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Background In patients with heart failure and reduced left ventricular ejection fraction (LVEF), the effect of upgrading from right ventricular (RV) apical to biventricular pacing on RV and left ventricular (LV) volumes and ejection fraction (EF) is unknown. Also, the relationship of symptom improvement after biventricular upgrade to RV and LV volumes and EF has not been clarified.

Careful, systematic inspection of planar projection and tomographic images is essential as extracardiac findings and non-perfusion abnormalities may be present and on occasion account for the patient's symptoms. Two case histories and the corresponding images are presented below in which a stress myocardial perfusion single photon emission computed tomography (SPECT) study was performed and the diagnosis of a pericardial effusion was made. Although pericardial effusions are typically diagnosed by other imaging modalities (echocardiography and computed tomography) they can also be identified by radionuclide imaging techniques. Findings on planar projection and gated SPECT include the appearance of a "halo" of reduced tracer concentration surrounding the heart on both the rest and stress planar projection and tomographic images, and a "rocking" motion of the heart on gated images.

INTRODUCTION Cardiac resynchronization therapy (CRT) can improve left ventricular (LV) hemodynamics and function. Recent data suggest the energy cost of such improvement is favorable. The effects of sequential CRT on myocardial oxidative metabolism (MVO(2)) and efficiency have not been previously assessed. METHODS AND RESULTS Eight patients with NYHA class III heart failure were studied 196 +/- 180 days after CRT implant. Dynamic [(11)C]acetate positron emission tomography (PET) and echocardiography were performed after 1 hour of: 1) AAI pacing, 2) simultaneous CRT, and 3) sequential CRT. MVO(2) was calculated using the monoexponential clearance rate of [(11)C]acetate (k(mono)). Myocardial efficiency was expressed in terms of the work metabolic index (WMI). P values represent overall significance from repeated measures analysis. Global LV and right ventricular (RV) MVO(2) were not significantly different between pacing modes, but the septal/lateral MVO(2) ratio differed significantly with the change in pacing mode (AAI pacing = 0.696 +/- 0.094 min(-1), simultaneous CRT = 0.975 +/- 0.143 min(-1), and sequential CRT = 0.938 +/- 0.189 min(-1); overall P = 0.001). Stroke volume index (SVI) (AAI pacing = 26.7 +/- 10.4 mL/m(2), simultaneous CRT = 30.6 +/- 11.2 mL/m(2), sequential CRT = 33.5 +/- 12.2 mL/m(2); overall P < 0.001) and WMI (AAI pacing = 3.29 +/- 1.34 mmHg*mL/m(2)*10(6), simultaneous CRT = 4.29 +/- 1.72 mmHg*mL/m(2)*10(6), sequential CRT = 4.79 +/- 1.92 mmHg*mL/m(2)*10(6); overall P = 0.002) also differed between pacing modes. Compared with simultaneous CRT, additional changes in septal/lateral MVO(2), SVI, and WMI with sequential CRT were not statistically significant on post hoc analysis. CONCLUSION In this small selected population, CRT increases LV SVI without increasing MVO(2), resulting in improved myocardial efficiency. Additional improvements in LV work, oxidative metabolism, and efficiency from simultaneous to sequential CRT were not significant.

Background: Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) can be utilized to assess myocardial viability. The objective of this study was to assess FDG PET image quality during the hyperinsulinemic euglycemic clamp (HE clamp) in patients with and without diabetes referred for myocardial viability assessment. Methods: Consecutive FDG PET viability scans at Mayo Clinic from June 2000Nov 2003 were reviewed retrospectively. Scans were performed using static acquisition. Image quality was visually assessed at the time of reading by two experienced observers. Image quality was also assessed by calculating the myocardium to blood pool (M/B) activity ratio (mean activity from regions of interest over normal myocardium and the LV cavity, averaged over three midventricular slices). Results: 81 of 82 FDG PET scans utilized the HE clamp; 39 Type 2 diabetics (DM2), 2 Type 1 diabetics, and 40 non-diabetics (Non-DM). By visual assessment, images were inadequate in 1 DM2 (M/B=1.6) and 1 Non-DM (M/B=1.8). All other patients (97%) had adequate images (M/B range 2.2–30.0). DM2 Non-DM P-Value Age, yrs 67.4 ± 10.3 64.8 ± 13.0 NS BM, kg/m 2 2 30.9 ± 5.9 27.7 ± 5.4 0.02 LVEF, % 27.3 ± 9.5 29.8 ± 11.0 NS Blood glucose before clamp, mg/dL 141.1 ± 34.6 101.7 ± 13.3 0.0001 Clamp start to FDG injection, min 155.7 ± 71.8 104.7 ± 35.1 0.0001 FDG injection to scan, min 39.8 ± 10.9 39.8 ± 16.1 NS Blood glucose during scan, mg/dL 91.6 ± 10.5 85.4 ± 13.3 0.03 Dextrose infusion during scan, mg/kg/min 3.1 ± 1.6 3.9 ± 1.6 0.02 M/B ratio 6.5 ± 4.6 8.1 ± 4.6 0.06 Conclusions: HE clamp yielded adequate image quality in >97% of both diabetic and non-diabetic patients referred for FDG PET myocardial viability assessment. HE clamp time was longer in diabetics, primarily due to higher baseline glucose and longer time until FDG injection.