Abstract 18081: Inverse Changes in Atrial Size During Obstructive Apnea

Abstract

Introduction: Obstructive sleep apnea (OSA) is characterized by large swings in intrathoracic pressure. These pressure changes create an afterload burden on the left ventricle and presumably affect venous return to the right heart, and pooling of blood in the lungs. To better understand cardiac dynamics during OSA we used real time 2-D echocardiography to compare left (LA) and right atrial (RA) areas at baseline and during a series of gasping inspiratory efforts against an occluded airway. Hypothesis: Significant changes in atrial area will occur during inspiratory effort, with an inverse relationship between the two atria. Methods: Each of 14 healthy male subjects <30 years, trained in the Mueller Maneuver (MM), made 5 to 6 maximal gasping efforts to simulate naturally occurring OSA. Concomitant echocardiographic loops were acquired using the apical 4 chamber view. Results: Average baseline (end-systolic) atrial area was 16.6 ± 0.837 cm2 (100 beats; mean ± pooled SD) for the LA and 16.3 ± 0.931 cm2 for the RA. During the MM average LA area was 16.7 ± 1.29 cm2 (252 beats) and average RA area was 15.4 ± 1.69 cm2. For left and right separately, variance in atrial area during the MM exceeded that at baseline (p<0.0001, F-test). During the MM, LA variance increased to 2.38-fold that of baseline, RA variance to 3.30-fold. Further, there was an inverse relationship between LA and RA area during the MM (graph). Visual inspection of digitized loops revealed a sudden decrease in LA area with inspiratory effort. Conclusions: Performance of the MM as a series of gasping efforts (designed to mimic natural OSA) produced marked and mutually inverse variation in LA and RA area as compared with baseline. LA area decreased abruptly with onset of negative inspiratory pressure. Such changes, repeated hundreds of times per night, have the potential to alter atrial structure and function. These data may help explain the strong association between obstructive sleep apnea and atrial fibrillation.