Prognostic role of highly sensitive cardiac troponin I in patients with systolic heart failure

Congestive Heart Failure

Prognostic role of highly sensitive cardiac troponin I in patients with systolic heart failure Takayoshi Tsutamoto, MD, Chiho Kawahara, MD, Keizo Nishiyama, MD, Masayuki Yamaji, MD, Masanori Fujii, MD, Takashi Yamamoto, MD, and Minoru Horie, MD Otsu, Japan

Background Cardiac troponin T (cTnT) and cardiac troponin I (cTnI) are useful biomarkers in patients with chronic heart failure (CHF). However, the clinical use has limitations due to the low sensitivity of a conventional commercial assay system. Recently, a high sensitive-cTnI (hs-cTnI) commercial assay has become available. Methods To compare the prognostic value of cTnT and hs-cTnI, we measured hemodynamic parameters and serum levels of cTnT, hs-cTnI and N-terminal pro–brain natriuretic peptide (NT-proBNP)in 258 consecutive CHF patients and then followed these patients for a mean period of 2.6 years. In both assays of cTnT and hs-cTnI, the lowest concentration at which the coeffi cient of variation was ≤10% were 0.03 ng/mL, respectively. Therefore, in the present study, an elevated cTnT or cTnI test was defined as a level of ≥0.03 ng/mL. Results During long-term follow up, there were 20 cardiac deaths. In 258 CHF patients, serum cTnT were elevated (≥0.03 ng/mL) in 32 patients (12%) and serum hs-cTnI was elevated (≥0.03 ng/mL) in 112 patients (43%). On stepwise multivariate analyses, high plasma NT-proBNP (≥627 pg/mL, P = .0063) and hs-cTnI (≥0.03 ng/mL) (P = .016) were independent significant prognostic predictors but cTnT (≥0.03 ng/mL) was not. The hazard ratio for mortality of patients with high plasma NT-proBNP (≥627 pg/mL) and hs-cTnI (≥0.03 ng/mL) was 5.74 (95% CI, 2.33-14.28, P b .0001) compared to that of those with low NT-proBNP (b627 pg/mL) or hs-cTnI (b0.03 ng/mL). Conclusions These findings indicate that a high plasma concentration of hs-cTnI is an independent and useful prognostic predictor in patients with CHF. (Am Heart J 2010;159:63-7.)

Plasma levels of brain natriuretic peptide (BNP) and Nterminal pro-BNP (NT-proBNP) are well-established biomarkers not only in patients with CHF1-4 and acute coronary syndrome but also in the general population. Cardiac troponins such as cardiac troponin T (cTnT) and cardiac troponin I (cTnI) are also important and useful biomarkers in these patients.5-10 However, the clinical use of serum levels of cTnT and cTnI has limitations due to the low sensitivity of the assay system compared with that of BNP or NT-proBNP.11 Indeed, as recommended in the recent guideline for biomarker evaluation, optimal precision (CV at the 99th percentile upper reference limit for assay should be defined as ≤10%) and better precision allows for more sensitive assays.12 Recently, a highly sensitive commercial assay of cTnI has become available. We evaluated the prognostic value of cTnT using a

conventional commercial assay, a high sensitive-cTnI (hs-cTnI) and NT-proBNP in the same population of CHF.

Methods Patients The subjects were 258 consecutive symptomatic CHF patients (left ventricular ejection fraction [LVEF] b45%) as previously reported.13,14 Patients with recent (within 2 months) ischemic heart disease, those on dialysis therapy, and patients with high creatinine (≥2.5 mg/dL) were excluded. Informed consent was obtained from all patients before participation in the study, and the protocol was approved by the Human Investigations Committee of our institution. New York Heart Association (NYHA) functional class was evaluated on the day of cardiac catheterization.

