Supplement to the AHA Guidelines for the Management of Transient Ischemic Attacks
To the Editor:
I read with interest the recent supplement to the guidelines on management of patients with transient ischemic attacks.1 However, with regard to carotid endarterectomy (CE), I was disappointed that Albers et al made no attempt to interpret the clinical trial results in the context of real-world surgical performance.
For example, in the updated section on CE for 50% to 69% symptomatic stenosis, the authors state that symptomatic patients with 50% to 69% benefit from surgery and that these patients should be considered for CE. However, should clinicians conclude that because patients in the surgical arm of the North American Symptomatic Carotid Endarterectomy Trial (NASCET) had a marginal statistically significant benefit (P=0.045) that this result is clinically meaningful and that this can be routinely achieved in clinical practice?
One must keep in mind that the benefit of surgery in the 50% to 69% group was very modest. For the important clinical outcome of disabling, ipsilateral stroke, the absolute difference between the medical and surgical groups was only 4.4% at 5 years, or less than 1% per year.2 This modest result was achieved in the ideal setting of low-risk patients being operated on by surgeons screened for their excellence. In NASCET as a whole, the perioperative mortality was 1.1% and the stroke and death rate was 6.5%.
In terms of the real world, Wennberg et al3 analyzed CE results in over 100 000 Medicare beneficiaries in 1992–1993 and found the perioperative mortality at an average volume hospital to be 1.9%. This was in a mixed symptomatic/asymptomatic cohort. Had the analysis been restricted to symptomatic patients only, the perioperative mortality would likely have been even higher.
With regard to other recent studies, Hartmann et al4 studied symptomatic patients over a two year period at their hospital and the stroke/death rate was 11.1%. In the Carotid and Vertebral Artery Transluminal Angioplasty Study (CAVATAS), the rate of disabling stroke and death in the CE group was 5.9%, almost 3 times as high as the NASCET figure (M. Brown, personal communication, 1999).
With these considerations, I think that the extremely modest benefit seen in the high-moderate NASCET group is not generalizable and that these patients will not benefit from CE in the real world. The comments of Wennberg et al3 on the utilization of CE should be heeded when these authors stated that “the caution called for by those advocating restraint is warranted.”
- Copyright © 2000 by American Heart Association
Response to Dr Chaturvedi:
We thank Dr Chaturvedi for his comments regarding the carotid endarterectomy recommendations in the recently published American Heart Association Guidelines for the Management of Transient Ischemic Attacks. We agree that the efficacy of therapies in the community setting, medical or surgical, may differ from the results obtained in carefully controlled clinically trials. Application of clinical trial results to clinical practice is always problematic and requires clinical judgement. We also agree that surgical morbidity and mortality rates may be higher in the “real world” than those achieved in the North American Symptomatic Carotid Endarterectomy Trial (NASCET). However, the stroke and death rate is also likely to be higher in medically managed patients in a routine practice setting due to variations in the management of comorbid risk factors, decreased emphasis on medical compliance, and less frequent systematic follow-up. In addition, patients selected for participation in clinical trials frequently have relatively favorable outcomes in both active treatment and control groups. Therefore, we do not think it is valid to compare the surgical morbidity and mortality rates in populations such as Medicare beneficiaries with the rates observed in a clinical trial. It is also noteworthy that the NASCET trial enrolled patients with moderate carotid stenosis at 106 diverse clinical sites; therefore, the complication rates reported do exist in the “real world.”
Our evidence-based guidelines rely heavily on scientific data from randomized clinical trials. The NASCET and European Carotid Surgery Trial (ECST) provide the highest quality data regarding the risks and benefits of carotid endarterectomy for patients with moderate symptomatic stenosis. The guidelines state that carotid endarterectomy should be “considered” for patients with a recent transient ischemic attack or minor stroke with ipsilateral carotid stenosis of 50% to 69%, but that “the absolute benefit of surgery is relatively small for these patients.” The degree of benefit “is highly dependent on surgical risk” and “consideration should be given to clinical features that influence stroke risk and surgical morbidity.” These features should include the overall health and gender of the patient, the nature of the neurological symptoms, the degree of stenosis, and the availability of a surgical team with a demonstrated low perioperative morbidity and mortality rate.