Arrhythmias can cause disruption of the heart's conduction system. Premature complexes are usually asymptomatic but can cause palpitations, which may be helped by beta-blockers. They can also be a sign of hypoxia. Tachyarrhythmias involve multiple irregular foci in the atria leading to an irregular ventricular rate without P waves. Causes include heart disease, excess alcohol, and treatment involves stabilization and anticoagulation to prevent strokes. Atrial fibrillation is associated with heart failure, COPD, and ASD and requires at least 3 different P wave morphologies for diagnosis. Ventricular tachycardia is commonly caused by prior heart attacks and classified as sustained if lasting over 30 seconds and