Search

The 12th International Conference on Nuclear Cardiology and Cardiac CT was held from 3 to 5 May 2015 in Madrid, Spain. In this article, the three Congress Program Committee Chairs summarize selected highlights of the presented abstracts.

a Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD b Department of Medicine (Cardiology Division), Massachusetts General Hospital, Harvard Medical School, Boston, MA c Department of Medicine (Division of Cardiology), University of Rochester Medical Center, Rochester, NY d Department of Cardiology, Sismanoglio Hospital, Athens, Greece e Division of Cardiovascular Disease, Department of Medicine, University of Alabama at Birmingham and Birmingham Veterans Affairs Medical Center, Birmingham, AL f Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD g Departments of Medicine (Division of Cardiology) and Imaging Sciences (Nuclear Medicine), University of Rochester Medical Center, Rochester, NY

The mechanisms that determine chronic left ventricular dysfunction in coronary artery disease (in particular, critical reductions in coronary artery blood flow leading to hibernating myocardium) may affect the ability of the myocardium to respond to inotropic stimulation with dobutamine. This study was designed to investigate the relationship between resting myocardial blood flow and contractile reserve in patients with coronary artery disease and chronic left ventricular dysfunction.Twenty-three patients (21 men and 2 women; age 61 +/- 9 years) underwent transesophageal echocardiography during infusion of dobutamine (2.5 microg/kg to 40 microg/kg per minute) and positron emission tomography (PET) with 150-water (9 patients) or 13N-ammonia (14 patients). Systolic wall thickening at each dose of dobutamine and resting myocardial blood flow were quantitatively analyzed in 8 anatomically matched regions at mid-ventricular level. Myocardial regions with preserved contraction had higher blood flow compared with regions with basal dyssynergy (0.99 +/- 0.3 vs 0.65 +/- 0.3 mL/min/gm; P.0001). Among myocardial regions with preserved resting contraction, no relation was observed between blood flow and the response to dobutamine (r = 0.06). In contrast, among myocardial regions with diminished resting contraction, a significant correlation was observed between resting blood flow and contractile reserve (r = 0.53; P.0001). The maximum increase in percent systolic wall thickening with dobutamine was 32.8% +/- 14% in regions with normal blood flow, 21.5% +/- 17% in regions with mildly to moderately reduced blood flow, and 10.7% +/- 10% in regions with severely reduced blood flow (P.0001).These findings emphasize the importance of resting myocardial blood flow for the preservation of contractile reserve in patients with coronary artery disease and left ventricular dysfunction. Because a positive inotropic response to dobutamine is more likely to occur in dyssynergic regions with preserved rather than reduced myocardial blood flow, regional perfusion may determine in which circumstances dobutamine echocardiography contributes to the assessment of myocardial viability.

OBJECTIVES In this study we determined whether 13N-ammonia uptake measured late after injection provides additional insight into myocardial viability beyond its value as a myocardial blood flow tracer. BACKGROUND Myocardial accumulation of 13N-ammonia is dependent on both regional blood flow and metabolic trapping. METHODS Twenty-six patients with chronic coronary artery disease and left ventricular dysfunction underwent prerevascularization 13N-ammonia and 18F-deoxyglucose (FDG) positron emission tomography, and thallium single-photon emission computed tomography. Pre- and postrevascularization wall-motion abnormalities were assessed using gated cardiac magnetic resonance imaging or gated radionuclide angiography. RESULTS Wall motion improved in 61 of 107 (57%) initially asynergic regions and remained abnormal in 46 after revascularization. Mean absolute myocardial blood flow was significantly higher in regions that improved compared to regions that did not improve after revascularization (0.63 ± 0.27 vs. 0.52 ± 0.25 ml/min/g, p CONCLUSIONS These data suggest that beyond its value as a perfusion tracer, late 13N-ammonia uptake provides useful information regarding functional recovery after revascularization. The parallel relationship among 13N-ammonia, FDG, and thallium uptake supports the concept that uptake of 13N-ammonia as measured from the late images may provide important insight regarding cell membrane integrity and myocardial viability.

Background —New high-energy collimators for single photon emission computed tomography (SPECT) cameras have made imaging of positron-emitting tracers, such as [ 18 F]fluorodeoxyglucose ( 18 FDG), possible. We examined differences between SPECT and PET technologies and between 18 FDG and thallium tracers to determine whether 18 FDG SPECT could be adopted for assessment of myocardial viability. Methods and Results —Twenty-eight patients with chronic coronary artery disease (mean left ventricular ejection fraction [LVEF]=33±15% at rest) underwent 18 FDG SPECT, 18 FDG PET, and thallium SPECT studies. Receiver operating characteristic curves showed overall good concordance between SPECT and PET technologies and thallium and 18 FDG tracers for assessing viability regardless of the level of 18 FDG PET cutoff used (40% to 60%). However, in the subgroup of patients with LVEF≤25%, at 60% 18 FDG PET threshold value, thallium tended to underestimate myocardial viability. In a subgroup of regions with severe asynergy, there were considerably more thallium/ 18 FDG discordances in the inferior wall than elsewhere (73% versus 27%, P 18 FDG by SPECT and PET was compared in 137 segments exhibiting severely irreversible thallium defects (scarred by thallium), 59 (43%) were viable by 18 FDG PET, of which 52 (88%) were also viable by 18 FDG SPECT. However, of the 78 segments confirmed to be nonviable by 18 FDG PET, 57 (73%) were nonviable by 18 FDG SPECT ( P Conclusions —Although 18 FDG SPECT significantly increases the sensitivity for detection of viable myocardium in tissue declared nonviable by thallium (to 88% of the sensitivity achievable by PET), it will occasionally (27% of the time) result in falsely identifying as viable tissue that has been identified as nonviable by both PET and thallium.

