Michael P. White

Functional assessment with electrocardiographic gated single-photon emission computed tomography improves the ability of technetium-99m sestamibi myocardial perfusion imaging to predict myocardial viability in patients undergoing revascularization.

This study evaluates the use of electrocardiographic (ECG) gated single-photon emission computed tomographic (SPECT) myocardial perfusion imaging for the prediction of viability in patients undergoing revascularization, who have coronary disease and left ventricular dysfunction. Fifty patients underwent technectium-99m (Tc-99m) sestamibi ECG gated SPECT imaging preoperatively at rest and 1 week after revascularization, whereas 36 (72%) also underwent imaging 6 weeks after revascularization. Images were interpreted by the consensus of 3 experienced readers without knowledge of patient identity or time of imaging (pre- or postrevascularization) for perfusion and wall motion using a 17-segment model. Results of perfusion alone were compared with perfusion and wall motion combined. One hundred five coronary artery territories were revascularized, 96 of which were viable and 9 nonviable. Perfusion alone predicted 87 to be viable and 18 nonviable (sensitivity 86%, specificity 55%, positive predictive value 95%, negative predictive value 28%, and overall accuracy 85%). Perfusion and wall motion combined identified 95 territories to be viable (sensitivity 95%; p <0.025; specificity 55%, positive predictive value 96%, negative predictive value 50%, and overall accuracy 91%; p <0.05). Thus, Tc-99m sestamibi ECG gated SPECT myocardial perfusion imaging at rest allows assessment of both perfusion and wall motion, which significantly improves the sensitivity and overall accuracy for determination of viability in comparison with perfusion alone.

Comparison of acute rest myocardial perfusion imaging and serum markers of myocardial injury in patients with chest pain syndromes

BackgroundNewer diagnostic modalities such as serum markers and acute rest myocardial perfusion imaging (MPI) have been evaluated diagnostically in patients with chest pain in the emergency department (ED), but never concurrently. We compared these two modalities in distinguishing patients in the ED with symptomatic myocardial ischemia from those with non-cardiac causes.MethodsSerum markers and acute technetium-99m sestamibi/tetrofosmin rest MPI were obtained in 75 patients admitted to the ED with chest pain and nondiagnostic electrocardiograms. Venous samples were drawn at admission and 8 to 24 hours later for total creatine kinase, CK-MB fraction, troponin T, troponin I, and myoglobin. Three nuclear cardiologists performed blinded image interpretation. Coronary artery disease (CAD) was confirmed either by diagnostic testing or by the occurrence of myocardial infarction (MI).ResultsAcute rest MPI results were abnormal in all 9 patients with MI. An additional 26 patients had objective evidence of CAD confirmed by diagnostic testing. The sensitivity of acute rest MPI for objective evidence of CAD was 73%. Serum troponin T and troponin I were highly specific for acute MI but had low sensitivity at presentation. Individual serum markers had very low sensitivity for symptomatic myocardial ischemia alone. In the multivariate regression model, only acute rest MPI and diabetes were independently predictive of CAD.ConclusionAt the time of presentation and 8 to 24 hours later, acute rest MPI has a better sensitivity and similar specificity for patients with objective evidence of CAD when compared with serum markers.

Impact of limited treadmill exercise on adenosine Tc-99m sestamibi single-photon emission computed tomographic myocardial perfusion imaging in coronary artery disease

Limited exercise combined with dipyridamole increases myocardial perfusion defect severity compared with dipyridamole alone. The impact of limited exercise combined with adenosine on myocardial perfusion defect severity is unknown. This study compares myocardial perfusion defect severity with adenosine alone and adenosine combined with limited exercise. Thirty-two patients with coronary artery disease underwent on separate days and in randomized order technetium-99m sestamibi (25 to 30 mCi) single-photon emission computed tomographic imaging at rest, after adenosine (140 microg/kg/min x 6 minutes), and after adenosine (140 microg/kg/min x 4 minutes) during 6 minutes of modified Bruce treadmill exercise (adenosine-exercise). Radiopharmaceutical was injected at 3 and 5 minutes during adenosine and adenosine-exercise, respectively. Images were interpreted by a consensus agreement of 3 nuclear cardiologists without knowledge of patient identity, stress protocol, or clinical data using a 17-segment model and 5-point scoring system. A summed stress score (SSS), summed rest score (SRS), and summed difference (SSS-SRS) score (SDS) were calculated for each image. Peak stress heart rate and rate-pressure product were higher for adenosine-exercise than adenosine (102 +/- 19 vs 81 +/- 11 beats/min and 13,972 +/- 4,265 vs 10,623 +/- 2,131, respectively; both p <0.001). Sensitivity for detection of > or = 50% coronary stenosis was 75% and 72% for adenosine-exercise and adenosine, respectively (p = NS). There were no differences in SSS and SDS between adenosine-exercise and adenosine (8.2 +/- 5.9 vs 8.1 +/- 6.3 and 4.9 +/- 4.1 vs 5.2 +/- 4.6, respectively; both p = NS). Thus, in patients with coronary artery disease, limited treadmill exercise combined with adenosine does not increase myocardial perfusion defect severity compared with standard adenosine technetium-99m sestamibi single-photon emission computed tomographic myocardial perfusion imaging.

