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F J Wackers

Publications and source records attributed to F J Wackers.

At least 55 records · Page 3Linked to original sources
PubMed1994

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. These developments have resulted in a plethora of imaging modalities to choose from. This article attempts to provide a logical framework that may be helpful when choosing the appropriate radionuclide test for cardiac patients and bring order into a seemingly confusion multitude of possibilities.

Acute Disease↗
PubMed1994

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. Dogs were injected with 99mTc-tetrofosmin and radiolabeled microspheres during pharmacological stress. Coincident with radiotracer injection, dynamic planar imaging and arterial sampling were performed to assess 99mTc-tetrofosmin clearance from blood, myocardium, lung and liver. Fifteen minutes after injection, hearts were excised for well counting of myocardial 99mTc-tetrofosmin activity and flow. RESULTS: Myocardial 99mTc-tetrofosmin activity correlated linearly with microsphere flow (r = 0.84). Relative 99mTc-tetrofosmin activity underestimated flow at higher flow ranges (> 2.0 ml/min/g) and overestimated flow in low flow ranges (< 0.2 ml/min/g). Technetium-99m-tetrofosmin cleared rapidly from the blood and was retained in the myocardium. Resting target-to-background activity ratios (heart:lung = 3.57 +/- 1.01; heart:liver = 0.58 +/- 0.04) were acceptable 10 min after injection. CONCLUSION: Our experimental data support both the validity of 99mTc-tetrofosmin as a myocardial perfusion tracer and the use of early poststress 99mTc-tetrofosmin imaging for the assessment of myocardial perfusion in man.

Adenosine↗
PubMed1994

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.

Coronary Circulation↗
PubMed1993

Frequency and significance of right ventricular dysfunction during inferior wall left ventricular myocardial infarction treated with thrombolytic therapy (results from the thrombolysis in myocardial infarction [TIMI] II trial). The TIMI Research Group.

To determine the effect of thrombolytic therapy on the frequency of right ventricular (RV) dysfunction, and whether RV dysfunction is a risk factor for morbidity and mortality after discharge from the hospital, 1,110 patients in the Thrombolysis in Myocardial Infarction (TIMI) II trial with acute inferior wall left ventricular myocardial infarction were studied. RV dysfunction was defined as an RV wall motion abnormality on equilibrium radionuclide ventriculography performed a mean of 9 days after admission to the hospital. Fifty-eight patients (5%) had RV dysfunction. Baseline clinical characteristics among patients with and without RV dysfunction were similar. However, patients with RV dysfunction had a lower mean left ventricular ejection fraction (51.2 +/- 1.2% vs 55.5 +/- 0.3%; p < 0.001) and a greater frequency of in-hospital complications. Angiographic data from patients undergoing protocol catheterization 18 to 48 hours after hospital admission show that the infarct-related artery was more likely to be occluded in those with RV dysfunction (48% [15 of 31] vs 14% [68 of 495]; p < 0.001). There was no difference in the frequency of multivessel disease between the 2 groups. In patients with RV dysfunction in whom radionuclide ventriculography was repeated 6 weeks after hospital discharge, RV wall motion abnormalities persisted in only 18% (8 of 45). Mortality in the year after discharge was 3.5% (2 of 58) among patients with RV dysfunction compared with 1.7% (18 of 1,052; p = NS) among those without RV dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1993

Detection and significance of myocardial ischemia in stable patients after recovery from an acute coronary event. Multicenter Myocardial Ischemia Research Group.

