A tachycardia ( ancient Greek ταχυκαρδία tachycardia , German , Schnellherzigkeit ' , commonly palpitations ) is a continuing accelerated pulse to over 100 beats per minute in adults; From a pulse of 150 beats / min one speaks of pronounced tachycardia. The causes can be varied. The opposite of tachycardia - a heart rate below 60 beats per minute - is bradycardia .
- A tachycardia of over 100 beats per minute is normal with physical exertion. The heart rate in small children can be over 100 even at rest, without this being pathological.
- Conditioned by the heart itself, e.g. B. by additional conduction paths, other disturbances in the excitation conduction system or z. B. from circulatory disorders in the heart muscle . The doctor differentiates between ventricular (starting from the ventricle) and supraventricular (arising above the ventricle) tachycardias, with the ventricular tachycardias being more dangerous because they usually originate from a sick ventricle.
- Caused by hormones or neurotransmitters that affect the conduction system or the heart muscle. These include thyroid hormones and catecholamines . See also Graves' disease
Congenital tachycardia is a special case. This is based on faulty conduction of excitation to the heart and can be cured surgically.
Classifications of tachycardia
There are several possible classifications of tachycardia. In medicine, a distinction is usually made anatomically between atrial and ventricular tachycardia, especially since this classification is also of certain importance for assessing the danger. If the heart contracts fast enough, blood may no longer be pumped because the blood no longer moves between the individual beats for reasons of inertia. Atrial tachycardias are generally less dangerous than ventricular tachycardias, since the atria only contribute a small part to functional performance ( cardiac output ). The chamber ( ventricle ) normally contracts much more slowly in atrial tachycardia, since the AV node acts as a frequency filter and not every excitation of the atrium causes the ventricle to be excited. With ventricular tachycardia, however, there is usually a risk of cardiac arrest , as the heart no longer pumps blood.
Another important classification is based on the ventricular frequency. All tachycardias over 120 are to be classified as threatening in adults and all tachycardias over 150 as requiring immediate treatment or monitoring. The time course of a tachycardia is also important: a distinction is made between acute and chronic tachycardia, with the latter being further subdivided into chronic, recurrent or permanent. Finally, the classification of tachycardia with or without heart disease is important in order to assess the risk to the heart. An undamaged heart generally survives tachycardia with fewer problems.
In the case of atrial tachycardia, a narrow QRS complex is found on the ECG , typically ≤ 120 ms (0.12 s) in width. This is important as a differentiation criterion for the more threatening ventricular tachycardia. Atrial tachycardias in combination with bundle branch blocks represent an exception , here a broad QRS complex is found.
They are caused by an abnormal generation of excitation in the area of the atria, which contract at a rate of over 150 per minute. The picture of atrial tachycardia in the ECG is largely similar to that of normal sinus rhythm , ie the T wave and the QRS complex match. If the atrial frequency exceeds 200 / minute, the so-called AV block occurs, because in these frequency ranges it is no longer possible to transfer all atrial excitations to the ventricles. In the ECG this is shown in the form that not all P waves are followed by a QRS complex. A ventricular contraction that is too rapid is thus prevented by the AV node.
Atrial tachycardia that starts suddenly and lasts for minutes or hours and then disappears suddenly is called paroxysmal atrial tachycardia .
The sinus tachycardia is a fast, but regular activity of forecourt and chamber. The ECG can be seen, the sinus tachycardia at a regular sequence of QRS complexes (heart activity of the atrium and ventricle), but the frequency is greater than 100 beats per minute. This can be recognized by the shorter distance between successive QRS complexes. Otherwise the ECG image is normal. Sinus tachycardia often occurs as an accompanying syndrome of other diseases ( fever , electrolyte disturbances , panic attacks, etc.).
In the case of high blood loss, for example due to an accident mechanism, tachycardia usually first occurs with accompanying hypotension . This can be explained by the fact that the reduced volume is compensated for by a higher ejection rate.
AV reentry tachycardia
The AVRT occurs intermittently. It arises from circular excitations between the atrium and ventricle, with the AV node and an innate short circuit (accessory pathway) between the atrium and ventricle being parts of the circular path. It can be asymptomatic or symptomatic. As a rule, patients notice a sudden rapid heartbeat that can also go away spontaneously.
The intravenous antiarrhythmic drug adenosine is the drug of choice for acute therapy . It leads to a short-term AV block III. Degree and thus interrupts the circling excitation. The so-called Valsalva maneuver can also be carried out on an experimental basis, in which pressure is exerted on the chest during an attack, for example by holding one's breath, in order to influence the heartbeat. In the event of hemodynamic instability, electrical cardioversion is performed .
