Download Introduction - Australian Doctor

How to Treat
PULL-OUT SECTION
www.australiandoctor.com.au
Complete How to Treat quizzes online
www.australiandoctor.com.au/cpd to earn CPD or PDP points.
INSIDE
Bifascicular and
trifascicular block
First-degree
atrioventricular
block
Left bundle
branch block
Early
repolarisation
pattern
Wellens syndrome
Arrhythmogenic
right ventricular
cardiomyopathy
the author
Associate Professor
Stefan Buchholz
consultant cardiologist, Mackay
Base Hospital, Cardiac Services
Unit, Mackay; Associate Professor,
James Cook University school of
medicine, Mackay, Queensland.
ECG
conundrums
Introduction
THE 12-lead ECG is a diagnostic tool
that is very valuable in the evaluation
of cardiac complaints both for diagnostic and screening purposes, and to
support referrals to specialist services.
Most of the ECG findings that may
trigger an immediate consequence —
such as ST-segment deviation, complete heart block, supraventricular and
ventricular tachycardia, Wolff–Parkinson–White syndrome and ventricular fibrillation — have been covered in
past How To Treat articles and will
not be covered here. This article will
concentrate on important ECG findings that are reasonably common in
daily practice but not immediately
associated with any obvious pathological abnormality or medical condition,
including:
• Chronic first-degree heart block.
www.australiandoctor.com.au
• Chronic bi- and trifascicular block.
• Chronic left bundle branch block.
• Early repolarisation pattern.
• Wellens syndrome.
• Arrhythmogenic right ventricular
cardiomyopathy.
cont’d next page
Copyright © 2013
Australian Doctor
All rights reserved. No part of this
publication may be reproduced,
distributed, or transmitted in any
form or by any means without
the prior written permission of
the publisher.
For permission requests, email:
howtotreat@cirrusmedia.com.au
22 November 2013 | Australian Doctor |
23
How To Treat – ECG conundrums
Bifascicular and trifascicular block
THERE has been considerable interest in the potential of various forms
of cardiac conduction disturbances
such as first degree atrio-ventricular
as well as bifascicular or trifascicular block to degenerate into complete heart block.
Bundle branch block is usually
present when there is prolongation
of the QRS duration. The conduction system distal to the AV node
divides into left and right bundle
branches. A block in one of the
bundle branches from any cause
will therefore lead to delayed activation of the corresponding ventricle. The term ‘trifascicular block’ is
commonly applied in daily clinical
practice, and it usually denotes the
combination of right bundle branch
block (RBBB), left anterior hemiblock/fascicular block (LAFB), and
first-degree heart block. However,
this term is inaccurately applied as
it may confuse the issue in patients
with RBBB and block in both fascicles of the left bundle branch, manifesting as complete heart block, or
in patients with RBBB and left posterior hemiblock, as these entities
could also be termed ‘trifascicular
block’.
Figure 1 demonstrates findings
consistent with a bifascicular block.
The underlying rhythm is sinus
rhythm with a rate of about 55
beats per minute. The QRS is just
over 120 milliseconds in duration,
and there is rsR’ configuration in
lead V1 and a broadened s-wave in
leads I and V6, all consistent with
RBBB. The main QRS vector axis
should therefore be right-sided, with
a maximum QRS height somewhere
between +90º and +180º, with positive QRS complexes in leads aVF or
III. As shown in the example, however, the main QRS vector is facing
away from the right-sided (inferior)
leads, with the maximum QRS
Bifascicular block
Figure 1: 12-lead
ECG showing
a ‘bifascicular
block’ (right
bundle branch
block [RBBB]
and left anterior
hemi-block).
being in aVL. This finding, together
with predominant S-waves in leads
II and III (that is, the ratio of R to S
height is <1), is consistent with the
main axis beyond -30º also termed
left axis deviation. This is suggesting
a concomitant left anterior fascicular block, the combination of which
is then termed ‘bifascicular block’
(RBBB and LAFB).
Progression to heart block
One of the important clinical questions is: how often does asymptomatic chronic bifascicular or
trifascicular block degenerate into
symptomatic complete heart block,
requiring some form of intervention
or treatment? A large study from the
early 1980s followed 554 patients
with either bi- or trifascicular block.
The study investigators were able
to demonstrate that 1% of patients
each year progressed to complete
heart block.1 However, the majority of morbidity and mortality noted
in this study was due to the development of tachyarrhythmia rather
than bradycardia, or complete heart
block.
Quite a few studies from the
mid-1970s, however, have shown
a higher incidence of progression to
complete heart block, ranging from
10-16% in patients with chronic
RBBB and LAFB, to as high as 75%
over a period of 1-6 years in patients
with RBBB and left posterior fascicular block.2,3
Risk factors for deterioration
Several risk factors have been found
to be associated with progression
to complete heart block, including
syncope (with bifascicular block at
time of presentation), chronic kidney disease, and a QRS duration of
over 140 milliseconds. The presence
of all of these three risk factors correlated with a 95% chance of developing complete heart block within
one year of presentation, according
to one study.4
Management
Treatment options of chronic bi- or
trifascicular block include cessation and avoidance of drugs
that may slow conduction or
prolong the refractory period of
fascicular tissue and nodal conduction. Examples of medications to stop and avoid include
beta-blockers, calcium antagonists (both dihydropyridine and
non-­dihydropyridine),
digoxin
and flecainide, among others (see
Online resources). Other potentially reversible causes of impaired
conduction, such as myocardial
ischaemia (especially the right coronary artery that usually supplies
the sinus node, AV-node and right
fascicle) or electrolyte imbalance
should be identified and corrected.
