Dual Atrial Rhythms: A Case Report Of An Unusual Cause Of Pacemaker Syndrome

Background Atrial dissociation (AD) is described as the existence of two simultaneous electrically isolated atrial rhythms. Theoretically, detection of dual atrial rhythms with a sufficiently high rate by pacemaker can lead to automatic mode switching and associated pacemaker syndrome. Such a clinical observation has not been reported before in the literature. Case Summary An 87-year-old female with Ebstein’s anomaly status post tricuspid valve annuloplasty and tricuspid valve replacement and a dual chamber pacemaker presented with congestive heart failure one week after undergoing atrial lead revision. Interrogation of her dual chamber pacemaker revealed two atrial rhythms: sinus or atrial-paced rhythm and electrically isolated atrial tachycardia (AT). Sensing of both atrial rhythms by the pacemaker led to automatic mode switching, which manifested as ventricular paced rhythm with retrograde P waves on electrocardiogram (ECG). Adjusting the atrial lead sensitivity to a level higher than the sensing amplitude of AT restored atrial paced and ventricular sensed rhythm, which resulted in resolution of heart failure symptoms. Discussion Regardless of the cause of AD, there must be electrical insulation between the two rhythms for their independent coexistence in the atria. AD can lead to pacemaker syndrome from automatic mode switching. If the sensing amplitude during sinus rhythm is significantly larger than that of AT, adjusting the atrial lead sensitivity would solve the issue, as in the present case. Otherwise, atrial lead revision, pharmacotherapy or AT ablation should be considered.

309 Upgrading from a dual-chamber pacemaker to a cardiac resynchronization therapy defibrillator in situs inversus totalis with dextrocardia following mitral valve replacement and tricuspid annuloplasty using a left-sided approach

A 71-year-old female patient was referred to our centre to upgrade a dual-chamber pacemaker to a cardiac resynchronization therapy defibrillator (CRT-D) following the detection of worsened systolic function (ejection fraction: 25–30%) via transthoracic echocardiography. The patient had situs inversus totalis with dextrocardia. She had undergone mitral valve replacement and tricuspid annuloplasty in July 2019, with a concomitant left upper pulmonary lobectomy for neoplasm, detected at cardiac tomography incidentally. In January 2020, we performed an upgrade of the preexisting device to a CRT-D system because the patient developed heart failure, reduction in systolic function, and numerous nonsustained ventricular tachycardias. The right ventricular lead that had been previously implanted was extracted. To facilitate the intervention, we decided to flip the fluoroscopic image, obtained with a right-anterior oblique view, by 180 °C (right–left), creating the optical impression of a levocardial position.

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.

Inadvertent left ventricular pacing due to lead malpositioning, incidentally discovered seventeen years later

Inadvertent lead malpositioning into the left ventricle (LV) is an uncommon complication of pacemaker lead implantation. It can have implications on clinical outcome due to ventricular dyssynchrony, and result in further complications such as thrombus formation with subsequent embolisation. This case study reports the clinical, electrocardiographic, plain film and echocardiographic findings of an 82-year-old male in whom the intravenous lead of a dual chamber pacemaker was unintentionally passed into the LV via an atrial septal defect. Inadvertent placement was discovered incidentally following the onset of atrial fibrillation (AF) 17 years later.