Dipyridamole Thallium Imaging Research Articles

Extent of jeopardized viable myocardium determined by myocardial perfusion imaging best predicts perioperative cardiac events in patients undergoing noncardiac surgery

Objectives. This study was undertaken to test the hypothesis that the risk of perioperative cardiac events is not simply determined by the presence of myocardium at risk, but is directly related to the extent of myocardium at risk as reflected in thallium-201 myocardial imaging.Background. The risk of perioperative cardiac events in patients undergoing noncardiac surgery has been related to the presence of transient defects on dipyridamole thallium-201 myocardial imaging, reflecting jeopardized viable myocardium.Methods. The study cohort consisted of 231 consecutive patients who underwent noncardiac surgery and had a preoperative dipyridamole thallium-201 imaging study. Patients with vascular reconstruction or bypass constituted the largest surgical subgroup (n = 140). For thallium-201 imaging data, each of three planar projections was divided into three segments (total nine segments) and each segment was interpreted as normal or showing a transient or fixed defect. The ability of clinical and thallium-201 imaging data to predict perioperative cardiac events was compared with stepwise multivariate logistic regression analysis.Results. Perioperative cardiac events occurred in 19 patients, including 5 with cardiac death, 7 with nonfatal myocardial infarction and 7 with unstable angina. For cardiac death or nonfatal myocardial infarction, the only significant multivariate predictors were the number of myocardial segments with transient thallium·201 defects (p < 0.0005) and a history of diabetes mellitus (p < 0.05). For all cardiac events, the only significant multivariate predictors were the number of myocardial segments with transient defects (p < 0.0001), diabetes mellitus (p < 0.05) and calcium channel blocker use (p < 0.05).Conclusions. The probability of important cardiac events in patients undergoing noncardiac surgery is best predicted by the extent of myocardium at risk as reflected on thallium·201 myocardial perfusion imaging. A history of diabetes mellitus also has a significant influence on perioperative risk.

Prognostic value of noninvasive cardiac tests in the assessment of patients with peripheral vascular disease

Two hundred thirty-six patients with peripheral vascular disease were prospectively studied to assess whether noninvasive cardiac investigations could predict prognosis better than simple clinical assessment. Clinical history, examination and resting electrocardiography were considered in all patients; exercise electrocardiography, Holter monitoring, radionuclide ventriculography and dipyridamole thallium imaging were performed in a subgroup of 168 patients. Follow-up for 6 to 30 months revealed major cardiac events in 21 patients. Cox survival analysis showed that clinical evidence of prior coronary artery disease was the best variable from clinical assessment that predicted cardiac events, with no other clinical variable adding to the statistical model. When variables from noninvasive cardiac assessment were added to the model, which included clinical evidence of coronary artery disease, dipyridamole thallium heart:lung ratio and left ventricular ejection fraction added significantly and incrementally to the prediction of cardiac events. Results of exercise electrocardiography or Holter monitoring did not add significantly. It is concluded that high lung uptake of thallium during dipyridamole stress, and impaired left ventricular ejection fraction help to identify patients with peripheral vascular disease who are at high cardiac risk, and should therefore be used for selecting subsequent cardiovascular medical, surgical and anesthetic management.

Dipyridamole thallium-201 scintigraphy for improved detection of left anterior descending coronary artery stenosis in patients with left bundle branch block.

In patients with left bundle branch block (LBBB) undergoing thallium-201 exercise scintigraphy septal perfusion defects are frequently observed irrespective of the presence or absence of coronary artery disease. Consequently, in these patients the specificity for detecting stenoses in the left anterior descending coronary artery (LAD) by thallium-201 scintigraphy is relatively low. It has been hypothesized that pharmacological vasodilation would result in higher specificity than conventional exercise thallium-201 scintigraphy because of a more uniform exploitation of coronary flow reserve. Twenty-five consecutive patients with LBBB underwent dipyridamole thallium-201 imaging and coronary arteriography within 3 months. The prevalence of coronary artery disease was estimated at 48 +/- 19%. Sensitivity for detection of LAD lesions was 100% and specificity was 88%. The positive predictive accuracy and the negative predictive accuracy were 80% and 100% respectively. The 'false positive' septal defects were of the non-reversible type. The appearance of septal perfusion defects was not dependent on changes in heart rate during dipyridamole infusion. This study indicates the value of dipyridamole thallium-201 imaging for non-invasive detection of LAD stenosis in patients with LBBB.

