Albors, Carlos

Abstract Background Left atrial appendage (LAA) closure or amputation is commonly performed in atrial fibrillation (AF) patients undergoing cardiac surgery to reduce stroke risk. It has been shown that LAA closure or amputation results in persistent blood pressure (BP) decrease, which may be due to a surge in atrial natriuretic peptide (ANP) and by suppression of sympathetic activity due to activation of mechanoreceptors by atrial distention. We hypothesize that size of the LAA, a compliant structure, affects atrial distension. Consequently, patients with smaller LAA remnants (i.e. more complete amputation) have more distension of the atrium and a more pronounced BP response upon LAA amputation. Methods We analyzed 33 patients with persistent AF from the MARK AF registry who underwent LAA amputation concomitant to thoracoscopic AF ablation. Systolic BP was measured at baseline, 12 hours (h), 24h, and 48h, 1 month, 1 year, and 2 years postoperatively. Complete amputation was defined as LAA remnant depth <10mm and a remnant LAA was defined as depth ≥ 10 mm on contrast enhanced CT 6 months post surgery. The postoperative LAA remnant/LA volume ratio was calculated by segmenting the atria and quantifying the volume of the contrast pools. T-tests and linear regression analyzed BP changes by remnant size and LAA remnant/LA volume ratio. Results were visualized using a boxplot and scatter plots with regression lines. Results 25/33 Patients had a LAA remnant. Baseline systolic BP was similar with 147 ± 31 mmHg in the complete amputation group vs. 137 ± 23 mmHg in the remnant group, p=0.389. Complete amputation correlated with greater systolic BP reductions in relation to baseline at 12h (-18%, p=0.018), 24h (-14%, p=0.025), 48h (-15%, p=0.028), 1 month (-20%, p=0.024), and 1 year (-16%, p=0.001), Figure 1. BP returned to baseline by 2 years in both groups. Lower LAA remnant/LA volume ratios were significantly associated with greater systolic BP reductions at 12h (β=7.4, p=0.005), 24h (β=9.9, p<0.001), 48h (β=10.1, p=0.002), and 1 month (β=11.1, p=0.01), Figure 2. However, this association was not observed at 1 and 2 years. Conclusion Patients with smaller LAA remnants after LAA amputation experienced a more pronounced transient reduction in blood pressure. Our findings suggest that increased atrial distension—due to the loss of compliant LAA tissue—could play a key role in modulating hemodynamics via sympathoinhibition and suppression of the Renin-Angiotensin-Aldosterone System (RAAS). Further investigation is needed to confirm these results and explore the neurohumoral effects of LAA amputation.Figure 1 Figure 2

Abstract Background Patients with atrial fibrillation (AF) are at increased risk of stroke, often arising from a thrombus in the left atrial appendage (LAA). In selected cases, left atrial appendage occlusion or closure is an alternative for stroke prevention with oral anticoagulation. To assess the risk of stroke and the benefit of LAA closure and to select the appropriate device, it is crucial to quantify the morphology and dynamics of the left atrial appendage (LAA). To date, much about LAA dynamics in this setting is unknown, and subsequently the risk of embolic stroke and inappropriate device positioning is insufficiently explored. Purpose We describe the morphological and dynamic differences of the left atrium (LA) and LAA in high risk AF patients compared to controls undergoing trans catheter aortic valve implantation (TAVI). Methods Our study population consists of 14 patients, seven with AF and seven without AF, undergoing TAVI, since dynamic computed tomography (CT) angiography scans are performed in the standard of care in these patients. The scans were acquired every 5% of the cardiac cycle (i.e., R-R interval on the ECG) (Figure 1a). The LA and LAA were semi-automatically segmented (Figure 1b) to determine the following parameters across the entire cardiac cycle: LA volume; LAA volume, depth, height, and length; and ostium area, eccentricity, and diameter. Results AF patients had a significantly larger LA volume (108 mL vs 68 mL, p=0.03), while the LA volume change throughout the cardiac cycle was similar in AF patients and controls. Both groups had an LA volume change of 35mL on average. Figure 1cd shows the LA and LAA volume curves of a patient with and without AF. The LAA ostium size and volume of AF patients exhibited larger dynamic variations than those from non-AF patients, while the ostium eccentricity in AF patients showed less variation and the ostium shape was rounder. Conclusions We found differences in morphologic and dynamic parameters of the LA and LAA between AF and non-AF patients. The morphology and dynamics of the LAA can increase the understanding of LAA thrombus formation. Moreover, it may have implications for the risk of embolic stroke and may assist in the selection of the optimal LAA closure device type and size.