[The influence of increased preload on left ventricular systolic function in infants with congenital heart disease].

UNLABELLED: The aim of the study was to assess the systolic function of the volume overloaded left ventricle (LV) in infants with congenital heart disease.

MATERIAL: Seventy five consecutive patients (36 males, 39 females) with following breakdown were examined: 14 (18.7%) newborns, 24 (32%) infants under 3 months, 16 (21.3%) between 4 and 6, and 21 (28%) infants above 6 months of age. VSD was recognized in 60 (80%), PDA--6(8%), DORV--7 (9.3%), and CT (type I) in 2 (2.7%) of the patients.

METHODS

Based on ECHO studies LV end diastolic volume (LVedv), end diastolic muscle mass (LVedm), LV shortening fraction (FS), ejection fraction (EF), LV fractional area changes (FAC), and heart rate (HR) versus pulmonary blood flow (Qp), which reflected the LV preload systemic blood flow (Qs), Qp/Qs, Qp-Qs (left-to-right shunt) and indexed for body surface area (BSA) and age, were assessed by statistical analysis.

RESULTS

With a gradual increase of BSA with age (cc = 0.82, p < 0.001), a significant decrease in Qp-Qs (cc = -0.27, p = 0.035) and Qp/Qs (cc = -0.31, p = 0.013) were noted. Qp for the whole group ranged from 3.3 to 21.7 l/min/m2 (m = 8.9, x = 9.7, SD = 4.1), significantly increased with the rise of Qp-Qs (cc = 0.9, p < 0.0001) and influenced the increment of Qp/Qs (cc = 0.59, p < 0.001). Qs for the whole group ranged from 2.1 to 11.7 l/min/m2 (m = 4.3, x = 4.6, SD = 1.7) correlating with the rise of Qs (cc = 0.45, p < 0.001), and being lower than 2.5 l/min/m2 in only 5 (6.7%) patients but in only 5 (6.7%) patients (all newborns). The heart rate gradually decreased with age (r = -0.26, p = 0.04), from mean 145/min in newborns to 123/min in infants over 6 months, and with BSA (cc = -0.34, p = 0.006). Heart rate also correlated well with Qp (cc = 0.31, p = 0.014). The increase of LVedv was related to age (cc = 0.37, p = 0.003), BSA (cc = 0.43, p = 0.0004) and Qp (cc = 0.33, p = 0.009). However, only in newborns was the mean LVedv within normal limits for age. LVedm only correlated with BSA (cc = 0.26, p = 0.04), except in newborns where its mean values exceeded the upper limits for age in other subgroups of patients. LV systolic function indicators (FS, EF, FAC) were diminished in only 2 cases and did not correlate either with age, BSA, nor with hemodynamic parameters.

CONCLUSIONS

1. The reactions to increased preload of the systemic ventricle in children below one year of age were different. In newborns, the adrenergic response predominated, while infants manifested increased end-diastolic volume and left ventricular muscle mass. 2. The systolic function of the overloaded left ventricle in infants was normal regardless of age, body surface area and intensity of hemodynamic disturbances.