Transvenous cardiac pacing. Technics for optimal electrode positioning and prevention of coronary sinus placement.

Optimal electrode position for long-term transvenous cardiac pacing is in the apex of the right ventricle. Intracardiac electrograms, surface electrocardiograms, frontal fluoroscopy, lateral roentgenograms, and pacing threshold levels were studied in two groups of patients: One group was comprised of five patients with permanent pacemakers who had inadvertent malplacement of the pacing catheter, and the second group was composed of six patients undergoing temporary pacing from selected sites within the coronary venous system. The results of this study indicate that the appearance of a characteristic right ventricular endocardial complex recorded from the catheter tip is the most reliable guide to proper electrode placement. Low threshold levels, good position demonstrated roentgenographically, and typical surface electrocardiographic patterns of left bundle-branch block were all noted during intentional and following inadvertent malpositioning of the electrode within the coronary venous system and do not, therefore, guarantee proper positioning. A successful routine for pacemaker insertion has been established which includes fluoroscopy, lateral roentgenograms, intracardiac and surface electrocardiograms, and threshold analysis. Satisfaction of all these tests appears to insure proper electrode positioning.