Artificial Pacemakers: Part- VIII- Pacemaker complications
Pacemaker complications are divided into –
Implant related complications, Lead related complications, & Pacemaker malfunction.
A) Implant related complications (procedure related / acute)
1) Subclavian puncture: Traumatic pneumothorax, Haemothorax, air embolism, AV fistula, Thoracic duct injury, Subacute emphysema, Brachial plexus injury.
2) Hematoma formation at pulse generator / due to anticoagulants.
3) Thrombus formation / embolism / stroke / Acute venous thrombosis (30 – 40% have partial thrombosis : Asymptomatic due to collateral development)
4) Lead perforation / cardiac tamponade, Rising stimulus threshold, RBBB morphology, Intercostal diaphragmatic pacing, Frictional rub, hypotension
5) Subclavian thrombosis/ thrombosis of SVC, RA/RV (clinically / echo)
6) SVT / VT during implantation.
B) Lead related complications:
1) Lead dislodgement- Atrial > Ventricular, a) Macrodislodgement –radiographically evident, b) Microdislodgement.
2) Lead fracture: Occurs adjacent to pacemaker / near venous site. If # of bipolar leads occurs, it may be possible to pace by reprogramming to unipolar configuration.
3) Loss of integrity of insulation: Manufacturing defects / wear & tear, Crush injury, Insulation defects with # occurs at costoclavicular space.
4) EXIT BLOCK – Abnormality at myocardial-electrode interface.
5) Tip extrasystoles- Post-implant period , not preceded by stimulus, resolve spontaneously in 24 – 48hrs,
6) Diaphragmatic or pectoral muscle pacing- dislodgement ,insulation defect, Common with unipolar leads.
C) Pacemaker infection:
Most common Staphylococcus aureus / epidermidis, Lead -vegetations, Local inflammation, fever, positive blood culture, Incidence < 2%, Needs removal of pacemaker leads & generator.
D) Pacemaker system malfunction- Troubleshooting:
ECG abnormalities- 1) Failure to capture, Pacing artefact present, No cardiac depolarization, INTERMITENT OR PERSISTENT.
2) Failure to pace / Failure to output- Failure to deliver stimulus Sensitivity, Atrial- 0.18 to 8 mV, Ventricular- 1 to 14 mV.
OVERSENSING- T,P,R waves, Myopotentials, diaphraghmatic, Electromagnetic interference, Crosstalk, Diagnosis by magnet ECG.
TREATMENT: Reduce the sensitivity, Change to bipolar sensing, Increase ventricular banking period.
DD of failure to capture & failure to pace overlap:
1) Coil # incomplete- Failure to capture (incomplete #) with low threshold that cannot stimulate, escaping current is over sensed, that leads to inhibition of output
2) Complete # - Failure to pace
3) Insulation defect- Can cause over sensing: failure to pace or failure to capture
4) End stages of battery depletion- Failure to pace / capture.
Failure to sense / UNDERSENSING:
True Undersensing, Functional Undersensing, Failure to recognize normal intrinsic activity.
1) True abnormalities- Lead dislodgement, circuit failure, electromagnetic interference, battery depletion, insulating defects.
2) Functional Undersensing- activity occurs during refractory period.
Fusion / pseudo fusion beats, Hybrid beat
Local inflammation, Ischemia / Infarction, Electrolyte abnormalities, Drugs, Post cardioversion.
Pacemaker syndrome: Constellation of neurological & cardiovascular signs & symptoms.
Symptoms: Neck pulsations, Fatigue / apprehension, Palpitations, Cough / choking, Orthopnea, Dyspnoea, Dizziness / syncope, Confusion / altered mental state.
Signs: Cannon A waves, raised JVP, Liver pulsations, Peripheral oedema, S3, Pulmonary rales, decrease in SBP > 20.
Causes of pacemaker syndrome (5-7%): Loss of AV synchrony, Cardiovascular / humoral reflexes due to increased pulmonary venous & RA pressures, Ventriculoatrial conduction, Vasodepressor reflex induced- by cannon A wave carotid body- DDD, Lower VVI rate & using hysteresis mode VDD.
Hysteresis: Extension of escape / interval after sensed beat.
Pacemaker mediated tachycardia OR Endless loop tachycardia: a) Seen in atria sensed / ventricular pacing system, b) In patients with intact ventriculoatrial conduction- retrograde conduction to atria - if outside PVARP- c) can be prevented by increased PVARP.
Runaway Pacemaker: Circuit malfunction- erratic tachycardia, Due to radiation / cautery.
Twiddlers syndrome: Patient intentionally / unintentionally manipulates pulse generator Causing twisting in pacemaker system.
MRI, Cautery, DC shock, Radiofrequency ablation, Diathermy, Lithotripsy, Radiation therapy, Cellular phones, Metal detectors, High voltage power lines, Arc welding, Transformers, Electronic surveillance devices.