Paroxysmal supraventricular tachycardia I47

A variant of atrioventricular reentry tachycardia, the WPW syndrome, was first described in 1930 by Wolff, Parkinson and White and named after them (Greten 2010).

AV nodal reentry tachycardia (AVNRT) and atrioventricular reentry tachycardia (AVRT) used to be grouped under the generic term "paroxysmal supraventricular tachycardia (PSVT)". Nowadays, a distinction is made between both forms of tachycardia.

Atrioventricular reentry tachycardia (AVRT) is a form of regular tachycardia in predominantly healthy individuals with a frequency of 120 - 250 beats / min. caused by accessory pathways (Pinger 2019).

In AV reentry tachycardia (AVRT) there are accessory pathways.

These pathways are classified accordingly:

• According to its localization in:
  • left- right
  • anterior
  • superior
  • posterior
  • anterior
  • paraseptal
• according to its conduction characteristics in:
  • the rarely occurring decremental path (here the line speed decreases with increasing frequency, e.g. in the Mahaim bundle)
  • the frequently occurring non-decremental path
• according to its conduction direction:
  • antegrad
  • retrograde
  • bidirectional (Pinger 2019)

The orbits are referred to as:

• Kent bundle (atrioventricular)
• Paladino bundle (nodoventricular)
• Mahaim- bundle (atriofascicular)
• James- bundle (atrionodal / atrio- His)
• fasciculoventricular (Pinger 2019)

With the AVRT one differentiates between 4 variants:

• Wolff-Parkinson-White Syndrome (WPW Syndrome)
• Mahaim fiber
• Hidden accessory pathways (AL): These occur in about 50% of patients with AVRT. In this case there is only retrograde conduction. The accessory pathways thus lead exclusively from the main chamber to the atrium. The frequency lies between 180 - 200 beats / min.
• Permanent junctional reentry tachycardia (PJRT): This form of AVRT occurs only rarely. It is an accessory pathway with exclusively retrograde, retarding and slow conduction characteristics. Since the tachycardia frequency is lower and more permanent, patients often do not even notice the disturbance.

The ECG contains:

• narrow QRS complexes
• long R- P- interval (typical is R- P > P- R)
• mostly negative P- waves in II, III, aVF

PJRT can lead to tachycardia-induced cardiomyopathy. Differential diagnosis: Long Gonan Levine Syndrome (LGL- Syndrome).

In LGL- Syndrome the PQ- time is < 0,12 sec, there is no delta wave. The LGL- Syndrome has no disease value, it only represents an ECG variant.

AVRT is the second most common form of paroxysmal supraventricular tachycardia.

The incidence is about 1-3 / 1,000 (Voss 2016).

It is a congenital disorder.

The WPW syndrome can occur at any age, the first manifestation is found in 50% before the age of 20 (Pinger 2019).

Associated cardiac malformations:

In WPW syndrome, a variant of AVRT, about 7% to 20% of patients have additional cardiac defects, in particular:

• Mitral valve prolapse
• hypertrophic obstructive cardiomyopathy
• Atrial septal defect
• Ventricular septal defect
• M. Ebstein (Pinger 2019)

AVRT is a primarily electrical heart disease in which an accessory atrioventricular conduction structure is present in the atria and ventricles (Herold 2020).

The excitation runs from the atrium antegrad over the AV node, the His bundle, the Tawara legs and the Purkinje fibers to the ventricles and then retrogradely over the accessory pathway back to the atrium (Kasper 2015).

The conduction can be antegrade only, retrograde only or in both directions (Pinger 2019)

The onset of AVRT is abrupt in the majority of cases and is triggered by an extrasystole . The tachycardia is usually terminated by blockade of the AV node.

(Pinger 2019)

Symptoms of AVRT may include:

• Palpitations
• seizure-like onset of palpitations
• Dyspnea
• Anxiety
• polyuria
• in rare cases, occurrence of syncope

(Voss 2016)

Rest ECG

In about 20 % - 30 % the accessory pathway conducts only retrograde (ventricle - atrium). In these cases there are no changes in the surface ECG (so-called concealed conduction).

