Dipyridamole Thallium Imaging Research Articles

Hemodynamic response, arrhythmic risk, and overall safety of Regadenoson as a pharmacologic stress agent for myocardial perfusion imaging in chronic obstructive pulmonary disease and bronchial asthma patients

Regadenoson (REG) is a A2a receptor selective pharmacologic SPECT imaging agent. Its safety in unselected chronic obstructive pulmonary disease (COPD) or asthma (AM) undergoing SPECT imaging has not been well evaluated. We retrospectively identified 228 patients (COPD n = 126 and AM n = 102, Grp 1) undergoing REG SPECT from Jan to Nov 2009 and compared to 1,142 patients without COPD and AM (control, Grp 2). A standard 400 μg REG bolus was used and gated Tc-99 m tetrofosmin SPECT done. Patient demographics, REG SPECT data, side effects, arrhythmia occurrences, and any exacerbation of COPD or AM leading to treatment, hospitalization or death were evaluated. The side effect profile of Grp 1 was also compared to a historical cohort who underwent intravenous dipyridamole thallium-201 imaging and adenosine SPECT. Both groups were comparable with regards to baseline characteristics. There was 0% incidence of clinical exacerbation of COPD or AM after REG. COPD patients had more non-significant arrhythmias (58.3% vs. Grp 2, 43%, P = 0.004). There was 0% incidence of any atrio-ventricular block and only 2 instances of brief supraventricular tachycardia. When compared to the historical cohort of COPD who underwent IV dipyridamole thallium imaging, COPD in Grp 1, had more dyspnea and flushing and when compared to COPD/AM patients who underwent adenosine SPECT, Grp 1 pts had more of flushing and headache (24.9% vs. 2.8%, P = <0.001) but less of bronchospasm (1.3% vs. 6.9%, P = 0.022) and AV block (0% vs. 4.2%, P = 0.014). REG SPECT can be safely performed in COPD and AM population.

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.

Radiopharmaceutical Agents for Myocardial Perfusion Imaging

Myocardial perfusion imaging (MPI) is a well-established noninvasive method of assessing coronary blood flow.1–5 MPI is capable of identifying regional abnormalities in coronary artery blood flow and determining their physiological relevance to myocardial function and viability. MPI requires the intravenous injection of a radioactive blood flow marker followed by imaging of regional myocardial uptake.6–10 Imaging is most frequently performed by tomographic techniques (ie, SPECT [single-photon emission computerized tomography]) with electrocardiographically synchronized image gating. Used frequently in conjunction with either physical exercise or pharmacological stress, MPI is useful in unmasking myocardial perfusion deficits not evident at rest. A thorough discussion of clinical indications for MPI is beyond the scope of this review, but the reader is referred to recently published consensus committee documents.11,12 Three radioactive blood flow markers (RBFMs) are clinically available and in widespread use: (1) thallium Tl 201 chloride, (2) technetium Tc-99m sestamibi (Cardiolite; Lantheus Medical Imaging, North Billerica, Mass), and (3) technetium Tc-99m tetrofosmin (Myoview; GE Healthcare, Princeton, NJ). In the present review, these agents will be referred to by their nonproprietary names. The oldest of the 3 RBFMs, thallium 201, has been in use since approximately 1980, and the original experimental and clinical validation studies of MPI were performed with this agent.1,13–16 More recently, 99mTc-labeled sestamibi, approved in 1990, and tetrofosmin, approved in 1995, have been developed and validated clinically.6–8,17,18 In comparative imaging studies analyzed for accuracy (sensitivity, specificity, and normalcy rates), no obvious differences have been found among these 3 agents. Each RBFM has unique properties that determine the logistics of its use and its test performance characteristics. The purpose of the present review is to compare and contrast these 3 RBFMs. It is hoped this detailed overview will assist clinicians in choosing which agent(s) to use and in understanding …

Direct comparison between pharmacological stress with adenosine triphosphate disodium and exercise stress myocardial perfusion imagings

