Usefulness of superficial electrocardiogram to diagnose narrow QRS tachycardias: Correlation with intracavitary electrograms

Introduction and objectives. The electrocardiogram is an important tool to diagnose tachycardias. The sequence of analysis of the superficial electroc ardiogram was evaluated for the diagnosis of supraventricular tachycardias with narrow QRS complexes (less than or equal to 110 ms) establishing corre lation with intracavitary electrograms. Patients and methods. Between November 1996-October 1998, 674 electrophysio logical studies were revised. 173 cases were selected, during which suprave ntricular tachycardias were inducted. In each study, the superficial electr ocardiographic leads were correlated with the intracavitary electrograms du ring 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 atriove ntricular and ventriculoatrial intervals were stablished with the P-R' and R-P intervals, respectively, in the electrocardiogram. Results. 107 patients were female. Upon locating the P waves in the electro cardiogram, in each supraventricular tachycardia we observed: a) P waves co incided 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 d) P waves over T waves: 3 orthodromic atrioventricular reentries, and 1 nodal reentry. Conclusions. The sequence of analysis locating the P waves in the superfici al electrocardiogram is an useful, rapid method, with adequate sensitivity or specificity, in the evaluation of the mechanisms that sustain more commo n supraventricular tachycardias, permiting the performance of differential diagnosis between some of them.