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Biomedical subjects

J Lette

Publications and source records attributed to J Lette.

At least 19 recordsLinked to original sources
PubMed1992

Preoperative coronary artery disease risk stratification based on dipyridamole imaging and a simple three-step, three-segment model for patients undergoing noncardiac vascular surgery or major general surgery.

A 3-step, 3-segment scintigraphic model was developed to improve the accuracy of dipyridamole-thallium imaging for preoperative cardiac risk assessment and to simplify the prognostic interpretation of the images. The model was developed in a pilot study of 60 patients and validated in a group of 355 patients referred for vascular and major general surgery. Study end points included myocardial infarction and cardiac death. Step 1: The postoperative cardiac event rate was 1.3% in 225 patients with normal anterior, inferio- and posterolateral segment perfusion and without transient left ventricular dipyridamole-induced cavitary dilation. Step 2: The physiologic rationale for step 2 consists of identifying patients who are most likely to have left main, 3-vessel or high-risk 2-vessel coronary artery disease or a significant amount of jeopardized myocardium in the territory of a critical coronary stenosis. Of 29 patients with either reversible defects of all 3 segments, transient cavitary dilation, or at least 1 severe grade 3/3 reversible defect, 52% (15 of 29) sustained a postoperative cardiac event. Step 3: The remaining 101 patients were stratified according to age greater than 70 years (p = 0.01), presence of diabetes (p = 0.0004) and the number of segments displaying reversible defects (1 or 2) with cardiac event rates ranging from 5 to 36%. The 3-step, 3-segment model is a useful alternative to the conventional interpretation of dipyridamole myocardial perfusion images for the purpose of quick and efficient preoperative risk stratification based on the rationale of correlating surgical risk with the amount of potentially ischemic myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Prognostic implications of a negative dipyridamole-thallium scan: results in 360 patients.

PATIENTS AND METHODS: A total of 360 patients with either normal perfusion (314) or fixed defects (46) on dipyridamole-thallium scans were followed over an average period of 16 months. Of the 360 patients, 194 subsequently underwent major noncardiac surgery. RESULTS: There were a total of eight cardiac events including two postoperative complications (one fatal and one nonfatal myocardial infarction) and six cardiac events during long-term follow-up (one sudden death and five nonfatal infarctions). During the follow-up period, three patients underwent coronary artery bypass surgery. The low cardiac event rate could not be explained by a low pretest likelihood of coronary artery disease: 77% of the 360 patients had either typical angina pectoris, a previous myocardial infarction, or peripheral vascular disease, which is associated with a high prevalence of coronary artery disease. CONCLUSIONS: In patients with a high pretest likelihood of coronary artery disease, the absence of thallium redistribution on a dipyridamole-thallium scan denotes a very low (1%) cardiac risk for major noncardiac surgery as well as low long-term cardiac mortality (0.3%) and morbidity (1.4%) rates. The coronary death rate is comparable to that of patients with minimal (less than 50%) coronary stenoses.

Clinical Protocols↗
PubMed1992

Preoperative and long-term cardiac risk assessment. Predictive value of 23 clinical descriptors, 7 multivariate scoring systems, and quantitative dipyridamole imaging in 360 patients.

A total of 360 patients underwent preoperative cardiac risk assessment using 23 clinical parameters, seven multivariate clinical scoring systems, and quantitative dipyridamole-thallium imaging to predict postoperative and long-term myocardial infarction and cardiac death after noncardiac surgery. There were 30 postoperative and an additional 13 cumulative long-term cardiac events after an average follow-up of 15 months. Clinical descriptors were not useful in predicting the outcome of individual patients. The postoperative and long-term cardiac event rates were 1% and 3.5%, respectively, in patients with normal scans or fixed perfusion defects, and 17.5% and 22% in patients with reversible defects. Using quantitative indices reflecting the amount of jeopardized myocardium, patients could be stratified by dipyridamole imaging into multiple scintigraphic subsets, with corresponding postoperative and 1-year coronary morbidity and mortality rates ranging from 0.5% to 100% (p = 0.0001). Thus, postoperative and long-term cardiac events cannot be predicted clinically, whereas quantitative dipyridamole imaging accurately identifies high-risk patients who require preoperative coronary angiography.

