Hans Mickley

Classification of Myocardial Infarction: Frequency and Features of Type 2 Myocardial Infarction

BACKGROUND The classification of myocardial infarction into 5 types was introduced in 2007 as an important component of the universal definition. In contrast to the plaque rupture-related type 1 myocardial infarction, type 2 myocardial infarction is considered to be caused by an imbalance between demand and supply of oxygen in the myocardium. However, no specific criteria for type 2 myocardial infarction have been established. METHODS We prospectively studied unselected hospital patients who had cardiac troponin I measured on clinical indication. The diagnosis and classification of myocardial infarction were established, and the frequency and features of type 2 myocardial infarction were investigated by use of novel developed criteria. RESULTS From January 2010 to January 2011, a total of 7230 consecutive patients who had cardiac troponin I measured were evaluated, and 4499 patients qualified for inclusion. The diagnosis of myocardial infarction was established in 553 patients, of whom 386 (72%) had a type 1 myocardial infarction and 144 (26%) had a type 2 myocardial infarction. Patients in the group with type 2 myocardial infarction were older and more likely to be female, and had more comorbidities. The proportion of patients without significant coronary artery disease was higher in those with type 2 myocardial infarction (45%) than in those with type 1 myocardial infarction (12%) (P < .001). Tachyarrhythmias, anemia, and respiratory failure were the most prevalent mechanisms causing type 2 myocardial infarction. CONCLUSIONS In a cohort of patients with myocardial infarction who were admitted consecutively through 1 year, the category of type 2 myocardial infarction comprised one fourth when diagnosed by the use of newly developed criteria. Approximately half of patients with type 2 myocardial infarction had no significant coronary artery disease.

Rapid Estimation of Left Ventricular Ejection Fraction in Acute Myocardial Infarction by Echocardiographic Wall Motion Analysis

Echocardiographic estimates of left ventricular ejection fraction (ECHO-LVEF) in acute myocardial infarction (AMI) were obtained by a new approach, using visual analysis of left ventricular wall motion in a nine-segment model. The method was validated in 41 patients using radionuclide ventriculography (RNV) and contrast ventriculography measurements of LVEF for comparison. ECHO-LVEF from the 41 patients correlated well with the reference methods (y = 1.5x - 14.7, r = 0.93; linear regression analysis; 95% confidence limit for a single determination of ECHO-LVEF was 17.2). Interobserver variability by linear regression was r = 0.89, SEE = 7.1 with a mean difference between paired observations of -1.5 +/- 6.9 (SD). In a random sample of 18 patients (45 observations), ECHO-LVEF allowed separation between RNV-LVEF values greater than or equal to 40 and less than 40, representing low and high risk groups following AMI. Thus, the results showed that simple, readily available wall motion-derived estimates of LVEF were as closely associated with LVEF measured by standard reference methods as were previously published, more cumbersome, planimetric echocardiographic methods. Reporting on global LVEF function in LVEF units rather than in nonstandardized wall motion scores of index values may facilitate intra- and interhospital communication and the use of optimized echocardiographic risk stratification after AMI.

Cardiac troponin T and CK-MB mass release after visually successful percutaneous transluminal coronary angioplasty in stable angina pectoris

The incidence of cardiac troponin T (Tn-T) and creatine kinase (CK) isoenzyme MB mass release was studied in 23 patients with stable angina pectoris undergoing visually successful percutaneous transluminal coronary angioplasty (PTCA). Serial blood samples were drawn for measurement of serum Tn-T, CK-MB mass, total CK activity, CK-MB activity, and lactate dehydrogenase isoenzyme (LD-1). ST segment monitoring was carried out during PTCA and for the following 24 hours. None of the patients showed electrocardiographic (ECG) evidence of myocardial infarction. However, Tn-T was elevated in three patients (0.23 to 1.32 micrograms/L), and in these three and an additional three patients CK-MB mass was also elevated (7.0 to 27.5 micrograms/L). Total CK activity and LD-1 were only elevated in one of these six patients. None had elevated CK-MB activity. ST segment depression on ECG recording was not predictive of Tn-T or CK-MB mass release. Patients with elevated Tn-T or CK-MB mass did not differ with respect to demographic data, stenosis characteristics, or in the PTCA procedure. We conclude that CK-MB mass uncovers clinically and ambulatory electrocardiographically inapparent severe myocardial ischemia/minor myocardial damage (microembolization) in 26% (6 of 23) of patients after visually successful PTCA; 13% (3 of 23) had elevated Tn-T, indicating minor myocardial damage. The application of these markers in the future could be of considerable value for determining the efficacy of coronary angioplasty and atherectomy, as well as for drug therapy in connection with such procedures.

