Preparations of right ventricular papillary muscle and false tendon (Purkinje fiber) were obtained from dog hearts, placed in a bath perfused with Tyrode solution, and observed both under control conditions and during exposure to lidocaine in concentrations from 1 × 10-7 to 5 × 10-4 mole/liter. Transmembrane voltages were recorded from both ventricular muscle (VM) and Purkinje fibers (PF) of spontaneously beating and electrically driven preparations. Low concentrations (1 × 10-6 and 1 × 10-5 mole/liter) attenuated or abolished phase 4 (diastolic) depolarization and spontaneous firing in PF without decreasing their diastolic excitability. Concentrations of 1 × 10-5 mole/liter produced maximal shortening of both action potential duration (APD) and effective refractory period (ERP) and made the ERP long relative to APD; the latter alteration was more prominent in VM. At concentrations ≤ 1 × 10-5 mole/liter, lidocaine either caused a slight increase or no change in peak maximum rate of phase 0 depolarization (Vmax) and membrane responsiveness, the relationship between transmembrane activation voltage (MAV) and Vmax of the resultant action potential; these concentrations had no significant effect on resting potential (RP) in VM, maximal diastolic transmembrane voltage (DTMVmax) in PF, or action potential amplitude in either fiber type.
J. Thomas Bigger Jr., William J. Mandel
Usage data is cumulative from May 2024 through May 2025.
Usage | JCI | PMC |
---|---|---|
Text version | 219 | 15 |
64 | 28 | |
Figure | 0 | 2 |
Scanned page | 578 | 63 |
Citation downloads | 50 | 0 |
Totals | 911 | 108 |
Total Views | 1,019 |
Usage information is collected from two different sources: this site (JCI) and Pubmed Central (PMC). JCI information (compiled daily) shows human readership based on methods we employ to screen out robotic usage. PMC information (aggregated monthly) is also similarly screened of robotic usage.
Various methods are used to distinguish robotic usage. For example, Google automatically scans articles to add to its search index and identifies itself as robotic; other services might not clearly identify themselves as robotic, or they are new or unknown as robotic. Because this activity can be misinterpreted as human readership, data may be re-processed periodically to reflect an improved understanding of robotic activity. Because of these factors, readers should consider usage information illustrative but subject to change.