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Sumario Vol. 42 - Nº 3 Julio - Septiembre 2013

Myotonic Dystrophy and Bundle Branch
Reentry Ventricular Tachycardia

José Luis Velarde Mariscal*, Aldo Ruben Arévalo**,
Ricardo Alberto Martellotto*

*Unidad de Arritmias, Electrofisiología y Marcapasos.
**Instituto de Cardiología. Hospital Italiano, Córdoba.
Sarmiento 1595 – Bº General Paz. (5000) Córdoba, Argentina
E mail

Recibido 12-SET-12 – ACEPTADO después de revisión el 17-ENERO-2013.
The authors declare not having a conflict of interest.
Rev Fed Arg Cardiol. 2013; 42(3): 205-208


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RESUMEN

La distrofia miotónica es el tipo de distrofia muscular más frecuente en adultos y su manifestación clínica más llamativa es la debilidad distal y la miotonía. La fibrosis miocárdica y la degeneración del sistema de conducción His-Purkinje son responsables a menudo de arritmias cardíacas y muerte súbita. En ocasiones la taquicardia ventricular sostenida es la manifestación inicial. Se presenta el caso clínico de una mujer cuya primera manifestación fue una taquicardia ventricular (TV) con compromiso hemodinámico. Realizado el diagnóstico de una TV por reentrada rama-rama se procedió a realizar una ablación de la rama derecha que controló su taquicardia. Ante el hallazgo de alteraciones en el sistema de conducción se implantó un marcapaso bicameral con favorable evolución clínica en el seguimiento a 18 meses.

Palabras clave: Aneurisma. Aorta torácica. Tratamiento híbrido. Tratamiento endovascular.
SUMMARY

Myotonic dystrophy is the most common type of muscular dystrophy in adults. Distal weakness and myotonia are its most striking clinical symptoms. Myocardial fibrosis and degeneration of the His-Purkinje conduction system are often responsible for cardiac arrhythmias and sudden death. Sometimes, sustained ventricular tachycardia is the initial manifestation. We report the case of a woman whose first manifestation was ventricular tachycardia (VT) with hemodynamic compromise. After the diagnosis of bundle branch reentry VT, we proceeded to the ablation of the right branch, which successfully controlled the tachycardia. The finding of abnormalities in the conduction system led to implantation of a dual chamber pacemaker, with favorably clinical outcome at 18 months follow-up.

Key words: Myotonic dystrophy. Bundle branch reentry ventricular tachycardia. Ablation.

 

 

INTRODUCTION
Myotonic dystrophia (Steiner’s disease) is the type of muscular dystrophy most frequent in adults, with a prevalence of 1 in 8,000. This is a multisystemic disorder that is inherited in an autosomal dominant manner with almost complete penetrance and with panmuscular involvement –skeletal muscle, cardiac muscle and smooth muscle-, although the most remarkable clinical manifestations are distal weakness and the myotony [1-3].

The adult’s form starts between 15 and 45 years of age, and there is a congenital form with symptoms since birth.

Cardiovascular manifestations –initially asymptomatic- bring the consequence of myocardial fibrosis and degeneration of the His-Purkinje conduction system. Electrocardiographic alterations (prolonged PR, branch blocks, etc.) and cardiac arrhythmias may be responsible for sudden cardiac death, often described in these patients [4,5].

On some occasions, sustained ventricular tachycardia (VT) is the way of presentation and the most frequent electrophysiological mechanism is bundle branch reentry [6].

 

CLINICAL CASE
Female, 41-year-old patient, who is admitted by palpitations with hypotension and hemodynamic affection. The electrocardiogram showed tachycardia with wide QRS with left bundle branch block image, with ventricular rate of 210 bpm, which was reversed by electrical cardioversion (Figure 1).

Figure 1. Twelve-lead ECG at admittance. Sustained monomorphic ventricular tachycardia.

 

She presents history of diagnosis of myotonic dystrophy, type II diabetes and episodes of limited palpitations. Between her family history, a sister (25 years old) and a first cousin (18 years old) stand out, both with sudden cardiac death.

