The images were diagnostic in 92.5%, 100%, and 97.5% with functional, adenosine stress perfusion, and viability studies, respectively. In addition, there were no adverse events or significant changes in pacemaker parameters.
There are increasing data regarding safe scanning in noncardiac MRI and some data reported in functional cardiac MRI studies. "However, there are no prospective data focused on stress and viability studies, which are the important steps for the evaluation of CAD," study coauthor Dr Thananya Boonyasirinant (Siriraj Hospital, Bangkok, Thailand) said at the Heart Rhythm Society (HRS) 2016 Scientific Sessions.
The study included 40 patients with MR-conditional pacemakers (>2 months) referred for MRI who underwent prospectively performed 1.5T MRI (Phillips Achieva XR scanner) under MR-safe conditions for suspected CAD. Patients had Boston Scientific's Advantio MRI, St Jude Medical's Accent MRI, and Medtronic's Ensura MRI pacemakers. MRI imaging included a 3- to 5-minute survey, 10- to 15-minute functional study, 5-minute adenosine stress perfusion test, and 7- to 10-minute viability study.
Imaging scan time varied from 30 to 55 minutes (mean 43 minutes). The mean specific absorption rate was 1.2 W/kg, which is below the 2 W/kg-recommended level, she noted.
Positive MRI results were found in 38% of patients, including myocardial ischemia in seven patients, MI in four, left ventricular thrombus in two, and valvular dysfunction in nine.
MRI image quality determined by two independent readers was lowest in the apical anterior segment, followed by the mid-anteroseptal, apical septal, and mid-anterior segments. Predictors of poor image quality were steady-state free-precession cine technique, short-axis plane, and distance from the pacemaker to the heart.
Pre- and post-MRI assessment revealed no significant changes in lead threshold, pacing parameters, or battery longevity, Boonyasirinant and coauthor Dr Satchana Pumprueg (Siriraj Hospital Mahidol Unive, Bangkok) reported.
|A sensed amplitude (mV)||2.772||2.795||0.82|
|A captured threshold (V@0.4 ms)||0.723||0.643||0.16|
|A lead impedance (Ω)||478.3||473.0||0.28|
|V- sensed amplitude (mV)||10.45||10.79||0.09|
|V- captured threshold (V@0.4 ms)||0.739||0.713||0.10|
|V lead impedance (Ω)||595.5||617.8||0.43|
|Battery voltage (V)||3.012||3.011||0.49|
Session chair Dr J Rod Gimbel (Case Western Reserve University, Knoxville, OH) said, "One of the things that I'm always impressed with is the quality of the images despite the expected image artifact."
He commented that one of the rationales for putting in MRI-conditional devices is that MRI studies are thought to be too important not to have access to but went on to question whether being able to use MRI or cardiac MRI, which he described as "sort of the Swiss Army knife of imaging," can lead to better outcomes.
Boonyasirinant said they have no outcome data yet, but "now we have data that the MR stress test gives more information, especially for the viability of the myocardium." Thus, they use the study after revascularizations, and because "there's no radiation, maybe it will be the imaging of choice in some patients."
The authors reported no relevant financial relationships.
Heartwire from Medscape © 2016 Medscape, LLC
Cite this: Evidence Builds for Cardiac MRI Safety, Diagnostic Images in Pacemaker Patients - Medscape - May 16, 2016.