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PubMed1984

Serial thallium-201 imaging after dipyridamole for coronary disease detection: quantitative analysis using myocardial clearance.

After dipyridamole, canine studies have demonstrated a slower rate of myocardial thallium-201 clearance from zones distal to a coronary artery stenosis compared to normal zones. To determine if criteria based on canine myocardial thallium-201 clearance rates could be applied clinically, 40 patients with and 26 patients without coronary artery disease (CAD) had serial thallium-201 images obtained for 2 to 5 hours after dipyridamole. Regions of interest were manually placed over six left ventricular segments in two projections for each of three imaging times. The myocardial thallium-201 clearance rate was calculated for each of the six segments and, using the clearance rate criterion found in canine studies, was considered abnormal if less than 6.5%/hr. Using this criterion alone, 22 of 26 patients (85%) without CAD had normal and 30 of 40 patients (75%) with CAD had abnormal myocardial thallium-201 clearance rates. A quantitative analysis of regional inhomogeneity in tracer distribution (normal was greater than or equal to 25% difference between segments) was negative in 24 of 26 patients (92%) without CAD and positive in 20 of 40 patients (50%) with CAD. When both clearance rate and regional inhomogeneity were considered, 21 of 26 patients (81%) without CAD had negative and 36 of 40 patients (90%) with CAD had positive results. Thus, post-dipyridamole myocardial clearance rate criteria derived from canine studies can be applied to clinical thallium imaging. Quantitative analysis of serial thallium-201 images after dipyridamole is optimized by using myocardial thallium-201 clearance rates. Such an approach is independent of regional inhomogeneities in tracer distribution.

Adult↗
PubMed1988

Cardiac imaging and myocardial kinetics of technetium-tertiary butyl-isonitrile during dipyridamole-induced hyperemia.

UNLABELLED: To determine the myocardial kinetics of technetium-tertiary-butyl-isonitrile (Tc-TBI) during dipyridamole-induced hyperemia, the circumflex coronary arteries (LCX) of 15 dogs were partially occluded. Dipyridamole was then infused intravenously over 4 minutes, creating hyperemic flows in the anterior descending (LAD) coronary system. Tc-TBI was administered, then LAD and LCX regional myocardial Tc-TBI activities were continuously monitored with miniature detectors and gamma camera imaging over 3 hours. Microsphere-determined regional myocardial blood flows demonstrated an LCX/LAD flow ratio of 0.81 +/- 0.21 at rest and 0.45 +/- 0.24 (SD) during dipyridamole infusion. Three-hour fractional Tc-TBI clearance rates were minimal and were equal in the LAD (0.14 +/- 0.11) and LCX (0.13 +/- 0.12) zones (p = ns). Excellent gamma camera images, demonstrating the LCX defect, were obtained in all dogs. The correlation coefficient was 0.98 for regional myocardial blood flow vs initial Tc-TBI distribution. IN CONCLUSION: (1) Dipyridamole vasodilation unmasked coronary stenoses despite no flow disparities at rest. (2) The initial distribution of Tc-TBI is proportional to regional myocardial blood flow. (3) There is minimal washout and no redistribution into the initial defect over time, and thus image quality is stable over time. (4) Tc-TBI myocardial kinetics may be applicable to closely related agents currently being developed.

Animals↗
PubMed1988

The clinical and pathophysiologic implications of pain, ST abnormalities, and scintigraphic changes induced during dipyridamole infusion: their relationships to the peripheral hemodynamic response.

In order to determine their significance during dipyridamole perfusion scintigraphy, symptomatic, ECG, and scintigraphic findings were related to each other, to the hemodynamic response, and to angiographic findings in 73 consecutive patients having coronary angiography within 3 months of scintigraphy. The group having induced "cardiac" pain differed from the group without induced pain only in their higher incidence of induced ischemic ST changes, the "marked" hemodynamic response, and their lower incidence of an "absent" hemodynamic response (all p less than 0.01). Induced ST depression was found only in patients with coronary disease. In this population, dipyridamole-induced pain was a moderately specific marker and induced ST abnormalities a more highly specific marker for coronary disease. However, both were insensitive for coronary disease diagnosis. If induced pain or ST abnormalities in the presence of significant coronary disease were accepted as indicators of ischemia, then scintigraphic abnormalities appeared to be produced by dipyridamole in roughly equal incidence by ischemic and nonischemic mechanisms. Induced ischemia related frequently to an exaggerated hypotensive response with no change in double product, suggesting its cause to be an induced increase in myocardial oxygen demand. Dipyridamole-induced image defects were noted even in the absence of a peripheral hemodynamic response. This indicates that the peripheral response does not always correlate with its central coronary effect and an absent peripheral hemodynamic response does not necessarily invalidate scintigraphic results.