OBJECTIVE: To determine the clinical significance of silent and symptomatic myocardial ischemia detected by noninvasive testing in stable postcoronary patients. DESIGN: Cohort study with a mean 23-month follow-up. SETTING: Ambulatory outpatients after recent hospitalization for an acute coronary event. PATIENTS: Nine hundred thirty-six patients (76% male; mean age, 58 years) who were clinically stable 1 to 6 months after hospitalization for acute myocardial infarction or unstable angina. INTERVENTIONS: Noninvasive testing involved rest, ambulatory, and exercise electrocardiograms and stress thallium-201 scintigraphy. MAIN OUTCOME MEASURES: Cox regression analysis was used to evaluate the risk (hazard ratio) of first recurrent primary events (cardiac death, nonfatal infarction, or unstable angina) or restricted events (cardiac death or nonfatal infarction) associated with ischemic noninvasive test results. RESULTS: ST segment depression on the rest electrocardiogram was the only noninvasive test variable that identified a significantly increased risk (P = .05) for first recurrent primary events (hazard ratio; 95% confidence limits): rest electrocardiogram ST depression (1.5; 1.00, 2.25); ambulatory electrocardiogram ST depression (0.86; 0.49, 1.51); exercise electrocardiogram ST depression (1.13; 0.82, 1.56); and stress thallium-201 reversible defects (1.3; 0.96, 1.74). Test results were similar for first recurrent restricted events, and in patients with and without angina. Significantly increased risk (P < .05) was noted when exercise-induced ST depression occurred in patients who also had reduced exercise duration (hazard ratio, 3.4) or when reversible thallium-201 defects occurred in patients who also had increased lung uptake (hazard ratio, 2.8). Each high-risk subset made up less than 3% of the population and contained less than 6% of patients with first primary events. CONCLUSION: Detection of silent or symptomatic myocardial ischemia by non-invasive testing in stable patients 1 to 6 months after an acute coronary event is not useful in identifying patients at increased risk for subsequent coronary events.

Adult↗
PubMed1993

Short-term effects of early intravenous treatment with a beta-adrenergic blocking agent or a specific bradycardiac agent in patients with acute myocardial infarction receiving thrombolytic therapy.

OBJECTIVES: This study was conducted to explore mechanisms that could explain the possible clinical benefit of early administration of a beta 1-selective adrenoreceptor blocking agent or a bradycardiac drug as adjunct to thrombolysis in acute myocardial infarction. BACKGROUND: The effects of beta-blockers given concomitantly with thrombolytic therapy in patients with acute myocardial infarction have not been fully examined. The potential role of specific bradycardiac agents lacking negative inotropism as an alternative to beta-blockers in this setting has never been studied in humans. METHODS: In a double-blind study, we examined the effects of early intravenous and continued oral administration of a beta-blocker (atenolol), a specific bradycardiac agent (alinidine) or placebo on left ventricular function, late coronary artery patency, infarct size, exercise capacity and incidence of arrhythmias. RESULTS: A total of 292 patients with acute myocardial infarction of < or = 5 h duration and without contraindications to thrombolytic or beta-blocker therapy were studied. Of these, 100 were allocated to treatment with atenolol (5 to 10 mg intravenously followed by 25 to 50 mg orally every 12 h), 98 to alinidine (20 to 40 mg intravenously followed by 20 to 40 mg orally every 8 h) and 94 to placebo. All patients received 100 mg of alteplase over 3 h and full intravenous heparinization. No significant differences in coronary artery patency, global ejection fraction or regional wall motion were observed at 10 to 14 days among the three groups. Likewise, enzymatic and scintigraphic infarct size were also very similar. Neither atenolol nor alinidine was associated with a significant reduction in the incidence of arrhythmias during the 1st 24 h. No significant differences in clinical events were observed, with the exception of a greater incidence of nonfatal pulmonary edema in the atenolol group (6% vs. 1% in the alinidine group and 0% in the placebo group, p = 0.021). CONCLUSIONS: In the absence of contraindications, the administration of a beta-blocker or a specific bradycardiac agent together with thrombolytic therapy was safe. In this limited number of patients, these agents did not appear to enhance myocardial salvage or preservation of left ventricular function or to reduce the incidence of major arrhythmias in the early phase of infarction.

