Prognostic value of cardiac troponin T in patients with both acute and chronic stable congestive heart failure: comparison with atrial natriuretic peptide, brain natriuretic peptide and plasma norepinephrine

Organ protection possibilities in acute heart failure

Unlike chronic heart failure (HF), the treatment for acute HF has not changed over the last decade. The drugs employed have shown their ability to control symptoms but have not achieved organ protection or managed to reduce medium to long-term morbidity and mortality. Advances in our understanding of the pathophysiology of acute HF suggest that treatment should be directed not only towards correcting the haemodynamic disorders and achieving symptomatic relief but also towards preventing organ damage, thereby counteracting myocardial remodelling and cardiac and extracardiac disorders. Compounds that exert vasodilatory and anti-inflammatory action in the acute phase of HF and can stop cell death, thereby boosting repair mechanisms, could have an essential role in organ protection.

Usefulness of High-Sensitive Troponin Elevation After Effort Stress to Unveil Vulnerable Myocardium in Patients With Heart Failure

Elevation of resting high-sensitivity troponin (hs-Tn) holds prognostic value in heart failure (HF), but its pathophysiological meaning is unclear. We aimed to investigate hs-Tn elevation after maximal exercise in patients with systolic HF and its neurohormonal and hemodynamic correlates: 30 patients diagnosed with systolic HF (left ventricular ejection fraction 32 ± 8%, mean ± SD), on guideline-directed medical therapy and not recognized inducible ischemia, underwent maximal cardiopulmonary stress test, with assay of plasma N-terminal proB-type natriuretic peptide (NT-proBNP), norepinephrine (NE), and hs-TnT (hs-TnT) at baseline, peak, and 1 and 4 hours after exercise. Cardiac output (CO) was measured during effort, with a rebreathing technique. The natural logarithm of the ratio between percentage (%) increase in CO and NT-proBNP (ln[CO%/NT-proBNP% increase]) was evaluated, as a noninvasive estimate of Frank-Starling adaptation to effort, with NT-proBNP variation considered as a surrogate of end-diastolic left ventricular pressure variation. Hs-TnT increased during exercise with a 4-hour peak (p = 0.001); 10 patients had hs-TnT increase >20%. Patients with Hs-TnT increase >20% were more symptomatic at rest (p = 0.039) and showed greater NE at peak exercise (p = 0.003) and less ln[CO%/NT-proBNP% increase] (p = 0.034). A lower ln[CO%/NT-proBNP% increase] correlated with greater NE at peak exercise (r = -0.430, p = 0.018). In conclusion, acute troponin elevation after maximal exercise was detected in 1/3 of this series. The association of troponin release with NE, CO, and NT-proBNP changes after effort suggests a pathophysiological link among transient hemodynamic overload, adrenergic activation, and myocardial cell damage, likely identifying a clinical subset at greater risk for HF progression.

High-intensity focused ultrasound ablation of myocardium in vivo and instantaneous biological response

OBJECTIVE

This study aimed to evaluate the instantaneous biological response of canine myocardium in vivo to high-intensity focused ultrasound (HIFU) ablation, and thereby determine the feasibility of this method.

METHODS

Left ventricle myocardium HIFU ablation was performed on six dogs at four levels of HIFU energy (acoustic intensity was 3000 W/cm2 ; ablation durations were 1.2, 2.4, 3.6, and 4.8 sec, respectively). Gross lesion volumes were confirmed and assessed by tetrazolium chloride (TTC) staining, hematoxylin-eosin (HE) staining, and electron microscopy. Global cardiac function and focal wall motion were evaluated by echocardiography. Blood enzymes and cardiac troponin T (CTnT) were tested after ablation. HIFU ablation was repeated on another set of six fresh canine hearts in vitro at the same four energy levels. Focal maximum temperatures were detected both in vivo and in vitro.

RESULTS

Different sizes of ablation via HIFU can be created in beating hearts using controlled energy emission. Focal maximum temperatures varied from 62 ± 4.8 °C to 81 ± 12.9 °C. The lesion sizes were significantly smaller in vivo than in vitro, as verified by TTC and HE staining. Focal wall motion immediately decreased after ablation (P < 0.05), although the ejection fraction (EF) and E/A ratio were unchanged (P > 0.05). Enzymes and CTnT immediately increased.

