Dipyridamole Myocardial Scintigraphy Research Articles

Dipyridamole-Associated Shock and Pulmonary Edema

To report a case of fulminant shock and noncardiogenic pulmonary edema induced by intravenously administered dipyridamole. A 73-year-old woman presented to the office of her cardiologist for dipyridamole myocardial scintigraphy. Several minutes after administration of intravenous dipyridamole 0.57 mg/kg over 4 minutes she developed wheezing, followed by cardiovascular collapse and pulmonary edema requiring 100% oxygen and endotracheal intubation. She had never received dipyridamole before this, and no other medications or exposures were documented proximate to the collapse. On transfer to the hospital, she developed shock refractory to multiple vasopressors, which responded to continuous infusions of epinephrine. She also had severe pulmonary edema requiring invasive ventilation, 100% inspired oxygen, and 24 cm H₂O positive end-expiratory pressure. An echocardiogram did not show new left-ventricular dysfunction and there were signs of right-heart underfilling, supporting a diagnosis of noncardiogenic pulmonary edema. Both shock and pulmonary edema resolved within 12 hours. Dipyridamole-associated hypotension has been reported in a number of case series and registries. Detailed case descriptions, however, are not available in the literature to permit understanding of the mechanism of shock following hypotension resulting from dipyridamole myocardial scintigraphy. Our case is exceptional in that echocardiography results support a diagnosis of hypovolemic (rather than cardiogenic) shock. To our knowledge, this is the first case of severe (most likely noncardiogenic) pulmonary edema associated with intravenous infusion of dipyridamole. An objective causality assessment suggested that this patient's cardiopulmonary collapse was probably related to dipyridamole. While hypotension has been previously associated with intravenous use of dipyridamole, ours is the first report to suggest a noncardiogenic mechanism for shock. To our knowledge, this is the first reported case of noncardiogenic pulmonary edema following dipyridamole infusion.

Transitory Myocardial Ischemia in Patients with Vascular Lower Limb Amputation

To evaluate the prevalence of asymptomatic transitory myocardial ischemia during scintigraphy among amputees of vascular etiology as well as to ascertain correlation with atherothrombotic events during long-term follow-up. A cohort, mean follow-up of 2.1 yrs study was performed in an outpatient rehabilitation clinic with 58 lower limb vascular amputees who were referred for rehabilitation, asymptomatic for coronary heart disease. Patients were evaluated for myocardial ischemia by dipyridamole scintigraphy, and occurrence of severe cardiovascular events (death, acute myocardial infarction, stroke, and peripheral ischemia with hospitalization) was assessed. Of the 58 patients, 26 (44.8%) had positive dipyridamole myocardial scintigraphy for transitory myocardial ischemia. During follow-up, 12 subjects (20.7%), mainly diabetic patients (83%), registered a serious cardiovascular event, with 9 of 12 events having occurred in those who had tested positive for transitory ischemia on scintigraphy (P < 0.025). There were five deaths (19.2%) in those with a positive scintigraphy and a single death (3.1%) in those with a negative dipyridamole test, although the Kaplan-Meier survival curve and Cox regression were not significant (P = 0.09 and 0.1, respectively). We found that 44.8% of patients with vascular lower limb amputation, asymptomatic for coronary disease, tested positive on myocardial scintigraphy for transitory myocardial ischemia. In a mean follow-up of 2.1 yrs, there was 10.3% of atherothrombotic events/year, with a higher death toll in those patients with positive scintigraphy.

Simultaneous operation of ischemic heart disease, abdominal aortic aneurysm, and rectal cancer

A 68-year-old man with ischemic heart disease, abdominal aortic aneurysm, and rectal cancer was referred. Coronary angiography indicated triple-vessel disease with jeopardized collaterals, and dipyridamole myocardial scintigraphy disclosed no viability in the inferior, posterior, and lateral walls. Abdominal computed tomography scanning revealed an infrarenal abdominal aortic aneurysm, 65 mm in diameter, with an expanding rate of 8 mm/year. Barium enema revealed stenosis 4 cm in length 5 cm inward from the anal verge, and an endoscopic finding was ulcerated type tumor with a clear margin and circumferential stenosis. Histological examination of a biopsy specimen revealed adenocarcinoma, and the clinical stage in the Japanese classification of colorectal carcinoma was II according to other examinations. Simultaneous operations were scheduled because of the jeopardized collaterals of the coronary arteries, rapid expansion of the aneurysm, and subileus due to the cancer. The patient underwent simultaneous off-pump coronary artery bypass grafting to the left anterior descending artery with the in situ internal thoracic artery through a median sternotomy, abdominal aortic aneurysm repair with a tube graft through a median laparotomy, and the Miles' operation with total mesorectal excision. Although infection of the perineal wound was postoperatively recognized, it remained local and was healed with irrigation only. The patient is doing well 12 months after the operation, without myocardial ischemic symptoms or recurrence of the cancer.

