Polymorphic Ventricular Tachycardia: Causes, Symptoms and Treatment

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What is Polymorphic Ventricular Tachycardia?

Polymorphic ventricular tachycardia is an abnormally fast heart rhythm starting in the ventricles, the lower chambers of the heart. A normal heart rate for an adult is 60-100 beats per minute. In v-tach, as it’s commonly called, the heart rate can be 170 beats per minute or even faster. V-tach can either be monomorphic or polymorphic. In monomorphic v-tach, the EKG tracing is consistent and follows the same pattern. With polymorphic v-tach, the EKG pattern is more irregular due to the origins of the signal conduction in the ventricles.

Causes

Polymorphic v-tach can be caused by a heart attack. Coronary artery disease is the most common cause of all ventricular tachycardias. V-tach is also found in patients with heart failure, myocarditis, electrolyte imbalances and sleep apnea. The most common electrolyte imbalances that can cause v-tach are low potassium and low magnesium. These two electrolytes are essential for the proper conduction of the heart’s electrical signals. Drugs which block potassium channels, such as quinine, Haldol and erythromycin can also cause rhythm disturbances.

Symptoms

V-tach causes the rapidly beating ventricles to not fill properly with blood between beats. This causes too little blood to be pumped, which in turn causes too little oxygen to be delivered to the tissues. Blood pressure drops, causing dizziness and lightheadedness. Patients may also experience chest pain, shortness of breath or palpitations. Prolonged v-tach can cause loss of consciousness, cardiac arrest and death.

Treatment

If v-tach leads to cardiac arrest, emergent treatment utilizing ACLS protocols is needed to prevent death. Often treatment requires a combination of CPR, defibrillation (“shocking” the heart with electrical current) and use of IV drugs to correct arrhythmias. These drugs often include amiodarone, sotalol or procainamide.

If v-tach has not become emergent, treatment options include having an implantable cardiac defibrillator (ICD) placed, or undergoing radiofrequency catheter ablation (RCA). With an ICD, the cardiologist inserts a device about the size of a pager in a pocket under the skin of the left upper chest wall. Wires run from the ICD through the veins to the heart. When the ICD detects an abnormal heartbeat, an electrical impulse travels down the wires to the heart and restores the normal heart rhythm. The procedure is usually done under light sedation and requires only an overnight stay in the hospital.

With RCA, a cardiac electrophysiologist determines the area in the heart where the abnormal rhythm originates. A catheter with a specialized high-frequency electrical current tip is placed on the area of the ventricle responsible for the abnormal rhythm. This destroys a very small area of tissue, which renders it unable to function. RCA may be used alone or with an ICD to fully control the abnormal rhythm.

References

Texas Arrhythmia Institute: https://www.txai.org/edu/irregular/ventricular_tachyarrhythmias.htm

Medline Plus: https://www.nlm.nih.gov/medlineplus/ency/article/000187.htm

Cleveland Clinic: https://my.clevelandclinic.org/documents/heart/guides/ventricular-tachycardia-guide.pdf