Tachycardia

Tachycardia is a type of arrhythmia that causes an elevated heart rate at rest. In adults, it is defined as more than 100 beats per minute, while in children it is considered above 200 beats per minute, since their heart rate is naturally faster due to physiological immaturity.

An increased heart rate is normal during physical exercise or in situations of emotional stress. Although in some cases it does not represent a pathological condition—being a physiological response to fever or dehydration—when it occurs at rest it is usually a symptom of an underlying condition that, if untreated, may lead to serious health complications.

Depending on its presentation, tachycardia can be classified into two types:

• Paroxysmal tachycardia: sudden and intermittent, occurring in short episodes.
• Chronic tachycardia: persistent condition over time.

Tachycardia can also be classified according to the cardiac region responsible for the increased heart rate:

• Ventricular tachycardia: affects the ventricles, the lower chambers of the heart. Blood flow to the body is reduced, making it a potentially life-threatening condition.
  • Pulseless ventricular tachycardia: a cardiac arrest caused by an excessively fast ventricular rhythm that prevents effective pumping of blood. It is a medical emergency.
  • Ventricular tachycardia with pulse: although dangerous, a pulse is maintained and blood continues to reach tissues, albeit in reduced amounts.
• Supraventricular tachycardia: originates above the ventricles, including the atria, the atrioventricular node, the sinoatrial node, or the conduction pathways between atria and ventricles.
  • Atrial tachycardia: originates in the atria, which beat faster than the ventricles, causing irregular blood flow.
  • Atrioventricular tachycardia: one of the most common arrhythmias. It occurs due to an abnormal electrical circuit in the atrioventricular node, a conduction structure that coordinates electrical signals between atria and ventricles to regulate heart rhythm.
  • Sinus tachycardia: originates in the sinoatrial node, the structure responsible for generating impulses that control heart rhythm, commonly known as the "natural pacemaker of the heart." It is considered normal in cases of fever, dehydration, stress, physical exercise, or consumption of stimulants such as alcohol or caffeine.
  • AV nodal reentrant tachycardia (intranodal tachycardia): caused by dysfunction of the atrioventricular node, which delays electrical signals to allow proper ventricular filling.
  • Atrial flutter: rapid but regular atrial activity (around 300 beats per minute).
  • Atrial fibrillation: the most common arrhythmia, characterized by a chaotic (irregular and rapid) atrial rhythm.

The prognosis of tachycardia varies depending on its type, underlying cause, and the patient’s cardiovascular history. In general, supraventricular tachycardias have a better prognosis than ventricular tachycardias, which may be life-threatening.

Symptoms

Tachycardia symptoms are similar regardless of the cardiac origin. The most common include:

• Palpitations.
• Dizziness.
• Shortness of breath.
• Sweating.
• Weakness.
• Loss of consciousness.
• Angina pectoris: chest pain, pressure, or discomfort.
• Anxiety.
• In severe cases, reduced blood flow to vital organs.

Causes

The most frequent causes of tachycardia are:

• Physical exercise.
• Fever.
• Dehydration.
• Stress.
• Anemia: deficiency of healthy red blood cells.
• Consumption of stimulants such as alcohol, caffeine, tobacco, or drugs.
• Coronary heart disease: hardening of the arteries supplying blood to the heart.
• Mitral regurgitation: the mitral valve does not close properly, allowing blood to flow backward from the left ventricle to the left atrium during systole.
• Aortic stenosis: narrowing of the aortic valve connecting the left ventricle to the aorta.
• Cardiomyopathy: weakening or thickening of the heart muscle.
• Cardiac electrical abnormalities: impaired conduction of electrical impulses regulating heartbeats.
• Previous myocardial infarction: temporary interruption of blood supply to the heart.
• Pericarditis: inflammation of the pericardium.
• Congenital heart disease: structural heart abnormalities present at birth.
• Pneumonia: bacterial or fungal infection of the pulmonary alveoli.
• Chronic obstructive pulmonary disease (COPD): progressive lung damage causing airflow obstruction.
• Pulmonary embolism: blockage of the artery supplying blood to the lungs.
• Hyperthyroidism: excessive thyroid hormone production due to thyroid dysfunction.
• Graves disease: autoimmune disorder stimulating the thyroid and causing hyperthyroidism.
• Thyroiditis: inflammation of the thyroid gland.
• Hypokalemia: low potassium levels.
• Hypomagnesemia: low magnesium levels.

Risk factors

Although tachycardia can affect anyone, risk is higher in the following cases:

• Age: more common in older adults due to natural cardiac aging, leading to stiffness, fibrosis, and electrical system deterioration.
• Hypertension.
• Pregnancy: especially from the second trimester onward, due to increased cardiac output required to support fetal circulation.
• Family history of arrhythmias.
• Sleep apnea.
• Sedentary lifestyle.
• Obesity.
• Smoking.
• Chronic stress.
• Stimulant use.

Complications

Complications depend on the type and frequency of episodes, as well as overall cardiac health. The most relevant include:

• Blood clot formation.
• Heart attack.
• Stroke.
• Frequent fainting.
• Loss of consciousness.
• Heart failure.
• Sudden cardiac death.

Which specialist treats tachycardia?

Tachycardia is treated within the specialty of Cardiology.