CONCLUSION

HIFU can be used for the controllable ablation of myocardial tissue, with instantly increased serum markers, decreased regional wall motion, and unaffected left ventricular global function.

Do optimal prognostic thresholds in continuous physiological variables really exist? Analysis of origin of apparent thresholds, with systematic review for peak oxygen consumption, ejection fraction and BNP

Background

Clinicians are sometimes advised to make decisions using thresholds in measured variables, derived from prognostic studies.

Objectives

We studied why there are conflicting apparently-optimal prognostic thresholds, for example in exercise peak oxygen uptake (pVO₂), ejection fraction (EF), and Brain Natriuretic Peptide (BNP) in heart failure (HF).

Data Sources and Eligibility Criteria

Studies testing pVO₂, EF or BNP prognostic thresholds in heart failure, published between 1990 and 2010, listed on Pubmed.

Methods

First, we examined studies testing pVO₂, EF or BNP prognostic thresholds. Second, we created repeated simulations of 1500 patients to identify whether an apparently-optimal prognostic threshold indicates step change in risk.

Results

33 studies (8946 patients) tested a pVO₂ threshold. 18 found it prognostically significant: the actual reported threshold ranged widely (10–18 ml/kg/min) but was overwhelmingly controlled by the individual study population's mean pVO₂ (r = 0.86, p<0.00001). In contrast, the 15 negative publications were testing thresholds 199% further from their means (p = 0.0001). Likewise, of 35 EF studies (10220 patients), the thresholds in the 22 positive reports were strongly determined by study means (r = 0.90, p<0.0001). Similarly, in the 19 positives of 20 BNP studies (9725 patients): r = 0.86 (p<0.0001).

Second, survival simulations always discovered a “most significant” threshold, even when there was definitely no step change in mortality. With linear increase in risk, the apparently-optimal threshold was always near the sample mean (r = 0.99, p<0.001).

Limitations

This study cannot report the best threshold for any of these variables; instead it explains how common clinical research procedures routinely produce false thresholds.

Key Findings

First, shifting (and/or disappearance) of an apparently-optimal prognostic threshold is strongly determined by studies' average pVO₂, EF or BNP. Second, apparently-optimal thresholds always appear, even with no step in prognosis.

Conclusions

Emphatic therapeutic guidance based on thresholds from observational studies may be ill-founded. We should not assume that optimal thresholds, or any thresholds, exist.

Troponin elevation in patients with heart failure: on behalf of the third Universal Definition of Myocardial Infarction Global Task Force: Heart Failure Section

Cardiac troponin testing is commonly performed in patients with heart failure (HF). Despite being strongly linked to spontaneous (Type I) acute myocardial infarction (MI)--a common cause of acute HF syndromes--it is well recognized that concentrations of circulating troponins above the 99 th percentile of a normal population in the context of both acute and chronic HF are highly prevalent, and frequently unrelated to Type I MI. Other mechanism(s) leading to troponin elevation in HF syndromes remain elusive in many cases but prominently includes supply-demand inequity (Type II MI), which may be associated with coronary artery obstruction and endothelial dysfunction, or may occur in the absence of coronary obstruction due to increased oxygen demand related to increased wall tension, anaemia, or other factors provoking subendocardial injury. Non-coronary triggers, such as cellular necrosis, apoptosis, or autophagy in the context of wall stress may explain the troponin release in HF, as can toxic effects of circulating neurohormones, toxins, inflammation, and infiltrative processes, among others. Nonetheless, across a wide spectrum of HF syndromes, when troponin elevation occurs, independent of mechanism, it is strongly predictive of an adverse outcome. Clinicians should be aware of the high frequency of troponin elevation when measuring the marker in patients with HF, should keep in mind the possible causes of this phenomenon, and, independent of a diagnosis of 'acute MI', should recognize the considerable ramifications of troponin elevation in this setting.

