Radionuclide Assessment of Left Ventricular Function in Patients Requiring Intraoperative Balloon Pump Assistance

Abstract

Twenty-three surviving patients who were weaned from cardiopulmonary bypass with intraaortic balloon pump assistance returned for follow-up radionuclide left ventricular (LV) function and thallium 201 perfusion studies at a mean of 23 ± 3 months following operation. It was found that despite profound intraoperative myocardial depression requiring intraaortic balloon assistance, 13 patients had no change (within 10%) in the resting LV ejection fraction compared with the preoperative measurement. Among all 23 patients, there was no difference between mean (± standard error of the mean) preoperative and postoperative resting LV ejection fraction (48 ± 4 vs 46 ± 4%, p = not significant [NS]). Only 11 patients had perioperative myocardial infarction documented by new Q waves in the electrocardiogram, by elevation of creatine kinase–MB fraction, or by defects on thallium 201 imaging not explained by documented myocardial infarction before operation. Overall, postoperative resting LV ejection fraction was not different from the preoperative value in patients with perioperative myocardial infarction (44 ± 7 vs 47 ± 5%, p = NS). Postoperative resting LV ejection fraction rose by ≥ 10% compared with preoperative values in 4 patients (3 with aortic valve replacement), remained within the 10% limit in 9 patients, and fell by ≥ 10% in 10 patients (7 with perioperative myocardial infarction). Only 4 out of 16 patients studied at follow-up with exercise radionuclide studies demonstrated a normal LV response to exercise (≥ 5% increase in LV ejection fraction). Thus, among survivors requiring intraaortic balloon pump assistance for weaning from cardiopulmonary bypass, LV performance at rest is frequently preserved. In addition, 11 of the 23 patients had evidence of perioperative myocardial infarction, indicating a component of reversible intraoperative LV dysfunction.