J Vet Clin 26(2) : 155-159 (2009)

155

Pentalogy of Fallot with Subaortic Stenosis in a Mixed Dog

Seungkeun Lee*, Jin-Ung Jang and Changbaig Hyun1

School of Veterinary Medicine, Kangwon National University, Chuncheon 201-100, Korea*Korea Animal Clinic, Cheongju 361-829, Korea

(Accepted : March 10, 2009)

Abstract : A 2-year-old female mixed dog (weighing 4.3 kg) was referred to the Veterinary Teaching Hospital, KangwonNational University, with primary complaints of exercise intolerance, nocturnal coughing and heart murmur. Diagnosticstudies revealed bi-lateral holosystolic murmurs on phonocardiogram, over-riding aorta, pulmonic stenosis, ventricularseptal defect, atrial septal defect, biventricular hypertrophy, and subaortic stenosis in diagnostic imaging studies. Basedon the diagnostic findings, pentalogy of Fallot (POF) with subaortic stenosis (SAS) was tentatively diagnosed. Thisis the first case report of POF complicated with SAS in a dog in Korea.

Key words : congenital heart defect, pentalogy of Fallot, subaortic stenosis, dog.

Introduction

Tetralogy of Fallot (TOF) is a congenital cardiac malfor-

mation consisting of ventricular septal defect (VSD), pulmonic

stenosis (PS), right ventricular hypertrophy, and dextroposi-

tion of the aorta with septal override (overriding aorta). Pen-

talogy of Fallot (POF) is a more complex congenital cardiac

malformation characterized by TOF with patent ductus arteri-

osus (PDA) and/or atrial septal defect (ASD). The important

prognostic factors are the severity of the VSD and PS.

The overall prevalence of congenital heart disease in dogs

has been estimated to be 27 per 4000, in contrast, the preva-

lence of TOF in dogs has been estimated to be only 1 per

4000 (7). However, the actual prevalence rate may be higher

than that previously reported, because severely affected ani-

mals commonly die at a young age before having been thor-

oughly examined (3).

POF with aortic stenosis has been rarely reported in both

veterinary and human medicine. Recent human genetic stud-

ies revealed mutations in the ZFPM2 (zinc finger protein

multitype 2) caused some familial and sporadic cases of TOF

(9). In Keeshond dogs with TOF, genetic etiology with auto-

somal recessive inheritance was proposed (8). Further study

also found TOF in Keeshonds had oligogenic etiology (11).

This case report described a rare case of TOF complicated

with ASD (so-called as POF) and SAS in a mixed dog.

Case

A 2-year-old intact female mixed breed dog (weighing

4.3 kg) was presented to the Veterinary Teaching Hospital,

Kangwon National University with primary complaints of

exercise intolerance, nocturnal coughing and heart murmur.

On the phonocardiogram, a grade V/VI holosystolic mur-

mur was heard at the left apical, left basal and right paraster-

nal region of the heart with a precordial thrill. Although the

electrocardiogram (ECG) recorded at a month before presen-

tation showed a sinus rhythm with left ventricular hypertro-

phy (R wave amplitude; ~3.5 mV) (Fig 1A), the ECG

recorded at presentation found a left bundle branch block

(LBBB) (Fig 1B). No significant abnormalities were found

from hematology and blood chemistry analyses.

Radiographic studies of the thoracic cavity revealed a gen-

erally enlarged cardiac silhouette (vertebral heart scale, 11.4),

right ventricular enlargement, distended caudal vena cava,

under-circulation of the pulmonary vasculature, and displace-

ment of the cardiac apex to the left (Fig 2).

The 2-dimensional (2-D) echocardiography revealed an

overriding and dextropositioned aorta (Fig 3C), stenotic right

ventricular outflow tract (systolic jet outflow velocity of

5.1 m/sec; pressure gradient 107 mmHg) (Fig 3A, and 5A),

biventricular hypertrophy (Fig 3D), perimembraneous ven-

tricular septal defect (Fig 3B), and os secundum atrial septal

defect (Fig 4A). Color and continuous Doppler echocardio-

graphy confirmed a left-to-right shunt flow from the ventric-

ular septum. Doppler studies at the ventricular septum level

revealed the direction of the flow was the left to right under

3.0 m/sec of maximal peak velocity (Fig 5B), indicating that

the septal defect was large. Doppler studies at the level of the

atrial septum also revealed the flow direction was the left to

right under 0.7 m/sec of maximal peak velocity, indicating

large septal defect (Fig 5D). In addition, the hyperechoic sub-

valvular structure with systolic turbulent jets was observed in

the left ventricular outflow tract (LVOT). The maximal

velocity of systolic jets was over 4.6 m/sec (the pressure gra-

1Corresponding author.E-mail : hyun5188@kangwon.ac.kr

156 Seungkeun Lee, Jin-Ung Jang and Changbaig Hyun

dient between LVOT and aorta was over 87 mmHg), indicating

moderate subaortic stenosis (Fig 4B and 5C). Based on these

findings, the dog was diagnosed as a case of POF with SAS.