(Pinger 2019)

Otherwise, the following changes may occur in an acute attack:

• Tachycardia with a frequency of 120 - 250 beats / min
• Narrow QRS complex (with antegrade atrial ventricular conduction via the conduction system and with retrograde atrial ventricular excitation via the accessory pathway)
• wide QRS complex up to the right or left leg block (in case of aberrant line with antegrade direction over the accessory path)
• P- Waves:
  • are in the range of the ST range
  • are negative in II, III and aVF (for an orthodromic AVRT = postero-septic accessory pathway)
  • negative P- waves precede the QRS complex (in the antidromic AVRT)

(Kasper 2015 / Herold 2020 / Pinger 2019)

• prolonged repolarization
• shortened PQ- time
• Delta-wave as a sign of preexcitation (The occurrence of a delta-wave is only found when the excitation passes through both the AV node and the accessory path. At about 30% the accessory path can only conduct retrograde, in this case the delta wave is missing [Lam 2018])

(ping 2019)

A distinction is made between acute therapy and recurrence prophylaxis.

Acute therapy: Because of the danger of ventricular fibrillation, treatment should be started immediately after diagnosis (Pinger 2019). All common medications which are normally given in tachycardic atrial fibrillation are contraindicated in AVRT because they can further increase the ventricular frequency and thus further promote the development of atrial fibrillation (Pinger 2019).

Recommendations of the ACC / AHC / HRS 2015:

• Indication class I:
  • Valsalva trial
  • Carotid pressure test
  • without atrial fibrillation: Adenosine (is effective in about 90 % - 95 %. Recommended dosage: 6 mg - 18 mg rapid i. v. [Michels 2017])
  • with atrial fibrillation: Ajmalin 0,5 mg - 1mg / kg KG slow i. v. (Michels 2017)
  • in case of haemodynamic instability, electric cardioversion should be performed
  • cardioversion if the drug therapy is not effective
• Indication class II a for orthodromic AVRT without preexcitation at rest ECG:
  • Diltiazem: Recommended dosage: 0.25 mg / kg i. v. over 2 min (Lam 2018); contraindicated in existing atrial fibrillation (Michels 2017)
  • Verapamil: Recommended dosage: 5 mg - 10 mg i. v. (Trappe 2001); shortens the refractory time of accessory pathways.
  • Betablocker: recommended dosage: Metoprolol 5 mg - 15 mg i. v. (Trappe 2001)
• - Indication class II b for orthodromic AVRT with preexcitation at rest ECG:
  • Diltiazem: Recommended dosage: 0.25 mg / kg i. v. over 2 min (Lam 2018); contraindicated in existing atrial fibrillation (Michels 2017)
  • Verapamil: Recommended dosage: 5 mg - 10 mg i. v. (Trappe 2001); shortens the refractory time of accessory pathways.
  • Betablocker: Recommended dosage: Metoprolol 5 mg - 15 mg i. v. (Trappe 2001) (Pinger 2019)

Prevention of recurrence: Ablation is the treatment of choice for patients who have had an AVRT. The success rate is 95% - 98.5%, the recurrence rate is 5% (Pinger 2019).

If the patient refuses a catheter ablation, it can be used on a long-term basis in the absence of preexcitation:

• beta-blockers such as metoprolol, recommended dosage: 100 mg - 200 mg / day
• Calcium channel blockers such as Verapamil, recommended dosage: 80 mg - 120 mg / day (Schmidt 2007)

If a preexcitation is detectable in the ECG, Ic- Antiarrhythmics (Lam 2018) such as:

• Flecainide: Recommended dosage: 2 x 50 mg - 100 mg/day
• Propafenone; recommended dosage: 2 - 3 x 200 mg/day (Schmidt 2007)

In patients with preexcitation and tachycardia there is a risk of

• Syncopes
• hemodynamic collapse
• Occurrence of atrial fibrillation
• Occurrence of ventricular fibrillation
• sudden cardiac death (occurs in 2 in 1,000 adults, more often in children (Kasper 2015, Pinger 2019)

In the case of hidden accessory pathways (see "Classification" below), there is no increased risk of ventricular fibrillation or sudden cardiac death due to the lack of antegrade conduction via the accessory pathways.

The prognosis is very good for patients with no inducibility of tachycardia, who are otherwise heart-healthy and asymptomatic (applies to approx. 65% of patients). About 3.4% of them will become symptomatic within the next 3 years and should then be treated accordingly (Pinger 2019).

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