Sinus tachycardia: signs, symptoms, and causes
Tachycardia alone is a very nonspecific symptom. Its symptomatic value depends on the clinical circumstances. It has limited value in predicting volume loss. If combined with other symptoms, it is valuable in predicting pneumonia
The heart rate is more than 100 beats/min.
Flow chart Tachycardia mechanism
Sinus tachycardia is associated with many different conditions. Maybe a normal physiological response or the result of a pathological response. Those conditions include:
Decreased cardiac output (heart failure).
Sinus rhythm dysfunction.
Stimulants and drugs (eg, caffeine, beta-2 agonists, cocaine).
A clear understanding of the mechanism of each cause of tachycardia has not been established. Most of the pathways in cases of sinus tachycardia are by sympathetic activation and/or catecholamine release. This is typical in cases of anxiety, fear, and hypovolemia, but is not typical in cases of pheochromocytoma or drugs that release (or cause the release of) catecholamines.
Mechanism in Hyperthyroidism
The mechanism of tachycardia in hyperthyroidism is unique and results from elevated T3 levels.
T3 is both genomic (regulated and expressed by a single gene) and non-genomic in affecting production and altering the activity of myofibril protein, endoplasmic reticulum, ATPase, and Na, K, and Ca channel. The end result is increased contractility, increased heart rate, and increased cardiac output.
Tachycardia alone is a very nonspecific symptom. Its symptomatic value depends on the clinical circumstances. However, studies show that:
It has limited value in predicting volume loss.
If combined with other symptoms, it is valuable in predicting pneumonia.
In trauma, infectious pneumonia, and myocardial infarction, tachycardia has prognostic value and predictive value for increased mortality.