Left atrial appendages (LAA) are significantly enlarged in more than half of patients with cryptogenic stroke/transient ischemic attack (TIA) and may contribute to the pathogenesis of stroke in patients considered to have cryptogenic stroke after conventional evaluation, according to a study published online Nov. 4 in PLOS ONE.

Strokes are the leading cause of long-term disability and cause 10 percent of all deaths. Ischemic strokes that don’t have well-defined causes are categorized as cryptogenic, and comprise 30 to 40 percent of strokes in stroke registries.

“Most cardiac thrombi originate from the left atrial appendage,” wrote Mikko Taina, MD, of Finland’s Kuopio University Hospital, and colleagues. “An enlarged LAA may predispose to blood coagulation due to slow flow velocity. MRI results have shown enlarged LAA in stroke/TIA patients with atrial fibrillation (AF).”

Using this research as a springboard, the authors created a study aimed to determine if increased LAA and/or left atrium (LA) volume detected with cardiac CT (cCT) establishes a risk factor in cryptogenic stroke patients.

Participants included 82 stroke/TIA patients with a diagnosis of cryptogenic stroke after extensive radiological and cardiological investigations. The cases were defined using the TOAST criteria modified by European Association of Echocardiography recommendations for defining cardiac sources of embolism. Forty age- and sex- matched subjects without cardiovascular diseases were chosen as comparable control counterparts.

Once the LAA volume adjusted for body surface area was measured three-dimensionally by tracing the LAA borders on electrocardiogram-gated CT slices, results revealed that LAA volume was 67 percent larger in cryptogenic stroke/TIA patients. Overall, 55 percent of this demographic had enlarged LAA.

“Assessment of LAA and LA volumes may be valuable in the etiological work-up of stroke/TIA without defined etiology. Based on measurements in the control population, mid-diastolic LAA volume larger than 5.6 ml/m² indicates LAA enlargement,” wrote Taina and colleagues. “Currently, further examination for asymptomatic AF of patients with an enlarged LAA in cCT may be recommended, since AF as an etiology for stroke/TIA may significantly affect treatment of these patients.”