Background We have shown that the angiogenic peptides basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) enhance canine coronary collateral development when administered for ≥4 weeks. bFGF, a pluripotent mitogen of mesodermally derived cells, could theoretically exacerbate neointimal smooth muscle cell hyperplasia, a fundamental component of atherosclerosis. VEGF, an endothelial cell–specific mitogen and vascular permeability factor, could have deleterious effects related to vascular hyperpermeability. The present investigation had two aims: (1) to ascertain whether brief (7-day) systemic arterial treatment with bFGF or VEGF would improve myocardial collateral perfusion and (2) to determine whether these peptides induce neointimal accumulation in vivo. Methods and Results Dogs were subjected to ameroid-induced occlusion of the left circumflex coronary artery and randomized to bFGF 1.74 mg (n=9), VEGF 0.72 mg (n=9), or saline (n=10) as a daily left atrial bolus (days 10 to 16). Additional dogs were randomized to VEGF 0.72 mg (n=6) or saline (n=5); however, treatment was delayed by 1 week. Coincident with the institution of treatment, all dogs underwent balloon denudation injury of the iliofemoral artery. bFGF markedly increased maximal collateral flow but did not exacerbate neointimal accumulation. VEGF had no discernible effect on maximal collateral flow, but it exacerbated neointimal thickening after vascular injury. Conclusions Short-term treatment with bFGF enhanced collateral development without increasing neointimal accumulation at sites of vascular injury. Although VEGF did not increase collateral development as administered in this study, it significantly exacerbated neointimal accumulation. These data provide support for the clinical investigation of bFGF in selected patients with ischemic heart disease.

In recent years, the use of single photon emission computed tomography (SPECT) has been proposed for gated blood pool scans in order to assess left ventricular function. By constructing a beating heart phantom, the authors confined that SPECT may be superior to planar imaging for visual assessment of wall motion defects. Further, in data from five patients with coronary artery disease, a correlation was found between quantitative measures of heart wall defects from SPECT gated blood pool images and the magnitude of PET blood flow defects. Finally, the authors investigated the effects of statistical noise, background and attenuation on ejection fraction and amplitude calculations from SPECT slices. Statistical noise and background were found to produce very small effects while attenuation had a small but measurable effect on the amplitude map and no effect on ejection fraction. >

Background —In patients with coronary artery disease, stress-redistribution-reinjection thallium scintigraphy provides important information regarding myocardial ischemia and viability. Although both reversible and mild-to-moderate irreversible thallium defects retain metabolically active, viable myocardium, we hypothesized that stress-induced reversible thallium defects may better differentiate reversible from irreversible regional left ventricular dysfunction after revascularization. Methods and Results —Twenty-four patients with chronic coronary artery disease underwent prerevascularization and postrevascularization exercise-redistribution-reinjection thallium single photon emission CT, gated MRI, and radionuclide angiography. After revascularization, mean left ventricular ejection fraction increased from 30±9% to 37±13% at rest ( P P P P =NS). Furthermore, when asynergic regions were grouped according to the final thallium content, at 60% threshold value, functional recovery was observed in 83% of regions with reversible defects compared with 33% of regions with mild-to-moderate irreversible defects ( P Conclusions —These findings suggest that although both reversible and mild-to-moderate irreversible thallium defects after stress retain viable myocardium, the identification of reversible thallium defect on stress in an asynergic region more accurately predicts recovery of function after revascularization. Even at a similar mass of viable myocardial tissue (as reflected by the final thallium content), the presence of inducible ischemia is associated with an increased likelihood of functional recovery.

Recent advances in SPECT and PET technology permit ECG gating of tomographic cardiac images, allowing simultaneous measurement of 3D cardiac ventricular function with perfusion/metabolism. Extracting indices of regional function from these 4D data sets (3D space + time) remains a challenge. All approaches currently used to quantitate gated tomographic sequences deal separately with the spatial and temporal data. As functional information is based on close coupling between spatial and temporal changes, it could be beneficial to produce an image combining spatial and temporal information. In this paper we describe a method for producing such spatialtemporal images and, using gated FDG PET data, test the ability of these images to improve visual and quantitative assessment of cardiac function. Other potential schemes to make use of the space-time nature of this new representation are also discussed.

OBJECTIVE: To study changes in antibody titres and antibody avidities to putative periodontal pathogens in patients with resistant periodontitis and to compare these findings with the result of culture of these pathogens. SUBJECTS AND METHODS: Patients meeting strict clinical criteria in whom periodontal therapy had failed to prevent disease progression were studied microbiologically and immunologically over a 75-week period. Particular reference was made to the isolation of Actinobocillus actinomycetemcomitons (Aa) and Porphyromonos gingivalis (Pg) together with changes in antibody titres and avidities to these organisms between baseline examination and week 75. RESULTS: Pg was eliminated following antibiotic treatment but metronidazole and amoxycillin therapy failed to remove Aa in all cases. Antibody avidities to these pathogens were higher in patients than in matched controls but no change in avidity was noted during the course of treatment. Most antibody titres were not significantly higher in patients than in controls. CONCLUSIONS: Continued disease progression characterised these patients who, nevertheless, mounted an immune response to the periodontal pathogens but this appeared to be inadequate to stop the disease.