Noninvasive detection of risk for emotion-provoked myocardial ischemia

Abstract

Objectives: To test an easily administered, noninvasive technology to identify vulnerability to mental stress ischemia.

Background: Myocardial ischemia provoked by emotional stress (MSI) in patients with stable coronary artery disease (CAD) predicts major adverse cardiac events. A clinically useful tool to risk stratify patients on this factor is not available.

Methods: Patients with documented CAD (n = 68) underwent single photon emission CT myocardial perfusion imaging concurrent with pulse wave amplitude assessment by peripheral arterial tonometry (PAT) during a mental stress protocol of sequential rest and anger stress periods. Heart rate and blood pressure were assessed, and blood was drawn for catecholamine assay, during rest and stress. MSI was defined by the presence of a new perfusion defect during anger stress (n = 26) and the ratio of stress to rest PAT response was calculated.

Results: Patients with MSI had a significantly lower PAT ratio than those without MSI (0.76 +/- 0.04 versus 0.91 +/- 0.05, p = .03). An ROC curve for optimum sensitivity/specificity of PAT ratio as an index of MSI produced a sensitivity of 0.62 and a specificity of 0.63. Among patients taking angiotensin converting enzyme (ACE) inhibitors, the sensitivity and specificity of the test increased to 0.86 and 0.73, respectively; 90% of patients without MSI were correctly identified.

Conclusions: PAT in concert with ACE inhibition may provide a useful approach to assess risk for MSI. Future studies should help determine how best to utilize this approach for risk assessment in the clinical setting.

Figure 1

Examples of PWA traces as a function of time. Numeral 0 in each trace indicates the relaxation period and numeral 1 indicates the beginning of the mental stress task. A. Trace resulting in an abnormal PAT ratio, with relative vasoconstriction during mental stress. B. Trace resulting in a normal PAT ratio, with relative vasodilatation during mental stress.

Figure 2

ROC curve for PAT ratio predicting mental stress ischemia. The AUC is 0.613 (SE, 0.065, one-sided P = 0.04), indicating that PAT ratio has diagnostic utility in predicting MSI.

Figure 3

ROC curves for PAT ratio predicting mental stress ischemia for those who were taking ACE inhibitors versus those who were not. The AUCs are 0.768 (SE = 0.081, one-sided P < 0.001) when ACE inhibitors are present and 0.408 (SE = 0.095, one-sided P = 0.17) when they are absent (P = 0.004 for difference in AUC). PAT ratio performs significantly better as a test for MSI in those who are taking ACE inhibitors.