NEW ORLEANS – An elevated Framingham Risk Score identified recent ischemic stroke patients at high risk for a myocardial infarction or vascular death over the next 2 years, in a retrospective analysis of data from more than 2,500 stroke survivors without documented coronary heart disease.
If prospective study results confirm this finding, it could establish the Framingham Risk Score (FRS) as an important prognostic assessment for patients with a recent ischemic stroke, Dr. Amytis Towfighi said at the International Stroke Conference. If used this way, the FRS could identify stroke survivors who would benefit from more intensive risk-factor modification, she said.
Dr. Amytis Towfighi
"Considering every stroke to be a coronary risk equivalent could expose patients with a low risk for subsequent coronary events to unnecessary treatment," said Dr. Towfighi, a neurologist at the University of Southern California in Los Angeles and director of the acute neurology/acute stroke unit at Rancho Los Amigos National Rehabilitation Center in Downey, Calif.
"Unlike coronary atherosclerosis, there are lots of different causes of stroke, including nonatherosclerotic mechanisms.
"Many stroke survivors harbor asymptomatic coronary heart disease, and beyond the acute period they are often at higher risk for cardiac death than for recurrent cerebrovascular events," she said. Identifying patients with high FRSs of 20% or greater could flag those who would benefit from treatment with a beta- blocker; coronary diagnostic imaging; coronary revascularization; or more intensive vascular risk reduction by reducing body mass index, lowering triglycerides, exercising tighter diabetes management, and smoking cessation.
"Today, the FRS is usually not calculated for stroke patients," Dr. Towfighi said in an interview. "Part of the issue is that the FRS was initially developed for people who had not yet had a [cardiovascular] event, so it has not been studied in patients who had a stroke. We didn’t know going into our study whether or not a high FRS would predict a myocardial infarction or vascular death in patients who had a stroke."
To test whether the FRS could help stratify coronary risk in stroke patients, Dr. Towfighi and her associates analyzed data collected from 3,509 patients who had a recent ischemic stroke and who participated in the Vitamin Intervention for Stroke Prevention trial during 1996-2003 (JAMA 2004;291:565-75). The analysis primarily focused on the 2,547 patients from this group who did not have documented coronary heart disease at the time of their enrollment.
Calculation of the FRS for these patients identified 933 (37%) with a score of 20% or greater, and 1,614 (63%) with a score of less than 20%.
The researchers then tallied the rates of myocardial infarction, vascular death, or stroke in these two subgroups during 2 years of follow-up, and compared the rates between the two FRS groups in a multivariate analysis that controlled for baseline differences in age, race, prior stroke, body mass index, heart failure, carotid endarterectomy, stroke severity, alcohol use, low-density lipoprotein cholesterol, triglyceride levels, mean systolic blood pressure while in the study, antidyslipidemia drug treatment, antithrombotic drug treatment.
In this analysis, patients with an FRS of 20% or greater at baseline had a 2.8-fold increased risk for a myocardial infarction during 2 years of follow-up compared with patients with a lower FRS. The risk of vascular death during follow-up was 80% higher in the high-FRS subgroup than in patients with a lower score. However, a higher FRS had no link with an increased risk for a subsequent stroke.
In addition, the FRS components most strongly linked to subsequent myocardial infarction risk were smoking, which raised the risk by 70%, and diabetes, which doubled the risk.
These findings are not conclusive because they came from a retrospective analysis and may have been influenced by unmeasured confounding. Ideally, the findings need confirmation in a prospective study, Dr. Towfighi said.
Despite this limitation, Dr. Towfighi noted that she and her associates at Rancho Los Amigos now calculate an FRS for their stroke patients "because we feel it’s useful," she said at the meeting, which was sponsored by the American Heart Association.
Dr. Towfighi said that she had no disclosures.