A defibrillator (automatic implantable cardiac defibrillator, or AICD) is
actually a pacemaker with additional capability to monitor and treat harmful arrhythmias. Patients may be at risk
of ventricular tachycardia (VT) or ventricular fibrillation (VF) due to prior heart attack, cardiomyopathy, medications, genetic abnormalities, electrolyte abnormalities, or a combination
of these problems. VT and VF are life-threatening arrythmias of the heart, where the electrical signals rapidly circle the
ventricle chamber of the heart. The heart beats too fast and blood cannot be efficiently pumped to the body. An
electrical shock is needed to reset the electrical timing mechanism of the heart.
Symptoms of VT or VF include syncope, chest pain, or sudden death. Sometimes these heart arrhythmias occur
causing patients to pass out, but then the heart recovers and normal rhythm is restored, avoiding death. Some
patients may tolerate VT surprisingly well, with only symptoms of lightheadedness, palpitations or chest discomfort.
This will depend on the speed of the heart rhythm and the overall strength of the heart. Patients with prior heart attack
and low ejection fraction (<30%) are at risk of VT or VF, and therefore at risk of dying suddenly A large national
study has demonstrated that such patients live longer if an AICD is placed, compared to patients treated with medications
alone. An AICD is placed similar to a pacemaker, and may need to be changed every few years due to depletion of the
battery. We check these devices in the clinic every 3-6 months to optimize battery life and safety.
