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Biomedical subjects

R C Hendel

Publications and source records attributed to R C Hendel.

52 records · Page 3Linked to original sources
PubMed1990

Myocardial uptake of indium-111-labeled antimyosin in acute subendocardial infarction: clinical, histochemical, and autoradiographic correlation of myocardial necrosis.

Indium-111-labeled antimyosin has been utilized in the diagnosis and localization of acute transmural myocardial infarction. The present report describes a patient who presented with a massive subendocardial infarction. Two days after the injection of antimyosin, the patient's clinical status markedly deteriorated and he expired. Postmortem examination demonstrated severe three-vessel coronary artery disease with extensive myocyte death in the endocardium. Autoradiography and histochemical staining of the prosected heart demonstrated high correlation for myocardial necrosis and corresponded to clinical evidence for diffuse subendocardial infarction.

Aged↗
PubMed1989

Multiple cholesterol emboli syndrome. Bowel infarction after retrograde angiography.

The two patients described in this article are among the first to have been diagnosed with extensive bowel infarction as a result of cholesterol embolization following cardiac catheterization. The presence of acute hypertension, renal insufficiency, livedo reticularis, and gangrenous skin changes are characteristic manifestations of the multiple cholesterol emboli syndrome. Additionally, gastrointestinal symptoms and melena may herald ischemia and infarction of the alimentary tract. Anticoagulation and thrombolytic therapy are relatively contraindicated in this syndrome and may, in fact, be a precipitating cause. The prognosis is usually poor; however, survival is possible with aggressive medical and surgical therapy, despite extensive infarction of the gastrointestinal tract and other organs. Prevention remains the most critical aspect of management of this potentially catastrophic illness.

Aged↗
PubMed1976

Pancreatitis and severe metabolic abnormalities due to phenformin therapy.

Two elderly diabetic patients with abdominal pain were demonstrated to have complications of phenformin hydrochloride therapy. The first developed severe lactic acidosis treated with sodium bicarbonate given intravenously and followed by rebound alkalosis. The second showed severe acidosis (specimens for lactate determination were unfortunately unsatisfactory for analysis) and similar alkalotic rebound after therapy. She then developed severe pancreatitis, proved at operation, no cause for which other than phenformin was apparent. Poor renal and hepatic function predispose to these conditions by increasing serum phenformin levels and by decreasing urinary excretion of its metabolites. The acidosis should be treated judiciously with sodium bicarbonate administered intravenously. A rebound alkalosis, ensuring as the accumulated lactate is metabolized, is best treated by potassium chloride and ammonium chloride given intravenously. The mechanism by which phenformin causes pancreatitis is unknown, but termination of therapy causes cessation of the pancreatitis.

Acidosis↗
PubMed1971

Actinomycin D; renewed RNA synthesis after removal from mammalian cells.

Suppressed RNA synthesis exceeded control rates 2 hours after removal of actinomycin from serial lines of green monkey kidney cells in exponentially dividing monolayer cultures. Enhanced synthesis was directly related to the dose of actinomycin, and release from inhibition was temperature dependent. A broad range of RNA sizes was made after removal of drug, but cytoplasmic and nucleolar sedimentation profiles were abnormal for at least 20 hours.

Animals↗
PubMedDate not supplied

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. Tetrofosmin is a recently developed 99mTc-labeled agent that has shown promising results in early clinical trials. METHODS AND RESULTS: A multicenter, open-label trial was performed during which treadmill exercise thallium and tetrofosmin scintigraphy was performed within a 2-week period of each other in 216 subjects. Image quality was evaluated subjectively and scans were interpreted in a blinded, independent fashion by four readers. Perfusion abnormalities were graded as consistent with ischemia, infarction, or mixed and were described both globally and regionally. Interobserver variability was assessed by use of the kappa statistic, and receiver-operator curves were compared for each observer for the diagnostic accuracy of each agent. More tetrofosmin images were of excellent quality than with thallium (52% vs 28%; p < 0.05), and when differences in quality were noted between the agents, tetrofosmin was more often superior (p < 0.0001). The interobserver variability was lower with tetrofosmin scintigraphy because generally higher kappa values were noted, especially in the lateral wall. Higher receiver-operator curve areas indicative of improved diagnostic accuracy were noted among the four readers for tetrofosmin in 80% of vascular territories. CONCLUSIONS: 99mTc-labeled tetrofosmin scintigraphy yields images of improved quality compared with thallium, and there is an overall improvement in the consistency of image analysis associated with the use of tetrofosmin.

