Use of High-Sensitivity Cardiac Troponin for the Exclusion of Inducible Myocardial Ischemia: A Cohort Study.

ABSTRACT

Background: Many patients with coronary artery disease (CAD) are routinely referred for surveillance stress testing despite recommendations against it. Objective: To determine whether low levels of resting high-sensitivity cardiac troponin I (hs-cTnI) can identify persons without inducible myocardial ischemia. Design: Observational study. Setting: A university-affiliated hospital network. Patients Persons with stable CAD 589 in the derivation group and 118 in the validation cohort. Measurements Presence of inducible myocardial ischemia was determined by myocardial perfusion imaging with technetium-99m single-photon emission computed tomography during either treadmill or pharmacologic stress testing. Resting plasma hs-cTnI was measured within 1 week of the stress test, and the negative predictive value (NPV) for inducible ischemia was calculated. The derivation cohort was followed for 3 years for incident cardiovascular death and myocardial infarction. Results: In the derivation cohort, 10 of 101 patients with an hs-cTnI level below 2.5 pg/mL had inducible myocardial ischemia (NPV, 90% [95% CI, 83% to 95%]) and 3 of 101 had inducible ischemia involving at least 10% of the myocardium (NPV, 97% [CI, 92% to 99%]). In the validation cohort, 4 of 32 patients with an hs-cTnI level below 2.5 pg/mL had inducible ischemia (NPV, 88% [CI, 71% to 96%]) and 2 of 32 had ischemia of 10% or greater (NPV, 94% [CI, 79% to 99%]). After a median follow-up of 3 years in the derivation cohort, no adverse events occurred in patients with an hs-cTnI level below 2.5 pg/mL, compared with 33 (7%) cardiovascular deaths or incident myocardial infarctions among those with an hs-cTnI level of 2.5 pg/mL or greater. Limitation: The data may not be applicable to a population without known CAD or to persons with unstable angina, and the modest sample sizes warrant further validation in a larger cohort. Conclusion: Very low hs-cTnI levels may be useful in excluding inducible myocardial ischemia in patients with stable CAD. Primary Funding Source National Institutes of Health.