Aged↗
PubMed1992

Large renal arteriovenous malformation: scintigraphic evaluation and therapeutic embolization.

The authors describe a patient with a rare type of renal arteriovenous malformation, which was successfully treated by therapeutic coil embolization. Embolization did not destroy healthy renal tissue, as was shown by the Cerino technique, which measures the glomerular filtration rate of each kidney by image processing for standard renograms obtained after administration of diethylene-triaminepenta-acetic acid labelled with technetium 99m.

Arteriovenous Malformations↗
PubMed1991

Multivariate clinical models and quantitative dipyridamole-thallium imaging to predict cardiac morbidity and death after vascular reconstruction.

Patients with peripheral vascular disease have a high prevalence of coronary artery disease and are at increased risk for cardiac morbidity and death after vascular reconstruction. The present study was undertaken to assess the value of 18 clinical parameters, of 7 clinical scoring systems, and of quantitative dipyridamole-thallium imaging for predicting the occurrence of postoperative myocardial infarction or cardiac death. Vascular surgery was performed in 125 patients. Thirteen postoperative cardiac events occurred, including 10 cardiac deaths and 3 nonfatal infarctions. Clinical parameters were not useful in predicting postoperative outcome. All 63 patients with normal scan results or fixed perfusion defects underwent surgery uneventfully, whereas 21% (13/62) of patients with reversible defects had a postoperative cardiac complication. By use of quantitative scintigraphic indexes we found that patients with reversible defects could be stratified into intermediate and high-risk subgroups with postoperative event rates of 5% (2/47) and 85% (11/13), respectively, despite intensive postoperative monitoring and antianginal medication. Thus in patients unable to complete a standard exercise stress test, postoperative outcome cannot be predicted clinically, whereas dipyridamole-thallium imaging successfully identified all patients who had a postoperative cardiac event. By use of quantification we found that patients with reversible defects can be stratified into an intermediate risk subgroup that can undergo surgery with minimal complication rate and a high-risk subgroup that requires coronary angiography.

Canada↗
PubMed1991

In vivo glomerular filtration rate measurement based solely on image processing.

A simple and reliable technique was developed to measure split renal glomerular filtration (GFR) based solely on image processing of the standard 20-minute Tc-99m DTPA renogram. It requires neither syringe counting nor blood or urine sampling. Using three sequential blood samples in 36 patients, GFR values correlated well (r = 0.92) with in vitro GFR measurements.

Adult↗
PubMed1991

Dipyridamole-thallium imaging: minimum dose requirements.

A total of 372 consecutive dipyridamole-thallium studies were reviewed to determine if a relationship existed between the dose of dipyridamole administered and the likelihood that thallium images would show reversible defects. Men who received a dose of less than 31 mg were less likely to have thallium redistribution (P = 0.0001). Until the ideal study involving repeat testing with incremental dipyridamole doses on different days is carried out, the authors recommend that a minimal dose of 31 mg be administered for dipyridamole-thallium imaging.

Coronary Vessels↗
PubMed1990

Transient left ventricular cavitary dilation during dipyridamole-thallium imaging as an indicator of severe coronary artery disease.

Transient left ventricular (LV) cavitary dilation during dipyridamole-thallium imaging was reported in 45 of 510 (9%) consecutive patients referred for dipyridamole-thallium imaging. Clinical and hemodynamic effects observed during dipyridamole infusion were not predictive of transient cavitary dilation on the thallium images. Coronary angiography was performed in 32 of the 45 patients: 75% had either left main, 3-vessel or "high-risk" 2-vessel coronary artery disease. Although 25 of 45 patients (56%) with transient cavitary dilation were either asymptomatic or had only grade 1/4 effort angina, 16 of 25 patients (64%) not referred for coronary revascularization sustained a cardiac event during a mean follow-up of 12 months. Most events were cardiac deaths (75%) and 87% of events occurred within 4 months of the test. Noncardiac surgery was performed in 187 of the 510 patients. The postoperative cardiac event rate was 2% in the 101 patients with normal scans or fixed defects, 19% in 75 patients with reversible perfusion defects and 58% in 12 patients with reversible cavitary dilation (p less than 0.0001). Thus, transient LV dilation during dipyridamole-thallium imaging is a marker of severe underlying coronary artery disease, denotes a poor prognosis and predicts a high risk of postoperative cardiac complications in patients who undergo noncardiac surgery.

