What are the causes of tachycardia (rapid heart rate)?

From the Guidelines

Tachycardia, or a rapid heart rate, is caused by a variety of physiological and pathological factors, including exercise, anxiety, fever, dehydration, stimulant use, cardiac conditions, and certain medications, as noted in the 2016 guideline by the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society 1.

Physiological Causes

Some common physiological causes of tachycardia include:

• Exercise
• Anxiety
• Pain
• Fever
• Dehydration
• Stimulant use, such as caffeine, nicotine, or medications like albuterol

Pathological Causes

Pathological causes of tachycardia encompass:

• Cardiac conditions like atrial fibrillation, atrial flutter, supraventricular tachycardia, ventricular tachycardia, and heart failure
• Other medical conditions, including hyperthyroidism, anemia, shock, sepsis, pulmonary embolism, and electrolyte imbalances, particularly potassium and magnesium
• Certain medications that can cause tachycardia as a side effect, such as some antidepressants, antipsychotics, and bronchodilators

Underlying Mechanisms

The underlying mechanism of tachycardia typically involves either abnormal electrical impulses in the heart or the body's compensatory response to maintain adequate cardiac output and tissue perfusion when faced with stress or reduced oxygen delivery, as discussed in the 2003 guidelines by the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines 1.

Importance of Medical Evaluation

If experiencing persistent tachycardia, medical evaluation is essential to identify and address the specific cause, which may range from lifestyle modifications to medication or procedures depending on the severity and underlying condition. This is crucial because tachycardia can lead to more severe conditions, such as tachycardia-induced cardiomyopathy, as noted in the 2016 scientific statement from the American Heart Association 1.

From the Research

Causes of Tachycardia

• Tachycardia can be physiological or pathological in origin 2
• It can be caused by various factors, including:
  • Acute, often reversible conditions, such as ischemia or QT-prolongation, which can lead to polymorphic ventricular tachycardia 3
  • Focal abnormal activity, such as triggered activity, automaticity, or micro-reentry, which can cause monomorphic ventricular tachycardia 3
  • Arrhythmogenic substrate, such as an infarct scar, which can lead to macro-reentry tachycardia 3
  • Medical conditions, such as pulmonary embolism, anemia, infection, or hyperthyroidism, which can cause sinus tachycardia 4
  • Incompletely defined conditions, such as inappropriate sinus tachycardia, postural tachycardia syndrome, mast cell disorder, or post-COVID syndrome 4
  • Sympathetic overactivity, which can lead to increased heart rate and blood pressure, as well as metabolic abnormalities 5
  • Autonomic control of circulation abnormalities, which can be a marker of an underlying condition 5

Classification of Tachycardia

• Tachycardia can be classified as:
  • Secondary to a specific, usually treatable, medical condition 4
  • Related to incompletely defined conditions, such as inappropriate sinus tachycardia or postural tachycardia syndrome 4
  • Monomorphic or polymorphic ventricular tachycardia, based on the morphology of the tachycardia on the surface ECG 3

Pathophysiological Considerations

• Tachycardia has been associated with increased morbidity and mortality, and can be a marker of underlying pathophysiological conditions 5
• Sympathetic overactivity and autonomic control of circulation abnormalities can contribute to the development of tachycardia and its associated conditions 5