Feasibility study: Characterizing acute lesion dimensions in patients with and without devices using noncontrast (native T-weighted) magnetic resonance imaging after ventricular tachycardia/premature ventricular complex radiofrequency ablation.

Background: Late gadolinium enhancement magnetic resonance imaging (MRI) has been shown to reliably locate radiofrequency ablation (RFA) lesions with microvascular obstruction (MVO) as a broadly accepted signature. However, MVO volume depends on the time elapsed after gadolinium contrast injection. Native T1-weighted (Tw) MRI has recently been shown to accurately characterize RFA lesions in preclinical models.

Objective: This study aimed to demonstrate the feasibility of wideband native Tw MRI in characterizing lesion dimensions in patients within 7 days of ventricular tachycardia RFA.

Methods: Postablation wideband native Tw and 3-dimensional late gadolinium enhancement MRI was performed within 7 days of RFA. RFA lesion surface area (mm), volume (mm), and native Tw maximum lesion depth were calculated. Average catheter contact force (g), ablation duration (seconds), and impedance drop (Ω) were calculated. Patients with and without implantable cardioverter-defibrillators were included.

Results: Ten patients (median age = 64.5 years, 60% ischemic) underwent ventricular tachycardia RFA (80% endocardial, 20% epicardial RFA) and postablation cardiac MRI within 7 days of RFA (median = 4.5 days). There was a significantly greater mean MVO surface area and volume than mean native Tw lesion surface area and volume (P = .0108, P = .0376, P < .05), respectively. There were strong positive correlations between average surface area and average volume measured by MVO and native Tw (r = 0.71, P = .0237, r = 0.70, P = .0265, P < .05), respectively. Average maximum native Tw lesion depth correlated with average ablation duration and average impedance drop (r = 0.73, P = .02, r = 0.68, P = .04, P < .05), respectively.

Conclusion: Native Tw MRI can effectively characterize lesion dimensions in patients with and without implantable cardioverter-defibrillators within 7 days after ablation. This emerging biomarker may facilitate early prediction of RFA efficacy and ablation success particularly in patients demonstrating contraindications to gadolinium contrast agents.