Key result
Normothermic CABG with IAWBC preserved systolic function, increased diastolic stiffness (P=0.018), and improved systolic and diastolic chronotropic responses.
Why the study?
Does normothermic CPB with IAWBC preserve left ventricular function and chronotropic responses in patients undergoing CABG?
Observational (n=10)
Does normothermic CPB with IAWBC preserve left ventricular function and chronotropic responses in patients undergoing CABG?
Normothermic CABG with intermittent antegrade warm blood cardioplegia preserves systolic function and improves chronotropic responses, likely reflecting relief of ischemia.
May support normothermic CABG with IAWBC in select patients; hypothesis-generating and leaves open need for RCTs.
OBJECTIVE: Recent studies indicate that normothermic cardiopulmonary bypass (CPB) with intermittent antegrade warm blood cardioplegia (IAWBC) may have metabolic and clinical advantages, but limited data exist on its effects on myocardial function. Therefore, we investigated the acute effects of this approach on systolic and diastolic left ventricular function and on chronotropic responses. METHODS: In 10 patients undergoing isolated CABG we obtained on-line left ventricular pressure-volume loops using the conductance catheter before and after normothermic CPB with IAWBC. Steady state and load-independent indices of left ventricular function derived from pressure-volume relations were obtained during right atrial pacing (80-100-120 beats/min) to determine baseline systolic and diastolic function and chronotropic responses. RESULTS: The mean time of CPB was 105+/-36 min (median 103, range 60-167 min) with a mean aortic cross-clamp time of 75+/-27 min (median 69, range 43-129 min). Baseline (80 beats/min) end-systolic elastance (E(ES)) did not change after CPB (1.22+/-0.53 to 1.12+/-0.28 mm Hg/ml, P>0.2), while the diastolic chamber stiffness constant (k(ED)) significantly increased (0.014+/-0.005 to 0.040+/-0.007 ml-1, P=0.018) and relaxation time constant (tau) significantly decreased (61+/-3 to 49+/-2 ms, P=0.004). Before CPB, incremental atrial pacing had no significant effects on E(ES) and tau but significant negative effects on kED (0.014+/-0.005 to 0.045+/-0.012 ml-1, P=0.013). After CPB, atrial pacing had significant positive effects on E(ES), tau and kED (E(ES): 1.12+/-0.28 to 2.60+/-1.54 mm Hg/ml, P=0.021; tau: 49+/-2 to 45+/-2 ms, P=0.009; kED: 0.040+/-0.007 to 0.026+/-0.005 mm Hg, P=0.010), indicating improved systolic and diastolic chronotropic responses. CONCLUSION: On-pump normothermic CABG with IAWBC preserved systolic function, increased diastolic stiffness, and improved systolic and diastolic chronotropic responses. Normalization of the chronotropic responses post-CPB is likely due to effects of successful revascularization and subsequent relief of ischemia.
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Tulner et al. (2005) conducted an observational in Coronary artery disease requiring CABG (n=10). Normothermic cardiopulmonary bypass with intermittent antegrade warm blood cardioplegia vs. Baseline (before CPB) was evaluated on Systolic and diastolic left ventricular function and chronotropic responses. Normothermic CABG with IAWBC preserved systolic function, increased diastolic stiffness (P=0.018), and improved systolic and diastolic chronotropic responses.
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