Tachycardia is the medical term for an abnormally fast heart rate, defined as a resting heart rate above 100 beats per minute in adults. The word derives from the Greek tachys (fast) and kardia (heart). While the heart rate naturally increases during exercise, stress, or fever (physiological sinus tachycardia), pathological tachycardia arises from abnormal electrical activity in the heart itself.
Tachycardia is classified by the site of origin. Supraventricular tachycardia (SVT) refers to fast rhythms originating above the ventricles (in the atria or AV node), including atrial fibrillation, atrial flutter, AVNRT, and AVRT. Ventricular tachycardia (VT) originates in the ventricles and is of greater clinical concern, as very fast ventricular rates may not allow adequate filling and pumping, risking haemodynamic collapse and cardiac arrest. Paroxysmal tachycardia occurs in sudden episodes that start and stop abruptly, lasting seconds to hours.
Symptoms include palpitations, breathlessness, chest tightness, dizziness, and in severe cases, syncope or cardiac arrest. Investigations include ECG (to characterise the rhythm), Holter monitor (to capture intermittent episodes), and echocardiography (to assess cardiac structure).
Treatment depends on the specific arrhythmia. Vagal manoeuvres or adenosine terminate certain SVTs. Antiarrhythmic medications, catheter ablation, cardioversion, and ICD implantation are used for different arrhythmias and risk profiles.
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