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

BACKGROUND: Diagnosis of acute myocardial infarction (AMI) rests upon clinical, electrocardiographic and biochemical parameters. Previous studies reported AMI patients who present with non-specific ECGs. OBJECTIVES: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.