(SVT; PSVT; WPW)
In the case of supraventricular tachycardias reentrant (SVT) are conductor tracks, in which the electrical excitation circuits, located above the bifurcation of the His bundle. In some cases, dyspnea or chest discomfort occur. Patients complain of sudden episodes of palpitations with abrupt onset and abrupt end. The diagnosis results from the clinic and the ECG. By vagus stimulation the tachycardia can be terminated. If this measure is not successful, the treatment consists in narrow QRS complexes and with wide QRS complexes, due to a supraventricular reentrant tachycardia with abnormal conduction at the AV nodal conduction is necessary from the i.v. Administration of adenosine or calcium antagonists of the Nichtdihydropyridintyp. In another broad QRS rhythms therapy consists procainamide or amiodarone. Synchronized cardioversion is the treatment of choice for all forms.
In the case of supraventricular tachycardias reentrant (SVT) are conductor tracks, in which the electrical excitation circuits, located above the bifurcation of the His bundle. In some cases, dyspnea or chest discomfort occur. Patients complain of sudden episodes of palpitations with abrupt onset and abrupt end. The diagnosis results from the clinic and the ECG. By vagus stimulation the tachycardia can be terminated. If this measure is not successful, the treatment consists in narrow QRS complexes and with wide QRS complexes, due to a supraventricular reentrant tachycardia with abnormal conduction at the AV nodal conduction is necessary from the i.v. Administration of adenosine or calcium antagonists of the Nichtdihydropyridintyp. In another broad QRS rhythms therapy consists procainamide or amiodarone. Synchronized cardioversion is the treatment of choice for all forms. Pathophysiology The reentry path (Typical reentrant mechanism) in supraventricular tachycardia within the Atrioventricular (AV) node (about 50%) zusätzlichger bypass tract (40%) atria or sinoatrial (SA) node (10%) The AV nodal reentrant tachycardia is most often found in otherwise healthy people. It is most commonly caused by supraventricular arrhythmias. In the reentrant tachycardia via an accessory pathway, the excitation over a range of conduction tissue is passed, the partially or completely, the normal AV conduction bypasses (bypass) tract. Most commonly, these paths run directly from the atria to the ventricles, less frequently from the atrium to a portion of the conduction system or from a part of the conduction system to the ventricle. It can be caused by supraventricular or ventricular premature beats. Wolff-Parkinson-White syndrome (WPW) WPW syndrome (Präexzitationssyndrom) is the most common type of SVT via an accessory pathway and is found in 1-3 / 1000 people. For the most part it is a WPW syndrome of unknown cause. In patients with hypertrophic or other form of cardiomyopathy, a transposition of the great vessels or Epstein’s anomaly, the WPW syndrome, however, is more common. There are two main forms of WPW syndrome: Classic Hidden In the classical (or overt) WPW syndrome runs the anterograde conduction during sinus rhythm both an accessory pathway or via the normal conduction system. The faster accessory pathway depolarized some areas of the ventricle earlier. The ECG shows a short PR interval and QRS complex to the preceding sluggish “upstroke” (Deltawelle- classic Wolff-Parkinson-White syndrome (WPW syndrome) :). Classical Wolff-Parkinson-White syndrome (WPW syndrome): in leads I, II, III, and V3 to V6 show classical features of the WPW syndrome, a short PR interval and a delta wave during sinus rhythm , By the delta wave, the QRS duration increased to> 0.12 seconds, although the overall configuration except for the delta wave may appear normal. Depending on the orientation of the delta wave, the image of a pseudo infarction may appear with pathological Q-wave. Since the early depolarized areas of the ventricle re-polarize too early, the vector of the T wave may vary. In a hidden WPW syndrome energization via the accessory pathway is not conducted in an anterograde direction; Therefore, the above ECG changes do not show. However, the excitement runs in a retrograde direction and can thus be involved in a reentrant tachycardia. In most forms of reentrant tachycardias (orthodromic tachycardia so-called reentry.), The circulating excitation to activate the ventricles via the normal AV conduction path, and returns on an accessory AV connection to the atrium. Therefore, the QRS complex is narrow in this case (except in addition, a branch block exists) and without delta wave. The orthodromic reentrant tachycardia generally shows a short RP interval with retrograde P-wave in the ST segment. Rarely, the reentrant circuit in the opposite direction rotates. Here, the circulating excitation extends from the atrium to the ventricle via an accessory AV connection and returns retrogradely via the normal AV conduction system from the ventricle to the atrium back (so-called. Antidromic reentry tachycardia). Here, wide QRS complexes appear as the ventricles are not normally activated. Quite often there are patients who have two accessory AV connections. Here, the reentrant tachycardia can be passed in a retrograde direction over an accessory connection in the anterograde direction over another. The tachycardia in a WPW syndrome can begin as atrial fibrillation (AF) or go to a VHF, a condition that can be very dangerous for patients. In a WPW syndrome with enlarged atria due to hypertrophic cardiomyopathy, or other form of cardiomyopathy is more of a VHF can develop. Symptoms and signs In most patients show a WPW syndrome already in young or