What is DCCV (Direct Current Cardioversion) in cardiology?

Direct Current Cardioversion (DCCV) in Cardiology

DCCV (Direct Current Cardioversion) is a medical procedure that delivers a synchronized electrical shock to the heart to restore normal sinus rhythm in patients with cardiac arrhythmias, particularly atrial fibrillation and atrial flutter. 1

Definition and Technical Aspects

DCCV involves:

• Delivery of an electrical shock synchronized with the R wave of the ECG
• Synchronization ensures the shock does not occur during the vulnerable phase of the cardiac cycle
• Distinguished from defibrillation, which uses asynchronous electrical discharge (used for ventricular fibrillation)
• Can be performed externally (transthoracic) or internally (endocardial) 1

External Cardioversion

• Performed with the patient in a fasting state under sedation or general anesthesia
• Electrodes (paddles or pads) placed in anteroposterior or base-apex position
• For atrial fibrillation, a more superoanterior left paddle position is often more effective
• Shock synchronized to the peak of the QRS complex
• Initial energy levels vary by arrhythmia type, but generally 200J or greater is recommended for atrial fibrillation with biphasic waveform defibrillators 1

Internal Cardioversion

• Used when external cardioversion fails
• Performed under conscious sedation or general anesthesia
• Specialized electrode catheters with large surface areas placed in the right atrium and coronary sinus
• Up to 10J of energy can be safely delivered between right atrium and coronary sinus
• Requires temporary anticoagulation with heparin if warfarin is withheld 1

Clinical Indications

DCCV is recommended in the following scenarios:

• Patients with AF with ongoing myocardial ischemia, symptomatic hypotension, angina, or heart failure when rapid ventricular response doesn't respond to medications
• Patients with AF involving preexcitation with very rapid tachycardia or hemodynamic instability
• Patients without hemodynamic instability when AF symptoms are unacceptable
• As part of a long-term management strategy for patients with AF 1

Contraindications

• Frequent repetition of DCCV for patients with short periods of sinus rhythm between AF relapses despite antiarrhythmic therapy
• Patients with digitalis toxicity or hypokalemia 1

Precautions and Preparation

• Appropriate anticoagulation before and after the procedure for AF patients
• Transesophageal echocardiography may be used to identify atrial thrombi before cardioversion
• Adequate sedation and monitoring throughout the procedure
• Availability of emergency equipment to manage potential complications 1

Potential Complications

• Induction of ventricular tachycardia/fibrillation
• Asystole
• Transient depression of myocardial function, particularly with repeated shocks and higher energies
• Thromboembolic events if anticoagulation is inadequate 1

Efficacy

• Initial success rates for cardioversion are generally high
• Long-term maintenance of sinus rhythm is more challenging
• Antiarrhythmic medications may be used to maintain sinus rhythm after successful cardioversion
• Recurrence rates remain significant despite therapy 2, 3

Technical Considerations

• Biphasic waveform defibrillators have lower defibrillation thresholds compared to monophasic devices
• Higher initial energy may be more effective and result in fewer total shocks 4
• Electrolyte-impregnated pads minimize electrical resistance between electrode and skin
• Shocks delivered during expiration or chest compression deliver higher energy to the heart 1

DCCV remains an important tool in the management of cardiac arrhythmias, particularly for rapid restoration of sinus rhythm in symptomatic patients or those with hemodynamic compromise.