Usefulness of superficial electrocardiogram in the diagnosis of narrow QRS tachycardias: correlation with intracavitary electrocardiograms

INTRODUCTION AND OBJECTIVES: The electrocardiogram is an important tool to diagnose tachycardias. The sequence of analysis of the superficial electrocardiogram was evaluated for the diagnosis of supraventricular tachycardias with narrow QRS complexes (<= 110 ms) establishing correlation with intracavitary electrograms. PATIENTS AND METHODS: Between November 1996-October 1998, 674 electrophysiological studies were revised. 173 cases were selected, during which supraventricular tachycardias were inducted. In each study, the superficial electrocardiographic leads were correlated with the intracavitary electrograms during tachyarrhythmias. The P waves were located with respect to the R waves, the R-T or T-R' intervals, and the T waves, and relations between atrioventricular and ventriculoatrial intervals were established with the P-R' and R-P intervals, respectively, in the electrocardiogram. RESULTS: 107 patients were female. Upon locating the P waves in the electrocardiogram, in each supraventricular tachycardia we observed: a) P waves coincided with the R waves: 30 typical nodal reentries; b) P waves between R and T waves: 95 orthodromic atrioventricular reentries, 27 nodal reentries, 1 atrial tachycardia; c) P waves between T and R' waves: 4 nodal reentries, 5 orthodromic atrioventricular reentries, 7 atrial tachycardias, and