Angina Pectoris↗
PubMed1989

Role of myocardial oxygen consumption in dipyridamole-induced ischemia.

The aim of this study was to assess whether myocardial oxygen consumption can be responsible for aminophylline resistance in dipyridamole-induced ischemia. We analyzed 163 consecutive patients who had a positive low-dose (0.56 mg/kg over 4 minutes) dipyridamole-echocardiography test, requiring intravenous aminophylline as an antidote. All patients also performed an exercise stress test. In 141 of these patients, the signs of ischemia were reversed by administration of intravenous aminophylline (group I), while the remaining 22 patients were resistant to aminophylline (240 mg/kg over 3 minutes) and received additional treatment with nitrates to relieve ischemia (group II). The increase in rate-pressure product (RPP = mm Hg x beats/min x 100) measured during the exercise stress test in the patients in group I was significantly greater than that determined during dipyridamole-induced ischemia (204 +/- 41 versus 145 +/- 33, p less than 0.01). However, the increases in RPP under both conditions were similar for the patients in group II (147 +/- 24 versus 150 +/- 20, p = ns). In patients with dipyridamole-induced ischemia who were resistant to aminophylline, the rise in myocardial oxygen consumption--probably linked to reflex sympathetic activation--might maintain ischemia independently from flow maldistribution, which should be reversed by aminophylline.

Aminophylline↗
PubMed1989

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)

Aminophylline↗
PubMed1991

Dipyridamole-induced decrement of functional recovery of postischemic reperfused myocardium in conscious dogs with well-developed coronary collateral circulation.

The effects of dipyridamole (20 and 40 micrograms/kg/min intravenously) on the time course of functional recovery of myocardium after five 5-minute coronary artery occlusions and four 5-minute reperfusions and a subsequent 5-hour reperfusion period were studied in chronically instrumented, conscious dogs with well-developed coronary collateral circulation. In comparison with vehicle-treated control dogs, those given dipyridamole (20 and 40 micrograms/kg/min, respectively) 15 minutes before and during coronary occlusion had a greater depression of regional segment shortening (38 +/- 7% and 19 +/- 4%, respectively, vs control levels of 69 +/- 10% of preocclusion values) during acute coronary artery occlusion. After a 5-hour reperfusion period, segment shortening returned to preocclusion values in the control group but remained decreased in the dipyridamole groups (87 +/- 4% and 75%, respectively). These results suggest that dipyridamole in a dose-dependent manner exacerbates recovery of contractility of postischemic reperfused myocardium in dogs with well-developed coronary collateral circulation.

Animals↗
PubMed1991

Two-dimensional Doppler echocardiographic correlation of dipyridamole-thallium stress testing with isometric handgrip.

To determine how frequently new wall-motion abnormalities that are indicative of ischemia accompany thallium redistribution, 47 consecutive patients underwent two-dimensional echocardiography during routine dipyridamole-thallium stress testing. A secondary aim of the study was to determine whether the addition of isometric handgrip exercises to the standard dipyridamole imaging protocol increased the frequency of wall-motion abnormalities or thallium redistribution. Echocardiograms and thallium scans were independently interpreted, and wall-motion abnormalities that appeared with dipyridamole, handgrip exercise, or both were compared with results of thallium imaging. Five of 24 patients with thallium redistribution had new wall-motion abnormalities, and the extent (number of segments) of thallium redistribution in these five patients was significantly greater than in those who did not have well-motion abnormalities (p less than 0.03). The addition of isometric handgrip exercises to the imaging protocol did not distinguish between patients with and without new wall-motion abnormalities or thallium redistribution. Thus new wall-motion abnormalities infrequently accompany thallium redistribution in routine dipyridamole stress testing in spite of the addition of handgrip exercises, but when new wall-motion abnormalities are present, they are associated with a greater area of thallium redistribution.