For long-term treatment or for healing, the accessory pathway in the heart is sought out by means of a cardiac catheter examination and is then obliterated with electrical high-frequency application. As an alternative to this process, there is freezing of the tissue in question using cryotechnology . For (long-term) drug therapy, beta blockers or calcium antagonists are available to reduce the conduction speed in the AV node. If they are ineffective and if structural heart diseases are excluded, class I antiarrhythmics such as flecainide or propafenone can also be used. They reduce the speed on the train.
AV-nodal reentry tachycardia
AVNRT is a benign cardiac arrhythmia that is characterized by a rapid and regular heartbeat that begins and ends suddenly. It is caused by a duplication of the AV node .
Tachyarrhythmia in atrial fibrillation
This tachycardia is relatively common. An atrial fibrillation , the chamber is excited to a too rapid heartbeat. Often there is already atrial fibrillation with irregular conduction, which is accelerated to a tachyarrhythmia by additional influences such as fever, stress, dehydration or the like.
Ventricular tachycardia (VT) is a life-threatening tachycardia that originates in the ventricles .
Paroxysmal tachycardia is a paroxysmal increase in cardiac activity to around 150 to 220 beats per minute. A distinction is made here between the atria (supraventricular) and the ventricular (ventricular) tachycardia. Common causes of supraventricular paroxysmal tachycardias include a. the Wolff-Parkinson-White syndrome or changes in the AV node. Means for interrupting supraventricular paroxysmal tachycardias may include drinking cold water, stimulating the carotid sinus, or medication. If the medication is ineffective, the tachycardia must be ended by electrocardioversion (current surge synchronized with the R-wave in the ECG).
Much more dangerous are ventricular paroxysmal tachycardias, which can be recognized in the ECG image by abnormally formed QRS complexes. With these, there is a fundamental risk of life-threatening ventricular fibrillation or cardiogenic shock. Here too, electrocardioversion or an ICD (implantable cardioverter defibrillator) are suitable for ending the tachycardia.
Therapy of tachycardias
The therapy listed here is based on the recommendations of the ERC from 2005.
In addition to the standard procedure (oxygen, access, ECG monitoring, blood pressure, pulse oximetry, identification of reversible causes), the patient's stability is first assessed. Are instability criteria
- Reduced awareness
- Chest pain
- Systolic blood pressure below 90 mmHg
- Signs of heart failure
In a stable patient, there is a separation into narrow and wide complex tachycardias (see above); the limit is 120 ms (0.12 s) width of the QRS complex.
Broad QRS complex
- Regular : The cause is mostly ventricular, therapy with amiodarone.
- Irregular : Most likely cause of atrial fibrillation (AF) with block. Therapy here like narrow complex tachycardia. If polymorphic ECG, possibly torsades de pointes (then magnesium administration ). Another possible cause is Wolff-Parkinson-White syndrome with pre-excitation, then possibly ajmaline .
Narrow QRS complex
- Regular : vagal maneuvers (e.g. Valsalva attempt ). Clinically, it makes sense to let the patient "blow up" a syringe or to put an ice pack on the face / neck. This already breaks many tachycardias. If unsuccessful under ECG control, adenosine as a bolus , if unsuccessful also repeated.
- Irregular : Probable cause of atrial fibrillation, an attempt to control the frequency should be attempted with the help of iv beta blockers, iv digoxin or iv diltiazem . If the onset of the tachycardia was less than 48 hours ago, amiodarone as well . Anticoagulation should be considered here.
- Th. Ziegenfuß: Emergency Medicine , Springer (4th edition), Heidelberg 2007.
- JR Hampton (Ed.): EKG for care professions , Urban & Fischer, Munich 2005.
- Herbert Reindell , Helmut Klepzig: Diseases of the heart and the vessels. In: Ludwig Heilmeyer (ed.): Textbook of internal medicine. Springer-Verlag, Berlin / Göttingen / Heidelberg 1955; 2nd edition, ibid. 1961, pp. 450-598, here: pp. 566 f. ( Paroxysmal atrial and ventricular tachycardia ).
- Krakau, Lapp (ed.): The heart catheter book . 2nd Edition. Thieme, Stuttgart, New York 2005, ISBN 3-13-112412-1 , pp. 572-577 .
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- Nicole Menche: Internal Medicine , Urban & Fischer (8th edition), Munich and Jena 2009