Serum cardiac markers response to biphasic compared with monophasic electrical cardioversion

Introduction

Defibrilation or cardioversion in critically ill cardiac patients may be followed by serum cardiac marker elevation. However, only few studies with limited patient samples assessing electrical myocardial injury have been published [1, 2]. The aim of our study was to evaluate the response of serum cardiac markers following elective cardioversion for supraventricular tachyarrhyth-mias (SVT) and to analyze the impact of type of shock waveform.

Methods

Eighty-three patients with various SVTs indicated for elective cardioversion were randomized to monophasic or biphasic electrical cardioversion (CV). Serum levels of creatine kinase (CK), MB fraction of CK (CK-MB), myoglobin (Mg) and troponin I (TnI) were analyzed before CV and 262 ± 69 min after the procedure.

Results

Average age was 66.3 ± 11.2 years, 43 patients underwent biphasic and 40 monophasic CV. The most frequent type of arrhythmia was atrial fibrilation (63%). Mean cumulative energy (CE) was 301 ± 260 J. Delivered CE > 150 J was associated with significant elevation of CK and Mg levels after CV (0.96 μmol/l and 166 μg/l, respectively), while CE < 150 was not (P < 0.01). Baseline values of TnI were negative in all patients. No significant changes in CK-MB and TnI levels after CV were identified. Strong correlation between increase of CK and Mg levels and CE was observed. Multivariate logistic regression analysis identified only cumulative energy > 150 J as an independent positive predictor for CK and Mg elevation. Randomization to the biphasic or monopha-sic waveform group was not associated with significant differences in serum cardiac marker elevation and with the success rate in sinus rhythm restoration (88.37% vs 87.18%, respectively; P = 0.8692). However, a trend to lower CE necessary for sinus rhythm restoration was detected for biphasic wave shock (259 vs 347, P = 0.1237).

Conclusion

According to our study, elective electrical cardioversion for SVTs is not associated with biochemical signs of myocardial injury. Application of cumulative energy > 150 J can be followed by CK and Mg elevation most likely due to skeletal muscle damage. This pattern is not dependent on the type of the shock waveform.