Rhythm Control – Cardioversion
Rhythm control is an attempt to restore and maintain sinus rhythm (The normal regular rhythm of the heart set by the SAN). There two ways of converting to normal rhythm:-
1. Electrical cardioversion
· External cardioversion
The patient is anaesthetized and sedated.
Electrical makes use of a defibrillator. It involves delivering electrical shock to the heart through pads (electrodes) placed on the chest and the back. The shock causes electrical impulse causes all the cardiac cells to contract simultaneously, thereby interrupting the abnormal electrical rhythm. The heart’s electrical system then regains control and restores the normal rhythm. Once the heart has been converted, medication is given to keep the normal rhythm (anti-rhythmic medication).
· Internal cardioversion
It uses a device called an implantable cardioverter defibrillator (ICD). ICDs have two parts: a pulse generator and electrodes (wires). The generator is implanted under the skin, like a pacemaker and an electric shock is delivered to the heart through the electrodes. (used for people who are at high risk of sudden cardiac death)
2. Chemical/pharmacological cardioversion
It involves giving a medication either tin pill form or intraveanously to try to convert the heart rhythm back to normal.

Examples of drugs

Sodium channel blockers (Quinidine), which improve the heart's rhythm by slowing the heart's electrical conduction.

Potassium channel blockers (Amiodarone), which relax the heart muscle and slow the electrical signals that cause atrial fibrillation.

RATE CONTROL
Rate control is to leave patients in AF while minimizing their symptoms and preventing deterioration of ventricular function by controlling the ventricular response rate. (try to bring the rate to less than 100 beats per minute).
Common drugs used are beta blockers, calcium channel blockers, and digoxin (Lanoxin).
Beta blockers and calcium channel blockers (diltiazem and verapami) are the drugs of choice because they provide rapid rate control. These drugs are effective in reducing the heart rate at rest and during exercise in patients with atrial fibrillation.
Beta adrenoceptors are inhibitory except in the heart where they are excitatory. Beta blockers for e.g. propranolol acts as an antagonist on the beta 1 adrenoceptors in the heart decreasing cardiac excitability (pacemaker activity) and decrease susceptibility to disturbances to cardiac rhythm.