Tachycardia is defined as an elevated heart rate, usually when it is above 100 beats per minute. Depending on the source of the impulse generating the tachycardia, it is called supraventricular or ventricular. Supraventricular tachycardias are those in which the electrical activity that produces them is located above the ventricles, either in the atria or in the atrioventricular node. They most frequently occur paroxysmally (in episodes), while incessant tachycardias (sustained or with continuous episodes) are less common.
What are the causes of supraventricular tachycardia?
In most cases, supraventricular tachycardia occurs in patients without structural heart disease. In these patients, tachycardias are caused by an abnormality in the genesis or conduction of the heart’s electrical impulses. Typically, there is an abnormal bundle that conducts electricity through an accessory area. The most common are intranodal tachycardias (the circuit occurs in the atrioventricular node) and those secondary to pre-excitation (the most characteristic being Wolff-Parkinson-White syndrome). In fewer cases, it occurs as a consequence of heart disease. Any cardiac abnormality, congenital or acquired, can lead to supraventricular tachycardia. Attacks can be triggered by physical exercise or emotional stress, but frequently no triggering factor is found.
What are the symptoms of supraventricular tachycardia?
- Patients often report palpitations in the heart area, anxiety, nervousness, and chest discomfort.
- Occasionally, they report dizziness, dyspnea, or angina.
- Syncope, heart failure, or myocardial infarction are also possible, but very rare and usually occur in patients with structural heart disease.
On physical examination:
- The most notable finding is a rapid and regular pulse.
- Hypotension is present in many cases, but it is often mild.
- Polyuria (excessive urine excretion) sometimes occurs at the end of the attack, a phenomenon that appears to be secondary to atrial dilation and the subsequent release of atrial natriuretic peptide caused by the tachycardia.
How is the diagnosis made?
Since supraventricular tachycardias are generally benign, they do not normally require invasive testing, and their diagnosis is commonly based on their symptoms and, above all, with an electrocardiogram and Holter monitor.
This is sufficient to make the diagnosis in most cases, and although the origin and mechanism of the tachycardia are sometimes uncertain, the data obtained are sufficient for determining the appropriate antiarrhythmic treatment. Invasive diagnostic methods, primarily electrophysiological studies, are reserved for cases that are difficult to control, with severe symptoms or a risk of ventricular arrhythmias.
What is the treatment for supraventricular tachycardia?
Initial treatment for supraventricular tachycardia attacks depends on the patient’s clinical condition. In most cases, the patient is stable, so the usual approach is to attempt to reverse the arrhythmia with vagal maneuvers (Valsalva maneuver, carotid sinus or ocular compression) or antiarrhythmic drugs. In addition, a slow saline drip should be administered, blood pressure measurements should be taken frequently, and continuous electrocardiographic monitoring should be maintained. Cases with significant symptoms require emergency department assistance. If the patient presents with severe decompensation, such as acute pulmonary edema or shock, immediate electrical cardioversion is indicated.
In preventing paroxysms, the first step is to eliminate potential triggering factors. If attacks are infrequent, well tolerated, and easily controlled, chronic drug treatment is not necessary. Otherwise, antiarrhythmic drugs can prevent episodes. When these measures fail, catheter ablation or implantation of an antitachycardia pacemaker may be indicated. If the arrhythmia is chronic, maintenance treatment is aimed at heart rate control.
Prognosis
Supraventricular tachycardias usually have a benign prognosis and do not usually lead to serious complications. Only in patients with significant structural heart disease, tachycardia can lead to cardiac decompensation, sometimes severe. In some patients, tachycardias can be prevented with medication. When ablation is performed, it is effective in most cases and a cure can be achieved. Generally, the prognosis is similar to that of a normal person.
