Cardioversion and Atrial Fibrillation

Countershock/Cardioversion

• Cardioversion is used to convert dysrhythmias using electrical current
• Examples of dysrhythmias that require cardioversion: Atrial Fibrillation, SVT, and others
• In cardioversion, the dysrhythmia must have an R wave or QS wave
• The machine must be able to recognize and "sync" with the R/QS wave
• Symptoms that the patient may experience includes hypotension, dyspnea and chest pain

Atrial Fibrillation Treatment

• If the duration of atrial fibrillation is less than 48 hours, treatment involves digitalis, calcium channel blockers, beta-blockers, amiodarone, or cardioversion
• If the duration is more than 48 hours, non-emergent treatment is anticoagulation for 2-3 weeks followed by cardioversion
• In emergencies, treatment includes heparin, transesophageal echocardiogram to rule out atrial clots, followed by cardioversion

Protocols

• Protocols for cardioversion include procedural sedation using hypnotic sedatives and narcotic analgesics like Etomidate and Fentanyl
• Defibrillator pads placement should be anterior-posterior for best results with Afib
• The "sync" button on the defibrillator is pressed
• Biphasic current uses an initial dose of 100-120 joules, which may be repeated with 200 joules

Nursing Considerations

• Informed consent is required
• The resuscitation team present should be MD, RN, RT, RPh
• The nurse makes sure the resuscitation team has all necessary medications
• The patient must have patent IV access
• ECG strips are documented before and after the procedure
• Oxygen and metal are removed from the patient
• See care plan that is provided

Countershock/Defibrillation

• A countershock uses an unsynchronized electrical shock that administers a larger number of joules than cardioversion
• Countershocks are unsynchronized because there is no discernible "R" wave to sync the machine with
• Ventricular fibrillation and ventricular tachycardia where the patient is pulseless are examples of when to use countershocks

Pacemakers

• Pacemakers use a pulse generator to provide an electrical stimulus to the heart
• They are used when myocardial conduction cannot maintain adequate cardiac output
• The pulse generator is connected to wires that carry electrical stimulus to the myocardial cells
• Pacemakers are used in addition to drug therapy
• The pacing mechanism may be temporary or permanent

Types of Pacing

• Pacing is programmed to pace different areas of the heart
• The most common pacemakers are designed to pace ventricles
• Pacing produces a spike before the QRS complex
• Pacemakers can be used when transmission of atrial impulses is blocked
• They can be programmed to pace when an intrinsic beat is not sensed
• Pacemakers initiate an impulse on sensing electrical activity

ICD

• ICDs are indicated to prevent sudden cardiac death in conditions such as VF arrest, sustained VT and cardiomyopathy
• Therapies delivered by ICDs can include defibrillation to shock ventricular fibrillation and cardioversion, if necessary
• ICDs also provide pacing such as anti-tachycardia pacing (to avoid cardioversion if possible) and bradycardia pacing

Hypothermia Therapy

• Hypothermia therapy involves cooling a post cardiac arrest victim to 90-93 degrees Farenheit
• Hypothermia slows body metabolism and protects the brain

Hypothermia Therapy-Cool Down

• Atrial and ventricular dysrhythmias are common due to PR, QRS and QT prolongation with hypothermia therapy
• Sinus tachycardia occurs at the initiation of therapy, which slows to sinus bradycardia as therapy progresses
• Hypokalemia is a common result of using IV supplement therapy

Hypothermia: Rewarming

• Rewarming occurs after approximately 12-24 hours of therapy after hypothermia therapy
• Hyperkalemia may result as electrolytes shift, creating pointy T waves and widened QRS complexes
• Rewarming too rapidly can cause vasodilatation, hypotension and rapid electrolyte shifts
• Follow CVP, ScVO2, and UO closely