Prehospital thrombolysis: a reappraisal.

Last three decades have witnessed revolutionary changes in the management of patients with ST-elevation acute myocardial infarction (AMI). Despite the advances in pharmacological and interventional treatment, the magnitude of morbidity and mortality from AMI remains quite substantial. It is widely acknowledged that the key factor in the successful treatment of AMI by thrombolytic therapy is the time elapsed between the onset of symptoms and initiation of therapy. A meta-analysis of 22 trials, including more than 50000 patients, showed maximal effectiveness of thrombolytic therapy within the first hour of symptom onset (the golden hour), whereas the benefit was reduced by nearly 50% in the subsequent hour (the Boersma’s curve). An estimated 65, 37, 26 and 29 lives are saved per 1000 patients when treated with thrombolytic therapy within 0-1, 1-2, 2-3 and 3-6 hours respectively. If the patients of AMI can be identified and treated very early after the onset of symptoms, the infarction process can essentially be aborted. Although these data have been recognized for nearly a decade, time-to-thrombolysis in major recent clinical trials still remains stalled at approximately 2.5 to 3 hours after the onset of symptoms. Reasons for delay in the treatment of AMI by thrombolytic therapy include: patient delay, ambulance response time, transportation to hospital, and door to needle time. Public awareness, comprehensive community planning and rapid diagnosis of AMI in the emergency department may partly reduce the delay. However, the time delay factor that is most vulnerable is the transportation time to the hospital. This time can be unacceptably long in rural or congested urban areas. A recent study from a tertiary care hospital of northern India showed that prehospital delay was the most important factor in delayed administration of thrombolytic therapy. Only a third of the patients could reach the hospital within two hours of onset of symptoms. Additional delay of one hour in administering the thrombolytics resulted in only a few patients actually receiving thrombolysis within the first two hours. The obvious step in the continuing effort to shorten timeto-treatment and thus to achieve maximal myocardial salvage is the use of prehospital thrombolysis. Although, this paradigm shift in the treatment of AMI to the prehospital setting rather than in the emergency department of a hospital sounds interesting, yet it raises several clinical, medico-legal and logistical issues.