Search PubMed⌕ Search

Biomedical subjects

J Lette

Publications and source records attributed to J Lette.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1989

Bone imaging after cementless press fit total hip arthroplasty.

In view of the high rate of loosening of conventional cemented hip prostheses, cementless implants are gaining popularity in Europe and North America. Smooth-surfaced "press fit" prostheses are designed for autolocking in the femoral canal at the time of installation. Fifteen patients were prospectively followed by bone imaging with Tc-99m MDP at three-month intervals after cementless "press fit" hip arthroplasty to define the "normal" distribution of mechanical stress to the surrounding bone, as well as the incorporation of bone allografts used for reconstruction of resorption sites in cases of revision surgery.

Adult↗
PubMed1989

Severe bronchospasm followed by respiratory arrest during thallium-dipyridamole imaging.

We describe the occurrence of sudden severe bronchospasm and respiratory arrest following dipyridamole infusion in a patient with chronic obstructive pulmonary disease predominantly of the emphysematous type. The severe reaction was unexpected because the patient had tolerated well withdrawal of aminophylline derivatives for 48 hours and was receiving chronic prednisone 20 mg qd. Although the diagnostic and prognostic gains from dipyridamole imaging far outweigh the small risk associated with the test, patients with chronic pulmonary obstructive disease must be closely monitored during thallium-dipyridamole imaging.

Aged↗
PubMed1989

Transient mitral regurgitation: an adjunctive sign of myocardial ischemia during dipyridamole-thallium imaging.

A patient developed transient exacerbation of a mitral insufficiency murmur and a reversible posterior wall perfusion defect during dipyridamole-thallium imaging. Coronary angiography showed significant stenoses of both the right and the circumflex coronary arteries that supply the posterior papillary muscle. Cardiac auscultation for transient mitral incompetence, a sign of reversible papillary muscle dysfunction, is a simple and practical adjunctive test for myocardial ischemia during dipyridamole-thallium imaging. It may confirm that an isolated reversible posterior wall myocardial perfusion defect is truly ischemic in nature as opposed to an artifact resulting from attenuation by the diaphragm.

Aged↗
PubMed1989

Apical hypertrophic cardiomyopathy with spontaneous post partum coronary artery dissection.

Primary coronary dissection is usually a catastrophic event with a fatal outcome; less than 20 cases of long term survival have been reported. A 32-year-old woman with apical hypertrophic cardiomyopathy who survived a spontaneous dissection of the left anterior descending coronary artery and acute anterior wall infarction two days postpartum is described. To the authors' knowledge, the simultaneous occurrence of these two rare conditions has never been previously reported. Thallium-dipyridamole imaging was performed to estimate the amount of residual viable myocardium in the infarcted area and to evaluate the hemodynamic significance of the residual luminal narrowing. Myocardial perfusion imaging can be useful to decide on surgical versus conservative treatment of these patients.

Adult↗
PubMed1986

A reproducible radionuclide procedure for measurement of cerebrospinal fluid shunt flow.

A radionuclide technique was developed to obtain reproducible measurements of cerebrospinal fluid flow in Rickham-Holter type shunt systems. In attempting to reproduce previously described radionuclide procedures, we found that different flow rate measurements can be obtained simply by changing the radiotracer injection technique or the method of analysis of the time activity curves which are generated. The importance of these technical pitfalls cannot be over-emphasized, since there is no gold standard to evaluate cerebrospinal fluid flow in vivo. An experimental model with a calibrated Harvard pump and a shunt system filled with normal saline was constructed. Aliquots of 500 microCi of pertechnetate in 0.05 ml of saline were injected serially into the center of Rickham reservoir using a size 28 needle. Time-activity curves were obtained after waiting five min to reach equilibrium, and standard curves of radiotracer clearance vs actual flow for each system used clinically in our institution were generated. In addition, a technique to quantify and thus correct for the small but significant leak of radiotracer which occurs at the site of injection in the reservoir is described. Excellent correlation was obtained between our results and the clinical and radiological findings in a preliminary clinical evaluation.

Cerebrospinal Fluid↗
PubMed1986

Thallium-201 myocardial imaging during pharmacologic coronary vasodilation: comparison of oral and intravenous administration of dipyridamole.

Although the diagnostic utility of thallium-201 myocardial imaging after dipyridamole infusion is well established, the intravenous form of the drug is not yet commercially available in North America. Fifty patients referred for coronary angiography were prospectively studied. Within a 2 week period, each patient underwent cardiac catheterization and thallium-201 myocardial imaging after both oral and intravenous dipyridamole administration. For the oral protocol, patients were randomly assigned to treatment with either 200 or 400 mg of dipyridamole in tablet form. Coronary artery stenoses of 70% or greater were considered significant. For the 25 patients who received a 200 mg oral dose of dipyridamole, the scintigraphic study showed perfusion defects in 65% of patients with significant coronary artery disease after the oral dose and in 85% of patients after the intravenous dose. For the 25 patients who received a 400 mg oral dose, the sensitivity of the scintigram was 84% after the oral dose and 79% after the intravenous dose. Except for headache and nausea, side effects were less severe and less frequent with oral (either 200 or 400 mg) than with intravenous dipyridamole. Because of the delayed and variable absorption of dipyridamole tablets, the oral studies required a longer period of medical supervision (45 to 60 minutes), and aminophylline was empirically administered after completion of the first set of thallium-201 images. It is concluded from this study that thallium-201 myocardial imaging after coronary vasodilation with a 400 mg oral dose of dipyridamole is a safe, widely available and reliable alternative for the evaluation of coronary artery disease in patients unable to achieve an adequate exercise level on stress testing.

Administration, Oral↗
PubMed1984

Rebound of vasospastic angina after cessation of long-term treatment with nifedipine.

The beneficial effect of calcium antagonists in the treatment of vasospastic angina is now well recognized. Although withdrawal symptoms have been reported following abrupt cessation of therapy with some cardiovascular drugs, there is no detailed report on similar complications of the cessation of therapy with calcium antagonists. In a 4-month period eight patients with well documented and well controlled vasospastic angina experienced a marked increase in the frequency and duration of anginal episodes at rest following the involuntary cessation of treatment with nifedipine, 10 to 20 mg four times a day. The increase began within 2 to 5 days after the cessation of treatment. Substitute therapy with isosorbide dinitrate, 30 mg, and verapamil, 80 to 120 mg, each four times a day, was effective in all cases. Although the mechanism responsible for this rebound phenomenon is not known, awareness of its existence is essential considering the widespread use of calcium antagonists.

Adult↗