Atrial refractory period

Atrial fibrillation leads to electrical remodeling of the atria. Episodes of AF that are of longer duration and episodes that occur with increasing frequency result in progressive shortening of atrial refractory periods, further potentiating the reentrant circuits in the atria.22 Therefore, it is often said that atrial... 

Moricizine does not affect the atrial refractory period or conduction velocity within atrial muscle. 

Ibutilide causes an increase in the atrial refractory period, an effect seen at rapid heart rates. 

There has been a great deal of interest in the nature of coronary sympathetic stimulation. Braunwald s group observed coronary vasodilation after the intracoronary Injection of isoproterenol and concluded that beta receptors are present in the coronary circulation. Gilmore has recently reported the presence of both alpha and beta receptors within the coronary vasculature. Govier found both alpha and beta receptors as evidenced by changes in atrial refractory period. Gaal and his associates have suggested that both alpha and beta receptors are present in the coronary vessels and that normally the beta response predominates. After blockade of the beta receptors, administration of epinephrine or norepinephrine results in stimulation of only alpha receptors which results in coronary... 

Postventiicular atrial refractory period Hysteresis rate... 

Atrial Refractory Period The atrial refractory period (ARP) (expressed in milliseconds) is the interval following a paced or sensed atrial event during which the pacemaker ceases to be responsive to detectable atrial signals. It contains two parts the absolute refractory and relative refractory periods (Fig. 3.16). 

Fig. 3.29 Loss of Biventricular Pacing. On the Y axis the atrial rate is shown. As the atrial rate exceeds the LRL, biventricular pacing is maintained. However, when the atrial rate reaches the TARP, which equals the sum of the PVARP and the AV interval, biventricular pacing will stop. However, biventricular pacing will not resume even after the atrial rate falls until the atrial rate reaches the intrinsic total atrial refractory period (ITARP), which is the sum of the PVARP and the PR interval. From Wang PJ, Kramer A, Estes NAM III, Hayes DL. Timing cycles for biventricular pacing. PACE 2002 25 52-75. (12).

Lau CP, Tai YT, Fong PC, Li IP, Chung EL. Atrial arrhythmia management with sensor controlled atrial refractory period and automatic mode switching in patients with minute ventilation sensing dual chamber rate adaptive pacemakers. Pacing Clin Electrophysiol. 1992 15 1504-1514. 

Fig. 12.2 An example of atrial fibrillation (AF) organizing into atrial flutter. A. The upper strip in the top panel demonstrates the atrial electrogram (EGM) and the lower strip demonstrates the annotated markers indicating how the pacemaker classifies each atrial and ventricular event as well as the cycle length (in ms) between each interval. The atrial electrogram shows the rapid irregular atrial rhythm which subsequently transitions into an organized atrial tachycardia. B. Atrial antitachycardia pacing (ATP) therapy - a burst train followed by two premature extrastimuli is delivered restoring atrial paced rhythm. The marker channel notations indicate how the device classifies each beat. Inter-beat intervals are also shown (in ms). AP - atrial paced event VP - ventricular paced event AR - atrial event sensed in atrial refractory period FS - AF sensed event TD - tachycardia detected TS - tachycardia sensed event. Courtesy AM Gillis.

Levine PA, Postventricular atrial refractory periods and pacemaker mediated tachycardias, Clin Prog Pacing Electrophysiol 1983 1 394-401. 

For frequent PACs drugs that prolong atrial refractory period, such as beta-adrenergic blockers and calcium channel blockers... 

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