Successful high-density mapping and ablation of atrial tachycardia in a patient with dextrocardia and situs inversus: a complex case

Abstract

A 56-year-old man was referred to our laboratory for treatment of recurrent atrial tachycardia (AT) and severe left ventricular (LV) dysfunction [ejection fraction (EF) 28%]. He had a history of complex congenital heart disease, including situs inversus, dextrocardia, pulmonary stenosis and hypoplasia of the right pulmonary artery, congenitally corrected transposition of the great vessels according to Rastelli’s conversion, and two subsequent surgeries on the right ventricular-pulmonary conduit. In the years before his referral, the patient had experienced multiple arrhythmic episodes of ectopic AT and atrial fibrillation and had subsequently undergone ablations, including isthmic flutter ablation. The activation and voltage maps were constructed by means of the Orion multipolar basket catheter and the Rhythmia 3-dimensional electroanatomic mapping system (Boston Scientific, USA). An open-irrigated ablation catheter was used for radiofrequency (RF) delivery (IntellaNavMiFi OI, Boston Scientific, USA). The clinical AT presented with a cycle length of 310 ms and a wavefront activation moving from the proximal to the distal coronary sinus (CS) (Supplementary material online, Figure S1). The activation map of the systemic venous atrium revealed evidence of slow conduction areas with fragmented and late potentials of 145 ms duration inside the posterior-lateral region close to the areas of previous surgical incision (dense scar areas, at the site of intercaval line of the previous heart surgery) (Figure 1A; Supplementary material online, Video S1). The bipolar voltage map showed large areas of low potential signals at the level of the atrial wall close to the CS ostium, posterior near the superior vena cava, and at the vena cava-tricuspid isthmus (site of previous ablation) (Figure 1B). Interestingly, the slow conduction area within the scar area provided information perfectly coincident with what was shown by the propagation map. In this area, the ablation catheter recorded low-quality electrogram signals, which however revealed low-amplitude fragmented