Inadequate sinus tachycardia

The Inadequate sinus tachycardia (IST) , first described in 1979, is a rare type of heart rhythm disturbances within the category of supraventricular tachycardia (SVT) . In the case of inadequate sinus tachycardia, the frequency of the sinus node exceeds 100 beats / min without any connection with physical stress or psychological excitement or other secondary causes for an increase in frequency.

root cause

Inadequate sinus tachycardia is caused by an abnormality in the sinus node . In addition to the sinus node, there may be cells that cause sudden increases in frequency due to a decoupling from the autonomic nervous system , which are mostly catecholamine-dependent.

Symptoms

Symptoms reported by patients vary in frequency and severity. Mostly a variety of symptoms are reported. The symptoms of the IST are occasionally severe and stressful, a significant reduction in quality of life is not uncommon. They can include:

Frequent or persistent palpitations / racing heart
dizziness
Dyspnoea (shortness of breath) and palpitations on exertion
fatigue
Exercise intolerance
States of exhaustion
sweat
Chest pain
Drowsiness
Pre-syncope (feeling like passing out)

frequency

Inadequate sinus tachycardia is very rare. The prevalence of the IST relates to middle-aged patients and is more common than previously assumed at around 1%. Patients are particularly affected (up to 90%).

trigger

The following are discussed as possible triggers of an IST:

a previous viral infection
exposure to toxins
an endocardial catheter ablation with accidental modulation of the local autonomic nervous system

Electrocardiogram (EKG)

The P-wave configuration corresponds to the configuration in a physiological sinus rhythm . The diagnosis cannot be made on the basis of a single 12-lead resting ECG. A long-term ECG is necessary for the detection of constantly increased heart rates . The nightly frequency reduction is absent or at least weakened. A carefully kept activity log is necessary in order to objectify the inadequacy of the high frequencies.

Diagnosis

Before making a diagnosis of inadequate sinus tachycardia, causes of physiological sinus tachycardia must be ruled out. The following can be observed:

Exclusion of all other causes of secondary (adequate) sinus tachycardia (anemia, pain, anxiety disorder, hyperthyroidism, hormonal disorders, medication ...)
Common forms of supraventricular tachycardia (SVT) must be ruled out
Normal P-wave morphology
A sinus tachycardia at rest (but not always) usually available
Minimal heart rate reduction at night
Inadequate (inappropriate) heart rate response during exertion
Average heart rate in 24 hours> 95 beats / min
It is documented that the symptoms are due to tachycardia
Hypotension is occasionally observed
Syncope (fainting) has been reported occasionally

Differential diagnoses

In addition to a physiological sinus tachycardia, the inadequate sinus tachycardia must be opposed

Sinus node reentry tachycardias,
postural orthostatic tachycardia syndrome ,
atrial tachycardias originating near the sinus node (and thus similar P-wave configuration) and
other paroxysmal supraventricular tachycardias ( AV node reentry tachycardia , AV reentry tachycardia)

be delimited.

therapy

Both pathogenesis and long-term prognosis are incompletely understood, which is why the treatment of inadequate sinus tachycardia in clinical routine is often difficult. The treatment turns out to be complex in view of the multidimensional clinical picture, ie a multidisciplinary approach is appropriate for the majority of patients. Endurance training is sometimes recommended for patients with milder symptoms. In drug therapy resistance a Radiofrequenzstromablation (RFC ablation) should be considered. In the case of inadequate sinus tachycardia, RFC ablation is not suitable as the sole form of therapy, but rather an integral part of a comprehensive treatment concept. So-called hybrid therapy seems to offer advantages, i. H. the combination of different treatment strategies that exceed the effectiveness of a single measure. In individual cases of otherwise refractory treatment, successful surgical excision of the sinus node has been reported as an "ultima ratio".

Medication

Beta-blockers (treatment of first choice), calcium antagonists , IC antiarrhythmics or combination therapy, cardiac glycosides , off-label trial with ivabradine

Radio frequency current ablation

The role of sinus node ablation or modification has not yet been clearly defined.
There is a risk of obliteration or considerable restriction of the sinus node function due to the RFC procedure.
Although favorable short-term observations are available (76%), the long-term results of RFC ablation at IST are rather disappointing (approx. 65%).
There is the possibility of requiring a pacemaker and other procedural complications (persistent junctional rhythm, superior vena cava syndrome, diaphragmatic paralysis (phrenic nerve lesion), pericarditis, dysautonomy ).
Cardiac and extracardiac symptoms often persist even after RFC ablation. This observation suggests that the pathogenesis is at least partially determined extracardially.
Some symptoms can be interpreted as secondary manifestations of autonomic dysregulation.
If the sinus node is completely destroyed by RFC, permanent pacemaker stimulation is necessary in most cases .

forecast

The forecast of IS is not yet clearly understood. The risk of cardiomyopathy induced by tachycardia is largely unknown and is estimated to be very low, which has only been reported in isolated cases. Little information is available about the long-term outcomes of this disease, although no known mortality is known. IST is believed to be a chronic disease . It has been suggested that untreated IST is predisposed to the development of systemic hypertension .