Myocardial perfusion and metabolic changes induced by conventional right and biventricular pacing in dilated cardiomyopathy evaluated by positron emission tomography.

Background: Biventricular pacing induces well-known effects on myocardial wall function, apparently providing better results in comparison with conventional right pacing in patients presenting with dilated cardiomyopathy (DCM). However, at the moment the secondary changes in myocardial metabolism induced by pacing devices are unclear. The aim of our study was to evaluate the possible changes in myocardial metabolism and perfusion induced by cardiac pacing in these patients.

Methods: Twenty-eight patients presenting with DCM were submitted to positron emission tomography. Eighteen patients were examined during cardiac pacing, 6 had dual chamber pacemakers implanted for conventional reasons (group A), 12 biventricular pacemakers (group B) for resynchronization purposes; the other 10 patients were considered as controls. Myocardial metabolism was evaluated using 18F-fluorodeoxyglucose (FDG), by the glucose load-insulin technique and perfusion using 13N-ammonia (NH3), injected at rest. A visual and a semiquantitative analysis were performed, calculating on the basis of the regions of interest the septum to lateral uptake (S/L) ratio.

Results: In all the 6 patients of group A, a selective defect in FDG uptake was observed in the septum (mean S/L ratio 0.67 +/- 0.15, p < 0.01 with respect to controls), while both the patients in group B and the controls presented a homogeneous distribution of FDG uptake in the myocardial wall (mean S/L ratio 1.01 +/- 0.10 and 0.95 +/- 0.13 respectively, p = NS). On the contrary, at the NH3 positron emission tomography studies no significant difference in myocardial perfusion was found in the three groups of patients, both at the visual and at the semiquantitative analysis (mean S/L ratio group A 1.01 +/- 0.21, group B 0.99 +/- 0.17, controls 0.94 +/- 0.11, p = NS).

Conclusions: Our experience could suggest that, in patients with DCM, conventional right pacing could induce interference in the metabolism of the septum not correlated with perfusion changes. On the other hand, biventricular pacing improves myocardial wall function without interfering with myocardial metabolism and perfusion.