In AF, Complex LAA Shape Independently Predicts Thrombus

February 19, 2014

IBARAKI, JAPAN — Complex left atrial appendage (LAA) morphology was a risk factor for LAA thrombus in a prospective series of patients with atrial fibrillation (AF), independent of clinical predictors and echocardiographic markers of blood stasis[1].

For example, the patients with LAA thrombi were overwhelmingly more likely to show three or more LAA lobes by three-dimensional transesophageal echocardiography (3D TEE), while those without LAA thrombi were more likely to show only one or two lobes.

The findings, according to the authors, led by Dr Masayoshi Yamamoto (University of Tsukuba, Ibaraki, Japan), suggest that "LAA morphology might be a congenital risk factor for LAA thrombus formation in patients with AF."

It should therefore be considered alongside other well-known predictors such as CHADS2 score, left atrial volume, and degree of spontaneous echo contrast for diagnosing LAA thrombus and when considering anticoagulation management, according to the group, whose study is published online February 12, 2014 in Circulation: Cardiovascular Imaging.

The LAA is considered the most common source of thrombi in cardiogenic stroke, so common that procedures and devices for closing it off from the left atrium could potentially make warfarin unnecessary in patients with AF. That was the stated hope of members of an FDA advisory committee that voted overwhelming to support approval of the percutaneously delivered Watchman (AtriTech/Boston Scientific) LAA closure device in December 2013, as reported by heartwire .

In the current study, the researchers prospectively looked at 564 candidates for catheter ablation of symptomatic AF not responding to drug therapy who underwent 3D TEE on the eve of the procedure.

LAA thrombi were seen in 36 patients; of those, only two (5.6%) were in LAA with one or two lobes while the remaining 34 had three, four, or five lobes. Of the 296 patients with one- or two-lobed LAAs, only two, or less than 1%, showed thrombus.

Compared with those without thrombus, LAAs containing thrombi had slower emptying velocities; larger orifice areas, depths, and volumes; and more lobes (mean 3.4 vs 2.5; p<0.001 for all differences).

In multivariate analysis, number of LAA lobes and CHADS2 score emerged most strongly as independent predictors of LAA thrombus.

Odds Ratio (95% CI) for LAA Thrombus in Multivariate Analysis

Parameter OR (95% CI) p
LVEF (%) 0.962 (0.934–0.992) 0.01
Left atrial volume (mL) 1.018 (1.003–1.032) 0.02
CHADS2 score 1.752 (1.237–2.483) 0.002
Degree of spontaneous echo contrast 1.783 (1.102–2.740) 0.02
LAA lobes (n) 2.469 (1.495–4.078) <0.001

In an analysis that included only patients with a CHADS2 score of 0 or 1, at lowest risk for stroke based on clinical features, the significant LAA thrombus predictors were number of LAA lobes (p=0.008), spontaneous echo contrast (p=0.003), and LVEF (p=0.022).

3D TEE was repeated after a mean of 19 months in the 46 patients who had maintained sinus rhythm one year after ablation. Those patients showed significant left atrial and LAA reverse remodeling as evidenced by decreases in left atrial volume (p<0.001) and LAA orifice area (p=0.003), depth (p=0.002), and volume (p<0.001); and increased LAA emptying velocity (p=0.02). They had a lower degree of spontaneous echo contrast (p<0.001) and, strikingly, a 65% drop in natriuretic-peptide levels (p<0.001).

Knowing the number of LAA lobes could potentially be useful for guiding decisions on anticoagulation when the best course isn't clear from other risk stratifiers, according to the group. For example, based on the follow-up data, "in patients who have maintained sinus rhythm for a long time after catheter ablation, we wonder whether anticoagulation therapy should be continued."

The authors had no disclosures.

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