A 13-year-old boy with complex cyanotic congenital heart disease with criss-cross atrio-ventricular connection presented with Wolff-Parkinson-White (WPW) syndrome and recurrent orthodromic re-entrant tachycardia. During electrophysiological study, the accessory pathway was mapped along the left atrioventricular annulus initially but was successfully ablated through the left atrial appendage. The case describes the challenges and the intricacies while ablating an atypical accessory pathway connection in the setting of complex congenital heart disease.

Title: Sudden QRS widening while ablating a concealed left accessory pathway during left ventricular pacing

An 88-year-old man underwent a dual chamber pacemaker implantation for complete heart block. Post procedure 12-lead electrocardiogram showed some abnormal findings. The reader is challenged to identify the abnormalities and then explain the mechanism of these findings. The discussion then guides the reader with the explanation.

EP Rounds

A 44-year-old lady, a follow up case of idiopathic dilated cardiomyopathy and cardiac resynchronization therapy defibrillator (CRT-D) device implantation with epicardial left ventricular (LV) lead, underwent a transvenous LV lead revision in view of epicardial lead malfunction. A chest X-ray after this, done for worsening dyspnoea, revealed pneumopericardium along with left pneumothorax. The CT revealed a communication between the left pleural and pericardial cavities, around the old epicardial lead. Drainage of the left pleural cavity resolved both the pneumothorax and pneumopericardium and the patient remained well on follow up.

A 53- year old woman presented with recurrent episodes of paroxysmal tachycardia with a structurally normal heart. She had undergone an electrophysiology study in an outside hospital which revealed orthodromic atrioventricular reentrant tachycardia (ORT) using a concealed left posterolateral accessory pathway (AP), for which radiofrequency ablation was performed. But tachycardia recurred three months later. In view of significant symptoms, she came to us for a repeat procedure. The AH and HV intervals were 77 ms and 45 ms respectively. Narrow complex tachycardia with a cycle length (CL) of 300 ms was easily and repeatedly induced and terminated (Figure 1, left panel) by a premature ventricular complex (PVC). Shortly another tachycardia with CL of 255 ms was induced and terminated (Figure 1, right panel) by a premature ventricular complex. Later, during another tachycardia, a spontaneous change was seen (Figure 2). Are we dealing with a single tachycardia mechanism?