Noninvasive Risk Stratification in Patients after AMI
Several noninvasive modalities of stress testing are widely used for the functional and prognostic assessment of patients following AMI. The predischarge exercise ECG can reflect the risk of subsequent ischemic events when no preexisting ST-segment abnormalities are present. However, because of its limited diagnostic sensitivity, the requirement for no preexisting ECG changes, and the reduced exercise capacity of patients after AMI, exercise ECG is not as good as either the stress scintigraphy or the stress echocardiography. Treadmill stress echocardiography also provides useful information for assessing the risk of subsequent ischemic events, such as exercise endurance and time to the development of symptoms, and is therefore helpful in providing indicators for proper exercise rehabilitation. canadian healthcare mall
However, pharmacologic stress tests are more suitable for those patients who do not have the physical function to perform treadmill stress tests. Compared to stress scintigraphy, the diagnostic accuracy of DSE is more dependent on the quality of echocardiographic images and the physician’s experience in interpreting them, but there is more information obtained from echocardiographic evaluation at peak stress and the ischemic threshold as assessed by dobutamine time. There are no reported data comparing the prognostic value of DSE and stress scintigraphy in predicting future cardiac events in diabetic patients following AMI. In general, exercise and pharmacologic stress echocardiography are less costly than radionuclide stress scintigraphy. As the experience in this study shows, an early (1 week after AMI) or predischarge DSE is safe and valuable in the risk stratification for further cardiac outcomes.
There are some important limitations of this study. Because relatively few cardiac events occurred, a definite conclusion on the prognostic value of DSE in diabetic patients cannot be obtained. The patient numbers were relatively small, and a larger sample of diabetic patients may provide more information. Despite the relatively small sample of patients, we were able to show that the diabetic patients with a shorter dobutamine time during DSE constitute a subgroup at risk of future cardiac events after AMI. Also, data were analyzed from a single center, which could decrease the interinstitutional variation when interpreting results of DSE and collecting follow-up data. However, these patients were evaluated in a tertiary referral center, and this takes the advantage of a homogenous reading in a single echocardio-graphic laboratory. In addition, treatment decisions were not made in a fashion blinded to the presence or absence of diabetes, and this might have influenced the outcome of the patients.
It is necessary to integrate all of the information available to the clinician in deciding how to proceed with both diabetic and nondiabetic patients. Our preliminary data suggest that different DSE variables should be considered when assessing the likelihood of future events in diabetic and nondiabetic patients. The observation of dobutamine time, instead of DSE positivity, has a higher prognostic value in diabetics. The only role of DSE positivity in diabetic patients is for predicting future unstable angina; however, the predictive value is not as good as in the nondiabetic patients.