Abstract
Background Several cardiac biomarkers, especially brain natriuretic peptide (BNP) and N-terminal (NT)-proBNP, have been used as predictors of prognosis and negative remodeling in DCM. In the present study, we aimed to evaluate the prognostic value of tenascin-C in dilated cardiomyopathy (DCM) and whether it can be used to determine reverse remodeling in patients with DCM.
Methods Sixty-six patients with DCM were followed up for 12 months after initiation of medical treatment including carvedilol, ramipril (candesartan if ramipril was not tolerated), spironolactone, and furosemide. Tenascin-C and NT-proBNP measurements and transthoracic echocardiography were performed at baseline and at 12 months.
Results At 12 months, a significant improvement in New York Heart Association class (2.57 ± 0.6 vs. 1.87 ± 0.5; P < 0.0001), left ventricular end-diastolic volume (217 ± 47 vs 203 ± 48; P < 0.0001), left ventricular ejection fraction (29.1 ± 5.5 vs 30.9 ± 3.8; P < 0.0001), NT-proBNP (2019 ± 558 vs 1462 ± 805; P < 0.0001), and tenascin-C (76 ± 19 vs 48 ± 28; P < 0.0001) values were observed, compared with baseline. Importantly, decrease in tenascin-C values were correlated with increase in left ventricular ejection fraction. Tenascin-C (odds ratio [OR], 1.896; <95% confidence interval [CI], 1.543–2.670; P = 0.02), diabetes mellitus (OR, 2.456; G95% CI, 1.987–3.234; P = 0.01) and hypertension (OR: 2.106, <95% CI, 1.876–2.897; P = 0.03) were independent predictors of mortality in patients with DCM.
Conclusion Reverse ventricular remodeling obtained with carvedilol, ramipril/candesartan, and spironolacton is associated with decreases in left ventricular end-diastolic volume, left ventricular end-systolic volume, tenascin-C levels, and NT-proBNP levels. Consequently, tenascin-C may be used to evaluate reverse remodeling in patients with DCM.
Dilated cardiomyopathy (DCM) defines a group of myocardial disorders that are characterized by ventricular dilation and depressed myocardial contractility in the presence of abnormal loading conditions.1Dilated cardiomyopathy is characterized with progressive left ventricular (LV) remodeling and functional disruption which is amenable for clinical and symptomatic deterioration. Despite recent developments in pharmacological management, heart failure due to DCM still remains one of the major causes of frequent hospitalizations and high mortality in patients older than 65 years.2Optimization of treatment with proven drug regiments is essential for reducing mortality and hospitalizations and improving quality of life. Recently, cardiac resynchronization therapy, implantable cardioverter defibrillators, and heart transplantation have been introduced as new techniques to reduce mortality in patients with DCM.3Therefore, rapid categorization of patients able to benefit from either medical treatment or invasive procedures carries great importance.
Several cardiac biomarkers especially brain natriuretic peptide (BNP) and N-terminal (NT)-proBNP have been used as predictors of prognosis and negative remodeling in DCM. As known well, NT-proBNP levels are elevated in heart failure and decrease with optimal medical treatment.4,5However, novel markers with high diagnostic and prognostic value may support the diagnostic effort and reflect the efficiency of treatment more accurately in patients with DCM and heart failure.6,7Tenascin-C is an extracellular matrix glycoprotein with strong bioactivity, transiently expressed during embryonic development, wound healing, and cancer invasion.8Accumulating evidence suggests that tenascin-C may be a key regulator in an early step of the fibrotic process in various tissues.9In the heart, tenascin-C is sparsely detected in normal adults but becomes expressed in the pathological myocardium closely associated with inflammation and tissue remodeling.10,11Also, it was recently reported that tenascin-C might be a clinical marker for ventricular remodeling both in patients with DCM and acute myocardial infarction.1,12
However, the role of these biochemical markers in the process of reverse LV remodeling after administration of optimal medical treatment targeting heart failure has not been studied yet. Therefore, in the present study, we aimed to evaluate the prognostic and predictive value of tenascin-C on LV remodeling and mortality in the patients with DCM and heart failure.
MATERIALS AND METHODS
Patient Selection
Seventy-six consecutive patients with newly diagnosed dilated cardiomyopathy were screened between March 2007 and February 2010. However, only 70 of these patients fulfilled the inclusion criteria and enrolled in the study. The diagnosis of DCM was based on the patients’ history, physical examination, electrocardiography, chest x-ray, echocardiography, and cardiac catheterization, including coronary arteriography, left ventriculography, and endomyocardial biopsy. No patients had significant coronary artery stenosis.
