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S R Bergmann

Publications and source records attributed to S R Bergmann.

136 records · Page 8Linked to original sources
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Clinical applications of assessments of myocardial substrate utilization with positron emission tomography.

Positron emission tomography (PET) permits sequential, noninvasive assessment of myocardial perfusion and metabolism. Based on the pattern of substrate use, clinical studies have utilized PET to define the location and extent of myocardial infarction, to identify areas of jeopardized but viable myocardium, and to assess the metabolic response of the myocardium to pharmacological therapy as well as to interventions such as coronary thrombolysis and coronary artery bypass surgery. The ability to noninvasively assess specific metabolic pathways should facilitate our understanding of normal myocardial metabolism, its perturbations with cardiac disease, and thereby improve the diagnosis and treatment of the biochemical processes underlying cardiac dysfunction.

Amino Acids↗
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Normal limits for left ventricular ejection fraction and volumes estimated with gated myocardial perfusion imaging in patients with normal exercise test results: influence of tracer, gender, and acquisition camera.

BACKGROUND: Myocardial imaging with tracers such as technetium-99m sestamibi or thallium-201 is extensively used as a means of measuring myocardial perfusion. With gated acquisition, these tracers can also be used as a means of measuring left ventricular ejection fraction (EF) and end diastolic and end systolic volumes (EDV and ESV, respectively). The objective of this study was to determine the normal range of EF, EDV, and ESV and to evaluate differences caused by either the tracer used, the gender of the patient, or the acquisition camera used. METHODS AND RESULTS: A total of 1513 consecutive patients (mean age, 60+/-12 years [SD]) who had normal results on Bruce exercise tests had either Tc-99m sestamibi (n = 884) or Tl-201 (n = 629) injected at peak stress. Although all patients were referred for the evaluation of chest pain or dyspnea and many had cardiac risk factors, all had normal exercise capacity corrected for age, no electrocardiographic signs of ischemia, normal results on perfusion scans, and normal wall motion determined by means of quantitated gated single photon emission computed tomography (QGS). Scans were acquired on 1 of 3 different cameras. The mean EF for all patients who had gated Tc-99m sestamibi scans was 63% +/- 9%, not different from patients who had gated Tl-201 scans (63% +/- 9%). However, when the gender of the patient was considered, the mean EF for women was 66% +/- 8% with Tc-99m sestamibi (n = 519), higher than the mean EF for men (58% +/- 8%, n = 365, P<.0001). Similarly, the mean EF for women studied with Tl-201 (67% +/- 8%, n = 326) was higher than that of men (59% +/- 7%, n = 303,P<.0001). Patients with diabetes mellitus (n = 153) had a slightly reduced EF (62% +/- 10%, P<.001). In a subset of 240 patients, 140 patients studied with Tc-99m sestamibi and 100 studied with Tl-201, the EDV and ESV for women (n = 124) was estimated by means of QGS to be lower (57 +/- 17 mL and 19 +/- 11 mL, respectively) than those for men (74 +/- 22 mL-and 29 +/- 13 mL, respectively; n = 116; P<.001 for each comparison). No clinically significant differences in EF or volumes were noted based on tracers used or acquisition camera. For patients with normal results on exercise treadmill tests and perfusion imaging, the lower limit of normal for EF with gated perfusion imaging with QGS was 50% for women and 43% for men. For EDV and ESV, the upper limit of normal was 91 mL and 40 mL, respectively, for women and 119 mL and 55 mL, respectively, for men. CONCLUSIONS: No significant differences related to either tracer or acquisition camera used were noted for EF, suggesting equivalency for clinical trials for patients with normal results on exercise tests. However, EF, EDV, and ESV determined by means of gated perfusion imaging need to be corrected for gender.

Adult↗
PubMedDate not supplied

Tracer kinetic modeling in nuclear cardiology.

