Dipyridamole Thallium Imaging Research Articles

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 < 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.

Perioperative myocardial ischaemia and infarction in non-cardiac surgical patients

Summary Cardiovascular morbidity and mortality associated with non-cardiac surgery increase with the probability and severity of coronary artery disease in the surgical population. In the absence of coronary artery disease, the risk of a perioperative cardiac event is negligible. Preoperative evaluation of patients should always include a thorough history and clinical examination but specific investigations should be individualized as false-positive results are common when the incidence of coronary artery disease is low. Recent myocardial infarction, symptoms suggestive of unstable angina and the presence of heart failure are powerful predictors of perioperative cardiovascular morbidity. A routine 12-lead electrocardiogram should be obtained for all men over 40 years and for all women over 55 years as well as for all patients with a history suggestive of heart disease. Stress testing, with or without thallium, is useful for patients with peripheral vascular disease, and dipyridamole-thallium imaging may be of value in risk stratification for those patients in whom adequate exercise levels cannot be achieved. The risk of a cardiovascular event during surgery can be stratified using a ‘risk index’. Coronary angiography allows precise definition of the coronary anatomy and accurate assessment of left ventricular function but this is usually reserved for patients with severe symptoms or for those found to be at high risk as a result of provocative testing, where it is felt that revascularization of the myocardium may be indicated before the proposed surgery. Every effort should be made to treat any reversible risk factors that arepresent (unstable angina, heart failure, etc.) before surgery, with the aim of decreasing perioperative morbidity and mortality. In general, all cardiac medications should be continued throughout the perioperative period unless specific complications occur necessitating their withdrawal. Throughout the stress of the perioperative period myocardial oxygen delivery must be maintained while myocardial oxygen consumption should be kept at a low level. Myocardial ischaemia is common in patients with coronary artery disease during anaesthetic inducation and perioperative infarction occurs largely in those patients who develop significant tachycardia, hypotension or hypertension during surgery, the risk of infarction being increased three-fold when perioperative ischaemia occurs. Monitoring of the cardiac rhythm, arterial pressure, ST segment changes and, in high-risk patients, more sophisticated parameters of cardiac function, will allow for the early diagnosis of myocardial ischaemia and allow therapy to be monitored. Anaesthetic risk cannot be eliminated but can be minimized. The anaestheticagents and technique can be tailored to a patient's cardiovascular status but much will also depend on the anaesthetist's experience and expertise. Even with the best management there will be circumstances when myocardial ischaemia and infarction will occur and successful management will depend upon recognition and treatment. Careful monitoring can help diagnose myocardial ischaemia but infarction may be difficult to diagnose unless there is a high index of suspicion. It is often not possible to obtain a history and the standard investigations such as the 12-lead electrocardiogram and cardiac enzymes can be difficult to interpret. Radionuclide techniques and echocardiography can be helpful. The initial treatment of myocardial ischaemia and infarction in the perioperative period is identical, with nitrates, β-blocking drugs, aspirin and calcium antagonists being used. Thrombolytic therapy is contraindicated during and immediately after surgery. A combination of improved anaesthetic agents and techniques, togetherwith advances in the treatment of coronary artery disease, appear to be making surgery safer for patients with heart disease.

Postoperative myocardial infarction and cardiac death: Predictive value of dipyridamole-thallium imaging and five clinical scoring systems based on multifactorial analysis : Lette J, Waters B, Lassonde J, et al: Ann Surg 211:84–90, 1990

Postoperative myocardial infarction and cardiac death: Predictive value of dipyridamole-thallium imaging and five clinical scoring systems based on multifactorial analysis : Lette J, Waters B, Lassonde J, et al: Ann Surg 211:84–90, 1990

Prognostic value of intravenous dipyridamole thallium imaging in patients with diabetes mellitus considered for renal transplantation

Patients with diabetes and end-stage renal failure are known to have a high risk for cardiac morbidity and mortality associated with renal transplantation. The most efficient method to determine preoperative cardiac risk has not been established. To determine the effectiveness of intravenous dipyridamole thallium imaging in predicting cardiac events, 40 diabetic renal transplant candidates were studied preoperatively in a prospective trial. The study group consisted of 40 patients whose average age was 42 years (range 27 to 64); 34 (85%) were hypertensive and 21 (53%) were cigarette smokers. Cardiac history included chest pain in 6 patients and prior myocardial infarction in 3 patients. Dipyridamole thallium imaging showed reversible defects in 9 patients, fixed defects in 8 patients and normal scans in 23 patients. Dlpyridamole thallium imaging was performed using 0.56 mg/kg of dipyridamole infused intravenously over 4 minutes. Cardiac events occurred only in patients with reversible thallium defects, of which there were 6. Of these 6 patients, 3 had cardiac events before transplantation and 3 had them in the early postopera tive phase (within 6 weeks of surgery). Of 21 patients who underwent renal transplantation, 3 had cardiac events within 6 weeks of transplantation. The average duration of follow-up was 11 months (range 1 to 21). Thus, dipyridamole thallium imaging is an effective method of identifying renal transplant candidates likely to develop cardiac complications. Routine coronary angiography may not be necessary to screen all renal transplant candidates for coronary artery disease before surgery.

