From the Guidelines
Myocardial ischemia on a stress test is most accurately indicated by ST-segment depression of at least 1 mm that is horizontal or downsloping, occurring during exercise or recovery, as well as new or worsening wall motion abnormalities during stress echocardiography, and reversible perfusion defects on nuclear imaging stress tests. When interpreting stress test results, it's crucial to consider various signs that may indicate myocardial ischemia. These include:
- ST-segment depression of at least 1 mm that is horizontal or downsloping, occurring during exercise or recovery 1
- T-wave inversions
- ST-segment elevation in leads without Q waves
- Development of chest pain or angina-equivalent symptoms during testing
- Exercise-induced arrhythmias, particularly ventricular arrhythmias
- A drop in blood pressure or failure of blood pressure to rise appropriately with increasing workload (chronotropic incompetence), which may indicate severe coronary disease
- Reversible perfusion defects (areas that show decreased tracer uptake during stress but normalize at rest) on nuclear imaging stress tests, which strongly suggest ischemia 1
- New or worsening wall motion abnormalities during stress indicate ischemic myocardium on stress echocardiography
The choice of stress test modality depends on the patient's ability to exercise and the presence of known coronary artery disease (CAD) 1. According to the 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR guideline, for intermediate-risk patients with acute chest pain and no known CAD, either exercise ECG, stress echocardiography, stress PET/SPECT MPI, or stress CMR is useful for the diagnosis of myocardial ischemia 1.
In clinical practice, the most recent and highest quality study should guide decision-making. Therefore, the 2021 guideline 1 provides the most up-to-date recommendations for stress testing in patients with suspected myocardial ischemia. By considering these signs and guidelines, healthcare providers can accurately diagnose and manage myocardial ischemia, ultimately improving patient outcomes in terms of morbidity, mortality, and quality of life.
From the FDA Drug Label
Myocardial uptake of the radiopharmaceutical is proportional to CBF. Because regadenoson increases blood flow in normal coronary arteries with little or no increase in stenotic arteries, regadenoson causes relatively less uptake of the radiopharmaceutical in vascular territories supplied by stenotic arteries MPI intensity after regadenoson administration is therefore greater in areas perfused by normal relative to stenosed arteries.
The signs that indicate myocardial ischemia on a stress test are areas with relatively less uptake of the radiopharmaceutical, which suggests reduced blood flow in those areas, typically supplied by stenotic arteries. Key points to look for include:
- Reversible defects in MPI images, which may indicate ischemic areas
- Reduced MPI intensity in areas supplied by stenotic arteries compared to normal arteries
- Changes in heart rate and blood pressure after regadenoson administration, which may be associated with ischemia 2
From the Research
Signs of Myocardial Ischemia on a Stress Test
- ST segment depression (STD) is a standard electrocardiographic sign of myocardial ischemia 3
- ST segment elevation in the inferior leads can be associated with high lateral STD, which should be recognized as a reciprocal change rather than a sign of myocardial ischemia on its own 3
- STD in the anterior leads appears to be a sign of myocardial ischemia 3
- Reversible perfusion abnormalities can indicate ischemia 3
Choosing the Appropriate Stress Test
- The choice of stress test is important in the workup of patients with possible myocardial ischemia 4
- Multiple imaging modalities are available to evaluate patients suspected of having coronary ischemia, including stress electrocardiography, stress echocardiography, and single-photon emission computed tomography myocardial perfusion imaging 5
Importance of Objective Evidence of Myocardial Ischemia
- Objective evidence of myocardial ischemia is mandatory if lesion severity is questionable 6
- Physiological assessment of myocardial ischemia is most useful in patients with intermediate coronary artery stenosis 6
- Early invasive coronary angiography can be associated with lower mortality and higher rates of coronary revascularization in acute heart failure patients with possible ischemia 7