When carotid stenosis is asymptomatic, patients “should only be considered for revascularization if they have microemboli,” the authors say.
In their study, Dr. J. David Spence, from the Stroke Prevention and Atherosclerosis Research Centre, London, Ontario, Canada, and colleagues compared microemboli rates and cardiovascular events in 199 patients treated in 2000-2002, before intensive medical therapy was common, and 269 patients seen in 2003-2007. All had asymptomatic carotid stenosis >60% by Doppler peak velocity.
They found that 12.6% of patients had microemboli in the earlier era, compared with just 3.7% afterward (p < 0.001).
As microemboli rates fell with intensive medical therapy, plasma lipid control improved and carotid plaque progression slowed. Cardiovascular events were also much less common with intensive medical therapy. Before 2003, the 2-year rate of stroke, death, myocardial infarction, or carotid endarterectomy for symptoms was 17.6%. After 2003, the rate was just 5.2% (p < 0.001).
In both eras, patients with microemboli were at significantly higher risk of the combined endpoint, which occurred in 32.4% of patients with microemboli vs 8.6% of patients without. On Kaplan-Meier analysis, survival free of stroke, death, or myocardial infarction was significantly better for patients treated after 2003 and for those without microemboli.
In fact, with intensive medical therapy, the risk for stroke in patients without microemboli was less than the risk of endarterectomy or stenting, the investigators found.
“This is hugely important,” Dr. Spence told Reuters Health by email, “because at present (approximately) 70% of stenting and endarterectomy in the United States is for asymptomatic carotid stenosis; our findings show that this is inappropriate.”
The crux of intensive medical therapy was to treat the arteries, not just cardiovascular risk factors, according to the authors. Key components included reporting plaque imaging results to patients to encourage lifestyle changes, increasing statins to the maximum tolerated doses regardless of LDL cholesterol level, treatment with an ACE inhibitor or possibly an angiotensin-receptor blocker, and use of metformin or pioglitazone to prevent diabetes in at risk individuals.
Regarding future research, Dr. Spence commented that “the remaining question is whether other methods (besides transcranial Doppler) can reliably identify high-risk asymptomatic carotid stenosis patients who may benefit from surgery or stenting; we have submitted a paper showing that ulceration of carotid plaques identifies…patients whose risk is about half that of patients with microemboli. Other approaches might include imaging of vulnerable plaques by MRI or PET/CT scanning.”
Arch Neurol 2010;67:180-186.