An 84yr old white female, s/p VT/PEA arrest.
This ECG demonstrates AV dual sequenced pacing with loss of atrial capture. Note the high left axis in the x-y plane, consistent with typical pacer findings, but an atypical rightward shift of electrical forces across the precordial z-axis (inverse R-wave progression). Traditionally ventricular pacing electrodes are deployed in the right heart and result in a LBBB ECG morphology as the myocardial tissue depolarizes from right to left. Yet in this case we see a dramatic RBBB pattern, raising concerns about displacement or septal perforation, particularly given that the pt. has received CPR. The etiology of RBBB pacer morphology is not exclusively pathological, however, and receives a good discussion on Dr. S. Venkatesan’s Cardiology Blog. Note that the QRS in this case is elongated above 160ms, and necessarily reflects slow and poorly coordinated ventricular contraction, perhaps betraying a newly aberrant interventricular conduction pathway, even for this 100% paced patient.
Another interesting example of a similar RBBB effect can be seen at Dr. M. Rosengarten’s electrocardiography site, and there is a thorough case report and research analysis of the phenomenon in The Journal of Electrocardiography Vol.6 No. 1, 2003.
Shortly after this 12-lead was captured, the pt. again deteriorated into PEA and was lost to resuscitative efforts.