Cardiac cycle efficiency: a new index for cardiac work estimation tested during aortic valve plasty

Introduction

The pressure recording analytical method (PRAM) is the only pulse contour method that does not need any calibration since it estimates in vivo, beat to beat, the impedance of the cardiovascular system [1–3]. Cardiac cycle efficiency (CCE) is a novel parameter that is directly related to the cardiovascular impedance. Since the aortic valve contributes to impedance, we hypothesized during an aortic valvuloplasty, performed for severe aortic stenosis, the cardiovascular impedance may decrease by the reduction of the transvalvular gradient.

Methods

In a cath lab, five consecutive patients undergoing aortic valve plasty for severe aortic stenosis were monitored by means of PRAM during the procedure. Systolic (SAP), diastolic, and mean (MAP) arterial pressures, stroke volume (SV), heart rate (HR), cardiac output (SV × HR), CCE, and dP/dt_max were continuously collected and afterwards analyzed. The stroke work (SW = SV × MAP) and minute work (MW = SBP × CO) were also measured.

Results

After the ballooning maneuver (valvuloplasty), the maximal gradient measured with intraventricular and intraaortic catheters significantly decreased (146 (37) vs 43 (12) mmHg; P < 0.0001). The CCE significantly improved from -0.72 (0.4) to 0.02 (0.19) U; P < 0.0001. Peripheral dP/dt_max increased from 0.8 (0.27) to 1.16 (0.23) mmHg/ms; P = 0.001, while SW and MW did not show substantial modifications (4.06 (1.03) vs 4.02 (1.4) l × mmHg; NS, and 549.8 (111.5) vs 544.6 (153.4) l × mmHg; NS, respectively)

Conclusions

CCE demonstrated to be a very sensitive estimation of cardiovascular impedance since it shows a significant improvement after the valvuloplasty in spite of unchanged values of both SW and MW. In other words, the energy expenditure of the whole cardiovascular system significantly reduced after the aortic valve stenosis is corrected. Moreover, our data strongly suggest that peripheral dP/dt_max is deeply affected by aortic valve stenosis.