Myocardial perfusion and viability by positron emission tomography in infants and children with coronary abnormalities correlation with echocardiography,coronary angiography, and histopathology

AbstractObjectivesThis study was designed to assess the feasibility and accuracy of positron emission tomography (PET) imaging in infants and children.BackgroundPositron emission tomography is employed in adults for the evaluation of myocardial perfusion and the detection of myocardial viability.MethodsPerfusion and metabolism findings on PET in infants and children with suspected coronary abnormalities (age 14 days to 12 years old, mean 3.3 ± 4.0 years) were correlated with findings on coronary angiography, echocardiography, and myocardial histopathology. The segmental myocardial uptake of the flow tracer 13N-ammonia and of the glucose tracer 18F-deoxyglucose (18FDG) was graded on a five-point scale and compared with the angiographic perfusion score, with regional wall motion, and the presence of fibrosis.ResultsThere was an agreement of r = 0.72 (p < 0.05) between regional myocardial perfusion and angiography. The correlation of histopathologic changes with normal, moderately, and severely reduced segmental 13N-ammonia uptake was 87%, 60%, and 75%, respectively. Segmental myocardial 18FDG uptake and histopathologic findings were concordant in 48 (79%) of 64 segments without fibrosis; absence of viability by perfusion and metabolism imaging correlated with the presence of fibrosis in 21 (84%) of 25 segments.ConclusionsThe observed agreements between the findings on PET perfusion and metabolism imaging with those on coronary angiography, echocardiography, and histopathology support the utility and accuracy of PET for characterizing myocardial perfusion abnormalities and viability in pediatric patients

Effect of hormone replacement therapy on vasomotor function of the coronary microcirculation in post-menopausal women with medically treated cardiovascular risk factors

Aims The aim of this study was to evaluate the effect of hormone replacement therapy (HRT) on coronary vasomotor function in post-menopausal women (PM) with medically treated cardiovascular risk factors (RFs) in a cross-sectional and a longitudinal follow-up (FU) study. Methods and results Myocardial blood flow (MBF) response to cold pressor testing (CPT) and during pharmacologically induced hyperaemia was measured with positron emission tomography in pre-menopausal women (CON), in PM with HRT and without HRT, and repeated in PM after a mean FU of 24 ± 14 months. When compared with CON at baseline, the endothelium-related change in MBF (ΔMBF) to CPT progressively declined in PM with HRT and without HRT (0.35 ± 0.23 vs. 0.24 ± 0.20 and 0.16 ± 0.12 mL/g/min; P = 0.171 and P = 0.021). In PM without HRT and in those with HRT at baseline but with discontinuation of HRT during FU, the endothelium-related ΔMBF to CPT was significantly less at FU than at baseline (0.05 ± 0.19 vs. 0.16 ± 0.12 and −0.03 ± 0.14 vs. 0.25 ± 0.18 mL/g/min; P = 0.023 and P = 0.001), whereas no significant change was observed in PM with HRT (0.19 ± 0.22 vs. 0.23 ± 0.22 mL/g/min; P = 0.453). Impaired hyperaemic MBFs when compared with CON were not significantly altered from those at baseline exam. Conclusion Long-term administration of oestrogen may contribute to maintain endothelium-dependent coronary function in PM with medically treated cardiovascular RF

Improvement in coronary endothelial function is independently associated with a slowed progression of coronary artery calcification in type 2 diabetes mellitus

