Safety of intravenous dipyridamole for stress testing with thallium imaging

Cardiac and noncardiac side effects were studied in 293 consecutive patients referred for nonexercise stress thallium imaging with intravenous dipyridamole. Six minutes after the initiation of infusion, there was a mean 9-beat/min increase in heart rate and a mean 12-mm Hg decrease in systolic blood pressure. The largest increase in heart rate exceeded 20 beats/min in only 13% of patients and the largest decrease in systolic blood pressure exceeded 20 mm Hg in 31%. Noncardiac side effects were headache (11%), lightheadedness or dizziness (5%) and nausea (4%). Only 9 patients required intravenous aminophylline for relief of noncardiac side effects: severe headache in 7 and nausea in 2. Cardiac side effects included chest pain in 76 patients (26%), of whom 70% were given aminophylline for relief of symptoms. Sixty patients (20%) had ischemic ST-segment depression and 56 (19%) had arrhythmias (ventricular in 50 and atrial in 6). There were no deaths, myocardial infarctions or sustained arrhythmias due to dipyridamole administration. Among 62 patients also undergoing cardiac catheterization, side effects except for arrhythmias were unrelated to the number of vessels with coronary artery disease. Intravenous dipyridamole is safe for nonexercise stress testing and has few serious side effects. However, the possibility of ischemia requires careful selection of patients and monitoring of vital signs and the electrocardiogram during the test.     

Comparison of intravenous dipyridamole thallium cardiac imaging with exercise radionuclide angiography

Sixty-eight patients underwent dipyridamole thallium imaging and exercise blood pool imaging in order to determine the functional significance of various dipyridamole thallium imaging redistribution patterns. Serial thallium images and blood pool regional wall motion were interpreted by three independent observers. Rest and exercise left ventricular ejection fractions were calculated by two observers and were averaged. Transient thallium defects were associated with normal rest and exercise left ventricular ejection fraction and regional wall motion. Mild persistent thallium defects were associated with normal ejection fraction and regional wall motion at rest, with a deterioration in both with exercise. Severe persistent thallium defects were associated with reduced ejection fraction and regional wall motion at rest, but no further deterioration with exercise. These data support the following postulates: Transient dipyridamole thallium defects are due to mild coronary artery stenoses that cause no detectable functional consequence during levels of exercise achieved in this study. Mild persistent defects are due to more severe stenoses that do cause a functional reduction in wall motion during exercise. Although appearing qualitatively persistent, these defects probably represent very slow thallium redistribution and ischemia rather than scar. Finally, severe persistent defects probably represent myocardial scar.     

Combined arm exercise and dipyridamole stress thallium imaging for the detection of coronary artery disease

The safety and usefulness of combined isotonic-isometric arm exercise along with dipyridamolethallium 201 imaging for the detection of coronary artery disease (CAD) was tested in 50 patients. Dipyridamole (0.5 mg/kg) was injected i.v. for 4 minutes, followed by a 4-minute exercise of both arms. Fifty matched patients receiving dipyridamole only were imaged for comparison. Peak heart rate (mean 118 vs 77 b/minutes) and peak systolic and diastolic blood pressure were significantly higher in the exercised group. Evidence of myocardial ischemia, ST depression (82% vs 60%), Th-201 redistribution (85% vs 68%), and the target-to-background counts ratio were also more profound in this group, though side effects were fewer. It is concluded that arm exercise combined with dipyridamole-thallium imaging is safe and provides more reliable results in assessing CAD than dipyridamole alone followed by Th-201 imaging. It is therefore recommended for patients who are unable to perform lower limb exercise.Presented at the 35th World Congress, International College of Angiology, Copenhagen, Denmark, July 1993     

Prolonged myocardial ischemia after intravenous dipyridamole thallium imaging

Intravenous dipyridamole thallium imaging is reported to be a safe test with minimal side effects. It has been proposed by some that the test simply dilates the coronary vessels without actually producing myocardial ischemia. In this report, we describe a patient who, following intravenous dipyridamole thallium imaging, developed severe myocardial ischemia which persisted for 90 minutes, requiring emergency coronary angioplasty to alleviate the ischemic insult. Sequential electrocardiograms and cardiac isoenzyme levels following coronary angioplasty were within normal limits. Thus, severe myocardial ischemia following intravenous dipyridamole testing can occur and emphasizes the importance of careful monitoring of these patients, particularly when the pretest risk of coronary disease is high.     

