title: The correlation dimension of rat hearts in an experimentally controlled environment.
abstract: The electric response of several isolated rat hearts in a controlled environment was studied experimentally. The correlation dimension D(2) was estimated and was found to be between 4 and 6.5 when the response was nearly periodic. The variation of D(2) with the concentration of calcium was studied and a general trend of its increase with increasing concentration was found. Two types of ventricular fibrillation (VF) were observed, one that corresponds to a stochastic signal where D(2) is unbounded and the other to a low dimensional dynamical system with 3.5</=D(2)</=4. It was found also that for the heart the correlation dimension is only an approximate concept. A new method for the estimation of D(2), that is suitable for the case when it is only approximate was introduced. A surrogate data method suitable for the analysis of nearly periodic series was implemented. (c) 2000 American Institute of Physics.
authors.affiliation: Department of Internal Medicine A, Carmel Medical Center, 7 Michal St., Haifa 34362, Israel.
authors.forename: Guy
authors.initials: G
authors.lastname: Dori
authors.forename: Shmuel
authors.initials: S
authors.lastname: Fishman
authors.forename: S. A.
authors.initials: SA
authors.lastname: Ben-Haim