Modeling specific action potentials in the human atria based on a minimal single-cell model.

We present an effective method to model empirical action potentials of specific patients in the human atria based on the minimal model of Bueno-Orovio, Cherry and Fenton adapted to atrial electrophysiology. In this model, three ionic are currents introduced, where each of it is governed by a characteristic time scale. By applying a nonlinear optimization procedure, a best combination of the respective time scales is determined, which allows one to reproduce specific action potentials with a given amplitude, width and shape. Possible applications for supporting clinical diagnosis are pointed out.

Anatomical and spiral wave reentry in a simplified model for atrial electrophysiology.

For modeling the propagation of action potentials in the human atria, various models have been developed in the past, which take into account in detail the influence of the numerous ionic currents flowing through the cell membrane. Aiming at a simplified description, the Bueno-Orovio-Cherry-Fenton (BOCF) model for electric wave propagation in the ventricle has been adapted recently to atrial physiology. Here, we study this adapted BOCF (aBOCF) model with respect to its capability to accurately generate spatio-temporal excitation patterns found in anatomical and spiral wave reentry. To this end, we compare results of the aBOCF model with the more detailed one proposed by Courtemanche, Ramirez and Nattel (CRN model). We find that characteristic features of the reentrant excitation patterns seen in the CRN model are well captured by the aBOCF model. This opens the possibility to study origins of atrial fibrillation based on a simplified but still reliable description.

Longitudinal cohort study on the effectiveness of lipid apheresis treatment to reduce high lipoprotein(a) levels and prevent major adverse coronary events.

BACKGROUND: We investigated in a longitudinal, multicenter, cohort study whether combined lipid apheresis and lipid-lowering medication can reduce extremely high levels of lipoprotein(a) (Lp[a]) and thus prevent major adverse coronary events (MACE) more efficaciously than lipid-lowering medication alone. METHODS: Eligible patients had coronary artery disease and Lp(a) levels > or =2.14 micromol/l (95th percentile). All patients received lipid-lowering medications alone until maximally tolerated doses were no longer effective, followed by combined lipid apheresis and lipid-lowering medication. The rates of the primary outcome, MACE, were recorded for both periods. RESULTS: A total of 120 patients were included. The mean duration of lipid-lowering therapy alone was 5.6+/-5.8 years, and that of apheresis was 5.0+/-3.6 years. Median Lp(a) concentration was reduced from 4.00 micromol/l to 1.07 micromol/l with apheresis treatment (P<0.0001); the corresponding mean annual MACE rate per patient was 1.056 versus 0.144 (P<0.0001). CONCLUSIONS: Lowering of Lp(a) levels by apheresis was efficacious and safe, and we recommend this therapy for patients in whom maximally tolerated doses of medication alone have failed to control coronary artery disease-associated events.