Download How To Differentiate Right Ventricular Outflow Tract Tachycardia

How To Differentiate Right Ventricular Outflow Tract
Tachycardia from Arrhythmogenic Right Ventricular
Cardiomyopathy?
C. WOLPERT, C. ECHTERNACH, C. VELTMANN, R. SCHIMPF, M. BORGGREFE
Introduction
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a disease characterised by partial replacement of myocardial tissue by fibrofatty tissue.
Ventricular tachycardia may originate from the diseased areas and cause
haemodynamically non-tolerated ventricular tachycardia, syncope, or sudden death already in young patients.
Time of first diagnosis is usually before the age of 40 and not infrequently already in adolescence. The aetiology of ARVC varies and there are different hypotheses as to how ARVC develops [1, 2]. Among affected patients,
there is a predominance of males and early reports suggested that in some
cases the disease may be familial. Moreover, a number of different gene
mutations in desmosomes have been identified, such as mutations in
cytoskeletal proteins, plakoglobin, and desmoplakin, and both autosomaldominant and autosomal-recessive modes of inheritance have been reported. In some patients disease is also manifested in the left ventricle [3, 4].
Right ventricular outflow tract (RVOT) tachycardia is a benign condition.
In the absence of structural heart disease, it is considered to be primary electrical defect that results in ventricular extra beats, salvos, or sustained tachycardias mainly from the right ventricular outflow tract, but also infrequently
from other regions in the right ventricle, above the pulmonary valve or the
sinus valsalva. A variety of mechanisms have been suggested, including
cAMP-triggered activity through late after-depolarisation. RVOT tachycardia
is also mainly observed in young patients, predominantly females, and often
1st Department of Medicine-Cardiology, University Hospital Mannheim, Faculty of
Clinical Medicine of the University of Heidelberg, Mannheim, Germany
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C. Wolpert et al.
becomes symptomatic already in young adults. When confronted with a
patient with left bundle-branch-block tachycardia with inferior axis, a diagnosis of idiopathic RVOT tachycardia can be made only after exclusion of
ARVC. The differential diagnosis of ARVC is based on the criteria of the Task
Force of the Working Group Myocardial and Pericardial Disease of the
European Societ y of Cardiolog y and of the Scient ific Council on
Cardiomyopathies of the International Society and Federation of Cardiology.
Classification is based on electrocardiographic patterns of depolarisation
and repolarisation, echocardiography, endomyocardial biopsy findings, magnetic resonance imaging results, arrhythmia history, and other criteria [5].
However, clinical presentation alone does not allow a diagnosis to be made
in the majority of patients. To differentiate between ARVC and RVOT tachycardia is a clinical challenge, and an intense work up is essential to making
the correct therapeutic decision.
Electrocardiogram in Sinus Rhythm
There are different signs in the surface ECG of patients with arrhythmogenic
right ventricular cardiomyopathy, most strikingly, the T-wave inversion and
an epsilon-wave in lead V1 or V2. In addition, a localised increase of the QRS
duration of > 110 ms in leads V1–V3 or positive late potentials are signs for
a potential ARVC [1, 6, 7]. However, they are not observed in every patient
and especially not during early stages of the disease. Although patients with
a normal ECG at rest are less likely to suffer from ARVC, in the studies of
Niroomand [6] and O’Donnell [7], repolarisation abnormalities in the precordial leads varied between the two studies from 66% to 52% in patients
with ARVC, and from 23% to 6% in patients with RVOT tachycardia.
The ECGs of patients with ARVC often display an incomplete right bundle-branch block or T-wave inversion in the right precordial leads, sometimes also until V4, V5. In Niroomand’s study, T-wave inversion was seen in
13/15 patients (87%), while 14% of patients displayed epsilon waves [6].
O’Donnell observed positive late potentials on the signal-averaged electrogram in 78% of patients with ARVC and in none of the patients with idiopathic RVOT tachycardia.
Electrocardiogram During Ventricular Tachycardia
In patients with ARVC, the ventricular tachycardia (VT) shows a pattern of
left bundle-branch block. The QRS axis is shifted to the right when the VT
originates in the pulmonary infundibulum. The axis may also be shifted to
the extreme left when the VT arises from the diaphragmatic wall or is locat-
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ed in the right ventricular apex or close to the tricuspid annulus [1, 2]. In
patients with ARVC, the upstroke of the QRS complex seems to have some
‘slurring’ and a slew rate that is less steep. The QRS complex also appears
broader. In the study by Niroomand et al., the axis during VT in ARVC was
inferior in 48%, intermediate in 27%, and left/superior in 20% of patients. In
contrast, in patients with idiopathic RVOT tachycardia, it was inferior in 90%
and intermediate or superior in only 5% [6].
