Abstract 567: Ivabradine Improved Cardiac Function, Fibrosis And Hyperexcitability In Rat Post-myocardial Infarction Severe Heart Failure.
The selective sinus node If current inhibitor Ivabradine (Iva) reduces heart rate (HR) without any other hemodynamic effects. We investigated in a rat model of post-MI severe heart failure, the effects of a chronic Iva administration on LV function, structure and electrical remodelling.
Methods. MI was induced by coronary artery ligation in adult rats: echocardiography and Holter ECG were performed 2 months (m) after MI i.e. before randomization (n=12/group) into MI and MI+Iva (10 mg/kg/d) groups, and 3 m later. In ventricles, collagen was quantified after Sirius red staining of section and ACE and AT1-receptor mRNA expression (normalized to GAPDH) was assayed by RT-PCR.
Results: 2m-post MI, all rats displayed severe decreased LVEF, and increased LVEDP compared to sham-operated (28%±3 vs 66%±5 and 32±2 vs 10±1 mmHg, respectively; p<0.05). In 5m-post-MI, LVEF and LVEDP were stabilized with Iva (31±1% and 24±2 mmHg), while they were worsened in MI groups (21±3% and 38±2mmHg). Blood pressure, body and heart weights were similar in MI and MI+Iva. Iva reduced HR (RR: 201±5 vs 179±3 ms in MI; p<0.05) and ventricular premature beats (514±152 vs 4717±1363/day for MI; p<0.05), and improved HR variability (SDRR: 5±1.5 vs 3.9± 0.6 for MI; p<0.05). There were no effects of Iva on duration (ms) of PR (45±3 vs 44±3), QRS (51±3 vs 46±3) and QT (106±7 vs 99±6, for MI and MI+Iva, respectively). The increased ventricular collagen in MI (4.0±0.1 vs 0.8±0.2 % in sham; p<0.05) was markedly reduced in MI+Iva (1.8±0.1%, p<0.0001 vs MI). The increases in ventricular gene expression of ACE and AT-1 receptor in MI rats (2.5 and 6 folds versus sham operated, respectively, p<0.05) were completely blunted by Iva treatment.
Conclusion: Iva treatment of the post-MI heart failure: 1-markedly reduced HR and ventricular excitability and without harmful effects on conduction; 2-prevented worsening of LV dysfunction and remodelling, and 3- induced a downregulation of cardiac RAAS transcripts. Thus, through its negative chronotropic effects, Iva allowed the maintenance of cardiac function below the threshold for a tissular RAAS stimulation even in severe post-MI cardiac failure. Such beneficial effects of Iva on cardiac remodelling open new perspectives for the treatment of severe heart failure