Pacemakers
If reversible causes have been corrected or excluded, then permanent
pacemaker insertion in selected
symptomatic patients is indicated.
Some patients have an underlying neuromuscular disorder that
predisposes them to cardiac disease and bundle branch block.
These include myotonic dystrophy, Kearns–Sayre syndrome (a
rare neuromuscular disorder characterised by retinitis pigmentosa,
muscle weakness, ataxia, hearing
loss and diabetes), and other forms
of (usually inherited) muscular
dystrophies. For these patients,
a permanent pacemaker is more
likely to be recommended. This is
mainly because of the unpredictable nature of relentlessly advancing cardiac conduction disease
inherent to these progressive muscular disorders.
The choice of pacemaker (eg,
single or dual chamber pacing, the
rate–response system) is usually
left to the discretion of the operator responsible for pacemaker
insertion. In general, dual-chamber
pacing is recommended as it maintains physiological sequential pacing of the atria and the ventricles.
This helps to reduce the incidence
of ‘pacemaker syndrome’, characterised by the uncomfortable
awareness of palpitations due to
atrial contraction against a closed
mitral valve or, less likely, when
atrial contraction occurs shortly
after ventricular contraction with
incomplete atrial filling (such as in
marked first-degree heart block).
First-degree atrioventricular block
ATRIOVENTRICULAR
(AV)
conduction includes transmission
of an electrical impulse from the
atria to the ventricles, and ‘block’
is defined as a delay or interruption
of this impulse, either temporary or
permanent. Examples of AV block
include first-degree block, seconddegree AV block such as Mobitz
type I (Wenckebach periodicity)
and Mobitz type II, and complete
heart block. Only first-degree heart
block is discussed in this section.
Characteristics of PR interval
AV impulse conduction deficit is
defined as a delay of the PR interval beyond 200 milliseconds (one
large square on the standard ECG).
A normal PR interval is defined
as ranging between 120 and 200
milliseconds. It tends to be shorter
with faster heart rates, owing to
generalised rate-related shortening of the action potential (which
also accounts for the decreased
QT interval seen with faster heart
rates). Children tend to have a PR
interval below 160 milliseconds.
The PR interval is comprised of
the following components of conduction: atrial depolarisation, AV
nodal conduction, the His bundle
24
| Australian Doctor | 22 November 2013
and the infra-Hisian conduction
system including the fascicles and
Purkinje fibres (modified cardiac
muscle fibres originating from the
AV node).
Pathophysiology of first-degree
heart block
It is generally accepted that the
majority of cases of first-degree
heart block are due to an intraatrial or AV nodal conduction
defect. However, it must be pointed
out that in rare instances the defect
may be within the ventricular conduction system at, or well below,
the His bundle, which makes no
difference to the appearance of the
PR interval on a standard 12-lead
ECG. It has been estimated that
intra-atrial block is responsible for
about 3% of cases. Overall, about
80% are due to atrial or AV nodal
delay.5,6
It is estimated that over 90%
of patients with a PR interval
over 300 milliseconds have AV
nodal conduction block, as is frequently observed in patients with
generalised increased vagal tone.7
Sympathetic and parasympathetic
influences on the AV nodal conduction interval at rest are usu-
ally tightly balanced. Enhanced
vagal tone, such as during deep
sleep, athletic training, intense
pain, hypersensitive carotid sinus
syndrome, and during episodes of
vomiting or dry retching, are all
known to increase the AV nodal
conduction time to some degree
(for an extreme example, please see
case study at the end of the article).
Clinical associations
Asymptomatic first-degree AV
block is common. It has been
shown that, among 1000 healthy
aircraft pilots, about 1.6% had
PR intervals exceeding 280 milliseconds, without demonstrable
cardiac structural abnormalities or
symptoms.8
In some cases, however, AV
nodal conduction block is associated with structural abnormalities of the heart. Examples include
Ebstein’s anomaly (ventricularisation of the tricuspid valve), endocardial cushion defects (such as
ostium primum atrial septal defect
or cleft mitral valve as seen in
Down syndrome), infiltrative cardiomyopathies (such as haemochromatosis or amyloidosis) and
cardiomyopathies associated with
www.australiandoctor.com.au
neuromuscular disorders such as
muscular dystrophy. Hence clinical assessment including transthoracic echocardiography can prove
important in the evaluation of
patients with otherwise asymptomatic first-degree AV block.
There are some cases where
first-degree AV block is associated with a widened QRS complex (over 120 milliseconds). This
indicates pathology involving the
infra-Hisian conduction system
in about two-thirds of cases. His
bundle ECGs as done during electrophysiological catheter studies
provide the most accurate answer
as to where the conduction slowing is occurring. Electrophysiology catheters have multiple sites to
measure electrical impulses. During electrophysiology studies (EPS)
it is usually possible to differentiate
the length of the conduction system
below, and including, the AV node,
in much more detail then what is
seen on a standard 12-lead ECG.
Correlation with ECG
Is it possible to clinically determine
the site of the conduction block
when reviewing a 12-lead ECG?
On the whole, the ECG is of lim-
ited value, however, a PR interval
over 300 milliseconds with a normal QRS complex configuration
and duration is most commonly
due to AV nodal block (figure 2A),
whereas widening of the QRS complex indicates a potential problem
in the bundle branches.
Pacemaker syndrome
In some instances, the PR interval is
markedly prolonged. In those cases,
the P wave can morph into the preceding T wave which increased the
amplitude of the T wave, as shown
in figure 2B. This may cause clinical ‘pacemaker syndrome’, which
consists of symptoms and signs
related to AV-dyssynchrony (ie,
atrial contraction against a closed
mitral and tricuspid valve), such
as dyspnoea, palpitations, malaise
and syncope.