Adult↗
PubMed1993

Factors affecting uniformity in interpretation of planar thallium-201 imaging in a multicenter trial. The Multicenter Study on Silent Myocardial Ischemia (MSSMI) Thallium-201 Investigators.

OBJECTIVES: This study was designed to assess factors affecting interobserver agreement in interpretation of planar thallium-201 stress imaging in the Multicenter Study on Silent Myocardial Ischemia (MSSMI). BACKGROUND: Five hundred fifty-six planar thallium-201 images were interpreted in 24 clinical centers and in a Radionuclide Core Laboratory. The trial's Coordinating and Data Center observed that the participating clinical centers interpreted a significantly greater number of thallium-201 stress studies as abnormal (i.e., myocardial ischemia or scar) than the Core Laboratory, and overall agreement was poor (kappa 0.27). METHODS: Agreement in image interpretation between clinical centers and the Radionuclide Core Laboratory was analyzed by kappa statistics. The reproducibility of the Core Laboratory results on 41 randomly selected test studies was excellent (kappa 0.77). In contrast, the reproducibility of interpretation in the clinical centers on their own studies was at best fair (kappa 0.45). It was hypothesized that the poor agreement and reproducibility in the clinical centers were caused by lack of standardization of image display and lack of objective criteria for image interpretation. To test the effect of standardization, 13 clinical investigators interpreted the same 41 test studies using 1) uniform image display, and 2) uniform quantification of images. RESULTS: The agreement in interpretation between clinical investigators and the Radionuclide Core Laboratory improved modestly with uniformity of image display (kappa 0.57) but improved markedly (kappa 0.66) with quantitative circumferential profile analysis. CONCLUSIONS: Lack of standardization in image display and lack of objective criteria for interpretation of thallium-201 images are responsible for suboptimal reproducibility and poor interlaboratory agreement in the interpretation of thallium-201 stress imaging. The adoption of a uniformly accepted method for computer quantification of myocardial perfusion images is crucial to improve agreement in interpretation.

Exercise Test↗
PubMed1993

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. This characteristic allows for injection during angioplasty and later imaging for visualization and quantitation of the nonperfused area at risk. METHODS: Thirty-nine patients referred for coronary angioplasty were studied. Technetium-99m sestamibi was injected intravenously during angioplasty balloon inflation. Planar (33 patients) or tomographic (6 patients) imaging was performed after completion of angioplasty. Imaging was repeated 24 to 48 h later. Myocardial risk area (perfusion defect on angioplasty image) was quantified as an integral using circumferential count distribution profiles and normal reference. Angiographic risk area was assessed using five scoring methods. RESULTS: The scintigraphic risk area was 14 +/- 15 on planar images and 39 +/- 16 on tomography. Scintigraphic risk area of patients with infarction was larger than in patients without (22 +/- 17 versus 7 +/- 8, p = 0.003). The left anterior descending coronary artery had a larger mean risk area than other vessels (22 +/- 15 versus 7 +/- 11, p = 0.002). The presence of angiographic collateral channels was associated with smaller risk areas. Angiographic risk scores correlated only moderately with the technetium-99m sestamibi risk area (r = 0.54 to 0.65), with considerable spread of data. CONCLUSIONS: Area at risk estimated from coronary angiography does not correlate well with that from quantitative myocardial perfusion imaging with technetium-99m sestamibi. These findings emphasize that the functional significance of coronary artery disease is not predicted by coronary anatomy alone.

