Comparison of exponential truncated biphasic versus damped sine wave monophasic shocks in transthoracic cardioversion of atrial fibrillation

Background

Clinical studies have shown the efficacy of the bipha-sic waveform (BW) in reversion of ventricular fibrillation using lower energies. However, the effects of the BW in the treatment of other arrhythmias is unclear. The amount of energy of each shock and the sequency of shocks are to be determined. The purpose of this study is to compare the efficacy and side effects of the BW and the monophasic waveform (MW) in reversion of atrial fibrillation (AF).

Methods

In this prospective, randomized and unicenter trial we submitted 158 patients with AF to transthoracic cardioversion (CV). They were randomized in two groups. Group I, 80 patients underwent BW shocks (average age 55.9 ± 12.6 years old); and Group II, 78 patients underwent MW shocks (average age 59.8 ± 13.0 years old). Group I received sequential shocks of 50, 100, 150, and 175 J (half the energy used in Group II). Group II received sequential shocks of 100, 200, 300 and 360 J. We analyzed the clinical characteristics of both groups before CV (weight, height, AP thoracic diameter, body surface, oxymetry, body temperature, noninvasive blood pressure, duration of AF, ventricular response). Blood samples of cardiac and muscle markers of injury (CK, MB-CK, AST, ALT, DHL) were obtained before, 1 hour and 24 hours after CV.

Results

The first-shock efficacy was similar in both groups (56.3% vs 53.9%, Group I and Group II, respectively) as well the cumulative efficacy of sequential shocks rate (88.0% vs 92.3%, P = 0.415). Baseline characteristics were similar in both groups. Age and baseline cardiac frequency were independent predictors of CV success. Patients in Group II had higher elevations on serum CK (83.0 ± 106.3 vs 178.9 ± 306.9, P = 0.0087). There was a clear relation between CK elevation and cumulated energy used in CV (P = 0.0001). No other injury marker was elevated after CV in both groups.

Conclusions

Biphasic shock with a truncated exponential waveform was equally effective as monophasic damped sine waveform, causing less muscular injury, using only half the energy of the monophasic defibrillator.