Patients with high baseline diastolic blood pressure undergoing carotid endarterectomy are at increased risk of stroke, myocardial infarction, or death within 30 days of the procedure, according to results from the International Carotid Stenting Study (ICSS). In a paper published in the European Journal of Vascular and Endovascular Surgery, the authors say that in the context of a single preoperative measurement of blood pressure, diastolic blood pressure might be a better predictor than systolic blood pressure.
The paper was published in the December 2015 issue of EJVES by David Doig (first author), Martin Brown (lead author), from the Institute of Neurology, University College London, UK, and colleagues, on behalf of the ICSS investigators.
ICSS was an international multicentre randomised controlled trial that compared carotid artery stenting with carotid endarterectomy for patients with recently symptomatic carotid stenosis. The study by Doig et al aimed to determine whether there were subgroups of surgical patients in ICSS at higher risk of stroke, myocardial infarction, or death, and whether specific surgical factors were associated with higher risk.
The authors write that “There is variability in surgical technique for carotid endarterectomy and debate remains over optimal processes of care, including perioperative antiplatelet therapy, type of arterial reconstruction (standard, patch, or eversion endarterectomy) and mode of anaesthesia.”
Of the patients randomised in ICSS (1,713), 858 were allocated to surgery. Excluding patients who withdrew consent, crossovers and those who underwent no procedure, endarterectomy was initiated in 821 (96%) patients allocated to the surgery. Of the patients, 70.4% were male and 52.4% were aged over 70 years.
The results showed that within 30 days of the procedure, 27 (3.3%) patients suffered a stroke (21 ischaemic, five haemorrhagic, and one of uncertain type). Three of these strokes were fatal. One patient who had a postoperative non-disabling stroke subsequently had a disabling stroke within 30 days, and another experienced two postoperative non-disabling strokes within 30 days. Of these strokes, 25/27 were ipsilateral to the artery being treated.
Non-fatal myocardial infarction occurred in 5/821 patients (0.6%), and one (0.1%) patient died from another cause. The combined risk of stroke, myocardial infarction, or death within 30 days of their procedure was 4% (33/821). Of these events, 13/33 (39.4%) occurred on day 0—the day of the procedure. Patients undergoing endarterectomy stayed a median of four days before discharge, and 7/33 (21.2%) events occurred on or after their date of discharge.
Risk factors for the combined outcome of stroke, myocardial infarction or death were then analysed using maximum likelihood estimation. Of the baseline demographic and vascular risk factor variables examined, only sex and baseline diastolic blood pressure significantly predicted the risk of the combined outcome of stroke, myocardial infarction, or death within 30 days of carotid endarterectomy, with female patients having approximately double the risk of male patients. After adjustment in a multivariable model, only baseline diastolic blood pressure remained a significant predictor of risk. The investigators note that there was no evidence that the surgical technical variables, including type of anaesthesia, use of a shunt, or type of surgical reconstruction significantly influenced risk.
The authors highlight that the association between raised baseline blood pressure and outcome of surgery has also been demonstrated previously in a systematic review that included patients from the European Carotid Surgery Trial. They comment: “In ICSS, 8.3% of patients undergoing carotid endarterectomy experienced post-procedural hypertension which was associated with higher baseline blood pressure. Other authors have shown an association between preoperative blood pressure, postoperative blood pressure, and stroke or death. However, it is notable that all of these previous studies of blood pressure and the risk of endarterectomy reported only systolic blood pressure and none reported an analysis of diastolic blood pressure, perhaps because of an assumption that systolic blood pressure would be a better predictor of risk.” They suggest that in the context of a single preoperative measurement of blood pressure, diastolic blood pressure might be the better predictor. They add, “Given the consistency of raised blood pressure as a risk factor for perioperative events, consideration should be given to cautious lowering of raised blood pressure prior to endarterectomy. However, it should be borne in mind that overzealous lowering of blood pressure might be hazardous in patients with impaired cerebral perfusion, for example in those with border zone ischaemia or contralateral occlusion.”
In their conclusion, the investigators note that ICSS showed surgery was safer compared with previous randomised trials of symptomatic patients undergoing carotid endarterectomy, “which might have limited ability to detect other predictors of risk”. Nonetheless, they maintain, “cautious attention to blood pressure control after stroke or transient ischaemic attack might help to reduce the risk of serious complications in patients undergoing subsequent carotid endarterectomy”. “The finding that approximately one-fifth of patients with an event experienced this on or after the date of discharge suggests a need for careful post-surgical follow-up and attention to other vascular risk factors,” they say.