Impact of the revised criteria for acute myocardial infarction using cardiac troponins in a Japanese population with acute coronary syndromes.

BACKGROUND: The clinical implications of applying the new criteria of acute myocardial infarction (AMI) with cardiac troponins in terms of their diagnostic and prognostic impact in patients with suspected acute coronary syndromes (ACS) have not been well evaluated. METHODS AND RESULTS: The study group comprised 973 consecutive patients who were diagnosed as having ACS with or without ST elevation (STE). They were divided into 3 groups: unstable angina (UA) group (n=195) representing patients with no significant elevations of creatine kinase (CK) and troponin T (TnT); TnT-myocardial infarction (MI) group (n=170) with TnT elevation and no CK elevation (additionally detected AMI by the new criteria); CK-MI group (n=608) with significant elevation of CK (AMI by the old criteria). In the TnT-MI group, 140 (76%) patients had non-STE ACS. In-hospital mortality rates for STE ACS were 0%, 2.5% and 9.7% in the UA, TnT-MI and CK-MI groups, respectively. The corresponding values for non-STE ACS were 1.8%, 4.6%, and 16.5%, respectively (p<0.0001), suggesting a pivotal role of TnT. In multiple logistic regression analysis, significant CK elevation was selected as an independent predictor of in-hospital death in concurrence with age > or =75 years, prior MI, shock and low left ventricular ejection fraction in non-STE ACS. CONCLUSIONS: The new criteria result in a substantial increase in the diagnosis of AMI from non-STE ACS in particular. They assist greatly in detailed risk stratification of ACS patients, notably in cooperation with the old CK criteria.     

Impact of troponin T determinations on hospital resource utilization and costs in the evaluation of patients with suspected myocardial ischemia

The evaluation and triage of patients with suspected myocardial ischemia in the emergency department remains challenging and costly. Previous studies of cardiac troponins have focused predominantly on patients with chest pain and have not randomized patients to different diagnostic strategies. Eight hundred fifty-six patients with suspected myocardial ischemia were prospectively randomized to receive a standard evaluation, including serial electrocardiographic and creatine phosphokinase-MB determinations (controls) or a standard evaluation with the addition of serial troponin T determinations (troponin group). The primary end points were length of stay and hospital charges. Significant reductions in length of hospital stay were seen in troponin T patients both with (3.6 vs 4.7 days; p = 0.01) and without (1.2 vs 1.6 days; p = 0.03) acute coronary syndromes compared with controls. Total hospital charges were reduced in a similar fashion in troponin patients with and without acute coronary syndromes ($15,004 vs $19,202; p = 0.01, and $4,487 vs $6,187; p = 0.17, respectively) compared with controls. Troponin patients without acute coronary syndromes had fewer hospital admissions (25% vs 31%; p = 0.04), whereas troponin patients with acute coronary syndromes had shorter telemetry and coronary care unit lengths of stay (3.5 vs 4.5 days; p = 0.03) compared with controls. Thus, utilization of troponin T in a broad spectrum of emergency department patients with suspected myocardial ischemia improves hospital resource utilization and reduces costs.     

Utility of left bundle branch block as a diagnostic criterion for acute myocardial infarction

The clinical utility of new or "presumably new" left bundle branch block (LBBB) as an electrocardiographic criterion equivalent to ST-segment elevation myocardial infarction in contemporary practice is not well established. The aim of this study was to investigate the hypothesis that new or presumably new LBBB in symptomatic patients frequently leads to an overdiagnosis of acute myocardial infarction (AMI). A retrospective analysis of data from consecutive patients in the Mayo Clinic's ST-segment elevation myocardial infarction network from July 2004 to August 2009 was conducted among 892 patients, 36 (4%) of whom had new LBBB. The frequency, clinical characteristics, serum troponin levels, coronary angiographic findings, and outcomes of patients with new LBBB suspected of having AMI were evaluated. Compared with patients without LBBB (n = 856), those with new LBBB were older (64.5 vs 72.9 years, p < 0.001), had higher Thrombolysis In Myocardial Infarction (TIMI) risk scores (22.7 vs 31.0, p < 0.005), were less likely to undergo primary percutaneous coronary intervention (86% vs 22%, p < 0.001), and had longer door-to-balloon times. Only 14 patients (39%) had final diagnoses of acute coronary syndromes, of which 12 were AMI, while 13 (36%) had cardiac diagnoses other than acute coronary syndrome and 9 (25%) had noncardiac diagnoses. Of the patients with AMI, 5 had occluded culprit arteries, of which 2 involved the left anterior descending coronary artery. A Sgarbossa score ≥ 5 had low sensitivity (14%) but 100% specificity in diagnosing AMI in the presence of new LBBB. In conclusion, new or presumably new LBBB in patients suspected of having AMI identifies a high-risk subgroup, but only a small number have AMI. Two thirds of these patients are discharged from the hospital with alternative diagnoses. The Sgarbossa criteria appear to have limited utility in clinical practice because of their low sensitivity.     