The dog was managed by diltiazem (0.5 mg/kg TID), furo-

semide (3 mg/kg BID), enalapril (0.5 mg/kg BID) and low

sodium diet (Hill’s h/d). The dog is currently survived and

regularly visited for the evaluation of progression.

Discussion

In veterinary medicine, the occurrence of TOF is rare and

that of POF, a syndrome of TOF with concurrent ASD or

PDA, is much rare. Recently, TOF with ASD has been

reported (6). Clinical features of sole TOF account from right

side heart failure from PS and right ventricular hypertrophy,

and cyanosis and polycythemia from right-toleft shunt from

VSD and overriding aorta. Long-term survival from this dis-

ease is rare in veterinary medicine, because of multiple car-

diac defects subsequent with hypoxic injuries to multiple

vital organs. However, this case of dog survived for more

than 2 years, despite multiple cardiac defects.

Based on echocardiographical studies, this dog has a large

VSD (shunt flow velocity: < 3 m/sec) (5) and a large secundum

ASD (shunt flow velocity: < 1 m/sec). In general, if shunt

Fig 1. Electocardiogram. A: The electrocardiogram (ECG) recorded at a month before presentation showed a sinus rhythm with left

ventricular hypertrophy (R wave amplitude; ~3.5 mV). B: The ECG recorded at presentation found a left bundle branch block (LBBB).

Fig 2. Thoracic radiography. A: The lateral projection of radiography revealed a markedly enlarged cardiac silhouette (vertebral heart

scale, 11.4) with right ventricular enlargement, distended caudal vena cava and undercirculation of the pulmonary vasculature. B: The

ventro-dorsal projection of radiography revealed a marked cardiomegaly with the left displacement of the cardiac apex and under-

circulation of the pulmonary vasculature.

Pentalogy of Fallot with Subaortic Stenosis in a Mixed Dog 157

velocity is higher than 3 m/sec, it means a hole (defects) in

septum is smaller, so that the flow velocity through the hole

is greatly increased. The severity of ventricular outflow tract

obstruction (e.g. PS or SAS) determines the pressure gradi-

ent across the stenotic area. In general, the pressure gradient

under 60 mmHg (jet flow velocity < 4 m/s) is graded as mild,

while 60-100 mmHg (jet flow 4-5 m/sec) and over 100 mmHg

(> 5 m/sec) is graded as moderate and severe, respectively. In

this dog, the peak velocity at right and left ventricular out-

flow tract was 5.1 m/s (pressure gradient 107 mmHg) and

4.6 m/s (pressure gradient 87 mmHg), respectively, indicat-

ing that this dog had severe PS and moderate SAS. Due to

obstruction in both ventricular outflow tracts and subsequent

pressure overload, the left and right ventricular concentric

hypertrophy was obvious in this dog (Table 1).

TOF causes systemic arterial hypoxia due to the mixing of

oxygenated and deoxygenated blood in the left ventricle via

the VSD and preferential flow of the mixed blood from both

Fig 3. A: Short axis view at the level of pulmonic valve showing stenotic right ventricular outflow tract (arrow). B: Color Doppler

image of the right parasternal four-chamber long axis view showing a shunt flow in interventricular septum (perimembraneous ven-

tricular septal defect). C: Long axis LV outflow view showing dextro-positioned aorta (overriding aorta; arrow). D: M-mode echocar-

diography at the level of left ventricle showing marked biventricular hypertrophy.

Fig 4. A: Color Doppler image of the right parasternal four-chamber long axis view showing interatrial communication (secundum

atrial septal defect). B: Four chamber long axis view showing hyperechoic structure (arrow) causing left ventricular outflow tract

obstruction (subaortic stenosis).

