A Proposal for an Advanced Cardiovascular Imaging Training Track

Cardiovascular (CV) imaging has experienced major growth and technological advances with respect to the long-standing traditional cardiac imaging procedures of echocardiography and nuclear cardiology, the emergence of cardiac computed tomography and magnetic resonance imaging in clinical practice, and multimodality and molecular imaging as new technologies. Therefore, it is perhaps timely to change the training paradigm for fellows interested in emphasizing CV imaging as a subspecialty in their professional careers and desiring extensive training in all CV imaging modalities. Proposed is the establishment of a formal fourth year of training leading to board certification in advanced CV imaging. Areas of training would include the acquisition of knowledge of physics and instrumentation related to the various imaging modalities, interpretation and quantitation of imaging variables, multimodality imaging technology, molecular and vascular imaging, and clinical guidelines with appropriateness criteria for all technologies. The training track would lead to an American Board of Internal Medicine examination for a Certificate of Added Qualification, similar to that for subspecialization in electrophysiology and interventional cardiology, with noninvasive cardiologists who have already completed fellowship training given the opportunity to sit for an examination on the basis of predetermined eligibility criteria. One benefit of this CV imaging subspecialty track that provides cardiologists with expertise in all imaging modalities is the capability to select the best modality for the clinical indication and to independently interpret multimodality imaging studies. Its rigorous didactic and procedural requirements would enhance quality of CV imaging, enhance research, and increase the speed with which new discoveries are translated into practice. This ultimately would yield better patient outcomes

Stress Myocardial Perfusion Imaging for Assessing Prognosis: An Update

A strength of nuclear myocardial perfusion imaging (MPI) is the wealth of prognostic data accumulated over 30 years of experience with this technique. Nuclear MPI can predict outcomes and guide revascularization decisions in symptomatic patients and is well validated in special populations such as patients with diabetes and chronic renal disease. Known limitations, such as underestimation of ischemia and radiation burden, are being progressively reduced through advances such as positron emission tomography absolute flow quantification and fusion with computed tomography, new camera hardware and software, and stress-only protocols. Advanced statistical techniques and increasing focus on comparative effectiveness and appropriateness will continue to optimize nuclear cardiology going forward

Assessment of regional myocardial blood flow and regional fractional oxygen extraction in dogs, using 15O-water and 15O-hemoglobin

A new approach to the assessment of regional myocardial blood flow and fractional oxygen extraction has been developed using 15O-water (H2- 15O) and 15O-hemoglobin (15O-Hb). Bolus doses (1 mCi) of H2-15O and 15O- Hb were injected 10 minutes apart into the left main coronary artery of 12 normal dogs. Sequential images of regional myocardial tracer clearance were obtained over 5 minutes with a positron camera. Myocardial blood flow calculated from the monoexponential washout of H2- 15O after background correction was 78 +/- 6 (SE) ml/100 g per min. Functional images of regional blood flow in which the image of peak activity was divided by the integrated image of H2-15O washout were derived by computer processing. These images demonstrated homogeneous blood flow in the normal myocardium. Fractional myocardial O2 extraction was determined from an image of initial distribution of O2 used (obtained by extrapolating back to time zero the series of images obtained after 15O-Hb administration), divided by initial distribution of O2 delivered (obtained by back extrapolating H2-15O washout). These functional images showed uniform distribution of fractional O2 extraction in the normal myocardium. Thus, these studies show that regional myocardial blood flow and regional oxygen extraction can be measured simultaneously by sequential imaging after serial intracoronary injections of H2-15O and 15O-Hb

Prevalence of and variables associated with silent myocardial ischemia on exercise thallium-201 stress testing

AbstractThe prevalence of silent myocardial ischemia was prospectively assessed in a group of 103 consecutive patients (mean age 59 ± 10 years, 79% male) undergoing symptom-limited exercise thallium-201 scintigraphy. Variables that best correlated with the occurance of patients ischemia by quantitative scintigraphic criteria were examined. Fifty-nine patients (57%) had no angina on exercise testing. A significantly greater persent of patients with silent ischemia than of patients with angina had a recent myocardial infarction (31% versus 7%, P < 0.01), had no prior angina (91% versus 64%, p < 0.01), had dyspnea as an exercise test end point (56% versus 35%, p < 0.05) and exhibited redistribution defects in the supply regions of the right and circumflex coronary arteries (50% versus 35%, p < 0.05). The group with exercise angina had more ST depression (64% versus 41%, p < 0.05) and more patients with four or more redistribution defects.However, there was no difference between the two groups with respect to mean total thallium-201 perfusion score, number of redistribution defects per patient, multivessel thallium redistribution pattern or extent of angiographic coronary artery disease. There was also no difference between the silent ischemia and angina groups with respect to antianginal drug, usage, prevalence of diabetes mellitus, exercise duration, peak exercise heart rate, peak work load, peak double (rate-pressure) product and percent of patients achieving ≥85% of maximal predicted heart rate for age.Thus, in this study group, there was a rather high prevalence rate of silent ischemia (57%) by exercise thallium-201 criteria. Patients with silent ischemia and those with exercise angina had comparable 1) exercise tolerance and hemodynamics, 2) extent of angiographic coronary artery disease, and 3) extent of exercise-induced hypoperfusion. Finally, more patients with recent infarction had silent ischemia than had exercise angina

Do false positive thallium-201 scans lead to unnecessary catheterization? outcome of patients with perfusion defects on quantitative planar thallium-201 scintigraphy

AbstractObjectives. We postulated that artifactually abnormal thallium-201 scans are well identified at the time of initial clinical interpretation by experienced readers and do not lead to unnecessary coronary angiography.Background. Exercise thallium-201 scintigraphy employing quantitative imaging techniques has yielded sensitivity and specificity values of 80% to 90%. There are image artifacts, such as breast shadows, and variants of normal that, if not correctly identified, can lead to a high false positive rate for detection of coronary artery disease.Methods. Data from 338 consecutive patients with one or more focal thallium-201 defects on quantitative planar Images were reviewed. All patients had undergone symptom-limited exercise scintigraphy and were classified as having either artifactual or nonartifactual thallium-201 defects after review of clinical reports.Results. Of the 265 patients with defects judged to be nonartifactual on clinical readings, 167 underwent coronary angiography, which demonstrated significant coronary artery disease (≥50% stenosis) in 161 (96%) and normal findings in 6. Four of the latter six had documented prior myocardial infarction. The remaining 73 patients (85% female) had thallium-201 defects deemed to be artifactual on clinical readings, chiefly as a result of breast (66%) and diaphragmatic (8%) attenuation or variants of normal (26%). Only 4 (5%) of the 73 patients underwent subsequent coronary angiography; none had coronary artery disease. One had aortic stenosis and two had variant angina. Follow-up (mean 20 ± 2 months) of the 69 patients in this group who did not undergo coronary angiography revealed no deaths and one nonfatal non-Q wave myocardial infarction.Conclusions. Artifactual defects on quantitative planar thallium-201 scintigraphy are well recognized by experienced interpreters and do not result in a high false positive rate leading to unnecessary cardiac catheferization. The incidence of coronary artery disease is high in patients with thallium-201 defects judged to be nonartifactual, and many patients with perfusion defects and angiographically normal coronary arteries have organic heart disease