Ten year risk of myocardial infarction or unstable angina pectoris in patients with first-ever stroke

Background

Stroke and coronary artery disease (CHD) share common risk factors. The risk of myocardial infarction (MI) in stroke patients is doubled or tripled compared to healthy controls. A recent review found that the annual risks were 2.2% for having a MI after stroke. The purpose of the present study was to estimate the 10-year risk for MI and unstable angina pectoris in an unselected first-ever stroke cohort, as well as to find possible predictors.

Methods

First-ever stroke were registered in Örebro, Sweden, during a 12-month period in 1999-2000. Strokes were divided into subtypes. Stroke severity at baseline was assessed with the National Institute of Health Stroke Scale (NIHSS). Risk factors were registered at baseline. Carotid doppler was performed in patients potentially suitable for carotid surgery (n=82). After a mean follow-up time of ten years, medical records and death certificates were scrutinized for a diagnosis of MI or unstable angina pectoris. The rates of MI were compared with data from The National Board of Health and Welfare (NBHW).

Results

Incidence of MI and unstable angina pectoris: 377 patients had a first-ever stroke during the study period. 45 patients (12%) had either a MI or unstable angina during the follow-up period. At least 25 of these patients (6.6%) died from an acute MI. Figure 1 shows a Kaplan-Meier curve that illustrates the incidence of first-event MI or unstable angina after the index stroke.

MI: comparison with the general population: According to NBWH, the estimated incidence of first-ever MI for men at age 74.5 years in 2004 (mid-study mean age and year) was 1.6 cases / 100 / person-years. This should be compared with our first-event rate of 2.7 / 100 / person-years. For women, at the age of 78.5 years in 2004, the national rate was 1.2 cases / 100 / person-years. The corresponding first-event rate in our study was 2.3 / 100 / person-years. Thus, the RR for stroke patients having a MI is 1.6 for men (95% CI, 1.12-2.37), and 1.9 for women (95% CI, 1.27-2.90), compared to the general population.

Predictors of MI and unstable angina pectoris: We used Cox’s regression to analyze predictors for MI or unstable angina pectoris. The results are shown in Table 1. Hazard ratios in multivariate analysis were: for the combined risk factor CHD (MI, angina pectors, previous CABG/PTCA) 3.52 (95% CI 2.00-6.22), and for peripheral artery disease 6.31 (95% CI 2.19-18.2). Age, sex, hypertension, diabetes mellitus, cigarette smoking, atrial fibrillation, stroke severity, or stroke type, were not significant.

Table 1. Predictors for MI or unstable angina pectoris during a 10-year follow-up period after stroke.

Figure 1. Kaplan-Meier curve showing percentage patients free from MI and unstable angina pectoris during the follow-up period.

Conclusions

Physicians responsible for follow-up of stroke patients must be aware of the relatively high risk of CHD in this group. Only different manifestations of CHD before the stroke, and peripheral artery disease, were significant predictors for MI or unstable angina. Thus, stroke patients with a history of previous CHD, as well as those with peripheral artery disease (such as claudicatio intermittens) should have special attention during follow-up.

References

Touzé E, Varenne O, Chatellier G, Peyrard S, Rothwell PM, Mas JL: Risk of myocardial infarction and vascular death after transient ischemic attack and ischemic stroke: a systematic review and meta-analysis. Stroke 2005;36:2748-2755.
Appelros P, Gunnarsson KE, Terént A. Ten year risk for myocardial infarction in patients with first-ever stroke. A community-based study. Submitted to Cerebrovasc Dis.