Clinical introduction A 72-year-old woman presented with an 8-year history of palpitations occurring every few weeks. They were sudden in onset, were associated with dizziness and could last for up to 2 hours. She was prescribed bisoprolol which reduced the frequency of events but did not abolish them. Baseline ECG and echocardiography were normal. She was referred for electrophysiological study. Despite initial difficulties, diagnostic catheters were placed in the right ventricular (RV) apex and in the coronary sinus (CS) via the right internal jugular vein and superior vena cava (SVC) (figure 1A). A narrow complex tachycardia was easily induced, and ablation was then delivered during tachycardia with the ablation catheter positioned as shown in (figure 1A). This terminated tachycardia 4 s after onset of energy delivery and on follow-up she has remained asymptomatic. She later underwent a CT scan (figure 1B,C; online supplementary video).
Supplementary file 1
Question What anatomical abnormality caused difficulty in catheter placement during the procedure?
Azygous continuation of the inferior vena cava (IVC)
Giant Eustachian valve
Renal tumour compressing IVC
- Atrial arrhythmia ablation procedures
- catheter ablation
- supraventricular arrhythmias
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Catheters could not be advanced from the femoral vein to the right atrium (RA). The sagittal CT still image (figure 1B) and video (online supplementary video) show an abnormal azygous vein draining into the SVC, with hepatic veins draining directly into the inferior RA consistent with azygous continuation of the IVC. Fluoroscopy and CT are inconsistent with dextrocardia, and there is no evidence of a giant Eustachian valve on CT with no obstruction to contrast, nor is there any evidence of a renal tumour on the transverse CT image (figure 1C) with the IVC clearly visualised.
Diagnostic catheters were placed in the RV apex via the azygous vein and in the CS via the SVC (figure 1A). Electrophysiological study demonstrated an orthodromic atrioventricular re-entrant tachycardia via a left lateral pathway (see online supplementary file, supplementary figures A,B), and the ablation catheter was therefore introduced into the left ventricle via a retrograde femoral arterial approach.
Supplementary file 2
Ventricular pacing showed non-decremental retrograde conduction with earliest atrial activation in the distal CS (CS 1-2) (A), consistent with a left lateral pathway. Earliest atrial activation during tachycardia was at CS 1-2, consistent with LA tachycardia or orthodromic AVRT via a left lateral pathway. Ventricular entrainment of the tachycardia demonstrated a V-A-V response (B), supporting diagnosis of an orthodromic AVRT. Earliest atrial activation was mapped to 4 o’clock on the mitral annulus, where ablation terminated the tachycardia 4s after onset of energy delivery.(RV = right ventricle, CS = coronary sinus.)
Interruption of the IVC with azygous continuation is of clinical importance as it suggests the possibility of associated structural defects. The patient’s CT scan also demonstrated polysplenia (figure 1C) and she was diagnosed with heterotaxy syndrome. This involves abnormal arrangement of the thoracoabdominal organs, typically either in a left or right isomerism pattern. A wide range of phenotypes has been described, with extracardiac manifestations including asplenia or polysplenia, intestinal malrotation and biliary atresia. Cardiac anomalies are common, typically characterised by either right or left atrial appendage isomerism,1 and may also involve atrioventricular septal defects or anomalies of systemic or pulmonary venous return. Sinus node disease and complete atrioventricular block frequently occur in left atrial isomerism, but no specific association with accessory pathways has yet been described.
The authors thank Dr Andrew Grace for his assistance in the clinical case, and Dr Bobby Agrawal and Dr Harmeet Chana for their assistance in the preparation of the manuscript.
Contributors CAM, PRG and SA were involved in the clinical case and wrote the manscript.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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