Study protocol From the Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan. Submitted August 22, 2009; accepted October 16, 2009. Reprint requests: Takayoshi Tsutamoto, MD, Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Tsukinowa, Seta, Otsu 520-2192, Japan. E-mail: [email protected] 0002-8703/$ - see front matter © 2010, Mosby, Inc. All rights reserved. doi:10.1016/j.ahj.2009.10.022

All patients were premedicated with an oral dose of diazepam (5 mg) and rested in bed in a supine position for at least 20 minutes. Left-sided cardiac catheterization was performed and blood pressure was measured. Heart rate was monitored by electrocardiography. Blood samples for measuring serum levels of cTnT and hs-cTnI and plasma NT-proBNP levels were collected from the aortic root. Left ventriculography was performed using contrast medium or radioisotope before or at

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least one week after hemodynamic measurements and blood sampling. Estimated glomerular filtration rate (eGFR) was used as an indicator of renal function based on the abbreviated Modification of Diet in Renal Disease study formula.15

Table I. Hemodynamic and neurohumoral variables in 258 patients with systolic heart failure according to survival Variables

Measurement of biomarkers Samples for the assay of NT-proBNP concentrations were transferred to chilled disposable tubes containing aprotinin (500 kallikrein inactivator units/mL). The blood samples were immediately placed on ice and centrifuged at 4°C, and the plasma was frozen in aliquots and stored at −30°C until assay. Plasma levels of NT-proBNP were measured using the Elecsys proBNP sandwich immunoassay (Roche Diagnostics, Mannheim, Germany), as previously reported.16 We measured serum concentrations of cTnT using a commercial kit (fourth-generation Elecsys Troponin T immunoassay; Roche Diagnostics, Switzerland). In this assay, the lower limit of detection is 0.01 ng/mL, and the lowest concentration at which the CV was b10% was 0.03 ng/mL,17 while the intraassay and interassay CV were 8.9% (n = 4) and 9.8 % (n = 4), respectively, in a sample with a cTnT concentration of 0.03 ng/mL, as previously reported. In the present study, a positive cTnT test was defined as a cTnT level of ≥0.03 ng/mL. We measured serum cTnI using a high sensitive cTnI assay (Centaur TnI-Ultra/Siemens Medical Solution Diagnostics, NY). In this assay, the lower limit of detection is 0.006 ng/mL, and the lowest concentration at which the CV was b10% was 0.03 ng/mL,17 while the intraassay and interassay CVs were 3.5 % (n = 4) and 4.2 % (n = 4), respectively, in a sample with a cTnI concentration of 0.03 ng/mL. In the present study, a positive hs-cTnI test was defined as a cTnT level of ≥0.03 ng/mL.

Statistical analysis All results are expressed as the mean ± S.D. A χ2 test was used to determine differences between groups. Univariate analyses were performed using Student t test. Differences in mean levels of NTproBNP between the 2 groups were tested by Mann-Whitney U test for unpaired value with 2-tailed P values of b.05. Log hs-cTnI and log NT-proBNP was used for correlations and regression models in patients in whom hs-cTnI ≥0.03 ng/mL. Multivariable Cox proportional hazard analyses were performed as stepwise regressions with backward elimination. Kaplan-Meier analysis was performed on the cumulative rates of survival stratified into 2 groups based on cut-off values (0.03 ng/mL) for cTnT and hscTnI. Kaplan-Meier analysis was also performed on the cumulative rates of survival stratified into two groups based on the cut-off value of the plasma NT-proBNP, and the cutoff value of cTnI (0.03 ng/mL) and the differences between survival curves were analyzed by log-rank test. The cutoff level of NT-proBNP (627 pg/ mL) for predicting mortality was determined by the findings of a previous study.14 A value of P b .05 was considered significant.