Usefulness of oral dipyridamole suspension for stress thallium imaging without exercise in the detection of coronary artery disease

Stress thallium imaging with intravenous dipyridamole permits assessment of coronary artery disease (CAD) without the need for exercise. However, intravenous dipyridamole is available in the United States only on an experimental basis. To study the use of oral dipyridamole as a clinically available alternative to intravenous dipyridamole for this purpose, 100 patients underwent thallium imaging with oral dipyridamole. Each patient received 300 mg of pulverized tablets in a 30-ml suspension. Maximal increase in mean heart rate and decrease in mean blood pressure occurred 30 minutes after ingestion. At 45 minutes, 2 mCi of thallium was given intravenously and serial imaging was begun within 7 minutes. The serum dipyridamole level (mean +/- standard deviation) 45 minutes after 300 mg was administered orally (3.7 +/- 2.2 micrograms/ml) was similar to that 5 minutes after 0.56 mg/kg was given intravenously (4.6 +/- 1.3 micrograms/ml). Fifty-five patients had some adverse effects between 15 and 75 minutes after oral ingestion, including nausea, headache, dizziness, chest pain (25 patients) and electrocardiographic changes (14 patients). Intravenous aminophylline was used to resolve these adverse effects in 21 patients. There were no severe arrhythmias, myocardial infarctions or deaths. Of the 43 patients with angiographically documented CAD, 39 had an initial perfusion defect that redistributed on the delayed images. When the results in patients who had undergone catheterization were analyzed by individual segment, the presence of thallium redistribution was associated with normal or hypokinetic contrast left ventriculographic wall motion of that segment, whereas the presence of a persistent defect was associated with akinesia or dyskinesia (Fisher's standardized Z = 9.14).(ABSTRACT TRUNCATED AT 250 WORDS)     

Geriatric cardiology: when exercise stress testing is justified

Short exercise duration is not necessarily ominous in an older patient unless other significant abnormalities, such as ST-segment depression or arrhythmias, are associated. Problems peculiar to the elderly during exercise testing--appearance of fatigue and lightheadedness due to muscle weakness and deconditioning, vasoregulatory insufficiency, and a tendency to unsteadiness of gait--may require physical or emotional support.     

Use of isometric exercise to enhance the diagnostic value of dipyridamole testing in patients with angina pectoris]

A dipyridamole test was performed in 40 patients with coronary heart disease who were divided into 2 groups, each consisting of 20 subjects. The dipyridamole test alone was performed in the patients from Group 1, while the agent was given by using manual dynamometry and increasing venous return in those from Group 2. Positive results were obtained in 55 and 85%, respectively (p less than 0.05). The mean dipyridamole dose was 0.64 mg/kg for Group 1 patients and 0.48 mg/kg for Group 2 patients (p less than 0.05).     

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 scinitigraphy 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 greater than or equal to 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 less than 0.05) and increased cardiac index (3.1 +/- 0.7 to 4.7 +/- 1.0 L/min/m2; p less than 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 less than 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 (greater than 15 mm Hg) had both thallium-201 redistribution and multivessel coronary disease.(ABSTRACT TRUNCATED AT 250 WORDS)     

Submaximal exercise testing after unstable angina

Sixty-one consecutive men, mean age 56 years, who fulfilled criteria for unstable angina and who responded to medical therapy, underwent submaximal exercise testing prior to hospital discharge and at least 3 days after their last episode of angina. Forty-two patients were receiving propranolol at the time of exercise. Submaximal exercise was targeted to 120 beats/minute and strict criteria for the premature termination of each study were followed. Follow-up data were available on 55 patients post-discharge over a period of 6 to 36 weeks.No patient suffered recurrence of unstable angina or myocardial infarction due to the exercise test. Exercise was prematurely terminated by an ischemic response (chest pain and/or ST segment changes) in 34 patients (56%) and by leg fatigue in 13 patients (21%). Only five patients had exercise-induced ventricular ectopic activity, four of whom were not receiving propranolol. Nine patients achieved the target heart rate. Exercise-induced abnormal electrocardiographic changes predicted the postdischarge recurrence of episodes of unstable angina (p < 0.05). Comparison of predischarge submaximal exercise data with postdischarge maximal exercise shows that recovery in cardiovascular function after unstable angina occurs soon after stabilization and prior to the submaximal test.     