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). Therefore, dipyridamole thallium imaging demonstrates valuable prognostic information for long-term event-free survival in a large population of patients undergoing vascular surgery and provides important risk stratification data for the perioperative period.

Comparison of accuracy for detecting coronary artery disease and side-effect profile of dipyridamole thallium-201 myocardial perfusion imaging in women versus men

Intravenous dipyridamole planar thallium-201 imaging is a safe and effective test for detection and prognosis of coronary artery disease (CAD) in the general population. The relative diagnostic accuracy and side-effect profile of dipyridamole thallium-201 stress imaging in women is not defined. Forty-three consecutive female and 71 male patients who underwent dipyridamole thallium-201 imaging (0.56 mg/kg) within 3 months of cardiac catheterization were studied. Scans were considered abnormal if fixed or reversible perfusion defects were detected. Stenosis severity of ≥50% luminal diameter reduction of any artery defined CAD. Overall sensitivity for detection of CAD was 0.87 in women and 0.94 in men; specificity was 0.58 in women and 0.63 in men (p = not significant). Sensitivity for detection of 1-vessel CAD was 0.60 in women and 0.94 in men (p = 0.001). The sensitivity for detection of muttivessel CAD (with or without surgical revascularization) was 1.0 and 0.94 in women and men, respectively. Adverse effects were reported in 62% of women and in 38% of men (p = 0.01). There was no significant difference in the incidences of chest pain, headache, nausea, flushing or electrocardiographic changes. The incidences of severe ischemia and dizziness were higher in women. Possible explanations for this difference in adverse effects include gender differences in the volume of distribution of dipyridamole due to varied fat-to-muscle ratios and different subjective nocioceptive sensitivities to the effects of dipyridamole. Overall sensitivity and specificity are comparable between the sexes.

Prognostic value of dipyridamole thallium-201 imaging in elderly patients

The prognostic value of intravenous dipyridamole myocardial perfusion imaging has not been studied in a large series of elderly patients. Patients ≥70 years of age with known or suspected coronary artery disease were evaluated to determine the predictive value of intravenous dipyridamole thallium-201 imaging for subsequent cardiac death or nonfatal myocardial infarction. Of the 348 patients, 207 were symptomatic and 141 were asymptomatic; 52% of the asymptomatic group had documented coronary artery disease. During 23 ± 15 months of follow-up, there were 52 cardiac deaths, 24 nonfatal myocardial infarctions and 42 revascularization procedures (percutaneous transluminal coronary angioplasty in 20; coronary artery bypass surgery in 22). Clinical univariate predictors of a cardiac event included previous myocardial infarction, congestive heart failure symptoms, hypercholesterolemia and diabetes (all p < 0.05).The presence of a fixed, reversible or combined thallium-201 defect was significantly associated with the occurrence of cardiac death or myocardial infarction during follow-up (p < 0.05). Cardiac death or nonfatal myocardial infarction occurred in only 7 (5%) of 150 patients with a normal dipyridamole thallium-201 study (p < 0.001). Stepwise logistic regression analysis of clinical and radionuclide variables revealed that an abnormal (reversible or fixed) dipyridamole thallium-201 study was the single best predictor of cardiac events (relative risk 7.2, p < 0.001). As has been demonstrated in younger patients, previous myocardial infarction (relative risk 1.8, p < 0.001) and symptoms of congestive heart failure at presentation (relative risk 1.6, p = 0.02) were also significant independent clinical predictors of cardiac death or myocardial infarction.Dipyridamole thallium-201 myocardial imaging is a powerful independent noninvasive technique for prognostication in the elderly, a group with limited exercise capacity, the potential for advanced coronary artery disease and a high risk for cardiac events.

