Relationship between ejection phase indices of performance and myocardial functions during the development of pressure overload hypertrophy

Right ventricular gene therapy with a beta-adrenergic receptor kinase inhibitor improves survival after pulmonary artery banding

BACKGROUND

Increased right ventricular (RV) afterload results in RV hypertrophy and dysfunction, as well as increased levels of intracellular beta-adrenergic receptor kinase (betaARK1). We hypothesize that gene transfer of a betaARK1 inhibitor (betaARKct) may improve RV performance, morbidity, and mortality early after pulmonary artery (PA) banding.

METHODS

Rabbits underwent PA banding 3 days after right coronary artery injection of an adenovirus containing the gene encoding the betaARKct peptide (n = 14), beta-galactosidase (n = 10), or an empty adenovirus (n = 19). After banding, hemodynamic instability and maximal rate of increase in right ventricular pressure (RV dP/dt(max)) were documented. For 7 days after banding, animals were monitored for mortality, activity, and appetite.

RESULTS

When compared with controls, animals receiving the betaARKct transgene showed improvement in survival at 7 days (92.8% +/- 7% vs 48.3% +/- 9%, p = 0.01), less lethargy, a trend toward greater RV dP/dt(max) (NS), and increased hemodynamic stability at the time of banding (78% vs 41%, p = 0.03).

CONCLUSIONS

Selective RV expression of betaARKct improves survival and morbidity after PA banding. This represents a novel therapeutic modality for clinical situations involving increased RV afterload.

Simulation study on heart failure: effects of contractility on cardiac function

Using the model proposed by Beyar and Sideman, the effect of maximum isometric active stress at optimal sarcomere length (sigma 0) on left ventricular (LV) function was examined. Comparing the results of calculated LV function with those of reported experiments, sigma 0 was shown to be a potential indicator of myocardial contractility, and the model of Beyar and Sideman successfully predicted LV function with various myocardial contractilities. The LVP compensation curve, which describes the relationship between sigma 0 and maximum LV pressure, was then hypothesized. The combination of the Beyar-Sideman model and the LVP compensation curve enabled the prediction and approximation of the actual process of deterioration in heart failure. These models represent a step towards a fundamentally new concept in the current clinical situation of compensated heart failure and also in evaluating the process of heart failure.