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Editor,—We read the above original article of McNulty et al with interest particularly the antithrombotic management algorithm in fig 1.1 There is no mention of the time when the retrospective study was conducted. As it was submitted in January 2000 we assume that the study was conducted sometime in 1999.
The algorithm originally published in 19962 should be considered outdated in 1999/2000 because: first, in atrial fibrillation an age of 75 years or older is a high risk factor for thromboembolism to qualify for long term anticoagulation.3 Secondly, a large left atrium in patients with atrial fibrillation but without mitral valve disease is not an independent risk factor for thromboembolism .3 Therefore left atrium size of more than 4.5 cm per se should not be used to decide for long term anticoagulation in these patients. Thirdly, patients with atrial fibrillation who are below 65 years of age but with hypertension/ischaemic heart disease/ diabetes mellitus are at high risk and should be given warfarin, not aspirin.3 Fourthly, patients with atrial fibrillation at high risk of thromboembolism in whom warfarin and aspirin are contraindicated should be considered for clopidogrel or at least dipyridamole. In patients with atherosclerotic vascular disease, clopidogrel has been shown to be more effective than aspirin in reducing risk of ischaemic stroke, myocardial infarction or vascular death without increasing adverse effect.4Patients intolerant of aspirin should be given modified release dipyridamole or clopidogrel.5
We believe that using such improved management protocol for atrial fibrillation either for audit purpose or clinical practice, is likely to further reduce the risk of ischaemic stroke.
Drs McNulty, Hutchinson, and Hardy respond:
We read the three letters above with much interest and would like to address the issues raised by each, in turn. We appreciate the update on current knowledge of stroke prevention provided by Conway and Lip, which we have followed as it appears in the literature. Obviously we were unable to use these revised guidelines as our original audit predated the publication of this revision.1-1 When the audit was conceived we did debate whether to include paroxysmal atrial fibrillation (PAF) as well as sustained atrial fibrillation in our study but at that time the “jury was still out” as to whether PAF carried the same risk—so we chose to audit sustained atrial fibrillation only; again we appreciate the update on PAF.1-2
In response to Lairikyengbam et al—as stated our paper was submitted in January 2000. The auditing process took over a year to complete, as it takes time to accumulate 370 patients with atrial fibrillation, retrieve and extensively review case notes, and analyse the data. It should also be noted that there was a gap of six months between the two audits reported to allow for an education programme. Therefore when the revised guidelines were published in July 19991-3 the audit was completed.
Finally, the response from Murphy and Casey seems to raise two questions and a possible word of warning. The questions regard whether our patients had therapeutic INR control and what was the incidence of major adverse events in our group—unfortunately audit (and reaudit, in the case of our report1-4) consists of snapshots of current management. In the case of lifelong intervention with warfarin therapy, audit would be an inappropriate tool to measure their two concerns and perhaps a prospective study would be a more useful way of answering their questions. We note a recent report by Guptaet al studying elderly patients with atrial fibrillation on warfarin.1-5 The last five prothrombin readings were analysed, and it was found that only 9% of these patients were not adequately warfarinised; only four major bleeds occurred over 263 treatment years in this particular treatment group. They also raise concerns regarding the increased resources needed to deliver the current published recommended guidelines. We agree that treating more patients with warfarin would increase demands on haematology laboratory resources; however, we (like most people involved in this field) believe that this is offset by the potential reduction in the demands made upon stroke and general inpatient beds, physiotherapy, occupational therapy, and all the other resources which are consumed after a stroke.
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