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EXPERIMENTAL STUDY

Influence of left ventricular dysfunction on the role of atrial contraction

An echocardiographic-hemodynamic study in dogs

Brian D. Hoit, BS, FACC^* and Marjorie Gabel, BS

^* Department of Medicine, Case Western Reserve University, University Hospitals of Cleveland, 11100 Euclid Avenue, Cleveland, Ohio, USA
Department of Medicine, University of Cincinnati, Box 670542, Cincinnati, Ohio 45267, USA

Manuscript received January 14, 2000; revised manuscript received April 27, 2000, accepted June 21, 2000.

Reprint requests and correspondence: Dr. Brian D. Hoit, Division of Cardiology, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, Ohio 44106.
bdh6{at}po.cwru.edu

OBJECTIVES

The purpose of this study was to understand the significance of an effective atrial systole and the interactions between atrial and ventricular function.

BACKGROUND

The significance of atrial function is controversial, particularly in the setting of left ventricular (LV) dysfunction.

METHODS

Serial, rapid pacing in five dogs that had undergone radiofrequency ablation and implantation of right atrial and ventricular pacemakers produced reversible atrial and ventricular dysfunction (alone and in combination). Atrial function (echocardiograph-determined transmitral diastolic flow, left atrial appendage emptying, and pulmonary venous flow), cardiac output, and right heart pressures were measured at matched paced heart rates of 80 beats/min.

RESULTS

Isolated rapid atrial pacing (LV ejection fraction 60%) decreased atrial booster pump in the body and appendage of the left atrium, but increased the conduit function of the left atrium. Isolated LV dysfunction (LV ejection fraction 34%) increased atrial booster pump function. The decreased atrial booster pump function in animals with combined atrial and ventricular dysfunction was incompletely compensated by the redistribution of the reservoir and conduit functions of the left atrium. As a result, cardiac output decreased and right heart pressures increased only after superimposed pacing.

CONCLUSIONS

In the presence of a normal left ventricle (LV), atrial failure has little effect on cardiac output and right heart pressures because of compensatory conduit function, but when early LV dysfunction coexists, changes in reservoir and conduit functions are insufficient to compensate for an impairment of atrial contraction.

Abbreviations and Acronyms   AV = atrioventricular   Jvti/[Jvti+Kvti] = left atrial (LA) reservoir function   Kvti/[Jvti+Kvti] = left atrial conduit function   LA = left atrium/left atrial   LAA = left atrial appendage   LVEDD = left ventricular (LV) end-diastolic dimension   MV = mitral valve   PA = pulmonary artery   PV = pulmonary vein   RA = right atrial   RF = radiofrequency   VTI = velocity-time integral

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