Mimicking supraventricular
tachycardia
A markedly prolonged PR interval
could also mimic supraventricular
tachycardia, with complete loss of
the P wave as shown in the example ECG. A way of differentiating
PR prolongation in a patient with
sinus tachycardia from a supraven-
tricular tachycardia is shown in figure 2C. During the release phase of
a Valsalva manoeuvre, for example, the sudden and brief appearance of P waves (arrows) can be
appreciated. This appearance is
due to the prolongation of the T-P
interval (or R-R interval), which
then separates the T wave from the
P wave.
A
First-degree atrioventricular block
Prognosis
Several large-scale cohort studies have investigated the potential
clinical impact of chronic firstdegree heart block. The prospective Framingham Heart Study
found that healthy asymptomatic
patients with a PR interval over
200 milliseconds are more likely
to develop atrial fibrillation (140
vs 36 patients per 10,000 personyears), and need permanent pacemaker insertion (59 vs 6 patients
for pacemaker implantation).
They also had a 1.4 times higher
adjusted risk all-cause mortality
when compared to patients with
normal AV conduction.9 This
study included over 7500 patients
who were followed over almost 40
years. A further prospective study
of almost 1000 patients with stable
coronary artery disease identified
87 patients with PR interval over
220 milliseconds. Compared with
patients with normal AV conduction, these patients had a 2.3 times
higher risk of hospitalisation for
heart failure as well as cardiovascular mortality.10
Management
Current evidence therefore suggests that first-degree AV block
B
C
Figure 2: A:
First-degree
atrioventricular
block. B:
First-degree
atrioventricular
block in same
patient during
episode of
tachycardia (anxiety
related), showing
fusion of the P
and T wave with
‘disappearance’
of the P-wave. C:
Dissociation of P
and T wave during
Valsalva manoeuvre
(black arrows
showing P-wave) in
the same patient.
Valsalva
in healthy asymptomatic patients
as well as in those with known
coronary artery disease is associ-
ated with a higher overall risk of
cardiac morbidity and mortality.
Most patients with first-degree
AV block will not need permanent
pacemaker insertion. This includes
those who are asymptomatic or
in whom AV block is expected
to resolve and is unlikely to recur
(such as in suspected medication toxicity, transient increase in
vagal tone or decrease in oxygenation such as in obstructive sleep
apnoea). The current North American guidelines (AHA/ACC 2008),
however, conclude that permanent
pacemaker insertion may be considered in patients with first-degree
AV block associated with underlying neuromuscular disease (such as
Erb’s dystrophy, myotonic dystrophy, or Kearns–Sayre syndrome),
even when asymptomatic (class
IIb recommendation; Level of Evidence: B).
In terms of medical management,
routine prophylactic anticoagulation is not advised, because the
absolute number at risk is small in
those without AF (see Framingham
Heart Study mentioned earlier).
Routine prophylactic anticoagulation would unnecessarily expose
a lot of patients to antiplatelet or
anticoagulation therapy. Once AF
had established, anticoagulation
would be recommended according
to the usual guidelines.
It is not necessary to follow
patients without AF with repeated
tests but it is important to make
them aware of what palpitations
feel like. There are no data on
whether seemingly asymptomatic
patients should be closely scrutinised for coronary artery disease.
However, in patients with cardiovascular risk factors and firstdegree block, it is prudent to make
a dedicated appointment and discuss primary prevention strategies
with the patient.
Left bundle branch block
Clinical significance
THE prevalence of left bundle
branch block (LBBB) in young
healthy males has been shown to
be about 0.05%. Over 90% of
these have no evidence of structural heart disease on further
investigation.11 No increase in
mortality was observed in the
subpopulation without structural
heart disease.
Data from the Framingham
Heart Study has shown that
people who developed LBBB later
in life (over 60 years of age) had a
higher incidence of coronary heart
disease and hypertension and that
LBBB is an independent predictor
of all-cause mortality. This finding has been confirmed by several
other studies.12 Individuals with
LBBB and type 2 diabetes usually
have more severe and extensive
coronary atherosclerosis when
compared with patients with diabetes who do not have LBBB.
Pathophysiology
Most patients with LBBB have
underlying coronary artery disease,
not uncommonly involving the
proximal part of the left anterior
descending artery, which supplies
all the proximal septal branches.
The bundle of His divides into the
right and left bundle branches just
beyond the muscular and fibrous
boundaries of the proximal septum. The left anterior descending artery supplies the left bundle
branch, usually with some collat-
Left bundle branch block
Figure 3: Sinus
rhythm with
typical left bundle
branch block.
of the QRS complex (eg, positive
QRS in V6 and negative ST and T
in the same lead). ‘Negative’ QRS-T
concordance, meaning negative ST
or T waves in the anterior leads
with negative QRS is unusual, and
is usually associated with underlying
ischaemia.
Appropriate investigations
The presence of LBBB makes diagnosis of myocardial ischaemia very
difficult and a stress ECG is unlikely
to be helpful due to the marked resting QRS abnormalities. Stress echocardiography or exercise nuclear
perfusion imaging is therefore preferred when evaluating a patient for
coronary artery disease.
erals from the circumflex and right
coronary artery.
Other associations
LBBB may also be associated
with slowly advancing degenerative conduction system disease,
infiltrative cardiomyopathies with
normal coronary arteries, and
completely healthy and structurally normal hearts.
Interpreting the ECG
The characteristic changes seen on
a 12-lead ECG in LBBB are very
dramatic. The diagnosis can usually be made through ‘pattern recognition’ rather than dissecting the
ECG systematically.
