Epicardial Focal Ventricular Tachycardia Due to Micro-Reentry in a Patient with Cardiac Sarcoidosis

Aims: Ventricular arrhythmias (VAs), especially sustained monomorphic ventricular tachycardia (SMVT), are among the most important manifestations of cardiac sarcoidosis. Most SMVTs in Sarcoidosis are caused by scar-related macro reentry. We describe an unusual case where two SMVTs with focal activation pattern on electroanatomical mapping (EAM) due to micro-reentry, which were successfully ablated from the epicardial aspect with radiofrequency ablation (RFA).

Materials and results: A 37-year-old previously healthy male presented with a history of SMVT from 2 years and a single-chamber ICD was implanted in another center. Over 2 years he received multiple shocks and had one episode of heart failure. The patient was evaluated in our center and diagnosed with probable cardiac sarcoidosis. Device interrogation showed most episodes of VT could be terminated by anti-tachycardia pacing (ATP). The patient was taken up for electrophysiology (EP) study. Endocardial bipolar and unipolar voltage mapping did not show any significant scar. Two distinct SMVTs could be easily initiated with programmed electrical stimulation (PES). Entrainment showed progressive fusion. This along with the fact that it was reproducible induced by PES and terminated by ATP indicated a reentrant mechanism. However, endocardial activation map with EAM showed focal activation pattern with a wide early area. So epicardial mapping was done which showed a small focal early activation.RFA at this site initially slowed down the tachycardia without a change in morphology and terminated it in 12 seconds (Fig.1). The second less common tachycardia was also induced and exhibited similar features. It was ablated focally on the epicardial surface of RVOT.

Conclusions: Sarcoidosis typically produces subepicardial and mid-wall scarring. A micro-reentry circuit entirely situated within the thickness of the myocardium with an epicardial exit site can explain the findings in our case.