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14. Defibrillator Malfunction: It’s Electric! Boogie, Woogie, Woogie!
Keywords
AICD discharges resultMalignant ventricular arrhythmiaVT or VFStructural heart diseaseCardiomyopathyMalignant ventricular dysrhythmiaCase
Pertinent History
This patient is a 73-year-old male who presented to the ED approximately 3 hours after a perceived firing of his AICD. He states he was walking to the bathroom when he developed palpitations. He had no chest pain, dyspnea, lightheadedness, or other symptoms. Several seconds later, he felt as though he was “kicked in the chest by a mule.” Subsequently, the palpitations he experienced resolved. His only symptom after the event is mild chest discomfort, which is slowly resolving. Patient reports that he forgot to take his metoprolol this morning.
Past Medical History
Hypertension, Type II Diabetes, Coronary Artery Disease, and remote STEMI resulting in ischemic cardiomyopathy with EF 20%.
Medications
Metoprolol, Lisinopril, Lasix, Metformin, Atorvastatin.
Social History
Forty pack-year smoking history, no drug or alcohol use.
Pertinent Physical Exam
BP 142/90, Pulse 102, Temp 98.1 °F (36.7 °C), RR 14, SpO2 96%.
Cardiovascular:
Borderline tachycardia, regular rhythm, no gallop, friction rub or murmur heard.
Chest Wall:
Left upper chest AICD device without overlying erythema or tenderness to palpation of site.
Lung:
Clear to auscultation bilaterally.
Except as noted above, the findings of a complete physical exam are within normal limits.
Pertinent Test Results
EKG
Laboratory Analysis
Test | Result | Units | Normal Range |
|---|---|---|---|
WBC | 4.55 | K/uL | 3.8–11.0 103/mm3 |
Hgb | 14.8 | g/dL | (Male) 14–18 g/dL (Female) 11–16 g/dL |
Platelets | 222 | K/uL | 140–450 K /uL |
Sodium | 136 | mEq/L | 135–148 mEq/L |
Potassium | 2.9 ↓ | mEq/L | 3.5–5.5 mEq/L |
Chloride | 106 | mEq/L | 96–112 mEq/L |
Bicarbonate | 25 | mEq/L | 21–34 mEq/L |
BUN | 13 | mg/dL | 6–23 mg/dL |
Creatinine | 1.01 | mg/dL | 0.6–1.5 mg/dL |
Glucose | 177 ↑ | mg/dL | 65–99 mg/dL |
Magnesium | 1.4 ↓ | mg/dL | 1.6–2.6 mg/dL |
Troponin | <0.13 ↑ | ng/dl | <0.11 ng/dl |
BNP | 350 ↑ (baseline for this patient is 350) | pg/ml | <100 pg/ml |
CXR
Single chamber AICD in place without evidence of lead fracture or displacement, no other acute cardiopulmonary process.
Device Interrogation
Single episode of irregular wide complex tachycardia with rate approximately 177 bpm, successfully aborted by AICD discharge. No other events on device interrogation.
Updates on ED Course
Update 1: The patient’s nurse informs you that the patient had four additional AICD firings in the last 10 minutes. You review the cardiac monitor alarms, revealing four episodes of irregular wide complex tachycardia successfully aborted by AICD discharge. You suspect new-onset atrial fibrillation with rapid ventricular response. You place a magnet over the AICD and ask the nurse to notify you if the patient’s heart rate increases. Potassium and magnesium were also supplemented.
Update 2: Five minutes later, the nurse notifies you that the patient has had a rhythm change with a heart rate of 175. You enter the room and ask for a 12-lead ECG, which shows recurrence of the irregular wide complex tachycardia. The patient has a BP of 120/70. You administer 15 mg of diltiazem and begin an infusion. The patient’s heart rate improves to 130 and BP increases to 120/68.
Update 3: Cardiology was consulted and reviewed the device interrogation report. The consultant believes that this event represents new-onset atrial fibrillation with rapid ventricular response and the shock was inappropriate. She recommends correction of electrolytes, rate control, anticoagulation, and admission for further monitoring and trending of cardiac enzymes. During the admission, the AICD will be adjusted. No recommendation for addition of an antiarrhythmic medication was made at this time. Admission orders were placed and the patient admitted to a monitored unit.
Learning Points: AICD Firing
Priming Questions
1. How can one distinguish between an appropriate and inappropriate AICD discharge?
2. What are the types of inappropriate AICD discharges and how are they treated?
3. Which patients with AICD discharge can be safely discharged home and which require admission?
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