Definition
Tachycardia is a medical condition characterized by a resting heart rate that exceeds the normal upper limit for a given age group. In adults, this is typically defined as a heart rate greater than 100 beats per minute (bpm) while at rest.
Overview
Tachycardia can be physiological, occurring transiently in response to exercise, stress, fever, anemia, or stimulant use, or it can be pathological, reflecting underlying cardiac or systemic disorders. Persistent or recurrent tachycardia may impair cardiac efficiency, reduce myocardial perfusion, and increase the risk of arrhythmias, heart failure, or thromboembolic events. Diagnosis is usually established through electrocardiographic (ECG) monitoring, Holter recording, or event monitoring, supplemented by clinical evaluation to identify precipitating factors.
Etymology/Origin
The term derives from the Greek words tachýs (ταχύς), meaning “swift” or “rapid,” and kárdios (καρδία), meaning “heart.” It entered English medical terminology in the late 19th century.
Characteristics
- Threshold values: Resting heart rate > 100 bpm in adults; age‑adjusted thresholds are applied for children (e.g., > 180 bpm in infants).
- Types:
- Sinus tachycardia: Originates from the sinoatrial node; often a normal response to physiological demand.
- Supraventricular tachycardia (SVT): Includes atrioventricular nodal re‑entrant tachycardia (AVNRT) and atrial tachycardia; characterized by rapid atrial rates and narrow QRS complexes.
- Ventricular tachycardia (VT): Originates in the ventricles; associated with wide QRS complexes and higher risk of degeneration to ventricular fibrillation.
- Atrial flutter: Organized atrial activity with rates typically around 250–350 bpm, resulting in a ventricular rate that may be rapid if not controlled.
- Symptoms: Palpitations, chest discomfort, dyspnea, dizziness, syncope, or fatigue; asymptomatic cases are also common.
- Diagnostic tools: 12‑lead ECG, continuous cardiac monitoring, electrophysiological study, laboratory tests to assess electrolytes, thyroid function, and drug levels.
- Management: Treatment strategies depend on etiology and severity and may include:
- Removal of precipitating factors (e.g., fever, stimulants).
- Pharmacologic agents such as β‑blockers, calcium‑channel blockers, or anti‑arrhythmic drugs.
- Electrical cardioversion for hemodynamically unstable tachyarrhythmias.
- Catheter ablation for refractory SVT or VT.
Related Topics
- Bradycardia (slow heart rate)
- Arrhythmia (general term for abnormal heart rhythms)
- Heart rate variability
- Cardiovascular physiology
- Syncope and presyncope
- Electrocardiography (ECG)
- Cardiac electrophysiology
- Autonomic nervous system regulation of heart rate
- Pharmacologic agents affecting heart rate (β‑blockers, calcium channel blockers, etc.)