For some patients, preventing SCA means controlling or stopping the abnormal heart rhythms that may trigger ventricular fibrillation. Treating arrhythmias is done in three ways:

• Medications — Medications, including ACE inhibitors, beta blockers, calcium channel blockers and other antiarrhythmic drugs, can control abnormal heart rhythms or treat other conditions that may contribute to heart disease or SCA. But taking medication alone has not proved to be very effective in reducing SCA. These medications are sometimes taken by patients in conjunction with having an implantable defibrillator (ICD), in order to reduce the frequency of the ICD needing to treat an arrhythmia with a shock.
• Implantable cardioverter defibrillators (ICDs) — These devices have been very successful in preventing SCA in certain high-risk patients, particularly those with a weakened heart muscle (low ejection fraction). Like a pacemaker, an ICD is implanted under the skin. Wires called leads run from the ICD to the heart, and the device monitors the heart to detect any abnormal rhythms. If a dangerous arrhythmia is detected, the ICD delivers an electrical shock to restore the heart’s normal rhythm and prevent sudden cardiac death. The ICD can also act like a pacemaker if the heart is beating too slowly.
• Catheter Ablation — In this technique, radiofrequency energy (heat), cryotherapy (freezing), or other energy forms are used to destroy small areas of heart muscle that give rise to the abnormal electrical signals causing rapid or irregular heart rhythms. The energy is delivered through catheters that are snaked through the veins or arteries to the heart. Catheter ablation is sometimes done in patients who have an ICD to decrease the frequency of abnormal heart rhythms, and again, to reduce how often the device is required to shock a dangerous arrhythmia.