To clarify the significance of adenosine triphosphate disodium stress myocardial perfusion imaging (ATP-MPI), we directly compared the findings of ATP-MPI with those of exercise stress myocardial perfusion imaging (Ex-MPI). ATP-MPI, Ex-MPI, and coronary angiography (CAG) were performed within 60 days in 17 coronary artery disease patients with mean age of 62.1+/-7.9 years. CAG revealed single-vessel disease (SVD) in 10 patients and multivessel disease (MVD) in seven patients. The summed stress score (SSS) of ATP-MPI was significantly higher than that of Ex-MPI (10.0 [7.8-14.3] vs. 8.0 [4-18], P<0.05). No difference in the SSS was observed between ATP-MPI and Ex-MPI in patients with SVD (8.0 [6.0-9.0] vs. 8.0 [6.0-10.0], NS), whereas this difference was significant in patients with MVD (15.0 [14.0-22.8] vs.9 [7.3-16.3], P<0.05). There was no difference in the summed rest score between ATP-MPI and Ex-MPI. The univariate logistic analysis showed that "MVD" was the significant factor influencing to the overt discrepancy between ATP-MPI and Ex-MPI (odds ratio: 9.0, 95% confidence interval: 1.07-75.84, P=0.043). The accuracy of ATP-MPI and Ex-MPI in detecting the territory of stenotic coronary vessel or previous myocardial infarction was 98.0% and 92.1% (NS), respectively. In conclusion, ATP-MPI is useful for detecting potential ischemic areas that cannot be detected by Ex-MPI, particularly in patients with MVD.

SPECT Dipyridamole scintigraphy for detecting coronary artery disease in patients with isolated severe aortic stenosis

Background: The sensitivity and specificity of non-invasive methods – specifically single-photon emission computed tomography (SPECT) dipyridamole–thallium myocardial perfusion – for detecting coronary artery disease (CAD) in patients with severe aortic stenosis remains unclear. Occasionally, these patients present with atypical angina. Therefore, a CAD diagnosis must be excluded to prevent unnecessary cardiac catheterization. Methods: To determine the diagnostic value of SPECT dipyridamole–thallium imaging in this population, we compared the effectiveness of the imaging procedure with that of coronary angiography by prospectively analyzing patients who underwent both procedures. Group 1 included 59 patients who were asymptomatic or had atypical angina; group 2; 51 preoperative aged-matched patients with typical angina. SPECT acquisition was performed 15 min after 0.142 mg/kg/min of dipyridamole infusion completion, and redistribution images were performed 4 h after thallium injection. Two cut-off values of luminal diameter narrowing, >50 and >70%, defined significant CAD. Results: Coronary angiography with significant CAD (>50%) was present in 15 (25%) group 1 patients and in 16 (32%) group 2 patients (P=NS). The sensitivity was greater in group 2 than in group 1 (56 versus 26%; P=0.001). The specificity, positive and negative predictive value, and accuracy in the groups were similar. CAD of >70% luminal stenosis was present in 11 (19%) group 1 patients and in 12 (23%) group 2 patients (P=NS). The positive predictive value was greater in group 2 than in group 1 (75 versus 43%; P=0.001) but similar sensitivity, specificity, negative predictive value, and accuracy. The likelihood ratio for abnormal test increased in patients with CAD of >70%. Conclusions: symptoms of typical angina had significant impact on test sensitivity, positive predictive value and likelihood ratio for abnormal test. Furthermore, SPECT dipyridamole–thallium imaging was a useful non-invasive method to exclude the diagnosis of significant CAD (high specificity) in asymptomatic and symptomatic patients with isolated severe aortic stenosis.