Highly sensitive troponin T for risk stratification of acutely destabilized heart failure

BACKGROUND

A highly sensitive assay for troponin T (hsTnT) has been recently developed, which allows for the detection of even minor myocardial necrosis with high precision. It remains unexplored whether hsTnT provides incremental prognostic accuracy beyond conventional (c)TnT in patients with acutely decompensated heart failure (ADHF).

METHODS

A total of 202 consecutive patients admitted with ADHF and without criteria for acute myocardial infarction were studied. Troponin T was measured using the highly sensitive assay and compared with the conventional method. Patients were clinically followed up at a median of 406 days, with a primary outcome measure of all-cause mortality.

RESULTS

The high-sensitive assay detected measurable TnT in 98% of patients vs 56% for cTnT; 81% had an hsTnT above the 99th percentile for a healthy reference population, and it reclassified 60% of those with undetectable cTnT. Both TnT methods predicted the risk of death in adjusted multivariable Cox regression analyses, without a superiority of hsTnT over cTnT in the entire population (area under the curve 0.67 vs 0.71, P = .2). Among patients with a cTnT below 0.03 ng/mL (the lowest cut-point with <10% imprecision; n = 134), solely hsTnT improved the prediction of death over clinical risk factors (relative integrated discrimination improvement +36%, P = .01) and hsTnT above 20 pg/mL identified a significant higher risk of death (hazard ratio 4.7, 95% CI 1.6-13.8, P = .005).

CONCLUSION

Among patients with ADHF, myocardial necrosis (as detected with the hsTnT assay) was nearly ubiquitous. The highly sensitive assay for TnT provides comparable prognostic information to cTnT overall, but among those in whom the cTnT method was less precise or frankly negative, the hsTnT assay provided prognostic information.

Acute heart failure: lessons learned so far

Acute heart failure (AHF) affects nearly every Canadian with heart failure (HF) at least once. Despite several attempts, no medical therapies have been shown to improve the natural history of AHF. In addition, the place of diagnosis of AHF is increasingly made in the outpatient setting. In this view, AHF is a moving target, and from recent registry data and from clinical trials, 5 critical lessons regarding the syndrome of AHF emerge: (1) The period of clinical instability preceding AHF may be much longer than previously thought. (2) Refinement of tools used to aid the early and accurate diagnosis of AHF will impact patient outcomes. (3) Standard supportive care of patients with AHF includes early use of diuretics with frequent reassessment in nearly all patients and supplemental vasodilators and oxygen therapy in selected cases. (4) Patients who survive presentation of AHF continue to suffer high rates of re-presentation, death, and rehospitalization following discharge from either hospital or emergency department. (5) Interventions shown to improve patient outcomes for AHF to date are related to process of care rather than new medications or devices. This report reviews the recent literature regarding the presentation, diagnosis, management, and prognosis of AHF. Areas of future research priority are indicated and guidelines for improving treatment are provided. AHF is an important clinical area that has not been as intensively studied as chronic HF; it presents both important needs and exciting opportunities for research and innovation.

An update on cardiac troponins as circulating biomarkers in heart failure

Circulating troponins and natriuretic peptides are the only biomarkers specifically released from cardiac myocytes that can be determined with robust and sensitive analytical methods, even in healthy subjects. These intracellular proteins are released from reversibly or irreversibly damaged cardiac myocytes into the bloodstream by mechanisms that are not entirely clear. The recent introduction of a new generation of highly sensitive assays of cardiac troponin I or T has not only improved the early diagnosis of acute myocardial infarction but also suggested that there are several causes for troponin release other than acute coronary syndromes. Circulating troponins are elevated in patients with acute or chronic heart failure and are strongly associated with outcome, independently of natriuretic peptides, the benchmark biomarkers in heart failure. In the absence of further experimental evidences, the pathophysiologic basis for the elevation of circulating cardiac troponins in patients with stable chronic heart failure remains speculative.

The role of plasma biomarkers in acute heart failure. Serial changes and independent prognostic value of NT-proBNP and cardiac troponin-T

AIMS

Brain natriuretic peptide (BNP), NT-proBNP and troponins are useful for the assessment of patients with heart failure. Few data exist about their serial changes and their prognostic value in patients with acute heart failure (AHF).

