[T-wave changes in intermittent left bundle branch block. Pathogenesis and clinical significance].

In patients with intermittent left bundle branch block (LBBB) it is common to observe T wave abnormalities in the right precordial leads during normally conducted beats. These changes have usually been interpreted as a result of anteroseptal ischemia. More recently it has been suggested that they may be the consequence of an electric phenomena secondary to the abnormal ventricular activation. However, the "benign" character of these abnormalities has never been confirmed by clinical studies. We have studied a group of 10 pts (3 males and 7 females), aging between 23 and 66 years (mean 41 +/- 8) with atypical precordial pain admitted to our institution, because of intermittent LBBB and T wave inversion in the right precordial leads during the normally conducted beats. All patients had normal left ventriculography and coronary angiograms. During the follow-up period (20 to 102 months, mean 4.7 years) they were subjected to serial clinical examinations, 24 hours ECG Holter monitoring echocardiogram and exercise thallium 201 scintigraphy. Within this period of observation, no patient developed symptoms or signs of cardiac involvement while all but three developed a stable LBBB (these three patients have been followed only for a limited period of time). Exercise thallium 201 scintigraphy showed in 4 patients a reversible septal perfusion defect during LBBB. We conclude that T wave abnormalities observed in the normally conducted beats in patients affected by intermittent LBBB have a favourable prognostic significance.(ABSTRACT TRUNCATED AT 250 WORDS)