Diagnostic and prognostic role of myoglobin in patients with suspected acute coronary syndrome. North-Württemberg Infarction Study (NOWIS) Group

In patients with suspected acute coronary syndrome, myoglobin is, according to IFCC and NACB guidelines, the marker of choice for early determination of acute infarction, in particular in combination with creatine kinase-MB, 4 hours after admission with a sensitivity of 96%, and correctly excludes Q-wave infarctions. In patients without acute myocardial infarction, a positive troponin T (relative risk 31.5%), but not an elevated myoglobin (relative risk 4.5%), is highly predictive for adverse in-hospital outcome.     

Pregnancy associated plasma protein A, a novel, quick, and sensitive marker in ST-elevation myocardial infarction

Traditional biomarkers in acute coronary syndromes reflect myocardial necrosis but not the underlying arteriosclerotic disease. Pregnancy-associated plasma protein A (PAPP-A) is a new biomarker in acute coronary syndromes that detects vulnerable plaques in arteriosclerotic disease and identifies acute coronary syndromes earlier than traditionally used biomarkers. Information regarding circulating PAPP-A levels in patients with ST elevation myocardial infarctions (STEMIs) is limited and contradictory. The aim of the present study was to describe the presence and time-related pattern of circulating PAPP-A levels in patients with STEMIs. Consecutive patients (n = 354) referred for primary percutaneous intervention because of STEMI were included in the study. Blood samples for the analysis of PAPP-A, creatine kinase-MB (CKMB), and troponin T were drawn at admission and every 6 to 8 hours until biomarkers of myocardial necrosis were consistently decreasing. PAPP-A was measured using a newly developed sandwich enzyme-linked immunosorbent assay technique based on 2 monoclonal antibodies. In total, 1,091 PAPP-A, 1,049 troponin T, and 1,016 CKMB samples were analyzed. Mean PAPP-A values at admission were significantly higher in patients with STEMIs than in those with non-ST elevation myocardial infarctions or unstable angina pectoris (27.6 vs 12.2 mIU/L, p <0.01). In samples drawn <2 hours after admission, the sensitivity of PAPP-A was superior (93%) to that of CKMB (60%) and troponin T (61%). In conclusion, PAPP-A levels are elevated in >90% of patients presenting with STEMIs if measured <6 hours after the onset of symptoms or <2 hours of primary percutaneous coronary intervention. In the early stages of STEMI, PAPP-A seems to be a more sensitive marker of myocardial infarction than CKMB and troponin T.     

New diagnostic criteria for acute myocardial infarction and in-hospital mortality.

BACKGROUND: The recent introduction of new diagnostic criteria for acute myocardial infarction (AMI), with troponin measurement, has increased the number of patients admitted with this diagnosis. OBJECTIVE: To evaluate the epidemiologic and prognostic implications of the new diagnostic criteria for AMI. METHODS: This was a retrospective study of 586 patients admitted for acute coronary syndrome (ACS) to the coronary care unit of our hospital, between 2002 and 2003. Data were collected from RECIMA, the Madeira Ischemic Heart Disease Registry. The population was analyzed following two different definitions of ACS: 1 - old criteria (Group I): AMI with ST elevation (typical symptoms or ECG with ST-segment elevation and raised CK-MB >2x), AMI without ST elevation (typical symptoms or ECG without ST elevation and raised CK-MB >2x) and unstable angina (UA) (symptoms or ECG indicative of ischemia, with normal CK-MB, regardless of troponin status); 2 - new criteria (Group II): AMI with ST elevation (typical symptoms or ECG with segment ST elevation and raised CK-MB >2x or troponin), AMI without ST elevation (typical symptoms or ECG without ST-segment elevation and raised CK-MB >2x or troponin) and UA (symptoms or ECG indicative of ischemia, with normal enzymes). We evaluated whether this change in criteria had any influence on in-hospital mortality. RESULTS: The new criteria significantly (by 11.9 %) increased the total number of patients admitted with AMI. This was due to an increase in AMI without ST elevation (p < 0.001) and a decrease in patients with UA (p < 0.001), with no changes in AMI with ST elevation. In-hospital mortality was lower in patients with AMI diagnosed by the new criteria and in those with UA. CONCLUSION: The overall increase in AMI resulting from the new diagnostic classification was accompanied by a decrease, although not statistically significant, of in-hospital mortality, probably due to the lower risk of the population analyzed.     

