Myocardial Perfusion Imaging

Extract

[...] Preoperative pharmacologic stress perfusion imaging offers a noninvasive strategy for the detection of physiologically important coronary stenoses that may be associated with an increased risk of early and late cardiac events after peripheral vascular or aortic surgery. Patients who benefit most from preoperative risk assessment using pharmacologic stress perfusion imaging are patients at an intermediate or high risk of having underlying CHD based on clinical and resting ECG variables and who are scheduled to undergo intermediate-risk or high-risk operations. Patients with evidence for inducible ischemia on preoperative perfusion imaging are likely to benefit from preoperative ß-blocker therapy. [...]

[...] Increased FDG activity on clinical PET images in areas of diminished regional blood flow as determined by13 N ammonia imaging is characteristic of myocardial viability. These areas of blood flow/FDG mismatch usually show improved regional function after coronary revascularization. Regions of the heart that show diminished 13 N uptake and FDG uptake "match" pattern) represent predominantly nonviable myocardium, and these segments have only a 10 to 15% probability of showing improved systolic function after revascularization. Patients with CHD with predominantly viable myocardium as the cause of left ventricular dysfunction have better survival and more improvement of heart failure symptoms after revascularization than with medical therapy. [...]

[...] Reversibility is identified by comparing the perfusion pattern on the stress99m Tc-sestamibi images with the pattern on the baseline resting 201 Tl images. The major advantage of this technique is the marked decrease in total imaging time. Detection of Coronary Heart Disease The current indications for stress and rest myocardial perfusion imaging are to diagnose CHD and myocardial infarction, assess prognosis, and detect myocardial viability. Exercise or pharmacologic stress 201 Tl or 99m Tc-sestamibi SPECT imaging in patients with chest pain yields a sensitivity for detecting CHD in the 85% to 90% range. [...]

[...] Exercise or pharmacologic SPECT 201 Tl and exercise or pharmacologic SPECT99m Tc perfusion imaging have sensitivities and specificities that are superior to exercise ECG testing alone. The specificity of gated SPECT for detecting CHD using one of the 99m Tc-labeled perfusion agents is 20 to 30% higher than 201 Tl SPECT in women. Radionuclide stress perfusion imaging is of particular value compared with exercise ECG testing alone in patients with resting ECG abnormalities, such as those seen with left ventricular hypertrophy, digitalis effect, Wolff-Parkinson-White syndrome, and intraventricular conduction abnormalities, and patients who fail to achieve more than 85% of maximum predicted heart rate. [...]

[...] Myocardial perfusion imaging is the most commonly performed nuclear cardiology technique, and it is employed most often in conjunction with either exercise or pharmacologic stress intended to produce flow heterogeneity between relatively hypoperfused and normally perfused myocardial regions. Radionuclide angiography, in which technetium-99m (99m Tc)-labeled red blood cells or other 99m Tc-labeled agents are injected intravenously, is used for measurement of left ventricular ejection fraction (LVEF) and assessment of regional wall motion. This technique is used most commonly to monitor changes in global left ventricular function in patients undergoing chemotherapy for cancer when drugs with the potential for cardiac toxicity are administered. [...]