Mapping and ablation of polymorphic ventricular tachycardia after myocardial infarction

Abstract

Objectives The goal of this study was to describe the mapping and ablation of polymorphic ventricular tachycardia (VT) after myocardial infarction (MI). Background The initiating mechanisms of polymorphic VT after MI have not been reported. Methods Five patients (four males; age 61 ± 7 years) with recurrent episodes of polymorphic VT after anterior MI (left ventricular ejection fraction 32 ± 7%) despite revascularization and antiarrhythmic drugs were studied. All patients demonstrated frequent ventricular premature beats (PBs) initiating polymorphic VT. Pace mapping and activation mapping were used to identify the earliest site of PB activity. The presence of a Purkinje potential preceding PB defined its origin from the Purkinje network. Electroanatomic voltage mapping was performed to delineate the extent of MI. Results The PBs were observed in all cases to arise from the Purkinje arborization in the MI border zone. These PBs were right bundle-branch block in all five patients, with morphologic variations in the limb leads in four; one also had a left bundle-branch block morphology. The coupling interval of the PB to the preceding QRS complex demonstrated significant variations (320 to 600 ms). During PB, the Purkinje potential at the same site preceded the QRS complex by 20 to 160 ms and was associated with different morphologies. Repetitive Purkinje activity was documented during polymorphic VT. Splitting of Purkinje activity and Purkinje to muscle conduction block were also observed. Ablation at these sites eliminated all PBs. At 16 ± 5 months follow-up using defibrillator memory interrogation, no patient has had recurrence of arrhythmia. Conclusions The Purkinje arborization along the border-zone of scar has an important role in the mechanism of polymorphic VT in patients after MI. Ablation of the local Purkinje network allows suppression of polymorphic VT.