Efficacy of esmolol cardioplegia during hypothermic ischaemia

Abstract

Cardioplegic arrest using a polarizing solution has been shown to have beneficial advantages for cardioprotection compared with depolarizing (potassium-based) arrest; most studies, however, have looked at normothermic ischaemia with short infusion intervals (every 10-15 min). This study examines the protective efficacy of an esmolol-based cardioplegia during hypothermic arrest, together with a prolonged infusion interval (30 min) for increased clinical feasibility. Isolated Langendorff-perfused hearts were subjected to arrest with St Thomas' Hospital cardioplegia (STH2), or esmolol cardioplegia (single- or multidose infusion at 32°C) for 60-min, 90-min or 120-min global ischaemia at 32°C, and recovery of function (left ventricular developed pressure) measured. A further study examined the protective efficacy of multidose esmolol cardioplegia compared with hypothermia alone at temperatures of 20°C, 28°C and 32°C compared with 37°C for 120 min of ischaemia. Esmolol cardioplegic arrest with multidose infusion at 32°C significantly improved recovery of function (left ventricular developed pressure) compared with 32°C STH2, at each ischaemic duration (88 ± 3 vs 66 ± 3% at 60 min, 82 ± 3 vs 51 ± 3% at 90 min and 73 ± 6 vs 49 ± 4% at 120 min; P < 0.05). At various hypothermic temperatures, esmolol cardioplegia significantly improved protection compared with hypothermia alone (88 ± 4%, 88 ± 3% and 72 ± 3% vs 60 ± 3%, 30 ± 2% and 15 ± 1% at 20°C, 28°C and 32°C, respectively; P < 0.05); however, at 37°C, there was no difference in protection. Contracture during ischaemia mirrored the effects of left ventricular developed pressure recovery. Esmolol cardioplegia (a polarizing solution), used as a multidose infusion during hypothermia, significantly improved cardioprotection compared with the depolarizing STH2. An increased infusion interval of 30 min indicates improved clinical feasibility.