High-Sensitivity Troponins Associated With Exercise-Induced Myocardial Ischemia

Deborah Brauser

December 29, 2015

BASEL, SWITZERLAND — Levels of high-sensitivity (hs) cardiac troponin I may help clinicians detect exercise-induced myocardial ischemia in patients suspected of having the condition, according to new research[1].

In the 800-person cohort study conducted in Switzerland, those with exercise-induced ischemia, as measured by perfusion single-photon emission computed tomography (SPECT) and coronary angiography, had significantly higher concentrations of hs-troponin I before, during, and after stress testing vs those without the ischemia (P<0.001 for all comparisons).

In addition, troponin levels before and after stress testing plus "clinical judgment" were significant predictors of the ischemia.

However, "exercise-induced changes during exercise did not seem useful, as they were small and similar in patients with or without myocardial ischemia," write Dr Gino Lee (Cardiovascular Research Institute Basel, Switzerland) and colleagues.

"Our findings should help to further develop the concept of using biomarkers in conjunction with clinical assessment and the exercise ECG in the evaluation of patients presenting with symptoms suggestive of stable coronary artery disease," they write, adding that this concept may appeal to internists and general practitioners in addition to cardiologists.

The results were published online November 20, 2015 in the American Heart Journal.

BASEL VIII Participants

The researchers evaluated 819 participants (69% men; mean age 65 years) from the Biomarkers and ECG Signals in Exercise-Induced Myocardial Ischemia (BASEL VIII) study. All were enrolled between January 2010 and July 2012 and were referred for rest/bicycle myocardial perfusion SPECT.

A visual analog scale was used by the treating cardiologist before and after stress testing "to quantify clinical judgment" for the condition, with the final judgment coming from the perfusion SPECT and angiography.

The hs-troponin I levels from blood samples were measured prior to stress testing, right after peak stress, and 2 hours posttest.

A total of 34% of participants were found to have exercise-induced myocardial ischemia. At baseline, the mean hs-cardiac troponin I level was 4.2 ng/L in these patients vs 2.5 ng/L in those without the condition. Immediately after stress testing, the levels were 4.6 vs 2.8 ng/L, respectively, and 2-hour posttest levels were 5.2 vs 3.3 ng/L, respectively.

"Considerable Potential"

Prior to stress testing, clinical judgment alone had an area under the curve (AUC) accuracy score of 0.67 for the ischemia diagnosis. The score increased significantly to 0.76 when combined with baseline levels of the troponins (P<0.001).

After stress testing, diagnostic accuracy was increased when clinical judgment (alone, AUC 0.70) was combined with baseline troponin levels (AUC 0.77) or at either poststress test time point (AUC 0.76–0.77; P<0.001 for all comparisons). However, clinical judgment plus changes in hs-troponin levels from baseline to stress test did not significantly increase diagnostic accuracy (AUC 0.71).

Overall, troponin concentrations "provide substantial value to clinical judgment including exercise ECG regarding presence of myocardial ischemia," write the researchers.

In a further analysis, 151 of participants had severe CAD (>75% stenosis). These patients also had significantly higher hs-troponin I levels at all time points vs those without severe CAD (P<0.002–0.005). But, again, changes in troponin levels were not significantly different between the two groups.

The investigators note that more studies are needed to refine the strategy, including the possibility of combining the assessment of hs-troponin I levels with natriuretic peptides. In addition, they write that although cardiac imaging will remain important for these patients, "simple, inexpensive, and widely available diagnostic tools such as blood tests . . . have considerable potential."

Lee reports no relevant financial relationships. Disclosures for the coauthors are listed in the article.


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