Mortality rate in type 2 myocardial infarction: Observations from an unselected hospital cohort

BACKGROUND The classification of myocardial infarction into 5 types was introduced in 2007. The prognostic impact of this universal definition, with particular focus on type 2 myocardial infarction, has not been studied prospectively in unselected hospital patients. METHODS During a 1-year period, all hospitalized patients having cardiac troponin I measured were considered. The diagnosis of a myocardial infarction was according to the universal definition, and specified criteria were used in the classification of type 2 myocardial infarction. Follow-up was at least 1 year, with mortality as the end point. RESULTS A total of 3762 consecutive patients were studied, of whom 488 (13%) had a myocardial infarction. In 119 patients a type 2 myocardial infarction was diagnosed. After a median of 2.1 years (interquartile range, 1.6-2.5 years), 150 patients had died, with a mortality rate of 49% (58/119) in those with type 2 myocardial infarction and 26% (92/360) in those with type 1 myocardial infarction (P < .0001). In a multivariable Cox regression analysis the following variables were independently associated with mortality: current or prior smoker, high age, prior myocardial infarction, type 2 myocardial infarction, hypercholesterolemia, high p-creatinine, and diabetes mellitus. The multivariable-adjusted hazard ratio for type 2 myocardial infarction was 2.0 (95% confidence interval, 1.3-3.0). With shock as the only exception, mortality was independent of the triggering conditions leading to type 2 myocardial infarction. CONCLUSIONS Mortality in patients with type 2 myocardial infarction is high, reaching approximately 50% after 2 years. Further descriptive and survival studies are needed to improve the scientific evidence on which treatment of type 2 myocardial infarction is based.

Prevalence and prediction of silent ischaemia in diabetes mellitus: a population-based study

OBJECTIVES The aim of the study was to estimate the prevalence of silent ischaemia in diabetic subjects in the population, to compare the prevalence of silent ischaemia in diabetics and non-diabetics and to attempt to predict the presence of silent ischaemia in diabetic subjects. METHODS A random sample of 120 users of insulin and 120 users of oral hypoglycaemic agents aged 40-75 years living in the Danish municipality of Horsens were asked to participate in the study. Corresponding to the youngest half of the sample two non-diabetic controls were randomly selected from the Central Population Register. ST-depression of horizontal or descending character of at least 0.1 mV measured 80 ms after the J-point on either exercise ECG or Holter ECG was considered indicative of myocardial ischaemia. Angina pectoris was considered present if the Rose questionnaire was positive, or chest pain was registered simultaneously with ECG evidence of ischaemia. Individuals with ischaemia, but without angina pectoris, were defined as persons with silent ischaemia. RESULTS Seventy-four percent of the invited group were included. The observed prevalence of silent ischaemia in diabetics was 13.5% (95% CI = 8.5-19.8%). No association was found between silent ischaemia and gender (P = 0.83) or diabetes type (P = 0.67). In the group of diabetics who had controls, the prevalence was 11.4%, and among the controls the prevalence was 6.4% (OR = 1.87, one-sided P = 0.079). Systolic blood pressure was highly predictive of silent ischaemia in the diabetic subjects (P = 0.005). No predictive value could be shown for other variables. CONCLUSION This is the first population-based study of silent ischaemia in diabetes. The prevalence of silent ischaemia in diabetic subjects was 13.5%. The frequency of silent ischaemia did not differ significantly between diabetics and non-diabetics. Systolic blood pressure was predictive of silent ischaemia in diabetes.

Discrepancy between coronary artery calcium score and HeartScore in middle-aged Danes: the DanRisk study

Background: Coronary artery calcification (CAC) is an independent and incremental risk marker. This marker has previously not been compared to the HeartScore risk model. Design: A random sample of 1825 citizens (men and women, 50 or 60 years of age) was invited for screening. Methods: Using the HeartScore model, the 10-year risk of fatal cardiovascular events based on gender, age, smoking, systolic blood pressure, and total cholesterol was estimated. A low risk was defined as <5%. The CAC score was calculated from a non-contrast enhanced cardiac-CT scan and given in Agatston U. Results: A total of 1257 (69%) of the invited subjects were interested in the screening. Due to previous cardiovascular disease or diabetes mellitus, 101 were excluded. Of the remaining 1156, 47% were men and 53% women; one half were 50 years old and the other half 60 years old. A low HeartScore was found in 901 of which 334 (37%) had CAC. A high HeartScore was recorded in 251 of which 80 (32%) did not have any CAC. High HeartScores and CAC were significantly more common in males than females. Conclusions: CAC is common in healthy middle-aged Danes with a low HeartScore, and, on the contrary, high-risk subjects very frequently do not have CAC. The therapeutic and prognostic implications of these observations remain to be clarified.

