Supraventricular tachycardia (SVT) is a condition where the heart beats unusually fast, with the rapid rhythm originating from its upper chambers. When the heart rate is excessively high, it can struggle to pump enough blood effectively throughout the body. Cardioversion is a medical procedure that restores a normal heart rhythm by resetting the heart’s electrical system to a healthy pattern.
Understanding Supraventricular Tachycardia
Supraventricular tachycardia (SVT) refers to fast heart rhythms originating in the heart’s upper chambers. During an SVT episode, the heart can beat between 140 to 250 times per minute, or even up to 300 beats per minute. This rapid pace reduces the time for the heart’s chambers to adequately fill with blood, decreasing the amount of blood pumped to the body.
Individuals experiencing SVT may report symptoms such as palpitations, lightheadedness, dizziness, and shortness of breath. Chest discomfort, fatigue, and a pounding feeling in the neck are also common. Diagnosis typically involves a physical examination and an electrocardiogram (ECG). For intermittent episodes, an ambulatory electrocardiogram, like a Holter monitor, may be used to track heart rhythm over a longer period.
Cardioversion Explained
Cardioversion resets the heart’s electrical system, which can become disorganized with rapid or irregular beats. The goal is to restore the heart’s natural, coordinated pumping action.
This procedure is typically performed in a hospital setting, often planned but also used in emergencies for severe symptoms. It is a controlled process, distinct from defibrillation, which involves higher energy shocks delivered to a heart that has stopped or is quivering.
When Cardioversion is Considered for SVT
Cardioversion for SVT depends on the patient’s condition and symptom severity. For “unstable” SVT, characterized by severe symptoms such as very low blood pressure, fainting, significant chest pain, or altered mental status, immediate synchronized cardioversion is often necessary. In these urgent situations, the rapid heart rate impairs blood pumping, leading to life-threatening consequences.
For patients experiencing “stable” SVT, where symptoms are less severe, other treatments might be attempted first. Initial approaches may include vagal maneuvers or medications to slow the heart rate. If these less invasive methods are ineffective or the SVT is recurrent and causes significant discomfort, cardioversion remains an important treatment option. The decision is made by a healthcare provider, considering the patient’s overall health, medical history, and SVT characteristics.
Different Approaches to Cardioversion
Cardioversion uses two primary methods: electrical and pharmacological (chemical). Electrical cardioversion involves delivering a controlled electrical shock to the heart through pads or paddles placed on the chest. This procedure is typically performed under sedation, ensuring comfort and minimizing awareness of the shock. The electrical impulse briefly interrupts the heart’s abnormal electrical activity, allowing it to reset to a normal rhythm.
Pharmacological cardioversion uses antiarrhythmic medications to restore a normal heart rhythm. These medications can be administered intravenously or orally, modifying the heart’s electrical signals and slowing its rate. Chemical cardioversion may take minutes, hours, or even days to take effect, depending on the medication and patient’s condition. The choice depends on patient stability, SVT type, and physician assessment.
Other Treatments for SVT
Beyond cardioversion, other treatments manage supraventricular tachycardia. Vagal maneuvers are simple physical actions that stimulate the vagus nerve, helping slow the heart rate by influencing electrical conduction. Common vagal maneuvers include bearing down (Valsalva maneuver), coughing, or immersing the face in ice-cold water. These techniques are often a first-line approach for stable SVT episodes.
Medications manage acute episodes and long-term SVT. These include beta-blockers and calcium channel blockers, controlling heart rate or restoring normal rhythm. Adenosine is another medication administered intravenously for acute SVT, rapidly blocking electrical signals in a specific heart part.
For recurrent SVT, catheter ablation uses heat or cold energy to create small scars in the heart, blocking the abnormal electrical pathways responsible for rapid heartbeats. This procedure offers a high success rate and can provide a permanent solution.