APStracts 2:0116A, 1995.

Effect of negative intrathoracic pressure on left ventricular pressure dynamics and relaxation. Virolainen, Juha, Markku Ventil[umlaut]a, Heikki Turto, and Markku Kupari. Division of Cardiology, Department of Medicine, Helsinki University Central Hospital, FIN-00290 Helsinki, Finland.

APStracts 2:0116A, 1995.

To investigate the effect of a fall of intrathoracic pressure on left ventricular (LV) hemodynamics and relaxation, simultaneous micromanometric recordings of LV and aortic pressure were performed at rest and during two graded Mueller maneuvers in 16 patients undergoing cardiac catheterization for aortic valve stenosis (n=8) or chest pain (n=8). The reductions of airway pressure (mean +/- SE) during the lesser and greater maneuver were 26 +/- 1 and 42 +/- 1 mmHg, respectively. Simultaneously, LV isovolumic developed pressure increased by 9 +/- 3 and 21 +/- 4 mmHg (P<0.03 for both). During the greater maneuver, the individual changes of the time constant of LV isovolumic relaxation ( ) correlated with the changes of LV isovolumic developed pressure (r=0.73, P=0.002). In patients with >20 mmHg rise in isovolumic developed pressure, increased by 10.3 +/- 4.6 ms. In multiple regression analysis, the change of was related directly to the change of isovolumic developed pressure (standardized coefficient =0.80, P=0.001) and inversely to the resting systolic LV_aortic pressure gradient ( =_0.37, P=0.050). The other hemodynamic changes were independent of aortic valve stenosis. In conclusion, during the Mueller maneuver the LV isovolumic contraction load increases and lengthens particularly with higher elevations of LV systolic load.

Received 29 August 1994; accepted in final form 10 March 1995.
APS Manuscript Number A910-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 28 March 1995.