Pacemaker complication
(Redirected from Ventricular paced)
Background
- All ICDs are also pacemakers (i.e. have pacing functionality), but not all pacemakers are ICDs (i.e. do not have shocking functionality)
Nomenclature
| I | II | III | IV | V |
|---|---|---|---|---|
| Chamber(s) paced | Chamber(s) sensed | Response to sensing | Rate modulation | Multisite pacing |
| O = None | O = None | O = None | O = None | O = None |
| A = Atrium | A = Atrium | T = Triggered | R = Rate modulation | A = Atrium |
| V = Ventricle | V = Ventricle | I = Inhibited | V = Ventricle | |
| D = Dual (A+V) | D = Dual (A+V) | D = Dual (T+I) | D = Dual (A+V) |
Indications
- Sinus Node Dysfunction-sinus bradycardia/arrest, sinoatrial block, chronotropic incompetence, a-fib.
- Acquired AV block- 3rd degree block and 2nd degree type II
- Chronic Bifascicular or Trifascicular block
- After Acute MI-high mortality with persistent AV block post MI
- Cardiac Resynchronization Therapy- Conduction delay (>150msec with mortality benefit) in chronic systolic heart failure further decreases EF, increases remodeling and increased MR.
- Neurocardiogenic Syncope and Carotid Sinus Syndrome
Lead Location
- Atrial
- Right Atrial Appendage
- Lateral RA wall
- Right Ventricle
- Apex
- Septum
- Left Ventricle (most commonly placed for cardiomyopathy or CHF)
- Coronary veins along external LV wall via coronary sinus
- Rarely, externally placed electrode during open surgical procedure
Additional Pacemaker Functions
- Can record rhythm strips of AF, VT, and VF episodes for later review
- Keeps track of % of paced vs intrinsic beats
- Keeps a rate histogram, as well as % of time spent in AF
Methods to Identify Manufacturer
- Patient most often has a pocket card indicating manufacturer
- Manufacturer Hotline has patient database
- Medtronic Inc. (1-800-328-2518)
- St. Jude Medical Inc. (recently acquired by Abbott, Inc.) (1-800-722-3774)
- Boston Scientific Inc. (1-800-227-3422)
- Magnet mode - with placement of a magnet over the device, the mode changes to asynchronous (i.e. DOO or VOO). Each brand has slightly different rates
- Medtronic Inc.: 85 bpm; 65 bpm when battery is ready for replacement
- St. Jude Medical Inc.: 98.6 bpm; 86.3 bpm when battery is ready for replacement
- Boston Scientific Inc.: 100 bpm; 85 bpm when battery is ready for replacement
- Manufacturer code on pulse generator is visible on Chest Xray
Electromagnetic Interference
- Nonmedical
- Cell phones: do not interact with device
- Airport security: may trigger alarm, no alteration of activity
- Medical Sources
- MRI: mostly safe, consult cards on device specific recs
- Cardioversion: Use AP pads >8cm from device to minimize adverse effects
- Unipolar Cautery - can cause sensing and pacing malfunction as well as reprogramming
Differential Diagnosis
Pacemaker Malfunction
Problems with pocket
- Infection
- Most commonly S. aureus or S. epidermidis
- 2% local wound infection; 1% sepsis/bacteremia
- Hematoma
- Typically occurs shortly after placement
Problems with leads
- Dislodgment
- Perforation (most commonly at RV apex)
- Infection can cause severe sepsis
- Tricuspid regurgitation
- Coiling (ie: Twiddler's Syndrome)
Failure to Capture
- Delivery of pacing stimulus without depolarization
- Functional - refractory myocardium, desensitized local tissue around the lead
- Medical - drugs, myocardial disease, electrolytes
- Technical - insufficient device output, lead dislodgment, fracture, insulation defect, ventricular wall perforation
- Battery of End of Life (EOL)
Failure to Pace
- Failure to deliver a stimulus to the heart
- Oversensing - most common cause: can present with symptomatic bradycardia, cause is retrograde P’s, T’s, skeletal muscle myopotentials, can be treated by placing a magnet over the pacemaker to switch to pacer mode
- Crosstalk - type of oversensing where the ventricular lead senses atrial pacing stimulus, and ventilator output inhibited
