Abstract 16643: Pacemaker For First Degree AV Block Without Bradycardia: Pseudo-pacemaker Syndrome

Case Presentation: An 86 year old man underwent PCI of distal LAD for severe single vessel coronary artery disease identified after a high risk pharmacologic nuclear stress test (evaluation of exertional fatigue prior to abdominal aortic aneurysm surgical repair). ECHO was consistent with preserved LVEF (60-65%), moderate concentric LVH and mild left atrial enlargement. Less than a week after PCI, he presented to the emergency department for NYHA III dyspnea and fatigue. The patient was not taking any negative chronotropic medications. CT angiography of the chest excluded pulmonary edema, pneumonia and pulmonary embolism; repeat limited ECHO was unchanged. EKG showed first degree AV block (PR 400ms, figure 1). Severely prolonged PR interval with otherwise-unexplained exertional symptoms raised suspicion for pseudo-pacemaker syndrome. In the absence of an alternative cause of declining exertional tolerance, a dual chamber pacemaker with short programmed AV delay (<200ms) was implanted. The patient reported resolution of exertional fatigue and dyspnea on one-month followup. Discussion: Pseudo-pacemaker syndrome is a rare, infrequently reported, complication of first degree AV block with severely prolonged PR>300ms. P-wave at the end of the preceding T-wave suggests AV dyssynchrony (arrowhead, figure 1). Left atrial contraction against a closed mitral valve led to loss of atrial contribution to cardiac output, and elevated left atrial pressure. These changes, accentuated by physiologic increase in heart rate on exertion, most likely caused symptoms in this patient. It is interesting that AV dyssynchrony in pacemaker syndrome is caused by the pacemaker (VVI pacing) whereas the AV dyssynchrony in pseudo-pacemaker syndrome from severely prolonged PR interval is treated with a pacemaker. In the appropriate clinical picture, it is an indication for dual-chamber pacemaker implantation for first degree AV block without bradycardia or pauses.