Yaghi S, P. Moon YP, Mora-McLaughlin C, Willey JZ, Cheung K, Di Tullio MR, et al. Left Atrial Enlargement and Stroke Recurrence: The Northern Manhattan Stroke Study. Stroke. 2015
Left atrial enlargement (LAE) is associated with paroxysmal atrial fibrillation (AF), first-ever ischemic stroke, and detection of AF after cryptogenic stroke. In this report, Yaghi et al evaluated the association of LAE and recurrent stroke.
The authors identified first-ever ischemic stroke patients from the Northern Manhattan Stroke Study (NOMASS). 95% of the enrolled patients completed an electrocardiogram and cardiac telemetry monitoring with their first stroke. Transthoracic echocardiogram (TTE) was completed within three months of the initial infarct and the size of the left atrium (LA) was measured by its anteroposterior diameter. In cases where accurate measurement was not possible, a qualitative assessment was completed – there was excellent agreement between the two methods in the patients that had both done. Normal LA size was categorized into four groups – normal, mild LAE, moderate LAE, and severe LAE. Over a five year follow-up period, stroke occurrence and etiologic subtype (based on the TOAST (Trial of Org 10172 in Acute Stroke Treatment) criteria) was tracked. The primary outcome for this study was total recurrent ischemic stroke and the secondary outcome was combined recurrent cardioembolic or cryptogenic infarct.
529 patients with a first stroke had LA size data available. The mean age was 69 years and average LA diameter was 40.6 mm (standard deviation 6.3 mm). 279 (53%) had normal LA size, 167 (32%) had mild LAE, and 83 (16%) had moderate-severe LAE. Over a median of 4 year follow-up period, 80 patients (15%) had recurrent stroke; 65 were ischemic, of which 13 were cardioembolic and 16 were cryptogenic. LA diameter and moderate-severe LAE were not associated with the risk of total recurrent ischemic stroke. However, those with moderate-severe LAE had a greater risk of recurrent (combined) cardioembolic or cryptogenic stroke (unadjusted model HR 4.35, 95% CI 1.81-10.48). When adjusting for baseline demographics and risk factors (including AF, heart failure) the association was still present (adjusted HR 2.83, 95% CI 1.03-7.81). Mild LAE was not associated with recurrent cryptogenic or cardioembolic stroke. LA diameter (assessed as a continuous variable) was also associated with a higher risk – adjusted HR 1.55 per SD change in LA diameter (95% CI 1.01-2.37). Finally, none of the patients with moderate-severe LAE were found to have AF at time of recurrent infarct.
This study demonstrates that, in patients with ischemic stroke, moderate-severe LAE is an independent risk factor for recurrent cryptogenic or cardioembolic infarct. Evaluation for LAE, along with other clinical markers of atrial dysfunction – N-terminal pro-brain natriuretic peptide, p-wave terminal force in lead V1 on EKG, and paroxysmal supraventricular tachycardia – may identify a population with elevated risk of stroke even in the absence of paroxysmal AF. This may allow for development of improved risk prediction models for risk of stroke and systemic embolism in patients with an “atrial cardiopathy” (of which paroxysmal AF may only be one manifestation). Additionally, this could identify a group of cryptogenic stroke patients who benefit from anticoagulation over antiplatelet therapy. An important limitation to this study was that prolonged AF monitoring was not routinely conducted, and thus occult AF may not have been detected in some of these patients. Also, LA volume was not assessed in this study, which is a better reflection of LA size than its diameter.