Hemodynamic tracing during LV distention due to aortic regurgitation during CPB

These traces were recorded from a patient with severe regurgitation of a porcine aortic valve prosthesis. In contrast to the hemodynamic pattern normally seen during initiation of cardiopulmonary bypass, the arterial blood pressure (ART) trace remains pulsatile while the patient is in sinus rhythm, despite the fact that good venous drainage to the pump has been achieved, as indicated by the pulmonary artery pressure (PAP) and central venous pressure (CVP) traces, which approach 0 mmHg (left panel). This hemodynamic pattern is seen typically in patients with significant aortic valve regurgitation and reflects the continued left ventricular filling through the incompetent aortic valve and its subsequent ejection with each heartbeat. A serious problem arises when this situation is not recognized, and the heart stops beating, either in asystole or in ventricular fibrillation (middle panel). Aortic regurgitation continues, but the fibrillating left ventricle no longer ejects the regurgitant volume, and left ventricular distention results. This pattern is recognized by the progressive rise in PAP caused by back-filling of the left ventricle from the aorta. Note that PAP can rise to equal systemic pressure, as shown here where PAP (24 mmHg) and ART (27 mmHg) are nearly identical (middle panel). Under these circumstances, the coronary perfusion pressure gradient, estimated as ART – PAP, approaches 0 mmHg, and severe myocardial ischemia will occur if corrective action is not taken. Left ventricular venting will relieve left ventricular distention and restore a pressure gradient for coronary perfusion (right panel). This hemodynamic pattern now resembles the normal one during cardiopulmonary bypass, where the ART trace is nonpulsatile and the CVP and PAP are approximately 0 mmHg. Note that effective venting ameliorates left ventricular distention but does not guarantee adequate systemic blood flow in patients with severe aortic valve regurgitation.