Cardiac troponin I level correlates with chronic-phase left ventricular function after successful direct percutaneous transluminal coronary angioplasty in patients with acute myocardial infarction

OBJECTIVES: The relationships between cardiac troponin I, various biochemical markers, and chronic-phase left ventricular ejection fraction (LVEF) after successful direct percutaneous transluminal coronary angioplasty (PTCA) were examined in 36 patients with acute myocardial infarction. METHODS: Biochemical markers were measured on admission, immediately after, and from 6 hours to 9 days after PTCA. RESULTS: The time to peak values were: creatine kinase-MB 9.7 hours, cardiac troponin I 9.8 hours, myoglobin 10.7 hours, creatine kinase 10.6 hours, cardiac troponin T 18.6 hours, and myosin light chain 68.9 hours. Cardiac troponin T, cardiac troponin I and myosin light chain levels were elevated over 9 days after successful direct PTCA. Chronic-phase LVEF inversely correlated with peak values of creatine kinase-MB (r = -0.519, p < 0.01), cardiac troponin T (r = -0.500, p < 0.01), cardiac troponin I (r = -0.441, p < 0.05) and creatine kinase (r = -0.411, p < 0.05). The values of cardiac troponin I, cardiac troponin T, creatine kinase and creatine kinase-MB at each sampling point were significantly inversely related to chronic-phase LVEF. The value of cardiac troponin I at each time point for 7 days correlated well with chronic-phase LVEF. CONCLUSIONS: Cardiac troponin I has high specificity for predicting long-term cardiac function after successful direct PTCA when early values are unavailable.     

What have the new definition of acute myocardial infarction and the introduction of troponin measurement done to the coronary care unit? Impacts on admission rate, length of stay, case mix and mortality

OBJECTIVE: To assess the impact of the new American College of Cardiology/European Society of Cardiology definition of acute myocardial infarction (AMI) and the introduction of troponin measurement on the coronary care unit (CCU). METHODS: This was a retrospective cohort study performed in a tertiary care university hospital. All admissions to the CCU during the year before (period 1, year 2000, n = 1,134) and the year after (period 2, year 2002, n = 1,360) the introduction of troponin measurement and the new AMI definition were studied. We studied baseline characteristics, case load, distribution of admission diagnoses, management and outcome of patients in the two periods. RESULTS: There was a 20% increase in the number of CCU admissions, driven solely by a 141% increase in the burden of non-ST elevation AMI (NSTEMI) (p < 0.01). This increase was not a mere reflection of a change in diagnostic criteria, as the overall burden of non-ST elevation acute coronary syndromes (ACS) (NSTEMI + unstable angina) increased by 46%, suggesting referral of many more patients to the CCU. Despite a 42% increase in the number of angiograms performed, the proportion of ACS patients who had an angiogram declined. AMI patients in period 2 were older and had higher rates of coronary risk factors but had a higher chance of receiving a guideline-based therapy. Length of CCU stay decreased by a whole day for all ACS patients. 30-day mortality for AMI patients did not change significantly. CONCLUSIONS: The new AMI definition had a dramatic impact on the CCU case load, case mix and length of stay and on the ability to provide early coronary angiography.     