Aims To examine a relationship between alterations of structure and function of the arterial wall in response to glucose-lowering therapy in type 2 diabetes mellitus (DM) after a 1-year follow-up (FU). Methods and results In DM (n = 22) and in healthy controls (n = 17), coronary artery calcification (CAC) was assessed with electron beam tomography and carotid intima-media thickness (IMT) with ultrasound, whereas coronary function was determined with positron emission tomography-measured myocardial blood flow (MBF) at rest, during cold pressor testing (CPT), and during adenosine stimulation at baseline and after FU. The decrease in plasma glucose in DM after a mean FU of 14 ± 1.9 months correlated with a lower progression of CAC and carotid IMT (r = 0.48, P ≤ 0.036 and r = 0.46, P ≤ 0.055) and with an improvement in endothelium-related ΔMBF to CPT and to adenosine (r = 0.46, P ≤ 0.038 and r = 0.36, P ≤ 0.056). After adjusting for metabolic parameters by multivariate analysis, the increases in ΔMBF to CPT after glucose-lowering treatment remained a statistically significant independent predictor of the progression of CAC (P ≤ 0.001 by one-way analysis of variance). Conclusion In DM, glucose-lowering treatment may beneficially affect structure and function of the vascular wall, whereas the observed improvement in endothelium-related coronary artery function may also mediate direct preventive effects on the progression of CA

Comparison of maximal myocardial blood flow during adenosine infusion with that of intravenous dipyridamole in normal men

AbstractObjective. This study compared quantitatively the efficacy of intravenous adenosine and dipyridamole for pharmacologic induction of myocardial hyperemia.Background. Pharmacologic vasodilation is used increasingly for induction of myocardial hyperemia in conjunction with radionuclide imaging of myocardial blood flow. Although both intravenous dipyridamole and adenosine have been used, the magnitude of hyperemia induced by these agents and the hyperemia to baseline blood flow ratios have not been quantified and compared.Methods. Twenty normal volunteers were studied with dynamic positron emission tomography (PET) and intravenous nitrogen-13 ammonia. Myocardial blood flow was quantified with a two-compartment tracer kinetic model.Results. Myocardial blood flow at rest averaged 1.1 ± 0.2 ml/min per g and increased significantly to 4.4 ± 0.9 ml/min per g during adenosine and 43 ± 1.3 ml/min per g after dipyridamole administration. Hyperemia to baseline flow ratios averaged 4.3 ± 1.6 for adenosine and 4.0 ± 1.3 for dipyridamole. The average flow ratios and the maximal flows achieved were similar for both agents, but there was considerable variation in the individual response to these agents, as indicated by the range of hyperemia to baseline flow ratios (from 2.0 to 8.4 for adenosine and from 1.5 to 5.8 for dipyridamole). in addition, the hyperemic responses to dipyridamole and to adenosine differed by > 1 ml/min per g in nine subjects.Conclusions. Despite these inter- and istraindividual differences, we conclude that both agents are equally effective in producing myocardial hyperemia

Diagnostic value of PET-measured heterogeneity in myocardial blood flows during cold pressor testing for the identification of coronary vasomotor dysfunction

Background: We aimed to evaluate the diagnostic value of a positron emission tomography (PET)-measured heterogeneity in longitudinal myocardial blood flow (MBF) during cold pressor testing (CPT) and global MBF response to CPT from rest (ΔMBF) for identification of coronary vasomotor dysfunction. Methods and Results: In 35 patients CPT-induced alterations in epicardial luminal area were determined with quantitative angiography as the reference. MBF was assessed over the whole left ventricle as global MBF and regionally in the mid and mid-distal myocardium as MBF difference or MBF heterogeneity with nitrogen-13 ammonia and PET. The sensitivity and specificity of a longitudinal MBF difference during CPT in the identification of epicardial vasomotor dysfunction were significantly higher, than the global ΔMBF to CPT (88% vs 79% and 82% vs 64%, respectively; P<.05). Combining both parameters resulted in an optimal sensitivity of 100% at the expense of an intermediate specificity of 73%. The diagnostic accuracy was higher for the combined analysis than that for the MBF difference alone and global ΔMBF alone (91% vs 86% and 74%, respectively; P<.05). Conclusions: The combined evaluation of a CPT-induced heterogeneity in longitudinal MBF and the change in global MBF from rest may emerge as a new promising analytic approach to further optimize the identification and characterization of coronary vasomotor dysfunctio

