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Long QT intervals predispose the patient to an R-on-T phenomenon, wherein the R-wave, representing ventricular depolarization, occurs during the relative refractory period at the end of repolarization (represented by the latter half of the T-wave). An R-on-T can initiate torsades. Sometimes, pathologic T-U waves may be seen in the ECG before ...
The cardiac pacemaker is the heart's natural rhythm generator. ... not their intrinsic rate in a phenomenon known as overdrive-suppression. Thus, in the normal ...
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An artificial cardiac pacemaker (or artificial pacemaker, so as not to be confused with the natural cardiac pacemaker) or just pacemaker is an implanted medical device that generates electrical impulses delivered by electrodes to the chambers of the heart either the upper atria, or lower ventricles to cause the targeted chambers to contract and ...
Biventricular pacemaker. This pacemaker has three wires placed in three chambers of the heart. One in the atrium and two in either ventricle. It is more complicated to implant. [10] Rate-responsive pacemaker. This pacemaker has sensors that detect changes in the patient's physical activity and automatically adjust the pacing rate to fulfill the ...
The concept of "R on T ectopics" was further brought out by Katz in 1928. [30] This was called the "vulnerable period" by Wiggers and Wegria in 1940, who brought to attention the concept of the danger of premature ventricular beats occurring on a T wave. [citation needed] Another definition of VF was produced by Wiggers in 1940.
[17] [18] [19] The name pacemaker syndrome was first coined by Erbel in 1979. [18] [20] Since its first discovery, there have been many definitions of pacemaker syndrome, and the understanding of the cause of pacemaker syndrome is still under investigation. In a general sense, pacemaker syndrome can be defined as the symptoms associated with ...
Pacemaker cells, however, do not have a resting potential. Instead, immediately after repolarization, the membrane potential of these cells begins to depolarise again automatically, a phenomenon known as the pacemaker potential. Once the pacemaker potential reaches a set value, the threshold potential, it produces an action potential. [2]