The cardiovascular (post-cardioversion) test did not show relevant data, with an electrocardiogram that shows PR of 230 ms and QRS with image of intraventricular conduction disorder. The echocardiogram shows preserved cardiac diameters, with normal ventricular function and Doppler with mild mitral valve insufficiency.

Due to her family history of sudden cardiac death, diabetes and ventricular arrhythmia, she was evaluated by coronary angiography, which showed normal coronary arteries.

Subsequently, an interconsultation was made with our group and an electrophysiology study was conducted that showed AH interval of 85 ms; HV 100 ms and QRS 128 ms (Figure 2). Atrial pacing shows normal sinus function, with early Wenckebach point without induction of arrhythmias. Ventricular pacing with two extrastimuli with short cycle-long cycle sequence, could induce sustained ventricular tachycardia with equal morphology to that of clinical tachycardia (Figure 3). Mapping and electrophysiological maneuvers showed VT by bundle branch reentry (criteria used: QRS morphology by branch block, AV dissociation during tachycardia, prolonged HV during sinus rhythm, presence of stable His electrogram during tachycardia with interval equal or greater to sinus rhythm, spontaneous changes in His cycle length preceding changes in tachycardia cycle, interruption of tachycardia after right bundle branch ablation)[6].

Figure 2. Twelve-lead surface and intracavitary recording in sinus rhythm. The recording of the right branch (RB) and the His (His) bundle is observed, with HV of 100 ms.

 

Figure 3. Twelve-lead surface and intracavitary recording of the right ventricle (RV) and the His bundle (His) during bundle branch sustained ventricular tachycardia of the same morphology as clinical tachycardia. QRS morphology is observed with branch block, AV dissociation, presence of stable His electrogram during tachycardia with interval greater than sinus rhythm (105 ms).

 

With this diagnosis, right bundle branch ablation is decided. With ablation catheter with 4-mm type, an application of radiofrequency (65º-70 W) was made in the right branch of the His bundle with interruption of tachycardia and the presence of right bundle branch block in the electrocardiogram (Figure 4). Subsequently, with a stimulation protocol with up to 3 extrastimuli and under isoproterenol (IV) infusion, it was not possible to reinduce the arrhythmia.

RV:  Right ventricular electrograms. RF: Proximal (p) and distal (d) ablation catheter electrograms.

Figure 4. Twelve-lead surface and intracavitary recording during the application of radiofrequency with ventricular tachycardia interruption and right bundle branch block in sinus rhythm.

 

Before the findings of the conduction system alterations (prolonged HV, branch block, early Wenckebach), a dual-chamber pacemaker was implanted.

In an 18-month follow-up, the patient remained asymptomatic and 24 h Holter does not show significant arrhythmias.

 

DISCUSSION
In myotonic dystrophy, the heart is frequently affected, although most patients do not present significant cardiac symptoms.

Between the cardiac manifestations, the most frequent ones are electrophysiological alterations: conduction disorders, AV blocks, supraventricular and ventricular arrhythmias [4-5]. In these patients, even a third of them may die suddenly and the mechanisms of it are not clear.

Sudden cardiac death may occur as a consequence of myocardial fibrosis and degeneration of the conduction system. A percentage die by neuromuscular respiratory failure and others due to asystole after AV block or ventricular tachyarrhythmia (VT and/or ventricular fibrillation) [5].

In the paper by Groh W.J. et al, the presence of electrocardiographic alterations –non-sinus rhythm, prolonged PR >240 ms, QRS duration >120 ms or AV block of 2nd or 3rd degree- is an independent predictor with moderate sensibility for sudden cardiac death [5].

In our case, the patient showed basal electrocardiographic alterations (prolonged PR – branch block), with no respiratory manifestation, some isolated palpitations without clinical significance, and the first manifestation was VT without hemodynamic involvement.

Within arrhythmias, VT has been described as of high risk and the most widely observed electrophysiological mechanism is bundle branch reentry, although other mechanisms have also been documented [6-7]. The response to antiarrhythmic pharmacological treatment is poor in these patients.