Coronary Disease↗
PubMed1992

Therapeutic effect of oral dipyridamole on myocardial perfusion and cardiac performance in patients with hypertrophic cardiomyopathy.

Recent studies have indicated that myocardial ischemia could occur and could play an important role in the pathophysiology of patients with hypertrophic cardiomyopathy (HCM). We therefore investigated whether or not dipyridamole--a selective coronary vasodilating agent--could favorably modify myocardial perfusion and the clinical manifestations in 20 patients with HCM (19 nonobstructive and one mildly obstructive) with an average age of 50 years. Oral dipyridamole, 150 mg/day for 2 weeks, prevented reversible perfusion defects initially observed in six patients on baseline exercise thallium-201 (201TI) scintigraphy and significantly increased the 201TI clearance (40 +/- 13% to 44 +/- 12%), while one patient developed new reversible perfusion defects. There were significant increases in echocardiographic fractional shortening and treadmill exercise time and reductions in cardiac size and supraventricular arrhythmias with dipyridamole therapy. These observations suggest that coronary vasodilation with dipyridamole may improve myocardial perfusion and cardiac function in patients with HCM.

Administration, Oral↗
PubMed1994

Effect on early acute occlusion rate of adjunctive antithrombotic treatment with intravenously administered dipyridamole during percutaneous transluminal coronary angioplasty.

This study compared the acute occlusion and complication rates within 24 hours of coronary angioplasty in three groups of patients. In group 1, 178 procedures were performed by one operator who administered 30 mg of dipyridamole intravenously over 1 hour, starting immediately before the procedure; in group 2, 200 procedures were performed by the same operator before he administered dipyridamole; and in group 3, 599 procedures were performed during the same time period in the same catheterization laboratory by two other operators who did not administer dipyridamole. All patients received an intravenous bolus of heparin and aspirin. Baseline variables were similar in the three groups. The acute closure rate was 2.8% in group 1, 7.5% in group 2, and 5.2% in group 3 (p < 0.05 between groups 1 and 2); acute thrombosis was observed in 0.6%, 3.5%, and 3% of patients, respectively, in the three groups (p < 0.05 between group 1 and both groups 2 and 3), and acute dissection was noted in 2.2%, 4%, and 2% of patients, respectively (p = not significant). The cumulative rate of acute complications (death, acute myocardial infarction, or emergency coronary bypass surgery) was lower in group 1 (1.7%) than in group 2 (5.5%, p < 0.05) and group 3 (3.5%, p = not significant). Therefore in this retrospective study, adjunctive antithrombotic treatment with intravenously administered dipyridamole resulted in lower acute thrombosis and complication rates during the 24-hour period after the procedure than when heparin and aspirin therapy were used alone.

Acute Disease↗
PubMed1995

Prognostic value of predischarge dipyridamole technetium 99m sestamibi myocardial tomography in medically treated patients with unstable angina.

Recently developed unstable angina clinical practice guidelines have recommended risk stratification with dipyridamole thallium-201 myocardial imaging in patients at "intermediate" pretest clinical risk who cannot exercise maximally. The prognostic value of predischarge dipyridamole technetium 99m sestamibi (MIBI) tomography has not been assessed in this clinical setting. To this end, 128 medically treated patients with unstable angina at intermediate pretest clinical risk underwent follow-up for 16 +/- 11 (mean +/- SD) months after predischarge intravenous dipyridamole MIBI tomography. An abnormal MIBI scan result was present in 99 patients (77%), of whom 47 had one or more reversible and 76 had one or more fixed perfusion defects. Cardiac events occurred in 68 (53%) patients after dipyridamole testing: recurrent unstable angina (n = 36), nonfatal acute myocardial infarction (n = 6), or death (n = 26). A cardiac event occurred in 10% of patients with normal MIBI tomography results compared with 69% of those with abnormal results (p < 0.01). Event rates associated with specific perfusion defects were similar (reversible = 68%; fixed = 71%) and were greater than rates in patients without defects (both p < 0.05). Clinical variables associated with increased risk of cardiac events by univariate analysis included a history of congestive heart failure, prior myocardial infarction, and diabetes mellitus (all p < 0.05). Independent multivariable predictors (Cox proportional hazards model) of any cardiac event were an abnormal result of MIBI scan (relative risk [RR] = 4.3, 95% confidence interval [CI] 1.5 to 12.0) and a reversible (RR = 1.8, 95% CI 1.1 to 2.9) or a fixed perfusion defect (RR = 2.9, 95% CI 1.6 to 5.4).(ABSTRACT TRUNCATED AT 250 WORDS)

Angina, Unstable↗
PubMed1981

Intravenous dipyridamole combined with isometric handgrip for near maximal acute increase in coronary flow in patients with coronary artery disease.

