Biventricular pacing exclusively via a persistent left-sided superior vena cava: case report.

Biventricular pacing in association with a persistent left-sided superior vena cava is technically challenging. The presence of an associated innominate vein enables a conventional approach via the right atrium for coronary sinus intubation and left ventricular lead placement. In its absence, the coronary sinus lead must be positioned exclusively via the left-sided superior vena cava. The acute angulation of the branch ostia encountered when catheterizing the coronary sinus "downstream" makes this difficult, but with the use of preshaped cardiac catheters and over-the-wire pacing leads selective intubation of a left ventricular vein is possible.