Serial measurements of N-terminal pro-brain natriuretic peptide after acute ischemic stroke

Background: The exact time-course of N-terminal pro-brain natriuretic peptide (NT-proBNP) and the prognostic importance in the immediate phase of ischemic stroke have not been established. Methods: NT-proBNP was measured daily from admission to day 5 and again at 6-month follow-up in 250 consecutive patients with acute ischemic stroke. Results: NT-proBNP peaked the day after onset of symptoms (p = 0.007) followed by a decrease until day 5 (p = 0.001, ANOVA). At 6-month follow-up the difference in the level of NT-proBNP was unchanged compared to day 5 (p = 0.42). NT-proBNP levels ≧615 pg/ml at day 2 after onset of symptoms was associated with 6-month mortality. Conclusion: NT-proBNP peaks the day after onset of symptoms in patients with acute ischemic stroke. A single measurement of NT-proBNP appears to be an indicator of 6-month mortality.

Osteoprotegerin concentrations and prognosis in acute ischaemic stroke.

Abstract.  Jensen JK, Ueland T, Atar D, Gullestad L, Mickley H, Aukrust P, Januzzi JL (Odense University Hospital, Denmark; Rikshospitalet, Oslo, Norway; Massachusetts General Hospital, USA). Osteoprotegerin concentrations and prognosis in acute ischaemic stroke. J Intern Med 2010; 267: 410–417.

The antiplatelet effect of clopidogrel is not attenuated by statin treatment in stable patients with ischemic heart disease

Recent studies suggest that cytochrome P450 (CYP) 3A4 metabolized statins attenuate the antiaggregatory effect of clopidogrel. We evaluated how CYP3A4 metabolized statins and non-CYP3A4 metabolized statins influence platelet aggregation when given concomitantly with clopidogrel. Sixty-six stable patients with ischemic heart disease were included in this parallel group study. All patients were on clopidogrel and aspirin. Thirty-three patients received a CYP3A4 metabolized statin (simvastatin or atorvastatin), and 33 were treated with a non-CYP3A4 metabolized statin (pravastatin). The antiplatelet effect of clopidogrel was assessed at inclusion and 21 days after statin discontinuation. Platelet function was evaluated by two methods 1) optical platelet aggregometry after stimulation with 20 and 30 microM ADP, and 2 and 4 mg/l collagen, respectively, 2) a Platelet FunctionAnalyzer-100. The primary effect measure was final platelet aggregation after stimulation with 20 microM ADP. No difference was observed between patients treated with a CYP3A4 metabolized statin and patients receiving a non-CYP3A4 metabolized statin (30% point (7-42) versus 20% point (9-32), p = 0.83). Platelet aggregation was not improved by discontinuation of statins for 21 days. Indeed, we found that statin treatment given concomitantly with clopidogrel resulted in an improved platelet inhibition when compared to clopidogrel given alone. The antiplatelet effect of clopidogrel is not attenuated by concomitant treatment with a CYP3A4 metabolized statin in patients with clinical stable ischemic heart disease.

Clinical Characteristics and Outcomes of Patients with Myocardial Infarction, Myocardial Injury, and Nonelevated Troponins

BACKGROUND Cardiac troponins have emerged as the preferred biomarkers for detecting myocardial necrosis and diagnosing myocardial infarction. However, current cardiac troponin assays do not discriminate between ischemic and nonischemic causes of myocardial cell death. Thus, when an increased troponin value is encountered in the absence of obvious myocardial ischemia, a careful search for other clinical conditions is crucial. METHODS In 2010 to 2011, we prospectively studied hospitalized patients who had cardiac troponin I measured on clinical indication. An acute myocardial infarction was diagnosed in cases of a cardiac troponin I increase or decrease pattern with at least 1 value >30 ng/L (99th percentile) together with myocardial ischemia. Myocardial injury was defined as cardiac troponin I values >30 ng/L, but without signs or symptoms indicating overt cardiac ischemia. Patients with peak values ≤30 ng/L were classified as nonelevated cardiac troponin I. Follow-up was at least 3 years with all-cause mortality as the sole clinical end point. RESULTS A total of 3762 patients were included. Of these, 488 (13%) had acute myocardial infarction, 1089 (29%) had myocardial injury, and 2185 (58%) had nonelevated cardiac troponin I values. Patients with myocardial injury frequently presented with dyspnea, were older, and had more comorbidity than patients in the 2 other groups. During a median follow-up of 3.2 years, 1342 patients died. Mortality differed significantly between groups: 39% in those with myocardial infarction, 59% in those with myocardial injury, and 23% in those with nonelevated cardiac troponin I (log-rank test; P < .0001). No significant difference in mortality between patients with type 2 myocardial infarction and patients with myocardial injury was observed (63% and 59%, respectively). CONCLUSIONS Patients with myocardial injury are older and have more comorbidity than those with acute myocardial infarction. Both groups exhibit a poorer prognosis than patients with nonelevated cardiac troponin I values. Of note, a very high long-term mortality is observed in patients with type 2 myocardial infarction and patients with myocardial injury.