ECG-manifest and ECG-silent dipyridamole technetium-99m sestamibi SPET perfusion defects in patients with ischaemic heart disease.

At dipyridamole myocardial scintigraphy, perfusion defects are seldom backed up by significant ECG changes. This would suggest myocardial blood flow heterogeneity, rather than true ischaemia, as the cause of the scintigraphic abnormalities. Electrocardiographic surface mapping has been documented to be more accurate than standard 12-lead ECG in the detection of provoked ischaemia. Thus, to investigate the relationship between ECG changes and perfusion abnormalities, body surface maps were recorded during dipyridamole infusion in 55 subjects (11 normals and 44 patients with ischaemic heart disease) undergoing dipyridamole technetium-99m sestamibi single-photon emission tomography (SPET). All had a normal resting ECG. The extent and severity of the sestamibi defect were quantified. New negative areas in the isointegral maps and rest-dipyridamole map differences >2 SD from normal limits were considered abnormal. After dipyridamole in normals, neither perfusion defects nor >/=1 mm ST segment depression on 12-lead ECG nor new negative areas in isointegral maps occurred. In patients, dipyridamole induced new perfusion defects in 35 (80%) but ST segment depression in only 18 (41%, P<0.001). Of the 35 patients with perfusion defects, 17 (49%, group 1) showed ST segment depression, while the other 18 (51%, group 2) did not. Abnormal body surface maps were found in 100% of group 1 and 88% of group 2 patients (NS). In group 1, the provoked hypoperfusion was of greater extent (P=0.007) and severity (P=0.01) and the onset of map abnormalities was significantly earlier (P<0. 001) than in group 2; time to map abnormalities was also significantly shorter than time to ST segment depression (P=0.01). In the 35 patients with complete scintigraphic, body map and angiographic data, the severity of reversible perfusion defect proved to be the strongest correlate of ST segment depression upon logistic regression analysis. Thus, sestamibi SPET abnormalities after dipyridamole are almost always associated with electrical changes on body surface maps, suggesting myocardial ischaemia as their cause. The much less common 12-lead ECG changes are slower to appear and reflect a more severe hypoperfusion.

Outpatient echocardiography as a predictor of perioperative cardiac morbidity after peripheral vascular surgical procedures

A variety of preoperative provocative tests have been used to define the risk of cardiac morbidity and mortality after peripheral vascular procedures, including dipyridamole myocardial scintigraphy and dobutamine stress echocardiography. Although highly sensitive, these tests are time-consuming and associated with significant expense. We investigated outpatient echocardiography as a less resource-intensive means of assessing cardiac risk with operation. Over a 2-year period 250 consecutive patients underwent outpatient transthoracic echocardiography before elective peripheral vascular operation was performed. The accuracy of the Goldman, Detsky, and the American Society of Anesthesiologists' Physical Status Classification clinical indexes of cardiac risk were assessed with regard to the development of cardiac complications such as unstable angina, myocardial infarction, life-threatening ventricular arrhythmias, severe congestive heart failure, and cardiogenic shock. The accuracy of echocardiographically determined left ventricular ejection fraction was determined at threshold values between 20% and 60%. Perioperative cardiac events developed in 23 (9.2%) of the patients, and nine (3.6%) of the patients died as a result of these complications. Clinical indexes lacked sensitivity in the preoperative prediction of cardiac complications. Receiver operating curve analysis defined a left ventricular ejection fraction of less than 50% as an appropriate threshold for defining patients at high risk, with a sensitivity of 78% and a specificity of 81% in the identification of patients who had cardiac morbidity. The positive predictive value was 27%, and the negative predictive value was 97%. The economic impact of outpatient echocardiography was well below that of dipyridamole myocardial scintigraphy or dobutamine stress echocardiography. Outpatient echocardiography appears to offer a cost-efficient compromise between clinical criteria alone and provocative cardiac testing such as dipyridamole myocardial scintigraphy and dobutamine stress echocardiography in the preoperative screening of patients undergoing peripheral vascular surgical procedures.

