To explore the effects of tetramethylpyrazine (TMP) on fibrosis of atrial tissue and atrial fibrillation in a canine model of congestive heart failure (CHF) induced by ventricular tachypacing.
Twenty-one healthy mongrel dogs were randomly divided into three groups, which were normal control group, untreated group and TMP-treated group. Atrial fibrillation (AF) was induced by burst of atrial pacing, after the canine model of CHF was established. The atrial tissues were sampled and stained with Mallory’s trichromic stains, then the fibrosis in the atrial tissues was analyzed. The left ventricular ejection fraction (LVEF) was evaluated by echocardiography. The levels of angiotensin Ⅱ (AngⅡ), aldosterone (ALD), amino-terminal peptide of type Ⅲ procollagen (PⅢNP),laminin (LN) and hyaluronic acid (HA) in peripheral blood were examined by radioimmunoassay.
The LVEF was significantly decreased in the untreated group as compared with that in the normal control group (P＜0.01）, while the frequencies of AF and sustaining AF were significantly increased and the AF duration was obviously prolonged in the untreated group as compared with those in the normal control group (P＜0.01）. The fibrosis degree in the left or right atrial tissue in the untreated group was more serious than that in the normal control group (P＜0.01). The AF duration was positively correlated with the fibrosis degree in the left atrial tissue (r=0.84, P=0.018). The levels of AngⅡ, ALD, PⅢNP and HA in peripheral blood were significantly higher in the untreated group than those in the normal control group (P＜0.05 or P＜0.01). The level of AngⅡ was positively correlated with the level of ALD in peripheral blood (r=0.759, P=0.048). The LVEF and the frequency of sustaining AF were both significantly improved in the TMP-treated group as compared with those in the untreated group (P＜0.05). The fibrosis in the left or right atrial tissue in the untreated group was more serious than that in the untreated group (P＜0.01). The levels of AngⅡ and PⅢNP in peripheral blood were also markedly higher in the TMP-treated group than those in the untreated group (P＜0.05, P＜0.01).
Tetramethylpyrazine has the effect of reducing the fibrosis degree of atrial tissue in dogs with CHF, and this efficacy may be related to the mechanism of decreasing the frequency of AF and shortening the AF duration.