Superiority of 24-hour outpatient monitoring over multi-stage exercise testing for the evaluation of syncope.

Twenty-four hour outpatient monitoring was compared with maximum multi-stage Treadmill exercise testing for the detection of dysrhythmias producing syncope or near syncope in 119 patients. All patients had cardiovascular disorders; only 21% had coronary artery disease. Patients with obvious cause of syncope and/or significant dysrhythmias by resting electrocardiograms (ECGs) were excluded. A significant dysrhythmia was found which was considered the probable cause of syncope or pre-syncope in 76 patients (64%). A non-cardiac cause was found in tachycardia, exercise testing identified only patients with complex ventricular dysrhythmias and missed 64% of these. Overall, dysrhythmias were found by ambulatory monitoring alone in 63 patients, by exercise testing alone in only three, and by both in 10. It is concluded that: 1) in the majority of patients with syncope or pre-syncope suspected to be of a cardiac origin, a dysrhythmia can be found; 2) ambulatory monitoring is far superior to exercise testing for detection of dysrhythmias; 3) exercise testing increases the yield for complex ventricular dysrhythmias.     

Reverse redistribution of thallium-201 detected by SPECT imaging after dipyridamole in angina pectoris

Reverse redistribution refers to a thallium-201 perfusion defect that develops or becomes more evident on delayed imaging compared with the initial image immediately after stress. To determine the diagnostic importance of reverse redistribution after intravenous dipyridamole, thallium-201 single photon emission computed tomography and quantitative coronary arteriography were performed in 90 men with angina pectoris. Of the 250 myocardial segments analyzed, reverse redistribution was present in 17 (7%). Minimal coronary cross-sectional area in proximal vessel segments was less than or equal to 2.0 mm2 more often in regions with transient perfusion abnormalities than in regions with reverse redistribution (66 vs 29%, p less than 0.05). Compared with regions exhibiting transient perfusion abnormalities, regions with reverse redistribution had larger proximal arterial diameters (1.9 +/- 1.1 vs 1.3 +/- 1.1 mm, p less than 0.001) and cross-sectional areas (3.9 +/- 3.1 vs 2.2 +/- 2.6 mm2, p less than 0.001). Coronary artery dimensions and relative stenosis severity did not differ between those regions with normal perfusion and those with reverse redistribution. Reverse redistribution detected by thallium-201 single photon emission computed tomographic imaging after dipyridamole is uncommon, appears to occur as frequently in normal subjects as in patients undergoing coronary arteriography and does not indicate the presence of severe coronary artery disease.     

Prediction of late cardiac events by dipyridamole thallium imaging in patients undergoing elective vascular surgery.

Dipyridamole thallium scintigraphy has previously been shown to have prognostic value in the preoperative assessment of patients scheduled to undergo vascular surgery, but its effect on the long-term outcome is less well-defined. In the largest series to date, dipyridamole thallium scanning was performed in 360 patients before elective vascular surgery and survivors were followed for a mean of 31 months. In the 327 patients who underwent vascular surgery, operative death and nonfatal myocardial infarction occurred in 4.9 and 6.7%, respectively. A cardiac event (nonfatal myocardial infarction or cardiac death) occurred in 14.4% of patients with a transient thallium defect, as opposed to 1% with a normal scan (p < 0.001). Logistic regression analysis revealed that the best predictor of a perioperative event was the presence of a reversible thallium defect, elevating the risk by 4.3-fold. Late cardiac events occurred in 53 (15.2%) surgical survivors or nonsurgically treated patients. Patients with a fixed perfusion abnormality had a 24% late event rate, compared with 4.9% in those with a normal dipyridamole thallium study (p < 0.01). Cox analysis demonstrated that a fixed thallium defect was the strongest factor for predicting a late event and increased the relative risk by almost fivefold. A history of congestive heart failure was the only significant variable that contributed additional value to that of a fixed defect alone. Life-table analysis confirmed the strong relation of a fixed defect to cardiac event free survival (p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Prognostic value of dipyridamole thallium imaging after acute myocardial infarction in older patients