Loss of Q waves
The main components usually
found in ‘typical’ LBBB (figure 3)
include a loss of the Q waves in the
leftward leads — I, aVL, V5 and
V6. Small Q waves in these leads
are normal and reflect normal
early proximal septal activation
that usually causes Q wave deflections (<1mm in the anterior/chest
leads and <2mm in the limb leads)
when the cardiac muscle depolarises from the outside (epicardium)
to the inside (endocardium) of the
cardiac chambers. In LBBB, these
Q waves are lost especially in lead
I, but occasionally in lead aVL.
Significance of large Q waves
A potential clue for the presence of
www.australiandoctor.com.au
Management
underlying coronary artery disease
is a significant Q wave that is larger
and broader than expected in LBBB
in these leads. Figure 3 is an ECG
taken from a patient four months
after anterior STEMI. The black
arrow shows a significant Q wave
in lead aVL, larger and broader than
expected in LBBB, and hence raises
suspicion of coronary artery disease.
QRS complex changes
The QRS complex in LBBB is large
and dysmorphic, the duration usually prolonged at over 120 milliseconds, with broad or notched
R waves in the leftward leads, and
occasional RS pattern in V5 and
V6. The ST and T waves are most
commonly divergent to the direction
Given the association of cardiovascular disease with LBBB, these
patients should be carefully evaluated
for arterial hypertension, coronary
artery disease, and other disorders
associated with conduction disease,
such as myocarditis, infiltrative cardiomyopathies, valvular heart disease and, rarely, hyperkalaemia. For
patients with an isolated LBBB and
no evidence of underlying structural
heart or coronary disease, no specific therapy is required. Patients with
LBBB and unexplained syncope may
be considered for permanent pacemaker insertion, especially when
further conduction abnormalities
such as second or third degree are
subsequently documented.
cont’d next page
22 November 2013 | Australian Doctor |
25
How To Treat – ECG conundrums
Early repolarisation pattern
THE early repolarisation pattern is
not uncommonly seen on ECGs of
younger individuals, with an estimated prevalence of about 10%. It
has long been thought to represent
a ‘benign’ variant of a normal ST
segment. Recent studies suggest,
however, early repolarisation pattern is not ‘benign’ a priori, just as
‘benign’ intracranial hypertension
is not necessarily ‘benign’.
Figure 4: 12-lead
ECG of a young
asymptomatic
male with a
J-point elevation
of at least 0.2
mV (two small
squares) in the
inferior (II, III,
aVF) as well as
the lateral leads
(V5 and V6).
Early repolarisation pattern
J-point is elevated in early
repolarisation
In early repolarisation, the ECG
changes include elevation of the
J-point (defined as the junction
between the end of the QRS complex and the beginning of the ST
segment, normally level with or
<0.1mV above the PR segment on
the ECG) by more than 0.1mV in
at least two contiguous leads. Figure 4 shows a 12-lead ECG of a
young asymptomatic male with a
J-point elevation of at least 0.2 mV
(two small squares) in the inferior
(II, III, aVF) as well as the lateral
leads (V5 and V6). The insert A
shows the exact location of the
J-point and its elevation, a feature absent from the ECG insert
B without J-point elevation. Most
commonly, in early repolarisation
the J-point is elevated in either all
of the inferior leads, or all of the
anterior chest leads. Occasionally
the J-point elevation would be
found in both the inferior leads
and the anterior chest leads.
Differential diagnoses
Differential diagnoses of J-point
elevation include J-waves (also
known as Osborn waves), which
are transiently seen in cases of
hypothermia, acute myo-pericarditis and ST-segment elevation myocardial injury. Marked J-waves or
J-point elevation are also seen in
Brugada syndrome, although the
J-point elevations are usually only
seen in the right precordial leads
V1-V3.
Progress and clinical
associations
It has been demonstrated that early
repolarisation pattern may be a
transient phenomenon. In a study
involving over 500 individuals with
early repolarisation pattern on baseline ECG, about 20% of the subjects
did not have the pattern at the fiveyear follow-up study.13
Inheritance patterns
Some studies have shown a twoto threefold increase in the probability that a first-degree relative
of a person with early repolarisation pattern will also have the
same ECG pattern. This raises the
question of whether early repolarisation pattern could be inherited. Rarely, families with early
repolarisation pattern and a high
incidence of sudden cardiac death
have been identified. An autosomal dominant inheritance in such
families was suggested. If such
an association exists, early repolarisation pattern could represent
a potential health hazard rather
than being benign as previously
thought.
Predisposition to ventricular
fibrillation
A large case–control study has
shown the prevalence of early
repolarisation pattern is 31% in
more than 200 patients with idiopathic ventricular fibrillation compared with only 5% in over 400
healthy control individuals. Over a
six-year follow-up there was a 2.1
times higher rate of implantable
cardioverter-defibrillator shocks
for recurrent VF in patients with
early repolarisation pattern than in
the healthy control population.14 It
appears that the greatest risk of VF
is associated with early repolarisation in the inferior leads > 0.2mV.
However, early repolarisation
pattern is reasonably common in
young asymptomatic individuals,
and unexplained or idiopathic VF
is very rare. Larger studies have
estimated the incidence of idiopathic VF in a person younger
than 45 years to be 3 in 100,000.
