![]() On the electrocardiogram, the ventricular rate is at the upper limit of the pacemakers range at 160-180 bpm. ![]() Sensor induced at tachycardia occurs when limb movement during exercise, rapid hyperventilation, vibrations, loud noises, fever, acidosis, or electrocautery during surgery causes the sensor of a modern pacemaker to fire at an inappropriately rapid rate. 'Failure to capture' is the inability of the pacemaker stimulus to depolarize the myocardium and is recognized on the ECG by visible pacemaker spikes not followed by P waves (if the electrode is located in the atrium) or QRS complexes (if the electrode is located in the right ventricle). On the EKG, it is observed as a tachycardia with ventricular pacing, in the case of atrial fibrillation can be seen irregular ventricular pacing. Onset of atrial tachycardia ( atrial flutter, atrial fibrillation or atrial tachycardia) that is tracked by the pacemaker. Tracking an Atrial Tachyarrhythmia by Dual Chamber Pacemaker Placing a magnet on the device results in the termination of tachycardia by suspending the atrial sensing. The endless-loop tachycardia is observed on the electrocardiogram as a tachycardia with pacemaker pacing close to the maximum rate limited by the pacemaker programming. On the surface ECG, pacing spikes are present, but they are not followed by a QRS complex in the event of ventricular noncapture or by the lack of P waves in the event of atrial noncapture (Fig. The ventricular stimulus is conducted by the normal condution system (retrograde conduction ) and it is sensed as native atrial activity with subsequent ventricular pacing this ventricular stimulus returns to the atria by the normal condution system, closing the circuit. Capture failure occurs when the generated pacing stimulus does not initiate myocardial depolarization. It is a re-entrant tachycardia, which occurs in the dual-chamber pacemakers. The electrocardiogram shows a partial or total absence of pacemaker spikes despite the existence of conduction problems. Remember: The full or partial absence of spikes does not mean a problem of pacing, it can be inhibited by a patient's heart rhythm with a higher heart rate. Review the underlying mechanisms of malfunction of the pacemaker. Outline different ways in which a pacemaker typically malfunctions. The main causes are often the fracture or displacement of the lead, battery depletion, electrolyte disturbance or antiarrhythmic treatment (in these last two the function of the pacemaker is correct but is not able to stimulate the muscle). Objectives: Describe the basic functioning of a pacemaker. Pacing disorders occur when the electrical stimulation of the device does not occur or is not transmitted to the myocardium. Ventricular pacing spikes are not followed by QRS complexes. The dysfunctions of pacemakers can be classified in disorders of the stimulation (generation or transmission of the stimulus), or the sensing (absence or bad detection of cardiac stimulation). In these cases the electrocardiogram is the first tool with which we have to detect them. The electrical pacemaker, as every device, can present alterations in its operation.
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