OBJECTIVE: To assess the utility of intravenous dipyridamole thallium testing for predicting major cardiac events following acute myocardial infarction in older patients. DESIGN: Prospective cohort study with a median follow-up of 18 months. SETTING: A university teaching hospital. PARTICIPANTS: 73 patients aged 65 years and older with enzymatically confirmed acute myocardial infarction (mean age 75 years, 56% male, 71% white). MEASUREMENTS: All patients underwent a detailed clinical assessment, an echocardiogram, and an intravenous dipyridamole thallium stress test before hospital discharge. The study endpoint was death or nonfatal reinfarction during the follow-up period. RESULTS: Overall, 24 patients (33%) died or developed recurrent myocardial infarction during follow-up. Among 44 patients with a reversible thallium defect, 19 (43%) reached the study endpoint, compared with only five of 29 patients (17%) without reversible ischemia (P = .04). On multivariate analysis, independent prognostic variables included non-use of aspirin at hospital discharge (P = .002), decreased left ventricular systolic function (P = .009), non-use of a beta-blocker at hospital discharge (P = .013), and reversible ischemia on thallium scintigraphy (P = .025). The relative risks for death or reinfarction associated with non-use of aspirin, non-use of a beta-blocker, left ventricular dysfunction, and reversible ischemia were 2.65, 2.39, 2.01, and 2.51, respectively. Patients with three or four of these risk factors had an 83% probability of death or reinfarction, compared with 41% in patients with two risk factors and 6% in patients with one or no risk factor (P < .001). CONCLUSION: Intravenous dipyridamole thallium imaging provides independent prognostic information in older patients with acute myocardial infarction. Moreover, the combination of clinical, echocardiographic, and dipyridamole thallium variables effectively stratifies older postinfarction patients into high-, intermediate-, and low-risk categories for death or recurrent myocardial infarction.     

Role of exercise thallium 201 imaging in decision making

This prospective study examined the impact of results of exercise thallium 201 imaging on the estimation of probability of coronary artery disease (CAD) and patient management among cardiologists and internists in our institution. Before exercise testing, the probability of CAD in the 100 patients enrolled in this study was considered low in 31, intermediate in 28, and high in 41 patients. The probability of CAD after exercise thallium imaging was different in four patients (10%) in the high group, 22 patients (79%) in the intermediate group, and three patients (10%) in the low group. Further, the results of exercise testing resulted in changes in patient management in 29 patients (71%) in the high group, 26 patients (93%) in the intermediate group, and 16 patients (52%) in the low group. Overall, the management changed in 71% of the patients. This change included changes in medications, physical activity, frequency of office visits, need for cardiac catheterization, and need for coronary arterial bypass grafting. Thus, exercise thallium imaging is useful in clinical decision making: the diagnostic certainty is improved in patients with intermediate pretest probability of CAD; and some degree of change in patient management is observed, even in patients in whom the probability of CAD is not altered.     

Verbal conditioning of angina pectoris during exercise testing

A 40 year old man with far advanced coronary heart disease consistently experienced pain and exhibited marked S-T segment depression after 44 crossings during a Master two-step test. When the number of times traversed was miscounted so that he exercised less, the pain occurred at the precise count of 44 and he showed the same marked degree of S-T depression. However, when the count was accurate, he had neither pain nor S-T segment deviation at the reduced exercise level. The possible basis for verbal conditioning provoking angina pectoris is explored.     

Myocardial imaging using thallium 201 scintigraphy after dipyridamole infusion: a case history

Coronary artery disease frequently occurs in combination with peripheral vascular disorders and is an important cause of morbidity and mortality during or after peripheral vascular surgery. However, the detection of coronary artery disease in patients with peripheral vascular disease may be complicated, since most of these patients are unable to perform conventional exercise testing. The authors report a sixty-two-year-old man with an infrarenally located aneurysm of the abdominal aorta who underwent thallium 201 scintigraphy combined with dipyridamole infusion as an alternative exercise test. The subsequent thallium 201 images showed perfusion defects indicative of severe coronary artery disease. Coronary angiography showed an occluded right coronary artery and a significant proximal stenosis in the left anterior descending coronary artery. The patient underwent successful aortocoronary bypass surgery, and two months later, the aortic aneurysm was operated on without complications. As a result, dipyridamole thallium 201 scintigraphy should be considered as a valuable diagnostic test to detect coronary artery disease in patients with peripheral vascular disorders.