Abstract
The morphology of pacemaker-induced QRS complexes is not an infallible criterion to locate the position of the stimulating electrodes.
3 Yet the patterns are specific enough to have clinical importance. This is more evident when there are sudden changes in QRS morphology. In these cases, a variation of the position of the electrodes usually occurs, except in patients with atriosynchronized units.
Permanent endocardial pacing is a valuable technique for the treatment of A-V conduction disturbances.
17 Although complications do occur, they are rarely fatal. Isolated reports have appeared dealing with right ventricular perforation. In one patient, perforation occurred in a “tunneling” fashion, the catheter transversing 2 cm. of the myocardium; and yet, this patient's death was most probably due to asystole rather than to cardiac tamponade. In another patient, perforation of the interventricular septum was suspected. However, the necropsy showed that the catheter had been stimulating the epicardial surface of the left ventricle through a vein draining in the coronary sinus.
Moreover, even the sudden appearance of a RBBB morphology in patients with right ventricular pacemakers should not be considered diagnostic of perforation. This pattern was shown to be due to several causes: (1) stimulation from specific areas within the right ventricle; (2) stimulation through the coronary sinus in its tributaries; and (3) dual A-V conduction in patients with atriosynchronized units.