Adult↗
PubMed1993

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. MIBI was injected before occlusion (group 1A) or during occlusion (groups 1B and 2), and serial ECG-gated planar imaging was performed. Dobutamine was infused after 3 hours of reperfusion (groups 1B and 2) to transiently alter left ventricular size and function. Perfusion defect magnitude (DM) and extent (DE) were serially quantified with circumferential profile analysis of end-systolic (ES), end-diastolic (ED), and summed images. Flow was assessed with radiolabeled microspheres and correlated with myocardial MIBI activity. Myocardial thickening was assessed in the risk area with sonomicrometers. In group 1A dogs, ischemic dyskinesis produced large artifactual quantitative MIBI defects on ES images (DM, 9.3 +/- 1.3; DE, 27.8 +/- 6.0) that were significantly smaller on ED images (DM, 4.5 +/- 0.9, P < .05; DE, 4.4 +/- 2.3, P < .05). In addition, DM and DE correlated inversely with myocardial thickening on ES images (DM, r = -.84; DE, r = -.78) and summed images (DM, r = -.72; DE, r = -.61) but not ED images (DM, r = -.12; DE, r = -.15). An index of defect reduction derived from summed images correlated well with thickening fraction in stunned dogs (group 1B, r = .89) but poorly in infarcted dogs (group 2, r = .41) subjected to dobutamine stress. CONCLUSIONS: 99mTc-MIBI defect size may be affected by alteration of left ventricular geometry. Changes in regional function may confound analysis of risk area and myocardial salvage with serial 99mTc-MIBI imaging and may also affect defect size during pharmacological stress with dobutamine. Dobutamine 99mTc-MIBI imaging may be useful for distinguishing viable and nonviable myocardium.

Animals↗
PubMed1993

Assessing myocardial reperfusion with technetium-99m-labeled myocardial perfusion agents: basic concepts and clinical applications.

The accurate determination of reperfusion in the setting of acute myocardial infarction and the evaluation of vessel patency or reocclusion has become critical in the management of patients in the thrombolytic era. This article reviews the biological properties and potential clinical applications of the new technetium-99m-labeled perfusion agents following perfusion. Both 99mTc-Sestamibi and 99mTc-Teboroxime have unique biological properties that may permit the assessment of reperfusion and vessel patency following thrombolysis. The noninvasive evaluation of patients following acute coronary reperfusion, must occur during acute, intermediate, and predischarge phases. Serial imaging with 99mTc-Sestamibi and 99mTc-Teboroxime in combination probably will serve in the future as an important means of assessing myocardial salvage, residual viability, and vessel patency following thrombolysis.

Humans↗
PubMed1993

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. Cardiac peak power increased continuously in healthy subjects, from 5.4 +/- 0.8 W/ml at rest to 11.4 +/- 3.1 W/ml at peak exercise, p < 0.001. In patients, peak power increased initially, reached a plateau in stage 2, and subsequently remained unchanged in stage 3 (5.6 +/- 2 versus 5.6 +/- 1.6 W/ml, p = ns). Ejection fraction demonstrated a flat response during exercise in patients, contrasting with a 42% increase in cardiac peak power. The lack of increase in ejection fraction was attributed to its dependence on afterload. Peak power showed no correlation with systemic vascular resistance (r = 0.01, p = ns). In a subgroup of patients with low resting LVEF (LVEF = 26% +/- 7%), peak power increased 70% during exercise, from 2.0 +/- 0.7 to 3.5 +/- 1.7 W/ml, p < 0.05, in contrast to a flat ejection fraction response. Thus, cardiac peak power, a relatively afterload-independent index of left ventricular performance and contractility can be obtained noninvasively during exercise.

Blood Pressure↗
PubMed1993

Biokinetics of technetium-99m-tetrofosmin: myocardial perfusion imaging agent: implications for a one-day imaging protocol.

