Right ventricular distension and left ventricular compliance

Area of Science:

• Cardiovascular Physiology
• Cardiac Mechanics
• Ventricular Interaction

Background:

• The interaction between the right ventricle (RV) and left ventricle (LV) influences overall cardiac function.
• Understanding RV constraint on LV diastolic properties is crucial for diagnosing and managing cardiac conditions.

Purpose of the Study:

• To investigate the effect of right ventricular (RV) distension on the end-diastolic pressure-volume (PV) relationship of the nonischemic and ischemic left ventricle (LV).
• To examine the impact of RV constraint on LV diastolic function during experimentally induced ischemia.

Main Methods:

• Utilized an isovolumic beating LV model with a separately perfused, ejecting RV under controlled distension.
• Assessed changes in the LV PV relationship with varying levels of RV distension (mild to severe).
• Induced myocardial ischemia by reducing left main coronary artery flow and evaluated RV distension effects on the ischemic LV PV relationship.

Main Results:

• Increased RV distension (from 1.5 to 16 mmHg RVEDP) caused a significant leftward shift in the nonischemic LV PV relationship.
• During 90 minutes of ischemia, both mild and moderate RV distension led to a progressive leftward shift in the LV PV relationship.
• Impaired ventricular relaxation (prolonged time constant T) was observed during ischemia but did not fully account for the observed PV relationship shifts.

Conclusions:

• Right ventricular constraint significantly impacts left ventricular diastolic function, shifting the PV relationship.
• The observed changes in LV PV relationship during ischemia are not solely explained by impaired relaxation or external RV constraint.
• The time course of LV PV relationship changes during ischemia in this model differs from human pacing-induced ischemia, suggesting complex underlying mechanisms.