Doxorubicin cardiotoxicity: Response of left ventricular ejection fraction to exercise and incidence of regional wall motion abnormalities

Gated radionuclide ventriculograms were performed to evaluate cardiac function in 53 patients who received doxorubicin treatment for various malignancies (mean dose: 449±128 mg/m 2 BSA). In fourteen patients (Group I) function was evaluated before and after treatment; there was a significant decrease of resting left ventricular ejection fraction after therapy (p<0.001). Twenty-two patients (Group II) had serial studies during treatment which also showed a significant fall of resting left ventricular ejection fraction (p<0.001). Eighteen patients in Groups I and II had supine exercise studies. A normal exercise response was maintained in the majority of patients. Exercise testing added little to the diagnostic performance when compared to serial resting studies. We found regional wall motion abnormalities (mild apical hypokinesis) at rest by visual inspection in 33 of 36 Group I and Group II patients who had received doxorubicin. In the baseline or initial study, only 4 of these patients demonstrated WMA. In 18 Group I and II patients who were exercised, 3 had wall motion abnormalities during the initial study. All of these patients demonstrated wall motion abnormalities at rest after the second study, however only 7 of 18 demonstrated abnormalities during the exercise study.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42543/1/10554_2005_Article_BF01797717.pd

948-46 Preserved Cardiac Baroreflex Control of Renal Cortical Blood Flow in Advanced Heart Failure Patients: A Positron Emission Tomography Study

Cardiac baroreflex (CBR) control of forearm blood flow (FBF) is blunted or reversed in humans with heart failure (HF). but little is known about CBR control of renal cortical blood flow (RCBF) in HF due to technical limitations. Positron emission tomography (PET) 0–15 water is a new, precise method to measure RCBF quantitatively. We compared CBR control of RCBF and FBF (venous plethysmography) in 8 patients with HF (mean age, 47±3 y, ejection fraction 0.25±0.02) and 10 normal humans (mean age 35±5 y) during CBR unloading with phlebotomy (450ml). In 5 normals, cold pressor test was used as a strong, non-baroreflex mediated stimulus to vasoconstriction.ResultsPhlebotomy decreased central venous pressure (p &lt;0.001), but did not change mean arterial pressure or heart rate in HF patients or controls. The major findings of the study are: 1) At rest, RCBF is markedly diminished in HF vs normals (2.4±0.1 vs 4.3±0.2ml/min/g, p &lt; 0.001). 2) In normal humans during phlebotomy, FBF decreased substantially (basal vs phlebotomy: 3.3±0.4 vs 2.6±0.3 ml/min/100 ml, p=0.021, and RCBF decreased slightly, but significantly (basal vs phlebotomy: 4.3±0.2 vs 4.0±0.3 ml/min/g, p=0.01). 3) The small magnitude of reflex renal vasoconstriction is not explained by the inability of the renal circulation to vasoconstrict since the cold pressor stimulus induced substantial decreases in RCBF in normals (basal vs cold pressor: 4.4±0.1 vs 3.7±0.1 ml/min/g, p=0.003). 4) In humans with heart failure during phlebotomy, FBF did not change (basal vs phlebotomy: 2.6±0.3 vs 2.7±0.2 ml/min/100 ml, p=NS), but RCBF decreased slightly but significantly (basal vs phlebotomy: 2.4±0.1 vs 2.1±0.1 ml/min/g, p=0.01). Thus, in patients with heart failure, there is an abnormality in cardiopulmonary baroreflex control of the forearm circulation, but not the renal circulationConclusionThis study 1) shows the power of PET to study physiologic and pathophysiologic reflex control of the renal circulation in humans, and 2) describes the novel finding of selective dysfunction of cardiac baroreflex control of the forearm circulation, but its preservation of the renal circulation, in patients with heart failur