Acute coronary syndrome vs nonspecific troponin elevation: clinical predictors and survival analysis

BACKGROUND: Although troponin is considered a specific marker for the diagnosis of acute coronary syndrome (ACS), recent studies have shown troponin elevation in a variety of nonischemic conditions. Our aim was to determine the predictors for the diagnosis of ACS in the presence of an abnormal troponin level. METHODS: All patients with abnormal troponin T levels were analyzed. Demographic and clinical data were collected and death was recorded. The study group was divided into 2 subgroups: ACS vs nonthrombotic troponin elevation. A multivariate logistic regression analysis was performed to define variables that predict the diagnosis of ACS. The positive predictive value (PPV) for ACS diagnosis was calculated, and a survival analysis was performed. RESULTS: During the study period, 615 patients had elevated troponin T levels. Only 326 patients (53%) received a main diagnosis of ACS, while 254 (41%) had nonthrombotic troponin elevation; for 35 patients (6%), the diagnosis was not conclusive. Positive predictors for the diagnosis of ACS were age between 40 and 70 years, history of hypertension or ischemic heart disease, normal renal function, and a troponin T level higher than 1.0 ng/mL. The overall PPV of troponin T for ACS diagnosis was only 56% (95% CI, 52%-60%). The PPV of troponin T level higher than 1.0 ng/mL in the presence of normal renal function was 90% but was as low as 27% for values of 0.1 to 1.0 ng/mL for elderly patients with renal failure. In-hospital and long-term survival rates were significantly better (P<.001) for patients with ACS. CONCLUSIONS: Nonspecific troponin elevation is a common finding among hospitalized patients and correlates with worse prognosis. The diagnosis of myocardial infarction should still mostly be based on the clinical presentation. The predictors and algorithm suggested in this study might increase the diagnostic accuracy of ACS and direct the appropriate treatment.     

Acute coronary ischemia: troponin I and T

Despite advances in diagnosis and management, ischemic heart disease remains the leading cause of death in the USA. Serum cardiac enzymes, one of the three fundamental criteria for establishing the diagnosis of myocardial infarction, are not specific for cardiac muscle and have a narrow time-window. The recent development of monoclonal antibodies to cardiac troponin I and troponin T has resulted in cardiac-specific assays. Several published studies have documented the utility of troponin proteins in the evaluation of myocardial necrosis. A brief overview of the characteristics and clinical utility of troponin T and I is presented here.     

急性冠脉综合征与血清肌钙蛋白Ⅰ及其他危险IN素的相关性分析

目的探讨急性冠脉综合征（ACS）与血清肌钙蛋白Ⅰ（cTnⅠ）、血脂、体重指数（BMI）等的关系。方法A组70例，为健康对照组；B组51例，为ACS的不稳定型心绞痛（UA）组；C组41例，为ACS的急性心肌梗死（AMI）组。检测cTnⅠ时间：A组为清晨空腹取静脉血3．0ml送检，B组于心绞痛发作后3h取静脉血3．0ml送检，C组于发现AMI时立即取静脉血3．0ml送检。A、B、C组全部采用肌钙蛋白Ⅰ快速测试板检测，并于禁食12h次晨采静脉血测血脂。结果A组cTnⅠ全部阴性，B组阳性8例，C组全部为阳性，A组、B组、C组各组之间比较差异有统计学意义（P〈0．05）。ACS组（B＋C组）的血总胆固醇（TC）、甘油三酯（TG）、BMI均增高，与对照组比较差异有统计学意义（P〈0．05），ACS组高血压及糖尿病的发病率与对照组比较差异有统计学意义（P〈0．05）。结论cTnⅠ作为一种新的心肌标志物，可作为ACS诊断、估计病情严重程度及预后的重要指标。血脂及BMI、高血压及糖尿病与ACS关系密切。     

Guidelines: Acute coronary syndrome (ACS). II: Acute coronary syndrome with ST-elevation

Ohne Zusammenfassung     

肌钙蛋白测定在急性冠脉综合征中的应用

心肌肌钙蛋白(Cardiac Troponins,cTn)作为心肌损伤的非酶学指标,在急性心肌梗死的诊断中因其敏感性高、特异性强、在血液中出现早、持续时间长、对微小心肌损伤具有诊断价值等优点近年备受重视,目前已作为新的"金标准"而逐渐取代肌酸激酶同功酶MB(CK-MB)的地位,并广泛应用于急性冠状动脉综合征(acute coronary syndrome,ACS)的诊断、治疗、危险分层及预后评价等各个方面.     

Acute coronary syndrome in the older adults

Coronary heart disease remains the leading cause of death in the developed world. Advanced age is the single strongest risk factor for coronary artery disease (CAD) and independent predictor for poor outcomes following an acute coronary syndrome (ACS). ACS refers to a spectrum of conditions compatible with acute myocardial ischemia and/or infarction due to various degrees of reduction in coronary blood flow as a result of plaque rupture/erosion and thrombosis formation or supply and demand mismatch. Unstable angina and non -ST segment elevation myocardial infarction are often continuous and clinically indistinguishable, collectively referred as non -ST elevation ACS (NSTE-ACS). An abrupt total occlusion of a coronary artery causing transmural myocardial ischemia/necrosis and displaying ST segment elevation or new left bundle branch block on a12-lead electrocardiogram (ECG) leads to the diagnosis of ST segment elevation myocardial infarction (STEMI). NSTE-ACS and STEMI require acute cardiac care. Professional societies have established guidelines for high quality contemporary care for ACS patients, i.e. American Heart Association/American College of Cardiology guidelines for STEMI1 andNSTE-ACS2, European Society of Cardiology guidelines for STEMI3 and NSTE-ACS4, and the United Kingdom National Institute for Health and Care Excellence (NICE) guidelines for STEMI5 and NSTE-ACS.6 Implementation of evidence-based therapies has significantly decreased mortality and morbidities of ACS.3, 7, 8 However, these advancements in ACS management have not equally improved outcomes for older adults. Vulnerable older patients continue to be at high risk of poor outcomes, are less likely to receive evidence based care, and have high mortality rates regardless of treatments given.9, 10 These disparities and challenges in caring for ACS in older adults are well recognized.11-13 This review summarizes the increasing burden and persistent unfavorable outcome of ACS in older adults, and discusses the clinical presentation, diagnosis and strategies for medical and invasive therapy.     