Con: Preoperative thallium testing should not be performed routinely before vascular surgery

Con: Preoperative thallium testing should not be performed routinely before vascular surgery

Preoperative risk assessment in vascular surgery patients

The patient scheduled for peripheral vascular surgery is an increased anaesthetic challenge, mainly because of coexisting generalized cardiovascular atherosclerotic involvement leading to a high risk of perioperative cardiac complications. In clinical practice it is of importance preoperatively to predict, as accurately as possible, the potential risk of complications so that proper risk-reducing measures can be taken. Relevant clinical data, which have been included by Goldman and Detsky in multifactorial cardiac risk indices, are of potential value for differentiating between patients at low, intermediate, or high risk of perioperative cardiac morbidity and mortality. Patients with low risk scores can be accepted for surgery without further testing, thereby allowing more extensive cardiac testing, such as ambulatory ECG monitoring, exercise stress testing, echocardiography, dipyridamole thallium imaging, or coronary angiography, to be reserved for patients with higher risk scores or overt cardiac problems. The risk stratification is of importance not only for decisions on preoperative prophylactic therapeutic measures (e.g. optimization of medical therapies, coronary artery revascularization), but also for decisions on intraoperative anaesthetic management and postoperative care.

Prediction of human transplantation arteriopathy and coronary events with lung/heart count ratios during intravenous dipyridamole thallium-201 imaging

Background Cardiac allograft arteriopathy often limits long-term survival in transplantation recipients but has been difficult to detect by standard diagnostic methods. Because of the diffuse nature of transplantation coronary disease, we postulated that a lung/heart ratio during dipyridamole thallium imaging might better predict arteriopathy-related complications than diagnostic methods that detect discrete luminal stenoses. Methods and Results Sixty-six unselected heart transplantation recipients were evaluated with annual coronary arteriograms, endomyocardial biopsy, and intravenous dipyridamole thallium testing (initial study group). The mean lung/heart ratio on an anterior planar image was 0.40 for all patients; therefore <0.40 was arbitrarily defined as normal. After October 1992, 98 patients were tested (validation study group) and a lung/heart ratio cutoff of 0.40 was evaluated prospectively. Coronary end points were defined as (1) at least 1 coronary artery stenosis ≥50% of the luminal diameter, (2) sudden cardiac death, and (3) acute myocardial infarction. Stepwise logistic regression analysis was performed to identify independent predictors of future coronary end points. For the initial study group, the lung/heart ratio on the first annual thallium study was the only independent predictor of subsequent cardiac end points (0.47 ± 0.13 [SD] with end points vs 0.38 ± 0.11 without end points, P < .05). For the validation study group, independent predictors of subsequent coronary events included the lung/heart ratio and the radionuclide left ventricular ejection fraction. No patient with a lung/heart ratio <0.40 and a left ventricular ejection fraction ≥0.50 developed a cardiac event during 21 ± 11 months of follow-up. Conclusions A lung/heart ratio ≥0.40 on dipyridamole thallium testing is a sensitive predictor of coronary events after heart transplantation. Patients with heart transplantion who have a lung/heart ratio <0.40 and normal systolic left ventricular function are at low risk for subsequent coronary events and may not require annual surveillance by coronary arteriography. (Am Heart J 1999;137:942-8.)

Physician estimates of perioperative cardiac risk in patients undergoing noncardiac surgery.

We know little about how physicians assess perioperative cardiac risk in patients undergoing noncardiac surgery. To evaluate preoperative medical consultations and determine the extent to which consultants used validated cardiac risk indices and specialized noninvasive cardiac tests, and to assess agreement between physician ratings of cardiac risk (low, moderate, or high) and risk estimates derived using validated cardiac risk indices or, in the case of vascular surgery, a risk index. This observational study was conducted at 5 Canadian teaching hospitals affiliated with 2 universities. We retrospectively evaluated 308 preoperative consultations performed in 297 patients and examined the frequency with which consultants recorded the use of validated cardiac risk indices. We used K statistics to quantify the extent to which physician ratings of cardiac risk agreed with risk estimates derived using validated cardiac risk indices. Physicians recorded use of a risk index in 31% of the consultations, but the index used was almost always the suboptimal classification of the American Society of Anesthesiologists. The agreement between physician estimates of cardiac risk and the validated cardiac risk indices was only fair, with a weighted K of 0.38 (95% confidence interval, 0.28-0.49). Overestimation and underestimation of cardiac risk occurred in 16% and 13% of the consultations, respectively. Consultants did not order dipyridamole thallium imaging or dobutamine stress echocardiography for any moderate-risk patients undergoing vascular surgery. Physicians underuse validated cardiac risk indices, and the agreement between the cardiac risk estimates and risk as determined by validated cardiac indices is suboptimal. Physicians are also underusing dipyridamole thallium imaging and dobutamine stress echocardiography for moderate-risk patients undergoing vascular surgery.

