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Ventricular Fibrillation Information - cause, symptom, treatment of Ventricular Fibrillation
Sudden cardiac death is defined as unexpected nontraumatic death in clinically well or stable patients who die within 1 hour after onset of symptoms. The causative rhythm in most cases is ventricular fibrillation, which is usually preceded by ventricular tachycardia except in the setting of acute ischemia or infarction. Complete heart block and sinus node arrest may also cause sudden death. A disproportionate number of sudden deaths occur in the early morning hours. Over 75% of victims of sudden cardiac death have severe coronary artery disease. Many have old infarctions. Sudden death may be the initial manifestation of coronary disease in up to 20% of patients and accounts for approximately 50% of deaths from coronary disease. When ventricular fibrillation occurs in the initial 24 hours after infarction, long-term management is no different from that of other patients with acute infarction. Other conditions that predispose to sudden death include severe left ventricular hypertrophy, hypertrophic cardiomyopathy, congestive cardiomyopathy, aortic stenosis, pulmonary stenosis, primary pulmonary hypertension, cyanotic congenital heart disease, atrial myxoma, mitral valve prolapse, hypoxia, electrolyte abnormalities, prolonged QT interval syndrome, and conduction system disease. Late potentials (after the QRS complex) on a signal-averaged surface ECG in patients with prior myocardial infarction may identify a group of patients at risk of ventricular arrhythmias and sudden death.
Ventricular Fibrillation Information
Unless ventricular fibrillation occurred shortly after myocardial infarction, is associated with ischemia, or is seen with an unusual correctable process (such as an electrolyte abnormality, drug toxicity, or aortic stenosis), surviving patients require evaluation and intervention since recurrences are frequent. Exercise testing or coronary arteriography should be performed to exclude coronary disease as the underlying cause, since revascularization may prevent recurrence. Conduction disturbances should be managed as described in the next section. If prodromal supraventricular arrhythmias or ventricular arrhythmias, such as sustained or nonsustained ventricular tachycardia, are found by ambulatory electrocardiographic monitoring, their elimination by pharmacologic therapy or ablation may prevent further episodes. There is growing consensus that if myocardial infarction or ischemia, other precipitating causes of ventricular fibrillation, or bradyarrhythmias and conduction disturbances are not found to be the cause of the sudden death episode, an implantable defibrillator is the treatment of choice for appropriate patients. In addition, there is evidence from the MADIT II study and other reports that in a patient with a prior myocardial infarction and severe left ventricular dysfunction, prophylactic implantation of a defibrillator reduces the risk of death—though the cost of doing so in all such patients would be very high.
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