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

Overview of stress echocardiography: uses, advantages, and limitations

Responses of the heart to changes in our environment are probably even more important than how the heart functions at rest. Accordingly, stress testing with noninvasive imaging has become important for diagnosis, prognosis, and monitoring the effects of therapy. Echocardiography at rest and with stress permits characterization of global and segmental left ventricular function as well as valvular structure and function. Moreover, echocardiography can be performed during or after a number of different physical or even mental stressors. Advantages of stress echocardiography include its ready availability, relatively low capital cost, and incremental value in that it allows characterization of cardiac anatomy as well as the myocardial response to a potentially ischemic stimulus. Moreover, echocardiography has the potential to image myocardial perfusion along with wall motion and wall thickening. Substantial literature has now been accumulated on the value of stress echocardiography for the diagnosis of ischemic disease, preoperative risk assessment, and assessment of myocardial viability. Echocardiography has compared generally well with nuclear imaging techniques for the detection of angiographic coronary artery disease. Overall sensitivity, however, has been slightly less, particularly for the detection of single-vessel coronary disease, although specificity has been on average somewhat higher than nuclear cardiology techniques. Because of the potential for variability in study acquisition as well as interpretation, careful safeguards need to be employed. Specifically, meticulous technique needs to be applied to obtain high-quality images and to assure that those images are obtained promptly after treadmill exercise stress. Only readers with specific interest and expertise should interpret stress echocardiography studies. Continuing efforts need to be made to assess and minimize variability and to assure continuing quality improvement. Advances in instrumentation, including evolving technology for real-time 3-dimensional imaging, and echocardiography contrast assessment of myocardial perfusion will likely improve the sensitivity of echocardiography and further extend its usefulness.

Perioperative myocardial infarction with noncardiac surgery

The incidence of perioperative myocardial infarction with noncardiac surgery varies by the type of procedure and the prevalence of coronary atherosclerosis in the study population. Incidence is < or = 1% with minor procedures and may exceed 10% with vascular operations. The case fatality rate continues to be 30% to 50%. Pathogenesis is not understood completely. Diagnosis is sometimes problematic, because less than 50% of patients complain of chest pain. In addition, a high frequency of notable but apparently innocent postoperative electrocardiograph changes limits the diagnostic use of the electrocardiogram. Fortunately, the creatine kinase MB isoenzyme retains its sensitivity and specificity for acute infarction in perioperative patients. Different approaches to preoperative risk assessment have been developed, including a summative cardiac risk index and a stratification system based on the likelihood that the most powerful risk factor (coronary artery disease) is present. Although many interventions have been recommended to lower perceived risk, none has been tested in a randomized controlled trial, and their comparative efficacy and safety is unknown.

Dose and test for dipyridamole infusion and cardiac imaging early after uncomplicated acute myocardial infarction

To evaluate the relation of the dose of intravenous dipyridamole on results of thallium and echocardiographic testing, the results of standard- (0.56 mg/kg/4 minutes) versus high- (0.84 mg/kg/10 minutes) dose dipyridamole were obtained 9 +/- 3 days after uncomplicated acute myocardial infarction in 57 patients. New wall motion abnormalities were compared with redistribution of thallium imaging and results of discharge coronary angiography. The sensitivity of thallium in predicting the presence of multivessel coronary artery disease was significantly (p < 0.01) higher (85%) than echocardiography (53%) and was unaffected by the dose. However the sensitivity of echocardiography was better with the higher dose (53 vs 14%). Minor adverse effects occurred in 34 patients (59%) after receiving the high dose and only in 4 patients (7%) after the standard dose (p < 0.001). Thus, thallium-201 scintigraphy during standard-dose dipyridamole infusion is more effective than high-dose dipyridamole echocardiographic testing in safely identifying patients who could benefit from early invasive evaluation and therapy.