title: Leftward bulging of atrial septum is provoked by nitroglycerin and by sustained valsalva strain.
abstract: BACKGROUND
  The motion of the interatrial septum primum (septum) is dependent on the interatrial pressure relation, normally with slightly higher pressure in the left atrium and the septum bulging toward the right atrium. The aim of this study was to explore the physiologic mechanisms that reverse interatrial pressures and provoke leftward bulging of septum (LBA). The hypothesis was that both left ventricular unloading with nitroglycerin and sustained Valsalva strain would independently provoke LBA and that their combination would further intensify the effect.
  
  
  METHODS
  Prospectively collected transesophageal echocardiography recordings from 13 patients with obstructive sleep apnea were retrospectively analyzed for the presence or absence of LBA during resting respiration and during Valsalva strain. In each condition, LBA beats were counted at time points before and after nitroglycerin spray had been administered, which enabled a comparison of the independent effects and the combined effect of the nitroglycerin and the Valsalva maneuver. An LBA beat was defined as a heartbeat displaying any LBA during the cardiac cycle.
  
  
  RESULTS
  Nitroglycerin increased the proportion of LBA beats significantly during resting respiration, from 21 ± 27% to 54 ± 43% (P = .008). During Valsalva strain, the proportion increased with nitroglycerin spray from 48 ± 21% to 80 ± 17% (P = .001). After nitroglycerin administration, LBA occurred in at least three beats during strain in all Valsalva periods.
  
  
  CONCLUSIONS
  Unloading of the left ventricle by nitroglycerin administration and by sustained Valsalva strain independently provoked LBA. The combination of these two interventions further intensified the effect.
authors.affiliation: Department of Molecular and Clinical Medicine/Clinical Physiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. Electronic address: magnus.c.johansson@vgregion.se.
authors.forename: Magnus C
authors.initials: MC
authors.lastname: Johansson
authors.affiliation: Department of Molecular and Clinical Medicine/Clinical Physiology, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Cecilia Wallentin
authors.initials: CW
authors.lastname: Guron
mesh_terms: D000368:Aged; D062185:Atrial Pressure / Q000187:drug effects*; D054087:Atrial Septum / Q000000981:diagnostic imaging* / Q000187:drug effects / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D005996:Nitroglycerin / Q000008:administration & dosage*; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D012189:Retrospective Studies; D014463:Ultrasonography; D014636:Valsalva Maneuver; D014665:Vasodilator Agents / Q000008:administration & dosage
chemical_list: D014665:Vasodilator Agents; D005996:Nitroglycerin
keywords: Diastolic function; Echocardiography; Nitroglycerin; Patent foramen ovale; Septum primum motion