The walls of the left atrium are slightly thicker than the walls of the right atrium. Oxygen-rich blood from the lungs enters the left atrium through the pulmonary vein. The blood is then pumped into the left ventricle chamber of the heart through the mitral valve. From there, the blood is ready to be pumped into the body to deliver oxygen-rich blood to all bodily tissues. Mitral valve prolapse is a common affliction in which the mitral valve between the left atrium and left ventricle does not close properly.
This condition does not typically require treatment; however, some patients with mitral valve prolapse can develop more serious conditions that require treatment.
One such condition is mitral valve regurgitation, in which blood leaks back into the left atrium through the mitral valve. The right atrium is one of the four chambers of the heart. The heart is comprised of two atria and two ventricles.
Blood enters the heart through the…. In coordination with valves, the chambers work to keep blood…. The coronary sinus is a collection of smaller veins that merge together to form the sinus or large vessel , which is located along the heart's…. Conclusions: Significant variations exist for mean LA wall thickness at different regions which are often targeted during circumferential pulmonary venous ablation CPVA.
Appreciating these differences may have significant implications in catheter ablation of AF. Abstract Background: The success and complication rates of atrial fibrillation AF ablation may be related to regional differences in left atrial LA wall thickness. AF treatment consists in preventing thrombo-embolic complications and in treatment of symptoms using anti-arrhythmic therapy or frequency control [ 1 ].
Catheter ablation in the Left Atrium LA has become a therapeutic option to maintain sinus rhythm in patients with AF, although the substrates for the development of AF and therefore the target for ablation remain to be fully described [ 1 ]. The pulmonary veins are central to the initiation of the fibrillatory process, as it defines an area of increased electrical activity [ 1 ].
The centrepiece in ablation is consequently the creation of transmural LA wall lesions that ensure permanent electrical isolation of the pulmonary veins [ 2 ]. Alterations in LA geometry and wall tissue composition may play a critical role in arrhythmia induction and perpetuation [ 3 ]. The LA cavity and the Pulmonary Veins PV are complex anatomical structures with important interpatient variability in size, form and branching patterns [ 4 , 5 ].
The interaction between LA anatomy and ablation catheters including contact force, catheter stability, energy delivery intensity and duration of ablation, has been shown to affect the clinical efficacy of ablation [ 2 ]. MDCT is a well established modality for pre-ablation evaluation of gross anatomy of the LA with focus on PV location and numbers [ 4 ]. However, recent developments in MDCT have made it possible to visualize the LA in greater details, including wall characteristics and the PV size noninvasively with high spatial and reasonable temporal resolution by creating high-quality three-dimensional images [ 6 ].
This widely accessible imaging modality may be used to provide a more detailed anatomical evaluation and road map before ablation, in terms of both LA and PV anatomy [ 3 , 7 - 12 ]. Recent studies indicate that LA and PV characteristics as determined by cardiac MDCT are possible important predictors of AF recurrence after ablation therapy [ 11 , 13 - 16 ], and that the thicker the parts of the LA are, the less successful ablation therapy becomes [ 13 , 17 ]. In addition, it has been found that patients with persistent AF have enlarged LA cavity, decreased left ventricular function and lower success rates than other patients referred for ablation [ 7 , 9 , 18 , 19 ].
This study was cross-sectional. The controls were recruited from the Copenhagen General Population Study CGPS , which is an on-going prospective general population study with registration of health-related conditions [ 20 ]. Participants were randomly selected, and age-, BMI- and gender-matched in sinus rhythm without a history of cardiac disease in a ratio of with AF patients.
The Danish National Committee of Biomedical Research Ethics approved the study protocols and all patients gave written informed consent. MDCT was performed prior to ablation in the AF patients group and used as image integration to guide the ablation.
Automated bolus triggering in the descending aorta with a threshold of Hounsfield Units was used for initiation of image acquisition, and ml intravenous contrast agent Visipaque , GE Healthcare was infused flow rate of 5. The scanner settings were: gantry rotation time 0. A cardio selective beta-blocker metoprolol mg was administered orally 1 h before scanning in controls with a heart rate of more than 60 bpm, unless systolic blood pressure was less than mmHg or other contraindications to beta-blocker treatment did exist.
For the AF patients retrospective gating, dose modulation and iterative reconstruction algorithms were used. Adaptive Iterative Dose Reduction 3D AIDR 3D is the newest iterative reconstruction algorithm developed by Toshiba which - based on the scanning conditions and electronic noise statistics - preserves the maximal attenuation density signal while noise and artifacts are reduced. The estimated radiation dose was 5 mSv.
All image data were transferred to an external workstation Vitrea 6. Assessment of left atrial wall thickness, pulmonary vein size and left atrial volume were performed using the mid-diastolic frame with least cardiac motion as assessed automatically from raw-data. It was measured from axial views in 12 preselected locations Figure 1 based on the differences in Hounsfield Units HU for various compartments contrasted blood HU, left atrial wall tissue 50 HU and pericardial fat - and with anatomical fix points the pulmonary veins and the left atrial appendage as guidance in location determination Figure 2.
We included 3 locations at the roof right, middle, left , 3 locations at the floor right, middle, left , 4 locations at posterior wall right, middle, middle-superior, left , 1 at the Left Lateral Ridge LLR , and 1 at the mitral isthmus as previously described [ 11 ].
The LAWT was assessed as the mean of 3 manually performed measurements in each preselected location, or excluded if not possible due to anatomical anomalies or motional artefacts - 23 measurements 2. Global LAWT was calculated as the mean thickness in each patient based on a summed mean of all preselected locations.
Figure 1: Preselected locations for left atrial wall thickness assessment, modified from Beinart, et al.
View Figure 1. Figure 2: Method demonstration of left atrial wall thickness assessment, in this case location 5. Axial view. View Figure 2. It was defined as the cross-sectional area of each pulmonary vein 5 mm perpendicular to the ostium of the pulmonary vein Figure 3. The PV ostium was defined as the intersection between the LA wall and PV wall, and the extent of the ostium was determined using multiple coronal planes. Figure 3: Method demonstration of pulmonary vein cross-sectional area assessment.
View Figure 3. It was measured from axial view by manually tracing the endocardial wall on tomographic slices as previously described interobserver variation 1. The pulmonary veins were identified and excluded from the PV ostium, whereas the LA appendage was included in the LA cavity. The border of the LA was defined as a straight line between the attachments of the mitral valve.
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