Mechanical correlates of contraction-excitation feedback during acute ventricular dilatation.
OBJECTIVE
The purpose was to examine the mechanical correlates of the electrophysiological changes that occur during acute left ventricular dilatation.


METHODS
Ten isolated, retrogradely perfused, ejecting rabbit hearts were studied. Left ventricular volume was adjusted by varying left atrial perfusion pressure. Left ventricular pressure was measured directly. Changes in left ventricular chamber dimensions at the level of an epicardial electrode were evaluated with two dimensional echocardiography and wall stress was calculated from these measures. Regional left ventricular electrophysiological properties were measured at two left atrial perfusing pressures.


RESULTS
Increases in left atrial perfusion pressure resulted in significant increases in left ventricular end diastolic and end systolic pressures, epicardial and endocardial circumference, and wall stress. Only changes in diastolic wall stress correlated with changes in ventricular refractoriness (r = 0.69, p = 0.027).


CONCLUSIONS
Left ventricular dilatation results in shortening of ventricular refractoriness in the isolated, ejecting rabbit heart. Regional changes in refractoriness are best correlated with changes in wall stress.
Halperin
B D
BD
Division of Cardiology, University of Colorado Health Science Center, Denver 80262.
Adler
S W
SW
Mann
D E
DE
Reiter
M J
MJ
D000208:Acute Disease; D000818:Animals; D001696:Biomechanical Phenomena; D004108:Dilatation, Pathologic / Q000503:physiopathology; D004594:Electrophysiology; D005246:Feedback / Q000502:physiology; D006331:Heart Diseases / Q000503:physiopathology*; D006333:Heart Failure / Q000503:physiopathology; D006439:Hemodynamics / Q000502:physiology; D009200:Myocardial Contraction / Q000502:physiology*; D011817:Rabbits; D016277:Ventricular Function, Left / Q000502:physiology*