middle-aged. Typically, patients complain of tachycardia episodes that begin suddenly and just as suddenly end again, and palpitations, which are perceived as quickly and regularly. Often symptoms indicate a hemodynamic problem with dyspnea, chest discomfort and dizziness. The attacks may last only a few seconds or last for several hours (rarely> 12 h). Infants suffer attacks of dyspnea, act lethargic, are not hungry or show rapid precordial pulsations. In a sustained tachycardia of heart failure may develop. The study findings are in addition to a heart rate of 160-240 beats / min generally unremarkable. Diagnostic ECG Diagnosis of supraventricular tachycardia arises from the ECG showing a high tachycardia, regular heart rate. If available, previous ECG findings are examined for signs of overt WPW syndrome out. The P-waves vary. In most cases, an AV nodal reentrant circuit, the retrograde P-waves in the terminal part of the QRS complex find (and often generate a pseudo-R ‘in lead V1). About a third appears just after the QRS complex and only a few in front of the QRS complex. When orthodromic reentrant tachycardia of WPW syndrome, the P-waves always follow after the QRS complex. The QRS complexes are narrow, except at the same time present bundle branch block, antidromic tachycardia or tachycardia due to two accessory pathways. Tachycardia with wide QRS complexes must be distinguished from ventricular tachycardia (see table: Indications for implantable cardioverter defibrillators for ventricular tachycardia and ventricular fibrillation, Classic Wolff-Parkinson-White syndrome (WPW) and tachycardia with a narrow QRS complex:. orthodromic reentrant tachycardia with accessory pathway in Wolff-Parkinson-White syndrome Tips) and risks Although most supraventricular tachycardia, a narrow QRS complex is present, some have also distinguished a wide QRS complex and have ventricular tachycardias become. Tachycardia with narrow QRS complex: orthodromic reentrant tachycardia with accessory pathway in Wolff-Parkinson-White syndrome. The activation takes place in the following order: AV node, His-Purkinje system, ventricle, accessory pathway, atria. The P-wave follows shortly after the QRS complex; it’s a short RPTachykardie (PR> RP). Treatment vagus stimulation adenosine In narrow QRS complex, verapamil or diltiazem Frequent recurrence radiofrequency ablation Many tachycardia episodes end spontaneously before the start of a therapeutic intervention. A vagal stimulation (z. B. Valsalva maneuver, unilateral carotid sinus massage, immersing the face in ice-cold water or drinking ice water) can, v. a. if it is carried out at an early stage, the end tachycardia. Some patients apply these techniques at home. AV node blocker used when these maneuvers are not effective and the QRS complexes narrow (and therefore have a orthodromic reconciliation back). If the line is in the AV node blocked for one beat, it will disengage the reentry circle. Adenosine is the treatment of choice, and is injected i.v. in a dose of 6 mg (0.05-0.1 mg / kg in children) in the bolus. Then, 20 ml of physiological saline are subsequently injected. If, when the dosage no effect, hereinafter twice each with 12 mg at intervals of five minutes administered. Under adenosine occurs in some cases a disturbing for patients and physician brief cardiac arrest about two to three seconds. As alternatives to adenosine increase verapamil are iv 5 mg or diltiazem 0.25-0.35 mg / kg i.v. In a tachycardia with regular wide QRS complexes, which is known that there is a antidromic reentrant tachycardia without the participation of two accessory pathways (finding must be a history secured, two accessory pathways can not be determined in the acute stage), may a AV nodal inhibitors be effective. However, the mechanism of tachycardia unknown, ventricular tachycardia can not be excluded. Here AV nodal inhibitors should be avoided because they can contribute to the worsening of ventricular tachycardia. In such cases (or in cases where other drugs are ineffective), the administration of procainamide is i.v. or amiodarone. Alternatively, is the synchronized cardioversion with 50 joules (in children 0.5-2 Joules / kg) a quick and safe way to terminate the tachycardia, and may be preferable to more toxic drugs. Frequent or perceived as annoying episodes of AV nodal reentrant tachycardia can be terminated by a long-term therapy with antiarrhythmic drugs or by a transvenous RF catheter ablation. In general, the ablation is recommended. However, if ablation is not feasible, a medikametöse prophylaxis usually starts with digitalis. Subsequently, as necessary, continue with beta-blockers, calcium antagonists of the Nichtdihydropyridintyp or a combination of both. Finally, the adjustment is made on one or more antiarrhythmic agents of Class Ia, Ic or III. However postadoleszente, patients with overt WPW syndrome (where AF is more likely) not only digoxin or a non-dihydropyridines calcium channel blocker obtained (atrial fibrillation and Wolff-Parkinson-White syndrome (WPW)). Summary The symptoms begin and end suddenly. The QRS complexes are narrow, fast and regular, as a rule, but it is also wide QRS complexes occur, which then have to be distinguished from ventricular tachycardia. Vagus stimulation (z. B. Valsalva maneuver) is sometimes hiflreich. In tachycardia with narrow QRS complexes AV nodal inhibitors should be used. Adenosine is the first choice; if it is not effective, verapamil or diltiazem alternatives. In tachycardia with wide QRS complex AV nodal inhibitors should be avoided; should instead synchronized cardioversion or procainamide or amiodarone are applied.