Results Patient characteristics Table I summarizes patient characteristics according to survival. During a median follow-up of 2.6 years, 20 patients died of cardiac-related causes. Of 258 CHF patients, serum cTnT concentrations were elevated (≥0.03 ng/mL) in 32 patients (12%) and serum hs-

Age (y) Sex (male/female) Ischemic heart disease, n (%) NYHA class I or II/III or IV eGFR (mL/min/1.73 m2) NT-proBNP (pg/mL) cTnT ≥0.03 (ng/mL), n (%) hs-cTnI ≥0.03 (ng/mL), n (%) HR (beat/min) MBP (mmHg) LVEDP (mmHg) LVEF (%) Treatments Loop diuretics, n (%) Spironolactone, n (%) ACEI or ARB, n (%) β-Blockers, n (%)

All patients Survivors Nonsurvivors (n = 258) (n = 238) (n = 20) P value 63.8 ± 12.8 63.9 ± 12 203/55 187/16 159 (62) 149 (63)

218/34 72 ± 36

204/34 73 ± 37

522 490 (215-1240) (210-123) 34 (13%) 29 (12%)

62.7 ± 21 16/4 10 (50)

.679 .999 .338

14/6 61 ± 29

.005 .098 .167

1604 (683-4078) 5 (25%)

.0011 .157

112 (43%)

97 (41%)

15 (75%)

.0041

72.4 ± 17 85.3 ± 15.3 12.0 ± 6.8 33.9 ± 7.8

71.8 ± 16 85.7 ± 15 11.9 ± 6.6 34.4 ± 7.7

78.4 ± 22 72.4 ± 16 12.8 ± 8.7 28.9 ± 7.1

.100 .0005 .602 .0024

123 (48)

108 (42)

15 (75)

.017

80 (31)

71 (30)

9 (45)

.269

196 (76)

181 (76)

15 (75)

.999

146 (57)

132 (55)

13 (65)

.245

ACEI, Angiotensin-converting enzyme inhibitor; ARB, angiotensin receptor blockers; AO, aortic root; HR, hear rate; LVEDP, left ventricular end-diastolic pressure; MBP, mean blood pressure.

cTnI concentrations were elevated (≥0.03 ng/mL) in 112 patients (43%). Kaplan-Meier curves for cardiac death by cTnT and hs-cTnI are shown in Figure 1. There was a significant correlation between log cTnT and log hs-cTnI in 32 patients in whom both cardiac troponins were elevated (≥0.03 ng/mL) (Figure 2) (r = 0.664, P b .0001). There was a significant correlation between log NTproBNP and log hs-cTnI in 112 patients who were hs-cTnI (≥0.03 ng/mL) (r = 0.344, P = .0002) (Figure 3). There was no significant correlation between eGFR and serum hs-cTnI (r = −0.141, P = .139) in these patients. There was no difference in patients who were cTnT positive (≥0.03 ng/mL) between survivors and nonsurvivors (P = .082), while there was a significant difference in patients who were hs-cTnI positive (≥0.03 ng/mL) between survivors and nonsurvivors (P = .0011). There was no difference in the treatment for CHF between two groups.

Univariate and multivariable predictors of mortality–comparison of cTnT, hs-cTnI, NT-proBNP, and hemodynamic parameters Nine variables including biomarkers and hemodynamic variables were analyzed using univariate and stepwise

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Figure 1

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Figure 3

Correlation between plasma NT-proBNP and serum hs-cTnI in patients with chronic heart failure.

Table II. Univariate and multivariate predictors of mortality— comparison of NT-proBNP and cardiac troponin Variables

Kaplan-Meier survival curves according to the cut-off values for cTnT (0.03 ng/mL) and hs-cTnI (0.03ng/mL) in patients with chronic heart failure.

