Decrease in the ability to detect elevated lung thallium due to delay in commencing imaging after exercise.

Post-exercise elevation of the lung/myocardial thallium ratio and a high lung clearance rate between initial and delayed images have been reported to be markers for exercise-induced left ventricular (LV) dysfunction associated with coronary artery disease (CAD). We performed thallium exercise tests on 60 patients, 42 with CAD, in order to determine the effect of delaying initial imaging on detection of elevated lung thallium. In addition to images obtained at 2 minutes and at 2 hours after exercise, 18-minute images were also obtained to simulate such a delay.

The effect of adding mannitol or albumin to a crystalloid cardioplegic solution: a prospective, randomized clinical study.

To determine if the myocardial protection afforded by a cold crystalloid potassium cardioplegic solution could be improved by the addition of either mannitol or albumin, a prospective clinical study was undertaken in which 58 patients undergoing elective aortocoronary bypass were randomized to one of three groups. Each group featured a different cardioplegic solution. The solutions were a standard potassium crystalloid solution, a solution containing mannitol sufficient to raise the osmolality by 20 to 30 mOsm, and a solution containing 5% albumin.

Effect of a delay in commencing imaging on the ability to detect transient thallium defects.

Sixty patients, 42 with coronary disease and 18 normals, were studied to assess the impact of a delay following exercise in commencing thallium imaging on the sensitivity for detecting ischemic transient defects. Three sets of images were obtained beginning 2 min, 18 min, and 2 hr after exercise. Each patient's images were separated into two pairs of studies for analysis: 2 min-2 hr and 18 min-2 hr.

Comparison of exercise electrocardiography and quantitative thallium imaging for one-vessel coronary artery disease.

The relative value of exercise electrocardiography and computer analyzed thallium-201 imaging was compared in 124 patients with 1-vessel coronary artery disease (CAD). Of these, 78 had left anterior descending (LAD), 32 right and 14 left circumflex (LC) CAD. In patients with no previous myocardial infarction (MI), thallium imaging was more sensitive than the electrocardiogram (78% vs 64%, p less than 0.

Increased thallium lung uptake after exercise in isolated left anterior descending coronary artery disease.

Increased thallium lung uptake during exercise correlates with an exercise-induced elevation in left ventricular filling pressure. This finding was analyzed in 48 patients with 1-vessel left anterior descending (LAD) coronary artery disease (CAD) before and after percutaneous transluminal coronary angioplasty. Patients were separated into 2 groups: 13 (27%) patients with increased (group 1) and 35 patients with normal thallium lung uptake (group 2).

The relationship between proton nuclear magnetic resonance relaxation parameters and myocardial perfusion with acute coronary arterial occlusion and reperfusion.

Previous investigators have demonstrated that acute myocardial ischemia, whether followed by reperfusion or not, is associated with prolongation of the proton nuclear magnetic resonance (NMR) relaxation times T1 and T2. Heretofore, the relationship between the severity of ischemia and alterations of these relaxation times has not been assessed. In our studies, changes in T1 and T2 were compared with myocardial perfusion in dogs both before and during 30 and 60 min of coronary arterial occlusion.

Assessment of myocardial ischemia with proton magnetic resonance: effects of a three hour coronary occlusion with and without reperfusion.

Proton (hydrogen-1) magnetic resonance imaging techniques have potential for the detection and characterization of changes associated with myocardial ischemia. Since image contrast is dependent on T1 and T2 relaxation times, we examined these parameters in a canine preparation of occlusion of the left anterior descending coronary artery. Of 16 dogs studied, seven underwent 3 hr of coronary artery occlusion and nine underwent 3 hr of occlusion followed by 1 hr of reperfusion.

Value and limitations of radionuclide angiography in determining the cause of reduced left ventricular ejection fraction: comparison of idiopathic dilated cardiomyopathy and coronary artery disease.

The radionuclide angiograms of 59 patients with a left ventricular (LV) ejection fraction (EF) less than 0.40, 23 with idiopathic dilated cardiomyopathy (IDC) and 36 with coronary artery disease (CAD) were analyzed to assess the usefulness of radionuclide angiography in distinguishing these conditions. Mean right ventricular EF was lower in the IDC group than in the CAD group, 0.

Determination of cardiac risk by dipyridamole-thallium imaging before peripheral vascular surgery.

To evaluate the severity of coronary artery disease in patients with severe peripheral vascular disease requiring operation, we performed preoperative dipyridamole-thallium imaging in 54 stable patients with suspected coronary artery disease. Of the 54 patients, 48 had peripheral vascular surgery as scheduled without coronary angiography, of whom 8 (17 per cent) had postoperative cardiac ischemic events. The occurrence of these eight cardiac events could not have been predicted preoperatively by any clinical factors but did correlate with the presence of thallium redistribution.

Clinical, angiographic, hemodynamic, perfusional and functional changes after one-vessel left anterior descending coronary angioplasty.

Percutaneous transluminal coronary angioplasty (PTCA) was successfully performed in 20 patients with 1-vessel left anterior descending (LAD) coronary artery disease. Exercise capacity in terms of peak workload, heart rate and systolic blood pressure all increased significantly 1 week after PTCA. All patients had some decrease in stenosis size and gradient.