Long-term prognostic value of preoperative dipyridamole thallium imaging and clinical indexes in patients with diabetes mellitus undergoing peripheral vascular surgery

The objective of this study is to assess the prognostic impact of preoperative dipyridamole thallium imaging and clinical variables on the long-term outcome of diabetic patients undergoing peripheral vascular surgery. Complete follow-up was obtained in 101 consecutive patients with diabetes mellitus undergoing routine dipyridamole thallium scintigraphy before vascular surgery (mean 4.2 ± 3.2 years, range 1 month to 11 years). Low risk was defined by diabetes alone with a normal resting electrocardiogram. High risk was defined as a history of angina, myocardial infarction, congestive heart failure, or resting electrocardiogram abnormalities. There were 71 deaths in 98 patients discharged alive from the hospital (median survival 4.4 years). Age, the presence of resting electrocardiogram abnormalities, and an abnormal thallium scan were independent predictors of late death. After adjusting for age >70 years and thallium abnormalities, high-risk patients had a death rate 4.8 times (95% confidence interval 1.7 to 13.4, p <0.002) greater than low-risk patients. The presence of >2 reversible thallium defects was useful in further risk stratification of both low- and high-risk patients. Low-risk patients with >2 reversible defects had a median survival of 4.0 years compared with 9.4 years in those with ≤2 reversible defects (p <0.001). Similarly, high-risk patients with ≤2 reversible defects had an intermediate median survival rate of 4.7 years compared with 1.8 years in the group with >2 reversible defects (p <0.001). Therefore, advanced age and the presence of resting electrocardiographic or thallium abnormalities identifies a subset of diabetic patients with a poor long-term outcome after vascular surgery. Combined clinical and thallium variables may identify a population in whom intensive medical or surgical interventions may be warranted to reduce both perioperative and late cardiac events.

Intravenous dipyridamole thallium imaging V combined arm-leg cycle stress testing of patients unable to exercise on the treadmill.

Rehabilitation patients who will undergo noncardiac surgery or strenuous rehabilitation programs often cannot exercise to greater than 85% of predicted maximal heart rate as required for valid treadmill testing. Because many patients have known or suspected coronary artery disease, greatly increasing their risk for a cardiac event, dipyridamole thallium scans are usually performed, despite a cost of approximately $1400, patient radiation exposure, and the need for a gamma camera. Instead, arm-leg cycle stress testing can be continued to an appropriately high heart rate, is done in the physician's office with an electrocardiograph machine and a blood pressure cuff, and costs $250. This study describes nine patients who had both dipyridamole thallium scans and arm-leg cycle ergometry. Four awaited peripheral vascular surgery, one needed bilateral knee replacements, one was an amputee, and three had claudication. Six had documented and three had suspected coronary disease. In eight of nine patients, the electrocardiograms during both dipyridamole thallium imaging and ergometry were in agreement as to the presence or absence of ischemia (kappa statistic, 0.7273; P = 0.0117). In seven of nine patients, thallium images and ergometry agreed (78% concurrence). To achieve 90% agreement between dipyridamole thallium scans and cycle results, however, 68 patients would have to be studied. In this preliminary study, arm-leg ergometry was feasible in all patients and seemed cost-effective and useful for detecting myocardial ischemia. Clinically, if the ergometry were inconclusive, dipyridamole thallium scans could be performed subsequently to obtain the needed information.

