Europace Advance Access originally published online on August 3, 2006
Europace 2006 8(10):901-903; doi:10.1093/europace/eul084
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ELECTROPHYSIOLOGY
Sustained monomorphic ventricular tachycardia associated with unrepaired double-chambered right ventricle
Arrhythmia Unit, Cardiology Department, Hospital Universitario Virgen de las Nieves, Avda. Fuerzas Armadas, 18014 Granada, Spain
Manuscript submitted 16 August 2005. Accepted after revision 20 May 2006.
* Corresponding author. Tel/fax: +34 958 020563. E-mail address: malvarez{at}fundacionhvn.org
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Abstract |
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Double-chambered right ventricle (DCRV) is a congenital anomaly characterized by the division of the ventricular cavity into two chambers separated by an abnormal hypertrophied muscular band or by severe hypertrophy of the muscle wall. Two adult patients with a diagnosis of DCRV presented sustained monomorphic ventricular tachycardia. In both cases, the clinical tachycardia was induced with programmed stimulation. After surgically resecting, the muscular band tachycardia could no longer be induced in the patient who underwent follow-up electrophysiological study. The outcome was favourable; there was no clinical recurrence of ventricular tachycardia in the two patients at 48 and 36 months, respectively.
Key Words: Double-chambered right ventricle, Monomorphic ventricular tachycardia, Cardiac surgery for congenital heart disease
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Introduction |
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Double-chambered right ventricle (DCRV) is an infrequent congenital defect. It is characterized by the division of the RV into two chambers having a pressure gradient between them.1
–3 This division can be due to the presence of one or more abnormal muscular bands or to excessive hypertrophy of the moderator band.
Its clinical expression is variable and, in some cases, causes exertional dyspnoea, angina, or syncope. It is diagnosed by echocardiography or cardiac catheterization.1,3 When DCRV is of an obstructive pathology, the treatment of choice is the resection of the muscular band during childhood or youth, after which the clinical outcome is usually favourable.1,4,5 Nevertheless, some cases have been described where the patient has reached adulthood without undergoing surgical correction.4–6
A complication that we believe has not been described is the association of this congenital defect with sustained ventricular arrhythmias. In this paper, we describe two adults with DCRV who presented sustained monomorphic ventricular tachycardia (SMVT).
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Case 1 |
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A male, 52 years old, found 15 years before to have DCRV after haemodynamic and angiographic studies (pressure gradient 30 mmHg) and a muscular ventricular septal defect (VSD). He experienced palpitations and dizziness on light exertion. Regular wide QRS tachycardia was detected at 186 bpm with left bundle-branch block (LBBB) morphology and normal axis. External electrical cardioversion was performed on two occasions after pharmacological treatment with amiodarone had failed. ECG showed normal sinus rhythm. The pressure gradient assessed by Doppler echocardiography was 60–70 mmHg. Right heart catheterization showed a pressure of 90 mmHg in the proximal area of the RV.
The electrophysiological study (EPS) showed that the AH (116 ms) and HV (54 ms) intervals were normal. Programmed stimulation (cycle length 400 ms, 250/240/210 coupling intervals) induced SMVT with morphology similar to the clinical tachycardia (Figure 1A), which was accompanied by arterial hypotension and dizziness. A His bundle electrogram combined with the RV electrogram led to a diagnosis of suspected bundle-branch re-entry, which was eliminated due to the long post-pacing intervals (90 ms) during entrainment from the RV apex. Pace mapping close to the muscular band insertion showed similar QRS morphology to that of VT (Figures 2 and 3).
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The patient underwent resection of the muscular band via right ventriculotomy, and the VSD was closed (Figure 3). The post-operative progress was good and subsequent echocardiography showed no significant pressure gradient. At EPS, no sustained tachycardia could be induced with up to three ventricular extrastimuli (coupling intervals
180 ms). At 48 months of follow-up, the patient was asymptomatic without recurrence of ventricular tachycardia in the absence of antiarrhythmic treatment.