Positive exercise thallium-201 test responses in patients with less than 50% maximal coronary stenosis: angiographic and clinical predictors.

The incidence and causes of abnormal thallium-201 (TI-201) myocardial perfusion studies in the absence of significant coronary artery disease were examined. The study group consisted of 100 consecutive patients undergoing exercise TI-201 testing and coronary angiography who were found to have maximal coronary artery diameter narrowing of less than 50%. Maximal coronary stenosis ranged from 0 to 40%.

Quantitative split dose thallium-201 imaging with exercise: a technique for obtaining rest and exercise perfusion images in one setting and markedly reducing the study time.

In the current study, a technique for performing serial thallium imaging after two separate tracer injections was applied to exercise thallium imaging, thus allowing the acquisition of rest and exercise images within 1 hour. Twenty-four patients with and 10 patients without significant coronary artery disease were studied. One mCi of thallium-201 was injected intravenously and imaging was performed at rest in three projections.

Contrast echocardiography in acute myocardial ischemia: I. In vivo determination of total left ventricular "area at risk".

Myocardial contrast echocardiography has been shown recently to accurately assess the "area at risk" for necrosis after acute coronary occlusion in the experimental model. Risk area quantitation, however, has been studied primarily from single tomographic planes. Because the three-dimensional extent of myocardial necrosis depends on the total volume of myocardium at risk, the total left ventricular "area at risk" was determined in 11 dogs (Group A) with either left anterior descending or left circumflex artery occlusion using contrast echocardiography and compared with risk area determined by technetium autoradiography.

A new approach to quantitation of exercise thallium-201 scintigraphy before and after an intervention: application to define the impact of coronary angioplasty on regional myocardial perfusion.

We have developed a new computer method designed to quantitate regional myocardial thallium-201 (TI-201) initial distribution, redistribution, and clearance rate. In addition, this computer method permits the generation of functional images to compare two thallium images in the same projection to one another. These functional images can be used to demonstrate the extent of redistribution and the extent of change in regional perfusion before and after an intervention.

Quantification of pulmonary thallium-201 activity after upright exercise in normal persons: importance of peak heart rate and propranolol usage in defining normal values.

Fifty-nine normal patients (34 angiographically normal and 25 clinically normal by Bayesian analysis) underwent thallium-201 imaging after maximal upright exercise. Lung activity was quantitated relative to myocardial activity and a lung/myocardial activity ratio was determined for each patient. Stepwise regression analysis was then used to examine the influence of patient clinical characteristics and exercise variables on the lung/myocardium ratio.

The use of preintervention and postintervention thallium imaging for assessing the early and late effects of experimental coronary arterial reperfusion in dogs.

To determine if thallium-201 imaging of myocardial perfusion can be used as an early predictor of myocardial salvage after reperfusion, 24 adult dogs were subjected to complete occlusion of the left anterior descending coronary artery with release of the snare 2 hr later. Separate doses of thallium (1 mCi) and microspheres were given 15 min before, 5 min after, and 1 hr after release of the snare. Gamma camera images of the heart were obtained after each injection of thallium.

Evaluation in dogs of a new double-dose technique for imaging changes in myocardial perfusion.

Assessment of myocardial perfusion with thallium immediately before and after an intervention that alters blood flow has been difficult due to presence of residual activity from the first tracer dose at the time of the second imaging. In a canine model we investigated a technique using two separate thallium injections during an intervention and after its reversal. Images were obtained after each injection, and a difference image was obtained by subtracting the first from the second image to correct for tracer persisting from the first injection.

Right ventricular ejection fraction response to exercise in patients with coronary artery disease: influence of both right coronary artery disease and exercise-induced changes in right ventricular afterload.

To determine the influence of proximal right coronary artery disease and right ventricular afterload on right ventricular ejection fraction response to exercise, 64 patients were studied at rest and after supine exercise with gated equilibrium radionuclide angiography and coronary angiography. Right ventricular afterload response to exercise was estimated from determinations of exercise-induced changes in pulmonary blood volume, previously shown to correlate with exercise-induced changes in pulmonary capillary wedge pressure. Values for right ventricular ejection fraction decreased from rest to exercise (48 +/- 5% to 42 +/- 9%, p less than 0.

Quantitation of myocardial infarct size from thallium-201 images: validation of a new approach in an experimental model.

A new computer-based method has been developed to quantitate myocardial infarct size from the size of the regional thallium-201 deficit. The operator outlines the left ventricular myocardial activity with an ellipse. The program then plots the background-corrected activities of the highest mean value in a 3 pixel myocardial band perpendicular to and within the ellipse.

Sources of variability in the radionuclide angiographic assessment of ejection fraction: a comparison of first-pass and gated equilibrium techniques.

Measurements of ejection fractions (EF) determined by first-pass and gated equilibrium radionuclide angiography are widely believed to be equivalent. To compare these measurements in a large group of patients over a wide range of EF values, left ventricular (LV) and right ventricular (RV) EFs at rest were measured in 135 consecutive patients who underwent the 2 methods of radionuclide angiography within 1 hour: first-pass upright with a multi-crystal camera in the anterior projection and gated equilibrium supine with a single-crystal camera in the left anterior oblique projection. The population included 18 normal patients and 117 patients with various cardiac and pulmonary disorders.