The introduction of tracer kinetic modeling techniques in conjunction with nuclear imaging has allowed the assessment of physiologic processes in the myocardium in a noninvasive and quantitative manner. Alongside the development of novel radiopharmaceuticals for both positron emission tomography and single photon emission computed tomography is the clarification of their pharmacology, pharmacokinetics, and modeling strategies for assessment of physiologic rates from imaging data. Image analysis and tracer kinetic modeling techniques used in nuclear cardiology must address unique considerations related to the heart. The most commonly used tracers and modeling techniques are presently discussed, with particular attention given to methods that allow absolute quantitation of physiologic processes. The applications of these techniques are obvious in research protocols and may find more use in future clinical studies.

Coronary Circulation↗
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Failure of right precordial electrocardiography during stress testing to identify coronary artery disease.

BACKGROUND: It has been reported that the use of right precordial leads results in the same diagnostic accuracy as thallium-201 exercise scintigraphy for the detection of coronary artery disease (CAD). The aim of this study was to evaluate the utility of right precordial leads in the detection of CAD. METHODS AND RESULTS: We evaluated 900 consecutive patients (514 men, 386 women) ranging in age from 39 to 84 years (mean +/- SD, 64 +/- 11 years). Seven hundred forty patients underwent treadmill exercise testing, and 160 underwent pharmacologic stress testing for the diagnosis of chest pain or dyspnea. All received either Tl-201 or technetium-99m sestamibi during stress. During stress testing, the ECG was recorded every minute with 12 limb and left precordial leads and 3 right precordial leads (V(3)R, V(4)R, and V(5)R). The electrocardiogram was considered positive when the ST segment was either elevated or depressed by at least 0.1 mV at 80 ms after the J point, and results were also compared with single photon emission computed tomography myocardial perfusion imaging results. Of the 900 patients, 158 had significant positive changes in the limb or left precordial leads. Only 4 patients had positive changes in the right precordial leads (Fisher exact test, P <.001). Of the patients who had positive electrocardiographic changes, 95 (60%) had abnormal myocardial perfusion scans, with 91 in patients with normal right precordial leads. All 4 patients with ischemic changes in the right precordial leads had abnormal scans, but the left leads were also positive. Three hundred seventy-three of 900 patients (41%) had abnormal scans with no electrocardiographic evidence of ischemia. CONCLUSIONS: Our experience is far different than that published and suggests that the use of right precordial leads during stress testing fails to provide the same diagnostic accuracy as either the standard left-sided electrocardiography or myocardial perfusion imaging for the detection of CAD.

Adult↗
PubMedDate not supplied

Incidence of major cardiovascular events in black patients with normal myocardial stress perfusion study results.

BACKGROUND: Previous studies have shown that the risk of major cardiovascular events at 1 year is less than 1% in patients with normal myocardial stress perfusion study results. However, the racial distribution of patients enrolled in these studies is not known. Hence, the prognostic value of normal stress perfusion study results in black patients is not well established. Our objective was to determine the incidence of major cardiovascular events in black patients with normal stress perfusion study results over a 12-month period. METHODS AND RESULTS: We searched the nuclear cardiology database at our institution for all black patients who had normal stress perfusion study results between January 1990 and December 1996. We excluded patients with a history of coronary revascularization, valvular heart disease, cardiomyopathy, congenital heart disease, left bundle branch block, or pre-excitation syndrome. Patients were followed up for at least 12 months from the time of inclusion. A total of 592 patients were enrolled and were followed up for 18 +/- 6 months (mean +/- SD). Of these, 388 underwent treadmill exercise testing, 155 underwent dipyridamole stress testing, and the remainder underwent dobutamine stress testing. Perfusion studies were performed in all patients with thallium 201 single photon emission computed tomography imaging. During the follow-up period, 11 cardiac deaths and 7 myocardial infarctions (MIs) occurred. The incidence of cardiac deaths was 1.2% per year, and that of nonfatal MIs was 0.8% per year. The total incidence of major cardiovascular events was 2% per year. In patients who underwent treadmill exercise testing, the incidence of major cardiovascular events was 1% per year. Performance of a pharmacologic stress test and a prior MI were significantly associated with death or nonfatal MI (P <.05). CONCLUSIONS: The overall incidence of major cardiovascular events in black patients after normal exercise perfusion study results were obtained was low (1%). However, black patients who had normal perfusion study results but underwent pharmacologic stress testing or had a history of MI were at intermediate risk. These patients require close surveillance for major cardiovascular events.

