Myocardial fibrosis detected by cardiac CT predicts ventricular fibrillation/ventricular tachycardia events in patients with hypertrophic cardiomyopathy

Abstract

Background: Myocardial fibrosis (MF) occurs in up to 80% of subjects with asymptomatic or mildly symptomatic hypertrophic cardiomyopathy (HCM) and can constitute an arrhythmogenic substrate for re-entrant, life-threatening ventricular arrhythmias in predisposed persons.

Objective: The aim was to investigate whether MF detected by delayed enhancement cardiac CT is predictive of ventricular tachycardia (VT) and fibrillation (VF) that require appropriate therapy by an implantable cardioverter defibrillator (ICD) in patients with HCM.

Methods: Twenty-six patients with HCM with previously (for at least 1 year) implanted ICD underwent MF evaluation by cardiac CT. MF was quantified by myocardial delayed enhanced cardiac CT. Data on ICD firing were recorded every 3 months after ICD implantation. Risk factors for sudden cardiac death in patients with HCM were evaluated in all patients.

Results: MF was present in 25 of 26 patients (96%) with mean fibrosis mass of 20.5 ± 15.8 g. Patients with appropriate ICD shocks for VF/VT had significantly greater MF mass than patients without (29.10 ± 19.13 g vs 13.57 ± 8.31 g; P = .01). For a MF mass of at least 18 g, sensitivity and specificity for appropriate ICD firing were 73% (95% CI, 49%-88%) and 71% (95% CI, 56%-81%), respectively. Kaplan-Meier curves indicated a significantly greater VF/VT event rate in patients with MF mass ≥18 g than in patients with MF <18 g (P = .02). In the Cox regression analysis, the amount of MF was independently associated with VF/VT in ICD-stored electrograms.

Conclusion: The mass of MF detected by cardiac CT in patients with HCM at high risk of sudden death was associated with appropriate ICD firings.

Keywords: Delayed enhancement cardiac computed tomography; Hypertrophic cardiomyopathy; Implantable cardiac defibrillator; Myocardial fibrosis; Ventricular arrhythmias.

Figure 1

Image analysis for determination of myocardial fibrosis. Delayed cardiac CT images in 4-chamber (A) and shortaxis (B) views show septal hypertrophy associated with myocardial hyperenhancement (black arrow). Metal artifact caused by implantable cardioverter defibrillator lead (white arrow) precludes the analysis of inferoseptal left ventricular segment. (C) Segmentation of the LV is shown in the short-axis view. (D) Exclusion of the inferoseptal left ventricular segment. LA, left atrium, LV, left ventricle, RA, right atrium, RV, right ventricle.

Figure 2

Delayed cardiac CT scan of a 26-year-old female patient with 55.1 g ofmyocardial fibrosis and appropriated shock by implantable cardioverter defibrillator shown in 4-chamber (A) and short-axis (B) views. Extensive myocardial fibrosis is present in the interventricular septum (white arrows). An implantable cardioverter defibrillator lead artifact is present (black arrows). LA, left atrium, LV, left ventricle, RA, right atrium, RV, right ventricle.

Figure 3

Delayed cardiac CT scan of an 18-year-old male patient with 8.3 g of myocardial fibrosis and no ventricular fibrillation or ventricular tachycardia event shown in 2-chamber (A) and short-axis (B) views. A small area of myocardial fibrosis is present in the anteroseptal region of the left ventricle close to the right ventricular junction (arrows). LA, left atrium, LV, left ventricle, RV, right ventricle.

Figure 4

Kaplan–Meier curve indicating VF/VT event-free survival for patients with myocardial fibrosis (MF) ≥18 g (dotted line) and <18 g (continuous line). VF, ventricular fibrillation; VT, ventricular tachycardia.