Hallén et al. Cardiovascular Diabetology 2010, 9:52 CARDIO http://www.cardiab.com/content/9/1/52 VASCULAR DIABETOLOGY ORIGINAL INVESTIGATION Open Access Determinants and prognostic implications of Cardiac Troponin T measured by a sensitive assay in Type 2 Diabetes Mellitus Jonas Hallén1,2*, Odd Erik Johansen3, Kåre I Birkeland2,4, Lars Gullestad2,5, Svend Aakhus5, Knut Endresen5, Solve Tjora6, Allan S Jaffe7, Dan Atar1,2 Abstract Background: The cardiac troponins are biomarkers used for diagnosis of myocardial injury. They are also powerful prognostic markers in many diseases and settings. Recently introduced high-sensitivity assays indicate that chronic cardiac troponin elevations are common in response to cardiovascular (CV) morbidity. Type 2 diabetes mellitus (T2DM) confers a high risk of CV disease, but little is known about chronic cardiac troponin elevations in diabetic subjects. Accordingly, we aimed to understand the prevalence, determinants, and prognostic implications of cardiac troponin T (cTnT) elevations measured with a high-sensitivity assay in patients with T2DM. Methods: cTnT was measured in stored, frozen serum samples from 124 subjects enrolled in the Asker and Bærum Cardiovascular Diabetes trial at baseline and at 2-year follow-up, if availabe (96 samples available). Results were analyzed in relation to baseline variables, hospitalizations, and group assignment (multifactorial intensive versus conventional diabetes care for lowering CV risk). Results: One-hundred thirteen (90 %) had detectable cTnT at baseline and of those, 22 (18 % of the total population) subjects had values above the 99th percentile for healthy controls (13.5 ng/L). Levels at baseline were associated with conventional CV risk factors (age, renal function, gender). There was a strong correlation between cTnT levels at the two time-points (r = 0.92, p > 0.001). Risk for hospitalizations during follow-up increased step- wise by quartiles of hscTnT measured at baseline (p = 0.058). Conclusions: Elevations of cTnT above the 99th percentile measured by a highly sensitive assay were encountered frequently in a population of T2DM patients. cTnT levels appeared to be stable over time and associated with conventional CV risk factors. Although a clear trend was present, no statistically robust associations with adverse outcomes could be found. Introduction and lipid lowering, in addition to glucose control, are The majority of deaths in patients with type 2 diabetes necessary for mitigating morbidity and mortality related mellitus (T2DM) are due to cardiovascular (CV) disease. to macrovascular disease [5,6]. Consistent with this con- Although hyperglycemia, the defining feature of T2DM, cept, the prospective, randomized Asker and Bærum is closely associated with microvascular and macrovas- Cardiovascular Diabetes (ABCD) trial on 120 T2DM cular complications[1], studies have failed to demon- subjects found that structured care encompassing a strate that glucose lowering per se reduces the risk of comprehensive and intensive preventive strategy reduced macrovascular events [2-4]. Thus, current understanding the primary efficacy outcome of change in the estimated suggests that broad, multiple intervention strategies 10-year absolute risk for fatal coronary heart disease at including lifestyle changes, aggressive blood pressure 2 years compared to conventional care [7]. The cardiac troponins T and I are extremely sensitive and specific biomarkers of myocardial necrosis and crucial * Correspondence: [email protected] 1Department of Cardiology, Oslo University Hospital, Oslo, Norway components of the diagnosis of myocardial infarction Full list of author information is available at the end of the article © 2010 Hallén et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Hallén et al. Cardiovascular Diabetology 2010, 9:52 Page 2 of 8 http://www.cardiab.com/content/9/1/52 [8,9]. The recent emergence of several high-sensitivity available. Samples were stored at - 80°C for 4-8 years assays has shown that cardiac troponins can be chronically and measured on the Roche Diagnostics (Basel, Switzer- elevated in response to CV comorbidities and that they land) Cardiac troponin T assay by the electrochemilumi- confer important prognostic information. The presence of nescence method. The limit of the blank is 3 ng/L, the T2DM is a known predictor of elevated cardiac troponin limit of detection 5 ng/L, and the 99th percentile was T in the general population with contemporary assays determined to be 13.5 ng/L in 616 apparently healthy [10], but the prevalence, determinants and prognostic volunteers [12]. Assays were performed