Technetium-99m-nitroimidazole (BMS181321): a positive imaging agent for detecting myocardial ischemia.

Unlabelled: A new technetium-99m-labeled nitroimidazole (BMS181321) has been proposed for positive imaging of myocardial ischemia.

Methods: An in vivo open-chest canine model of partial coronary occlusion and pacing-induced demand ischemia was used to correlate myocardial retention of BMS181321, following an intravenous injection at peak stress, with regional microsphere blood flow. Postmortem measurements of myocardial BMS181321 activity and flow were correlated with in vivo planar and ex vivo SPECT images.

Tomographic and planar quantitation of perfusion defects on technetium 99m-labeled sestamibi scans: evaluation in patients treated with thrombolytic therapy for acute myocardial infarction.

Background: Our segmentation algorithm for single-photon emission computed tomographic perfusion studies was tested in 244 patients treated by thrombolysis within 5 hours after onset of symptoms. This algorithm uses radial slices to approximate true three-dimensional gradients, determines the apex and basal plane, and creates a perfusion and volume polar map.

Methods And Results: Perfusion defect size was compared with enzymatic infarct size and global and regional function.

Relationship between reverse redistribution on planar thallium scintigraphy and regional myocardial viability: a correlative PET study.

Unlabelled: The purpose of this study was to assess myocardial metabolic activity in the area of reverse redistribution and determine the prognostic value of reverse redistribution and PET imaging. Reverse redistribution is thought to be a manifestation of reperfusion therapy and associated with a favorable clinical outcome. Preliminary observations from the Thrombolysis and Myocardial Infarction (TIMI) trial suggest that reverse redistribution is associated with higher incidence of future cardiac events.

Myocardial perfusion imaging with 99mTc tetrofosmin. Comparison to 201Tl imaging and coronary angiography in a phase III multicenter trial. Tetrofosmin International Trial Study Group.

Background: Our objective was to compare the sensitivity and specificity of tetrofosmin, a new 99mTc-labeled myocardial perfusion imaging agent for the detection of myocardial perfusion abnormalities, with those of 201Tl and coronary angiography. Our hypothesis was that same-day stress/rest tetrofosmin imaging could provide data comparable to those of 201Tl imaging. Myocardial perfusion imaging plays an important role for the evaluation of coronary artery disease.

Prognostic significance of a fixed thallium defect one to six months after onset of acute myocardial infarction or unstable angina. Multicenter Myocardial Ischemia Research Group.

In a large prospective study of myocardial ischemia, exercise thallium studies were performed in 896 patients 1 to 6 months after an acute coronary event (acute myocardial infarction, 70%; unstable angina, 30%). Thallium images were analyzed quantitatively and classified as normal or demonstrating either a reversible defect after 2 to 4 hours or having only a fixed defect. The effect of the thallium findings on the time to end point (cardiac death, nonfatal infarction, or unstable angina) were examined by Kaplan-Meier curves and compared using the log-rank statistic.

Reduced variability of interpretation and improved image quality with a technetium 99m myocardial perfusion agent: comparison of thallium 201 and technetium 99m-labeled tetrofosmin.

Background: The purpose of this study was to determine the relative image quality and interobserver variability among four readers for 201Tl and 99mTc-labeled tetrofosmin myocardial perfusion images. 99mTc-labeled perfusion agents, with near-optimal physical characteristics for gamma camera imaging, may allow for superior image quality and improved consistency of interpretation. However, most studies to date have demonstrated only similarity in the diagnostic accuracy between technetium agents and thallium.

Limited usefulness of exercise testing and thallium scintigraphy in evaluation of ambulatory patients several months after recovery from an acute coronary event: implications for management of stable coronary heart disease. Multicenter Myocardial Ischemia Research Group.

Objectives: This study evaluated the value of noninvasive testing to predict cardiac events in patients with stable coronary disease after hospital admission (and risk stratification) for an acute coronary event.

Background: Exercise testing with thallium perfusion imaging identifies patients with obstructive coronary artery disease and has been used to stratify patients after myocardial infarction. Its usefulness for predicting cardiac events in patients with stable coronary disease after recovery from an acute coronary event was explored.

Science, art, and artifacts: how important is quantification for the practicing physician interpreting myocardial perfusion studies?

Although considerable efforts have been directed toward improving imaging agents and imaging equipment, relatively little attention has been given to factors that optimize image interpretation. Stress myocardial perfusion images are often interpreted by visual inspection alone. This may introduce considerable inter- and intraobserver variability.

One-year prognosis of patients with normal planar or single-photon emission computed tomographic technetium 99m-labeled sestamibi exercise imaging.

Background: The favorable prognostic significance of normal 201Tl stress perfusion images, even in the presence of known coronary artery disease, has been well documented. Relatively few data are available with regard to the prognostic significance of normal planar and single-photon emission computed tomographic (SPECT) stress 99mTc-labeled sestamibi (99mTc-sestamibi) images.

Methods And Results: The prognostic significance of normal exercise 99mTc-sestamibi myocardial perfusion imaging was evaluated in 208 consecutive patients.