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

To assess the utility of intravenous dipyridamole thallium testing for predicting major cardiac events following acute myocardial infarction in older patients. Prospective cohort study with a median follow-up of 18 months. A university teaching hospital. 73 patients aged 65 years and older with enzymatically confirmed acute myocardial infarction (mean age 75 years, 56% male, 71% white). 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. 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). 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.

The early prediction by dipyridamole thallium-201 imaging of late restenosis after PTCA: Is it an accurate approach?

The early prediction by dipyridamole thallium-201 imaging of late restenosis after PTCA: Is it an accurate approach?

Noninvasive diagnosis of gastroesophageal inflammation using dipyridamole thallium-201 tomography

Objective: Esophagitis, a complication of GERD, and gastric erosions are common findings in dyspeptic patients. Unfortunately, these findings cannot be predicted based on symptoms alone and require endoscopy for an accurate diagnosis. Noninvasive diagnosis of other gastrointestinal pathology by radiopharmaceuticals (GA 67, Tc 99m pertechnetate) has previously been studied. We hypothesized that endoscopically documented esophagitis and/or gastric erosions could also be detected by using dipyridamole thallium-201 imaging and, if they were of sufficient accuracy, could serve as a useful, noninvasive screening test for esophagitis and/or gastric erosions. Methods: A pilot study was undertaken in 12 patients undergoing endoscopy for symptoms of GERD or dyspepsia. Esophagitis was defined as the presence of either erosions or ulceration and gastric erosions were defined as discrete mucosal breaks measuring ≥1 mm. Dipyridamole thallium-201 imaging was performed the following day on all 12 patients. A standard dose of dipyridamole (0.56 mg/kg) was infused over 4 min, followed by a 3-mCi dose of thallium-201. Initial stress tomographic images and reinjection (1 mCi) resting tomographic images 3–4 h later were obtained using a gamma camera. Tomographic images were read blinded to the endoscopy results. Thallium-201 uptake was graded on a 0–3+ scale using the liver uptake as the internal comparative standard (2+ = uptake equal to the liver). Abnormal thallium uptake was defined as ≥2+ in the area of the esophagus or stomach. Results: Seven women and five men (mean age 41 yr, range 25–60 yr) were studied. Eight patients were taking histamine-2 receptor antagonists and none were on proton pump inhibitors, or promotility agents. All five patients with endoscopic esophagitis had a positive thallium-201 tomographic image. Seven patients had no evidence of esophagitis, and three had positive thallium-201 tomograms. Dipyridamole thallium-201 imaging sensitivity, specificity, and positive and negative predictive values for esophagitis were 100%, 57%, 63%, and 100%, respectively. All three patients with gastric erosions had positive thallium-201 tomograms. Six of nine patients without gastric erosions had positive tomograms. The sensitivity, specificity, and positive and negative predictive values of DT 201 gastric erosions were 100%, 33%, 33%, and 100%, respectively. Conclusions: Dipyridamole thallium-201 tomographic imaging has good sensitivity (100%) in detecting esophagogastric mucosal erosions, but its poor specificity (33–57%) results in an unacceptable accuracy as a screening test. Additionally, the cost of radiopharmaceuticals requires that sensitivity and specificity be at least equal to that of endoscopy for this test to be clinically valuable as a screening test. However, a noninvasive test for these diseases is inherently appealing, and further research in this area seems to be warranted.

Noninvasive diagnosis of gastroesophageal inflammation using dipyridamole thallium-201 tomography.