Inclusion criteria were the following: (1) ejection fraction (EF) less than 40%; (2) chronic stable HF of New York Heart Association functional class II or III; (3) no significant coronary artery stenosis confirmed by coronary angiography; (4) no prior administration of angiotensin converting enzyme (ACE) inhibitor, angiotensin receptor blocker, or β-blocker therapy. Exclusion criteria were secondary DCM, infectious or inflammatory diseases, collagen diseases, malignancy, impaired liver or kidney function (serum creatinine >1.2 mg/dL), and having had severe trauma or undergone surgical procedures 3 months before the study. Also, patients with prior history of cardiac surgery, significant valvular heart disease, implanted cardiac resynchronization therapy, and secondary cardiomyopathy and patients with contraindications to administration of β-blockers, ACE inhibitors, or angiotensin receptor blockers were excluded from the study protocol. Ramipril, at an initial dose of 2.5 mg/d and target dose of 10 mg/d, was administered to patients and increased in every 2 weeks up to the maximal tolerated or target dose (10 mg/d). Candesartan with initial dose of 8 mg/d was administered to patients intolerant to ramipril. Carvedilol, at an initial dose of 3.125 mg twice daily was administered to patients. Every 2 weeks, the dose of β-blocker was increased to the target dose of 25 mg twice daily or maximal tolerated dose. An adequate dose of furosemide was also added if needed. All medication doses were optimized before enrollment and remain edunchanged during the study. The length of polypharmacologic treatment optimization before enrollment was 6.8 weeks. Forty healthy volunteers were selected as controls for tenascin-C analysis.
Echocardiography
All patients were imaged in the left lateral decubitus position using the same ultrasound system (VIVID 7, GE Vingmed Ultrasound, Horten, Norway) by 2 blinded observers. Two-dimensional and M-mode echocardiograms were obtained according to the American Society of Echocardiography guidelines. Global LV function was assessed with Simpson rule by measuring LV end-diastolic volume (LVEDV) and LV end-systolic volume (LVESV).13All echocardiographic analyses were performed by observers not involved in clinical follow-up and were blinded to the clinical data at all times.
Sixty-six of the enrolled patients were assessed before and at 12 months after initiation of optimal medical treatment targeting heart failure. Left ventricular end-diastolic volume, LVESV, and LV ejection fraction (LVEF) were measured at baseline and 12 months.
Transmitral flow early velocity (E) was measured with spectral Doppler and peak early mitral annular velocity (E′) was measured with tissue Doppler imaging using apical 4-chamber view. The E′ was measured and E/E′ was calculated as E divided by E′.
Biochemical Analysis
Blood samples for NT-proBNP and tenascin-C analyses were obtained at baseline and at 12 months. Blood samples were centrifuged at 15,000g for 15 minutes, and the resulting supernatants were stored at −80°C until analysis. Serum levels of tenascin-C with the large subunit containing the C domain of FNIII repeats were determined by using an enzyme-linked immunosorbent assay (ELISA) kit with 2 monoclonal antibodies (IBL, Gunma, Japan). Serum levels of NT-pro BNP were also determined by using an ELISA kit (Cortez Diagnostics, Calabasas, CA).
Statistical Analysis
The Statistical Package for Social Sciences version 15.0 (SPPS, Chicago, IL) was used for statistical analysis. Data were expressed as means ± standard deviation for continuous variables, and as numbers (percentages) for categorical variables. Comparisons of pretreatment and posttreatment variables were made using the 2-tailed paired Student t test. Independent samples t test was used to compare continuous variables between the patients and the controls. The χ2 test was used to compare categorical data. Pearson or Spearman correlation analysis was performed to estimate correlations between variables. The association of different variables with mortality was calculated in univariate analysis. The variables for which the unadjusted P < 0.10 in logistic regression analysis were identified as potential risk markers (hypertension, diabetes mellitus, LVEF, and tenascin-C) and included in the full multivariate model. Backward elimination multivariate logistic regression analyses using likelihood ratio tests to eliminate variables were used. P < 0.05 was considered to indicate statistical significance.
RESULTS
Optimal medical therapy with the maximal tolerated doses of ramipril/candesartan and carvedilol was maintained for up to 12 months after randomization. Four of 70 patients did not complete the study protocol (1 patient developed sinusal bradycardia during follow-up and 3 patients were lost to follow-up). Therefore, longitudinal data were available in 66 patients (39 men and 27 women) with a mean ± SD age of 67 ± 8 years. The mean maintenance dosages were 33.8 mg/d for carvedilol and 8.6 mg/d for ramipril. Baseline characteristics are listed in Table 1. Baseline tenascin-C values, NT-proBNP values, LVEDV, LVESV, LVEF, and E/E′ ratio were significantly different between the patients with DCM and the controls (Table 1).
At 12 months after initiation of optimal medical treatment, a significant improvement in clinical parameters represented by New York Heart Association class (2.57 ± 0.07 vs 1.87 ± 0.07; P < 0.0001) was observed in the patients with DCM. In addition, echocardiography revealed a significant improvement in LVEF (29.1% ± 0.6% vs 30.9% ± 0.8%; P < 0.0001), LVEDV (217 ± 47 vs 203 ± 48 mL; P < 0.0001) and LVESV (153 ± 41 vs 139 ± 43 mL; P < 0.0001) and E/E’ ratio (14.8 ± 2.2 vs 8.4 ± 2.4; P < 0.001) compared with baseline values (Table 2). Eleven patients died of advanced heart failure and sudden cardiac death during follow-up.