Merino JL et al, presented a series of 6 patients with myotonic dystrophia, where VT by bundle branch reentry was present in all of them [6]. In our patient, the morphology of tachycardia in the electrocardiogram, joined to the base pathology, led us to consider this type of VT by bundle branch reentry and the electrophysiology study confirmed this supposition.

Catheter ablation of bundle branch VT was described many years ago as an efficient and safe therapeutic option to treat this type of arrhythmia. In the follow-up of the patients of Merino JL, the ablation controlled and removed sustained arrhythmias in the follow-up. In our case, the ablation of the right branch showed the removal of tachycardia and in the evolution there were no more arrhythmias presenting.

Due to the unpredictable progression of electrical disorders in these patients, mainly those with family history of sudden cardiac deaths, electrocardiographic alterations and/or complex ventricular arrhythmia, the implant of pacemaker or cardioverter defibrillator (ICD) is proposed to prevent sudden cardiac death, in spite of a successful ablation [5-6,8-9].

Some authors point out that the treatment by ablation and later pacemaker implant, is a good option if the arrhythmia is no longer inducible [6].

The use of pacemaker in patients with myotonic dystrophy has been reflected in the American guidelines of cardiology (AHA-ACC-HRS) were an implant is advised in selected cases[9]. In the registry of Groh WJ et al, from 406 patients, 10% had a pacemaker implanted, but in spite of this a reduction in the incidence of sudden cardiac death was not observed [5].

Others advocate that patients with clinically symptomatic ventricular arrhythmias should have an ICD implanted as prevention, since up to 6.5% die suddenly in spite of successful ablation [5,10]. In spite of the effectiveness of ICD to prevent sudden cardiac death, its indication remains controversial.

In our patient, ablation could control tachycardia and due to her family history (two first degree relatives with sudden cardiac death) and the presence of significant alterations in the conduction system (HV: 100 ms, branch block, etc.), the possibility of ICD implant was discussed, although by problems with her health insurance this was not possible and permanent dual-chamber pacemaker was implanted.

 

REFERENCES
  1. Church SC. The heart in myotonia atrophica. Arch Intern Med 1967; 119: 176-81
  2. Perloff JK, Stevenson WG, Roberts NK, et al. Cardiac involvement in myoyonic muscular dystrophy (Steinert’s disease): a prospective study of 25 patients. Am J Cardiol 1984; 54: 1074-81
  3. Harper PS, van Engelen BG, Eymard B, et al. 99th European Neuromuscular Centre International Workshop: myotonic dystrophy: present management, future therapy. Neuromuscul Disord 2002; 12: 596-9.
  4. Hiromasa S, Ikeda T, Kubota K, et al. Myotonic dystrophy : Ambulatory electrocardiograma, electrophysiologic, and echocardiographic evaluation. Am Heart J. 1987; 113: 482-8.
  5. Groh WJ, Groh MR, Saha C, et al. Electrocardiographic abnormalities and sudden death in myotonic dystrophy type 1. N Engl J Med 2008; 358: 2688-97.
  6. Merino JL, Carmona JR, Fernández-Lozano I, et al. Mechanisms of sustained ventricular tachycardia in myotonic dystrophy. Implications of catheter ablation. Circulation 1998; 98: 541-6.
  7. Nageh MF. Recurrent fascicular ventricular tachycardia in myotonic dystrophy. Europace 2006; 8 (5): 336-7.
  8. Lazarus A, Varin J, Babuty D, Anselme F, et al. Long-term follow-up of arrhythmias in patients with myotonic dystrophy treated by pacing: a multicenter diagnostic pacemaker study. J Am Coll Cardiol 2002; 40: 1645-52.
  9. Gregoratos G, Abrams J, Epstein AE, et al. ACC / AHA / NASPE 2002 guideline update for implantation of cardiac pacemakers and antiarrhythmia devices: summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation 2002; 106: 2145-61.
  10. Saliba WI, Natale A. Ventricular tachycardia syndromes. Med Clin North Am 2001; 85: 267-303.

Publication: September 2013

 
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