Artificial Pacemakers: Part- VIII- Pacemaker complications

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.

ELECTROMAGNETIC INTERFERENCE:

MRI, Cautery, DC shock, Radiofrequency ablation, Diathermy, Lithotripsy, Radiation therapy, Cellular phones, Metal detectors, High voltage power lines, Arc welding, Transformers, Electronic surveillance devices.