Adult↗
PubMedDate not supplied

Quantitation of myocardial blood flow with H2 15O and positron emission tomography: assessment and error analysis of a mathematical approach.

Quantitation of regional myocardial blood flow (MBF) in absolute terms with positron emission tomography (PET) has been difficult to achieve in part because of errors induced by the relatively low spatial resolution of current tomographic instruments. We previously demonstrated that MBF could be accurately measured over a wide range of flows after intravenous administration of H2 15O when the arterial input function and myocardial radiotracer content were measured directly. To extend this quantitative approach for noninvasive estimates of MBF with PET. We recently developed and implemented a novel mathematical approach whereby partial volume and spillover effects were estimated along with flow within the operational one-compartment flow equation. Noninvasive estimates of flow correlated closely with flow measured directly with radiolabeled microspheres. In the present study, with the use of a commercially available cardiac phantom, we assessed our ability to obtain true time-activity curves from observed PET data contaminated by partial volume and spillover effects. Computer simulations demonstrated that the approach developed is relatively insensitive to most potential sources of error, but is sensitive to timing discrepancies between the arterial input function and the tissue time-activity curve. Implementation of this approach provides accurate quantitation of regional MBF in absolute terms and should be useful in noninvasive evaluation of the efficacy of treatments designed to enhance nutritional perfusion in human subjects.

Coronary Circulation↗
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Clinical applications of myocardial perfusion assessments made with oxygen-15 water and positron emission tomography.

Positron emission tomography is an intrinsically quantitative tool which permits the quantitative assessment (i.e., in ml/g/min) of regional myocardial perfusion. Oxygen-15-labeled water is the only positron-emitting flow tracer which is freely diffusible within the myocardium. It has been used extensively to define normal myocardial perfusion physiology, as well as to delineate the effects of numerous cardiac diseases on myocardial perfusion and to assess the efficacy of therapeutic interventions. This brief review summarizes the major observations that have been made in humans using oxygen-15 water and positron emission tomography for quantitative estimation of regional myocardial perfusion.

Blood Flow Velocity↗
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The super PET 3000-E: a PET scanner designed for high count rate cardiac applications.

OBJECTIVE: Mathematical models for the delineation of regional myocardial perfusion and metabolism with PET require faithful reconstruction of arterial and myocardial time-activity curves following administration of radiotracers. High temporal resolution is often required in such measurements. Many commercially available tomographs exhibit long dead times that limit their count rate capabilities. To overcome these limitations, we developed and tested a whole-body tomographic device (Super PET 3000-E) with high count rate capabilities. The use of cesium fluoride scintillation detectors coupled with a one-to-one detector photomultiplier configuration reduces the system resolving and dead times. MATERIALS AND METHODS: The Super PET 3000-E was subjected to a series of tests with phantoms to determine its resolution, sensitivity, linearity, count rate capabilities, dead time, and random coincidence contribution. RESULTS: The system sensitivity is 136 kcounts/s/microCi/ml and its transverse and longitudinal resolutions are 8.5 and 10.5 mm full width at half-maximum, respectively. The system can easily record a total event rate of 2.0 Mcounts/s with minimal dead time loss and excellent linearity. CONCLUSION: The system fulfills its design goals and allows the very high count rate performance needed for the application of the physiological models used in our cardiac studies.

Algorithms↗