Exercise dependent complete left bundle branch block.

Eleven patients with an exercise dependent complete left bundle branch block (CLBBB) were followed-up over a period of 2-13 years (mean 6.5 +/- 3.8). Their ages ranged from 19 to 62 years (mean 48). Four patients complained of chest pain on effort and one of palpitations. All patients underwent a clinical examination, 12 lead ECG, routine blood tests, chest X-ray, a multistage exercise test, echo Doppler, radionuclide ventriculography with TC99 and 48-h Holter monitoring. Ten were submitted to a coronary angiography with left ventriculography. The ECG at rest displayed a normal ECG in seven patients and an incomplete left bundle branch block (ILBBB) in four patients. The onset heart rate (HR) of CLBBB ranged from 95-146 beats.min-1 (mean 123) and the offset HR75-135 (mean 102 beats.min-1). Coronary angiography showed three-vessel disease in two patients and an obstruction of the left anterior descending coronary artery (LAD) in the third. In the other seven patients all the investigations (including coronary angiography) were normal. During the follow-up period the HR at onset of CLBBB decreased from 145 beats.min-1 to 100 beats.min-1 in four patients but no coronary artery disease (CAD) could be proven at coronary angiography. In our series chest pain did not always signify the presence of CAD. We conclude, that in patients with exercise-dependent CLBBB the prognosis is good if no underlying heart disease can be detected. It appears from our limited experience that an exercise-dependent CLBBB at heart rate below 125 beats.min-1 does not by itself constitute a sign of CAD.