by personnel implications of cardiac troponin T elevations measured by unaware of the patient’s identity or other characteristics. a high-sensitivity assay in T2DM subjects have not been Details regarding sampling strategies and assay charac- investigated. Furthermore, it is unknown whether troponin teristics for the laboratory determinations of the other levels are lowered by aggressive CV risk-factor modifica- serum markers have been described previously [7,11]. tion in this patient group. Accordingly, in the present post Details of all procedures and clinical tests have been hoc analysis of the ABCD study, we attempted to define published previously [7,11]. In brief, for the exercise test the distribution and determinants of cardiac troponin we used a modified maximum symptom-limited 1-min T levels in patients enrolled in the trial at baseline, and incremental exercise test on an electrically braked cycle investigate whether the structured, intensive care delivered ergometer (Siemens-Elema, Germany). The patients in the ABCD trial results in lower cardiac troponin maintained a constant pedaling-rate of 60 rotations per T values after 2 years of follow-up. In addition, we wanted minute. Simultaneous haemodynamic monitoring was to tentatively explore whether cardiac troponin T levels performed and symptoms of chest pain were recorded were associated with hospitalizations during follow-up. during exercise. A 12-lead Likar-Mason modified elec- trocardiogram was continuously sampled every 2 ms Methods (500 Hz sampling rate) and converted to digital form Setting, design and participants with a 12-bit resolution. Standard ST-segment depres- We performed a post hoc analysis of the ABCD study sion criterion (> 1 mm [0.1 mV]) or additional horizon- conducted at Vestre Viken, Asker and Baerum Hospital, tal or down-sloping ST-segment depression at end Rud, Norway from 2002 to 2006. The study enrolled exercise was used for assessment of the ECG. 133 subjects with T2DM for a cross-sectional investiga- Dobutamine stress echocardiography was performed tion of the prevalence of coronary artery disease. Exclu- using a staged protocol with dobutamine infusions up to sion criteria were clinically significant peripheral 40 μg/kg/min in increments of 3 minutes with atropine (defined as amputation-threatening ischemia) or cerebral 0,25-1,0 mg added when needed to obtain peak heart artery disease or type 1 DM (the presence of autoantibo- rate [13]. Peak stress was defined as either of: new or dies towards pancreatic beta cells and insulin initiation worsened left ventricular regional wall motion abnorm- within one year since the diagnosis of T2DM). Partici- ality, HR > 220 - age (years), blood pressure > 200/110 pants underwent clinical examination, 24 hour Holter mmHg, or patient discomfort. Ultrasound cine loops of monitoring and blood pressure measurements, stress left ventricle imaged from 3 apical and 2 parasternal electrocardiogram, and testing of ventilatory oxygen imaging planes were obtained (Vivid 7 or Vivid 5 scan- uptake, in addition to blood and urine sampling. 120 of ners, GE Vingmed Sound, Horten, Norway) at rest, at the original 133 participants had ≥ 1CVriskfactor 10 and 20 μg dobutamine/kg/min and at peak stress, andagreedtobepartofaprospective,randomized and transferred for off-line analysis. Left ventricular wall controlled trial of intensive versus usual care in T2DM motion analysis was performed by a blinded experienced subjects. Figure 1 provides an overview of the inclusion observer. Wall motion score index was assessed by use and exclusion of patients. Individuals included in the of a 16 segments model of the left ventricle [14]. Rever- prospective trial were referred for voluntary stress echo- sible myocardial ischemia was defined as new or pro- cardiography and invasive coronary angiography. Details gressing wall motion abnormality during test in > = 1 of the design and results of the cross-sectional and segment. prospective studies have been published [7,11]. All parti- Coronary angiography was performed using standard cipants gave written informed consent and the studies Judkins’ technique, with a percutaneous radial or femoral were conducted in accordance with the Helsinki approach using 6F diagnostic catheters (Cordis Corpora- Declaration and approved by the Regional Ethics tion, Miami, FL, US) and the water-soluble, non-ionic, Committee and the Norwegian Data Inspectorate. dimeric contrast medium iodixanol (Visipaque 320 mg/ mL;AmershamHealth,Oslo,Norway).Theangiograms Data collection and procedures were performed after routine referral to the catheteriza- Cardiac troponin