Indeed, it is now possible to program in all contemporary pacemakers an automatic measurement function of the ventricular threshold more or less associated with an automatic adjustment of the pacing amplitude. In this setting, the Capture Management function must be discussed. In dialysis patients, electrolyte conditions (serum sodium, serum calcium, serum potassium, blood glucose) constantly change with possible variations in pacing thresholds, requiring that the pacing outputs be regularly monitored and modified accordingly in order to efficiently capture the myocardium. This patient was programmed with a pacing amplitude of 2.5 Volts for 0.4 ms. This safety margin is designed to take into account the circadian variations in the pacing threshold which is influenced in variable manner from one subject to another by sleep, meals, physical activity, fever, etc. It is generally recommended to set a safety margin of 100% which corresponds to a double threshold voltage. The determination of the pacing threshold is of major importance since the programming of the voltage and the duration of the pulse defines the safety margin and determines the energy consumption of the prosthesis and therefore the rate of battery wear. It can be measured in voltage (Volts) or in pulse width (milliseconds). The pacing threshold corresponds to the smallest electrical pulse, delivered outside of all natural refractory periods, capable of generating the propagation of a depolarization. continued absence of ventricular capture.ineffective ventricular pacing the ensuing QRS is not detected this does not correspond to a sensing defect this QRS falls into the post-ventricular pacing ventricular blanking period, an absolute ventricular refractory period and is therefore not detected.
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