Sustained VT

VT is considered sustained if it is continuous for at least 30 seconds. If the QRS complex has primarily a single morphology, the VT is monomorphic, whereas if the QRS complex varies, the VT is polymorphic .

Polymorphic VT is defined as an unstable rhythm with a continuously varying QRS complex morphology in any recorded ECG lead. Polymorphic VT that occurs in the setting of QT prolongation is considered as a distinct arrhythmia, known as torsades de pointes .

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare condition. It causes an irregular heart rhythm that can be life threatening . It often shows up in childhood, but can show up later in life. The first sign is often fainting or near fainting during exercise or strong emotion.

Polymorphic VT in patients with a normal QT interval is treated in the same manner as monomorphic VT. If the patient has runs of polymorphic VT punctuated by sinus rhythm with QT prolongation, treatment is with magnesium sulfate, isoproterenol, pacing, or a combination thereof .

Polymorphic VT generally indicates the presence of significant heart disease due to acute myocardial ischemia, cardiomyopathies, or a genetic arrhythmia syndrome (see what follows). Drugs causing QT prolongation and metabolic derangements are other causes (Fig.

Collapse Section. Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a condition characterized by an abnormal heart rhythm (arrhythmia) . As the heart rate increases in response to physical activity or emotional stress, it can trigger an abnormally fast heartbeat called ventricular tachycardia.