Levi Bassin

Arrhythmogenicity of Hypothermia – A Large Animal Model of Hypothermia

BACKGROUND Therapeutic hypothermia (TH) is used to mitigate cerebral injury after an out of hospital cardiac arrest. There is a perceived risk of increased arrhythmias with temperatures lower than the current target of 32-34°C for TH. This study sought to develop and investigate the electrophysiological changes in a sheep model of systemic hypothermia regarding the susceptibility to ventricular arrhythmias. METHODS Ten sheep underwent systemic hypothermia using a venous-venous extra-corporeal circuit whilst instrumented with a 12 lead ECG. An epicardial sock recorded potentials to 30°C (N=10) or 26°C (N=6). Activation times (AT) and Activation Recovery Intervals (ARI) were calculated using custom software. RESULTS The AT and ARI were significantly prolonged with increased heterogeneity during hypothermia. This effect was most pronounced between normothermia and 34°C during sinus rhythm (SR). For ventricular pacing (VP) however heterogeneity continued to increase with progressive hypothermia. CONCLUSIONS Hypothermia causes a significant increase in the heterogeneity of depolarisation and repolarisation. There is evidence to suggest that SR is protective with most of the increase in heterogeneity occurring with cooling to 34°C. This raises the possibility that the current target temperatures for therapeutic hypothermia may be safely lowered to provide a gain in cerebral protection.

Impending paradoxical embolism: have we lost the clot?

Impending paradoxical embolism is a rare diagnosis that requires urgent treatment. We present a case where surgical thromboembolectomy was undertaken. The thrombus vanished from view on transesophageal ultrasound and was presumed to have undergone embolisation while bypass was established. Unexpectedly, it was found tangled in the superior vena cava cannula apertures.