Doppler Derived Indices of the Left Ventricular Diastolic and Systolic Function in Neonate and Young Kitten
In human beings, neonates and children are acknowledged to have a highly performant but less compliant left ventricle whose diastolic filling is more dependent upon the left atrial systole and subsequently poorly tolerates left atrial pump failure (The Journal of The American College of Cardiology. 1998. 32.1441-1448)
This study was done to determine and compare the Doppler derived indices of the left ventricular (LV ) diastolic and systolic function in neonate ( under 1 month ) and young kitten ( 1 to 3 months ) and to test the hypothesis of a predominant left atrial contribution to the left ventricular filling in the neonate kitten.
The neonate group (13 kittens) and the kitten group (14 kittens) underwent echocardiograhic examination without sedation. Diastolic parameters included the isovolumetric relaxation time, peak early filling velocity, early filling acceleration and deceleration times, peak late filling velocity, active filling time, passive and active filling velocity time integrals. Systolic parameters included the peak velocity, acceleration time and velocity time integral of the aortic ejection flow. Median values for parameters of each group were compared using the Mann-Wittney test. Univariate linear correlation analysis was used to determine significant correlation between variables in each group.
The preload approximated from the sum of the early and late filling velocity time integral was significantly greater in the kitten. Within each group there was a good positive correlation between the peak early filling velocity and the preload. The peak early filling velocity and the contribution of the passive filling to the LV filling were significantly lower in neonates. The left atrial pump function approximated from the active atrial inflow and the peak late filling velocity were similar in the 2 groups. The stroke volume approximated from the aortic velocity time integral was significantly lower in the neonates in the face of a similar aortic acceleration time in the 2 groups.
The predominant contribution of the left atrial systole to the LV filling correlates with a steady left atrial pump function in the early life in the face of a low passive filling. The positive influence of preload on the passive filling and peak early atrioventricular pressure difference suggests that the increasing preload with age is the essential determinant for the changes in the LV filling dynamics in kitten. The discrepancy between the increasing stroke volume coupled with the constant acceleration time of the aortic flow suggests a steady myocardial contractility in the face of an increasing left ventricular pump function related to the increasing LV loading conditions.