The incidence increases to 11 in
100,000 when early repolarisation
pattern is present.15 This finding
has been confirmed by a recent
meta-analysis involving more
than 140,000 early repolarisation
pattern-positive individuals with
a collective 3.6 million personyears follow-up. The study demonstrated a 1.7 times increased risk of
arrhythmic death compared with
an equally large control group. The
estimated absolute risk difference
of early repolarisation patternpositive subjects was 70 cases of
death attributed to primary cardiac
arrhythmia per 100,000 personyears. Again, early repolarisation
pattern in the inferior leads was
identified as the ECG location conferring the highest risk.
The exact mechanism that
causes the early repolarisation pattern is not well understood, and
the precise mechanism for VF is
unknown. In all likelihood early
repolarisation and VF are due to
ion-channel current imbalance,
possibly similar to Brugada syndrome or short QT syndrome.
Further research is underway to
elucidate the potential genetic basis
for this disorder.
Treatment
Because of the high prevalence of
early repolarisation pattern in the
general population, the current consensus is that no additional tests or
investigations are indicated, unless
there is a history of syncope or
familial sudden cardiac death. Such
patients should be further evaluated,
ideally in a specialist cardiology
clinic. Survivors of sudden cardiac
arrest due to otherwise unexplained
primary VF arrest, are best treated
with an implantable cardioverterdefibrillator.
Class 1a antiarrhythmic therapy
may be indicated as a therapeutic
option in an early repolarisation
pattern-positive patient with recurrent VF after implantable cardioverter-defibrillator
implantation.
However, the choice of antiarrhythmic therapy needs to be individualised.
Emergency treatment
In patients with known or suspected
early repolarisation pattern presenting with sudden cardiac arrest and
ongoing episodes of recurrent VF,
intravenous isoproterenol has been
shown to be beneficial in suppressing VF storm.
Wellens syndrome
WELLENS syndrome is named after
Dutch cardiologist Hein Wellens. It
is a potentially very dangerous cardiac condition that may go unnoticed because of the timing of ECG
changes and the occasional non-specific appearance. Wellens syndrome
has been convincingly linked to an
imminent occlusion of the proximal
left anterior descending coronary
artery, threatening infarction of
the anterior left ventricle, usually
involving a large area.
Figure 5: Sinus
rhythm ECG from
a patient with a
subacute proximal
left anterior
descending artery
occlusion. A: The
more common ‘type
1’ Wellens ECG. B:
The uncommon ‘type
2’ Wellens ECG.
Wellens syndrome
Management
Diagnosis
The syndrome criteria include characteristic ‘Wellens-type’ anterior
T-wave changes, recent history of
chest pain suggestive of angina, little
or no cardiac biomarker elevation,
normal precordial R-wave progression without Q waves (this excludes
previous anterior infarction which
can mimic the ECG changes in
Wellens syndrome), and no significant ST elevation.
ECG findings
The ECG changes associated with
this syndrome can be very subtle,
and are usually confined to the
anterior precordial leads, most
26
| Australian Doctor | 22 November 2013
may therefore be entirely missed if
serial ECGs are not being done.
In Wellens’ original description,
only about 1 in 10 patients had
cardiac biomarker elevation; the
ECG may be the only indication
of an impending infarct in an otherwise pain-free patient. Therefore,
a high index of suspicion needs to
be maintained when dealing with
patients who may have Wellens
syndrome.
commonly seen in V2-V4. Two
different ECG pattern have been
described by Wellens’ team: the
more common ‘type 1’ (figure 5A),
with deep symmetrical T-wave
inversion, and ‘type 2’ (figure 5B),
causing rather subtle biphasic T
waves anteriorly. Type 2 Wellens
ECG is less common (only about
25% of patient with the syndrome
display this ECG pattern), and
may go either completely unnoticed by automated computerised
ECG interpretation algorithms or
is being reported as ‘non-specific’.
Both ECG types are consistent
www.australiandoctor.com.au
with a pre-infarction stage (when
seen in the setting of symptoms and
signs suggesting an acute coronary
syndrome), and impending occlusion of the left anterior descending
artery. These ECG changes interestingly do not appear until about 4-6
hours after the onset of angina, and
Exercise stress testing is contraindicated in Wellens syndrome as this
could lead to acute infarction and
VF arrest.
Urgent admission to a coronary
care unit and expedited inpatient
transfer to a percutaneous coronary intervention-capable hospital
for coronary angiography is recommended if these ECG changes
occur in the context of symptoms
and signs suggesting an acute
coronary syndrome. Additionally,
these patients should be medically
treated as per current guidelines
for an acute coronary syndrome/
NSTEMI.
cont’d page 28
How To Treat – ECG conundrums
Arrhythmogenic right ventricular cardiomyopathy
THE prevalence of arrhythmogenic
right ventricular cardiomyopathy
(ARVC) is estimated at about 1 in
3000. This condition is an important cause of sudden cardiac death in
young adults. It is probably underrecognised as some of the clinical
symptoms and signs can be very
subtle.
References
Figure 6:
Transthoracic
echocardiogram
from the subcostal
view, showing a
dilated, infiltrated
and thickened
right ventricle
(white arrows).
Increased rate of sudden cardiac
death
It is estimated that 10% of cases
with sudden cardiac death are due
to ARVC. The condition is characterised by right ventricular scarring
with patchy fibrous or fibro-fatty
replacement of the normal myocardium, ultimately leading to right
ventricular dilatation (figure 6).
The mean age at diagnosis is about
30 years. It has been suggested
that about 30% of cases are familial, involving the desmoplakin–­
desmosomal protein discs that
connect myocytes electrically.
A European study has found that
the incidence of ARVC in sudden
cardiac death in athletes may be
as high as 20%.16 This may be at
least partly due to abnormal stress
response of the right ventricle and
impaired sensitivity to catecholamines resulting in abnormal cardiac
sympathetic function.