METHODS AND RESULTS

NT-proBNP and troponin-T plasma levels were measured at baseline, after 6, 12, 24, 48 h and at discharge in 116 consecutive patients with AHF and no evidence of acute coronary syndrome. NT-proBNP levels were 4421 pg/mL at baseline, declined after 24 h and reached their nadir at 48 h (2703 pg/mL). Troponin-T was detectable in 48% of patients. During a median follow-up of 184 days, 52 patients died or had a non-fatal cardiovascular hospitalisation. At a multivariable analysis including clinical and echo-Doppler variables, NT-proBNP plasma levels at discharge, detectable troponin-T plasma levels, and NYHA class at discharge were the only independent prognostic factors.

CONCLUSION

In patients with AHF, NT-proBNP levels decline 24 h after the initiation of intravenous therapy and troponin-T is detectable in 48% of cases. NT-proBNP levels at discharge, detectable troponin-T levels, NYHA class and serum sodium have independent prognostic value.

Prognostic value of very low plasma concentrations of troponin T in patients with stable chronic heart failure

BACKGROUND

Circulating cardiac troponin T, a marker of cardiomyocyte injury, predicts adverse outcome in patients with heart failure (HF) but is detectable in only a small fraction of those with chronic stable HF. We assessed the prognostic value of circulating cardiac troponin T in patients with stable chronic HF with a traditional (cTnT) and a new precommercial highly sensitive assay (hsTnT).

METHODS AND RESULTS

Plasma troponin T was measured in 4053 patients with chronic HF enrolled in the Valsartan Heart Failure Trial (Val-HeFT). Troponin T was detectable in 10.4% of the population with the cTnT assay (detection limit < or = 0.01 ng/mL) compared with 92.0% with the new hsTnT assay (< or = 0.001 ng/mL). Patients with cTnT elevation or with hsTnT above the median (0.012 ng/mL) had more severe HF and worse outcome. In Cox proportional hazards models adjusting for clinical risk factors, cTnT was associated with death (780 events; hazard ratio=2.08; 95% confidence interval, 1.72 to 2.52; P<0.0001) and first hospitalization for HF (655 events; hazard ratio=1.55; 95% confidence interval, 1.25 to 1.93; P<0.0001). HsTnT was associated with the risk of death in unadjusted analysis for deciles of concentrations and in multivariable models (hazard ratio=1.05; 95% confidence interval, 1.04 to 1.07 for increments of 0.01 ng/mL; P<0.0001). Addition of hsTnT to well-calibrated models adjusted for clinical risk factors, with or without brain natriuretic peptide, significantly improved prognostic discrimination (C-index, P<0.0001 for both outcomes).

CONCLUSIONS

In this large population of patients with HF, detectable cTnT predicts adverse outcomes in chronic HF. By the highly sensitive assay, troponin T retains a prognostic value at previously undetectable concentrations.

Reference intervals and decision limits for B-type natriuretic peptide (BNP) and its precursor (Nt-proBNP) in the elderly

BACKGROUND

Elderly patients have the highest prevalence of heart failure (HF). The aims of the study were to establish a reference interval for B-type natriuretic peptide (BNP) and (Nt-proBNP) in elderly people, and to identify clinically relevant decision limits based on long-term outcome.

METHODS

Plasma concentrations of BNP and Nt-proBNP were measured from two elderly populations: 218 healthy subjects (mean age 73 years, population I), and 474 patients (mean age 73 years, population II) with symptoms associated with HF. Study population II was followed for 6 years with registration of all cardiovascular mortality.

RESULTS

An association between both BNP and Nt-proBNP concentrations and age was found. The upper limit for the reference intervals in the healthy elderly (population I) was: BNP< or =28 pmol/L (< or =97 ng/L), and Nt-proBNP< or =64 pmol/L (< or =540 ng/L). Based on cardiovascular mortality, decision limits for BNP (approximately 50 pmol/L, approximately 170 ng/L) and Nt-proBNP ( approximately 200 pmol/L, approximately 1700 ng/L) (population II) were determined.