Coronary Disease↗
PubMedDate not supplied

The value of perioperative clinical indexes and dipyridamole thallium scintigraphy for the prediction of myocardial infarction and cardiac death in patients undergoing vascular surgery.

BACKGROUND: Dipyridamole thallium scintigraphy has previously been shown to have predictive value for both perioperative and late cardiac events in patients undergoing vascular surgery. However, despite the prognostic utility of this technique, the relative importance of clinical factors and scintigraphic information is not well known. The purpose of this study was to evaluate the value of commonly used clinical risk indexes, composed of historic variables, and dipyridamole thallium scintigraphy for predicting perioperative cardiac event-free survival rates. METHODS AND RESULTS: Clinical and scintigraphic variables in 360 patients undergoing vascular surgery were analyzed for their predictive utility for perioperative and late (up to 5 years) cardiac events (nonfatal myocardial infarction or cardiac death) by means of chart review and telephone contact. Patients were correctly categorized as being at low, moderate, or high risk for perioperative cardiac events based on two clinical indexes. Thallium redistribution, however, was a more powerful predictor of cardiac events than these indexes. Even in a clinically low-risk patient cohort, the odds ratio for an event increased by 6- to 8-fold (p < 0.05) if thallium redistribution was noted. These indexes also demonstrated prognostic utility for late cardiac event-free survival rates by life-table analysis (p < 0.001). The presence of a fixed thallium defect was associated with an increased risk of late cardiac events (p < 0.01). When stratified by risk index, in those patients at moderate to high risk who had a fixed defect the odds ratio increased by 3.9- to 5.4-fold (p < 0.001). Likewise, the low-risk subgroup had a 3.9- to 8.2-fold increase in the risk of a late cardiac event when a fixed perfusion defect was present. CONCLUSIONS: Preoperative clinical indexes are predictive of both perioperative and late cardiac events in patients undergoing vascular surgery. However, dipyridamole thallium scintigraphy is more powerful prognostically than these clinical indexes and provides supplemental value to clinical risk stratification.

Adult↗
PubMedDate not supplied

Diagnostic utility of tomographic myocardial perfusion imaging with technetium 99m furifosmin (Q12) compared with thallium 201: results of a phase III multicenter trial.

BACKGROUND: Based on physical properties, 99mTc-labeled perfusion agents offer several advantages over 201Tl for myocardial perfusion imaging. The results of in vivo and experimental studies, along with preliminary experience in human subjects, have shown 99mTc-labeled furifosmin to be a promising new perfusion tracer. The purpose of this study was to evaluate the safety of a new myocardial perfusion agent, 99mTc-labeled furifosmin (Q12), and determine the concordance of furifosmin perfusion scintigraphy to 201Tl imaging. In addition, we sought to determine the normalcy rate of myocardial scintigraphy with furifosmin. METHODS AND RESULTS: One hundred fifty patients constituted the study group in this multicenter trial. Patients underwent exercise testing with furifosmin injected at peak exercise, and tomographic imaging was begun 15 to 30 minutes afterward. After a separate injection, resting images were obtained 3 to 4 hours later. Thallium scintigraphy was performed within 2 weeks of the furifosmin scans, after a similar exercise workload. Patients with a low likelihood of coronary artery disease (n = 39) also underwent furifosmin imaging. All images were processed and displayed in uniform manner and interpreted by a panel of readers. No adverse effects or clinically important laboratory alterations were related to furifosmin imaging. Image quality was slightly better with furifosmin than with thallium. The overall concordance between the perfusion studies was 86% (kappa value = 0.669). The normalcy rate for furifosmin scintigraphy was 100%. CONCLUSIONS: 99mTc-labeled furifosmin is a promising new 99mTc-labeled myocardial perfusion agent, providing diagnostic results similar to those obtained with 201Tl.

Coronary Disease↗
PubMedDate not supplied

Improved diagnostic accuracy of planar imaging with technetium 99m-labeled tetrofosmin compared with thallium-201 for the detection of coronary artery disease.