Twenty-four patients with coronary artery disease were studied during cardiac catheterization to determine the effects of sustained isometric handgrip exercise and intravenous dipyridamole and their combination on coronary and systemic hemodynamics and measured coronary luminal caliber. During 4 to 5 minutes of 25 percent maximal handgrip, blood pressure and heart rate increased 24 and 19 percent, respectively, coronary sinus flow increased to 1.7 x baseline value, and epicardial coronary arteries constricted to increase predicted flow resistance by 40 percent in 36 diseased arterial segments. After a 4 minute intravenous infusion of dipyridamole (0.56 mg/kg body weight), systemic pressure decreased 8 percent, heart rate increased 23 percent, coronary sinus flow increased to 2.4 x baseline value and coronary luminal caliber was unchanged. During isometric handgrip initiated 6 minutes after the infusion of dipyridamole, systemic pressure and heart rate increased to 14 and 31 percent, respectively, above control values, coronary sinus flow increased to 3.3 x baseline value (3.8 x baseline value in patients with normal anterior perfusion) and stenotic flow resistance increased by 36 percent. The response of coronary flow to the combined stresses was 68 percent greater than the response to dipyridamole alone (p less than 0.02); these flow levels exceed values previously reported for the human coronary circulation. Aminophylline plus nitroglycerin appears to assure patient safety.

Acute Disease↗
PubMed1984

Significance of increased lung thallium-201 activity on serial cardiac images after dipyridamole treatment in coronary heart disease.

Increased lung thallium-201 (Tl-201) activity occurs in patients with severe coronary artery disease (CAD) on initial postexercise images. To determine the significance of assessing lung Tl-201 on serial imaging after dipyridamole therapy, initial and delayed (2 to 3 hours) Tl-201 imaging was performed in 40 patients with CAD and 26 normal control subjects. Lung Tl-201 activity was quantitated as a percentage of maximal myocardial activity for each imaging time (lung Tl-201 index). The mean initial lung Tl-201 activity was 42 +/- 2% (+/- standard error of the mean) in 26 control subjects, 56 +/- 2% in 25 patients with 2- or 3-vessel CAD (p less than 0.001) and 53 +/- 2% in 15 patients with 1-vessel CAD (p less than 0.005 compared with control subjects) (difference not significant between 1-vessel and multivessel CAD). Dipyridamole lung Tl-201 activity decreased relative to the myocardium from initial to delayed images (p less than 0.001) in patients with CAD but not in control subjects. When a dipyridamole lung Tl-201 index of 58% (mean +/- 2 standard deviations for control subjects) was chosen as the upper limit of normal, 14 of 40 of the CAD patients (35%) had abnormal values and all control patients had values within normal limits. These 14 patients with CAD and abnormal initial lung Tl-201 indexes had rest ejection fractions that were not significantly different from those in patients with CAD, and normal initial dipyridamole lung Tl-201 index (58 +/- 4% and 63 +/- 2%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Effects of dipyridamole and low-dose aspirin therapy on platelet adhesion to vascular subendothelium.

The effect on platelet function of low-dose aspirin (ASA) and dipyridamole alone or in combination was evaluated after repeated dosing in 5 healthy volunteers. The subjects were treated according to a randomized, single-blind, crossover design with 150 mg of dipyridamole, 25 mg of ASA, the 2 drugs together or placebo twice a day for 3 days. Platelet adhesin was evaluated using an experimental model of adhesion to rat aorta subendothelium under controlled hemodynamic conditions in the presence of red blood cells. Dipyridamole significantly reduced platelet adhesion both alone and in combination with ASA. ASA by itself did not significantly modify platelet adhesion, but completely blocked serum thromboxane production and platelet aggregation by arachidonic acid. Thus, low-dose ASA and dipyridamole may have a complementary action, modifying at the same time 2 platelet functions, adhesion and aggregation, both relevant in the pathogenesis of thrombosis.

