Pacemaker Implantation in a Patient With Dextrocardia, Corrected Transposition, and Situs Inversus
A 65-year-old woman was referred for assessment of 2 syncopal episodes that occurred in a seated position without preceding symptoms. She regained consciousness within 30 seconds and had no associated ictal phenomena.
She had a prior diagnosis of dextrocardia, corrected transposition, and situs inversus; in addition, she had a prosthetic systemic atrioventricular valve implanted 5 years ago for severe valvular regurgitation (thick line in Figures 1 and 2⇓).
Examination was remarkable for prosthetic heart sounds and a right-sided apical impulse. The ECG showed marked first-degree atrioventricular block, left bundle-branch block, and evidence of dextrocardia (Figure 3A). Transthoracic echocardiography revealed a moderately dilated and impaired systemic ventricle with an estimated ejection fraction of 35% to 40% and a normally functioning prosthetic valve. Ambulatory monitoring did not reveal significant arrhythmias, and there were no reported symptoms during the recording. Given the clinical scenario, baseline ECG, and underlying congenital heart disease, a bradyarrhythmia was thought to be the most likely cause of her syncope. After a discussion with the patient, a dual-chamber pacemaker was implanted (the ECG in Figure 3B) using a defibrillator lead placed in the apex of the systemic right ventricle (dashed line in Figures 1 and 2) and an atrial lead placed in the right atrial appendage (thin line in Figures 1 and 2). The rationale for choosing a defibrillator lead was based on the potential long-term need for upgrade to an implantable defibrillator given the systemic ventricular impairment and the challenges with vascular access and anatomy. The pacemaker implantation was successful, and the patient has remained well with no further syncope over 6 months of follow-up.