Sex differences in ventricular function in patients with right bundle branch block

Prognostic value of exercise stress technetium-99m-tetrofosmin myocardial perfusion imaging in patients with normal baseline electrocardiograms

Exercise stress electrocardiography is the recommended method for cardiac evaluation of patients with normal electrocardiograms (ECGs). There are no data to indicate an independent value of myocardial perfusion imaging (MPI) in predicting mortality in these patients. This study assessed the value of exercise stress MPI in predicting mortality in patients with normal baseline ECGs. We studied 319 patients (55 +/- 10 years of age; 180 men) with normal ECGs by exercise stress technetium-99m tetrofosmin MPI. End points during follow-up were cardiac and all-cause mortalities and hard cardiac events. A normal scan was detected in 190 patients (60%). Myocardial perfusion abnormalities were fixed in 59 patients (18%) and reversible in 70 (23%). During a mean follow-up of 7 +/- 1.2 years, 46 patients (14%) died. Death was considered cardiac in 28 patients (9%). Nonfatal myocardial infarction occurred in 12 patients (4%). Annual cardiac death rates were 0.4% in patients with normal perfusion, and 2.7% in patients with reversible defects. Annual total mortality rates were 1.1% in patients with normal perfusion and 3.4% in patients with reversible defects. In a multivariate analysis model, reversible perfusion abnormalities were associated with cardiac death (RR 2.8, 95% confidence interval 1.6 to 5.1) and hard cardiac events (RR 2.7, 95% confidence interval 1.5 to 4.5). Perfusion abnormalities in multivessel distribution were predictive of all-cause mortality (RR 2, 95% confidence interval 1.4 to 3.2). ST-segment depression was not significantly associated with events. In conclusion, stress technetium-99m tetrofosmin MPI provides independent information for predicting cardiac and overall mortalities in patients with normal ECGs. Reversible perfusion abnormalities, but not ischemic electrocardiographic changes, are predictive of outcome in these patients.

Impact of intraventricular conduction delay on coronary haemodynamics: a study with intracoronary Doppler in patients with bundle branch blocks and normal coronary arteries

AIMS

The impact of right bundle branch block (RBBB) and left bundle branch block (LBBB) on myocardial perfusion is not completely understood as data are often blurred by underlying cardiac disease. The present study investigates whether conduction delays per se affect coronary perfusion-an indirect measure of myocardial oxygen demand.

METHODS AND RESULTS

Intracoronary Doppler and ultrasound were performed in 8 patients with RBBB, 10 patients with LBBB, and 10 control subjects. All patients had angiographically normal coronary arteries and normal left ventricular function. Baseline (bAPV) and adenosine-induced hyperaemic average flow velocity and coronary flow velocity reserve (CFVR) were measured in left anterior descending arteries. Intravascular ultrasound showed no difference in lumen cross-sectional area and plaque burden between groups. Patients with RBBB and LBBB had higher bAPV values than controls (19.0 +/- 4.9, 21.9 +/- 5.1, and 14.6 +/- 2.4 cm/s, respectively; ANOVA P = 0.003). There was no difference between patients with LBBB and RBBB compared with controls in CFVR (2.8 +/- 0.5, 3.0 +/- 1.0, and 3.4 +/- 0.7, respectively; ANOVA P = 0.21).

CONCLUSION

Bundle branch blocks, in particular LBBB, are associated with an increased coronary flow velocity, which indicates enhanced myocardial oxygen demand on the basis of mechanoenergetic disturbance. This may contribute to the unfavourable outcome of patients with intraventricular conduction delay.