[Adrenomedullin alleviates collagen accumulation in pulmonary arteries of rats with hypoxic pulmonary hypertension].

OBJECTIVE: To observe the effect of adrenomedullin (ADM) on the pulmonary vascular collagen metabolism in hypoxic rats in order to study the effect of ADM on chronic hypoxic pulmonary vascular structural remodeling and its possible mechanism. METHODS: Nineteen male Wistar rats were randomly divided into three groups: normal control (n=6), hypoxia (n=7) and ADM-treated hypoxia (n=6). ADM was subcutaneously administered into rats of the ADM-treated hypoxia group by mini-osmotic pump (300 ng/h) for two weeks. After two weeks of hypoxic challenge, mean pulmonary arterial pressure (mPAP) was evaluated using a right cardiac catheterization procedure. The ratio of right ventricular mass to left ventricular plus septal mass[RV/ (LV+S)] was measured. The changes of pulmonary vascular microstructure were observed. Meanwhile, the expression levels of collagen I, collagen III and transforming growth factor (TGF)-ß in pulmonary arteries were detected by immunohistochemical assay. RESULTS: mPAP and RV/(LV+S) increased significantly in the hypoxia group compared with normal controls (P<0.01). The muscularization of small pulmonary vessels and the relative medial thickness of pulmonary arteries increased obviously in the hypoxia group compared with those in the normal control group (P<0.01). Meanwhile, the expression levels of collagen I, collagen III and TGF-ß of pulmonary arteries in the hypoxia group increased markedly compared with those in the normal control group. However, mPAP and RV/(LV+S) were significantly reduced in the ADM-treated hypoxia group compared with those in the hypoxia group (P<0.01). ADM ameliorated pulmonary vascular structural remodeling of hypoxic rats, with a decrease in the expression of collagen I, collagen III and TGF-ß of pulmonary arteries. CONCLUSIONS: ADM might play a regulatory role in the development of hypoxic pulmonary hypertension and hypoxic pulmonary vascular remodeling, through inhibiting the expression of TGF-ß and alleviating the collagen accumulation of pulmonary arteries.

[Clinical characteristics and follow-up study of tachycardia-induced cardiomyopathy in 12 children].

OBJECTIVE: Tachycardia induced cardiomyopathy (TIC), secondary to various tachyarrhythmias, is a reversible condition which can lead to cardiac enlargement and heart failure. The impairment of both structure and function of heart can be reverted completely or partially if tachyarrhythmias are ceased without delay. This study aimed to explore the clinical characteristics, therapeutic regimen and outcome of TIC in children. METHODS: Clinical data of 12 children with TIC, who came from Peking University First Hospital from Feb. 2003 to Jun. 2009, were retrospectively analyzed and followed up. The echocardiogram data on admission were compared with those from 12 homochronous cases with idiopathic dilated cardiomyopathy matched with 12 TIC cases in age and gender. RESULTS: Atrial tachycardia is the commonest arrhythmia in 12 TIC cases (75%). Four cases underwent catheterization for radiofrequency ablation and all succeeded. The cardiac rhythm of 6 out of 8 cases treated with drugs became sinus rhythm after 3 days to 2 weeks antiarrhythmic drugs treatment. The remaining 2 cases still retained atrial rhythm, but the ventricular heart rates declined to normal. The left ventricular end-diastolic dimensions of the 12 cases were decreased compared with those of pretherapy [(37.5 ± 5.3) mm vs. (43.0 ± 5.7) mm, P < 0.01], and the left ventricular ejection fractions were increased [(60.5% ± 5.6%) vs. (33.7% ± 10.3%), P < 0.01], after (3.4 ± 2.3) months. In our (4.3 ± 2.4) year-follow-up, all cases were fine, except in one case the tachyarrhythmia relapsed because of discontinuation of the drug treatment by her parents. The left ventricular end-diastolic dimensions in 12 TIC cases were smaller than those of the 12 age- and gender-matched idiopathic dilated cardiomyopathy [(43.0 ± 5.7) mm vs. (54.8 ± 7.5) mm, t = 7.9, P < 0.01], and the ejection fractions were higher [(33.7% ± 10.3%) vs. (21.8% ± 7.5%), t = 3.7, P < 0.01]. CONCLUSION: The diagnosis of TIC should be considered for the children with tachycardia, cardiac enlargement and cardiac insufficiency. The degree of cardiac enlargement and cardiac insufficiency might be of value for the differential diagnosis between TIC and idiopathic dilated cardiomyopathy. The rhythm control and ventricular rates control could all result in a favorite therapeutic efficacy.