Several clinical studies (e.g.Danish Ⅱ1,2, Danish Ⅱ3,4, DAVID5, MOST sub analysis) have shown that unnecessary chronic right ventricular pacing has detrimental effects such as atrial fibrillation, left ventricular dysfunction and congestive heart failure, even in patients with intact AV conduction.Right ventricular apical (RVA) pacing produces an anomalous activation of the ventricles resulting in mechanical asynchrony, especially when conduction disturbances are present7.It is known that this anomalous activation pattern results in a redistribution of the myocardial work load and perfusion and, after years, a remodelling of the left ventricle with a redistribution of the myocardial wall mass.