Introduction:
The extent of left atrial (LA) wall fibrosis detected by delayed enhancement (DE)-cardiac MRI prior to catheter ablation of atrial fibrillation (AF) appears to predict procedural success. However, it is currently unknown how the degree of fibrosis affects atrial mechanical function.
Methods:
Prior to catheter ablation of AF, 31 patients underwent DE-CMRI and 2-dimensional transthoracic echocardiography. 3D segmentation of LA was performed and the degree of fibrosis was determined using a semi-automated quantification algorithm. Longitudinal mid-septal and mid-lateral LA wall velocity, strain and strain rate were measured during ventricular systole from the apical 4-chamber view by velocity vector imaging.
Results
: There was greater percent of fibrosis as LA maximum (R = 0.4, p = 0.05) and minimum (R=0.52, p = 0.008) volumes increased. Figure
shows examples of DE-CMRI and strain curves (C) for two patients: Patient 1(A) with mild fibrosis and patient 2 (B) with extensive fibrosis. Patient 1 shows much larger strain than patient 2. Larger LA volumes correlated inversely with maximal LA mid-lateral systolic wall strain (p < 0.005). The percent fibrosis also correlated inversely with maximal LA mid-lateral systolic wall strain (R=0.56, p < 0.005) and the systolic strain rate (R = 0.58, p = 0.002).
Conclusion:
LA strain and strain rate can be assessed using standard echocardiographic gray scale images. LA strain is related to both atrial volumes and fibrosis, which are markers of atrial disease progression. This relationship may represent changes in the properties of LA substrate. These novel imaging approaches may be helpful in predicting outcomes in patients with AF.
Association of Atrial Tissue Fibrosis Identified by Delayed Enhancement MRI and Atrial Fibrillation Catheter Ablation
