The onset of ventricular fibrillation (VF) has been associated with steep action potential duration restitution in both clinical and computational studies. Recently, detailed clinical restitution properties in cardiac patients were reported showing a substantial degree of heterogeneity in restitution slopes at the epicardium of the ventricles. The aim of the present study was to investigate the...

We study numerically the dynamics of spiral waves in an excitable medium with negative restitution. For our study we use two models of the excitable medium: a cellular automaton and a reaction-diffusion model. There are no significant effects of negative restitution as long as the slope of the restitution curve is less steep than -1. In media with slopes steeper than -1, the dynamics of spiral ...

BACKGROUND We tested the hypothesis that action potential duration (APD) restitution of normal ventricular muscle cells is different during double premature stimuli (S3) compared with a single premature stimulus (S2). We propose a possible ionic mechanism for such a difference. METHODS AND RESULTS Action potentials and isometric tension were recorded simultaneously from isolated canine right ...

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...

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...

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...

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...

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 ...