Serum troponins T and I after elective cardioversion

Aims: To describe the pattern of release of five myocardial proteins after elective cardioversion.

Methods and results: We measured serum levels of the myocardial proteins creatine kinase, creatine kinase MB mass, myoglobin, troponin T and troponin I serially from baseline to 24 h after 72 elective cardioversion attempts. The total energy used for attempted cardioversion was 408+/-318 J (range 50 to 1280 J). Maximal creatine kinase levels (median 232 IU x l(-1), interquartile range 91 to 1152 IU x l(-1)) occurred at 24 h and correlated with the total energy delivered (r=0.75, P<0.0001). The peak creatine kinase MB mass levels exceeded the discrimination level for myocardial injury (>/=5 microg x l(-1)) in seven patients (10%). The peak myoglobin levels were elevated (>85 microg x l(-1)) in 40 patients (56%) and correlated with the peak creatine kinase levels (r=0.83, P<0.0001). Troponin T reached the discrimination level (0.10 microg x l(-1)) in one patient with a serum creatinine level of 0.16 mmol x l(-1)and severe left ventricular impairment. Twelve patients had baseline troponin I levels above our prespecified discrimination level of 0.4 microg x l(-1)(range 0.4 to 3.1 microg x l(-1)), which did not increase after cardioversion. In two patients the levels rose from <0.4 microg x l(-1) to 0.5 microg x l(-1) and 0.6 microg x l(-1) respectively.

Conclusions: Troponin T levels do not rise after elective cardioversion. The minor increases in troponin I may reflect our choice of discrimination level. Cardiac troponins are useful in determining whether arrhythmias requiring emergency cardioversion are primary or secondary to myocardial infarction.