tachycardia
Summary
Tachycardia is defined as a heart rate >100 beats per minute in adults. It can be physiological (exercise, fever, anxiety) or pathological (arrhythmias, heart failure, hyperthyroidism). Classification includes supraventricular (SVT) and ventricular tachycardia, with different mechanisms and clinical significance.
Detail
Tachycardia represents an abnormally fast heart rate exceeding 100 bpm in adults (>150 bpm in infants, >120 bpm in children). Physiological causes include exercise, emotional stress, fever, dehydration, and sympathetic stimulation. Pathological causes encompass cardiac arrhythmias (atrial fibrillation, atrial flutter, AVNRT, AVRT, ventricular tachycardia), systemic conditions (hyperthyroidism, anemia, sepsis, shock), and medications (stimulants, bronchodilators, anticholinergics). Supraventricular tachycardia (SVT) originates above the ventricles and typically presents with narrow QRS complexes, while ventricular tachycardia shows wide QRS complexes and carries higher risk of hemodynamic compromise. Clinical presentation varies from asymptomatic to palpitations, chest pain, dyspnea, syncope, or cardiovascular collapse. Management depends on hemodynamic stability, underlying cause, and arrhythmia type, ranging from vagal maneuvers and medications (adenosine, beta-blockers) to cardioversion or ablation procedures.
Sources
- Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine
- Harrison's Principles of Internal Medicine
- Dubin's Rapid Interpretation of EKGs
- American Heart Association Guidelines
- First Aid for USMLE Step 1
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