Esophagitis, a complication of GERD, and gastric erosions are common findings in dyspeptic patients. Unfortunately, these findings cannot be predicted based on symptoms alone and require endoscopy for an accurate diagnosis. Noninvasive diagnosis of other gastrointestinal pathology by radiopharmaceuticals (GA 67, Tc 99m pertechnetate) has previously been studied. We hypothesized that endoscopically documented esophagitis and/or gastric erosions could also be detected by using dipyridamole thallium-201 imaging and, if they were of sufficient accuracy, could serve as a useful, noninvasive screening test for esophagitis and/or gastric erosions. A pilot study was undertaken in 12 patients undergoing endoscopy for symptoms of GERD or dyspepsia. Esophagitis was defined as the presence of either erosions or ulceration and gastric erosions were defined as discrete mucosal breaks measuring > or = 1 mm. Dipyridamole thallium-201 imaging was performed the following day on all 12 patients. A standard dose of dipyridamole (0.56 mg/kg) was infused over 4 min, followed by a 3-mCi dose of thallium-201. Initial stress tomographic images and reinjection (1 mCi) resting tomographic images 3-4 h later were obtained using a gamma camera. Tomographic images were read blinded to the endoscopy results. Thallium-201 uptake was graded on a 0-3+ scale using the liver uptake as the internal comparative standard (2+ = uptake equal to the liver). Abnormal thallium uptake was defined as > or = 2+ in the area of the esophagus or stomach. Seven women and five men (mean age 41 yr, range 25-60 yr) were studied. Eight patients were taking histamine-2 receptor antagonists and none were on proton pump inhibitors, or promotility agents. All five patients with endoscopic esophagitis had a positive thallium-201 tomographic image. Seven patients had no evidence of esophagitis, and three had positive thallium-201 tomograms. Dipyridamole thallium-201 imaging sensitivity, specificity, and positive and negative predictive values for esophagitis were 100%, 57%, 63%, and 100%, respectively. All three patients with gastric erosions had positive thallium-201 tomograms. Six of nine patients without gastric erosions had positive tomograms. The sensitivity, specificity, and positive and negative predictive values of DT 201 gastric erosions were 100%, 33%, 33%, and 100%, respectively. Dipyridamole thallium-201 tomographic imaging has good sensitivity (100%) in detecting esophagogastric mucosal erosions, but its poor specificity (33-57%) results in an unacceptable accuracy as a screening test. Additionally, the cost of radiopharmaceuticals requires that sensitivity and specificity be at least equal to that of endoscopy for this test to be clinically valuable as a screening test. However, a noninvasive test for these diseases is inherently appealing, and further research in this area seems to be warranted.

The safety of dipyridamole-thallium imaging in patients with critical aortic valve stenosis and angina.

Angina pectoris occurs in many patients with critical aortic valve stenosis, but in less than 50% of cases is it due to atherosclerotic coronary disease. Pre-operative coronary angiography is used to determine whether coronary revascularization is required in addition to aortic valve replacement. The aim of this study was to determine the safety and image quality of dipyridamole-thallium imaging (DPT) in excluding coronary artery disease requiring a coronary artery bypass graft in patients with aortic valve stenosis requiring aortic valve replacement. Dipyridamole-thallium imaging and coronary angiography were performed less than one month apart in patients with clinical and echo-Doppler evidence of aortic valve stenosis requiring aortic valve replacement. Coronary angiography and DPT were each interpreted by experienced observers blind to the other result. The safety of DPT was judged by symptoms, ECG changes, haemodynamic effects and the need for stress reversal. Image quality was determined from the myocardial-to-background thallium uptake ratio in a normal segment. Twelve patients with aortic valve stenosis (gradient 95 +/- 24 mmHg) were studied, all of whom had left ventricular hypertrophy. The dominant symptom was angina pectoris in eight patients, syncope in three and dyspnoea in one. None had previous myocardial infarction, but two were smokers, six were hyperlipidaemic and one was hypertensive. The patients tolerated DPT well and only one required stress reversal. The quality of the DPT images was good. The DPT image was entirely normal in eight (66%) patients, none of whom had coronary artery disease. Reversible defects were seen in four patients, all of whom had significant coronary artery disease. We conclude that DPT is safe in patients with aortic valve stenosis and angina pectoris. The image quality is good despite left ventricular hypertrophy. In patients with angina pectoris and aortic valve stenosis, coronary angiography can safely be restricted to those with abnormal myocardial perfusion results.