BACKGROUND: Receiver operating characteristic (ROC) curve analysis provides detailed information about the performance of a diagnostic test. METHODS AND RESULTS: As part of a multicenter phase III trial, 160 patients with known or suspected coronary artery disease underwent planar stress-rest 99mTc-labeled tetrofosmin and stress-redistribution 201Tl imaging within 14 days of each other, to compare the diagnostic accuracy of these imaging modalities by ROC curve analysis. Coronary arteriography was used as the reference standard and greater than 70% stenosis was considered significant. ROC curve analysis showed improved detection of coronary artery disease with 99mTc-labeled tetrofosmin compared with 201Tl, with ROC curve areas of 0.765 versus 0.644, respectively (p = 0.02). 99mTc-labeled tetrofosmin also better identified single-vessel disease in those without previous myocardial infarction (ROC curve areas of 0.684 vs 0.510 for 99mTc-labeled tetrofosmin and 201Tl, respectively; p = 0.04) and enhanced the detection of multivessel disease in those with previous myocardial infarction (ROC curve areas of 0.764 vs 0.638, respectively; p = 0.02). CONCLUSIONS: Detailed assessment of diagnostic performance by ROC curve analysis shows that, for planar imaging, 99mTc-labeled tetrofosmin enhances the detection of coronary artery disease compared with 201Tl.

Adult↗
PubMedDate not supplied

Impact of an abbreviated adenosine protocol incorporating adjunctive treadmill exercise on adverse effects and image quality in patients undergoing stress myocardial perfusion imaging.

BACKGROUND: Limited data are available about the effects of adjunctive treadmill exercise on adverse effects and the image quality of adenosine perfusion imaging. This study compared the incidence of adverse effects and image quality between standard 6-minute adenosine perfusion imaging and a stress test incorporating a 4-minute adenosine infusion with low-level treadmill exercise. METHODS AND RESULTS: Nineteen patients underwent both a 6-minute adenosine technetium-99m sestamibi single photon emission computed tomography (SPECT) imaging study and a 4-minute adenosine Tc-99m sestamibi SPECT study with 6 minutes of simultaneous low-level treadmill exercise. Symptoms were recorded at 1-minute intervals during the stress and recovery periods. Heart-to-liver and heart-to-lung count ratios were determined from anterior planar images. More adverse effects were experienced during the standard adenosine study than during the adenosine study with low-level exercise (2.7+/-1.4 vs. 1.4+/-1.1, P = .0003). The duration adverse effects were experienced was longer during the standard 6-minute adenosine protocol (6.6+/-2.1 minutes vs 3.2+/-2.8 minutes, P<.0001). Additionally, the symptom-severity scores were higher with the standard adenosine study (15.5+/-9.8 vs 4.5+/-5.1, P<.0001). The heart-to-liver ratios were noted to be higher in the 4-minute adenosine protocol with low-level exercise (1.0+/-0.3 vs. 0.6+/-0.2, P = .0003). CONCLUSIONS: In comparison with standard 6-minute adenosine perfusion imaging, a protocol incorporating a 4-minute adenosine infusion with low-level treadmill exercise results in a marked reduction in the quantity and severity of adverse effects and an improvement in image quality.

Adenosine↗
PubMedDate not supplied

Neural network assessment of perioperative cardiac risk in vascular surgery patients.

Neural networks were developed to predict perioperative cardiac complications with data from 567 vascular surgery patients. Neural network scores were based on cardiac risk factors and dipyridamole thallium results. These scores were converted into likelihood ratios that predicted cardiac risk. The prognostic accuracy of the neural networks was similar to that of logistic regression models (ROC areas 76.0% vs 75.8%), but their calibration was better. Logistic regression overestimated event rates in a group of high-risk patients (predicted event rate, 64%; observed rate 30%; n=50, p<0.001). On a validation set of 514 patients, the neural networks still had ROC similar areas to those of logistic regression (68.3% vs 67.5%), but logistic regression again overestimated event rates for a group of high-risk patients. The calibration difference was reflected in the Hosmer-Lemeshow chi-square statistic (18.6 for the neural networks, 45.0 for logistic regression). The neural networks successfully estimated perioperative cardiac risk with better calibration than comparable logistic regression models.

Bayes Theorem↗