Tetrofosmin is a 99mTc-labeled myocardial perfusion imaging agent that has shown encouraging results in Phase I and II clinical trials. The purpose of this study was to determine the biokinetics of this agent following administration during exercise and at rest in order to determine an optimal imaging protocol. Twenty patients with suspected coronary artery disease underwent symptom-limited treadmill exercise. Six to 8 mCi of 99mTc-tetrofosmin was injected at peak exercise and 22-24 mCi was injected 4 hr later at rest. Serial 5-min planar images were obtained in the left anterior oblique view at 5, 10, 15, 30, 60, 120 and 180 min after the radiotracer injection. Regions of interest were drawn on the serial images around the entire heart and portions of liver, lung, spleen, gallbladder and gastrointestinal tract. Average decay-corrected counts per pixel in each organ were plotted against time. In addition, heart-to-adjacent organ ratios were also determined. On stress images, the heart had the highest activity at all times, with the exception of gallbladder in the first 15 min. On rest images, the gallbladder, liver and gastrointestinal tract initially had higher activity than the heart; but the activity in these organs cleared rapidly over the subsequent 30-60 min. Heart-to-adjacent organ ratios were > 1.0 at all times in the stress images. Heart-to-organ ratios were < 1.0 in the first 15 min on the rest images for the liver and gastrointestinal tract. However, 30 min later, all ratios on the rest images were > or = 1.0. Technetium-99m-tetrofosmin images were considered to be of good to excellent quality with good myocardial delineation and adequate contrast between the heart and background. These These observations indicate that a convenient one-day tetrofosmin imaging protocol similar in duration to conventional 201Tl imaging is feasible.

Adult↗
PubMed1992

Comparison of thallium-201 and technetium-99m methoxyisobutyl isonitrile.

Thallium-201 (201Tl) is a well-established radionuclide used in myocardial perfusion imaging for assessing the presence and prognostic significance of coronary artery disease. Recently, technetium-99m hexakis-2-methoxyisobutyl isonitrile (99mTc-sestamibi) has become available for the same diagnostic and prognostic procedures. This discussion compares the imaging characteristics and clinical applications of 201Tl with those of 99mTc-sestamibi. There is a strong diagnostic concordance between the 2 agents in symptomatic patients. Various comparative clinical trials have shown in numerous patients that both agents have a similar diagnostic yield in both planar and single-photon emission computed tomography (SPECT) imaging. Because of better image quality of the 99mTc agent, there is a trend toward better specificity and normalcy rate, in comparison to 201Tl. However, when using reinjection imaging protocols, 201Tl retains a unique place as an imaging agent to identify viable myocardium.

Coronary Disease↗
PubMed1992

Assessment of global and regional left ventricular performance at rest and during exercise after thrombolytic therapy for acute myocardial infarction: results of the Thrombolysis in Myocardial Infarction (TIMI) II Study.

Global and regional left ventricular performances were evaluated with equilibrium radionuclide angiocardiography in patients in the Thrombolysis in Myocardial Infarction (TIMI) II trial at the time of hospital discharge. Studies at rest were available in 1,162 (69%) of the invasive and 1,150 (69%) of the conservative strategy patients, and exercise studies in 1,133 (67%) of the invasive and 1,145 (69%) of the conservative patients. Repeat studies were performed at the time of 6-week follow-up. Global and regional ejection fraction at rest were both comparable in patients assigned to each of the treatment strategies. However, at the time of hospital discharge patients in the invasive strategy had normal exercise responses more frequently (29.7 vs 25.8% p = 0.01), greater peak exercise LV ejection fraction (54.8 +/- 13.8% vs 53.1 +/- 14.1%, p = 0.004), greater exercise--rest change in LV ejection fraction (3.7 +/- 6.7% vs 2.7 +/- 7.2%, p less than 0.001) and greater peak exercise infarct zone regional ejection fraction (53.2 +/- 31.1% vs 50.3 +/- 33.0%, p less than 0.001) than patients assigned to the conservative strategy. At 6-week follow-up these differences between treatment strategies were no longer evident. When data were restricted to those collected at comparable work loads, similar differences in hospital discharge exercise performance between invasive vs conservative strategy patients were observed. Thus, there is a small transient difference in exercise global and regional LV performance associated with an invasive as opposed to conservative strategy after thrombolytic therapy. These differences are noted at the time of hospital discharge but not at 6 weeks, and are unlikely to confer clinical benefit.

Chi-Square Distribution↗