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Chronic heart rate reduction by ivabradine prevents endothelial dysfunction in dyslipidaemic mice.

ABSTRACT: BACKGROUND AND PURPOSE: High resting heart rate is a predictor for total and cardiovascular mortality independent of other risk factors in patients with coronary artery disease. We tested the hypothesis that a reduction of resting heart rate with the cardiac pacemaker I(f) current inhibitor ivabradine prevents the endothelial dysfunction associated with dyslipidaemia. EXPERIMENTAL APPROACH: Three-month-old dyslipidaemic (DL) male mice expressing the human ApoB-100 were assigned or not (DL, n=16), to treatment for 3 months with ivabradine (10 mg kg(-1) d(-1), n=17). Wild-type C57Bl/6 mice (WT, n=15) were used as controls. Heart rate was measured at 3, 4.5 and 6 months. Dilatation to acetylcholine (ACh) of isolated cerebral and renal arteries was investigated at 6 months. KEY RESULTS: Heart rate remained stable in anaesthetized WT mice, increased (25%, P<0.05) with age in DL mice but was limited (11%, P<0.05) by ivabradine. At 6 months, left ventricular maximal pressure was similar in all groups. The minimal and end-diastolic left ventricular pressures were increased (P<0.05) in DL (10.2+/-1.0 and 18.7+/-1.4 mm Hg) compared to WT (-0.4+/-0.7 and 6.3+/-1.0 mm Hg) and reduced (P<0.05) by ivabradine (4.2+/-1.3 and 11.5+/-1.5 mm Hg). ACh-induced maximal dilatation was impaired (P<0.05) in renal and cerebral arteries isolated from DL compared to WT (56+/-7 versus 83+/-3% in renal arteries; 22+/-2 versus 42+/-2% in cerebral arteries). Ivabradine completely prevented (P<0.05) this dysfunction in renal and cerebral arteries. CONCLUSIONS AND IMPLICATIONS: Selective heart rate reduction with ivabradine limits cardiac dysfunction and prevents the renovascular and cerebrovascular endothelial dysfunction associated with dyslipidaemia.

SUBMITTER: Drouin A

PROVIDER: S-EPMC2439858 | biostudies-other | 2008 Jun

REPOSITORIES: biostudies-other

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Project description:Heart rates during ischaemia and reperfusion are possible determinants of reperfusion arrhythmias. We used ivabradine, a selective If current inhibitor, to assess the effects of heart rate reduction (HRR) during ischaemia-reperfusion on reperfusion ventricular arrhythmias and assessed potential anti-arrhythmic mechanisms by optical mapping. Five groups of rat hearts were subjected to regional ischaemia by left anterior descending artery occlusion for 8min followed by 10min of reperfusion: (1) Control n=10; (2) 1?M of ivabradine perfusion n=10; (3) 1?M of ivabradine+5Hz atrial pacing throughout ischaemia-reperfusion n=5; (4) 1?M of ivabradine+5Hz pacing only at reperfusion; (5) 100?M of ivabradine was used as a 1ml bolus upon reperfusion. For optical mapping, 10 hearts (ivabradine n=5; 5Hz pacing n=5) were subjected to global ischaemia whilst transmembrane voltage transients were recorded. Epicardial activation was mapped, and the rate of development of ischaemia-induced electrophysiological changes was assessed. HRR observed in the ivabradine group during both ischaemia (195±11bpm vs. control 272±14bpm, p<0.05) and at reperfusion (168±13bpm vs. 276±14bpm, p<0.05) was associated with reduced reperfusion ventricular fibrillation (VF) incidence (20% vs. 90%, p<0.05). Pacing throughout ischaemia-reperfusion abolished the protective effects of ivabradine (100% VF), whereas pacing at reperfusion only partially attenuated this effect (40% VF). Ivabradine, given as a bolus at reperfusion, did not significantly affect VF incidence (80% VF). Optical mapping experiments showed a delay to ischaemia-induced conduction slowing (time to 50% conduction slowing: 10.2±1.3min vs. 5.1±0.7min, p<0.05) and to loss of electrical excitability in ivabradine-perfused hearts (27.7±4.3min vs. 14.5±0.6min, p<0.05). Ivabradine administered throughout ischaemia and reperfusion reduced reperfusion VF incidence through HRR. Heart rate during ischaemia is a major determinant of reperfusion arrhythmias. Heart rate at reperfusion alone was not a determinant of reperfusion VF, as neither a bolus of ivabradine nor pacing immediately prior to reperfusion significantly altered reperfusion VF incidence. This anti-arrhythmic effect of heart rate reduction during ischaemia may reflect slower development of ischaemia-induced electrophysiological changes.

Project description:IntroductionIn the prospective, open-label multicenter INTENSIFY study, the effectiveness and tolerability of ivabradine as well as its impact on quality of life (QOL) in chronic systolic heart failure (CHF) patients were evaluated over a 4-month period.MethodsIn CHF patients with an indication for treatment with ivabradine, resting heart rate (HR), heart failure symptoms [New York Heart Association (NYHA) class, signs of decompensation], left ventricular ejection fraction, brain natriuretic peptide (BNP) values, QOL, and concomitant medication with focus on beta-blocker therapy were documented at baseline, after 4 weeks, and after 4 months. The results were analyzed using descriptive statistical methods.ResultsThousand nine hundred and fifty-six patients with CHF were included. Their mean age was 67 ± 11.7 years and 56.9% were male. 77.8% were receiving beta-blockers. Other concomitant medications included angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (83%), diuretics (61%), aldosterone antagonists (18%), and cardiac glycosides (8%). At baseline, the mean HR of patients was 85 ± 11.8 bpm, 51.1% and 37.2% of patients were classified as NYHA II and III, respectively, and 22.7% showed signs of decompensation. BNP concentrations were tracked in a subgroup, and values exceeding 400 pg/mL were noted in 53.9% of patients. The mean value of the European quality of life-5 dimensions (EQ-5D) QOL index was 0.64 ± 0.28. After 4 months of treatment with ivabradine, HR was reduced to 67 ± 8.9 bpm. Furthermore, the proportion of patients presenting with signs of decompensation decreased to 5.4% and the proportion of patients with BNP levels >400 pg/mL dropped to 26.7%, accompanied by a shift in NYHA classification towards lower grading (24.0% and 60.5% in NYHA I and II, respectively). EQ-5D index improved to 0.79 ± 0.21.ConclusionOver 4 months of treatment, ivabradine effectively reduced HR and symptoms in CHF patients in this study reflecting daily clinical practice. These benefits were accompanied by improved QOL and good general tolerability.

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Chronic heart rate reduction by ivabradine prevents endothelial dysfunction in dyslipidaemic mice.

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