158 Seungkeun Lee, Jin-Ung Jang and Changbaig Hyun

ventricles through the aorta because of the obstruction to

flow through the pulmonary valve. Therefore, the primary

symptom of TOF is lower blood oxygen saturation with or

without cyanosis from birth or developing in the early stage

of disease progression. However, in this dog, no cyanosis and

hypoxia were evident from the presentation and furthermore,

no evidence of right-to-left shunt was detected in echocardio-

graphic studies. Probably it was because the concurrent left

ventricular obstruction might maintain higher pressure status

in the left ventricle over the right ventricle, even though the

right ventricular pressure was increased due to PS. Since the

left-to-right shunt was maintained due to left ventricular pres-

sure overload from concurrent subaortic stenosis, the cyano-

sis with polycythemia, which was characterized features of

TOF, was not observed through clinical course of this dog.

Interestingly, the concurrent SAS in this dog might retard the

disease progression and interfere with the development of

cyanotic heart disease.

Therapeutic directions of TOF are generally to minimize

risk of the acute setting of hypercyanosis using oxygen ther-

apy, to reduce ventilatory drive using alpha-adrenergic ago-

nist and to relieve the pain using analgesics. Although palliative

surgical techniques (e.g. Blalock-Taussig shunt, Pott proce-

dure, Waterston shunt) are available in human medicine

(2,4,10), no such surgical treatment has been attempted in

veterinary medicine. However, in this dog, the oxygen ther-

apy for minimizing cyanotic crisis was not necessary to

attempt, since this dog did not show cyanosis. Therapeutic

directions for this dog were mainly focused on reducing ven-

tricular pressure overload and increasing diastolic function

Fig 5. A: The systolic jet outflow velocity of 5.1 m/sec at the right ventricular outflow tract (pressure gradient 107 mmHg) indicating

severe pulmonic stenosis. B: Left to right direction of shunt flow in the interventricular septum at peak velocity under 3.0 m/sec, indi-

cating a large ventricular septal defect. C: The systolic jet outflow velocity of 4.6 m/sec at the left ventricular outflow tract (pressure

gradient 87 mmHg) indicating moderate subaortic stenosis. D: Left to right direction of shunt flow in the interatrial septum at peak

velocity under 0.7 m/sec, indicating a large atrial septal defect.

Table 1. Echocardiographic dimensions of this case

LVIDda) (mm) LVIDs (mm) LVPWd (mm) LVPWs (mm) IVSd (mm) IVSs (mm) EF (%) FS (%)

Reference (1) 27.4±5.2 16.0±4.7 5.4±1.7 7.9±1.6 6.2±1.7 10.2±2.2 20-70 28-40

Case 14.7 9.7 12.8 15.3 7.2 8.1 67 34.01a)IVSd: interventricular septal thickness at diastole, LVIDd: left ventricular dimension at diastole, LVPWd: left ventricular posterior wallthickness at diastole, IVSs: interventricular septal thickness at systole, LVIDs: left ventricular internal dimension at systole, LVPWs: leftventricular posterior wall thickness at systole, EF: % ejection fraction, FS: % fractional shortening.

Pentalogy of Fallot with Subaortic Stenosis in a Mixed Dog 159

using calcium channel blockers (e.g. diltiazem), and on reduc-

ing atrial volume overload using diuretics (e.g. furosemide)

and angiotensin converting enzyme inhibitors (e.g. enalapril).

The clinical outcome from this therapy was reasonably suc-

cessful.

In conclusion, this case report described a rare case of

compound congenital heart defects from TOF complicated

with ASD and SAS in a mixed dog. To our best knowledge,

this is the first case report of POF complicated with SAS in

Korea.

Acknowledgments

This study was supported by a research fund from Korean

Research Foundation (KRF-2008-331-E00369).

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10. Tchervenkov CI, Hill S, Del Duca D, Korkola S. Surgical

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잡종견의 대동맥하 협착증을 동반한 팔로오증

이승근*·장진웅·현창백1

*청주고려동물병원, 강원대학교 수의학부대학

요 약 :암컷 잡종견 (2년령, 체중 4.3 kg)이 운동불내성, 야행성 기침, 심잡음을 주증상으로 강원대학교 수의학부대학

부속동물병원에 내원하였다. 전수축기성 잡음이 양쪽에서 청진되었으며, 영상진단에서 대동맥 변위, 폐동맥협착, 심실

중격결손, 심방중격결손, 양심실의 비대, 대동맥하협착이 확인되었다. 이러한 소견들을 바탕으로 대동맥하 협착증을 동

반한 팔로오증으로 진단을 내렸다. 이는 국내에서 진단된 대동맥하 협착증과 복합된 팔로오증의 첫 번째 증례보고이다.

주요어 :선천성 심장질환, 팔로오증, 대동맥하협착증, 개.