Patients with stable chronic obstructive pulmonary disease can safely undergo intravenous dipyridamole thallium-201 imaging

Background Patients with chronic obstructive pulmonary disease are usually excluded from intravenous dipyridamole thallium-201 testing. We developed a nurse-administered protocol to screen and pretreat patients so they could be safely tested.Methods and Results We prospectively screened patients referred for intravenous dipyridamole thallium testing and retrospectively reviewed a comparison group of patients who had undergone intravenous dipyridamole testing before our bronchospasm protocol. We studied 492 consecutive patients referred for intravenous dipyridamole thallium testing, separating those with complete data (n = 451) into two groups: group A (n = 72), patients assessed to be at risk for intravenous dipyridamole-induced bronchospasm who received our bronchospasm treatment protocol; and group B (n = 379), patients assessed to be free of risk, who did not receive our bronchospasm protocol. Group C (n = 89) was a retrospective comparison group of patients who had undergone intravenous dipyridamole testing before initiation of the protocol. Patients were considered at risk for an adverse event if any of the following were present: peak flow ≤400 ml at the time of the test (spirometry by nurse) that increased to >400 ml after bronchodilator treatment, wheezing audible with stethoscope, history of chronic obstructive pulmonary disease or asthma or dyspnea on exertion at less than four blocks, or resting respiratory rate >18 breaths/min. The test was considered contraindicated if resting oxygen saturation was <85%, respiratory rate ≥36 breaths/min, or peak flow measured by peak flowmeter <400 ml after bronchodilator inhalant (albuterol or metaproterenol sulfate by spacer) at a dose of up to six puffs. One minute after injections of thallium-201, patients at risk were given 50 mg aminophylline by slow intravenous injection. We looked for major and minor adverse effects and divided them into three categories: (1) minor events (transient headache, abdominal discomfort, or nausea), wheezing (audible by stethoscope but without marked respiratory distress), (2) marked events (severe bronchospasm or severe ischemia defined as wheezing audible with or without stethoscope, respiratory rate >20 breaths/min or increased by 10 from pretest evaluation, oxygen desaturation to <90%, hypoventilation [reduced respiratory rate with decreased mental status], respiratory arrest, chest pain, horizontal ST-segment depression ≥1 mm on the electrocardiogram in any lead, symptomatic hypotension), or (3) other intravenous dipyridamole-induced side effects (persistent headache, dizziness, flushing, nausea, dyspnea, and ischemic chest pain) or anginal equivalent. The protocol properly identified patients with impaired pulmonary function. There was no difference in the frequency of adverse marked events among groups A, B, or C (1% vs 4% vs 2%, p = 0.25). Patients in group A had more minor side effects than those in group B (53% vs 35%, p = 0.004). Specifically, patients in group A were more likely to wheeze (39% vs 1%, p = <0.001), but wheezing in group A was self-limited or responded to treatment as described in the protocol. The prevalence of positive thallium-201 scans in group A (44%) compared with group C (49%) was not different (p = 0.15).Conclusions A nurse-administered risk assessment and pretreatment protocol (1) properly identified patients with impaired pulmonary function, (2) permitted completion of intravenous dipyridamole testing in patients at risk for bronchospasm without an increased incidence of marked adverse events, and (3) did not appear to influence the interpretation of the thallium test. (Am Heart J 1998;136:307-13.)

Current practice in the pre-operative assessment of patients for elective repair of abdominal aortic aneurysm. A survey of UK hospitals.

A postal survey of 100 hospitals throughout the United Kingdom and Ireland was conducted to assess current practice in the pre-operative assessment and use of pulmonary artery catheters in patients undergoing elective abdominal aortic aneurysm repair. Seventy-four completed questionnaires were received. The survey revealed that 53% of respondents hold designated preoperative assessment clinics, attended by anaesthetists in 54% and cardiologists in 26%. However, only 4% of respondents have a written protocol for stratifying patients and assessing peri-operative risk. By far the commonest investigation of choice for further cardiological assessment is transthoracic echocardiography (67%). Other investigations of choice are multiple update gated acquisition (MUGA) scan (13%), dipyridamole thallium imaging (9%), exercise ECG (6%), stress echocardiography (1%) and stress MUGA (1%). Two units (3%) never undertook further investigation. Pulmonary artery flotation catheters are used as a routine by 9% of respondents, dependent upon left ventricular ejection fraction by 65%, dependent on other factors by 7% and not used at all by 19%. The survey reveals widespread variation in pre-operative assessment of patients undergoing elective repair of abdominal aortic aneurysm.

