Cardiac cycle efficiency correlates with pro-B-type natriuretic peptide in cardiac surgery patients

Introduction

Cardiac cycle efficiency (CCE) can be calculated by the pressure recording analytical method (PRAM), a less invasive pulse-contour system that can provide beat-to-beat monitoring of cardiac output (CO). CCE is an innovative parameter that ranges from -1 to +1, with -1 being the worse and +1 the best possible efficiency of the cardiac cycle (that is, better ventricular–arterial coupling). Pro-BNP-type natriuretic peptide (pro-BNP) is predominantly secreted from the cardiac ventricles in response to increases in ventricular wall stress (VWS). Pro-BNP has been shown to correlate with myocardial hypertrophy and dysfunction [1]. We studied the feasibility of the CCE by PRAM when compared with pro-BNP to monitor the VWS and myocardial impairment and recovery in cardiac surgery.

Methods

Ten patients with myocardial hypertrophy undergoing aortic valve replacement were studied. Plasma pro-BNP concentrations were obtained 15 minutes after the induction of anesthesia (t0), 15 minutes after myocardial reperfusion (t1), and 24 hours after surgery (t2). CCE measurements were acquired at the same times and correlations with pro-BNP levels were assessed.

Results

CCE values ranged from -0.38 to +0.44. CCE decreased from 18% to 42% at t1 with respect to t0 (P < 0.05). Also, at t1 a decrease of CO from 10% to 25% with respect to t0 was observed (P < 0.05). The t2 and t0 intervals showed similar values for CCE (+0.37 ± 0.08 vs +0.35 ± 0.11) and CO (5.0 ± 0.9 vs 4.8 ± 1.1 l/min). Pro-BNP was 1,270 ± 1,560 pg/ml at t0, increased moderately at t1, and peaked significantly at t2 (2,839 ± 873 pg/ml; P < 0.001). Overall, a negative correlation between CCE and pro-BNP values was found (r = -0.89, P < 0.01). At each time of the study, correlations between CCE and pro-BNP were -0.91, -0.83, and -0.88 (t0, t1, and t2, respectively; P < 0.01).

Conclusion

This study demonstrated an inverse correlation between CCE and pro-BNP values. The feasibility of PRAM to assess VWS, myocardial impairment and recovery during various phases of surgery sounds good. This new pulse-contour system seems a valuable tool that, together with pro-BNP measurements, may provide new insights into cardiac and hemodynamic assessment of patients scheduled for cardiac surgery.