Improvement of left ventricular filling by ivabradine during chronic hypertension: involvement of contraction-relaxation coupling

Three-vessel coronary infusion of cardiosphere-derived cells for the treatment of heart failure with preserved ejection fraction in a pre-clinical pig model

Heart failure with preserved ejection fraction (HFpEF) is a major public health concern. Its outcome is poor and, as of today, barely any treatments have been able to decrease its morbidity or mortality. Cardiosphere-derived cells (CDCs) are heart cell products with anti-fibrotic, anti-inflammatory and angiogenic properties. Here, we tested the efficacy of CDCs in improving left ventricular (LV) structure and function in pigs with HFpEF. Fourteen chronically instrumented pigs received continuous angiotensin II infusion for 5 weeks. LV function was investigated through hemodynamic measurements and echocardiography at baseline, after 3 weeks of angiotensin II infusion before three-vessel intra-coronary CDC (n = 6) or placebo (n = 8) administration and 2 weeks after treatment (i.e., at completion of the protocol). As expected, arterial pressure was significantly and similarly increased in both groups. This was accompanied by LV hypertrophy that was not affected by CDCs. LV systolic function remained similarly preserved during the whole protocol in both groups. In contrast, LV diastolic function was impaired (increases in Tau, LV end-diastolic pressure as well as E/A, E/E'septal and E/E'lateral ratios) but CDC treatment significantly improved all of these parameters. The beneficial effect of CDCs on LV diastolic function was not explained by reduced LV hypertrophy or increased arteriolar density; however, interstitial fibrosis was markedly reduced. Three-vessel intra-coronary administration of CDCs improves LV diastolic function and reduces LV fibrosis in this hypertensive model of HFpEF.

Therapeutic Use and Molecular Aspects of Ivabradine in Cardiac Remodeling: A Review

Cardiac remodeling can cause ventricular dysfunction and progress to heart failure, a cardiovascular disease that claims many lives globally. Ivabradine, a funny channel (I_f) inhibitor, is used in patients with chronic heart failure as an adjunct to other heart failure medications. This review aims to gather updated information regarding the therapeutic use and mechanism of action of ivabradine in heart failure. The drug reduces elevated resting heart rate, which is linked to increased morbidity and mortality in patients with heart failure. Its use is associated with improved cardiac function, structure, and quality of life in the patients. Ivabradine exerts several pleiotropic effects, including an antiremodeling property, which are independent of its principal heart-rate-reducing effects. Its suppressive effects on cardiac remodeling have been demonstrated in animal models of cardiac remodeling and heart failure. It reduces myocardial fibrosis, apoptosis, inflammation, and oxidative stress as well as increases autophagy in the animals. It also modulates myocardial calcium homeostasis, neurohumoral systems, and energy metabolism. However, its role in improving heart failure remains unclear. Therefore, elucidating its molecular mechanisms is imperative and would aid in the design of future studies.

Ivabradine improves left ventricular twist and untwist during chronic hypertension

BACKGROUND

Left ventricular (LV) dysfunction develops during LV hypertrophy and particularly during tachycardia. Thus we investigated the effects of heart rate (HR) reduction with ivabradine, an I_f-channel blocker, on LV twist and untwist which represents myocardial deformation occurring during the overall systole and diastole and therefore provide valuable evaluation of global LV systolic and diastolic function.

METHODS

Eight chronically instrumented pigs receiving continuous angiotensin II infusion during 28days to induce chronic hypertension and LV hypertrophy. Measurements were performed at Days 0 and 28 after stopping angiotensin II infusion in the presence and absence of ivabradine.

RESULTS

At Day 0, reducing HR from 75±3 to 55±2beats/min with ivabradine did not affect LV twist but slowed LV untwist along with an increase in LV end-diastolic pressure. At Day 28, LV posterior and septal wall thickness as well as the estimated LV mass increased, indicating LV hypertrophy. LV twist and untwist were significantly reduced by 33±4% from 16±1° and 32±6% from -154±9°/s, respectively, showing global LV systolic and diastolic dysfunction. In this context, ivabradine decreased HR by 25% from 86±5beats/min and significantly improved LV twist from 11±1 to 14±1° and LV untwist from -104±8 to -146±5°/s.

CONCLUSIONS

Administration of ivabradine during chronic hypertension and LV hypertrophy improved LV twist and untwist. This further supports the beneficial effect of this drug on both LV systolic and diastolic function during the development of LV hypertrophy.