Detection of coronary artery disease in diabetic patients

Coronary artery disease may be difficult to detect in diabetic patients. This study was designed to determine the specificity and sensitivity of three non-invasive tests. Accordingly, the results of 48-h ambulatory electrocardiogram (ECG) monitoring, maximal ECG exercise test, and intravenous dipyridamole myocardial thallium scintigraphy were compared in 59 middle-aged diabetic patients who were consecutively selected for suspected coronary artery disease. All patients also underwent coronary angiography, which was performed regardless of the results of the non-invasive tests. Twenty patients (34%) had significant coronary lesions, i.e. stenosis equal to or greater than 70%, and 16 of these 20 patients (80%) had double or triple vessel disease. Sensitivity and specificity were, respectively, 25% and 88% for ambulatory ECG monitoring, 75% and 77% for the exercise test and 80% and 87% for thallium myocardial scintigraphy. This observation strongly supports the use of non-invasive tests for the detection of coronary artery disease in those diabetic patients at high risk of such disease. As the exercise test is cheaper and more widely available than thallium myocardial scintigraphy it should be used as a first line examination. Dipyridamole myocardial scintigraphy may provide an alternative solution for those patients who cannot perform maximal exercise, or with atypical clinical presentation.

Thallium-201 rest and dipyridamole myocardial scintigraphy in essential hypertension patients with and without LV hypertrophy: Total perfusion reserve and viability

Thallium-201 rest and dipyridamole myocardial scintigraphy in essential hypertension patients with and without LV hypertrophy: Total perfusion reserve and viability

An assessment of the positive predictive value and cost-effectiveness of dipyridamole myocardial scintigraphy in patients undergoing vascular surgery

The approach to cardiac risk stratification of patients undergoing vascular surgery continues to be controversial. The success of algorithms that use clinical risk factors to determine cardiac risk have been inconsistent. Dipyridamole myocardial scintigraphy (DMS) has been accepted as a sensitive, noninvasive approach to risk stratification with excellent negative predictive value. Low positive predictive value (PPV) of abnormal DMS scans is a shortcoming that contributes to extensive preoperative cardiac evaluation and intervention with associated morbidity, mortality, and cost in most patients who undergo uncomplicated vascular procedures, regardless of DMS results. Over 6 years, 237 patients underwent DMS before surgical management of infrarenal aortic aneurysm, aortoiliac, or infrainguinal occlusive disease. The value of multiple clinical factors and DMS were assessed retrospectively for the prediction of perioperative myocardial infarction (MI), heart-related death, or preoperative selection for myocardial revascularization. Only congestive heart failure and two or more reversible defects on DMS were statistically significant on logistic regression analysis. The PPV of DMS was 19% for all patients with reversible defects, 12% for patients with one reversible defect, and 36.7% for patients with two or more reversible defects. The rates of cardiac death and MI were 1.3% and 5.9%, respectively. Perioperative echocardiography revealed unchanged postinfarction ejection fraction in most patients who experienced MI. Cost-effectiveness of DMS screening was evaluated. The costs per MI and cardiac death averted suggest a decline in cost-effectiveness of screening with DMS over time, assuming improving cardioprotective strategies of patient care. Clinical risk factors were minimally useful in the prediction of perioperative MI, heart-related death, or need for myocardial revascularization. The PPV of DMS is low, and the majority of MIs may be clinically insignificant. The cost-effectiveness of cardiac screening with DMS may not be justifiable given current trends of health care reform.

Coronary spasm induced by dipyridamole during a myocardial scintigraphy

A 59-year-old male underwent a dipyridamole myocardial scintigraphy. During dipyridamole infusion, a marked ST-segment elevation was observed in the inferior leads. After aminophylline injection, a short burst of ventricular tachycardia occurred, then the ST-segment elevation disappeared. The myocardial scintigraphy was consistent with myocardial ischemia of the inferior wall. The coronary angiography revealed no significant coronary lesion. Coronary spasm induced by dipyridamole remained the most probable mechanism for this complication.