血清微小RNA可能是急性心肌梗死的标志物

目的观察急性心肌梗死患者血清中微小RNA（miRNA）水平的变化。方法采用3＇端加多聚poly（A）尾的反转录后荧光定量PCR的方法测定17例急性心肌梗死患者和11例健康对照者血清中miR-1的水平,并测定其血清肌酸激酶（CK）、肌酸激酶同工酶MB（CK-MB）及心肌肌钙蛋白T（cTnT）水平。结果心梗组miR-1水平较对照组升高（P〈0.01）;心梗组患者血清miR-1较对照组均值升高的倍数与其血清CK-MB较对照组均值升高的倍数存在正相关关系（r=0.52,P〈0.05）。结论 miR-1有可能作为急性心肌梗死的标志物,miR-1水平升高的机制可能与心肌梗死灶周围的缺血组织释放增加有关。     

Ability of troponins to predict adverse outcomes in patients with renal insufficiency and suspected acute coronary syndromes: a case-matched study

ObjectivesThe purpose of this study was to investigate the utility of cardiac troponin T and troponin I for predicting outcomes in patients presenting with suspected acute coronary syndromes and renal insufficiency relative to that observed in similar patients without renal disease.BackgroundCardiac troponin T and troponin I have shown promise as tools for risk stratification of patients with acute coronary syndromes. However, there is uncertainty regarding their cardiac specificity and utility in patients with renal disease.MethodsWe measured troponin T, troponin I and creatine kinase MB in 51 patients presenting with suspected acute coronary syndromes and renal insufficiency and in 102 patients without evidence of renal disease matched for the same peak troponin T or I value, selected from a larger patient cohort. Blood samples were obtained at presentation to an emergency room 4 hours, 8 hours and 16 hours later. The ability of biochemical markers to predict adverse outcomes in both groups including infarction, recurrent ischemia, bypass surgery, heart failure, stroke, death or positive angiography/angioplasty during hospitalization and at six months was assessed by receiver-operator curve analysis. The performance of both troponins was compared between groups.ResultsThirty-five percent of patients in the renal group and 45% of patients in the nonrenal group experienced an adverse initial outcome; over 50% of patients in all groups had experienced an adverse outcome by 6 months, but these differences were not significant. The area under the curve (AUC) for the ROC curve for troponin T as predictor of initial outcomes was significantly lower in the renal group than in the nonrenal group: 0.56 ± 0.07 and 0.75 ± 0.07, respectively. The area under the curve was also significantly lower in the renal group compared with the nonrenal group for troponin T as predictor of six month outcomes: 0.59 ± 0.07 and 0.74 ± 0.07, respectively. The area under the curve was also significantly lower in the renal group compared to the nonrenal group for troponin I as predictor of both initial and six month outcomes: 0.54 ± 0.06 vs. 0.71 ± 0.07 and 0.53 ± 0.06 vs. 0.65 ± 0.07, respectively. The sensitivity of troponin T for both initial and six month adverse outcomes was significantly lower in the renal group than in the nonrenal group at a similar level of specificity (0.87): 0.29 vs. 0.60 and 0.45 vs. 0.56, respectively. Troponin I also exhibited similar differences in sensitivity in the renal group (0.29 vs. 0.50 and 0.33 vs. 0.40, respectively).ConclusionsThe ability of cardiac troponin T and troponin I to predict risk for subsequent adverse outcomes in patients presenting with suspected acute coronary syndromes is reduced in the presence of renal insufficiency.     

A new definition for myocardial infarction: what difference does it make?

AIMS: As a response to changing diagnostic tools of myocardial infarction (MI), new case definitions for acute coronary events were published in 2003 as the American Heart Association Scientific Statement. We assessed the new definition in hospitalized patients in a large population-based MI register study. METHODS AND RESULTS: We identified all suspected acute coronary syndromes with data either on troponin T or on troponin I and at least one of the enzymatic markers of myocardial injury (n=6104). The 2003 definition with the use of troponins identified 83% more definite MIs than the WHO MONICA definition using cardiac enzymes. The additional patients were older, had more often diabetes, and received less often thrombolysis and revascularization than those having MI by both definitions. Adjusting for age, sex, study area, and study year, the additional patients with their first MI aged 25-74 had a higher risk of cardiovascular death within 1 year than patients having definite MI by both definitions (hazard ratio 1.6, 95% CI 1.1-2.2). CONCLUSION: The changing diagnostic criteria present a considerable challenge for the assessment of long-term trends in MI events in the community as well as for longitudinal studies of the natural history of MI. The 2003 definition, when applied using troponins, identified a sizable new group of MI patients, among persons with suspected acute coronary syndrome, at high risk of a recurrent event.     

Metabolic syndrome in patients with acute myocardial infarction is associated with increased infarct size and in-hospital complications.