PREOPERATIVE ASSESSMENT OF COMMON DISEASES IN THE OUTPATIENT SETTING

Perioperative myocardial infarction (MI) is a major source of morbidity and mortality in surgical patients. Each year an estimated 50,000 patients in the United States experience perioperative and mortality exceeds 20,000 annually.44 The average cost to hospitals is estimated in one source to be $12,000 per ~atient.4~ The risk of perioperative MI is greatly increased in patients with previous infarction within 6 months of 69 and elective outpatient surgery should be postponed in such patients. In patients with previous MI for whom surgery cannot be postponed an appropriate number of weeks, or in patients without prior MI who have coronary artery disease (CAD) or stable angina, the use of preoperative testing can identify which patients are at increased risk of perioperative cardiac ischemia. For patients with recent MI in whom surgery is not completely elective but not truly emergent (e.g., a patient with a resectable malignancy) evaluation of left ventricular function and exercise tolerance may identify patients with relatively small risks. The nature of the surgery to be undertaken has considerable influence over the risks of surgery in patients with CAD. Backer et a1 found that ophthalmologic surgery under local anesthesia was safe, even in patients with recent ML4 The number of patients in the study who underwent ophthalmologic surgery under general anesthesia was small, but they also did well. Transurethral resection of the prostate appears to carry low risk, even in patients with serious heart disease,-*' and many authors suggest that the risks of peripheral extremity procedures is also l0w.7~ Vascular surgery is associated with increased risk.60 The identification of patients with preoperative myocardial ischemia is an important step in identifying patients at increased anesthetic and surgical risk. Slogoff and Keatsm demonstrated that perioperative myocardial ischemia is associated with perioperative MI. Preoperative testing that defines patients at

Prediction of late cardiac events by dipyridamole thallium scintigraphy in patients with intermittent claudication and occult coronary artery disease

Concomitant coronary artery disease often occurs in patients with peripheral vascular disease, but it may be asymptomatic. Despite being asymptomatic, cardiovascular events are the main source of morbidity and mortality in this group of patients. Dipyridamole thallium scintigraphy has been shown to be of prognostic value in patients with peripheral vascular disease and symptomatic coronary artery disease, but its effect on the long-term outcome in the asymptomatic group of patients is less defined. Eighty-four consecutive patients with peripheral vascular disease and no symptoms of coronary artery disease were therefore evaluated by clinical assessment, dipyridamole thallium imaging, radionuclide ventriculography, and cardiac catheterization and followed for a mean of 66 months. Abnormal perfusion patterns were found on thallium scintigraphy in 48 patients (57%); fixed, mixed, and reversible defects were present in 14 (17%), 11 (13%), and 23 (27%) patients, respectively. Significant coronary artery disease was present in 52 patients (69%) and mean left ventricular ejection fraction was 44%. During the followup period, 23 patients had a cardiac event (nonfatal myocardial infarction or cardiac death). Univariate analysis of 15 clinical, scintigraphic, radionuclide, and angiographic variables revealed that age, angiographic extent of coronary artery disease, and an abnormal thallium scan were significant predictors of subsequent cardiac events. Multivariate stepwise logistic regression analyses selected fixed and mixed thallium defects and diffuse coronary artery disease as the only significant independent predictors of outcome. Thus, the present study shows the value of dipyridamole thallium scintigraphy as a valuable prognostic indicator for long-term event-free survival in a cohort of patients with peripheral vascular disease and no history or symptoms of coronary artery disease.