In Vivo Temperature Threshold for Myocardial Thermal Damage

Peter Nabil Costandi¹, Ramez Emile Necola Shehada¹, Neha Bharat Butala¹, Ben Anthony Coppola¹, Kevin Jurkowski¹, Ali Dianaty¹

Current contraindications for pacemaker patients in clinical MR systems stem primarily from RF induced tissue heating hazards. The quantified effect of elevated temperature doses on myocardial tissue remains unknown. Sixteen canines were implanted with a ventricular pacing system capable of monitoring temperature of viable myocardium. Three cumulative one-hour thermal doses to 44C were applied to each chronic canine. Change in capture threshold relative to baseline was measured following each heating cycle and shown to increase by 68%, 81% and 83%, respectively. These findings provide data that may serve as a foundation for proof of safety of pacemaker systems in MRI.