The safety of intravenous dipyridamole thallium myocardial perfusion imaging. Intravenous Dipyridamole Thallium Imaging Study Group.

Clinical data on 3,911 patients were collected from 64 individual investigators to evaluate the safety of intravenous dipyridamole-thallium imaging as an alternative to exercise thallium imaging for the evaluation of coronary artery disease. There were two deaths because of myocardial infarctions, two nonfatal myocardial infarctions, and six cases of acute bronchospasm. Chest pain occurred in 770 patients (19.7%). Headache and dizziness were reported by 476 patients (12.2%) and 460 patients (11.8%), respectively. ST-T changes on the electrocardiogram were seen in 292 patients (7.5%). Use of parenteral aminophylline to treat adverse events associated with intravenous dipyridamole brought complete relief of symptoms in 439 of 454 patients (96.7%). There is a potential for increased risk for serious ischemic events in patients with a history of unstable angina who are administered intravenous dipyridamole. In patients with acutely unstable angina (i.e., continuing chest pain) or in the acute phase of myocardial infarction, use of intravenous dipyridamole in thallium scintigraphy should be avoided. There is also an increased risk for bronchospasm in patients with a history of asthma; acute bronchospasm can be relieved immediately by administration of aminophylline. These results demonstrate that intravenous dipyridamole-thallium scintigraphy is a relatively safe, noninvasive technique for the evaluation of coronary artery disease.

Is dipyridamole-thallium imaging preferable to submaximal exercise thallium testing for risk stratification after thrombolysis?

We describe a patient who underwent thrombolysis for acute inferior wall myocardial infarction with only a small ischemic area on the submaximal exercise thallium test but multiple severe perfusion defects on dipyridamole-thallium imaging

Thallium-201 uptake by the lungs during oral dipyridamole Thallium-201 imaging

Thallium-201 uptake by the lungs during oral dipyridamole Thallium-201 imaging

Dipyridamole thallium imaging may not be a reliable screening test for coronary artery disease in patients undergoing vascular surgery

Dipyridamole thallium imaging has been proposed for cardiac risk stratification in patients undergoing peripheral vascular surgery. The purpose of this study was to define the benefit of this investigation in routine preoperative evaluation of these patients. The outcome of 86 patients undergoing vascular surgery procedures was examined in light of preoperative clinical assessment and dipyridamole SPECT thallium imaging (DST). Fifty-one patients (59%) were considered at high risk on clinical grounds, and 22 patients (26%) had perfusion defects. Ten patients suffered a perioperative coronary event, including unstable angina, myocardial infarction, or cardiac death. Seven of the patients with such events were among the 51 clinically high-risk subjects (14%). Three perioperative events occurred in the group of 19 patients with positive DST images who underwent surgery (16%), but the DST test failed to identify 7 patients who suffered coronary events. The frequency of abnormal thallium imaging was similar to the prevalence of angiographically significant coronary disease reported previously at this center, but considerably less than the rate of abnormal thallium imaging in past studies of vascular surgery patients. The application of the test to a low to moderate risk population is probably responsible for its lower predictive accuracy for coronary events. DST is not an ideal routine noninvasive technique for risk stratification in patients undergoing vascular surgery.

Nonexercise Stress Thallium Imaging Using Dipyridamole Coronary Vasodilation

Pharmacologic stress testing using dipyridamole thallium imaging is emerging as a useful alternative to exercise thallium testing in patients who are unable to perform adequate exercise. In this review we summarize the mechanism of dipyridamole’s affect, the hemodynamic and clinical observations frequently associated with dipyridamole thallium testing and discuss clinical protocols for test performance. In addition, we review studies which have compared dipyridamole thallium testing with exercise thallium imaging. Finally, we discuss the clinical instances where dipyridamole thallium imaging is especially useful as well as some of the side effects and limitations of this technique.

Prognostic value of dipyridamole thallium scintigraphy for evaluation of ischemic heart disease

Exercise testing alone or in combination with thallium scintigraphy has significant prognostic value. In contrast, dipyridamole thallium imaging is not dependent on patients achieving adequate levels of exercise, but no long-term prognostic studies have been reported. Accordingly, imaging results of 516 consecutive patients referred for dipyridamole thallium studies were correlated with subsequent cardiac events, death (n = 23) and myocardial infarction (n = 43) over a mean follow-up period of 21 months.Patients with a history of congestive heart failure, prior myocardial infarction, diabetes mellitus or abnormal scans were significantly more likely to have a cardiac event (p < 0.03). With use of logistic regression analysis, an abnormal scan was an independent and significant predictor of subsequent myocardial infarction or cardiac death and increased the relative risk of any event more than threefold. The presence of redistribution on thallium scanning further increased the risk of a cardiac event. Survival analysis demonstrated a significant difference between patients with an abnormal or normal thallium scan over a 30 month period.In conclusion, dipyridamole thallium scintigraphy demonstrates prognostic value in a large unselected population and may be an adequate clinical alternative to physiologic exercise testing in the evaluation of coronary heart disease.

