Effect of Digoxin on Ventricular Remodeling and Responsiveness of beta-Adrenoceptors in Chronic Volume Overload

Galectin-3 is associated with left ventricular reverse remodeling and outcome after percutaneous mitral valve repair

BACKGROUND

Plasma Galectin-3 is a marker of myocardial inflammation and fibrosis, was associated with left ventricular (LV) reverse remodeling after conventional surgical mitral valve repair (MVR) and predicted clinical events in patients undergoing transcatheter aortic valve replacement (TAVR). We aimed to evaluate the association between pre-interventional Galectin-3 levels and (1) reverse LV remodeling and (2) major adverse cardiovascular events (MACE) in patients undergoing percutaneous MVR.

METHODS

Forty-four consecutive patients (median age 79 years, LV ejection fraction 39.5 ± 11.4%, 91% in NYHA functional class ≥III) with symptomatic moderate to severe mitral regurgitation undergoing percutaneous MVR were prospectively included. Plasma Galectin-3 levels were measured before the procedure. Echocardiographic and clinical assessment was performed at baseline and after 3 months. LV reverse remodeling was prospectively defined as a ≥10% increase in global longitudinal strain. MACE included death, myocardial infarction, heart failure related rehospitalization and stroke and was assessed after a mean follow-up time of 2 years.

RESULTS

72.7% of the patients showed LV reverse remodeling. Pre-interventional Galectin-3 < 10 ng/ml was an independent predictor of LV reverse remodeling (OR 10.3, 95% CI 1.2-83.9, p = 0.036). 25 patients (56.8%) experienced a MACE. Patients with Galectin-3 levels ≥ 10 ng/ml had significantly more MACE than patients with Galectin-3 levels < 10 ng/ml (100% vs. 45.5%, p = 0.003). Diabetes independently predicted MACE (HR 3.1, 95% CI 1.0-9.4, p = 0.049); Galectin-3 ≥ 10 ng/ml was of borderline significance (HR 2.2, 95% CI 0.9-5.4, p = 0.088).

CONCLUSIONS

Pre-interventional plasma Galectin-3 levels are associated with LV reverse remodeling and with clinical outcome after percutaneous MVR.

Dobutamine stress echocardiography in healthy adult male rats

BACKGROUND

Dobutamine stress echocardiography is used to investigate a wide variety of heart diseases in humans. Dobutamine stress echocardiography has also been used in animal models of heart disease despite the facts that the normal response of healthy rat hearts to this type of pharmacological stress testing is unknown. This study was performed to assess this normal response.

METHODS

15 normal adult male Wistar rats were evaluated. Increasing doses of dobutamine were infused intravenously under continuous imaging of the heart by a 12 MHz ultrasound probe.

RESULTS

Dobutamine stress echocardiography reduced gradually LV diastolic and systolic dimensions. Ejection fraction increased by a mean of +24% vs. baseline. Heart rate increased progressively without reaching a plateau. Changes in LV dimensions and ejection fraction reached a plateau after a mean of 4 minutes at a constant infusion rate.

CONCLUSION

DSE can be easily performed in rats. The normal response is an increase in heart rate and ejection fraction and a decrease in LV dimensions. A plateau in echocardiographic measurements is obtained after 4 minutes of a constant infusion rate in most animals.

Upregulation of beta-adrenergic receptors in heart failure due to volume overload

To examine the mechanisms of changes in beta-adrenergic signal transduction in heart failing due to volume overload, we studied the status of beta-adrenoceptors (beta-ARs), G protein-coupled receptor kinase (GRK), and beta-arrestin in heart failure due to aortocaval shunt (AVS). Heart failure in rats was induced by creating AVS for 16 wk, and beta-AR binding, GRK activity, as well as their protein content, and mRNA levels were determined in both left and right ventricles. The density and protein content for beta1-ARs, unlike those for beta2-ARs, were increased in the failing hearts. Furthermore, protein contents for GRK isoforms and beta-arrestin-1 were decreased in membranous fractions and increased in cytosolic fractions from the failing hearts. On the other hand, steady-state mRNA levels for beta1-ARs and GRK2, as well as protein content for Gbetagamma-subunits, did not change in the failing heart. Basal cardiac function was depressed; however, both in vivo and ex vivo positive inotropic responses of the failing hearts to isoproterenol were augmented. Treatment of AVS animals with imidapril (1 mg.kg(-1).day(-1)) or losartan (20 mg.kg(-1).day(-1)) retarded the progression of heart failure; partially prevented changes in beta1-ARs, GRKs, and beta-arrestin-1 in the failing myocardium; and attenuated the increase in positive inotropic effect of isoproterenol. These results indicate that upregulation of beta1-ARs is associated with subcellular redistribution of GRKs and beta-arrestin-1 in the failing heart due to volume overload. Furthermore, attenuation of alterations in beta-adrenergic system by imidapril or losartan may be due to blockade of the renin-angiotensin system in the AVS model of heart failure.