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Sumario Vol. 42 - Nº 1 Enero - Marzo 2013

Inapparent accessory pathway and paroxysmal supraventricular tachycardia induced by exercise.

Oscar A Pellizon, Karina Ramos.

Centro de Arritmias Cardíacas.
Hospital Universitario del Centenario.
Pasco 1315 2° A.
Rosario. Santa Fe. Argentina.
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Recibido 23-DIC-2013 – ACEPTADO después de revisión el 30-ENERO-2013.

The authors declare not having a conflict of interest.

Rev Fed Arg Cardiol. 2013; 42(1): 63-64


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The induction by exercise of paroxysmal supraventricular tachycardia is infrequent (1-2%) [1,2]. We present a patient in whom stress test showed the presence of inapparent accessory pathway that participated in a retrograde way in an orthodromic atrioventricular reentrant tachycardia.

A 21-year-old male patient underwent a stress test as part of a cardiovascular evaluation for the practice of sports. He did not have any personal or family history of heart disease. All the tests, including the electrocardiogram (ECG) in rest were normal (Figure 1A). The stress test was made with a modified Bruce protocol. During the recovery (Figure 1B) premature atrial contraction can be seen, as well as blocked P’ (dashed arrow) representing atrial echo. After this beat, a preexcited complex is evident (white arrow). Next, a beat without preexcitation and another premature atrial contraction (solid arrow) that triggers an orthodromic atrioventricular reentrant tachycardia with aberration in the right branch (cycle length 240 milliseconds). He presented 2 episodes of 30 and 6 seconds respectively. The preexcited QRS complex pattern is consistent with left lateral atrioventricular accessory pathway [3].

 

This case shows how the stresstest can make evident an inapparent accessory pathway. This situation in conditions of rest could be due to: 1) the presence of accelerated atrioventricular node (AVN) conduction; 2) a prolonged time of intraatrial conduction, which would foster the conduction toward the normal atrioventricular conduction system (AV-His-Purkinje node) and not toward the accessory pathway, in this case located distally (left lateral area) or 3) that the accessory pathway has a prolonged refractory period.

In our case, the exercise produced a hyperadrenergic state that caused frequent premature atrial contractions. The second beat in Figure 1B is a premature atrial contraction that produces an atrial echo that is blocked and does not conduct to the ventricles. The pause generated by the blocked premature atrial contraction allows the anterograde conduction through the left lateral accessory pathway. The fifth beat induces an orthodromic atrioventricular reentrant tachycardia with functional block in the right branch, thus configuring a Wolff-Parkinson-White syndrome.

This case indicates us that the thorough analysis of a stress test as part of a cardiovascular evaluation may make evident an inapparent ventricular preexcitation and the substrate for a supraventricular tachyarrhythmia.

 

REFERENCES.

  1. Lee KW, Nitish Badhwar N, Scheinman MM. Supraventricular Tachycardia - Part I. Curr Probl Cardiol 2008; 33: 467-546.
  2. Maurer MS, Shefrin EA, Fleg JL. Prevalence and prognostic significance of exercise-induced supraventricular tachycardia in apparently healthy volunteers. Am J Cardiol 1995; 75: 788-792.
  3. Arruda MS, McClelland JH, Wang X, et al. Development and validation of an ECG algorithm for identifying accessory pathway ablation site in Wolff-Parkinson-White syndrome. J Cardiovasc Electrophysiol 1998; 9: 2-12.

 

Publication: March 2013

 
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