonary arterial compliance (PAC), and characteristic impedance 4.
- Studies 5 and 6 discuss the importance of RV function in patients with pulmonary hypertension, and note that RV contractility must increase to maintain cardiac output in response to pressure overload 5, 6.
- However, none of the studies provide a direct answer to the question of how squatting affects RV afterload, and further research would be needed to fully understand this relationship 2, 3, 4, 5, 6.
Key Findings Related to RV Afterload
- Increased RV afterload can result in increased RV volumes and secondary alteration in left ventricular diastolic mechanics 2.
- Therapy designed to reduce pulmonary vascular resistance (PVR) may be appropriate to increase flow in the setting of increased RV afterload 2.
- RV contractility must increase to maintain cardiac output in response to pressure overload 5, 6.
- The balance between the degree of RV contractility and afterload determines stroke volume 6.