Prognostic performance of kinetic changes of high-sensitivity troponin T in acute coronary syndrome and in patients with increased troponin without acute coronary syndrome

Background

We sought to evaluate the prognostic impact of absolute and relative kinetic changes of high-sensitivity cardiac Troponin T (hs-cTnT) in comparison to baseline hs-cTnT elevations for risk stratification in acute coronary syndrome (ACS) and non-ACS conditions with increased hs-cTnT.

Methods

hs-cTnT was measured serially in patients presenting with acute symptoms to our emergency department. We assessed the prognostic performance of baseline and serial hs-cTnT concentrations in all consecutive patients with ACS (n = 406) or hs-cTnT increases not due to ACS (n = 442) within 3–6 h after admission.

Results

Mortality rates were higher, albeit not statistically, in non-ACS (53/442 = 12.0%) than ACS patients (36/406 = 8.9%). In ACS patients, receiver operating characteristics (ROC) revealed optimized cut-off values of 12.2 ng/L for absolute δ-change (AUC = 0.66, p < 0.001), 31.2 ng/L for baseline hs-cTnT (AUC = 0.71, p < 0.001) and 45.2 ng/L for maximal hs-cTnT (AUC = 0.68, p < 0.001). C-statistics showed superiority of absolute δ-changes (p = 0.0003), baseline hs-cTnT (p = 0.04) and maximal hs-cTnT (p = 0.02) compared to relative δ-changes. However, the combination of baseline hs-cTnT values with either absolute or relative δ-changes did not improve risk prediction compared to baseline hs-cTnT alone (p = n.s.). In non-ACS conditions, the ROC-optimized cut-off value of 46.2 ng/L for baseline hs-cTnT (AUC = 0.661, p < 0.001) was superior to absolute (p = 0.007) and relative δ-changes regarding prognostication (p = 0.045).

Conclusions

Our data suggest that the magnitude of baseline hs-cTnT, and not acute dynamic changes, convey superior long-term prognostic information in ACS and non-ACS conditions. Moreover, absolute and relative kinetic δ-changes of hs-cTnT do not add significant incremental value in risk assessment in both conditions.     

Cardiac troponin T in acute coronary syndrome with renal insufficiency

Cardiac troponin levels are frequently elevated in patients with chronic renal failure, hence diagnosis of myocardial necrosis is difficult. The prevalence of elevated serum troponin T was determined and its diagnostic value in acute coronary syndrome was assessed in patients with chronic renal insufficiency. A retrospective cross-sectional analysis was performed in 227 patients with chronic renal insufficiency and a diagnosis of unstable angina, non-ST or ST-segment elevation myocardial infarction. All patients had baseline serum troponin T levels measured at previous visits; the baseline troponin T level was raised in 53.3%. Cardiac troponin T levels did not correlate with creatinine levels, and were not affected by dialysis. Mortality after an acute coronary event was high (46.3%). Because of the elevated baseline cardiac troponin T levels, detection of acute coronary syndrome in patients with chronic renal failure requires evaluation of serial cardiac enzyme measurements and serial 12-lead electrocardiograms. Early and definitive cardiac interventions may contribute towards decreasing the mortality rate in this group of patients.     

Patients with acute coronary syndrome and normal high-sensitivity troponin

Background

Failure to identify patients with acute coronary syndrome (ACS) is a serious clinical problem. The incidence, characteristics, and outcome of ACS patients with normal high-sensitivity cardiac troponin T (hs-cTnT) levels at presentation are unknown.

Methods

In a prospective multicenter study, hs-cTnT was determined in a blinded fashion in 1181 consecutive patients presenting with acute chest pain to the emergency department. The final diagnosis of ACS was adjudicated by 2 independent cardiologists. Patients were followed for 12 months.

Results

ACS was the adjudicated diagnosis in 351 patients (30%), including 187 patients with acute myocardial infarction (AMI) and 164 patients with unstable angina (UA). At presentation, hs-cTnT was normal (<.014 ug/L) in 112 ACS patients (32%), including 11 patients (6%) with AMI and 101 patients (62%) with UA (P <.001). Multivariable analysis revealed previous statin treatment, younger age, preserved renal function, and the absence of ST deviation on the electrocardiogram as independently associated with normal hs-cTnT levels. Mortality rates in ACS patients with normal hs-cTnT level were 0.0% at 30 days, 0.0% at 90 days, and 2.0% (95% confidence interval, 0.5-7.9) at 360 days, which was significantly lower than in ACS patients with elevated hs-cTnT level at presentation (17.5% at 360 days, P <.001). Conversely, AMI rates at 360 days was higher in ACS patients with normal versus elevated hs-cTnT levels (P = .004).

Conclusion

Almost one third of ACS patients have normal hs-cTnT levels at presentation, mostly patients with UA. ACS patients with normal hs-cTnT have a very low mortality, but an increased rate of AMI during the subsequent 360 days.