BACKGROUND: Metabolic syndrome (MS), the combination of hypertension, obesity, dyslipidemia, and insulin resistance, is a precursor of diabetes mellitus (DM) and highly prevalent among patients with acute myocardial infarction (AMI). Diabetes mellitus is associated with larger infarct size and worse outcomes after AMI. This study examined infarct size and short-term outcomes among nondiabetic patients with MS following contemporary treatment of AMI. METHODS: Four hundred five consecutive patients with AMI treated with primary percutaneous coronary intervention were evaluated. Patients with diabetes (n=105) were excluded. Those with MS (n=167) included patients with three or more of the following criteria: hypertension, elevated fasting blood glucose, hypertriglyceridemia, low high-density lipoprotein, and obesity [body mass index (BMI)> or =30]. The control group (n=133) included patients without MS or DM. RESULTS: Baseline characteristics were similar except for hypertension, BMI, and dyslipidemia, which by study design were higher in the MS group. The MS group had larger infarct size as determined by peak creatine kinase-MB (79.8+/-133.8 vs. 30.84+/-51.5, P<.001). Overall in-hospital complications were higher in patients with MS (21.1% vs. 9.2%, P=.003). Metabolic syndrome is associated with a 10-fold increased risk of acute renal failure after myocardial infarction (7.9% vs. 0.8%, P=.007). CONCLUSION: Metabolic syndrome in nondiabetic patients with AMI is associated with larger infarct size, more in-hospital complications, and a marked increase of acute renal failure. Awareness of MS and preventative measures is crucial in this population to minimize infarct size and decrease morbidity after AMI.     

心肌损伤标志物联合检测在早期诊断心肌梗死中的应用

目的探讨心肌损伤标志物联合检测在心肌梗死中的早期诊断价值。方法选取2011年6月~2014年6月入住我院的疑似急性心肌梗死患者100例,按照世界卫生组织标准将其分成实验组60例(急性心肌梗死),对照组40例(非急性心肌梗死),联合检测两组心肌损伤标志物。结果实验组cTnl、MYO、CK-MB、CK水平均高于对照组(P0.05),实验组早期敏感性以MYO最高,特异性以cTnl最高。结论心肌损伤标志物在急性心肌梗死诊断中发挥着十分重要的作用,值得在临床上广泛应用,     

Specificity of cardiac troponin I and creatine kinase-MB isoenzyme in asymptomatic long-term hemodialysis patients and effect of hemodialysis on these cardiac markers

OBJECTIVES: The objectives of this study were: (1) to evaluate the specificity of cardiac troponin I and creatine kinase-MB isoenzyme in ambulatory asymptomatic chronic renal failure patients on long-term hemodialysis, and (2) to evaluate the effect of hemodialysis on the serum levels of cardiac troponin I and creatine kinase-MB isoenzyme. METHODS: One hundred and forty-four consecutive ambulatory asymptomatic chronic renal failure patients on hemodialysis for a minimum of 1 year were evaluated clinically. Serum cardiac troponin I and creatine kinase-MB isoenzyme levels were measured with specific monoclonal antibodies before and after dialysis using ACCESS Troponin I and ACCESS CK-MB assays. RESULTS: The specificity of serum cardiac troponin I was 83% with a cutoff level of 0.03 ng/ml, which is an expected level for healthy population, but it rose to 100% with a cutoff level of 0.15 ng/ml, which is a reference level for patients with acute myocardial infarction. Twenty-four (17%) patients had borderline elevation in cardiac troponin I (>0.03 to <0.15 ng/ml). A history of angina pectoris was more common in the borderline-elevated cardiac troponin I subgroup. In 28% of the patients, serum creatine kinase-MB isoenzyme levels were increased with a specificity of 72% at a cutoff level of 4 ng/ml, which is the upper limit of normal, but the specificity rose to 98% by increasing the cutoff level value to 10 ng/ml. There were no statistically significant differences in serum levels of cardiac troponin I and creatine kinase-MB isoenzyme before and after dialysis. CONCLUSIONS: Cardiac troponin I is highly specific in ambulatory asymptomatic chronic renal failure patients on long-term hemodialysis; borderline elevations in cardiac troponin I may represent microinjury to the myocardium. A serum level of creatine kinase-MB isoenzyme >2.5 times of the normal upper limit may be highly specific in this patient population. Hemodialysis per se does not significantly change the serum levels of cardiac troponin I and creatine kinase-MB isoenzyme.     

