Article Text


Thrombolytic therapy for acute myocardial infarction
  1. Department of Medicine, UT-Houston Medical School
  2. 6431 Fannin, Suite 1.134 MSB, Houston, TX 77030, USA
    1. A KELION
    1. Department of Cardiology, John Radcliffe Hospital, Oxford OX3 9DU, UK

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      Sir,The title of a recently published article ‘The effect of reduction of door-to-needle time on the administration of thrombolytic therapy for acute myocardial infarction’1implies that a reduction in door-to-needle time led to a higher proportion of eligible patients receiving thrombolysis and the authors seem to make a similar conclusion. It is difficult to know how this conclusion was reached. From the data given by the authors it seems that the prime reason for increased uptake of thrombolysis in the second group was education of the junior doctors and nurses looking after these patients rather than a reduction in door-to-needle time. The result shows that all eligible patients who received thrombolysis, received it on presentation, ie, 63% in the first group and 100% in the second group. Also, only patients thrombolysed on the basis of an admission electrocardiogram and who were eligible for thrombolysis on admission were included in the analysis of door-to-needle time and accuracy of treatment. So how did the reduction in door-to-needle time increase the proportion of patients being thrombolysed, especially when patients in the second group arrived 3 hours later than those in the first one and the proportion of patients eligible for thrombolysis decreased from 38/66 (57%) to 30/76 (39%) in the second group? Perhaps the most important factor may have been the presence of a higher number of elderly patients in the second group with far more elderly patients being thrombolysed which may be due to an increased access to the coronary care unit (CCU) for this population. Only a minority of elderly patients with myocardial infarction (MI) are admitted to the CCU, where thrombolysis is given in most hospitals.2 In the US, patients older than 75 years are 2.5 times more likely not to be admitted to CCU than the younger population, even when the physician's admitting diagnosis is MI.3 Also, general awareness amongst the people involved in the care of such patients is an important factor; an improvement in uptake of thrombolysis following education of the junior doctors and nurses has been shown previously.4 Another factor may have been the presence of a slightly higher proportion of male patients in the second group. Even in patients eligible for thrombolysis, increasing age and female sex is independently associated with less likelihood of receiving thrombolysis.5

      If we are to improve the outcome of MI then all eligible patients should be thrombolysed, irrespective of age and sex, and one practical way of achieving higher thrombolysis rates is to admit more elderly patients to the CCU, for once admitted to CCU increasing age no longer seems to be an independent predictor of low thrombolysis.6Also, aggressive management of elderly patients (even those older than 80 years) admitted to CCU has resulted in improved survival in these patients.7 This article highlights the fact that all patients suspected of having ischaemic cardiac pain should be initially admitted to CCU, for at least the first 24 hours. Another study has shown that approximately 77% of patients admitted to medical wards who eventually develop MI do so within 24 h.8 Also, those who develop MI as in-patients on wards are treated less aggressively, are less often thrombolysed, and when thrombolysed, there is a considerably greater delay than for those admitted directly to CCU.8

      In the treatment of MI, ‘time is muscle’ and delay is the enemy to successful thrombolysis. If optimal treatment of MI is to be achieved, then thrombolysis should be initiated in the emergency department and all patients with suspected MI should be admitted to the CCU, irrespective of age. Around 60% of patients with MI are older than 65 years of age.5 By disregarding age or sex as selection factors, thrombolytic treatment rates could be raised from 35% to 55% of all patients admitted with acute MI.5


      This letter was shown to the authors who responded as follows:

      Sir,Our study compares patterns of thrombolytic treatment in a district general hospital CCU before and after implementation of a structured management policy. As stated in the paper, although the primary aim was to reduce door-to-needle times, “we hoped that a generally increased awareness of the importance of thrombolysis would lead to a higher proportion of eligible patients receiving the appropriate treatment.” The results demonstrate that our intervention resulted in the treatment of more eligible patients with less delay.

      Clearly, reducing door-to-needle times per se cannot have a direct causal effect on the proportion of eligible patients being thrombolysed. Rather, as we point out in the paper, it is “an important beneficial result of theeffort to lower door-to-needle times”. Education about the indications and absolute contraindications for thrombolysis is an important part of our improved management. We believe that our paper confirms this and emphasises the importance of carefully considering thrombolytic therapy for all patients presenting with acute myocardial infarction.

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