[Electrocardiogram in the differential diagnosis of wide-QRS tachycardias].

The surface ECG constitutes an invaluable tool for the differential diagnosis in those cases in which the QRS complex exceeds the normal duration (120 mseg or more) and a heart rate of 100 bpm or more. Most of the arrhythmias with wide QRS complexes are ventricular in origin, and frequently related to heart disease; nevertheless, in those patients with hemodynamic stability it is frequently misdiagnosed as supraventricular tachycardia. The importance of the surface ECG resides in the fact that the correct diagnosis can be done with high probability when the analysis is orderly made. To be able to perform such an analysis it is necessary to count upon a good quality ECG, besides it is very important if, in addition, a transesophageal record is available to establish the precise relation between the "p" wave and the ventricular activation. There are the traditional morphologic criteria, with their limited usefulness, but the observations of Brugada et al. increased the sensitivity, which can reach up to 98% with a high degree of specificity (96%). The clinical data plus an adequate ECG analysis can lead to the differential diagnosis with a high grade of certainty.