J Cardiol 2000; 36: 45 – 48

Hypertrophic Cardiomyopathy With
Dominant Hypertrophy in the Right
Anterobasal Region of theVentricular Septum: A Case Report
Taku

MATSUBARA, MD

MasaruYAMAZOE, MD

Motomasa

KIMURA, MD＊Tomoyuki

HORI, MD

Kazuyuki

OZAKI, MD

Katsuharu

HATADA, MD

Yoshifusa

AIZAWA, MD, FJCC

Abstract ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
A 62-year-old man was referred to our hospital for investigation of abnormal electrocardiography find. Terminalings. The mean frontal plane QRS axis was directed toward the right superior quadrant（−125 °）S waves were present in all 3 bipolar standard leads and an R wave in lead aⅤR. RS complex was seen inlead Ⅴ1 and deep S waves in leads Ⅴ2−Ⅴ6. Left ventricular hypertrophy associated with asymmetrical septal hypertrophy was suspected based on transthoracic echocardiography, but the echocardiographic quality
was poor. Magnetic resonance imaging revealed hypertrophic cardiomyopathy with massive wall thickening involving the right anterobasal region of the ventricular septum. Magnetic resonance imaging may provide useful information about the distribution of ventricular myocardial hypertrophy in patients withhypertrophic cardiomyopathy and unusual electrocardiography findings.
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Key Words■ Cardiomyopathies, hypertrophic■ Magnetic resonance imaging■ Electrocardiography

INTRODUCTION
Standard 12-lead electrocardiography
（ECG）
may
show a great variety of abnormalities in patientswith hypertrophic cardiomyopathy 1−3）. ECG is
important for the first diagnostic screening of thisdisease, but new diagnostic modalities, such as
magnetic resonance（ MR）imaging, MR spectroscopy and positron emission computed tomography, have greatly contributed to the diagnosis of
hypertrophic cardiomyopathy and to the interpretation of its morphological and pathophysiologicalfeatures4）. We describe a case of hypertrophic car-diomyopathy with unusual ECG findings, and discuss the significance of the changes in relation to
the MR imaging findings.
CASE REPORT
A 62-year-old man was referred to our hospitalfor investigation of abnormal ECG findings（Fig.
1）. He had no history of cardiac or pulmonary disease. Chest radiography showed the cardiac silhouette was normal. Transthoracic echocardiography
could not clearly show the details of the heart in theparasternal echocardiographic window because oflimitation of the window by the adjacent lung tis-──────────────────────────────────────────────＊新潟大学医学部 第一内科，
放射線科 : 〒 951−8510 新潟県新潟市旭町通り 1−754
The First Department of Internal Medicine, ＊ Department of Radiology, Niigata University School of Medicine, Niigata
Address for reprints : MATSUBARA T, MD, The First Department of Internal Medicine, Niigata University School of Medicine,
Asahimachi-dori 1−754, Niigata, Niigata 951−8510
Manuscript received December 9, 1999 ; revised March 3, 2000 ; accepted March 6, 200045

46

Matsubara, Yamazoe, Kimura et al

Fig. 1 Electrocardiographic findings
The mean frontal plane QRS axis is directed toward the right superior quadrant（−125 °）. Terminal S waves are present inall 3 bipolar standard leads and an R wave
is seen in lead aⅤR. An RS complex is seenin lead Ⅴ1, and deep S waves are evident inⅤ2−Ⅴ6.

Fig. 2 Rest-gated single photon emission computed
tomography scan with technetium-99 m tetrofosmin
The basal short-axis slice of the left ventricle shows
uptake of technetium-99 m tetrofosmin is increased in
the right anterobasal region of the ventricular septum.

sue, but the apical view showed slight indicationsof the presence of left ventricular hypertrophy associated with asymmetrical septal hypertrophy. The
difficulty in the echocardiographic evaluation
seemed to be due to the muscular physique of thepatient. Single photon emission computed tomography with technetium-99 m tetrofosmin revealed
myocardial hypertrophy localized in the anterobasal
portion of the ventricular septum（Fig. 2）. MR
imaging was performed to evaluate the ventricular
hypertrophy accurately, and revealed hypertrophic
cardiomyopathy with massive wall thickening
involving the right anterobasal region of the ventricular septum（Fig. 3）. This finding was considered to be consistent with the unusual ECG
changes. The patient has remained clinically stable
and asymptomatic, and his ECG findings have also
remained unchanged for the past 5 years.
DISCUSSION
Standard 12-lead ECG shows abnormal findingsin 85% to over 90% of patients with hypertrophic
J Cardiol 2000; 36: 45 – 48