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 dipyridamolethallium 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 >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. With step 1 (low risk) 63% (225 of 355) of the patients have been classified, whereas with step 2 (high risk), 50% (15 of 30) of the complications could have been avoided.

Multivariate clinical models and quantitative dipyridamole thallium imaging to predict cardiac morbidity and death after vascular reconstruction : Lette J, Waters D, Lassonde J, et al: J Vasc Surg 14:160–169, 1991

Multivariate clinical models and quantitative dipyridamole thallium imaging to predict cardiac morbidity and death after vascular reconstruction : Lette J, Waters D, Lassonde J, et al: J Vasc Surg 14:160–169, 1991

Value of dipyridamole thallium-201 imaging in noninvasive differentiation of idiopathic dilated cardiomyopathy from coronary artery disease with left ventricular dysfunction

The purpose of this study was to noninvasively differentiate in patients with reduced global left ventricular function between those with idiopathic dilated cardiomyopathy (IDC) and coronary artery disease (CAD). Clinical features and findings of dipyridamole thallium-201 imaging in 55 consecutive patients with IDC were compared with those in 77 with CAD. Left ventricular ejection fraction was similar between the 2 groups (34 ± 16% vs 39 ± 7%). Patients with IDC had lower incidences of ischemic chest pain (11 vs 79%; p < 0.0001), electrocardiographs evidence of myocardial infarction (24 vs 82%; p < 0.0001), and reversible defects (4 vs 57%; p < 0.0001) than did those with CAD. The lowest percent thallium uptake in the initial imaging was less with CAD than IDC (30 ±15% vs 59 ± 10%; p < 0.001). Patterns of perfusion defects were classified as: no defects, multiple small defects and large defects. Of patients with IDC, 15 had no defects, 19 had multiple small defects, and 21 had large defects, whereas all those with CAD had large defects (p < 0.0001). Stepwise discriminant analysis, using chest pain and electrocardiography, revealed sensitivity of 89%, specificity of 87%, accuracy of 88%, and positive predictive value of 83% in the identification of patients with IDC. After including the findings of dipyridamole thallium imaging, analysis revealed that the combination of the lowest percent thallium uptake in the initial imaging, the chest pain, reversible defects, blood pressure at rest, pattern of perfusion defects and electrocardiography best identified (p < 0.0001) patients with IDC (sensitivity 95%, specificity 96%, accuracy 95% and positive predictive value 95%). These results indicate that the addition of dipyridamole thallium-201 imaging data to known clinical and electrocardiographic variables can help differentiate patients with cardiac dysfunction between IDC and CAD with a high degree of certainty.

ST-segment depression during dipyridamole infusion, and its clinical, scintigraphic and hemodynamic correlates

The goal of this study was to determine whether dipyridamole-induced ST-segment depression reflects more severe or extensive myocardial hypoperfusion than the absence of this electrocardiographic finding. The clinical, hemodynamic and scintigraphic correlates of ST-segment depression during intravenous dipyridamole infusion were studied in 204 consecutive patients undergoing dipyridamole stress thallium-201 (Tl-201) imaging for evaluation of coronary artery disease. Of 182 patients with a diagnostic baseline electrocardiogram, 28 (15%) developed ST depression after dipyridamole. Patients with ST depression, compared with those without, were older (64 ± 1 vs 60 ± 1 years; p < 0.03) and had a higher frequency of chest pain (57 vs 23%; p < 0.001) and a higher heart rate-blood pressure product (12.7 ± 0.6 vs 11.2 ± 0.2 × 10 3; p < 0.008) after dipyridamole. Patients with ST depression were more likely to have Tl-201 redistribution (64 vs 38%; p < 0.02) and a greater number of redistribution defects (2.3 ± 0.04 vs 0.9 ± 0.1, p < 0.001) than were those without ST depression. By multivariate logistic regression analysis, the most powerful correlate of ST depression was the number of segments having Tl-201 redistribution (p < 0.001). Other independent correlates were presence of chest pain, heart rate at Tl-201 injection, and age. Thus, the determinants of dipyridamole-induced ST-segment depression include the scintigraphic extent of reversible hypoperfusion, as well as indexes of myocardial oxygen demand.

