Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Electrocardiographic tracing of modified V1, V5, and D3 leads demonstrating sinus rhythm with alternating bundle branch block, right bundle branch block at the beginning of the ECG, followed by ventricular extrasystole and left bundle branch block. (A higher resolution / colour version of this figure is available in the electronic copy of the article).
