The morphology of the<unk> ycardia depends on its cause and the origin of the re-entry electrical circuit in the heart. In monomorphic<unk> , the shape of each heart beat on the ECG looks the same because the impulse is either being generated from increased automaticity of a single point in either the left or the right ventricle, or due to a reentry circuit within the ventricle. The most common cause of monomorphic<unk>  is scarring of the heart muscle from a previous myocardial infarction (heart attack). This scar cannot conduct electrical activity, so there is a potential circuit around the scar that results in the<unk> ycardia. This is similar to the re-entrant circuits that are the cause of atrial flutter and the re-entrant forms of supraventricular<unk> ycardia. Other rarer congenital causes of monomorphic<unk>  include right ventricular dysplasia, and right and left ventricular outflow tract<unk> . Polymorphic<unk> , on the other hand, is most commonly caused by abnormalities of ventricular muscle repolarization. The predisposition to this problem usually manifests on the ECG as a prolongation of the QT interval. QT prolongation may be congenital or acquired. Congenital problems include long QT syndrome and catecholaminergic polymorphic<unk> . Acquired problems are usually related to drug toxicity or electrolyte abnormalities, but can occur as a result of myocardial ischemia. Class III anti-arrhythmic drugs such as sotalol and amiodarone prolong the QT interval and may in some circumstances be pro-arrhythmic. Other relatively common drugs including some antibiotics and antihistamines may also be a danger, in particular in combination with one another. Problems with blood levels of potassium, magnesium and calcium may also contribute. High-dose magnesium is often used as an antidote in cardiac arrest protocols.
Ventricular tachycardia
Artificial cardiac pacemaker
Sinus arrhythmia
Electrocardiography
Junctional tachycardia
Supraventricular tachycardia
Torsades de pointes
Tachycardia