Inappropriate sinus tachycardia
Encyclopedia
Inappropriate Sinus Tachycardia (IST) is a rare type of cardiac arrhythmia, within the category of supraventricular tachycardia
(SVT), although doctors believe it stems from dysautonomia
, a disturbance and/or failure of the autonomic nervous system.
The mechanism and primary etiology
of Inappropriate Sinus Tachycardia has not been fully elucidated. The mechanism of the arrhythmia primarily involves the sinus node and peri-nodal tissue and does not require the AV node
for maintenance. Treatments in the form of pharmacological therapy or catheter ablation
are available, although it is currently difficult to treat successfully.
Symptoms associated with IST include:
Some types of medication tried by cardiologists and other physicians include: beta blocker
s, selective sinus node If channel inhibitors (ivabradine
), calcium channel blocker
s and antiarrhythmic agent
s. Some SSRI drugs are also occasionally tried and also treatments more commonly used to treat postural orthostatic tachycardia syndrome
such as fludrocortisone
. This approach is very much "trial-and-error". Patients with IST are often intolerant to beta blocker
s. A new selective sinus node inhibitor ivabradine
is also being used to treat IST.
Invasive treatments include forms of catheter ablation
such as sinus node modification (selective ablation of the sinus node), complete sinus node ablation (with associated implantation of a permanent artificial pacemaker
) and AV node ablation in very resistant cases (creation of iatrogenic complete heart block, necessitating implantation of a permanent artificial pacemaker
).
Supraventricular tachycardia
Supraventricular tachycardia is a general term that refers to any rapid heart rhythm originating above the ventricular tissue. Supraventricular tachycardias can be contrasted to the potentially more dangerous ventricular tachycardias - rapid rhythms that originate within the ventricular...
(SVT), although doctors believe it stems from dysautonomia
Dysautonomia
Dysautonomia is a broad term that describes any disease or malfunction of the autonomic nervous system. This includes postural orthostatic tachycardia syndrome , inappropriate sinus tachycardia , vasovagal syncope, mitral valve prolapse dysautonomia, pure autonomic failure, neurocardiogenic...
, a disturbance and/or failure of the autonomic nervous system.
The mechanism and primary etiology
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
of Inappropriate Sinus Tachycardia has not been fully elucidated. The mechanism of the arrhythmia primarily involves the sinus node and peri-nodal tissue and does not require the AV node
Atrioventricular node
The atrioventricular node is a part of the electrical control system of the heart that coordinates heart rate. It electrically connects atrial and ventricular chambers...
for maintenance. Treatments in the form of pharmacological therapy or catheter ablation
Catheter ablation
Catheter ablation is an invasive procedure used to remove a faulty electrical pathway from the hearts of those who are prone to developing cardiac arrhythmias such as atrial fibrillation, atrial flutter, supraventricular tachycardias and Wolff-Parkinson-White syndrome.It involves advancing several...
are available, although it is currently difficult to treat successfully.
Symptoms
Symptoms reported by patients vary in frequency and severity.Symptoms associated with IST include:
- Frequent palpitations
- DyspneaDyspneaDyspnea , shortness of breath , or air hunger, is the subjective symptom of breathlessness.It is a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations...
(shortness of breath) and palpitations on exertion - Pre-syncopeSyncope (medicine)Syncope , the medical term for fainting, is precisely defined as a transient loss of consciousness and postural tone characterized by rapid onset, short duration, and spontaneous recovery due to global cerebral hypoperfusion that most often results from hypotension.Many forms of syncope are...
(feeling as if about to faint) - Fatigue (physical)Fatigue (physical)Fatigue is a state of awareness describing a range of afflictions, usually associated with physical and/or mental weakness, though varying from a general state of lethargy to a specific work-induced burning sensation within one's muscles...
- DizzinessDizzinessDizziness refers to an impairment in spatial perception and stability. The term is somewhat imprecise. It can be used to mean vertigo, presyncope, disequilibrium, or a non-specific feeling such as giddiness or foolishness....
- Exercise intoleranceExercise intoleranceExercise intolerance is a condition where the patient is unable to do physical exercise at the level or for the duration that would be expected of someone in his or her general physical condition, or experiences unusually severe post-exercise pain, fatigue, or other negative effects...
- Occasional paresthesiaParesthesiaParesthesia , spelled "paraesthesia" in British English, is a sensation of tingling, burning, pricking, or numbness of a person's skin with no apparent long-term physical effect. It is more generally known as the feeling of "pins and needles" or of a limb "falling asleep"...
and cramping - Symptoms associated with autonomic nervous systemAutonomic nervous systemThe autonomic nervous system is the part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils,...
disturbance, including GI disturbance
Diagnosis
No formal diagnostic criteria exist. A diagnosis of Inappropriate sinus tachycardia is primarily one of exclusion and the following may be observed:- Exclusion of all other causes of sinus tachycardiaSinus tachycardiaSinus tachycardia is a heart rhythm with elevated rate of impulses originating from the sinoatrial node, defined as a rate greater than 100 beats/min in an average adult. The normal heart rate in the average adult ranges from 60–100 beats/min...
- Common forms of supraventricular tachycardiaSupraventricular tachycardiaSupraventricular tachycardia is a general term that refers to any rapid heart rhythm originating above the ventricular tissue. Supraventricular tachycardias can be contrasted to the potentially more dangerous ventricular tachycardias - rapid rhythms that originate within the ventricular...