A
RVOT ventricular tachycardia @ 220 bpm, LBBB
Diagnosis
The diagnostic criteria for ARVC
are complex and based on findings
obtained by 2D echocardiography,
12-lead ECG, cardiac MRI, endomyocardial biopsy and family history.17
B
RVOT ventricular tachycardia @ 260 bpm, with RBBB
Genetic inheritance patterns
Autosomal dominant transmission
is most common, however larger
families with autosomal recessive
inheritance have been identified.
This is especially the case in the
Mediterranean area where ARVC
is part of the ‘Naxos’ syndrome
(named after a Greek island with a
very high prevalence of autosomal
recessive ARVC). This cardiocutaneous syndrome also presents with
palmoplantar keratoderma and
frizzy hair.
Figure 7: A: Right ventricular outflow tract (RVOT) ventricular tachycardia from
a patient with arrhythmogenic right ventricular cardiomyopathy. B: ‘Common’
ventricular tachycardia originating within the left ventricle, hence showing RBBB
activation.
Clinical presentation
About 40% of cases with ARVC
are asymptomatic. They are usually
picked up during family screening
of an identified patient. As many
as 50% of patients have a normal
ECG at presentation, especially
those with no significant or minimal right ventricular thickening,
dysplasia or dilatation.
When symptomatic, the principal
features include palpitations (not
uncommonly triggered by stress or
physical exertion), syncope and, as
mentioned, sudden cardiac death.
Although ventricular tachycardia
is the most common arrhythmia,
patients with ARVC can present
with supraventricular tachycardia
(atrial tachycardia, AF or flutter).
Ventricular tachycardia
Ventricular tachycardia (VT) is
identified as a monomorphic nonsustained or sustained broad complex tachycardia with a LBBB
morphology (this is because the VT
frequently originates in the right
ventricular free wall and then traverses across the septum to the left
ventricle). Figure 7 shows two different VTs: figure 7A has been taken
from a 39-year-old male with exercise-induced VT, with underlying
ARVC. Note the VT main vector
and precordial QRS configuration
in this case is consistent with LBBB,
28
| Australian Doctor | 22 November 2013
tricular ARVC or, rarely, left ventricular involvement only.
A
B
C
D
ECG findings
Although as many as 50% of
patients have a normal ECG at
presentation, the following changes
may be the first clue to the presence
of underlying ARVC:
• Epsilon wave (figure 8A): An epsilon wave, present in up to 30%
of cases, represents multiple low
amplitude after-depolarisations
caused by delayed activation of
the right ventricle. This ECG finding is very suggestive of ARVC
and is usually present in advanced
stages of right ventricular involvement. The epsilon wave, especially
when prominent, can be mistaken
for a P wave.
• T-inversion in the right precordial
leads (usually V1-V3, figure 8B):
This is not a sensitive (only positive in 50% at presentation) nor
specific (also seen in Brugada syndrome) ECG finding, and is said
to correlate with right ventricular
dilatation.
• Right ventricular conduction
delay, incomplete RBBB, or QRS
prolongation over 110 milliseconds in the absence of a ‘typical’
RBBB (figure 8C), are uncommon
overall but highly specific findings.
• Delayed upstroke of the S wave
in any of the right precordial leads
(V1-V3), defined as the interval
from the nadir of the S wave to the
end of the QRS over 55 milliseconds (about 1.5 small squares on
the standard ECG with 25mm per
second paper speed, figure 8D). In
the example given, the delay in S
wave upstroke is 2 small squares
= 80 milliseconds).
Management
Figure 8: 12-lead ECG taken from a patient who had a history of symptomatic VT
and underlying ARVC. A: Epsilon wave. B: T-inversion in a right precordial lead.
C: Prolongation of the QRS complex due to after-depolarisations (epsilon-wave).
D: Delayed S-wave upstroke.
with negative QRS in lead V1. Insert
B demonstrates a VT originating in
the left ventricle (hence with RBBB
and positive QRS deflection in V1)
in a patient with ischaemic heart
disease. Determining whether LBBB
or RBBB is present, to some degree,
may help to at least narrow down
whether the VT originates in the
left or the right ventricle. That said,
there are quite a few case reports in
the literature demonstrating bivenwww.australiandoctor.com.au
Current guidelines suggest that
cardioverter-defibrillator implantation should be reserved for select
patients. These include those with
sustained VT, cases of survived
sudden cardiac arrest, primary VF
or for selected high-risk patients
(eg, patients with extensive disease
with right ventricular and left ventricular involvement, one or more
affected family members with sudden cardiac death, or undiagnosed
syncope, among others).
Individuals with ARVC, even
when asymptomatic, should not
partake in intense endurance training or competitive sports.
1. McAnulty JH, et al. Natural history
of ‘high-risk’ bundle-branch block:
final report of a prospective study.
New England Journal of Medicine
1982; 307:137-43.
2. K
ulbertus HE. The magnitude of risk
in developing complete heart block
in patients with LAD-RBBB. American Heart Journal 1973; 86:278-80.
3. S canlon PJ, et al. Right bundlebranch branch block associated with
left superior or inferior intraventricular block. Clinical setting, prognosis,
and relation to complete heart block.
Circulation 1970; 42:1123-33.
4. M
arti-Almor J, et al. Novel predictors of progression of atrioventricular block in patients with chronic
bifascicular block. Revista Espanola
de Cardiologia 2010; 63:400-08.
5. N
arula OS. Atrioventricular
block. In: Cardiac Arrhythmias:
Electrophysiology, Diagnosis and
Management. Williams and Wilkins,
Baltimore, 1979.
