Assessment of myocardial fatty acid metabolism in atrioventricular synchronous pacing: analysis of iodine 123-labeled beta-methyl iodophenyl pentadecanoic acid SPECT.

BACKGROUND: We used beta-methyl iodophenyl pentadecanoic acid (BMIPP) single photon emission computed tomography (SPECT) to evaluate fatty acid metabolism in patients who were candidates for permanent pacemaker implantation and in patients with atrioventricular (AV) synchronous pacing. METHODS AND
RESULTS: We performed BMIPP SPECT studies in 66 patients with bradyarrhythmia, of whom 11 patients were candidates for permanent pacemaker implantation, 27 patients had atrial pacing (atrial sensing, inhibited mode, simple programmable [AAI]), and 28 patients had atrial synchronous ventricular inhibited pacing (ventricular pacing, 2-chamber sensing, atrial-triggered and ventricular-inhibited, multiprogrammable [VDD]) or atrial and ventricular pacing in sequence (atrial and ventricular sensing, atrial-inhibited and atrial-triggered, ventricular-inhibited, multiprogrammable [DDD]). A qualitative assessment revealed that the BMIPP uptake at the septal, inferior, and apical regions was significantly decreased in the patients with VDD/DDD compared with both the candidates for permanent pacemaker implantation and the patients with AAI. The total extent score (ES) and severity score (SS) were significantly higher in the patients with VDD/DDD than in the other 2 groups. Significant regional differences of both ES and SS values were observed at the septal and inferior regions in the patients with VDD/DDD compared with the other groups. No differences were found between the qualitative and quantitative measures of BMIPP uptake in the candidates for permanent pacemaker implantation and those in the patients with AAI.
CONCLUSION: Our study suggests that AV synchronous right ventricular pacing resulting in the delayed conduction and depolarization of myocardial cells may directly interfere with regional cellular free fatty acid uptake and metabolism.