Short-term variability of heart rate turbulence in chronic heart failure

Background

Heart rate turbulence (HRT) is associated with risk in chronic heart failure (CHF). The objective of this study was to assess the short-term variability of HRT and to compare the diagnostic yield of 7-day (7DH) versus 24-hour (1DH) Holter monitoring for calculating HRT in a CHF population.

Methods and Results

Forty-nine consecutive patients with CHF were studied. At inclusion, 7DH was performed to evaluate the variability of HRT parameters. For categorized analyses, turbulence onset (TO) ≥0% and turbulence slope (TS) ≤2.5 ms/RR were defined as abnormal, and patients were classified into subgroups based on the number of abnormal HRT parameters.The cumulative percentage of patients with calculable HRT increased from 69.4% with 1DH to 93.9% with 7DH. The intraclass correlation coefficients across the 7-day monitoring were 0.81 (95% confidence interval [CI] 0.70–0.89) for TO and 0.90 (95% CI 0.84–0.95) for TS. When comparing 2 randomly selected days, TO and TS values were similar (P > .1) and showed a strong correlation (TO: r = 0.79; TS: r = 0.84: P < .001). Bland-Altman plots showed a mean difference of 0.31% (95% CI −0.07 to 0.70) for TO and 0.44 ms/RR (95% CI −1.37 to 0.48) for TS. In contrast, categorized analyses showed that up to 16% of patients changed their HRT subgroup score from day 1 to day 2 of comparison.

Conclusions

In this population, 7DH significantly increased the percentage of patients with calculable HRT parameters. The short-term variability of the quantitative HRT values was good, but when patients were categorized into the established HRT subgroups, the concordance was suboptimal.     

Recommendations for Institutions Transitioning to High-Sensitivity Troponin Testing: JACC Scientific Expert Panel

High-sensitivity cardiac troponin (hs-cTn) I or T methods have been in use in certain regions for years but are now increasingly globally adopted, including in the United States. Accordingly, inevitable challenges are created for institutions transitioning from conventional cardiac troponin (cTn) assays. hs-cTn assays have higher analytic precision at lower concentrations, yielding greater clinical sensitivity for myocardial injury and allowing accurate recognition of small changes in troponin concentration (rise or fall) within a short time frame. Although much of the knowledge regarding troponin biology that was applicable with older troponin assays still holds true, considerable education regarding the differences between conventional cTn and hs-cTn is needed before medical systems convert to the newer methods. This includes a basic understanding of how hs-cTn testing differs from conventional cTn testing and how it is best deployed in different settings, such as the emergency department and inpatient services. This Expert Panel will review important concepts for institutional transition to hs-cTn methodology, providing recommendations useful for education before implementation.     

Cardiac troponin T concentrations above the 99th percentile value as measured by a new high-sensitivity assay predict long-term prognosis in patients with acute coronary syndromes undergoing routine early invasive strategy

Objective

A recently developed immunoassay for high-sensitivity measurement of cardiac troponin T (hsTnT) allows measurement at the 99th percentile for a normal population with an assay imprecision <10%. It is unclear whether such a low cutpoint (14?ng/L) is helpful for long-term risk stratification of patients with an acute coronary syndrome (ACS) undergoing routine early invasive strategy.

Patients and main outcome measures

Consecutive patients with ACS admitted to a chest pain unit were studied. The usefulness of hsTnT for early diagnosis of myocardial infarction (MI) and prediction of all-cause death or death/MI over a median of 271?days following presentation was compared against the fourth generation cTnT at the 99th percentile cutpoint.

Results

Of 1,384 patients with ACS enrolled, 47.8% had non-ST-segment elevation MI (NSTEMI), 26.4% unstable angina, 21.8% STEMI and 4% had non-ACS. Adjusted risk for all-cause death [adjusted HR 8.26 (95%CI: 1.13?C66.33), p?=?0.038] and death/MI [adjusted HR 2.71 (95% CI: 1.15?C6.38), p?=?0.023] were significantly higher with hsTnT above the 99th percentile. In particular, among patients with a standard fourth generation cTnT result below the 99th percentile cutoff (0.01?ng/mL), hsTnT improved risk assessment. Mortality risk associated with an elevated hsTnT was present across the spectrum of ACS, as well as in conditions with hsTnT elevations not related to ACS.

Conclusion

hsTnT at the 99th percentile cutoff is useful for the diagnostic evaluation of patients with ACS, and provides strong and independent predictive power for adverse long-term outcomes even after early invasive strategy.