Figure 2

Age (y) NYHA class (III/IV = 1, I/II = 0) Ischemic heart disease (yes = 1, no = 0) LVEDP (mm Hg) LVEF (%) eGFR (mL/min/1.73 m2) NT-proBNP ≥627 (pg/mL) cTnT ≥0.03 (ng/mL) hs-cTnI ≥0.03 (ng/mL)

Univariate χ2

P

0.0002 3.876

.916 .042

1.916

.166

0.350 8.094 0.586 13.355

.554 .004 .449 .0003

5.425 10.928

.0199 .0009

Multivariate χ2 HR (95%CI) P

7.448 4.7 (1.5-14.4)

.0063

5.765 3.55 (1.26-10)

.016

Abbreviations are listed in Table I.

compared to those with NT-proBNP (b627 pg/mL) or cTnI (b0.03 ng/mL) for mortality (Figure 4).

Correlation between serum hs-cTnI and cTnT in patients with chronic heart failure.

multivariable Cox proportional hazards regression analyses (Table II). The hazard ratio of patients with cTnT (≥0.03 ng/mL) was 3.2 (95% CI, 1.14-9.0) compared to those with cTnT (b0.03 ng/mL) for mortality (P = .027), and the hazard ratio of patients with hs-cTnI (≥0.03 ng/mL) was 4.7 (95% CI, 1.72-13.1) compared to those with hs-cTnI (b0.03 ng/mL) for mortality (P = .0027). On stepwise multivariate analyses, high plasma NT-proBNP (≥627 pg/mL, P = .0063) and hs-cTnI (≥0.03 ng/mL) (P = .016) were independent significant prognostic predictors but not cTnT (≥0.03 ng/mL). The hazard ratio of patients with high plasma NT-proBNP (≥627 pg/mL) and cTnI (≥0.03 ng/mL) was 5.74 (95% CI, 2.33-14.28, P b .0001)

Discussion In this study, we demonstrated for the first time the prognostic value of hs-cTnI in patients with CHF. We measured serum concentrations of cTnT (fourth-generation Elecsys Troponin T immunoassay; Roche Diagnostics) and measured serum hs-cTnI (Siemens Healthcare Diagnostics) in the same 258 CHF patients with a low LVEF (b45%). In these patients, serum cTnT concentrations were elevated (≥0.03 ng/mL) in 32 patients (12%) and serum hs-cTnI concentrations were elevated (≥0.03 ng/mL) in 112 patients (43%). Moreover, not only a high plasma NT-proBNP (≥627 pg/mL, P = .006) but also an elevated hs-cTnI (≥0.03 ng/mL) (P = .013) was an independent significant prognostic predictor but not an elevated cTnT (≥0.03 ng/mL), suggesting that the assay for hs-cTnI is more sensitive than the conventional commercial assay for cTnT and the sensitive assay system for cTnI or cTnT provides useful information on the

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Figure 4

Kaplan-Meier survival curves according to the combination of cutoff values for NT-roBNP (627 pg/mL) and hs-cTnI (0.03 ng/mL) in patients with chronic heart failure.

prognosis of CHF with low LVEF. Latini et al10 reported the prognostic value of very low plasma concentrations of hs-cTnT measured by a precommercial assay in patients with stable CHF. In this study, we, for the first time, demonstrated the prognostic value of hs-cTnI by a commercial assay system in patients with CHF. Sensitive cardiac troponin assays are more useful for evaluating the early stage of myocardial infarction than conventional troponin assays.18 Taking the findings of Latini et al10 together with our data, sensitive cardiac troponin assays may be useful to predict severity and prognosis in patients with CHF. In the present study, the hazard ratio of patients with high plasma NT-proBNP (≥627 pg/mL) and hs-cTnI (≥0.03 ng/mL) was 5.74 compared to those with low NT-proBNP (b627 pg/mL) or hs-cTnI (b0.03 ng/mL) for mortality (Figure 4), suggesting that the combination of cTnI or cTnT and BNP or NT-proBNP are useful for predicting mortality in patients with CHF, which was consistent with previous reports using the classical assay system of cTnT or cTnI.6,9,19-22 However, cTnT was not an independent prognostic predictor if hs-cTnI is not entered into the multivariable Cox proportional hazard analyses. Therefore, the findings of the present study suggest the usefulness of a sensitive assay for cardiac troponins. Recently, Sabatine at al23 reported that an ultrasensitive assay of cTnI (at Singulex, Berkeley, CA) was more useful for detecting myocardial injury during transient stress test-induced myocardial ischemia than the highly sensitive commercial cTnI assay (Siemens Healthcare Diagnostics Inc., Tarrytown, NY) used in the present assay. Therefore, the greater the sensitivity of the assay system for cTnT and cTnI, the more useful it will be for predicting myocardial injury and/or mortality in patients with CHF. Further large studies are needed to assess this issue using more sensitive assay of cTnT and cTnI. The plasma NT-proBNP level is a biomarker reflecting hemodynamic abnormality such as an increase in left ventricular end-diastolic pressure or left ventricular wall