At 12 months of optimal medical treatment, tenascin-C levels were significantly decreased compared with the baseline levels (76.5 ± 19 vs 48.1 ± 28 ng/mL; P < 0.0001). N-terminal proBNP values were also significantly decreased at 12 months (2019 ± 558 vs 1462 ± 805 pg/mL; P < 0.0001) compared with the baseline values (Table 2). Decrease in the tenascin-C values were correlated with increase in the LVEF and decrease in the LVEDV (Figs. 1,2). In addition, tenascin-C values were correlated with NT-proBNP values at baseline (r = 0.847; P < 0.001) and at 12 months (r = 0.832; P < 0.001). Tenascin-C values were also correlated with E/E’ ratio at baseline (r = 0.685; P < 0.001) and at 12 months’ follow-up (r = 0.593; P < 0.001).
Also, the effects of multiple variables on mortality were analyzed with univariate and multivariate logistic regression analyses. At multivariate analysis, tenascin-C (odds ratio [OR], 1.896; <95% confidence interval [CI], 1.543–2.670; P = 0.02), diabetes mellitus (OR, 2.456; G95% CI, 1.987–3.234; P = 0.01) and hypertension (OR, 2.106; <95% CI, 1.876–2.897; P = 0.03) were independent predictors of mortality in the patients (Table 3).
DISCUSSION
The major findings of the present study are as follows: (1) In patients with DCM and heart failure, tenascin- C levels are decreased with administration of optimal medical treatment including β-blockers and ACE inhibitors; (2) decreases in tenascin-C levels are significantly associated with improvements in New York Heart Association functional class, LVEF, LVEDV, LVESV, and BNP level, indicating that circulating tenascin-C is associated with the severity of LV dysfunction; (3) furthermore, tenascin-C, diabetes mellitus, and hypertension are independent predictors of mortality in DCM. Also, decline in LVEDV and LVESV after initiation of optimal medical treatment targeting heart failure are positively correlated with decline in levels of circulating tenascin-C, suggesting that tenascin-C may be used as a marker of negative remodeling.
In a previous study, Aso et al.14demonstrated that tenascin-C levels were increased in patients with DCM in association with lower LVEF and higher LV volumes. In a study of Tamura et al.,15which examined biopsy specimens of hearts obtained from DCM patients, they found that tenascin-C is distributed in the enlarged perimysium and endomysium near replacement fibrotic lesions close to necrotizing myocytes and in the peripheral portion of the replacement fibrotic lesions. They also concluded that tenascin-C has an important role in the initiation of replacement fibrosis in patients with DCM.15In the light of previous studies and the present study, we speculate that patients with DCM and persistently increased levels of circulating tenascin-C might have ongoing myocardial fibrosis and ventricular dilation, resulting in adverse outcomes.
Tenascin-C is a large extracellular matrix protein that is primarily expressed during embryonic development of the myocardium, heart valves, and coronary vessels as well as in wound healing and cancer invasion in various tissues, which can regulate cell behavior and matrix organization during tissue remodeling.16However, it is re-expressed in the adult heart under various pathological conditions associated with extensive tissue remodeling, including acute myocardial infarction, myocarditis, and DCM.17–19
Sato et al.11has shown that during acute phase of anterior myocardial infarction (MI), tenascin-C levels are elevated, suggesting that tenascin-C may act as a novel inflammatory marker of LV remodeling and the prognosis after anterior MI As shown previously, tenascin-C is expressed especially in inflammatory lesions of myocardium such as myocarditis and acute MI.19–22In addition, increased levels of tenascin-C in patients with DCM suggest involvement of myocardial inflamation.1In DCM, tenascin-C contributes to adverse LV remodeling by weakening the binding between cardiomyocytes and the ECM, leading to cardiomyocyte slippage, LV dilatation, and a reduction in contractile function.23
Although the relation of tenascin-C and LV remodeling is well known, its relation with reverse remodeling is in doubt. Until today, the association between LV reverse remodeling and tenascin-C levels in patients with DCM have been studied in only one study. In that study, Hessel et al.19demonstrated decline in tenascin-C levels and LV volumes at 6 months after implantation of CRT device. However, the association between tenascin-C and LV reverse remodeling in patients under optimal medical treatment has not been studied in any trial yet. Results of the present study suggest that decreased levels of tenascin-C in response to optimal medical treatment targeting heart failure is associated with LV reverse remodeling and improved cardiac function. Our study is the first in demonstrating association between tenascin-C levels and LV reverse remodeling after initiation of optimal medical treatment for HF.
Limitations
We included patients with serum creatinine levels of less than 1.2 mg/dL and did not measure glomerular filtration rate in our study population. Enrollment of patients with impaired renal functions would probably provide more realistic data in our patients.
CONCLUSION
Optimal medical therapy targeting heart failure improves clinical symptoms and LV function in most patients with heart failure. Reverse ventricular remodeling after optimal medical therapy is associated with decreased levels of tenascin-C and NT-proBNP.
In conclusion, these biochemical markers may be used to evaluate reverse remodeling in patients with DCM.