Cardiac MRI may improve ablation procedures

Researchers from the University of Michigan Health System in Ann Arbor were able to detect radiofrequency ablation lesions in patients treated for ventricular arrhythmias — long after the initial procedure — via delayed-enhancement cardiac MRI.

“Integration of previous ablation lesions into the real-time ablation procedure helps to identify scars from previous ablation, which helps to limit unnecessary ablation lesions,” the researchers wrote.

They performed cardiac MRI (Signa Excite CV/i, General Electric) on 35 consecutive patients (19 women; mean age, 48 years; ejection fraction, 0.56) without structural heart disease who were referred for ventricular arrhythmia ablation before and after the procedure. All antiarrhythmic drugs were discontinued after the procedure, and 24-hour Holter monitor recording and an echocardiogram were performed at three- to six-month follow-up and again if palpitations recurred.

The procedure was successful in 29 patients (83%) and reduced the mean burden of premature ventricular complexes among those who experienced them frequently from 22% to 4% (P<.0001). The researchers identified new-site delayed-enhanced ablation lesions in 25 patients at a mean of 19 month follow-up. The lesions had a mean volume of 1.4 cm³ and a mean endocardial area of 3.5 cm². They determined that patients with the largest lesions (mean volume, 2.9 cm³; endocardial area, 6.4 cm²) had arrhythmias that originated in the papillary muscles. Additional findings confirmed the previously reported correlation between lesion size and the duration of radiofrequency energy delivered (P<.001).

“Identification of ablation lesions in patients with a failed procedure identified the sites where ineffective radiofrequency energy lesions were created,” the researchers wrote.

In an accompanying editorial, Saman Nazarian, MD, of the division of cardiology and cardiac arrhythmia at John’s Hopkins University in Baltimore, wrote that incorporating cardiac MRI into available techniques to identify scar arrhythmia substrates and monitor lesion formation may result in improved safety and efficacy during ventricular tachycardia ablation.

“This methodology can provide information regarding a dimension of ventricular muscle previously untapped due to limitations of surface mapping,” Nazarian wrote. “Ultimately, real-time cardiac MRI guidance of ventricular tachycardia ablation may provide the electrophysiologist with live information regarding the underlying scar substrate for ventricular tachycardia and allow precise titration of lesions.”

Ilg K. J Am Coll Cardiol Img. 2010;3:278-285.

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