Reversal effect of Zhigancao decoction on myocardial fibrosis in a rapid pacing-induced atrial fibrillation model in New Zealand rabbits.

OBJECTIVE: To evaluate the effect of Zhigancao decoction on reversal of right atrial myocardial fibrosis after rapid atrial pacing (RAP)-induced atrial fibrillation (AF). METHODS: New Zealand white rabbits were randomly divided into four groups: sham operation group (Group A: implanted electrodes, no RAP), pacing group (Group B: RAP-induced AF), Zhigancao soup water decoction Yin group (Group C: RAP-induced AF followed by Zhigancao soup Yin prescription twice a day for 30 days), and Zhigancao soup group (Group D: RAP-induced AF followed by Zhigancao water decoction twice a day for 30 days). The atrial myocardium was then examined for myocardial fibrosis by Masson staining, and protein expression of matrix metalloproteinase-9 (MMP-9) was immunohistochemically assessed. The right atrial appendage tissue field action potential duration (fAPD) was measured by microelectrode arrays. RESULTS: RAP successfully induced AF. Myocardial fibrosis was more severe in Groups B and C and less severe in Group D. Protein expression of MMP-9 was strongly positive in Groups B and C and weakly positive in Group D. The fAPD was significantly decreased in Groups B and C, but the decrease in Group D was not significant. CONCLUSION: Zhigancao decoction can reverse AF-induced myocardial fibrosis in rabbits and shorten the fAPD.

Microelectrode array measurement of potassium ion channel remodeling on the field action potential duration in rapid atrial pacing rabbits model.

BACKGROUND: Atrial fibrillation (AF) arises from abnormalities in atrial structure and electrical activity. Microelectrode arrays (MEA) is a real-time, nondestructive measurement of the resting and action potential signal, from myocardial cells, to the peripheral circuit of electrophysiological activity. This study examined the field action potential duration (fAPD) of the right atrial appendage (RAA) by MEA in rapid atrial pacing (RAP) in the right atrium of rabbits. In addition, this study also investigated the effect of potassium ion channel blockers on fAPD. METHODS: 40 New Zealand white rabbits of either sex were randomly divided into 3 groups: 1) the control, 2) potassium ion channel blocker (TEA, 4-Ap and BaCl2), and 3) amiodarone groups. The hearts were quickly removed and right atrial appendage sectioned (slice thickness 500 µm). Each slice was perfused with Tyrode's solution and continuously stimulated for 30 minutes. Sections from the control group were superfused with Tyrode's solution for 10 minutes, while the blocker groups and amiodarone were both treated with their respective compounds for 10 minutes each. The fAPD of RAA and action field action potential morphology were measured using MEA. RESULTS: In non-pace (control) groups, fAPD was 188.33 ± 18.29 ms after Tyrode's solution superfusion, and 173.91 ± 6.83 ms after RAP. In pace/potassium ion channel groups, TEA and BaCl2 superfusion prolonged atrial field action potential (fAPD) (control vs blocker: 176.67 ± 8.66 ms vs 196.11 ± 10.76 ms, 182.22 ± 12.87 ms vs 191.11 ± 13.09 ms with TEA and BaCl2 superfusion, respectively, P < 0.05). 4-AP superfusion significantly prolonged FAPD. In pace/amiodarone groups, 4-Ap superfusion extended fAPD. CONCLUSIONS: MEA was a sensitive and stable reporter for the measurement of the tissue action potential in animal heart slices. After superfusing potassium ion channel blockers, fAPD was prolonged. These results suggest that Ito, IKur and IK1 remodel and mediate RAP-induced atrial electrical remodeling. Amiodarone alter potassium ion channel activity (Ito, IKur, IK1 and IKs), shortening fAPD.

Implantable device recalls: are we throwing away the baby with the bath water?

Over the past year, there has been a sharp increase in the number of recalls, or `field safety corrective actions' concerning implantable defibrillators. This may be due to an actual rise in device or component-related problems (for which there is some evidence), overzealous reporting of potential problems (which is apparent), or most probably a combination of the two. In this day and age of increasing numbers of ICD implantations, it is essential that all concerned realise that ICDs are no more infallible than other man-made devices and that the incidence of complications is therefore likely to increase commensurately. It is also important to weigh the procedural risk of replacing the device against the risk not only of device failure, but more importantly related harm to the patient. Odds actually favour replacement in very few cases. Above all this demands critical attention to communication between stakeholders, medical, industry, patients and press. This article attempts to place a number of these issues in some perspective, and offer future directions for management of ICD recalls and safety actions.