Postoperative Myocardial Infarction and Cardiac Death

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.

Dipyridamole thallium imaging for detecting cardiac involement in patients with systemic sclerosis (scleroderma)

Dipyridamole thallium imaging for detecting cardiac involement in patients with systemic sclerosis (scleroderma)

Validation of Dipyridamole Thallium Imaging by Coronary Angiography in the Noninvasive Assessment of Coronary Artery Disease

Validation of Dipyridamole Thallium Imaging by Coronary Angiography in the Noninvasive Assessment of Coronary Artery Disease

Assessment of Cardiac Risk in Patients with Peripheral Vascular Disease - Role of Dipyridamole Thallium Imaging

Assessment of Cardiac Risk in Patients with Peripheral Vascular Disease - Role of Dipyridamole Thallium Imaging

Prognostic importance of silent myocardial ischemia detected by intravenous dipyridamole thallium myocardial imaging in asymptomatic patients with coronary artery disease

One hundred seven asymptomatic patients who underwent intravenous dipyridamole thallium imaging were evaluated to determine prognostic indicators of subsequent cardiac events over an average follow-up period of 14 ±10 months. Univariate analysis of 18 clinical, scintigraphic and angiographic variables revealed that a reversible thallium defect, a combined fixed and reversible thallium defect, number of segmental thallium defects and extent of coronary artery disease were significant predictors of subsequent cardiac events. Of the 13 patients who died or had a nonfatal infarction, 12 had a reversible thallium defect.Stepwise logistic regression analysis selected a reversible thallium defect as the only significant predictor of cardiac events. When death or myocardial infarction was the outcome variable, a combined fixed and reversible thallium defect was the only predictor of outcome. In patients without previous myocardial infarction, the cardiac event rate was significantly greater in those with an abnormal versus normal thallium scan (55% versus 12%, p < 0.001).Thus, intravenous dipyridamole thallium scintigraphy is a useful noninvasive test to risk stratify asymptomatic patients with coronary artery disease. A reversible thallium defect most likely indicates silent myocardial Ischemia in a sizable fraction of patients in this clinical subset and is associated with an unfavorable prognosis.

Prognostic utility of predischarge dipyridamole-thallium imaging compared to predischarge submaximal exercise electrocardiography and maximal exercise thallium imaging after uncomplicated acute myocardial infarction

The prognostic value of predischarge dipyridamolethallium scanning after uncomplicated myocardial infarction was determined by comparison with submaximal exercise electrocardiography and 6-week maximal exercise thallium imaging and by correlation with clinical events. Two endpoints were defined: cardiac events and severe ischemic potential. Of the 40 patients studied, 8 had cardiac events within 6 months (1 died, 3 had myocardial infarction and 4 had unstable angina requiring hospitalization). The finding of any redistribution on dipyridamole-thallium scanning was common (77%) in these patients and had poor specificity (29%). Redistribution outside of the infarct zone, however, had equivalent sensitivity (63%) and better specificity (75%) for events (p < 0.05). Both predischarge dipyridamole-thallium and submaximal exercise electrocardiography identified 5 of the 8 events (p = 0.04 and 0.07, respectively). The negative predictive accuracy for events for both dipyridamole-thallium and submaximal exercise electrocardiography was 88%. In addition to the 8 patients with events, 16 other patients had severe ischemic potential (6 had coronary bypass surgery, 1 had inoperable 3-vessel disease and 9 had markedly abnormal 6-week maximal exercise tests). Predischarge dipyridamole-thallium and submaximal exercise testing also identified 8 and 7 of these 16 patients with severe ischemic potential, respectively. Six of the 8 cardiac events occurred before 6-week follow-up. A maximal exercise thallium test at 6 weeks identifed 1 of the 2 additional events within 6 months correctly. Thallium redistribution after dipyridamole in coronary territories outside the infarct zone is a sensitive and specific predictor of subsequent cardiac events and identifies patients with severe ischemic potential. Because events recur early after uncomplicated myocardial infarction, predischarge testing is recommended. Dipyridamole-thallium scanning is an acceptable alternative to submaximal exercise testing for risk stratification in patients who are unable to exercise.