(SVT) must be excluded - Normal P wave morphology
- A resting sinus tachycardiaSinus tachycardiaSinus tachycardia is a heart rhythm with elevated rate of impulses originating from the sinoatrial node, defined as a rate greater than 100 beats/min in an average adult. The normal heart rate in the average adult ranges from 60–100 beats/min...
is usually (but not always) present - Nocturnal dip in heart rateHeart rateHeart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
- Inappropriate heart rateHeart rateHeart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
response on exertion - Mean heart rateHeart rateHeart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
in 24hrs >95bpm - Symptoms are documented to be due to tachycardiaTachycardiaTachycardia comes from the Greek words tachys and kardia . Tachycardia typically refers to a heart rate that exceeds the normal range for a resting heart rate...
- Hypotension is occasionally observed
- SyncopeSyncope (medicine)Syncope , the medical term for fainting, is precisely defined as a transient loss of consciousness and postural tone characterized by rapid onset, short duration, and spontaneous recovery due to global cerebral hypoperfusion that most often results from hypotension.Many forms of syncope are...
(fainting) is occasionally reported
Treatment
IST has been treated both pharmacologically and invasively, with varying degrees of success.Some types of medication tried by cardiologists and other physicians include: beta blocker
Beta blocker
Beta blockers or beta-adrenergic blocking agents, beta-adrenergic antagonists, beta-adrenoreceptor antagonists or beta antagonists, are a class of drugs used for various indications. They are particularly for the management of cardiac arrhythmias, cardioprotection after myocardial infarction ,...
s, selective sinus node If channel inhibitors (ivabradine
Ivabradine
Ivabradine is a novel medication used for the symptomatic management of stable angina pectoris. It is marketed under the trade name Procoralan , Coralan in India , Australia or such as in Italy Corlentor , and was also known as S-16257 during its development...
), calcium channel blocker
Calcium channel blocker
A calcium channel blocker is a chemical that disrupts the movement of calcium through calcium channels.CCB drugs devised to target neurons are used as antiepileptics. However, the most widespread clinical usage of calcium channel blockers is to decrease blood pressure in patients with...
s and antiarrhythmic agent
Antiarrhythmic agent
Antiarrhythmic agents are a group of pharmaceuticals that are used to suppress abnormal rhythms of the heart , such as atrial fibrillation, atrial flutter, ventricular tachycardia, and ventricular fibrillation....
s. Some SSRI drugs are also occasionally tried and also treatments more commonly used to treat postural orthostatic tachycardia syndrome
Postural orthostatic tachycardia syndrome
Postural orthostatic tachycardia syndrome is a condition of dysautonomia, more specifically orthostatic intolerance, in which a change from the supine position to an upright position causes an abnormally large increase in heart rate, called tachycardia...
such as fludrocortisone
Fludrocortisone
Fludrocortisone is a synthetic corticosteroid with moderate glucocorticoid potency and much greater mineralocorticoid potency. The brand name in the U.S. and Canada is Florinef.-Uses:...
. This approach is very much "trial-and-error". Patients with IST are often intolerant to beta blocker
Beta blocker
Beta blockers or beta-adrenergic blocking agents, beta-adrenergic antagonists, beta-adrenoreceptor antagonists or beta antagonists, are a class of drugs used for various indications. They are particularly for the management of cardiac arrhythmias, cardioprotection after myocardial infarction ,...
s. A new selective sinus node inhibitor ivabradine
Ivabradine
Ivabradine is a novel medication used for the symptomatic management of stable angina pectoris. It is marketed under the trade name Procoralan , Coralan in India , Australia or such as in Italy Corlentor , and was also known as S-16257 during its development...
is also being used to treat IST.
Invasive treatments include forms of catheter ablation
Catheter ablation
Catheter ablation is an invasive procedure used to remove a faulty electrical pathway from the hearts of those who are prone to developing cardiac arrhythmias such as atrial fibrillation, atrial flutter, supraventricular tachycardias and Wolff-Parkinson-White syndrome.It involves advancing several...
such as sinus node modification (selective ablation of the sinus node), complete sinus node ablation (with associated implantation of a permanent artificial pacemaker
Artificial pacemaker
A pacemaker is a medical device that uses electrical impulses, delivered by electrodes contacting the heart muscles, to regulate the beating of the heart...
) and AV node ablation in very resistant cases (creation of iatrogenic complete heart block, necessitating implantation of a permanent artificial pacemaker
Artificial pacemaker
A pacemaker is a medical device that uses electrical impulses, delivered by electrodes contacting the heart muscles, to regulate the beating of the heart...
).
See also
- Supraventricular tachycardiaSupraventricular tachycardiaSupraventricular tachycardia is a general term that refers to any rapid heart rhythm originating above the ventricular tissue. Supraventricular tachycardias can be contrasted to the potentially more dangerous ventricular tachycardias - rapid rhythms that originate within the ventricular...
- Sinus tachycardiaSinus tachycardiaSinus tachycardia is a heart rhythm with elevated rate of impulses originating from the sinoatrial node, defined as a rate greater than 100 beats/min in an average adult. The normal heart rate in the average adult ranges from 60–100 beats/min...
- Postural orthostatic tachycardia syndromePostural orthostatic tachycardia syndromePostural orthostatic tachycardia syndrome is a condition of dysautonomia, more specifically orthostatic intolerance, in which a change from the supine position to an upright position causes an abnormally large increase in heart rate, called tachycardia...
- DysautonomiaDysautonomiaDysautonomia is a broad term that describes any disease or malfunction of the autonomic nervous system. This includes postural orthostatic tachycardia syndrome , inappropriate sinus tachycardia , vasovagal syncope, mitral valve prolapse dysautonomia, pure autonomic failure, neurocardiogenic...