Evaluation of transthoracic countershock with initial energy levels up to 200 J in a coronary care unit.

In a five year prospective study, transthoracic countershock of patients in the coronary care unit was evaluated with respect to efficacy, transthoracic resistance and arrhythmias. Those patients dying within 12 hours of the recorded event are referred to as agonal patients. Atrial arrhythmias were generally first treated with quinidine or disopyramide and/or a digitalis preparation. Patients with coronary heart disease were treated with lidocaine, disopyramide, or verapamil when there was time for appropriate diagnosis. The efficacy of the first shock with an energy level between 50 J and 200 J in non-agonal patients was: for atrial fibrillation, 44% (N = 34), and between 83% and 93% for tachycardias and ventricular fibrillation. The cumulative efficacy of two shocks with energy levels between 50 J and 200 J was: in atrial fibrillation 53% and others between 90% and 96%. In agonal patients with ventricular fibrillation and acute myocardial infarction the efficacy of one shock of 100-150 J was 39% and two shocks of 100-200 J, 69% (N = 13). No correlation was found between the transthoracic resistance and parameters such as body-weight, length or thorax-circumference, indicating that these should not be taken into account in the choice of the energy level for countershock. In non-agonal patients without coronary heart disease arrhythmias due to countershock increased in duration when the energy of the countershock increased (p less than 0.01, N = 39). It is concluded that the initial stored energy for defibrillation and cardioversion of nonagonal patients in a coronary care unit may be limited to 200 J (160 J delivered energy), even with atrial fibrillation after drug therapy in which case an initial energy level of 200 J seems more appropriate.