Background and purpose: Possible specific risk factors for silent infarcts remain unknown. The aim of this study was to investigate whether risk factors for silent infarcts differ from those for symptomatic infarcts in stroke patients.
Methods: Silent infarcts were defined as asymptomatic infarcts detected on computed tomographic scan in patients free of history of stroke and unrelated to the symptoms and signs of the index stroke. Of 595 consecutive patients with stroke or transient ischemic attacks, 116 (19%) had at least one silent infarct on the first computed tomographic scan performed within 24 hours after onset. They were compared with the 479 remaining patients for cerebrovascular risk factors and for presumed mechanism of stroke by means of the odds ratio method. A discriminant analysis was then performed in the subgroup of 216 patients with ischemic stroke who underwent an exhaustive cardiac and vascular workup.
Results: One hundred forty-one silent infarcts (99% confidence interval [CI], 29% to 41%) and 265 symptomatic infarcts (99% CI, 59% to 71%) were subcortical infarcts smaller than 15 mm. Univariate analysis showed that patients with silent infarcts were more likely to be older than 65 years (odds ratio [99% CI], 1.11 to 3.49) and to have left atrial enlargement on echocardiogram (odds ratio [99% CI], 1.02 to 26.70) and leukoaraiosis (odds ratio [99% CI], 1.39 to 4.21). Discriminant analysis found only two independent risk factors for silent infarcts: left atrial enlargement (P = .007) and age older than 65 years (P = .03); leukoaraiosis was not found to be an independent risk factor (P = .86).
Conclusions: Age and left atrial enlargement are the main risk factors for silent infarcts in patients with ischemic stroke or transient ischemic attacks.