S2W4 Pacing Q& A MT

ADD IMAGES

Questions and Answers Overview

Question 1: Patient Device Requirements

  • Atrial Only Device:

    • Indicated for young patients with sino-atrial disease that have good AV node conduction.

  • RV Only Device:

    • Recommended for pacing in patients who are in permanent Atrial Fibrillation (AF).

  • Dual Device:

    • Suitable for all other patient populations.

Question 2: Advantages of Single Chamber Device

  • Benefits:

    • Simpler implantation process.

    • Lower initial cost of device.

  • Important Consideration:

    • Dual devices provide additional protection against future AV node involvement.

    • Current medical practice has shifted towards utilizing the dual system.

Clinical Observations

  • Clinical evidence shows increased left atrial diameter, decrease in left ventricular (LV) fractional shortening, and increased AF incidence in patients with DDD/R pacing compared to single chamber atrial devices (Reference: "Atrial pacing, the forgotten pacing mode" by M. EL Gamal).

Question 3: Mode Switch in Pacemakers

  • Functionality:

    • Mode switch prevents the pacemaker from tracking rapid atrial tachycardias or other rapid signals (which can be artifact).

    • Reduces adverse hemodynamic effects and patient symptoms.

  • Historical Context:

    • Originally, paroxysmal atrial tachycardias were contraindications for DDD devices.

Question 4: ECG Interpretation

  • Atrial Pacing:

    • Observations from ECG lead II.

Question 4 (Continued): Additional ECG Interpretation

  • DDD System:

    • Identifying both atrial and ventricular pacing in ECG leads (aVR, aVL, V₁).

Question 5: Sensing Issues in Pacemakers

  • Undersensing:

    • Occurs when pacemaker fails to detect the intrinsic rhythm, causing asynchronous pacing.

    • ECG finding: Pacing spikes seen within QRS complexes, or QRS complexes present without clock reset.

  • Oversensing:

    • Occurs when non-cardiac signals (like large P/T waves) are incorrectly recognized as intrinsic rhythms, leading to inhibited pacing.

Question 6: Pacing Problems

  • Output Failure:

    • Occurs when expected paced stimulus is not generated, leading to reduced or absent pacing function.

    • Causes include oversensing, wire fracture, lead displacement, and external interference.

  • Failure to Capture:

    • Occurs when the pacing stimulus does not depolarize cardiac tissue (spike without QRS complex or P wave).

    • Causes include electrode displacement, wire fracture, electrolyte disturbances, myocardial infarction.

Question 7: Issues Caused by Pacemakers

  1. Pacemaker-Mediated Tachycardia (PMT):

    • A re-entry tachycardia involving antegrade conduction via the pacemaker with retrograde conduction through the AV node.

    • Results from retrograde P waves being detected as intrinsic activity leading to paced ventricular contractions, causing a continuous cycle of tachycardia.

  2. Pacemaker Syndrome:

    • Arises from poor timing between atrial and ventricular contractions, leading to AV dyssynchrony.

    • Symptoms include fatigue, dizziness, palpitations, pre-syncope, and significant BP drops during rhythm changes.

  3. Lead Displacement Dysrhythmia:

    • Occurs when a pacing lead dislodges, causing irregular stimulation of the myocardium (ventricular ectopics or VT).

    • Diagnosis confirmed via chest x-ray.

Question 8: ECG Analysis

  • Observation:

    • A ventricular paced rhythm with intermittent failure to capture is noted.

    • Atrial sensing appears operational (spikes follow each P wave) but there is a complete heart block or high-grade 2nd degree AV block as intrinsic P waves don’t capture ventricles.