Abstract 4091: Characteristics of the Electroanatomical Substrate in Patients with Fast and Slow Ventricular Tachycardias Late after Myocardial Infarction
Ventricular tachycardias (VT) in patients after myocardial infarction (MI) may be unstable prohibiting catheter mapping due to short VT cycle lengths (CL). Linear radiofrequency lesions applied at the scar borderzone can be effective to eliminate these VTs. This study used voltage mapping to assess characteristics of the electroanatomical substrate for fast and slow VTs in post MI patients. The study population consisted of 34 consecutive patients referred for radiofrequency ablation of sustained VT after MI. Group A (12 patients, 12 male, age 60±12yr, 67% anterior MI) with documented spontaneous or inducible fast VT (CL<250ms) were compared to 22 patients (18 male, age 65±16yr, 73% anterior MI) with slow VT (CL>250ms, group B). All patients underwent programmed electrical stimulation and left ventricular electroanatomical sinus rhythm voltage mapping. Bipolar electrogram amplitudes >0.5mV were defined as dense scar, >0.5mV and ≤1.5mV as borderzone and a ‘patchy pattern’ as multiple low voltage areas separated by areas of normal voltage (>1.5mV). VT occurred 10±11yr (group A) and 14±8yr (group B), respectively after the index MI (p=ns). Mean LV ejection fraction was comparable in both groups (A 31±14% vs. B 26±10%, p=ns). The mean VT CL was 236±12ms in group A and 318±55ms in group B (p<0.01). In group A 42% had underwent early reperfusion with an angiographically documented patent infarct related artery (IRA) directly and at the time of VT occurrence compared to 9% in group B (p=0.03). A patchy pattern of LV scar in the IRA supplied area was present in 83% of group A compared to 5% in group B (p<0.01) and the proportion of dense scar was significant smaller in group A than in group B (20±15% vs. 49±19%, p<0.01). The characteristics of low voltage scars after MI are different in patients with and without fast VT’s. Less confluent scars are associated with early reperfusion with a patent IRA and give rise to faster VTs. These findings have implications for VT ablation strategies that target the infarct border zones.