The most common clinical presentation of RVOT tachycardia is a frequent,
nonsustained repetition of uniform, monomorphic VT alternating with periods of sinus rhythm. Isolated ventricular extra systoles present the same morphologic pattern as observed in tachycardia. The cycle length of sustained
ventricular tachycardia commonly ranges from 140 to 180 bpm [8, 9].
Transthoracic Echocardiography
The structural major abnormalities in ARVC can be detected by echocardiography, but minor abnormalities are seen only by magnetic resonance imaging (MRI). The signs of the disease are dilation of the right ventricle, the
presence of aneurysm during diastole, and dyskinetic areas in the inferobasal region. Therefore, if there is any doubt about the diagnosis after
transthoracic echocardiography, the patient should undergo cardiac MRI.
Nuclear Magnetic Resonance Imaging
Patients with right ventricular tachycardia should undergo MRI before intervention in order to detect aneurysms, intramyocardial fat, or advanced wall
thickening before catheter ablation, if not distinct on echocardiography or
right ventricular ventriculography [10].
Electrophysiological Study
Electrophysiological studies (EPSs) may help to differentiate RVOT tachycardia due to ARVC from idiopathic RVOT-VT. In the setting of ARVC, the signals of the endocardial electrograms may be significantly altered in terms of
activation delay, fragmentation, amplitude decrease, or dense scarring. These
features are not likely to be found in idiopathic RVOT tachycardia patients.
Some investigators have analysed the endocardial electrograms by using an
electroanatomical mapping tool. Using this approach, Boulos et al. found a
significant difference between patients with ARVC and those with idiopathic
RVOT tachycardia [11]. They also compared the duration and amplitude of
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the electrogram between normal probands, patients with RVOT-VT, and
patients with an ARVC, and could demonstrate that while there was no difference between normal probands and patients with an idiopathic RVOT-VT,
there was a very large difference compared to ARVC patients [11]. Areas with
a strong disposition to fibrofatty degeneration and therefore areas to look
for fragmentation or scarring are the RVOT, the subtricuspidal base of the
ventricle, and the RV-apex. Another indicator for VT in structural heart disease is repetitive inducibility by programmed stimulation and the presence
of a critical coupling interval. O’Donnell found that, in contrast to idiopathic
RVOT-VT patients (3%), VT was induced by extra stimulation in 82% of
pat ients w ith ARVC which indicates a re-ent rant mechanism [6].
Furthermore, in that study, in patients with idiopathic RVOT tachycardia
there was usually only one morphology in premature beats or VT, whereas
71% of patients with ARVC presented from one to six morphologies characteristic of inducible tachycardia. Therefore, in the presence of VT pleomorphism an ARVC should be suspected. Finally, the study also noted that fragmented diastolic electrograms occurred in 82% of patients with ARVC [6].
Inducibility maybe facilitated by infusion of isoproterenol in both clinical
entities and is therefore not a criterion to discriminate between the two diseases.
Triggering Factors for VT and Symptoms
Idiopathic ventricular tachycardia from the RVOT and VT in ARVC are difficult to discriminate based on circumstances of onset, because sustained
tachycardia and salvos tend to be induced by stress, catecholamines, or physical exercise in both cases [1, 2, 6]. However, there is a difference in symptoms in terms of severity for the overall population. Whereas syncope is
more frequent in ARVC and cardiac arrest does practically not occur in idiopathic RVOT-VT, in idiopathic VT there are more mild to moderate palpitations and dizziness due to bradycardia with bigeminus and resulting peripheral pulse deficit. In ARVC, intensive physical activity or extreme anxiety is
known to cause fast and recurrent VT with a considerable risk of sudden
death. Therefore, it should be absolutely avoided in those patients [1].
Conclusions
The diagnosis of an idiopathic RVOT-VT is made by exclusion of ARVC or
any other structural heart disease. If there are no signs of RV myocardial
changes, such as dilatation, dyskinesia, hypokinesia, or aneurysms and wall
thickening, and there are no electrocardiographic signs of ARVC, the patient
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349
most likely has an idiopathic RVOT-VT. However, especially in families with
a history of sudden death, close follow-up may be useful. When enough
minor or major criteria are met, the patient should be risk-stratified and
treatment options should be tailored to the individual, taking into consideration the risks and benefits. In some younger patients with, e.g. syncope and
one other minor criterion and RVOT-VT, this decision is often very difficult
and will probably remain difficult. Genetic testing should be performed in
all patients with a family history in order to detect relatives at risk.
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