Fetal responses to maternal exercise: effect on fetal breathing and body movement.

This study was conducted to determine the impact of maternal exercise on fetal breathing and fetal body movement, which are commonly used for assessing fetal well-being. Twelve healthy patients with a range of gestational ages of 26 to 36 weeks, who actively exercised throughout pregnancy, participated in the study. The patients walked on a motorized treadmill using a modified Bruce protocol until the maternal heart rate reached 75% of the age-predicted maximal heart rate.

Radionuclide evaluation of coronary artery disease in the 1990s. Choosing the best stress, best tracer, best technique.

In recent years, many changes and new developments have occurred in nuclear cardiology. New radiopharmaceuticals and new stress modalities have been developed. Imaging techniques and instrumentation have developed as well.

Exercise myocardial perfusion imaging.

The role of physical exercise in myocardial perfusion imaging is critical for two reasons: (1) stress is essential to create heterogeneity of blood flow in myocardial regions supplied by normal versus stenosed coronary arteries and (2) exercise data provide invaluable information that can influence the interpretation of perfusion images. Image interpretation and correlation with exercise data provide important prognostic information on a patient's risk for subsequent cardiac events.

Technetium-99m-tetrofosmin to assess myocardial blood flow: experimental validation in an intact canine model of ischemia.

Unlabelled: Technetium-99m-tetrofosmin is a 99mTc-labeled perfusion tracer demonstrating promise for myocardial perfusion imaging. To determine if 99mTc-tetrofosmin tracks myocardial flow over a pathophysiologic range, the initial myocardial uptake and clearance of 99mTc-tetrofosmin relative to microsphere flow were evaluated in a canine model of ischemia during pharmacological vasodilatation.

Methods: Six open-chest dogs were subjected to complete left anterior descending coronary artery occlusion.

The maze of myocardial perfusion imaging protocols in 1994.

A confusing multitude of different myocardial perfusion imaging protocols have been proposed during the last few years. The impetus for this development was new insights in imaging with thallium 201 and the challenge to perform efficient imaging with the newly developed technetium 99m-labeled imaging agents. The practicing nuclear cardiologist is confronted with a true maze of options.

Effects of altered left ventricular geometry on quantitative technetium 99m sestamibi defect size in humans: perfusion imaging during coronary angioplasty.

Background: Serial myocardial perfusion imaging is used to assess exercise-induced myocardial ischemia and myocardial risk area, salvage, and viability in patients with myocardial infarction. In an experimental animal model it has been shown that abnormal regional wall motion and altered left ventricular geometry can produce apparent perfusion defects independent of changes in blood flow. The effects of regional alteration in ventricular geometry on perfusion images in humans are not defined.

A new quantitative method for the analysis of cardiac perfusion tomography (SPET): validation in post-infarct patients treated with thrombolytic therapy.

In this study a new method for assessment of perfusion defects (PDs) derived from myocardial perfusion tomograms was evaluated in patients treated with thrombolytic therapy. Using global constraints and dynamic programming, a model-based delineation algorithm defined myocardial borders, the basal plane and absolute and relative PD size in 49 thallium-201 chloride (201TL CL) and 60 technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) tomograms. Tomographic (single-photon emission tomography: SPET) and planar quantification of PDs was compared to enzymatic infarct size as well as to global (LVEF) and regional ventricular function (RWM) obtained by contrast angiography.

Left ventricular peak power during exercise: a noninvasive approach for assessment of contractile reserve.

Cardiac peak power, a contractility index based upon instantaneous changes in intracavitary pressure and systolic peak flow, was measured at rest and during supine exercise in 26 patients with coronary artery disease and 8 healthy subjects. The pathophysiological significance of this index was compared with left ventricular ejection fraction (LVEF) during exercise. Cardiac peak power, ejection fraction, end-diastolic volume, stroke volume, cardiac output and systemic vascular resistance were measured at rest, during three stages of supine bicycle ergometry and two stages of recovery.

Impact of regional ventricular function, geometry, and dobutamine stress on quantitative 99mTc-sestamibi defect size.

Background: Serial myocardial perfusion imaging with 99mTc-sestamibi (MIBI) was used to evaluate infarct risk area and salvage after thrombolysis. The purpose of this investigation was to determine whether changes in MIBI defect size observed after reperfusion may result in part from distortion of regional and global left ventricular geometry.

Methods And Results: Twenty-five open-chest dogs were subjected to either 15 minutes (groups 1A and 1B) or 3 hours (group 2) of left anterior descending coronary artery occlusion followed by 3 hours of reperfusion.

Myocardial risk area defined by technetium-99m sestamibi imaging during percutaneous transluminal coronary angioplasty: comparison with coronary angiography.

Objectives: The purpose of this study was to compare the assessment of myocardial area at risk in patients with coronary artery stenosis by coronary angiography and quantitative myocardial perfusion imaging with technetium-99m sestamibi.

Background: Decisions concerning patient management frequently rely on semiquantitative angiographic estimation of the myocardial area at risk, although this approach has not been well validated. Technetium-99m sestamibi is a perfusion imaging agent with little redistribution after initial myocardial uptake.