Related article: Supraventricular tachycardias.
Inappropriate sinus tachycardia is a tachycardia generated in the sinus node, wich appears at rest or in situations of mild effort, and it is accompanied by a set of symptoms that can be disabling for the patient.
The mechanisms of the inappropriate sinus tachycardia are not fully specified.1 2
It is important to distinguish it from the sinus tachycardia itself and other similar, such as postural orthostatic tachycardia syndrome, because their symptoms can be confused.1
Inappropriate sinus tachycardia is a rare arrhythmia. It is more frequent in females and in the age range between 15 and 45 years.
It presents a varied symptomatology. The most common symptoms are palpitations and dyspnea, although, chest pain, dizziness, presyncope, and in some cases, syncope may also appear chest.2 3
These symptoms are in relation to sinus tachycardia and they are usually triggered by mild exercise, psychological stress or postural changes.1 2
Although symptoms can be disabling, inappropriate sinus tachycardia has a benign prognosis.
It is often confused with psychological symptoms or anxiety, which tends to delay the diagnosis.2
Electrocardiogram of sinus tachycardia
The diagnosis of inappropriate sinus tachycardia is a diagnosis of exclusion.1 2 3
It is essential to rule out more common types of supraventricular tachycardias (SVT), such as AV nodal reentrant tachycardia (AVNRT), atrial flutter, or atrial tachycardia.
In certain cases, an electrophysiology study may be necessary to definitively exclude other underlying causes of tachycardia.
Furthermore, secondary causes of "appropriate" sinus tachycardia (e.g., fever, hyperthyroidism, hypoxia, or substance use/toxicity, among others) must be ruled out.2 3
The presence of sinus tachycardia during physiological states that do not warrant such a response, when accompanied by clinical symptoms, strongly supports the diagnosis.
Lifestyle modifications are recommended, specifically avoiding triggers or stimulants such as caffeine, nicotine, and alcohol.2
The primary pharmacological treatments for inappropriate sinus tachycardia are beta-adrenoceptor blockers (beta-blockers) and non-dihydropyridine calcium channel blockers (such as diltiazem and verapamil).
Treatment is typically initiated at low doses with subsequent up-titration based on clinical symptomatology.
Increased intake of salt and fluids (volume expansion) may also alleviate clinical symptoms in these patients.
Ivabradine —a selective I f channel inhibitor that acts directly on the sinoatrial node— has emerged. While its primary indications are for ischemic heart disease and heart failure, it is now considered a viable alternative for the treatment of inappropriate sinus tachycardia.4
In refractory or extreme cases, patients may require selective or complete SA node ablation. This procedure may necessitate the implantation of a permanent pacemaker.
Inappropriate sinus tachycardia is an uncommon arrhythmia originating in the sinoatrial node. It is characterized by elevated heart rates in response to minimal stimuli that are disproportionate to the patient's physiological requirements.
The electrocardiogram findings are identical to those of sinus tachycardia. Despite a clinical presentation that can be significantly symptomatic, the prognosis is benign.
Currently, management is centered on pharmacological agents that reduce the sinus node firing rate, primarily beta-blockers and non-dihydropyridine calcium channel blockers.
Related article: Supraventricular tachycardias.
