Value of preexisting @entity5036 in the electrocardiographic differentiation of supraventricular from ventricular origin of wide QRS XXXX .

@entity1 @entity1165 @entity714 @entity591 @entity5036 @entity4710 @entity943
The relation between the morphologic configuration of QRS complexes during wide QRS @entity591 induced during electrophysiologic studies and sinus rhythm was examined in 18 @entity1 who had preexisting left or @entity714 . Representative QRS complexes during sinus rhythm and during @entity591 were isolated from each @entity1 and juxtaposed for comparison. The QRS complexes that constituted each pair were judged by 4 observers as being identical, different or, if the decision was equivocal, similar. Nine @entity1 had @entity4710 ( @entity4710 ). In 8 of the 9 @entity1 , all 4 observers found the QRS complexes during sinus rhythm and @entity4710 identical in morphologic configuration. In the other @entity1 , 2 observers found the QRS complexes identical and 2 found them similar. In 12 @entity1 @entity1165 ( @entity1165 ) was induced. In 11 of these 12, all 4 observers found the QRS complexes during @entity1165 different from their respective sinus beats. In the other @entity1 , 3 observers found the QRS complexes different, whereas the fourth found them similar. During @entity4710 , the QRS duration was unchanged from the corresponding value during sinus rhythm, whereas in @entity1 with @entity1165 , QRS width increased by a mean of 56 +/- 20 ms (p less than 0.001). The results of our study suggest that the electrocardiographic differentiation of wide QRS @entity591 in @entity1 with preexisting @entity5036 can be accomplished easily and accurately by comparing the QRS complexes during @entity591 with those during sinus rhythm: If the complexes are identical, the @entity591 is supraventricular, but if they are different, the @entity943 is ventricular in origin.
