Ventricular tachycardia is a type of arrhythmia that is defined by a faster than a normal heartbeat that arises when there is improper electrical activity in the ventricles of the heart. A few seconds of this rapid heartbeat may not cause any problems but longer periods or episodes of the arrhythmia can be dangerous.
Causes of Ventricular Tachycardia
Aside from the malfunction in the electrical system of the heart, ventricular tachycardia can also be caused by underlying cardiac disorders that produce damage to the ventricular muscle, usually heart failure or coronary artery disease. The cardiac muscle gets scarred or weakens with the presence of other heart conditions and this weakening or scarring of the cardiac muscle tends to create tiny electrical circuits within the heart muscle.
These electrical circuits can cause reentrant tachycardias.
Ventricular tachycardia can also occur in young and completely healthy individuals who don’t have heart failure or coronary artery disease but this is a rare occurrence. These arrhythmias are frequently caused by genetic problems or congenital problems such as:
- Brugada syndrome
- Long QT syndrome
- Short QT syndrome
- Arrhythmogenic right ventricular cardiomyopathy or ARVC
- Repetitive monomorphic ventricular tachycardia or RMVT
- Catecholamine-sensitive polymorphic ventricular tachycardia or CPVT
Inherited Cardiac Arrhythmia
Sudden cardiac deaths are frequently caused by hereditary heart conditions that are usually a primary structural heart disorder that is linked to arrhythmia or a primary arrhythmia syndrome in a normal heart without structural problems. These conditions are normally of autosomal dominant inheritance that usually affects healthy individuals.
They can usually be treated if they are recognized at an early stage. Individuals who have these diseases generally have relatives affected by the disease who are asymptomatic.
Hereditary arrhythmia syndromes are seen in more or less 50% of basically unexplained sudden cardiac death cases occurring in younger individuals. Hereditary arrhythmia syndrome is a primary cause in 70% cases of sudden cardiac death while arrhythmogenic structural heart disease is the cause in 30% cases of sudden cardiac death.
Hereditary arrhythmia syndromes are not common but diagnosing these conditions early can lower the risk of sudden death. Hereditary arrhythmia syndromes can be divided into primary arrhythmia syndromes due to dysfunction of the cardiac muscle’s ion channels and primary structural heart disorder with elevated arrhythmia risk.
The structural heart conditions that can be of genetic or hereditary origin are noncompaction cardiomyopathy, arrhythmogenic right-ventricular cardiomyopathy or dysplasia, nonobstructive and hypertrophic obstructive cardiomyopathy, and dilated cardiomyopathy. The most prevalent ion channel diseases are short QT syndrome, long QT syndrome, Brugada syndrome, NS catecholaminergic polymorphous ventricular tachycardia. These diseases may be of genetic origin so it’s worthwhile to do a genetic testing for these diseases.
Catecholaminergic Polymorphic Ventricular Tachycardia
Catecholaminergic polymorphic ventricular tachycardia or CPVT, also known as catecholamine-induced polymorphic ventricular tachycardia or familial polymorphic ventricular tachycardia, is an inherited or genetic heart condition that is defined by an abnormally rapid and irregular rhythm of the heart or arrhythmia as a response to emotional stress or physical activity. Symptoms of the disease may include dizziness, fainting, and lightheadedness. The symptoms of this disease usually manifest when an individual is between 7 to 9 years old. CPVT can cause death and heart attack if it is left untreated. This disease is due to mutations or abnormalities in the CASQ2 or RYR2 genes. This condition is inherited in autosomal recessive manner when the gene mutations in CASQ2 are involved. CPVT is inherited in an autosomal dominant manner when RYR2 gene mutation is involved. In some instances, the underlying cause of CPVT cannot be determined.
RYR2 gene mutations cause around half of the cases of CPVT while CASQ2 gene mutations cause 1 to 2 percent of the cases. As for the rest of the causes that are not accounted for, the genetic cause of the disease is still unknown.
Symptoms of CPVT
These are the following symptoms of CPVT that an individual may have:
- Ventricular tachycardia
- Atrial standstill
- Atrial fibrillation
- Sudden cardiac death
- Autosomal dominant manner of inheritance
- Sudden death
Diagnosing rare and genetic diseases is quite difficult. Doctors usually check for the individual’s medical and family history, do a physical exam and check for symptoms, and eventually recommend laboratory tests. The results of laboratory tests confirm the diagnosis of the condition. Genetic testing is usually performed on diseases that might be of genetic origin. Ventricular tachycardia and its associated cardiac diseases can be diagnosed through an ECG.
The initial diagnostic procedure is a 23-lead resting ECG, a stress ECG, a long-term ECG, and an echocardiographic examination. It is followed by an interview about the family history which encompasses 3 generations. The doctor asks the patient for cases of seizures, syncope, and sudden death in the family.
Clinical evaluation is the first step to determine the probability of the presence of a hereditary arrhythmia syndrome and if it does, genetic testing follows to confirm the diagnosis.
Ventricular tachycardia is not a genetic disorder but the associated heart problems that are present or that can cause it are the ones that may have a genetic or hereditary factor.