Abstract 2267: Can Patients with Acute Anterior Myocardial Infarction and Right Bundle Branch Block Be Further Risk-Stratified within 60 Minutes of Fibrinolytic Therapy?
Background: Patients with an acute anterior ST elevation AMI and RBBB have a high mortality risk, which may be stratified by early ECG changes.
Methods and Results: In the HERO-2 trial, 17,073 patients with AMI within 6 hours of symptoms onset were treated with streptokinase and randomised to receive bivalirudin or heparin. There was no difference in the primary endpoint of 30-day mortality. ECGs were recorded at randomisation and at 60 minutes after beginning fibrinolytic therapy. 30-day mortality was 31.6% in the 415 patients with RBBB and anterior AMI at randomization and 33% in the 100 patients who developed new RBBB at 60 minutes from normal baseline conduction accompanying an anterior AMI. An increasing QRS duration by 20msec increments was associated with increasing 30-day mortality in both RBBB groups on multivariable analyses with co-variates of age, Killip class, systolic blood pressure, pulse and prior infarction. Patients with QRS duration ≥160 msec had higher 30-day mortality than those with QRS duration <160 msec (37.2% vs 27.2%, P =0.03 and 46.2% vs 24.5%, P=0.025 in the 2 groups respectively). For the 415 patients, RBBB resolved at 60 minutes in 40 patients but 30-day mortality was unchanged (31.6%). For those with persisting RBBB at 60 minutes, 30-day mortality was lower if ST segment elevation had resolved by ≥50% (20.4% vs 35.3%, P=0.006).
Conclusion: In patients with anterior AMI and RBBB, increasing QRS duration is associated with increasing 30-day mortality. Early ST segment resolution after fibrinolytic therapy (despite persisting RBBB) is associated with lower mortality.