RESUMO
ObjectiveTo observe right ventricle (RV) structure and function of New Zealand rabbits with chronic intermittent hypoxia (CIH) for short-term (0-8 weeks) by echocardiography. MethodsTwenty-four healthy male New Zealand rabbits were set up CIH animal model for 8 weeks. RV structure?s systolic and diastolic function were measured by conventional and tissue Doppler echocardiography at 0, 1, 2, 4, 6 and 8 week and one rabbit was sacriifced randomly for RV myocytes and pulmonary tissue pathology examination. RV structure and function parameters at 0, 1, 2, 4, 6 and 8 week were analyzed by mixed effects model analysis.ResultsRV structure variables: RV, RA at 8 week increased compared with those at 0 week, but had no signiifcant difference (P>0.05); RV systolic function variables:RVFAC at 8 week increased compared with those at 0 week (F=3.45, P<0.05), TAPSE at 4, 6, 8 week increased compared with that at 0 week (F=3.11, 3.41 and 3.86, all P<0.05), RVMPI at 4 week decreased compared with that at 0 week (F=3.46, P<0.05), recovered to baseline at 6, 8 week. Isovolumetric relaxation time (IRTc) corrected by heart rate at 1, 2, 4 week decreased compared with that at 0 week (F=3.15, 3.31 and 3.17, all P<0.05), recovered to baseline at 8 week, ET of PA at 1, 2 week decreased compared with that at 0 week (F=3.01 and 3.15, both P<0.05), recovered to baseline at 4, 6, 8 week, AT of PA at 1, 2, 4 week decreased compared with that at 0 week (F=3.13, 3.15 and 3.32, all P<0.05), recovered to baseline at 6, 8 week. RV diastolic function variables: isovolumetric contraction time (ICTc) corrected by heart rate at 2, 4 week decreased compared with that at 0 week (F=3.13 and 3.33,both P<0.05), E/E? at 1, 2 week decreased compared with that at 0 week (F=3.13 and 3.44,bothP<0.05), recovered to baseline at 4, 6, 8 week, E/A at 4, 6, 8 week increased compared with that at 0 week (F=4.01, 3.82 and 3.37, all P<0.05), E?/A? at 8 week increased compared with that at 0 week (F=3.81, P<0.05). The myocardial pathology showed that RV myocardial cell structure was normal at 4 week. Nuclei enlarged, stain darkened and some cytoplasms loosed when exposed to CIH for 8 weeks. The structure of lung tissues was normal when exposed to CIH for 4 weeks. Inflammatory cell inifltrated, capillary engorged as well as the wall of pulmonary arterioles thickened slightly at 8 week.ConclusionsRV diastolic and systolic function showed compensatory and structure was normal in early CIH (0-8 week). RV diastolic function compensated earlier than systolic function. IRT and ICT were sensitive indicators of RV systolic and diastolic function compensation.