Left Atrial Hemodynamics in AF Patients Selected for Catheter Ablation

Presenting Author(s)

• RS

  Roberto Sarnari, MD

  Clinical Research Associate
  Northwestern University Feinberg School of Medicine

Primary Author(s)

• RS

  Roberto Sarnari, MD

  Clinical Research Associate
  Northwestern University Feinberg School of Medicine

Co-Author(s)

• JB

  Justin Baraboo, MSc

  PhD candidate
  Northwestern University
• DD

  David Dushfunian, MD

  Clinical Research Associate
  Northwestern University Feinberg School of Medicine
• RP

  Rod Passman, MD

  Professor of Electrophysiology
  Northwestern University
• PG

  Philip Greenland, MD

  Professor
  Northwestern University
• 

  Daniel Lee, MD, MSc

  Professor of Medicine and Radiology
  Northwestern University Feinberg School of Medicine
  Northwestern
• 

  James C. Carr, MD

  Professor
  Northwestern University Feinberg School of Medicine
• 

  Michael Markl, PhD

  Professor
  Northwestern University Feinberg School of Medicine

Background: Atrial fibrillation (AF) is the most commonly diagnosed cardiac arrhythmia. AF leads to flow alterations in the left atrium (LA) and left atrial appendage (LAA) which promote thrombus formation and risk for cardioembolic stroke. Current therapeutic decisions are based on clinical evaluation and stroke risk assessment using predictive models such as the CHA₂DS₂-VASc score (c-statistic 0.6-0.7). However, CHA₂DS₂-VASc does not include atrial hemodynamic parameters known for promoting atrial thrombus formation (such as LA and LAA flow stasis and  reduced flow velocity). The purpose of this study was to investigate the distribution of LA-LAA hemodynamics in a large cohort of AF patients selected for catheter ablation (CA) procedure.

Methods: One hundred ninety-four AF patients (age=63±10 years, 142 male, 44 % hypertensive, 73% paroxysmal AF, 49% low to moderate stroke risk as per CHA₂DS₂-VASc score = 0-1) selected for CA underwent CMR for pulmonary vein mapping, including ECG and respiratory gated 4D flow MRI. 4D flow data analysis included pre-processing and manual 3D segmentation of the LA and LAA followed by quantification of blood stasis (% of cardiac time frames with region velocities < 10 cm/s) and peak velocities (Fig 1). Whole group analysis was performed. Two groups were then generated for comparison: high risk AF (CHA₂DS₂-VASc score ≥2) and non-high risk AF (CHA₂DS₂-VASc score < 2). Demographics and group characteristics in Table 1.

Results: Higher LA stasis, lower peak velocity, higher volume and higher LAA stasis were correlated with higher patient age (r = 0.30, -0.38, 0.19 and -0.24, respectively, p < 0.01). Compared to women, men had higher LA and LAA volumes (81 ± 28 ml vs. 108 ± 41ml, p < 0.01, and 6 ± 2 ml vs. 7 ± 4, p < 0.01), and lower LAA stasis (67 ± 13% vs. 59 ± 14%, p < 0.01). Compared to paroxysmal AF, patients with persistent AF had higher LA stasis (44 ± 14% vs. 52 ± 17%, p < 0.01), lower LAA peak velocity (0.37 ± 0.10 m/s vs. 0.33 ± 0.11 m/s, p < 0.05), and higher atrial volumes (LA: 96 ± 38 ml vs. 115 ± 42ml, p < 0.01; LAA: 6 ± 3 ml vs. 8 ± 4, p < 0.01). (Fig 2). Higher CHA₂DS₂-VASc score was associated with lower LA peak velocity, higher LA and LAA stasis (Kendall’s tau = -0.23, 0.12, 0.14, all p < 0.02). At group comparison, LA stasis (50 ± 15% vs 43 ± 15%, 0 < 0.01), LAA stasis (64 ± 15% vs 58 ± 13%, p< 0.01) were higher and LA peak velocity (0.34 ± 0.07m/s vs 0.39 ± 0.11m/s, p< 0.01) was lower in the high risk group, despite no significant difference in LA volume.

Conclusion: In this cross-sectional study, women demonstrated greater flow stasis in the LAA, despite smaller LA and LAA. Higher CHA₂DS₂-VASc score showed weak correlations with flow parameters associated with risk of thrombus formation and atrial hemodynamics analysis may help refining stroke risk estimation and clinical decision-making. After AF-CA, atrial hemodynamics analysis could also improve outcome definition and risk reassessment.

Figure 1. Left atrial 4D flow measurements and analysis workflow for LA and LAA flow parameters quantification. Top: 4D flow post processing for LA and LAA parameters. Bottom: stasis and peak velocity 4D-MIP color maps displayed for left atrium (LA) and left atrial appendage (LAA).

Figure 2. Top: Correlations between age and left atrial stasis are reported on the left; correlation between left atrial peak velocity and CHA₂DS₂-VASc score are reported on the right. Bottom left: box plots for left atrial stasis in patients with paroxysmal vs persistent atrial fibrillation. Bottom right: box plots for left atrial appendage flow stasis in males and females. LA: left atrium. LAA: left atrial appendage.