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Case 2 |
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A male, 62 years old, with an undefined congenital heart defect spontaneously presented an episode of palpitations and presyncope with regular wide QRS tachycardia at 240 bpm with LBBB and left axis morphology, which required external electrical cardioversion. The ECG in sinus rhythm showed right bundle-branch block and signs of RV overload.
The echocardiogram showed DCRV with significant intraventricular obstruction (64 mmHg). The EPS showed normal AH and HV intervals and the absence of VA conduction. Using extrastimuli (cycle length 400 ms, 240/180 coupling intervals), we induced SMVT, poorly tolerated, which was very similar to the clinical VT (Figure 1B).
A non-significant pressure gradient remained after resecting the muscular band via right ventriculotomy. The patient refused another EPS, and post-operative echocardiography showed no significant pressure gradient. At 36 months of follow-up, there have been no recurrences in the absence of antiarrhythmic drugs.
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Discussion |
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A search of the literature revealed no other case of SMVT as a complication in adults with uncorrected DCRV. The criteria used for diagnosing DCRV include (1) systolic pressure gradient between two RV chambers (sinus and infundibulum) identified via angiographic and haemodynamic studies and echocardiography, (2) characteristic ventriculography showing the obstructive muscular band and an anatomically normal outflow tract, and (3) direct observation of the anomaly during surgical repair.5
,7 The most frequent electrocardiographic abnormality is the presence of right bundle-branch block, although the ECG may be normal.7
The diagnosis of ventricular tachycardia via surface ECG is indicated by the duration of the QRS complex (160 ms) in the presence of LBBB, a time of >100 ms from the beginning of the R-wave to the nadir of the S-wave in leads V4–V5 and AV dissociation (confirmed by the EPS).8 In the two cases described, clinical tachycardia was the only induced tachycardia that showed criteria compatible with a re-entry mechanism, i.e. reproducible VT initiation via extrastimuli, reset and entrainment with fusion, and termination by rapid pacing.9
Ventricular tachycardia with LBBB morphology was diagnosed, and tachycardias of supraventricular origin were excluded. The presence of heart disease and the QRS axis during VT excludes idiopathic right outflow tract VT, and the absence of a history of myocardial infarction and corrective surgery for congenital heart disease excludes two more possibilities. Arrhythmogenic RV dysplasia clearly differs from DCRV on the surface ECG (epsilon wave), on ventriculography the RV has the appearance of ‘stacks of coins’ and there is an absence of an intraventricular pressure gradient.10,11 Bundle-branch re-entry is diagnosed when the His bundle electrogram is combined with a RV electrogram, detecting tachycardia with an HV interval similar to that during sinus rhythm. Nevertheless, one of the diagnostic criteria was not fulfilled, i.e. a post-pacing interval from the RV apex similar to the tachycardia cycle.12
Two adult patients with DCRV are described in the literature, who presented unsustained ventricular tachycardia (20 beats in one case); however, in these cases, the onset of arrhythmia took place after corrective surgery in the absence of reported ventricular arrhythmias prior to surgery, although one of the patients had presented recurrent syncope.6
The structural anomalies involved in muscular band hypertrophy (substitution of myocardium by fibrotic tissue, disarray, heterogeneously stained myofilaments)13 could favour the appearance of ventricular arrhythmias at this (muscular band) level.14 The lack of re-induction after surgery and the absence of recurrence in the medium term equally suggest the involvement of the muscular band in the pathogenesis of ventricular tachycardia,15 but we cannot discard the possibility that pressure overload in the proximal chamber also plays a role.
These considerations are important because once the RV anomaly is eliminated, the risk of arrhythmic events appears to be low. Thus, when the surgical outcome is good and, as usual, ventricle function is normal, it is unnecessary to use other therapies (ablation, drugs, or defibrillator which themselves are not free of complications) especially when it has been confirmed that inducible arrhythmia is absent.
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References |
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