Routine serum enzyme tests in the diagnosis of acute myocardial infarction. Cost-effectiveness

To determine the cost-effectiveness of routine use of serial SGOT, lactic dehydrogenase (LDH), and LDH isoenzyme determinations in patients with suspected acute myocardial infarction (AMI), 166 consecutive patients admitted to a coronary care unit were prospectively identified and clinical findings analyzed independently using predetermined criteria. Based on chest pain characteristics, ECG, and creatine kinase--MB (CK-MB) results, patients were placed in categories of definite AMI (31%), possible AMI (34%), or AMI excluded (36%). The SGOT and/or LDH patterns were considered positive (ie, suggestive of AMI) in 82% of the patients with definite AMI but only confirmed CK-MB results. Positive SGOT/LDH results yielded new clinically relevant information in only 14 patients (8%). Total charges for SGOT/LDH determinations in these 166 patients totaled $10,938 or approximately $780 for each additional clinically important positive result. When serial ECG and CK-MB results are available, routine serial SGOT/LDH determinations are not justified.     

Cardiac troponin I in acute pericarditis

OBJECTIVES: This study was designed to investigate the prognostic value of cardiac troponin I (cTnI) in viral or idiopathic pericarditis. BACKGROUND: Idiopathic acute pericarditis has been recently reported as a possible cause of nonischemic release of cTnI. The prognostic value of this observation remains unknown. METHODS: We enrolled 118 consecutive cases (age 49.2 +/- 18.4 years; 61 men) within 24 h of symptoms onset. A highly sensitive enzymoimmunofluorometric method was used to measure cTnI (acute myocardial infarction [AMI] threshold was 1.5 ng/ml). RESULTS: A cTnI rise was detectable in 38 patients (32.2%). The following characteristics were more frequently associated with a positive cTnI test: younger age (p < 0.001), male gender (p = 0.007), ST-segment elevation (p < 0.001), and pericardial effusion (p = 0.007) at presentation. An increase beyond AMI threshold was present in nine cases (7.6%), with an associated creatine kinase-MB elevation, a release pattern similar to AMI, and echocardiographic diffuse or localized abnormal left ventricular wall motion without detectable coronary artery disease. After a mean follow-up of 24 months a similar rate of complications was found in patients with a positive or a negative cTnI test (recurrent pericarditis: 18.4 vs. 18.8%; constrictive pericarditis: 0 vs. 1.3%, for all p = NS; no cases of cardiac tamponade or residual left ventricular dysfunction were detected). CONCLUSIONS: In viral or idiopathic acute pericarditis cTnI elevation is frequently observed and commonly associated with young age, male gender, ST-segment elevation, and pericardial effusion at presentation. cTnI increase is roughly related to the extent of myocardial inflammatory involvement and, unlike acute coronary syndromes, is not a negative prognostic marker.     

Usefulness of lactate dehydrogenase and lactate dehydrogenase isoenzymes for diagnosis of acute myocardial infarction

The usefulness of lactate dehydrogenase (LD) and LD isoenzymes in the diagnosis of acute myocardial infarction (AMI) is controversial. The present study reviewed 507 consecutive patients in whom creatine kinase, creatine kinase isoenzymes, LD and LD isoenzymes were ordered over a 1-month period. Of these, 249 had an insufficient number of serial enzyme determinations to establish a laboratory diagnosis of AMI. After excluding an additional 11 patients for other reasons, 247 patients remained for analysis. Of these, only 2 (0.8%) had myocardial infarction by standard clinical criteria with normal creatine kinase and creatine kinase-MB but elevated LD and abnormal LD isoenzymes. Seven patients (7 of 247, 2.8%) had false-positive LD isoenzymes. Thus, the routine use of LD and LD isoenzymes was of no use in most patients (96%) and led to the incorrect diagnosis of AMI more than 3 times as often as it helped with a correct diagnosis. Total 1-month charges for all the LD and LD isoenzymes obtained equalled +42,450. Therefore, it appears that LD and LD isoenzymes are not routinely useful in the diagnosis of AMI and may result in considerable unnecessary expense. It is suggested that LD and LD isoenzymes be ordered only under suspicion of late presentation (greater than 48 hours) of AMI.     

