Is symptom to balloon time a better predictor of outcomes in acute ST-segment elevation myocardial infarction than door to balloon time?

Introduction: Current guidelines for the treatment of ST-segment elevation myocardial infarction (STEMI) recommend early revascularization with a door-to-balloon (D2B) time of 90 minutes or less in patients undergoing primary percutaneous coronary intervention (PPCI). The focus of most studies has been D2B time. Because of the large variability in the time between symptom onset and presentation, we sought to determine the effect of symptom-to-balloon (S2B) time on presentation and outcomes as a potentially more clinically relevant parameter. Methods: We conducted a retrospective study of 106 patients who were diagnosed with an acute STEMI, had a documented S2B time and who underwent a PPCI at a tertiary hospital from the period of January 2014 to December 2014. S2B time was defined as the time interval beginning from the episode of chest pain that led the patient to present to the emergency department to the time of the first balloon inflation. We categorized our patients into 2 main groups depending on whether S2B time was greater or less than 240 minutes. They were further subdivided into 2 groups depending on the site of the culprit lesion (left anterior descending LAD vs. non-LAD). Results: There was no difference between the two main groups in regard to the left ventricular ejection fraction (EF) on presentation, length of stay, and readmission with heart failure or chest pain. However, when S2B time was greater than 240 min, there was a statistically significant difference in left ventricular ejection fraction (EF) between LAD and non-LAD stenosis with a mean of 38.4% and 49.3% respectively (P=0.01). No relationship was found between S2B time and gender or age. Conclusion: Although D2B time is a well-established clinical parameter, S2B time may be expected to be a more accurate predictor of outcomes. However, in our study, S2B time of >240 minutes only predicted a significant worse EF (and presumably mortality) when the culprit vessel was the LAD. Further studies are needed to better elucidate the relation of S2B time to clinical outcomes