Adult↗
PubMed1987

Limitations of dipyridamole-echocardiography in effort angina pectoris.

The sensitivity of dipyridamole--2-dimensional (2-D) echocardiography was assessed for detection and localization of ischemia in 21 patients with severe chronic stable angina pectoris, a clearly positive exercise stress test response and multivessel coronary atherosclerosis. Regional wall motion during dipyridamole infusion (0.6 mg/kg intravenously over 4 minutes) was compared with control and recovery by 2 blinded observers in consensus. Transient regional wall motion abnormalities were observed in 11 patients. Angina and ST-segment changes occurred in 9 of these 11 patients with positive responses, but in none of those who showed no transient abnormality of regional wall motion. Localization of regional wall motion abnormalities correlated well with angiographic severity of coronary lesions. Endocardial area contraction, evaluated by a computerized system, was reduced significantly after dipyridamole administration in patients with a positive response (from 51 +/- 10% to 35 +/- 11%, p less than 0.001), whereas it did not change significantly in the others (from 43 +/- 6% to 42 +/- 8%). In the 11 patients with a positive response, coronary reserve assessed by exercise testing (modified Bruce protocol) was more impaired than in those with a negative response (time to 1 mm of ST depression 177 +/- 148 seconds and 472 +/- 179 seconds, respectively, p less than 0.01). In patients with severe angina and multivessel coronary artery disease, dipyridamole--2-D echocardiography appears to identify the vessel in which flow reserve is most limited. Although this information may be valuable, indications for the test are restricted to patients with severely limited exercise capacity.

Adult↗
PubMed1989

Regional and global biventricular function during dipyridamole stress testing.

This study assesses the relation between regional ventricular performance (using 2-dimensional echocardiography) and global systolic and diastolic indexes of biventricular myocardial function (using hemodynamic monitoring) during dipyridamole stress testing. Simultaneous 2-dimensional echocardiographic and biventricular hemodynamic monitoring during dipyridamole infusion (0.56 mg/kg over 4 minutes) was performed in 19 patients. All patients had a normal resting function. Eleven of the 19 patients had a positive echocardiography test (new wall motion dyssynergy with dipyridamole) and they formed group 1. Eight patients had a negative echocardiography test (group 2). During baseline conditions, no significant differences were found in the 2 groups: rate pressure product (107 +/- 16 vs 108 +/- 13 mm Hg x beats/min x 1/100), positive left ventricular (LV) dP/dt (1,950 +/- 473 vs 2,262 +/- 430 mm Hg/s), negative LV dP/dt (-2,069 +/- 620 vs -2,205 +/- 245), LV end-diastolic pressure (8.2 +/- 4.4 vs 9.6 +/- 4.0 mm Hg), right ventricular positive dP/dt (368 +/- 133 vs 400 +/- 190 mm Hg/s) and negative dP/dt (-281 +/- 89 vs -383 +/- 147). At peak dipyridamole, the 2 groups were different for LV end-diastolic pressure (20 +/- 10 vs 8 +/- 5 mm Hg, p less than 0.01), LV positive dP/dt (2,100 +/- 688 vs 3,013 +/- 851 mm Hg/s, p less than 0.01) and negative dP/dt (-1,868 +/- 518 vs -2,564 +/- 272, p less than 0.01). At peak ischemia, LV positive dP/dt increased slightly, but not significantly, while negative dP/dt decreased significantly (p less than 0.01) in comparison with resting values.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Predictive value of quantitative dipyridamole-thallium scintigraphy in assessing cardiovascular risk after vascular surgery in diabetes mellitus.

