Ventricular tachycardia (VT) is caused by irregular electrical activity in the heart ventricles, causing regular and fast heart rate. Although a few seconds of VT may not be a cause for problems, prolonged VT is dangerous. Short periods may happen, and they may be accompanied by chest pain, palpitations, or light-headedness. However, prolonged VT may result in cardiac arrest, further developing into ventricular fibrillation. VT is only found initially in about 7% of people who have undergone cardiac arrest.
VT can occur due to aortic stenosis, coronary heart disease, electrolyte imbalances, or heart attacks. The diagnosis of VT is made through the use of an electrocardiogram (ECG) when the rate of greater than 120 beats per minute is seen. This should be accompanied by three with QRS complexes sequentially. VT is classified as sustained versus non-sustained by whether or not it occurs less than or more than 30 seconds. VT encompasses a group of irregular heartbeats that include ventricular fibrillation and ventricular tachycardia.
In those whose blood pressure is normal, and with a strong pulse, anti-arrhythmic drugs may be used. In other cases, cardioversion should be the main form of therapy.
In VT, the heart beat is too rapid. As a consequence, the ventricles cannot pump oxygen-rich blood to the rest of the body. VT can be fatal if left untreated. The symptoms of VT include the following. Palpitations, which is an uncomfortable feeling that the heart is beating too rapidly or irregularly, are signs of VT. Another sign is accompanying dizziness or light-headedness. Shortness of breath is another sign, as well as chest pain or pressure. Syncope, or fainting, as well as the sensation that one is almost fainting, can also point to a diagnosis of VT. A weak pulse or no pulse can also be used as a sign that VT is occurring.
Ventricular tachycardia often occurs when there is already a structural heart disease. However, VT can occur in its absence. Ischemic heart disease is the most likely cause of prolonging ventricular arrhythmias. The most common cause of out-of-hospital sudden death is acute coronary ischemia, which causes polymorphic VT. During acute ischemia, potassium leaks and this gets into the extracellular space. This depolarizes the myocytes in the ischemic border zone. This depolarization leads to the varied conduction that provides a substrate for re-entry, thus causing polymorphic VT or ventricular fibrillation.
Sustained monomorphic VT is most commonly due to a scar in the myocardium. The most common cause of a scar is an old infarct that was either undetected or healed.
A number of genetic conditions may also cause VT and sudden death even without structural heart disease. Most of these genetic disorders are classified as ion channel abnormalities. For instance, long QT syndrome results from either sodium or potassium abnormalities. These typically manifest as prolong QT intervals when assessed using an ECG. Syncope and sudden death that arise from polymorphic VT often have QRS that are waxing and waning.
Idiopathic VT may also occur. These result when there are no structural heart abnormalities, no genetic conditions, and no metabolic conditions that cause VT. Idiopathic VT usually arises from a few specific spots that can be identified by the ECG machine. Most of them originate from the right ventricular outflow tract (RVOT). Thus, they have left bundle branch block morphology. Idiopathic RVOT tachycardia comes from a focus, which then leads to an intracellular calcium overload.
The risk factors for VT are the same as that for heart disease. People with high blood pressure, or hypertension, are at an increased risk. High cholesterol, diabetes, and smoking are also risk factors. Being obese or overweight has also been linked to an increased risk of heart disease. Having a family history of early heart disease is another risk factor. A sedentary lifestyle and an unhealthy diet are two other modifiable risk factors for heart disease. Age is a risk factor (55 years and older for women). After menopause, women are more likely to get heart disease because estrogen production decreases. Women who go through early menopause may also have an increased risk. Women who undergo hysterectomies also undergo early menopause and thus acquire the same risk.
Another reason for the increased risk of aging is that middle age is the period when women tend to develop the other risk factors that cause heart disease. A family history of heart disease is another risk factor that cannot be changed. Pre-eclampsia is another risk factor that cannot be controlled.
High blood cholesterol increases your chances of coronary heart disease and heart attack. There are two main types of cholesterol that travel through the bloodstream. The low-density lipoproteins (LDL) cholesterols are deemed as harmful because they carry cholesterol to tissues, including the cardiac arteries. A high LDL level increases the risk for cardiovascular diseases.
High-density lipoproteins (HDL) is deemed as good cholesterol because it removes cholesterol from arteries. A low HDL level increases the risk for heart disease.
High blood pressure is defined as levels above 120/80 mmHg. Pressures above this increase a person’s risk of developing heart disease. The risk grows as the blood pressure increases.
Diabetes and prediabetes are also risk factors. Over time, a sustained level of glucose in the body can cause plaque build-up in the arteries, which doubles a person’s chances of acquiring heart disease. Prediabetes is a condition in which the person’s blood sugar is higher than normal but not as high as in diabetes. People with prediabetes are also at an increased risk for heart disease. Being overweight or obese increases a person’s chances of acquiring heart disease.
The complications of ventricular tachycardia depend on a number of factors, such as the severity of the disease, the person’s age, and the frequency with which VT happens, the duration of the rapid heart beat, and the existence of other heart conditions.
Possible complications include the inability of the heart to pump blood, also known as heart failure. Other possible complications may include frequent fainting spells or unconsciousness. VT may also lead to sudden death by cardiac arrest.
The diagnosis of VT relies on ECG readings. An ECG is a machine with probes that are attached to a patient’s chest to record the heart rhythm. Another tool to help diagnose VT is electrophysiology testing. During this test, catheters equipped with electrodes will be placed into the body at several points. These include the veins at the groin. They will be placed directly into the heart to study the electrical activity of the heart as well as to create a map of the different regions. Using this study, the doctor can precisely map out where abnormalities are present.
The goals of treating VT are to manage any underlying disease and to prevent future episodes of the disease. However, in an emergency setting, the immediate goal is to bring the heart rate back to normal. This may involve the use of CPR, giving IV drugs, or electrical defibrillation.
Most patients with VT have two options for treatment. These include radiofrequency catheter ablation (RCA) and an implantable cardioverter defibrillator (ICD). Both of these two options are associated with good outcomes.
RCA is performed by cardiologists and requires that a patient undergoes electrophysiological tests first. The physician then uses a catheter with a special tip. The tip emits a high-frequency electric current. It is used to destroy a small amount of tissue, which is called an ablation procedure. Ablation of VT has had a long history of success and safety. For many patients, RCA completely cures the VT and they require no further treatment. For other patients, RCA enhances the efficacy of an ICD.
An ICD is a device that is implanted under the skin and monitors and controls the heart’s rhythm. It consists of a pulse generator and lead wires. The leads are placed in direct contact with the heart through the veins. The leads transmit the electrical activity of the heart to the main computer chip. The chip responds if it detects an abnormal rhythm by restoring the normal rhythm of the heart.
Clinical studies have shown that ICDs are very successful in a large number of patients in which VT was diagnosed. Other treatment options include drugs to slow down the heart rate. These drugs can be effective, but they are associated with some serious and life-threatening side effects.
Preventing VT starts with preventing heart disease. Smoking should be avoided. Patients should be advised to exercise regularly and to eat a healthy diet. In addition, people should also be advised to refrain from consuming too much fatty food, as this raises blood pressure and cholesterol in the blood. Another way to prevent VT is to ensure that any recommendations made by physicians about previous heart conditions are followed. Regular check-ups with the doctor are important for ensuring that the disease is detected early on. These preventive measures can help people lead healthier lives by reducing their risk of heart disease.