Document Detail

Beat-to-beat augmentation of left ventricular function by intraaortic counterpulsation.
MedLine Citation:
PMID:  8659782     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Measuring the effects of intraaortic balloon counterpulsation (IABP) in single cardiac beats may permit an improved understanding of the physiologic mechanisms by which IABP improves the circulation. The objective of the study was to use trans- esophageal echocardiography in combination with hemodynamic measurements to test the hypothesis that IABP improves global left ventricular systolic function selectively in the IABP-augmented cardiac beats by acutely decreasing left ventricular afterload. METHODS: Twenty-seven studies in which the IABP-to-R wave trigger ratio was serially changed from 1:1, 1:2, 1:4, 0:1 (IABP off) and back to 1:1 were performed in 20 anesthetized cardiac surgical patients during IABP support. Left ventricular short-axis end-diastolic cross-sectional area, end-systolic area, mean end-systolic wall thickness, and ejection time were measured by transesophageal echocardiography at the midpapillary muscle level. Aortic pressure was measured simultaneously from the central lumen of the intraaortic balloon catheter. These measurements were used to calculate the fractional area change, end-systolic meridional wall stress, and heart rate-corrected velocity of circumferential fiber shortening. The echocardiographic and hemodynamic parameters of left ventricular preload, afterload, and systolic function immediately after balloon deflation (IABP-augmented cardiac beats) were compared to the parameters measured during nonaugmented cardiac beats to determine the beat-to-beat effects of IABP on left ventricular function. RESULTS: IABP-augmented cardiac beats had a decreased systolic arterial pressure and end-systolic meridional wall stress and increased diastolic blood pressure, fractional area change, and velocity of circumferential fiber shortening compared to nonaugmented cardiac beats. IABP did not cause significant beat-to-beat changes in heart rate, pulmonary artery diastolic pressure, or central venous pressure. The improvement in left ventricular systolic function associated with IABP-augmented cardiac beats correlated with the decrease in end-systolic meridional wall stress for that cardiac beat. CONCLUSIONS: Beat-to-beat echocardiographic and hemodynamic measurements performed in anesthetized cardiac surgical patients during IABP support demonstrated improved left ventricular systolic function and decreased left ventricular systolic wall stress in the cardiac beats immediately after balloon deflation. The relationship between left ventricular systolic function and left ventricular systolic wall stress during IABP support suggests that afterload reduction was an important mechanism by which IABP instantaneously improved circulatory function in anesthetized cardiac surgical patients.
A T Cheung; J S Savino; S J Weiss
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Anesthesiology     Volume:  84     ISSN:  0003-3022     ISO Abbreviation:  Anesthesiology     Publication Date:  1996 Mar 
Date Detail:
Created Date:  1996-07-26     Completed Date:  1996-07-26     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  1300217     Medline TA:  Anesthesiology     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  545-54     Citation Subset:  AIM; IM    
Department of Anesthesiology, Division of Cardiothoracic Anesthesia, University of Pennsylvania, Philadelphia, 19104-4283, USA.
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MeSH Terms
Aged, 80 and over
Coronary Circulation
Echocardiography, Transesophageal
Middle Aged
Ventricular Function, Left*

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