Cardiac complications represent a major risk to patients undergoing vascular surgery. Diabetic patients may be particularly prone to such complications due to the high incidence of concomitant coronary artery disease, the severity of which may be clinically unrecognized. Attempts to stratify groups by clinical criteria have been useful but lack the predictive value of currently used noninvasive techniques such as dipyridamole-thallium scintigraphy. One hundred one diabetic patients were evaluated with dipyridamole-thallium scintigraphy before undergoing vascular surgery. The incidence of thallium abnormalities was high (80%) and did not correlate with clinical markers of coronary disease. Even in a subgroup of patients with no overt clinical evidence of underlying heart disease, thallium abnormalities were present in 59%. Cardiovascular complications, however, occurred in only 11% of all patients. Statistically significant prediction of risk was not achieved with simple assessment of thallium results as normal or abnormal. Quantification of total number of reversible defects, as well as assessment of ischemia in the distribution of the left anterior descending coronary artery was required for optimum predictive accuracy. The prevalence of dipyridamole-thallium abnormalities in a diabetic population is much higher than that reported in nondiabetic patients and cannot be predicted by usual clinical indicators of heart disease. In addition, cardiovascular risk of vascular surgery can be optimally assessed by quantitative analysis of dipyridamole-thallium scintigraphy and identification of high- and low-risk subgroups.

Angina Pectoris↗
PubMed1990

Ability of dipyridamole-thallium-201 imaging one to four days after acute myocardial infarction to predict in-hospital and late recurrent myocardial ischemic events.

The ability of dipyridamole-thallium-201 imaging to predict in-hospital and late cardiac events when performed very early (62 +/- 21 hours, range 23 to 102) after acute myocardial infarction (AMI) was tested in 50 patients. During hospitalization, 1 patient developed recurrent AMI and 8 patients developed recurrent angina after MI associated with ST-segment depression at 60 +/- 42 hours after the dipyridamole-thallium-201 imaging; of these, 6 required urgent coronary revascularization. No patient died in-hospital. There were no serious adverse effects during the dipyridamole protocol. Using stepwise multivariate logistic regression analysis, the best and only statistically significant predictor of in-hospital ischemic cardiac events was the presence of thallium-201 redistribution within the infarct zone (p = 0.0001). Of 20 patients with infarct zone thallium-201 redistribution, 9 (45%) developed in-hospital ischemic cardiac events compared to 0 of 30 patients without infarct zone thallium-201 redistribution (p less than 0.0001). During a follow-up 12 +/- 7 months after discharge, 3 additional patients with infarct zone thallium-201 redistribution developed recurrent AMI or unstable angina, whereas no patient without infarct zone thallium-201 redistribution developed ischemic cardiac events. These data suggest that dipyridamole-thallium-201 imaging performed very early after AMI may identify a subgroup of patients at high risk for in-hospital and late ischemic cardiac events. Such patients may benefit from early cardiac catheterization and revascularization. Patients without infarct zone thallium-201 redistribution appear to be at very low risk for in-hospital and late ischemic cardiac events and may be candidates for early discharge.

Coronary Disease↗
PubMed1990

Usefulness of semiquantitative analysis of dipyridamole-thallium-201 redistribution for improving risk stratification before vascular surgery.

Preoperative dipyridamole-thallium-201 scanning is sensitive in identifying patients prone to ischemic cardiac complications after vascular surgery, but most patients with redistribution do not have an event after surgery. Therefore, its positive predictive value is limited. To determine which patients with thallium redistribution are at highest risk, dipyridamole-thallium-201 images were interpreted semiquantitatively. Sixty-two consecutive patients with redistribution on preoperative dipyridamole-thallium-201 planar imaging studies were identified. Each thallium scan was then analyzed independently by 2 observers for the number of myocardial segments out of 15, the number of thallium views out of 3 and the number of coronary artery territories with redistribution. Seventeen patients (27%) had postoperative ischemic events, including unstable angina pectoris, ischemic pulmonary edema, myocardial infarction and cardiac death. Thallium predictors of ischemic operative complications included thallium redistribution greater than or equal to 4 myocardial segments (p = 0.03), greater than or equal to 2 of the 3 planar views (p = 0.005) and greater than or equal to 2 coronary territories (p = 0.007). No patient with redistribution in only 1 view had an ischemic event (0 of 15). Thus, determining the extent of redistribution by dipyridamole-thallium-201 scanning improves risk stratification before vascular surgery. Patients with greater numbers of myocardial segments and greater numbers of coronary territories showing thallium-201 redistribution are at higher risk for ischemic cardiac complications. In contrast, when the extent of thallium redistribution is limited, there is a lower risk despite the presence of redistribution.

Aged↗