Cardiac Conduction Defects
6.6
Cardiac Conduction Defects
Long QT Syndrome
- Etiology/Risk Factors
- Congenital
- Acquired
- Patients may have underlying pathology
- Drug induced is the most common cause of acquired long QT syndrome [32, 33]
- Antibiotics
- Macrolides
- Fluoroquinolones
- Antifungals
- Antidysrhythmics
- Antidepressants
- Antihistamines [34]
- Methadone [35, 36]
- Electrolyte disturbance
- Coronary artery disease
- Bradydysrhythmias
- Advanced age
- Pathophysiology
- Typical mechanism is interaction with potassium channels on myocardium
- Prolonged QT interval (Figure 6.14)
- Athletes may be initially diagnosed based on pre‐sports participation screening
- Treatment
- Treat underlying cause
- Discontinue precipitating medication
- β‐blockers
- Implantable cardioverter‐defibrillator (ICD)
- Primary Concerns
- Anesthetic medications and adjuncts increasing QT interval
- ↑ Risk of torsades de pointes
- Evaluation
- Consider cardiology consultation
- History
- Episodes of syncope
- Family history of sudden cardiac death
- Anesthesia Management [37]
- Consider delay of elective procedure if underlying cause is treatable
- Magnesium readily available
- Continue β‐blocker
- Avoid significant increases in HR
- Considered safe:
- Propofol
- Midazolam
- Fentanyl [38]
- Sevoflurane [39]
- Isoflurane [40]
- Phenylephrine [41]
- Vecuronium
- Consider avoiding as elongates QT interval
- Ondansetron [42]
- Pancuronium [43]
- Anticholinergics [44]
- Cholinesterase inhibitors [45]
- Can use in conjunction with anticholinergics
- Haloperidol [46]
- Droperidol
- Antihistamines [34]
- Albuterol [47]
- Ephedrine
- Epinephrine [41]
- Norepinephrine
- Macrolide antibiotics
- ICD management covered on page 175.
Figure 6.14
Wolff–Parkinson–White Syndrome
- Pathophysiology
- Accessory conduction pathway which connects atria to ventricles, bypassing AV node (Figure 6.15)
- Wolff–Parkinson–White pattern
- Preexcitation (delta wave) on ECG without symptomatic arrhythmias
- Wolff–Parkinson–White syndrome
- Both preexcitation (delta wave) on ECG and symptomatic arrhythmias
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