Early prediction of ventricular fibrillation using electrocardiographic characteristics in prehospital suspected ST-segment elevation myocardial infarction: a case-control study.

PURPOSE: Our objective was to determine characteristics of electrocardiograms (ECG) that predict ventricular fibrillation (VF) among prehospital patients with suspected ST-segment elevation myocardial infarction (STEMI) in Québec.

METHODS: We performed a matched case-control study of prehospital adult suspected with STEMI. Patients in case group (STEMI/VF+) were matched with controls (STEMI/VF-) for age and sex and then compared for ECG characteristics, including ST-segment elevations (STE) and depressions (STD), duration of interval complexes, general characteristics, and several calculated variables. Logistic regression was used to measure the association between ECG characteristics and VF development.

RESULTS: Overall, 310 prehospital patients with suspected STEMI were included in the analysis (case group, n = 155; control group, n = 155). We confirmed that the presence of TW-pattern complex (OR 7.0, 95% CI 1.55-31.58), premature ventricular contraction (PVC) (OR 5.5, 95% CI 2.04-14.82), and STE in V2-V6 (OR 3.8, 95% CI 1.21-11.74) were electrocardiographic predictors of VF. We also observed that STD in V3-V5 (OR 6.5, 95% CI 1.42-29.39), atrial fibrillation (AF) ≥ 100 beats per minute (bpm) (OR 6.3, 95% CI 1.80-21.90), the combination of STE in V4 and V5, and STD in II, III and aVF (OR 4.8, 95% CI 1.01-22.35), and the presence of STD in ≥ 6 leads (OR 4.2, 95% CI 1.33-13.13) were also associated with VF development. Finally, simultaneous association of 2 (OR 2.3, 95% CI 1.13-4.06) and 3 (OR 11.6, 95% CI 3.22-41.66) predictors showed significant association with VF.

CONCLUSIONS: In addition to some already known predictors, we have identified several ECG findings associated with the development of VF in patients with suspected STEMI. Early identification of patients with STEMI at increased risk of VF should help EMS providers anticipate adverse events and encourage use of defibrillation pads.