Impact of a normal or non-specific admission ECG on the treatment and early outcome of patients with myocardial infarction in Swiss hospitals between 2003 and 2008

Abstract

Diagnosis of acute myocardial infarction (AMI) rests upon clinical, electrocardiographic and biochemical parameters. Previous studies reported AMI patients who present with non-specific ECGs. To examine clinical or demographic features of AMI patients presenting with or without ECG changes and assess the impact of these ECGs on treatment and outcome. Using the AMIS Plus data, patients admitted between 2003 and 2008 with a definite diagnosis of AMI (clinical symptoms, elevated troponin levels) were stratified according to the admission ECG into group 1 with normal/non-specific ECGs and group 2 with ECG changes. Of 14 957 patients, 1085 (7.3%) belonged to group 1 and 13 872 (92.7%) to group 2. There were no differences between the two groups in age (65.9 yr vs. 65.4 yr), gender (28% female), diabetes (19% vs. 18%), hypertension (61% vs. 59%), family history (35% vs. 33%) or smoking (37% vs. 38%). Dyslipidaemia (62% vs. 56%; p <0.001), history of CAD (39% vs. 35%; p = 0.023) and obesity (BMI >30 kg/m2 [23% vs. 19%; p = 0.003]) were more frequent in group 1 who were admitted longer after symptom onset (280 min vs. 230 min). Patients in group 1 were exposed to less intensive pharmacological and interventional treatments (aspirin [93.6% vs. 95.3%; p = 0.012], clopidogrel [70% vs. 73%; p = 0.046], unfractionated heparin [59% vs. 65%; p <0.001], ACE inhibitors or angiotensin II antagonists [46% vs. 53%; p <0.001]). However, therapy with beta-blockers (72% vs. 70%), statins (75% vs. 76%) and nitrates (59% vs. 57%) did not differ between groups. Patients in group 1 underwent PCI significantly less frequently (69% vs. 77%) with a longer hospital delay (589 min vs. 96 min). No differences were found for reinfarction (both 1.4%) and a cerebrovascular event (0.4% vs. 0.8%). Cardiogenic shock (5% vs. 2%; p <0.001) and mortality during hospitalisation were higher in group 2 (6% vs. 3%; p <0.001). A normal/non-specific ECG on admission was not an independent predictor of in-hospital mortality (OR 0.61; 95% CI 0.34-1.11; p = 0.104). Despite less intensive treatment, AMI patients who presented with a normal/non-specific ECG developed cardiogenic shock less frequently during their hospitalisation and had a lower crude mortality rate compared to those with ECG changes on admission. Nevertheless, reinfarctions and cerebrovascular events occurred evenly in all AMI patients, regardless of their admission ECG.