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Prognostic Value of Cardiac Troponin T in Patients With Moderate to Severe Heart Failure Scheduled for Cardiac Resynchronization Therapy
Study Questions:
Does highly-sensitive troponin T (hs-TnT) predict response to cardiac resynchronization therapy (CRT) and cardiovascular events?
Methods:
This was an open-label observational study of 81 consecutive patients undergoing CRT implant according to current guidelines. Both AV and VV optimizations were conducted after implant. Echocardiograms and cardiac magnetic resonance imaging (MRI) were obtained at baseline. Patient New York Heart Association (NYHA) class, cardiopulmonary stress testing, and blood samples (hs-TnT and N-terminal pro–B-type natriuretic peptide [NT-proBNP]) were obtained at baseline and at 3, 6, and 12 months by personnel blinded to hs-TnT concentrations. The primary outcome of interest was response to CRT based on baseline hs-TnT concentration (dichotomized at 15 ng/L). Responders were defined as having either: 1) a reduction in left ventricular systolic volume (LVSV) ≥10%, 2) an increase in LV ejection fraction of ≥6%, or 3) a combined reduction in LVSV with clinical improvement (NYHA class, peak oxygen consumption). Response to CRT and freedom from cardiovascular death or transplant was calculated using Cox regression and Kaplan-Meier estimates.
Results:
Baseline mean ± standard deviation patient age was 64 ± 10 years, 19% were female, and 48% had an ischemic cardiomyopathy. The mean QRS was 175 ± 22 ms. The baseline hs-TnT was ≥15 ng/L in 58% (n = 47). Elevated hs-TnT was associated with male sex, ischemic cardiomyopathy, use of statins, higher baseline NT-proBNP levels, more scar on cardiac MRI, lower LV ejection fractions, and higher serum creatinine. Following CRT, patients with a baseline hs-TnT <15 ng/L had greater reductions in LV diameters and greater increases in LV ejection fractions. As such, more patients with an hs-TnT <15 ng/L met the definition of “response to CRT” based on LVEF and LVSV criteria than those with higher hs-TnT values (both p < 0.05). Patients who responded to CRT were more likely to experience a reduction in hs-TnT levels at follow-up, but only 13% of patients had normalization of hs-TnT values. After 46 ± 6 months of follow-up, 7 patients underwent transplant and 13 died of cardiovascular causes. Event-free survival was associated with female sex, lower NT-BNPs and hs-TnT levels, and smaller baseline LV dimensions and volumes. Baseline hs-TnT level was the only multivariable predictor of event-free survival (hazard ratio, 4.2; 95% confidence interval, 1.01-17.2).
Conclusions:
The authors concluded that higher baseline hs-TnT is associated with worse CRT response and poor survival.
Perspective:
Despite extensive study, identifying responders to CRT remains difficult. The authors present data suggesting that pre-CRT levels of hs-TnT may be predictive of CRT response. The link between CRT response and baseline hs-TnT levels is not immediately intuitive. CRT aims to improve ventricular synchrony through electrical modulation of LV contraction. The authors explain that elevated hs-TnT levels may suggest the presence of baseline ischemia, apoptosis, or increased wall stress (via higher BNP levels). Thus, baseline hs-TnT may identify heart failure patients with ‘too any strikes against them.’ Study limitations include a very low rate of evidence-based medicine use (<42% were on beta-blockers) and small sample size to allow for adequate multivariable regression analysis.
Keywords: Follow-Up Studies, Biomarkers, Cardiomyopathies, Heart Failure, Troponin T, New York, Magnetic Resonance Imaging, Cardiac Resynchronization Therapy, Echocardiography
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