Postinfarction Myocardial Calcifications on Cardiac Computed Tomography: Implications for Mapping and Ablation in Patients With Nontolerated Ventricular Tachycardias.

Background: Postinfarction ventricular tachycardia (VT) generally involves myocardial fibers surrounded by scar. Calcification of scar tissue has been described, but the relationship between calcifications within endocardial scar and VTs is unclear. The purpose of this study was to assess the prevalence of myocardial calcifications as detected by cardiac computed tomography (CT) and the benefit for mapping and ablation focusing on nontolerated VTs.

Methods: Fifty-six consecutive postinfarction patients had a cardiac CT performed before a VT ablation procedure. Another 56 consecutive patients with prior infarction without VT who had cardiac CTs served as a control group.

Results: Myocardial calcifications were identified in 39 of 56 patients (70%) in the postinfarction group with VT, compared with 6 of 56 patients (11%) in the control group without VT. Calcifications were associated with VT when compared with a control group. A calcification volume of 0.538 cm distinguished patients with calcification-associated VT from patients without calcification-associated VTs (area under the curve, 0.87; sensitivity, 0.87; specificity, 0.88). Myocardial calcifications corresponded to areas of electrical nonexcitability and formed a border for reentry circuits for 49 VTs (33% of all VTs for which target sites were identified) in 24 of 39 patients (62%) with myocardial calcifications. A nonconfluent calcification pattern was associated with VT target sites independent of calcification volume ( P=0.01).

Conclusions: Myocardial calcifications detected by cardiac CT in patients with prior infarction are associated with VT. The calcifications correspond to areas of unexcitability and represent a fixed boundary of reentry circuits that can be visualized by CT. Calcifications correspond to effective ablation sites in >1/3 of patients with postinfarction VT.