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

Abstract

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.

Pseudo‐pacemaker syndrome with prolonged PR interval: A narrative review

“…Apart from our case and the one published by Ogunlade et al 6 . where no clear association between the patient’s past medical history and the presence of PPMS could be found, four etiologies of PPMS were identified in the remaining cases (n. 15), as follows: (1) Idiopathic PPMS related to poor AV nodal conduction (20% of cases); 2,14,16 (2) reversible inflammatory causes (13%) such as acute myocarditis 15 or acute rheumatic fever; 13 (3) cardiac surgery, 20 interventional procedures 11 or chest radiation 17 leading to the permanent damage of the normal AV conduction system (20%), and, finally, (4) PPMS due to manifest dual AV nodal physiology (DAVNP) occurring as a primary finding (27%) 10,12,16,19 or post slow pathway ablation for treatment of AVNRT (20%) 10,18,21 . In fact, in this latter group, two patients (66%) had residual DAVNP due to damage to the fast pathway, either as a complication of slow pathway ablation 21 or deliberate ablation as a treatment option for AVNRT 10 .…”

“…Finally, except for patients with reversable causes of PPMS, 13,15 most were successfully treated by permanent pacemaker implantation 2,10,11,14,17,18,21 including PPMS cases with past medical history of pathway ablation as treatment of AVNRT 10,18,21 . However, patients with PPMS and DAVNP were variably treated with medications such as ivabradine (25%) or slow‐pathway ablation (75%).…”

“…More specifically, one patient developed a “pacemaker‐like syndrome” caused by AV nodal echo beats during sinus rhythm after slow pathway ablation for the treatment of AV nodal reentrant tachycardia (AVNRT), 8 and a “pacemaker‐like syndrome” caused by AV junctional rhythm was presented in another article 9 . Excluding these articles and including a cases series 10 and an abstract, 11 14 articles accounting for 16 patients with PPMS were retrieved in addition to the presented case report. Demographic data, presenting symptoms, PR interval, PPMS etiologies, and the results of non‐invasive and invasive tests along with treatment and the potential negative outcomes after treatment were collected in these 17 patients and summarized in Table 1.…”

“…(1) Idiopathic PPMS related to poor AV nodal conduction (20% of cases); 2,14,16 (2) reversible inflammatory causes (13%) such as acute myocarditis 15 or acute rheumatic fever; 13 (3) cardiac surgery, 20 interventional procedures 11 or chest radiation 17 leading to the permanent damage of the normal AV conduction system (20%), and, finally, (…”

“…As to invasive evaluation, none of the investigated cases (59%) exhibited a prolonged His bundle to ventricular myocardium (HV) interval even in cases of PPMS due to DAVNP with remarkably prolonged PR intervals. 10,19 Finally, except for patients with reversable causes of PPMS, 13,15 most were successfully treated by permanent pacemaker implantation 2,10,11,14,17,18,21 including PPMS cases with past medical history of pathway ablation as treatment of AVNRT. 10,18,21 However, patients with PPMS and DAVNP were variably treated with medications such as ivabradine (25%) or slow-pathway ablation (75%).…”