Failure of negative dipyridamole thallium scans to predict perioperative myocardial ischaemia and infarction

Three cases of postoperative myocardial infarction are reported in patients with normal or fixed defects on preoperative dipyridamole thallium scans (interpreted as "negative" for active cardiac ischaemic risk). All patients were monitored with an ambulatory electrocardiographic recorder from the evening before surgery through the first two postoperative days. Two of the patients demonstrated preoperative or early postoperative ischaemia, suggesting that the test was a false negative. The third patient did not demonstrate ischaemia during the period of monitoring, but developed a myocardial infarction during the third postoperative day, suggesting progression of the underlying coronary artery disease. Preoperative dipyridamole thallium imaging may result in false negative scans in selected high-risk populations.

Hibernating Myocardium Associated with Coronary Artery Dissection and Vasospastic Angina.

Hibernating myocardium is an uncommon clinical state involving persistently impaired myocardial function. A 61-year-old man was admitted because of vasospastic angina. Coronary angiography revealed coronary artery dissection in the midportion of the right coronary artery, and segmental vasoconstriction was evoked by acetylcholine. In this patient, hibernating myocardium in the dissected region was clearly demonstrated by dipyridamole thallium-201 imaging. This report describes the first documented case of hibernating myocardium associated with coronary artery dissection, and the usefulness of dipyridamole thallium-201 imaging in the assessment of this state. Coronary artery spasm might be relevant to the etiology of coronary artery dissection.

Role of dipyridamole thallium-201 imaging in left bundle branch block

Exercise thallium-201 imaging is of limited diagnostic accuracy in patients with left bundle branch block (LBBB), because decreased septal activity often occurs in the absence of left anterior descending artery disease. 1–3 A combination of tachycardia, shortened diastolic relaxation time and asynchronous contraction are considered to be responsible for this phenomenon. 1,2 Recently, it has been suggested that dipyridamole thallium-201 scintigraphy significantly improves specificity in patients with LBBB by assessing coronary flow reserve at lower heart rates. 4 Relatively few patients in the latter report, however, had angiographic correlation. Accordingly, this study compares this technique with angiographic findings in a larger group of patients with LBBB at rest.

Preoperative Evaluation of Patients with Peripheral Vascular Disease

Coronary artery disease is the leading cause of death after revascularization procedures for abdominal aortic aneurysms and peripheral vascular disease. Late survival after vascular procedures is substantially reduced, largely by the high incidence of subsequent cardiac events. At the Lahey Clinic, it is not our practice to perform routine coronary angiography before elective revascularization. Thallium myocardial perfusion imaging should be performed in all patients before operation. Abnormal results on thallium exercise scanning showing multiple perfusion abnormalities or lung uptake at peak exercise identify patients who are candidates for preoperative cardiac catheterization. When severe correctable coronary artery disease is identified, these patients should be considered for coronary artery bypass surgery before vascular operation.

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.

High-Risk Cardiac Patient: Focus on Vascular Surgery

Summary The ideal screening test for the detection of patients at increased risk for cardiac morbidity during vascular operations has not yet been developed. Nevertheless, a broad spectrum of preoperative tests are available and include resting, ambulatory, and exercise ECG monitoring, radionuclide angiography, dipyridamole thallium-201 myocardial imaging, and coronary angiography. Any of these tests may be indicated in the asymptomatic patient, depending on the analysis of individual cardiac-risk factors. At present, we perform resting ECG and dipyridamole thallium-201 imaging in most of our patients who undergo vascular operation. Coronary angiography is performed in selected patients in whom evidence of significant myocardial ischemia is found on these or other comparable tests. Preoperative pharmacologic therapy is directed toward the treatment of potential causes of myocardial ischemia, such as tachycardia and hypertension. In addition, pharmacologic interventions to reverse intraoperative and postoperative myocardial ischemia are equally important. In this regard, constant surveillance for myocardial ischemia in patients undergoing vascular operation is recommended because the presence of some CAD in these patients is the rule rather than the exception.

