ECG interpretation in ST-elevation myocardial infarction: pattern recognition or caliper measurements?

In the setting of ST-elevation myocardial infarction (MI), the electrocardiogram (ECG) is essential in the diagnosis and evaluation of patients. The ECG is used to quickly risk stratify and subsequently implement the best treatment strategy for the individual patient. During this acute phase, the cardiologist or emergency department physician interprets the electrocardiogram focusing not only on the presence of ST elevation but also on the characteristics that provide important prognostic data on survival after MI. Heart rate, atrioventricular conduction, fascicular block, bundle branch block and the degree of ST-segment deviation have all been shown to influence survival after MI.1 For the more experienced physician, this process is facilitated by pattern recognition. However, it has now become clear that much more prognostic information, such as the likelihood of 30-day mortality, can be better explored with quantitative techniques. This was first realised by Schroder and colleagues, who performed very elegant studies in the 1990s, which demonstrated that the sum of the degree of ST elevation was prognostic of outcomes.2 More importantly, they also found that the proportion of ST segment resolution was also associated with of the degree of reperfusion and therefore prognosis as early as 90 min after receiving fibrinolytic therapy. These findings were later confirmed in larger clinical trials.3 This approach of measuring the sum and degree and resolution of ST segments is now common practice, and thus has opened the door for more careful measurements of the ECG.

More recently, cardiologists have raised the question of whether QRS duration is a robust risk stratifier in diverse cardiovascular disease populations, including patients with heart failure, with dyssynchrony and at increased risk of sudden cardiac death.4 5 The …