Overview

Tachycardia describes a heart rate that is faster than normal. In most adults it is defined as a resting heart rate above 100 beats per minute. A faster rhythm can be a normal, transient response to exercise, fever, anxiety or pain, but it can also reflect an underlying cardiac or systemic disorder that requires evaluation. For background on how the heart normally regulates rate, see heart rate basics. For the common adult threshold, see clinical definitions.

Types and distinguishing features

  • Sinus tachycardia – the natural pacemaker (sinus node) fires more rapidly in response to physiological demands; usually regular and gradual in onset.
  • Supraventricular tachycardia (SVT) – rapid rhythms that originate above the ventricles, often abrupt in onset and offset; may cause palpitations and dizziness.
  • Atrial fibrillation and flutter – disorganized or organized rapid atrial activity that produces an irregular or fast ventricular response and can increase stroke risk.
  • Ventricular tachycardia (VT) – fast rhythms that start in the ventricles; can be life‑threatening and, if sustained, may deteriorate to ventricular fibrillation and sudden death. For information on serious outcomes, see risk and mortality.

Causes and physiological mechanisms

Causes span benign to dangerous. Common noncardiac triggers include fever, dehydration, anxiety, stimulant drugs, anemia and thyroid overactivity. Cardiac causes include ischemic heart disease, cardiomyopathy, structural abnormalities and electrolyte disturbances. Mechanistically, tachycardia arises when the heart’s electrical conduction speeds up, abnormal circuits develop, or abnormal cells gain pacemaker activity. A fast heart rate increases the heart muscle’s demand for oxygen and nutrients, which can worsen conditions such as coronary artery disease; this increased demand is discussed in more detail at oxygen and metabolic needs.

Diagnosis

Initial assessment includes a focused history and physical exam to identify symptoms (palpitations, lightheadedness, chest pain, syncope) and triggers. Diagnostic tools commonly used are:

  • 12‑lead electrocardiogram (ECG) to document rhythm and identify features that point to a specific tachyarrhythmia.
  • Ambulatory monitoring (Holter or event recorder) for intermittent symptoms.
  • Blood tests for electrolytes, thyroid function and markers of cardiac injury.
  • Imaging such as echocardiography to evaluate heart structure and function when a cardiac cause is suspected.

Treatment and when to seek care

Treatment depends on the type, severity and underlying cause. Emergency care is required for severe symptoms, low blood pressure, chest pain, or altered consciousness. Options include acute measures (vagal maneuvers, intravenous medications, electrical cardioversion) and longer‑term strategies (beta‑blockers, calcium‑channel blockers, antiarrhythmic drugs, catheter ablation, or implantable devices for high‑risk ventricular arrhythmias). Lifestyle measures and correction of reversible factors (hydration, reducing stimulants, treating thyroid disease) are also important.

Complications, prognosis and prevention

When uncontrolled, tachycardia can reduce cardiac output, worsen heart failure, provoke ischemia, and—in the case of atrial fibrillation—increase the risk of stroke. Ventricular tachycardia can cause sudden cardiac arrest if not promptly treated. Many causes are reversible and treatable; appropriate diagnosis and management substantially reduce risks. For further reading on clinical care pathways and patient advice, consult resources such as professional guidance.

If you experience sustained rapid heartbeats, fainting, chest pain, or severe shortness of breath, seek urgent medical attention. For more detailed patient information and support, see educational materials and professional references at clinical resources.