Acute pulmonary edema caused by prolonged myocardial stunning after Dipyridamole-Thallium imaging

D ipyridamole-thallium imaging is routinely used in clinical practice to detect coronary artery disease in patients unable to exercise. Major side effects such as prolonged ischemia or symptomatic hypotension are uncommon and respond rapidly to administration of intravenous aminophylline [1]. Catastrophic events such as myocardial infarction or cardiac arrest have been reported but are not common [2,3]. We describe a unique case of myocardial stunning (defined as prolonged but reversible post-ischemic regional ventricular dysfunction [4]) and acute pulmonary edema during dipyridamole-thallium imaging.

Acute hemodynamic changes during intravenous dipyridamole thallium imaging early after infarction

In order to determine the safety and hemodynamic effects of intravenous dipyridamole infusion for thallium-201 scintigraphy in patients with acute ischemic syndromes, 10 patients with recent uncomplicated myocardial infarction (7 ± 2 days pre-test) had central pressures and cardiac output values measured serially in a coronary care unit during and after the administration of dipyridamole (0.56 mg/kg over 4 minutes) and following aminophylline reversal (50 to 150 mg intravenously) of dipyridamole effect. Cardiac medications were not discontinued. Double product did not change significantly (8522 ± 1811 versus 9044 ± 1701; p = NS). Serious ischemic events did not occur, although 20% of patients had noncardiac side effects and 30% developed ≥ 1 mm ST segment depression with associated angina in one-third of these cases. The peripheral blood pressure and heart rate response did not predict the occurrence of myocardial ischemia. Dipyridamole significantly reduced systemic vascular resistance (1218 ± 302 to 739 ± 166 dyne/sec −1/cm −5; p < 0.05) and increased cardiac index (3.1 ± 0.7 to 4.7 ± 1.0 L/min/m 2; p < 0.05) within approximately 10 minutes, in association with a significant increase in pulmonary capillary wedge pressure (13 ± 5 to 17 ± 6 mm Hg; p < 0.05). Three patients developed silent new “V” waves in their pulmonary capillary wedge pressure tracing, associated with anterior thallium redistribution. All three patients with newly elevated wedge pressures (>15 mm Hg) had both thallium-201 redistribution and multivessel coronary disease. A ≥3 mm Hg increase in wedge pressure (mean increase = 6 ± 3 mm Hg) occurred in five of eight (63%) patients with multivessel disease and in five of six (83%) patients with thallium-201 redistribution, while patients with single-vessel disease and no thallium-201 redistribution had a mean wedge increase of 2 ± 1 mm Hg. Aminophylline promptly reversed the hemodynamic effects of dipyridamole to baseline values, including new “V” waves. In summary, dipyridamole induces important hemodynamic changes similar to those occurring in spontaneous or exercise-induced angina that are not blunted by autonomically active drugs or reflexes in this early post-infarction setting. Early (≤7 day) post-infarction testing provides time- and cost-effective risk stratification, saving an average of 4 hospital days and $1843 ± $1181 per patient. As with any diagnostic intervention with the potential to induce myocardial ischemia during risk stratification, this test should be cautiously monitored, especially in patients with recent acute ischemic syndromes.

A comparison of dipyridamole-thallium imaging and exercise testing in the prediction of postoperative cardiac complications in patients requiring arterial reconstruction

The individual and combined predictive values of dipyridamole-thallium imaging and exercise testing were compared in a prospective study of 70 patients who had abdominal aortic aneurysms or aortoiliac occlusive disease that required surgical repair. All patients were evaluated clinically by the same cardiologist and had exercise stress testing and dipyridamole-thallium imaging before admission for surgery. Ten patients were excluded from the study because they had evidence of severe ischemia when tested (ST segment depression >2 mm on exercise testing, severe multivessel disease on thallium imaging). The remaining 60 patients were operated on (abdominal aortic aneurysm repair, 40; aortobifemoral repair, 17; femorofemoral graft, 3). The test results were withheld from the surgeon, anesthetist, and cardiologist before surgery. A total of 22 patients experienced major cardiac complications postoperatively (acute pulmonary edema, 17; acute myocardial, infarction, 5; cardiac death, 2). Thallium imaging showed myocardial ischemia in 3160 patients. Exercise testing was positive (⩾1 mm ST segment depression) in 1060 patients. Dipyridamole-thallium imaging with a high sensitivity and reasonable specificity is the initial test of choice. Exercise testing is a poor screening test because of its low sensitivity. The combination of the two tests gives the highest positive predictive value and the greatest likelihood ratio. Thus patients assessed initially and found to have positive thallium scan results may be further stratified by exercise testing.

A comparison of dipyridamole-thallium imaging and exercise testing in the prediction of postoperative cardiac complications in patients requiring arterial reconstruction

A comparison of dipyridamole-thallium imaging and exercise testing in the prediction of postoperative cardiac complications in patients requiring arterial reconstruction