Failure to Sense
- Normal function: a sensed myocardial depolarization greater than the programmed threshold causes inhibition of pacing
- Failure to sense results in a paced beat on top of an intrinsic beat (as the device is "unaware" of the intrinsic beat")
- Voltages of patient's intrinsic QRS complex is too low to be detected
- New intrinsic arrhythmia (AF has a smaller depolarization than sinus beat), AMI, electrolyte abnormalities, lead separation, battery depletion
Runaway Pacing
- Physiologic electrical activity (T waves, muscle potentials)
- External electromagnetic interference
- Signals generated by interaction of different portions of the pacing system
- Potentially life-threatening as it can cause V-Fib or (paradoxically) bradycardia due to failure to capture
Pacemaker Mediated Tachycardia
- Also known as Endless Loop Tachycardia
- Formation of a re-entrant circuit causing inappropriate tachycardia
- 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
- Tachycardia does not exceed programmed upper limit rate on pacemaker
Evaluation
Work-Up
- BMP and Mg
- CXR
- ECG
- Troponin
- Interrogation
- Each company has on-call representatives who will come interrogate a device 24/7 (phone numbers above)
- Most cath labs will have machines capable of interrogating each brand
Expected ECG Patterns
- Absence of pacer artifact indicates intrinsic depolarization
- With newer pacemakers, pacer spikes may not appear on some or all paced beats, depending on EKG machine
- Pacing artifacts preceding depolarizations indicate successful pacing and capture
- Leads in RV apex produce LBBB pattern with appropriate discordance
- New RBBB pattern may indicate lead in LV
- Bi-ventricular devices can produce paced QRS complexes that are either narrow or wide and bizarre, depending on device programming
- Simultaneous depolarization of ventricles produces dominant R wave in V1
Plain Film Findings
- Obtain PA/Lateral Films to confirm pulse generator, manufacturer, lead placement/number/integrity
- R atrial lead J shaped(tip medially on AP) entering right atrial appendage
- RV leads point downward with tip between left spine and cardiac apex--lateral XR shows inferior and anterior
- Coronary sinus lead- courses posteriorly on lateral XR
- Extra leads may be appropriately abandoned and capped
- ICD component appears as thickened shock coil
Management
- Pacemaker Mediated Tachycardia
- Break with adenosine or magnet.[2]
- Magnet placement will stop the sensing of the retrograde-conducted P waves driving PMT; this will immediately terminate the rhythm.
- Recurrence of PMT after earlier termination means that the pacemaker settings need to be changed
- Consider chest wall stimulation techniques[3] - transcutaneous pacing, isometric muscular exercise, precordial thump
- Break with adenosine or magnet.[2]
- Electrophysiology or cardiology consult is often needed
- Contact a device representative for a full interrogation
Disposition
- Resolved Pacemaker-mediated Tachycardia without recurrence - discharge
- Infection - admission with MRSA coverage antibiotics, consult to cardiology, with likely replacement of pacemaker after 4-6 weeks of IV antibiotics
- Pacing/sensing/capture issue - likely admit
See Also
- Medical device complications
- In-Training Exam Review
- Implantable Cardioverter-Defibrillator complication
References
- ↑ Bernstein AD. et al. The revised NASPE/BPEG generic code for antibradycardia, adaptive-rate, and multisite pacing. North American Society of Pacing and Electrophysiology/British Pacing and Electrophysiology Group. Pacing Clin Electrophysiol 2002 Feb; 25(2) 260-4. lmid:11916002
- ↑ EB Medicine- Sept 2014- Managing Pacemaker-Related Complications and Malfunctions in the Emergency Department
- ↑ Barold SS, Falkoff MD, Ong LS, Heinle RA. Pacemaker endless loop tachycardia: termination by simple techniques other than magnet application. Am J Med. 1988;85(6):817-22.