stress in CHF patients. Because most of the patients with ischemic cardiomyopathy had undergone revascularization and the other patients had a nonischemic etiology in this study, significant increases in cTnT and hs-cTnI concentrations reflect of ongoing myocardial damage. In the present study, there was no correlation between eGFR and hs-cTnI in patients with CHF. In our previous study, there was a significant negative correlation between eGFR and cTnT in the same population,11 suggesting that the impact of renal function on cTnT and cTnI is not the same.24 However, further studies are needed using the more sensitive assay system of cTnT and cTnI. The present study was a substudy of a previous study,13,14 therefore, the small number of patients and deaths are limitations. However, this is the first study to compare the prognostic value of cTnT using a conventional commercial assay and hs-cTnI using the current generation of sensitive commercial assay in the same population. In conclusion, the present study showed that a high plasma concentration of hs-cTnI is an independent and useful prognostic predictor in patients with CHF. Moreover, a high plasma NT-proBNP (≥627 pg/mL) and an elevated hs-cTnI (≥0.03 ng/mL) were independent significant prognostic predictors but not cTnT (≥0.03 ng/ mL) using a conventional commercial assay was not, suggesting that the combination of cTnI on a sensitive assay and NT-proBNP are useful for predicting mortality in patients with CHF with low LVEF (b45%).

Acknowledgements We wish to thank Ms. Yohko Watanabe for excellent technical assistance. We also express thanks to Mr. Daniel Mrozek for assistance in preparing the manuscript.

References 1. Tsutamoto T, Wada A, Maeda K, et al. Attenuation of compensation of endogenous cardiac natriuretic peptide system in chronic heart failure: prognostic role of plasma brain natriuretic peptide concentration in patients with chronic symptomatic left ventricular dysfunction. Circulation 1997;96:509-16. 2. Maeda K, Tsutamoto T, Wada A, et al. High levels of plasma brain natriuretic peptide and interleukin-6 after optimized treatment for heart failure are independent risk factors for morbidity and mortality in patients with congestive heart failure. J Am Coll Cardiol 2000;36: 1587-93. 3. Anand IS, Fisher LD, Chiang YT, et al. Changes in brain natriuretic peptide and norepinephrine over time and mortality and morbidity in the Valsartan Heart Failure Trial (Val-HeFT). Circulation 2003;107: 1278-83. 4. Richards AM, Doughty R, Nicholls MG, et al. Plasma N-terminal pro-brain natriuretic peptide and adrenomedullin: prognostic utility and prediction of benefit from carvedilol in chronic ischemic left ventricular dysfunction. Australia-New Zealand Heart Failure Group. J Am Coll Cardiol 2001;37:1781-7.

