Retrograde is superior to antegrade continuous warm blood cardioplegia for acute cardiac ischemia.

BACKGROUND

Theoretically, the efficacy of continuous warm blood cardioplegia may be improved when administered retrogradely (RCWBC) rather than antegradely (ACWBC) in the setting of acute regional ischemia because of enhanced oxygen and substrate delivery to myocardial tissue distal to an acute coronary artery occlusion.

METHODS AND RESULTS

Eighteen Yorkshire swine were instrumented for quantification of global left ventricular systolic, diastolic, and regional left anterior descending coronary artery (LAD) zone mechanics before and after 10 minutes of mid-LAD occlusion, followed by 60 minutes of cardiac arrest using continuous warm blood cardioplegia. Initially, 20 ml/kg of 37 degrees C oxygenated blood cardioplegia (hematocrit, 22 +/- 0.6%) was infused antegradely, followed by maintenance of 75 ml/min ACWBC (n = 9) or 60-100 ml/min of RCWBC (n = 9). LAD occlusion was released 20 minutes after cardiac arrest (30 minutes total LAD ischemia), simulating surgical revascularization. Postischemic recovery of global preload recruitable stroke work was nearly complete with RCWBC but significantly depressed with ACWBC (84.9 +/- 9.5% versus 52.4 +/- 5.1%, respectively; p < 0.01). LAD regional stroke work was also well preserved postischemically with RCWBC but showed no functional recovery and systolic bulging after ACWBC (87.4 +/- 13.7% versus -11.36 +/- 7.46% of control values; p < 0.01). Global diastolic stiffness calculated using the beta-coefficient of an exponential end-diastolic pressure-versus-volume relation was unchanged with ACWBC but increased significantly after RCWBC (from 0.027 +/- 0.002 to 0.028 +/- 0.003 mm Hg/ml and from 0.028 +/- 0.003 to 0.036 +/- 0.004 mm Hg/ml, respectively).

CONCLUSIONS

These data suggest that with acute regional ischemia, both global and ischemic zone regional systolic function are depressed by ACWBC, whereas RCWBC affords adequate protection of contractile performance. However, a loss of diastolic compliance may result as a consequence of warm retrograde delivery.