Contribution of decreased atrial function in the pathogenesis of neurally mediated XXXX .

@entity1 @entity907 @entity1163 @entity551 @entity1168
One of the most important mechanisms proposed in the pathogenesis of neurally mediated @entity1163 considers the stimulation of myocardial mechanoreceptors as the final trigger leading to reflex @entity551 and @entity1168 . The aim of our study was to analyze the modifications of systolic and diastolic velocities of the left ventricle by tissue Doppler echocardiography, during the upright tilt test, to confirm the presence of an increased ventricular contractility before @entity1163 . We evaluated 47 @entity1 (mean age 43 years) with unexplained @entity1163 and 13 healthy subjects. Three echocardiographic recordings were collected: at baseline, during the initial 5 minutes of the test, and after 15 minutes of tilt. The upright tilt test was positive in 28 @entity1 . During the test, all of them had a similar, significant, progressive reduction of left ventricular end-diastolic volume, left atrial area, and left atrial volume. In contrast, the left ventricular ejection fraction showed an early, more pronounced decrease in those with positive tests. By tissue Doppler echocardiography, the systolic waves remained almost unchanged, and the early filling waves decreased similarly in those with positive or negative findings and the controls. In contrast, the atrial filling waves showed a significant decrease only in @entity1 with positive tests. In conclusion, our study did not find increased ventricular contractility before @entity1163 . In contrast, a decreased atrial contribution to ventricular filling characterized @entity1 with positive upright tilt test results, which, we postulate, may be an important contributory factor to @entity907 .