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5. Sato Y, Yamada T, Taniguchi R, et al. Persistently increased serum concentrations of cardiac troponin t in patients with idiopathic dilated cardiomyopathy are predictive of adverse outcomes. Circulation 2001;103:369-74. 6. Ishii J, Nomura M, Nakamura Y, et al. Risk stratification using a combination of cardiac troponin T and brain natriuretic peptide in patients hospitalized for worsening chronic heart failure. Am J Cardiol 2002;89:691-5. 7. Setsuta K, Seino Y, Ogawa T, et al. Use of cytosolic and myofibril markers in the detection of ongoing myocardial damage in patients with chronic heart failure. Am J Med 2002;113:717-22. 8. Horwich TB, Patel J, MacLellan WR, et al. is associated with impaired hemodynamics, progressive left ventricular dysfunction, and increased mortality rates in advanced heart failure. Circulation 2003; 108:833-8. 9. Ishii J, Cui W, Kitagawa F, et al. Prognostic value of combination of cardiac troponin T and B-type natriuretic peptide after initiation of treatment in patients with chronic heart failure. Clin Chem 2003;49: 2020-6. 10. Latini R, Masson S, Anand IS, et al. Prognostic value of very low plasma concentrations of troponin T in patients with stable chronic heart failure. Circulation 2007;116:1242-9. 11. Tsutamoto T, Kawahara C, Yamaji M, et al. Relationship between renal function and serum cardiac troponin T in patients with chronic heart failure. Eur J Heart Fail 2009;11:653-8. 12. Alpert JS, Thygesen K, White HD, et al. Implications of the universal definition of myocardial infarction. Nat Clin Pract Cardiovasc Med 2008;5:678-9. 13. Tsutamoto T, Wada A, Sakai H, et al. Relationship between renal function and plasma brain natriuretic peptide in patients with heart failure. J Am Coll Cardiol 2006;47:582-6. 14. Tsutamoto T, Sakai H, Nishiyama K, et al. Direct comparison of transcardiac increase in brain natriuretic peptide (BNP) and N-terminal proBNP and prognosis in patients with chronic heart failure. Circ J 2007;71:1873-8.

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15. Levey AS, Coresh J, Greene T, et al. Using standardized serum creatinine values in the modification of diet in renal disease study equation for estimating glomerular filtration rate. Ann Intern Med 2006;145:247-54. 16. Tsutamoto T, Sakai H, Ishikawa C, et al. Direct comparison of transcardiac difference between brain natriuretic peptide (BNP) and N-terminal pro-BNP in patients with chronic heart failure. Eur J Heart Fail 2007;9:667-73. 17. James S, Flodin M, Johnston N, et al. The antibody configurations of cardiac troponin I assays may determine their clinical performance. Clin Chem 2006;52:832-7. 18. Reichlin T, Hochholzer W, Bassetti S, et al. Early diagnosis of myocardial infarction with sensitive cardiac troponin assays. N Engl J Med 2009;361:858-67. 19. Ralli S, Horwich TB, Fonarow GC. Relationship between anemia, cardiac troponin I, and B-type natriuretic peptide levels and mortality in patients with advanced heart failure. Am Heart J 2005;150: 1220-7. 20. Yin WH, Chen JW, Feng AN, et al. Multimarker approach to risk stratification among patients with advanced chronic heart failure. Clin Cardiol 2007;30:397-402. 21. Fonarow GC, Peacock WF, Horwich TB, et al. Usefulness of B-type natriuretic peptide and cardiac troponin levels to predict in-hospital mortality from ADHERE. Am J Cardiol 2008;101: 231-7. 22. Zairis MN, Tsiaousis GZ, Georgilas AT, et al. Multimarker strategy for the prediction of 31 days cardiac death in patients with acutely decompensated chronic heart failure. Int J Cardiol 2009. 23. Sabatine MS, Morrow DA, de Lemos JA, et al. Detection of acute changes in circulating troponin in the setting of transient stress test-induced myocardial ischaemia using an ultrasensitive assay: results from TIMI 35. Eur Heart J 2009;30:162-9. 24. Fehr T, Knoflach A, Ammann P, et al. Differential use of cardiac troponin T versus I in hemodialysis patients. Clin Nephrol 2003;59: 35-9.