Sinus rhythm with a heart rate >100 beats per minute
Impulse comes from sinoatrial node
Increase in sympathetic activity increases the rate of SA node
Sinus tachycardia is a physiologic response to the body’s needs rather than a pathologic cardiac condition
Treatment of the tachyarrhythmia should be directed at correcting the underlying condition and not at suppression of the SA node itself
Maximal sympathetic stimulation can increase the heart rate produced by the SA node to 200 beats/min or, rarely, 220 beats/min in younger individuals
Formula for maximal sinus rate = 220 beats/min - age
Physiological sinus tachycardia
caused by physiological increase in sympathetic activity brought by - emotions, physical exercise, pain, pregnancy
or in some pathological cases – anxiety, panic attack, anaemia, fever, pulmonary embolism, hypoglycaemia and many more
Inappropriate sinus tachycardia
sinus tachycardia >100 bpm at rest or during minimal activity that is out of proportion with the level of stress
occurs in individuals without apparent heart disease or other cause for sinus tachycardia and is generally considered a diagnosis of exclusion
tachycardia tends to be persistent and symptomatic - palpitations, presyncope, rarely syncope.
Characteristically the mean heart rate drops during sleep.
ECG: P wave axis and morphology similar or identical to sinus rhythm.
one P wave for every QRS complex
The PR interval is shorter than during normal sinus - increased sympathetic tone also speeds AV nodal conduction
P wave morphology: - Upright in leads I, II and usually aVF - Inverted in aVR - Upright, biphasic or inverted in III and aVL - The right to left activation results in P waves that are upright or biphasic in V1 and V2, and upright in V3 through V6
The QRS complex is usually normal (if there is no fixed or transient intraventricular conduction disturbance).
This distinction of sinus tachycardia from atrial tachycardias is generally based on the clinical presentation and the onset and termination of the tachycardia. Unlike sinus tachycardia, atrial tachycardias typically have abrupt onset and termination.
ECG 1 Sinus tachycardia
regular narrow complex tachycardia at rate 115 bpm
every QRS complex has a preceding P wave
P wave morphology and axis typical for sinus rhythm - positive in leads I, II, aVF - inverted in aVR
Treat the underlying cause
sinus tachycardia will improve or resolve following treatment directed at the underlying etiology
The heart rate usually declines over time to a level that reflects the degree of activation of the sympathetic nervous system.
Management of inappropriate sinus tachycardia
prognosis of IST is benign
lifestyle interventions such as exercise training, volume expansion, and avoidance of cardiac stimulants should be tried before drug treatment
in highly symptomatic patients - Ivabradine alone or in combination with a beta-blocker should be considered
Strauss, David G., et al. Marriott's Practical Electrocardiography. Wolters Kluwer, 2021
Brugada J, Katritsis DG, Arbelo E, Arribas F, Bax JJ, Blomström-Lundqvist C, Calkins H, Corrado D, Deftereos SG, Diller GP, Gomez-Doblas JJ, Gorenek B, Grace A, Ho SY, Kaski JC, Kuck KH, Lambiase PD, Sacher F, Sarquella-Brugada G, Suwalski P, Zaza A; ESC Scientific Document Group. 2019 ESC Guidelines for the management of patients with supraventricular tachycardiaThe Task Force for the management of patients with supraventricular tachycardia of the European Society of Cardiology (ESC). Eur Heart J. 2020 Feb 1;41(5):655-720. doi: 10.1093/eurheartj/ehz467. PMID: 31504425.