What is the interpretation of a stress test showing nonspecific ST-T wave changes and symptoms of shortness of breath and dizziness during exercise?

Stress Test Interpretation: Equivocal for Ischemia with Concerning Features

This stress echocardiogram shows an equivocal result for ischemia due to baseline nonspecific ST-T wave abnormalities that render the ECG component non-diagnostic, though the reassuring finding is no stress-induced wall motion abnormalities on echocardiography and preserved left ventricular function. However, the patient's symptoms of severe dyspnea and dizziness during exercise, combined with the ECG pattern showing ST-T changes that initially worsened then paradoxically normalized at peak stress, warrant further evaluation to definitively exclude obstructive coronary artery disease.

Key Findings Analysis

ECG Component - Non-Diagnostic

• The stress ECG is equivocal and non-diagnostic because baseline diffuse nonspecific ST-T wave abnormalities preclude accurate interpretation of exercise-induced changes 1.
• The unusual pattern of ST-T changes—worsening early in exercise, then normalizing completely at peak stress and early recovery before returning in recovery—is atypical and concerning, as normalization of ST-segment abnormalities can represent a "cancellation effect" from severe transmural ischemia 1.
• Patients with nonspecific ST-T wave changes at rest are considered to have non-diagnostic stress ECG responses, and those with intermediate to high likelihood of coronary disease should be assessed with alternative imaging modalities 1.

Echocardiographic Component - Reassuring

• No stress-induced segmental wall motion abnormalities were detected, which is the primary diagnostic endpoint and provides reassurance against significant obstructive coronary disease 1.
• Normal global left ventricular systolic function at baseline with appropriate augmentation during stress suggests adequate cardiac reserve.
• Left ventricular ejection fraction remained preserved, and LV chamber size appropriately decreased with stress.

Symptomatic Response - Concerning

• Severe dyspnea and moderate nausea during exercise are significant symptoms that should not be dismissed, even when imaging is negative 1.
• Exercise-induced symptoms in the context of equivocal testing should classify this patient as symptomatic, which has prognostic implications 1.
• The combination of dizziness and dyspnea could represent inadequate cardiac output augmentation or other cardiac pathology not detected by wall motion analysis alone.

Clinical Implications and Recommendations

Immediate Management

• The patient should be considered symptomatic based on exercise-provoked symptoms, regardless of the negative wall motion findings 1.
• Given the history of atrial flutter (the indication for testing), correlation with rhythm during symptoms is essential—was the patient in normal sinus rhythm or did arrhythmia contribute to symptoms?
• The appropriate blood pressure response and achievement of target heart rate suggest adequate chronotropic competence, making rate-related ischemia less likely.

Need for Additional Testing

• Myocardial perfusion SPECT imaging is recommended as the next diagnostic step, since patients with nonspecific ST-T wave changes and intermediate to high likelihood of coronary disease can be effectively assessed with nuclear imaging 1.
• Pharmacologic stress perfusion imaging may be preferable to repeat exercise testing given the non-diagnostic ECG findings 1.
• The diagnostic sensitivity of stress echocardiography ranges from 70-85% for exercise protocols, meaning a false negative rate of 15-30% exists even with adequate imaging 1.

Risk Stratification Considerations

• The functional capacity achieved was appropriate, which is generally a favorable prognostic indicator 1, 2.
• Normal heart rate response and blood pressure response to exercise are reassuring features 1, 2.
• However, isolated nonspecific ST-T wave abnormalities, even in asymptomatic patients, have been associated with increased cardiovascular and all-cause mortality in population studies 3.

Common Pitfalls to Avoid

Do Not Dismiss Symptoms

• Exercise-induced symptoms should never be attributed solely to deconditioning when cardiac pathology remains incompletely evaluated, particularly in a patient with known atrial flutter 1.
• The normalization of ST-T changes at peak stress is an unusual finding that could represent severe ischemia with "cancellation effects" rather than a benign response 1, 4.

Recognize Test Limitations

• Stress echocardiography has inherent limitations in detecting non-flow-limiting coronary disease or microvascular dysfunction that could still cause symptoms 1.
• The inability to obtain post-stress diastolic evaluation due to E/a fusion is a technical limitation that prevents assessment of diastolic dysfunction, which could contribute to dyspnea.
• Wall motion abnormalities may not develop if ischemia is subendocardial or if collateral circulation is adequate 1.

Consider Alternative Diagnoses

• Nonspecific ST-T wave changes can be associated with left ventricular hypertrophy, hypertension, or early cardiomyopathy 1, 5, 6.
• The baseline echocardiogram showed normal LV size and function, but serial monitoring may be warranted as T-wave abnormalities can precede structural changes in cardiomyopathy 5, 6.
• In patients with atrial flutter, rate-related symptoms or inadequate rate control during exercise could explain dyspnea independent of ischemia.

Recommended Clinical Pathway

Proceed with myocardial perfusion SPECT imaging (preferably pharmacologic stress) to definitively assess for inducible ischemia, given the equivocal ECG findings and symptomatic response 1. If perfusion imaging is normal, consider evaluation for non-ischemic causes of symptoms including diastolic dysfunction, valvular disease, or arrhythmia-related symptoms. Ensure adequate rate control of atrial flutter and consider ambulatory rhythm monitoring during typical activities to correlate symptoms with cardiac rhythm. Serial clinical follow-up is essential even if additional testing is negative, as nonspecific ST-T changes may represent early cardiac pathology 5, 6, 3.