![]() ![]() Tachycardia does not exceed programmed upper limit rate on pacemaker.Most commonly: paced ventricular beat -> retrograde AV node conduction -> intrinsic P wave -> device reacts to intrinsic P wave by looking for intrinsic QRS, but since AV node is now refractory it delivers a paced beat at the programmed P-R interval (typically ~200-250ms), starting the process anew.Formation of a re-entrant circuit causing inappropriate tachycardia.Potentially life-threatening as it can cause V-Fib or (paradoxically) bradycardia due to failure to capture.Signals generated by interaction of different portions of the pacing system.Physiologic electrical activity (T waves, muscle potentials). ![]() New intrinsic arrhythmia (AF has a smaller depolarization than sinus beat), AMI, electrolyte abnormalities, lead separation, battery depletion.Voltages of patient's intrinsic QRS complex is too low to be detected.Failure to sense results in a paced beat on top of an intrinsic beat (as the device is "unaware" of the intrinsic beat").Normal function: a sensed myocardial depolarization greater than the programmed threshold causes inhibition of pacing.Crosstalk - type of oversensing where the ventricular lead senses atrial pacing stimulus, and ventilator output inhibited.Oversensing - most common cause: retrograde P’s, T’s, skeletal muscle myopotentials,.Failure to deliver a stimulus to the heart.Technical - insufficient device output, lead dislodgment, fracture, insulation defect, ventricular wall perforation.Medical - drugs, myocardial disease, electrolytes.Functional - refractory myocardium, desensitized local tissue around the lead.Delivery of pacing stimulus without depolarization.Twiddler Syndrome after large pocket and defibrillator wires coiled around the generator Typically occurs shortly after placement.2% local wound infection 1% sepsis/bacteremia.Unipolar Cautery - can cause sensing and pacing malfunction as well as reprogrammingĭifferential Diagnosis Pacemaker Malfunction Problems with pocket.Cardioversion: Use AP pads >8cm from device to minimize adverse effects.MRI: mostly safe, consult cards on device specific recs.Airport security: may trigger alarm, no alteration of activity.Cell phones: do not interact with device.Manufacturer code on pulse generator is visible on Chest Xray.Boston Scientific Inc.: 100 bpm 85 bpm when battery is ready for replacement.Jude Medical Inc.: 98.6 bpm 86.3 bpm when battery is ready for replacement Medtronic Inc.: 85 bpm 65 bpm when battery is ready for replacement. ![]() Magnet mode - with placement of a magnet over the device, the mode changes to asynchronous (i.e.(recently acquired by Abbott, Inc.) (1-80) ![]()
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