Localized Hypertrophy of Anterobasal Septum

47

Fig. 3 Magnetic resonance image showing ventricular hypertrophy with asymmetrical septal hypertrophy
The right anterobasal region of the ventricular septum is markedly thickened and protrudes into the rightventricular outflow tract（arrow）.
RV ＝ right ventricle ; RA ＝ right atrium ; LV ＝ left ventricle ; LA ＝ left atrium.

cardiomyopathy1−3）. Deviation of the mean frontal
plane QRS axis superiorly and to the right is rare,
but occurs in 2% of patients with hypertrophic cardiomyopathy1）. The significance of such uncommon QRS axis deviation is still unclear. Wigle etal.5）reported the effects of ventriculomyotomy in 3
patients with hypertrophic cardiomyopathy andabnormal hypertrophy was located mainly in theanterior end of the septum and the immediately
adjacent left ventricular anterior wall. The septal
hypertrophy may have resulted in dominance ofanterosuperior over posteroinferior electrical forcesthat could be altered by septal incision. This patient
had localized hypertrophy of the anterobasal regionof the septum, so the electrical force of septal activation was spread to the right, anteriorly and inferiorly, and produced a small q wave in leads Ⅰ andaⅤL, a small r wave in leads Ⅱ, Ⅲ and aⅤF, an R
wave in the right precordial chest leads, and a qwave in the left precordial leads. The QRS complexes caused by the spread of excitation throughthe 2 ventricles were considered to be modified by
the localized hypertrophy of the anterobasal septum, which would cancel the normal frontal QRS
axis in the limb leads and produce deep terminal Swaves in all limb leads（except aⅤR）and in the precordial leads（except Ⅴ1）.
J Cardiol 2000; 36: 45 – 48

Echocardiography is widely accepted as a useful
tool for the diagnosis of hypertrophic cardiomyopathy, but hypertrophy of a localized region of thebasal ventricular septum is an incidental echocardiographic finding in most cases6）. Maron et al.7）
observed hypertrophy limited to the anterior septum（type I）in 12（10%）of 125 patients with hypertrophic cardiomyopathy. The prevalence of normal
ECG in the patients with this type I was significantly greater than in the other 3 morphologic types2）.
However, in the majority of their type I patients7）,
hypertrophy was not limited to the ventricular septum and extended to the apical portion of the left
ventricle. Belenkie et al.6）emphasized that hypertrophy localized to the basal septum infrequentlyrepresented part of the spectrum of hypertrophic
cardiomyopathy. We speculate that the unusual
ECG findings in the present case reflect the massive
bulge of myocardium localized in the right anterobasal region of the ventricular septum.
The advantages of MR imaging over echocardiography include a large field of view that provides
more accurate diagnostic information in almost allpatients 8,9）. The present case of the use of MR
imaging to identify hypertrophic cardiomyopathy
with dominant hypertrophy in the right anterobasal
region of the ventricular septum indicates that MR

48

Matsubara, Yamazoe, Kimura et al

imaging can yield additional insight into the features of hypertrophic cardiomyopathy in relation to
要

specific ECG abnormalities which might be impossible to clarify by echocardiography.
約

心室中隔基部の右室側前方に著しい肥大を伴った肥大型心筋症の 1 例松 原

琢山 添優

木村元政

尾崎和幸

畑田勝治

相澤義房

堀知 行

症例は 62 歳の男性で，心電図異常の精査のため当科を紹介され受診した．平均前頭面 QRS 電気軸は右上方に向かい（−125 °），3 つすべての双極標準誘導で S 波を，また aⅤR 誘導では R 波を認めた．胸部誘導Ⅴ1 は RS 型を示し，深い S 波をⅤ2−Ⅴ6 で認めた．経胸壁心エコー図で非対称性中隔肥厚を伴う左室肥大の存在が疑われたが，エコー図での描出は不良であった．磁気共鳴画像で心室中隔基部の右室側前方に，著しい限局的な肥厚を伴った肥大型心筋症であることが明らかになった．
特異な心電図所見を伴う肥大型心筋症において，その心室の肥大部位に関する情報を得るうえで，磁気共鳴画像検査は有用と思われた．

J Cardiol 2000; 36（1）: 45−48

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J Cardiol 2000; 36: 45 – 48