Dr. Pio Caso,
Is there an added value of imaging in guiding decision making in patients with atrial fibrillation? In this session, different experts presented the potential use of imaging for the evaluation of morphology and function of the left atrium and of the other cardiac chambers Atrial fibrillation is the most common sustained cardiac arrhythmia, affecting millions of the people around the world, mainly elderly people. Its prevalence is expected to increase with the increasing age of the population. The overall annual stroke risk is 5% in patients with AF, but the risk of stroke increases with age from 1.5 % between 50-59 years to 23.5% in patients aged between 80-89 years. How to evaluate atrial function? The atrium has three functions, namely a reservoir function, a conduit function and a pump function. The first function is active mainly during during ventricular systole and the other two during ventricular diastole. It is possible to evaluate atrial function by assessing atrial dimension and volumes in grey scale by m-mode or two dimensional echo or by new technologies such as strain and strain rate by Doppler myocardial imaging or by speckle tracking, which allows the evaluation of the deformation properties of the atrial wall. Dr Thomas from the Cleveland Clinic emphasized the role of left atrial volume. It is a sensitive surrogate marker of severity and duration of left ventricular diastolic dysfunction Left atrial volumes and left atrial volume index are independent predictors of atrial fibrillation and of recurrence of atrial fibrillation after cardioversion or ablation. Left atrial volume is a predictor of exercise capacity in subjects with normal or impaired LV systolic function and predicts the outcome of mitral regurgitation. The strain shows the deformation properties of the atrial wall, which are impaired in patients with diabetes and ischemic cardiomyopathy. Strain is also inversely correlated with capacity to exercise in healthy patients and in patients with heart failure. Dr Song from Corea presented the anatomy of the pulmonary vein with 3D echo and MSCT, and the impact of atrial fibrillation on other cardiac valves, such as the mitral and tricuspid valves. The Maze procedure can reduce the progressive involvement of these valves during atrial fibrillation. Real time 3D is a new modality imaging that makes it possible to acquire new information on morphology. Dr Faletra from Lugano underlined that this technology can improve the performance of electrophysiological and hemodynamic procedures. TEE 3D has shown utility, showing different atrial structures, such as the crista terminalis, pulmonary veins, left atrial appendage (LAA) and left lateral ridge between the left upper pulmonary vein and left atrial appendage. The visualization of the pulmonary vein is different by 3D TEE: left upper 96%, right upper 92%, lower left 56%, lower right 32%. The visualization of the catheter is important because it guides the electrophysiologist in their work thereby reducing fluoroscopy time for the patient.
The use of 3D TEE imaging techniques has several advantages : a) radiation exposure is reduced; b) difficult anatomical substrates for ablation are identified (prominent pectinate muscles or prominent left atrial ridge and Eustachian valve); c) contact between the atrial wall and the tip of the catheter and the act of burning can be visualized. In a large population with chronic AF patients, despite proven efficacy in the prevention of embolism, long-standing treatment with vitamin K antagonists may present some disadvantages (bleeding, non-compliance, drug- and food-interactions). It is well known that a large majority of embolic events in AF arise from thrombi in the left atrial appendage; this evidence has led to the concept of mechanically excluding the left atrial appendage from the systemic circulation in patients who have one or more contraindications to warfarin. Dr Almeida from Lisbon presented the characteristics of left appendage morphology. The indication for application of devices is patients with atrial fibrillation and high stroke risk (CHADS score > 1) and a contra-indication to coumadin therapy. A multicenter non inferiority study randomized 707 patients with non valvular atrial fibrillation (2:1) to treatment with either the Watchman device or standard treatment with warfarin. It is the largest experience to date in this indication. The device was successfully implanted in 88% assigned to the interventional group. The primary end point (a composite of stroke, cardiovascular death and systemic embolism) was significantly lower in the group with implanted device (3% versus 4.9% per year and per 100 patients) and met the non inferiority criteria. The rate of ischaemic and haemorrhagic strokes was lower in the interventional group (2.3% versus 3.2% per year per 100 patients); all cause mortality was also lower in the interventional group (3.0% vs 4.8%). The primary safety end point (pericardial effusion, procedural air embolism or stroke) was higher in the interventional group (7.4% vs 4.4%). The indication for this procedure remains debated. There is no agreement about the indications, and evaluation of the risk-benefit ratio should be undertaken on a case-by-case basis.
Imaging in atrial fibrillation: added value?
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