Intrinsic mechanisms of right ventricular autoregulation

Area of Science:

• Cardiovascular Physiology
• Cardiac Autoregulation
• Ventricular Adaptation

Background:

• The right ventricle's response to acute and sustained afterload elevation is not fully understood.
• Intrinsic cardiac mechanisms may play a role in right ventricular adaptation to increased workload.
• Understanding these mechanisms is crucial for managing conditions with elevated pulmonary pressure.

Purpose of the Study:

• To elucidate the adaptive mechanisms of the right ventricle during acute and sustained afterload elevation.
• To differentiate the roles of the Frank-Starling mechanism, shortening deactivation, and the Anrep effect in right ventricular adaptation.
• To investigate the impact of afterload increases on right ventricular pressure-volume loops and contractility.

Main Methods:

• A porcine model (12 pigs) was used to simulate acute and intermittently sustained afterload elevation.
• Preload reduction was induced via inferior vena cava occlusion.
• Right ventricular pressure-volume loops were monitored using a conductance catheter to assess ventricular function and contractility.

Main Results:

• The end-systolic pressure-volume relationship (ESPVR) showed a biphasic response during afterload elevation, indicating distinct phases of adaptation.
• Shortening deactivation (SDA) was implicated in the initial phase, followed by mechanisms resembling preload intervention in the second phase.
• A persistent increase in afterload led to increased ESPVR and preload recruitable stroke work (PRSW) slopes, with a decreased filling state, indicating a significant Anrep effect that prevents ventricular dilation.

Conclusions:

• This study demonstrates the successive activation of intrinsic cardiac autoregulation mechanisms—SDA, Frank-Starling mechanism, and Anrep effect—in the right ventricle during load adaptation.
• The Anrep effect plays a critical role in preventing right ventricular dilation under sustained afterload stress.
• These findings highlight the complex interplay of autoregulatory mechanisms in maintaining right ventricular function under increased workload.