Incidence, electrophysiological characteristics, and long-term follow-up
of perimitral atrial flutter in patients with previously confirmed
mitral isthmus block
Abstract
Introduction: After mitral isthmus (ΜΙ) catheter ablation, perimitral
atrial flutter (PMF) circuits can be maintained due to the preservation
of residual myocardial connections, even if conventional pacing criteria
for complete MI block are apparently met (MI pseudo-block). We aimed to
study the incidence, the electrophysiological characteristics, and the
long-term outcome of these patients. Methods and Results: Seventy-two
consecutive patients (mean age 62.4±10.2, 62.5% male) underwent MI
ablation, either as part of an atrial fibrillation (AF) ablation
strategy (n=35), or to treat clinical reentrant atrial tachycardia (AT)
(n=32), or to treat AT that occurred during ablation for AF (n=5). Ιn
all patients the electrophysiological characteristics of PMF circuits
were studied by high-density mapping. MI block was successfully achieved
in 69/72 patients (95.6%). Five patients developed PMF after confirming
MI block. In these patients, high-density mapping during the PMF showed
a breakthrough in MI with extremely low impulse conduction velocity
(CV). In contrast, in usual PMF circuits that occurred after AF
ablation, the lower CV of the reentrant circuit was of significantly
higher value (0.07±0.02m/s vs 0.25±0.07m/s, respectively;
P<0.001). Patients presented with clinical AT had better
prognosis in maintaining sinus rhythm after MI ablation compared with
patients presented with AF. Conclusion: PMF with MI pseudo-block may be
present after MI ablation and has specific electrophysiological features
characterized by remarkably slow CV in the MI. Thus, even after MI block
is achieved, a more detailed mapping in the boundaries of the ablation
line or reinduction attempts may be needed to exclude residual
conduction.