Pharmacologic stress testing: Understanding the options

ConclusionPharmacologic stress testing is not always the last-resort method of evaluating a patient. There are circumstances in which pharmacologic testing is preferred to exercise—for example, in the first days after acute myocardial infarction, when exercise testing is contraindicated. However, several studies have demonstrated that the safety and efficacy of dipyridamole stress testing within the first 48 hours after a myocardial infarction provides valuable information to aid in the decision to refer the patient for a more invasive procedure or to take a conservative approach. Second, a phenomenon associated with left bundle-branch block is anteroseptal defects during exercise treadmill testing, which are less commonly seen with vasodilator stress.The choice of pharmacologic stress agent remains with the referring physician, taking into account the known side effects, the patients ability to tolerate them, and the desired information. All pharmacologic stress agents discussed yield similar diagnostic accuracy for detecting coronary artery disease, although vasodilators produce higher flow rates than catecholamines. Furthermore, the addition of low-level exercise improves the target-to-background ratio and reduces side effects. Most importantly, pharmacologic stress offers physicians a means to evaluate a patient who is unable to exercise adequately or not at all.

Dipyridamole-dobutamine stress with Tc-99m sestamibi tomographic myocardial perfusion imaging

In 66 patients unable to exercise referred for pharmacologic stress single-photon emission computed tomographic myocardial perfusion imaging, a moderate dose of dobutamine was combined with intravenous dipyridamole and the results were compared with standard intravenous dipyridamole stress. The combined stress protocol resulted in increased defect size and reversibility with technetium-99m sestamibi single-photon emission computed tomographic myocardial perfusion imaging.

Role of the technologist in nuclear cardiology

ConclusionIt is the responsibility of all technologists to maintain the level of quality and professionalism the field of nuclear cardiology demands. As health care continues to change and become more complex, it is important that we remain an integral part of the diagnostic process. Technologists need to stay informed and actively involved to ensure the institution they are working in is state of the art, allowing the performance of the most upto-date procedures, and that these procedures are performed with the highest level of quality. The ASNC and the editorial staff at the Journal of Nuclear Cardiology support the addition of this Technologist Section to the Journal. It is our goal as coeditors to use these pages to bring valuable information about our field to the technologists who would otherwise not be receiving it and to encourage all technologists practicing nuclear cardiology to be involved in its success. We will strive to bring you the issues that are concerning technologists today in all aspects of nuclear cardiology. We hope that all technologists will be as interested as we are in maintaining the level of professionalism and respect that our predecessors worked so hard to achieve.We welcome your input. If you are a technologist practicing nuclear cardiology and are interested in writing an article, reviewing articles from your peers, or suggesting topics to be covered, we encourage you to contact us through the editorial office of the Journal of Nuclear Cardiology.

Acute myocardial perfusion imaging for the technologist

ConclusionAcute myocardial perfusion imaging involves careful planning from the nuclear medicine or nuclear cardiology laboratory to ensure optimal results are achieved. The role of the technologist is to ensure a high-quality study is performed on every patient who is referred to the laboratory. This is one of the most important roles because the decision for further evaluation can be based on the interpretation of the acute images. When acute myocardial perfusion imaging is used appropriately, in conjunction with standard methods of evaluation for patients presenting to the emergency department with chest pain syndromes perceived to be cardiac in origin, it can be of great benefit. It offers a more definitive diagnosis of chest pain syndromes and can be used to reduce the expense of otherwise costly hospital stays, even in patients with moderate risk of ischemic heart disease.