6. P
euch P. The value of intracardiac
recordings. In: Krikler D, Goodwin
JF (editors). Cardiac Arrhythmias.
Saunders, Philadelphia, 1975.
7. J osephson ME. Clinical Cardiac
Electrophysiology: Techniques and
Interpretations, 2nd edn. Lea &
Febiger, Philadelphia, 1993.
8. G
raybiel A, et al. Analysis of the
electrocardiogram obtained from
1000 young healthy aviators; ten
year follow-up. Circulation 1954;
10:384-400.
9. C
heng S, et al. Long-term outcomes in individuals with prolonged PR interval or first-degree
atrioventricular block. Journal of the
American Medical Association 2009;
301:2571-77.
10. C
risel RK, et al. First-degree atrioventricular block is associated with
heart failure and death in persons
with stable coronary artery disease:
data from the Heart and Soul
Study. European Heart Journal
2011; 32:1875-80.
11. R
otman M, Triebwasser JH. A
clinical and follow-up study of
right and left bundle branch block.
Circulation 1975; 51:477-84.
12. S chneider JF, et al. Newly acquired
left bundle branch block: the
Framingham study. Annals of
Internal Medicine 1979; 90:303-10.
13. T
ikkanen JT, et al. Long-term
outcome associated with early repolarization on electrocardiography.
New England Journal of Medicine
2009; 361:2529-37.
14. H
aissaguerre M, et al. Sudden
cardiac arrest associated with early
repolarization. New England Journal of Medicine 2008; 358:201623.
15. R
osso R, et al. J-point elevation in
survivors of primary ventricular
fibrillation and matched control
subjects: incidence and clinical
significance. Journal of the American College of Cardiology 2008;
52:1231-38.
16. C
orrado D, et al. Screening for
hypertrophic cardiomyopathy in
young athletes. New England Journal of Medicine 1998; 339:364-69.
17. M
arcus FI, et al. Diagnosis of
arrhythmogenic right ventricular cardiomyopathy/dysplasia:
proposed modification of the task
force criteria. Circulation 2010;
121:1533-41.
Online resources
Overview of Arrhythmias
(includes medications that may
cause impaired conduction):
bit.ly/19NTiA
cont’d page 30
How To Treat – ECG conundrums
Case study
Conclusion
A PREVIOUSLY healthy 32-yearold woman was admitted to the
ICU after a series of blackouts
during a hens’ night party. It transpired that she passed out three
times in quick succession without
premonitory symptoms or signs.
All three blackouts happened
straight after she bent forward to
vomit. Usually not keen on drinking alcohol, she admitted that she
had drunk “way too much” during the party. She remembered
that she passed out twice for a
few seconds onto the bathroom
floor right after a large vomit, and
another time while she was lying
flat on a bed, heaving and dry
retching.
Her past medical history was
unremarkable and she was not
on any prescription medication.
However, she mentioned that she
had experienced syncope seven
years ago when she had vomited
during an episode of food poison-
Figure 9: Patient’s ECG, showing a six-second pause due to asystole.
ing. At the time, the syncope was
felt to be due to dehydration.
Initial examination revealed an
inebriated slim female without
apparent distress. She was haemodynamically stable, blood pressure
recorded via a left radial arterial
line was 140/60mmHg, and heart
rate of 60 beats per minute. Initial blood work was unremarkable, the Glasgow Coma Scale
(GCS) and BSL were normal, and
12-lead ECG showed normal sinus
rhythm. During an episode of dry
retching, however, she suddenly
became unresponsive, with an
ECG showing a six-second pause
due to asystole (figure 9). A second episode of retching resulted in
a 20-second asystole, necessitating
CPR and emergency insertion of a
temporary pacing wire.
Complete this quiz online and fill in the GP evaluation form to earn 2 CPD or PDP points.
We no longer accept quizzes by post or fax.
The mark required to obtain points is 80%. Please note that some questions have more than one correct answer.
ECG conundrums —
22 November 2013
2. W
hich TWO statements are correct
regarding bifascicular and trifascicular
blocks?
a) R
isk factors associated with the progression
of a partial bundle branch block to complete
heart block, including syncope, chronic
kidney disease and a QRS duration of
>140ms
b) T
here is an annual 40% risk of progressing to
complete heart block
c) U
p to 75% of patients with a right bundle
branch block and left posterior fascicular
block will progress to complete heart block
over a period of 1-6 years
d) A
ll bifascicular or trifascicular blocks should
be treated with permanent pacemaker unless
contraindicated
3. W
hich TWO statements are correct
regarding first-degree heart block?
a) O
nly 3% of first-degree heart blocks are due
to intra-atrial block
b) P
atients with haemochromatosis may have
associated first-degree heart block
THE 12-lead ECG is an invaluable diagnostic tool in the evaluation of cardiac complaints.
There are many significant ECG
changes that are commonly
found in daily medical practice
but may not trigger an immediate consequence.
Chronic first-degree heart
block and other bundle branch
block patterns are often diagnosed on asymptomatic patients.
While there is no immediate lifethreatening consequence of these
ECG patterns, long-term followup and management is important
to prevent complications.
Conditions such as Wellens
syndrome and arrhythmogenic
right ventricular cardiomyopathy are uncommon and the ECG
changes may be subtle but have
significant prognostic implications. A correct diagnosis may be
instrumental in saving the life of
the patient.
