The outlook for cardiac arrhythmias depends on the type of rhythm disturbance and whether the person has coronary artery disease, congestive heart failure, or some other heart muscle disorder. The prognosis for ventricular fibrillation is grave, and death follows quickly without emergency treatment. Most atrial arrhythmias have an excellent prognosis. The outlook is good for heart block, even third-degree A-V block, the most serious type. The availability of permanent pacemakers, implanted cardioversion/defibrillation devices and effective medications has improved the prognosis for many people with serious cardiac arrhythmias.