Dipyridamole thallium imaging

Dipyridamole cardiac imaging is a useful alternative to exercise stress testing in the evaluation of patients with ischemic heart disease. Intravenous dipyridamole has been approved recently for clinical use. Oral dipyridamole is widely available. The hemodynamic effects of dipyridamole include an increase in coronary blood flow in excess of the increase in myocardial oxygen consumption and cardiac output. The quality of the thallium images is better or similar to that of exercise thallium images. The optimal dose of intravenous dipyridamole is 0.56 mg/kg and the optimal oral dose is 300-375 mg, although higher doses may be necessary in some patients. The sensitivity and specificity of dipyridamole-thallium imaging, whether intravenous or oral, have been shown in a number of studies to be quite adequate and comparable to that achieved during exercise thallium imaging. Dipyridamole-thallium imaging has also been useful in identifying high-risk patients undergoing major elective vascular surgery. The relative merits of dipyridamole imaging versus exercise testing after acute myocardial infarction require further studies.

Dilatation of the left ventricular cavity on dipyridamole thallium-201 imaging: A new marker of triple-vessel disease

To investigate the significance and mechanism of dilatation of the left ventricular cavity on dipyridamole thallium-201 imaging, we performed both dipyridamole thallium-201 imaging and dipyridamole radionuclide anglography on 83 patients with known angiograms. The dipyridamole/delayed ratio of the left ventricular dimension from the thallium-201 image was defined as the left ventricular dilatation ratio (LVDR). An LVDR greater than the mean + two standard deviations in patients without coronary artery disease was defined as abnormal. Twenty-two of 83 patients showed an abnormal LVDR, and 18 of the 22 patients (82%) had triple-vessel disease. By defect and washout analysis, the sensitivity and specificity for correctly identifying the patients as having triple-vessel disease was 72% and 76%, respectively, whereas LVDR had a sensitivity of 72% and a specificity of 93%. When LVDR was used in combination with the defect and washout criteria, sensitivity increased to 84% without a loss of specificity. In those 22 patients with abnormal LVDRs, end-diastolic volume measured by radionuclide angiography did not change after dipyridamole infusion. Dilatation of the left ventricular cavity on dipyridamole thallium-201 imaging reflected relative subendocardial hypoperfusion induced by dipyridamole rather than actual chamber enlargement. The LVDR was moderately sensitive and highly specific for triple-vessel disease and provided complementary information to dipyridamole thallium-201 imaging.

Dipyridamole thallium imaging for prognosis in elderly patients

Dipyridamole thallium imaging for prognosis in elderly patients

Noninvasive Screening for Silent Ischemic Heart Disease in Patients with Cerebral Ischemia: Use of Dipyridamole-Thallium Myocardial Imaging

To evaluate the incidence of silent ischemic heart disease in cerebrovascular patients unable to exercise, we performed intravenous dipyridamole-thallium myocardial imaging in 38 consecutive patients with stroke without angina or previous myocardial infarction. Dipyridamole was injected intravenously at the dosage of 0.56 mg/kg over 4 min, followed by 4 min of handgrip exercise. Of the 38 patients, 35 had severe atherosclerotic lesions of the internal carotid artery and 3 occlusion of the middle cerebral artery. Dipyridamole-thallium myocardial imaging was normal in 15 patients and abnormal in 23 (60%): reversible perfusion defects were detected in 21 cases and fixed defects in 2. Minor side-effects were observed in 5 patients; no neurologic complications occurred. In conclusion, our findings suggest that in a large proportion of patients with severe large-artery occlusive cerebrovascular disease, a silent ischemic heart disease is present. Dipyridamole-thallium myocardial imaging can be proposed as a safe and valuable examination in the noninvasive cardiac screening of those cerebrovascular patients unable to exercise.