INTRODUCTION To examine and compare biocompatibility, osteocompatibility, rate of resorption, and remodelling dynamics of 2 calcium phosphate cements in comparison with a well-established hydroxyapatite ceramic. MATERIALS AND METHODS In a randomised fashion, Bone Source™, Cementek™, and Endobon™ were implanted bilaterally into the proximal metaphyseal tibiae of 35 Göttinger minipigs in a dire...

Ventricular fibrillation is the cause of the most sudden mortalities. Restitution is one of the specific properties of ventricular cell. The recent findings have clearly proved the correlation between the slope of restitution curve with ventricular fibrillation. This; therefore, mandates the modeling of cellular restitution to gain high importance. A cellular automaton is a powerful tool for si...

BACKGROUND Regional differences in action potential duration (APD) restitution in the heart favour arrhythmias, but the mechanism is not well understood. METHODS We simulated a 150 x 150 mm 2D sheet of cardiac ventricular tissue using a simplified computational model. We investigated wavebreak and re-entry initiated by an S1S2S3 stimulus protocol in tissue sheets with two regions, each with d...

We examine the utility of the action potential (AP) duration (APD) restitution curve slope in predicting the onset of electrical alternans when electrotonic and memory effects are considered. We develop and use two ionic cell models without memory that have the same restitution curve with slope >1 but different AP shapes and, therefore, different electrotonic effects. We also study a third cell...

Selvaraj RJ, Picton P, Nanthakumar K, Chauhan VS. Steeper restitution slopes across right ventricular endocardium in patients with cardiomyopathy at high risk of ventricular arrhythmias. Am J Physiol Heart Circ Physiol 292: H1262–H1268, 2007. First published November 10, 2006; doi:10.1152/ajpheart.00913.2006.—Steep action potential duration (APD) restitution slopes ( 1) and spatial APD restitut...

BACKGROUND An action potential duration (APD) restitution curve with a steep slope ≥1 has been associated with increased susceptibility for malignant ventricular arrhythmias. We aimed to evaluate the "restitution hypothesis" and tested ventricular APD restitution slope as well as effective refractory period (ERP)/APD ratio for long-term prognostic value in patients with ischemic (ICM) or dilate...

Hao, Steven C., David J. Christini, Kenneth M. Stein, Peter N. Jordan, Sei Iwai, Orville Bramwell, Steven M. Markowitz, Suneet Mittal, and Bruce B. Lerman. Effect of -adrenergic blockade on dynamic electrical restitution in vivo. Am J Physiol Heart Circ Physiol 287: H390–H394, 2004. First published March 4, 2004; 10.1152/ajpheart.00749.2003.—The slope of the action potential duration (APD) rest...

OBJECTIVES The authors sought to study mechanisms to explain why single premature atrial complexes (PACs) from the pulmonary veins (PVs) may initiate human atrial fibrillation (AF). BACKGROUND Theoretically, single PACs may initiate AF if the rate response of action potential duration (APD) restitution has a slope >1. However, human left atrial APD restitution and its relationship to AF have ...

We investigated the steepened dynamic action potential duration (APD) restitution of rats with pulmonary artery hypertension (PAH) and right ventricular (RV) failure and tested whether the observed APD restitution properties were responsible for negative mechanical restitution in these myocytes. PAH and RV failure were provoked in male Wistar rats by a single injection of monocrotaline (MCT) an...

Theoretical and experimental studies have shown that restitution of the cardiac action potential (AP) duration (APD) plays a major role in predisposing ventricular tachycardia to degenerate to ventricular fibrillation, whereas its role in atrial fibrillation is unclear. We used the Courtemanche human atrial cell model and the Luo-Rudy guinea pig ventricular model to compare the roles of electri...