Coronary Angiography↗
PubMed1990

Postoperative myocardial infarction and cardiac death. Predictive value of dipyridamole-thallium imaging and five clinical scoring systems based on multifactorial analysis.

Sixty-six patients unable to complete a standard preoperative exercise test because of physical limitations were studied to determine the predictive value of individual clinical parameters, of clinical scoring systems based on multifactorial analysis, and of dipyridamole-thallium imaging before major general and vascular surgery. Study endpoints were limited to postoperative myocardial infarction or cardiac death before hospital discharge. There were nine postoperative cardiac events (seven deaths and two nonfatal infarctions). There was no statistical correlation between cardiac events and preoperative clinical descriptors, including individual clinical parameters, the Dripps-American Surgical Association score, the Goldman Cardiac Risk Index score, the Detsky Modified Cardiac Risk Index score, Eagle's clinical markers of low surgical risk, and the probability of postoperative events as determined by Cooperman's equation. There were no cardiac events in 30 patients with normal dipyridamole-thallium scans or in nine patients with fixed myocardial perfusion defects. Of 21 patients with reversible perfusion defects who underwent surgery, nine had a postoperative cardiac event (sensitivity, 100%; specificity, 43%). In the six other patients with reversible defects, preoperative angiography showed severe coronary disease or cardiomyopathy. Thus in patients unable to complete a standard exercise stress test, postoperative outcome cannot be predicted clinically before major general and vascular surgery, whereas dipyridamole-thallium imaging successfully identified all patients who sustained a postoperative cardiac event.

Aged↗
PubMed1990

Standing views to differentiate gallbladder or bile leak from duodenal activity on cholescintigrams.

Confusing a gallbladder or bile leak with duodenal activity is a common source of error in the interpretation of cholescintigrams. Techniques such as supplementary oblique views, delayed views, the "water test," dynamic display and combined cholescintigraphy and ultrasound have been used with varying degrees of success. As illustrated in two cases, supplementary standing views provide a simple alternative method to differentiate gallbladder from small bowel activity.

Adolescent↗
PubMed1990

Superiority of dipyridamole over exercise testing when exercise thallium imaging is limited by angina.

The extent of jeopardized myocardium can be underestimated on stress thallium myocardial perfusion images when exercise tolerance is limited by angina pectoris. A patient's tolerance for pain can influence the degree of myocardial ischemia observed on myocardial perfusion images during effort angina. A case is reported of a patient with angina pectoris showing mild ischemia limited to one myocardial segment on exercise thallium images, but severe and extensive reversible perfusion defects during dipyridamole-thallium imaging, and a 70% stenosis of the left main coronary artery on coronary angiography.

Angina Pectoris↗
PubMed1989

Usefulness of the severity and extent of reversible perfusion defects during thallium-dipyridamole imaging for cardiac risk assessment before noncardiac surgery.

Thallium-dipyridamole imaging is a very sensitive test for predicting cardiac events after noncardiac surgery, but it lacks specificity. To improve specificity, a semiquantitative scoring system was developed that combined dipyridamole-induced reversible left ventricular dilatation with scintigraphic indexes for severity and extent of reversible perfusion defects. Using this scoring system, patients were classified into low, intermediate and high risk subgroups. Thallium-dipyridamole imaging was performed in 66 patients before major general and vascular surgery. Thirty-nine patients classified as low risk (30 with normal scans and 9 with fixed defects) underwent surgery uneventfully. Surgery was cancelled in 6 patients with extensive thallium redistribution and coronary angiography was performed because of severe coronary artery disease in 5 and idiopathic dilated cardiomyopathy in 1. In the remaining 21 patients with thallium redistribution, a positive statistical correlation (p = 0.001) between scintigraphic indexes of severity and extent, and cardiac events was noted. Using cutoff values for the scintigraphic indexes, patients with reversible defects could be classified into intermediate and high risk subgroups. Only 1 of 11 patients at intermediate risk developed a complication, whereas 8 of 10 patients at high risk had a postoperative event (7 deaths and 1 myocardial infarction). Thus, using scintigraphic indexes for severity and extent, patients with reversible defects can be stratified into an intermediate risk subgroup that can safely undergo surgery and a high risk subgroup that requires coronary angiography.

Angiography↗