CONCLUSIONS

Besides establishing reference intervals for BNP and Nt-proBNP in an elderly population, a higher clinically relevant decision limit for BNP and Nt-proBNP was identified, indicating additive prognostic information of the peptides on top of measurements by echocardiography. Therefore, both reference intervals and decision limits should be included in clinical practice.

Amino-Terminal Pro–Brain Natriuretic Peptide, Brain Natriuretic Peptide, and Troponin T for Prediction of Mortality in Acute Heart Failure

Background: Combining testing for natriuretic peptides [amino-terminal pro–brain natriuretic peptide (NT-proBNP) and brain natriuretic peptide (BNP)] and cardiac troponin T (cTnT) may help predict mortality in patients with acute heart failure (HF).

Methods: We studied 209 patients with acute HF at an urban academic center and used ROC curves and multivariate analyses to examine the relationship of outcome to natriuretic peptide and cTnT concentrations at presentation.

Results: Higher concentrations of natriuretic peptides and cTnT at presentation were predictors of death at 60 days and 1 year (P &lt;0.001 and P &lt;0.01, respectively, at both time points). Optimal cutoff points for NT-proBNP, BNP, and cTnT for predicting death by 60 days or 1 year were 5562 and 3174 ng/L, 428 and 352 ng/L, and 0.01 and 0.01 μg/L, respectively. Most decedents demonstrated increased concentrations of both natriuretic peptides and cTnT and had a 25% mortality rate at the 60-day time point (P &lt;0.001). Mortality rates were low (&lt;4%) among patients with either no increase or an increase in only 1 marker. Decedents with increases in both a natriuretic peptide and cTnT at presentation had the highest death rate at 1 year (45%, P &lt;0.001). This combination was strongly predictive of death [NT-proBNP plus cTnT: hazard ratio (HR), 7.66; 95% confidence interval (CI), 3.06–17.8; BNP plus cTnT: HR, 6.82; 95% CI, 2.99–16.5].

Conclusions: A dual-marker strategy incorporating a natriuretic peptide and cTnT is superior to either marker alone for estimating short- and longer-term risk in patients with acute HF.

Serum biomarkers for heart failure

The incidence of heart failure has been steadily increasing over the past several decades. High readmission rates in patients with acute decompensated heart failure led to the search for biomarkers that could predict future clinical course and would, in an ideal case, enable monitoring of patients with heart failure and guidance of their therapy. From among several promising markers, the B-type natriuretic peptide and the biologically inactive N-terminal portion of its pro-hormone, NT-proBNP, have become the most frequently used analytes. Other known markers, such as atrial natriuretic peptide and endothelin-1, are currently used for research purposes. The development of additional biomarkers will be an important step from improving diagnosis and treatment of patients with chronic and acute decompensated heart failure.

Cardioprotection: a new paradigm in the management of acute heart failure syndromes

The management of acute heart failure syndromes (AHFS) focuses primarily on improving hemodynamic function and alleviating symptoms. Emerging evidence has raised the possibility that patients with AHFS may be susceptible to progressive myocardial failure because of the accelerated loss of cardiac myocytes. Although there are circumstantial data to suggest that the choice of therapeutic agent may affect long-term outcomes in such patients, the responsible mechanism is not known. Activation of mitochondrial adenosine triphosphate-dependent potassium (K(ATP)) channels in cardiac myocytes is a potent cardioprotective mechanism. We studied cardiac myocytes in culture to determine whether levosimendan can protect against apoptotic cell death in response to oxidative stress, a stimulus that appears to mediate myocyte loss in response to hemodynamic overload and beta-adrenergic stimulation, conditions commonly encountered in acute HF. Levosimendan, at concentrations below the therapeutic range in humans, protected myocytes from hydrogen peroxide-induced apoptosis. This effect was prevented by K(ATP) channel inhibitors. The demonstration that levosimendan can oppose myocyte apoptosis via the activation of mitochondrial K(ATP) channels provides a potential mechanism by which this agent might protect cardiac myocytes during episodes of acute HF. Although the alleviation of symptoms should remain an important goal of therapy in acute HF, a therapeutic approach that includes a cardioprotective strategy may be able to exert a clinically meaningful benefit on disease progression. This speculation, if proved true, would mandate a fundamental paradigm shift in the acute management of acute HF.