Cardiac resynchronization therapyhomogenizes myocardial glucosemetabolism and perfusion in dilatedcardiomyopathy and left bundle branch block

Abstract

ObjectivesWe investigated whether cardiac resynchronization therapy (CRT) affects myocardial glucose metabolism and perfusion in dilated cardiomyopathy (DCM) and left bundle branch block (LBBB). BackgroundPatients with DCM and LBBB present with asynchronous left ventricular (LV) activation, leading to reduced septal glucose metabolism. Cardiac resynchronization therapy recoordinates LV activation, but its effects on myocardial glucose metabolism and perfusion remain unknown. MethodsIn 15 patients (10 females; 61 ± 13 years) with DCM and LBBB (QRS width 165 ± 15 ms), gated 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and technetium-99m (99mTc)-sestamibi single-photon emission computed tomography were performed before and after two weeks of CRT. Uptake of FDG and 99mTc-sestamibi was determined in four LV wall areas. Ejection fraction and volumes were calculated from gated PET. ResultsBaseline FDG uptake was heterogeneous (p < 0.0001), with lowest uptake in the septal region (56 ± 12%) and highest uptake in the lateral region (89 ± 6%). During CRT, septal and anterior increases (p < 0.01) and lateral decreases (p < 0.01) resulted in homogeneously distributed glucose metabolism. Baseline heterogeneity (p < 0.0001) in 99mTc-sestamibi uptake was modest (lowest septal 65 ± 10%; maximum lateral 84 ± 5%) and also reduced with CRT, although some heterogeneity (p < 0.05) remained. The septal-to-lateral ratio increased with CRT for FDG (0.62 ± 0.12 to 0.91 ± 0.26, p < 0.001) and 99mTc-sestamibi uptake (0.77 ± 0.13 to 0.85 ± 0.16, p < 0.01). The LV end-diastolic and end-systolic volumes decreased from 293 ± 160 to 272 ± 158 ml (p < 0.05) and from 244 ± 164 to 220 ± 160 ml (p < 0.01), respectively. Ejection fraction increased from 22 ± 12% to 25 ± 13% (p < 0.01). ConclusionsGlucose metabolism is reduced more than perfusion in the septal compared with LV lateral wall in patients with DCM and LBBB. Cardiac resynchronization therapy restores homogeneous myocardial glucose metabolism with less influence on perfusion.