Ventricular Tachycardia

Ventricular tachycardia (VT) is a heart rhythm disorder that develops because of abnormal electrical signals of the ventricles, which is the lower chamber of the heart. In a normal scenario, the heart beats around 60 to 100 times a minute which are defined by the signals originating in the atria; the upper chamber of the heart. However, among individuals with this condition, the abnormality causes the heart to beat much faster than normal and out of synch with the upper chambers. Therefore, the heart is not able to pump sufficient amount of blood to the body and the lungs as the upper and lower chambers of the heart are not in synch with each other. If the condition only lasts for a few seconds it may not cause any symptoms, but if it persists, the symptoms may become evident. In the absence of structural heart disease, this condition is termed as idiopathic ventricular tachycardia. And, it has accordingly been classified based on the ventricle of origin, response to pharmacologic agents and its morphologic features. In most cases, individuals with ventricular tachycardia often have other health conditions such as coronary artery disease, heart valve disease, high blood pressure or an enlarged heart. In some cases, the non-heart related reasons for ventricular tachycardia may include an imbalance in electrolytes, certain medications, excess alcohol and genetically transmitted conditions.

In rare cases, individuals who already have other heart conditions such as a previous heart attack, the ventricular tachycardia could cause a life-threatening problem such as the sudden cardiac arrest. The management and the prognosis of VT can differ greatly based on the individual’s clinical status, the classification of VT and if they already have another heart disease. Individuals with idiopathic ventricular arrhythmia appear to have a better prognosis than those with structural heart disease and ventricular tachycardia.

Classification of Ventricular Tachycardia

Generally, patients with VT often experience structural heart disease but those who don’t have any structural heart abnormalities fall into these various categories;

  • Right Ventricular outflow tract tachycardia (RVOT)

This is one of the common forms of the outflow tract tachycardia which is normally benign and not considered to be life-threatening. However, the affected individual may experience recurrent palpitations, dizziness and very uncommonly loss of consciousness. It seems to be triggered by anxiety or excitement and also with the use of caffeine. Among pre-menopausal women, hormone appears to play a significant part in triggering this condition. The treatment begins with a reassurance that it’s a benign condition and to avoid stimulants such as caffeine. The beta-blockers appear to be more effective than the calcium channel blocker therapy. 

  • Left ventricular outflow tract tachycardia (LVOT)

This is an uncommon idiopathic left ventricular tachycardia. This form of tachycardia has a different ECG appearance from the RVOT but some left outflow tract tachycardias present more subtle differences. This condition could be resolved with the use of calcium blockers or beta-blockers. Also, with the advanced technologies like the intracardiac echocardiography, three-dimensional non-contact mapping and magnetic electroanatomic mapping could all be used for the mapping and ablation of LVOT-VT. However, ablation of LVOT-VT may not always be successful and free of complications. 

  • Ventricular tachycardia and cardiomyopathy

VT in the setting of cardiomyopathy appears to be the common forms of ventricular tachycardia. The myocardial infarction could present a central area of scar enveloped by small sections of scar interspersed with living tissue and these channels of living tissue appear to be the pathway for electrical signals to travel. And most VT in the setting of cardiomyopathy appears to take a circular path again and again. So, for individuals with cardiomyopathy and ventricular tachycardia, they could be treated with an implantable defibrillator because of the increased risk of sudden cardiac death and those with multiple VT shocks could have ventricular tachycardia ablation. 

  • Ventricular tachycardia and sudden cardiac death in hypertrophic cardiomyopathy

One of the major causes of death among individuals with hypertrophic cardiomyopathy is the life-threatening arrhythmias although not all cases are susceptible to it. However, in order to determine the increased risk of these serious ventricular arrhythmias, a complete family history, a number of tests such as 24 hours ECG monitoring, history of prior cardiac arrest will be evaluated by the physician and based on the criteria, the option of an implantable cardioverter defibrillator may be discussed. 

Investigations used for Ventricular Tachycardia

  • Echocardiography is the important investigation used for VT. Among individuals with VT related to coronary artery disease, the site of previous infarction and the extent of LV dysfunction are important. Dilated cardiomyopathy and left ventricle dysfunction among those with longstanding hypertension and diabetes are also considered important causes of VT.
  • MRI scan including the contrast-enhanced imaging is used to study the structural cardiac abnormalities.
  • Electrophysiological test is used to confirm the diagnosis and to locate the site of the problem. During this test, catheters are inserted either in the groin or the neck that guides them through the blood vessels to different spots of the heart.

Long-Term Management of Individuals with Ventricular Tachycardia

  • VT can be suppressed with beta-blockers and calcium channel blockers
  • d-Sotalol can be used for individuals with VT who either have structural heart disease or without it as long as the LV function is not compromised.
  • Amiodarone exerts its anti-arrhythmic action; however, the long term therapy is associated with high discontinuation rate due to pulmonary, hepatic and thyroid-related side-effects.
  • Implantable cardioverter defibrillator may be recommended among individuals at risk of having a life-threatening VT episode. This device detects and delivers calibrated electrical shocks when required to restore the normal heart rhythm.
  • Catheter ablation is used when an abnormal electrical pathway is responsible for increasing the heart rate. This procedure uses the catheters which are guided through the blood vessels and to the heart. The electrodes at the catheter tips uses either heat, extreme cold or radiofrequency energy to ablate the extra electrical pathway.
  • Cardiac surgery may be necessary in some cases when other treatment options don’t work effectively to control the condition.

References

https://stanfordhealthcare.org/medical-conditions/blood-heart-circulation/ventricular-tachycardia/types.html

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3539396/

http://medind.nic.in/gaa/t10/i2/gaat10i2p36.pdf

https://www.mayoclinic.org/diseases-conditions/ventricular-tachycardia/diagnosis-treatment/drc-20355144

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4295736/