Monomorphic Ventricular Tachycardia
Symptoms associated with MVT include:
- Palpitations, often described as pounding, racing, or fluttering
- Chest pain or tightness
- Dyspnea
- Presyncope or syncope
- Cardiac arrest
Signs on exam:
- achycardia with narrow QRS complex on ECG (rate usually 140-250 bpm)
- Hemodynamic instability – hypotension, acute heart failure
Associated risk factors and conditions:
- Structural heart disease – prior myocardial infarction, cardiomyopathy
- Electrolyte abnormalities – hypokalemia, hypomagnesemia
- Drugs that prolong QT interval
- Congenital syndromes – long QT syndrome, Brugada syndrome
- Men are more commonly affected than women
- Mean age of presentation is 65 years old
MVT can present across a spectrum from asymptomatic ectopy to unstable rhythms causing syncope, chest pain, shortness of breath, hypotension, or sudden cardiac death. It is crucial to obtain a 12-lead ECG, which will demonstrate a regular, monomorphic wide complex tachycardia. Hemodynamic instability warrants urgent electrical cardioversion.
Polymorphic Ventricular Tachycardia
- Symptoms associated with polymorphic VT include palpitations, lightheadedness, syncope, and chest pain. Hemodynamic instability with hypotension, altered mental status, and shock can occur.
- Polymorphic VT often presents with a rapid ventricular rate between 150-250 beats per minute.
- The ECG shows a irregular, continuously changing QRS morphology and axis – the complexes appear to twist around the isoelectric line.
- Prolongation of the QT interval is usually seen prior to initiation of polymorphic VT episodes.
- Risk factors include structural heart disease, electrolyte disturbances (hypokalemia, hypomagnesemia), drugs that prolong QT interval, bradycardia, pauses, congenital long QT syndromes.
- More common in older adults but can occur at any age. Slight male predominance.
- Sudden cardiac death can be the initial presentation in patients with undiagnosed congenital channelopathies.
- Syncope, cardiac arrest, or sudden death can occur if polymorphic VT deteriorates into ventricular fibrillation.
