4.1.1 Sinus tachycardia
Sinus tachycardia is a quickening of the firing of the sinoatrial node beyond its normal discharge rate, resulting in a heart rate between 90 and 150 beats per minute (bpm). Sinus tachycardia commonly occurs in normal healthy patients with no serious adverse effects. However, persistent sinus tachycardia, especially with acute myocardial infarction, can be serious. It may lead to ischemia and myocardial damage by raising oxygen requirements.
ECG signs of sinus tachycardia:
Heart rate more than 90 per minute.
Normal QRS duration.
Normal PR interval.
The impulse generating the heart beats are normal, but they are occurring at a faster pace than normal.
T wave with normal size and configuration.
Sinus tachycardia is often asymptomatic. If the heart rate is too high, cardiac output may fall due to the markedly reduced ventricular filling time. Rapid rates, though they may be compensating for ischemia elsewhere, increase myocardial oxygen demand and reduce coronary blood flow, thus precipitating an ischemia heart or valvular disease.