Open Journal of Internal Medicine, 2012, 2, 31-33 OJIM Published Online March 2012 (
Two cases of juvenile hypertrophic cardiomyopathy
presenting with marked bi-atrial enlargement on
standard 12-lead electrocardiogram*
Hajime Kataoka
Division of Internal Medicine, Nishida Hospital, Oita, Japan
Received 19 September 2011; revised 8 November 2011; accepted 18 November 2011
This report describes two cases of juvenile hypertro-
phic cardiomyopathy (HCM) in which prominent
bi-atrial enlargement was observed on standard 12-
lead electrocardiogram, suggesting inherent predis-
position to extreme enlargement and/or hypertrophy
may exist in atrial myocardium in juvenile HCM.
Comparative study between juvenile and adult HCM
patients using a large sample size is required to con-
firm this hypothesis.
Keywords: Hypertrophic Cardiomyopathy;
Electrocardiogram; P-Wave; Atrial Enlargement
Previous reports [1,2] indicate that an inverse relation
exists between left ventricular hypertrophy and age, and
suggest that left ventricular hypertrophy often progresses
in juvenile hypertrophic cardiomyopathy (HCM). Pro-
gression of atrial enlargement in relation to age has not
yet been examined. Here, this report describes two cases
of juvenile HCM in which prominent bi-atrial enlarge-
ment was observed on 12-lead electrocardiograms (ECG).
In this report, the ECGs were interpreted following the
criteria described by Savage et al. [3]; notably, the left
atrial enlargement was diagnosed if the product of the
depth and duration of the negative portion of the P-wave
in lead V1 was greater than 0.03 mV-sec [4]. The right
atrial enlargement was diagnosed if there were peaked
P-waves in leads II and III or V1,2 2.5 mV in amplitude.
Case No. 1. A 19-year-old female had been diagnosed as
HCH since the age of 11 years and was taking verapamil.
Follow-up clinical, chest x-ray, standard 12-lead ECG
and echo-Doppler studies were obtained periodically.
Gradual bi-atrial enlargement was observed on serial
standard 12-lead ECGs. In parallel with this, her New
York Heart Association functional class deteriorated
from class I at initial visits to class III at recent visits.
The 12-lead ECG taken at the age of 19 years (Figure 1)
showed a regular sinus rhythm with prominent right
(amplitude of the P initial force V2 lead = 0.5 mV) and
left atrial (Morris index of the P terminal force V1 = 0.4
mm-sec) enlargement, incomplete right bundle branch
block and ST-T changes. Echo-Doppler study taken
around this period disclosed asymmetric septal hyper-
trophy (20 mm) and hypertrophic right ventricular free
wall (10 mm). Left cavity size was normal (end-diastolic
*Disclosures: The author has no conflicts of interest to disclose. Figure 1. Standard 12-lead ECG of Case No. 1.
H. Kataoka / Open Journal of Internal Medicine 2 (2012) 31-33
volume of 83 cc), but the ejection fraction was slightly
depressed (51%). Moderate enlargement of both atria and
mild tricuspid regurgitation were noted. Rest thallium-
201 myocardial scintigram showed marked right ven-
tricular hypertrophy and visualization of the right atrial
appendage. Addition of diuretics slightly improved her
clinical condition.
Case No. 2. An 18-year-old male had been diagnosed
as HCM since the age of 5 years. At the age of 13 years,
he developed complete atrio-ventricular block and un-
derwent permanent VVI pacemaker therapy. Serial stan-
dard 12-lead ECGs before (a) and after pacemaker ther-
apy (b and c) are shown in Figure 2. At the 3-year fol-
low-up, 12-lead ECG demonstrated gradual enlargement
of the right (amplitude of the P initial force V1 lead =
0.35 mV) and left atrial (Morris index of the P terminal
force V1 = 0.4 mm-sec) enlargement (Figure 2(b)). In
parallel with P-wave abnormalities, progressive heart
failure developed and he was admitted twice during this
follow-up period. Echo-Doppler study during the conva-
lescent phase demonstrated asymmetric septal hypertro-
phy (16 mm) with a slightly dilated (end-diastolic vol-
ume of 118 cc) and moderately hypokinetic (ejection
fraction of 45%) left ventricle. Both the left and right
atria were moderately enlarged. Slight mitral regurgita-
tion and moderate tricuspid regurgitation were detected
on Doppler echocardiography. Rest thallium-201 myo-
cardial imaging showed a moderate degree of isotopic
uptake in the right ventricle. Medical therapy was not
sufficient to improve his clinical condition. Because
atrio-ventricular uncoupling due to VVI pacing was con-
sidered to be a major contributory factor to congestive
heart failure, VVI pacing was switched to dual-chamber
pacing, resulting in an improved clinical condition and
decrease of the bilateral atrial enlargement on 12-lead
ECG (Figur e 2(c)).
No previous report has specifically addressed the relation
between atrial abnormalities and age in HCM patients.
This case presentation of two juvenile HCM patients
seems to be important because it was suggested that,
beside from the hemodynamic overloading on the right
and left atria as the main cause, such ECG findings of
prominent atrial enlargement may be induced by factor
responsible for the body growth and development char-
acteristics of childhood and adolescence. Previous re-
ports in the literature on adult HCM patients [3,5-8] have
not described HCM patients with prominent atrial enlar-
gement on ECG as in the cases reported here. In con-
secutive 24 adult HCM patients (age, 36 - 80 years; 16
males) that the author has experienced (Table 1), left
atrial enlargement defined by Morris index [4] was fre-
quent, but the magnitude of the P-wave abnormality was
minimal when compared to the two juvenile HCM pa-
tients described in this report. It may be that adult HCM
patients usually develop atrial fibrillation [9,10] before
reaching such prominent bi-atrial enlargement on ECG.
Comparative study between juvenile and adult HCM
patients using a large sample size is required to confirm
the possibility of inherent predisposition to extreme atrial
enlargement/hypertrophy causing prominent P-waves on
ECGs in juvenile HCM patients.
Table 1. Summary of ECG findings in 24 adult HCM patients.
Sinus rhythm without history
of heart failure (N = 12)
Paroxismal atrial fibrillation and/or
history of heart failure* (N = 12) Total (N = 24)
Left atrial enlargement 1 (8%) 6 (50%) 7 (29%)
Morris index (mV-sec) 0.12 0.07 ± 0.03 (0.04 - 0.12) 0.08 ± 0.03 (0.04 - 0.12)
Amplitude (mV) 1.5 1.17 ± 0.41 (1 - 2) 1.21 ± 0.39 (1 - 2)
Duration (sec) 0.08 0.06 ± 0.02 (0.04 - 0.08) 0.06 ± 0.02 (0.04 - 0.08)
Right atrial enlargement 0 0 0
Repolarization abnormalities (ST-T) 10 (83%) 11 (92%) 21 (88%)
Left ventricular hypertrophy 7 (58%) 5 (42%) 12 (50%)
Right ventricular hypertrophy 2 (17%) 0 2 (8%)
Abnormal Q waves 1 (8%) 3 (33%) 5 (21%)
Conduction disturbance
Left bundle branch block 0 2 (17%) 2 (8%)
Left bundle branch block 1 (8%) 2 (17%) 3 (13%)
* = ECG recording during sinus rhythm.
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H. Kataoka / Open Journal of Internal Medicine 2 (2012) 31-33 33
Figure 2. Standard 12-lead ECG of Case No. 2.
Based on the ECG findings, this case report suggested
that inherent predisposition to extreme enlargement and/
or hypertrophy may exist in atrial myocardium in juve-
nile HCM patients.
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