RESULTS
Table 1 compares age and medical diagnoses between the two groups. The +HF group had a significantly higher prevalence of trisomy 21, muscular dystrophy, and oromotor incoordination. The +HF group also had, as expected, a higher prevalence of structural heart disease than the -HF group. The types of structural heart disease in the +HF group included atrial septal defect (ASD), ventricular septal defect (VSD), coarctation of the aorta (CoA), pulmonary stenosis (PS), cardiac fibroma, double outlet right ventricle (DORV), and hypertrophic cardiomyopathy. Children with -HF included ASD, VSD, PS, CoA, DORV, vascular ring, bicuspid aortic valve, and truncus arteriosus.
Table 2 depicts the relationship between PSG and echocardiogram findings between the two groups. The +HF group had lower median AHI and lower median CAI when compared to the -HF group. Furthermore, the +HF group had a higher median 2D LV End-diastolic Septal Thickness vs BSA z-score and a higher median 2D LV End-systolic Dimension vs BSA z-score.
At this point we adjusted for age to see if the observed elevations in central apnea measures were a function of age, rather than heart failure condition. An ANCOVA model was used with dependent variable of AHI, fixed factor of +HF group, and covariate of age with Bonferroni correction due to the small sample size. After this adjustment, AHI and CAI were no longer significantly different between the two groups.
Table 3 depicts the prevalence of various definitions of sleep apnea in both groups. Prevalence of both Elevated CAI and AASM CSA was significantly higher in the -HF group. Interestingly, when we used a pediatric CSA definition of CAI+HI >1/hr., the prevalence of pediatric CSA was similar in both groups.
CAI and OAI did not correlate with LVEF or any other echocardiogram z-score parameters.
Due to the wide range of CAI in the study population, we performed logarithmic transformation and depicted the relationship between LogCAI and age in Figure 2. CAI was inversely correlated to age at the time of sleep study (Pearson correlation coefficient -0.245, p = 0.022). OAI did not correlate with age (data not shown).
Using our definition of elevated central apnea index (CAI >1/hr.), we divided our entire cohort into two groups: normal CAI and elevated CAI. Table 4 compares these two groups’ demographics, medical diagnoses, echocardiographic findings, and PSG findings. Children with elevated CAI were younger and had higher prevalence of prematurity. Fewer patients with structural heart disease or evidence of HF had elevated CAI. There was no statistically significant difference in LVEF or other echocardiographic parameters between the two groups.