Instructions
How to Treat Quiz
1. W
hich TWO statements are correct
regarding the electrical tracings of the
heart?
a) T
he PR interval reflects atrial depolarisation,
AV nodal conduction, His bundle and the
infra-Hisian conduction system
b) T
he PR intervals in children are longer than
in adults
c) T
he J-point is defined as the point of peak
amplitude of the T wave
d) S
mall Q waves are physiological deflections
of the electrocardiac conduction when
the cardiac muscle depolarises from the
epicardium to the endocardium
The underlying diagnosis was
consistent with neurally mediated
reflex syncope, which can be classified according to the pattern of
change in heart rate or BP into
vasodepressor (vasodilatory hypotension), cardioinhibitory (bradycardia/asystole), or a mixture of
the two main patterns.
Markedly increased parasympathetic–vagal activity (dry retching
and vomiting), in susceptible individuals, may acutely shorten the
atrial refractory period (potentially causing atrioventricular
blockade) and/or inhibit impulse
generation in the sinoatrial node,
causing sinus arrest/asystole.
In the case presented, the
cardio­
inhibitory component was
felt to be playing the dominant
role, and therefore dual-chamber
permanent pacing was recommended and carried out, with the
patient remaining well during 12
months’ follow-up.
GO ONLINE TO COMPLETE THE QUIZ
www.australiandoctor.com.au/education/how-to-treat
c) First-degree heart block is characterised by a
normal QRS complex
d) A PR interval >300ms with a normal QRS
indicates a potential problem in the bundle
branches
4. Which TWO statements are correct
regarding left bundle branch blocks?
a) New-onset left bundle branch block after the
age of 60 is associated with increased risk of
coronary artery disease
b) A negative QRS-T concordance in the
anterior leads excludes underlying cardiac
ischaemia
c) An exercise stress test should be the firstline investigation for left bundle branch block
with suspected myocardial ischaemia
d) Left bundle branch block and type II
diabetes together increase the risk of
more severe and extensive coronary
atherosclerosis
5. Which TWO statements are correct
regarding early repolarisation patterns?
a) Familial early repolarisation pattern in an
autosomal dominant inheritance is benign
b) Early repolarisation pattern has a sixfoldhigher association in patients with idiopathic
ventricular fibrillation than those without
c) All early repolarisation patterns should
be thoroughly investigated to prevent
complications
d) Twenty per cent of patients with early
repolarisation pattern do not exhibit this
pattern five years later
6. Which TWO statements are correct
regarding Wellens syndrome?
a) Wellens syndrome is characterised by
ischaemic chest pain, raised cardiac
enzymes and pathological anterior Q
waves
b) The ECG changes associated with Wellens
syndrome are typically confined to the
anterior precordial leads, most commonly
seen in V2-V4
c) Any patient suspected of having Wellens
syndrome should undertake an exercise
stress test immediately
d) Serial ECGs should be taken at 4-6 hours
after the onset of ischaemic chest pain in
suspected Wellens syndrome
7. Which TWO statements are correct
regarding arrhythmogenic right
ventricular cardiomyopathy?
a) The mean age at diagnosis is about 30 years
b) This condition is typically due to
spontaneous mutation
c) More than 90% of cases with
arrhythmogenic right ventricular
cardiomyopathy are silent, with a normal
ECG
d) Epsilon waves are very suggestive
of arrhythmogenic right ventricular
cardiomyopathy and are found in up to 30%
of cases
8. Katie is a 47-year-old woman who
presented for follow-up on a past
history of first-degree heart block found
incidentally. Which TWO statements are
correct?
a) Asymptomatic first-degree heart block is
rare
b) Efforts should be made to exclude
underlying medication toxicity and
obstructive sleep apnoea
c) Echocardiography is never indicated when
an ECG had been done to confirm the
history
d) A markedly prolonged PR interval in firstdegree heart block could look just like
supraventricular tachycardia
9. Katie is otherwise healthy. Which TWO
statements are correct regarding her
prognosis?
a) Katie has a 1.4-times-higher risk for all-cause
mortality compared with a person with normal
AV conduction
b) Since she is asymptomatic, Katie can expect
to have no higher risk of developing atrial
fibrillation than any other patient with normal
AV conduction
c) Even if Katie develops underlying coronary
artery disease, she will have no higher risk
of cardiovascular mortality compared with
patients with normal AV conduction
d) If her PR interval elongates, Katie may be at
risk of developing AV dyssynchrony
10. A repeat ECG showed that Katie has
developed trifascicular block. Which TWO
statements are correct regarding this
development?
a) A trifascicular block is another name for a
complete heart block
b) The majority of morbidity and mortality from
trifascicular block is due to the development
of tachyarrhythmia
c) Dihydropyridine calcium antagonists should
be avoided while non-dihydropyridine
antagonists may be used
d) Katie should be referred for investigation to
identify and correct any underlying coronary
ischaemia
CPD QUIZ UPDATE
The RACGP requires that a brief GP evaluation form be completed with every quiz to obtain category 2 CPD or PDP points for the 2011-13 triennium.
You can complete this online along with the quiz at www.australiandoctor.com.au. Because this is a requirement, we are no longer able to accept
the quiz by post or fax. However, we have included the quiz questions here for those who like to prepare the answers before completing the quiz online.
how to treat Editor: Dr Steve Liang
Email: steve.liang@cirrusmedia.com.au
Next week General practice provides many opportunities for research, but GPs are often reticent about participating. Our special How to Treat next week is a comprehensive guide to research projects
in general practice. The authors are Associate Professor Amanda McBride, head of general practice and discipline leader — general practice, school of medicine, University of Notre Dame Australia,
Sydney, and Dr Charlotte Hespe, head of general practice and head of general practice research, school of medicine, University of Notre Dame Australia, Sydney, NSW.
30
| Australian Doctor | 22 November 2013
www.australiandoctor.com.au