High-sensitive cardiac troponin T

Cardiac troponin is the preferred biomarker for the diagnosis of acute myocardial infarction (AMI). The recent development of a high-sensitive cardiac troponin T (hs-cTnT) assay permits detection of very low levels of cTnT. Using the hs-cTnT assay improves the overall diagnostic accuracy in patients with suspected AMI, while a negative result also has a high negative predictive value. The gain in sensitivity may be particularly important in patients with a short duration from symptom onset to admission. Measurement of cardiac troponin T with the hs-cTnT assay may provide strong prognostic information in patients with acute coronary syndromes, stable coronary artery disease, heart failure and even in the general population; however, increased sensitivity comes at a cost of decreased specificity. Serial testing, as well as clinical context and co-existing diseases, are likely to become increasingly important for the interpretation of hs-cTnT assay results.     

Prognostic implications of elevated whole blood choline levels in acute coronary syndromes

Troponins I and T represent the current biomarker standard for diagnosis of myocardial infarction. Even small increases of cardiac troponins have prognostic implications, but not all patients at risk are correctly classified, particularly at admission. We identified elevated whole-blood choline as a promising marker and performed a prospective study of 327 patients with a suspected acute coronary syndrome that focused on the analysis of troponin-negative patients. Diagnostic classification of patients and the definition of troponin cutoffs were performed according to the new European Society of Cardiology/American College of Cardiology criteria. Blood was sampled serially and choline was measured using high-performance liquid chromatography mass spectrometry in whole blood. Patients were followed for 30 days. In patients with negative troponin I test results at admission (n = 250), choline was a predictor of cardiac death and nonfatal cardiac arrest (hazard ratio 6.0, p = 0.003), life-threatening arrhythmias (hazard ratio 3.75, p = 0.004), heart failure (hazard ratio 2.87, p = 0.002), and coronary angioplasty (hazard ratio 2.57, p = 0.001). In multivariate analysis of troponin-negative patients, choline was the strongest predictor of cardiac death or arrest (odds ratio 6.05, p = 0.01). Choline was not a marker for myocardial necrosis but indicated high-risk unstable angina in patients without acute myocardial infarction (sensitivity 86.4%, specificity 86.2%). Thus, an increased concentration of choline at hospital admission is a predictor of adverse cardiac events in patients with suspected acute coronary syndromes. Whole blood choline may be useful for early risk stratification of these patients, particularly if troponin results are negative on admission.     

Evaluation of troponin T criteria for periprocedural myocardial infarction in patients with acute coronary syndromes

In patients with acute coronary syndromes undergoing percutaneous coronary intervention (PCI), the diagnosis of periprocedural myocardial infarction is often problematic when the pre-PCI levels of cardiac troponin T (TnT) are elevated. Thus, we examined different TnT criteria for periprocedural myocardial infarction when the pre-PCI TnT levels were elevated and also the associations between the post-PCI cardiac marker levels and outcomes. We established the relation between the post-PCI creatine kinase-MB (CKMB) and TnT levels in 582 patients (315 with acute coronary syndromes and 272 with stable coronary heart disease). A post-PCI increase in the CKMB levels to 14.7 μg/L (3 × the upper reference limit [URL] in men) corresponded to a TnT of 0.23 μg/L. In the 85 patients with acute coronary syndromes and normal CKMB, but elevated post peak TnT levels before PCI (performed at a median of 5 days, interquartile range 3 to 7), the post-PCI cardiac marker increases were as follows: 21 (24.7%) with a ≥ 20% increase in TnT, 10 (11.8%) with an CKMB level >3 × URL, and 12 (14%) with an absolute TnT increase of >0.09 μg/L (p <0.005 for both). In the patients with stable coronary heart disease and post-PCI cardiac markers > 3× URL compared to those without markers elevations, the rate of freedom from death or nonfatal myocardial infarction was 88% for those with TnT elevations versus 99% (p <0.001, log-rank) and 84% for those with CKMB elevations versus 98% (p <0.001, log-rank). Of the patients with acute coronary syndromes, the post-PCI marker levels did not influence the outcomes. In conclusion, in patients with acute coronary syndromes and elevated TnT levels undergoing PCI several days later, ≥20% increases in TnT were more common than absolute increments in the TnT or CKMB levels of >3× URL. Also, periprocedural cardiac marker elevations in patients with acute coronary syndromes did not have prognostic significance.