Objectives To compare the frequency-dependent effects of amiodarone （Ami） on ventricular electrophysiology in fight ventricular rapid pacing-induced congestive heart failure （CHF） canine models. Methods Thirty-two...Objectives To compare the frequency-dependent effects of amiodarone （Ami） on ventricular electrophysiology in fight ventricular rapid pacing-induced congestive heart failure （CHF） canine models. Methods Thirty-two dogs were randomized into four groups： the control group, the Ami group in which the normal dogs were given Ami orally 300 mg a day for 4 -5 weeks, the CHF group induced by right ventricular rapid pacing （240 pulses, min^- 1 for 4 -5 weeks ）, and the group of CHF dogs fed with Ami orally 300 mg a day for 4 - 5 weeks. The techniques of electrical stimulation and monophasic action potential （MAP） recording were used in the electrophysiology studies. Results The effects of Ami on ventricular MAP duration （MAPD90） and effective refractory period （VERP） were not frequency-dependent in CHF dogs. There was also no frequency-dependent effect on the increase in the ratio of VERP to MAPD90 （ VERP/MAPD90 ）. The prolongation of ventricular conduction time was frequencydependent. Conclusions The frequency-dependent effects of Ami on ventricular electrophysiology in CHF dogs were similar to that in normal dogs.展开更多
Background Some studies have confirmed that the right ventricular walls of most rodents, such as canines and humans, have evident transient outward potassium current (I to1) heterogeneity, and this heterogeneity i...Background Some studies have confirmed that the right ventricular walls of most rodents, such as canines and humans, have evident transient outward potassium current (I to1) heterogeneity, and this heterogeneity is closely related to J point elevation, J wave formation, and some ventricular tachycardias such as ventricular fibrillations caused by Brugada syndrome. This study is designed to investigate transmural electrical heterogeneity of the canine right ventricle during repolarization (phase 1) from the viewpoint of 4-aminopyridine sensitive and calcium-independent I to1. Methods Adult canine single right ventricular epicardial (Epi) cells, mid-myocardial (M) cells, and endocardial (Endo) cells were enzymatically dissociated. Whole cell voltage-clamp recordings were made to compare the I to1 values of the three cell types. Results At 37℃ and using 0.2 Hz and +70 mV depolarizing test potentials, the average peak I to1 values of Epi cells and M cells averaged (4070±1720) pA and (3540±1840) pA, respectively. The activated and inactivated Epi and M cells kinetic processes were in accordance with the Boltzmann distribution. Compared with I to1 in Epi cells and M cells, the average peak I to1 in Endo cells was very low, averaged (470±130) pA. Conclusions These results suggest that there are evident differences and potent gradients in I to1 between the three cardiac cell types, especially between Epi and Endo cells. These differences are among the prominent manifestations of right ventricular electrical heterogeneity, and may form an important ionic basis and prerequisite for some malignant arrhythmias in the right ventricle, including those arising from Brugada syndrome and other diseases.展开更多
文摘Objectives To compare the frequency-dependent effects of amiodarone （Ami） on ventricular electrophysiology in fight ventricular rapid pacing-induced congestive heart failure （CHF） canine models. Methods Thirty-two dogs were randomized into four groups： the control group, the Ami group in which the normal dogs were given Ami orally 300 mg a day for 4 -5 weeks, the CHF group induced by right ventricular rapid pacing （240 pulses, min^- 1 for 4 -5 weeks ）, and the group of CHF dogs fed with Ami orally 300 mg a day for 4 - 5 weeks. The techniques of electrical stimulation and monophasic action potential （MAP） recording were used in the electrophysiology studies. Results The effects of Ami on ventricular MAP duration （MAPD90） and effective refractory period （VERP） were not frequency-dependent in CHF dogs. There was also no frequency-dependent effect on the increase in the ratio of VERP to MAPD90 （ VERP/MAPD90 ）. The prolongation of ventricular conduction time was frequencydependent. Conclusions The frequency-dependent effects of Ami on ventricular electrophysiology in CHF dogs were similar to that in normal dogs.
文摘Background Some studies have confirmed that the right ventricular walls of most rodents, such as canines and humans, have evident transient outward potassium current (I to1) heterogeneity, and this heterogeneity is closely related to J point elevation, J wave formation, and some ventricular tachycardias such as ventricular fibrillations caused by Brugada syndrome. This study is designed to investigate transmural electrical heterogeneity of the canine right ventricle during repolarization (phase 1) from the viewpoint of 4-aminopyridine sensitive and calcium-independent I to1. Methods Adult canine single right ventricular epicardial (Epi) cells, mid-myocardial (M) cells, and endocardial (Endo) cells were enzymatically dissociated. Whole cell voltage-clamp recordings were made to compare the I to1 values of the three cell types. Results At 37℃ and using 0.2 Hz and +70 mV depolarizing test potentials, the average peak I to1 values of Epi cells and M cells averaged (4070±1720) pA and (3540±1840) pA, respectively. The activated and inactivated Epi and M cells kinetic processes were in accordance with the Boltzmann distribution. Compared with I to1 in Epi cells and M cells, the average peak I to1 in Endo cells was very low, averaged (470±130) pA. Conclusions These results suggest that there are evident differences and potent gradients in I to1 between the three cardiac cell types, especially between Epi and Endo cells. These differences are among the prominent manifestations of right ventricular electrical heterogeneity, and may form an important ionic basis and prerequisite for some malignant arrhythmias in the right ventricle, including those arising from Brugada syndrome and other diseases.
