pISSN 1598-298X / eISSN 2384-0749 J Vet Clin 32(4) : 343-346 (2015)
http://dx.doi.org/10.17555/jvc.2015.08.32.4.343
343
Right-to-left Shunting Ventricular Septal Defect in a Dog
Sookyung Yun, Boeun Kim, Hwayoung Youn, Mincheol Choi and Junghee Yoon1
College of Veterinary Medicine and the Research Institute for Veterinary Science, Seoul National University, Seoul 151-742, Korea (Accepted: June 24, 2015)
Abstract : A 4-year-old castrated male Dachshund was presented with a chronic history of dyspnea and cyanosis.
Complete blood count revealed marked polycythemia with a hematocrit of 79.7%. Thoracic radiographs showed mild right-sided cardiac enlargement. Echocardiography showed a large ventricular septal defect in the left ventricular outflow tract region just proximal to the aortic valve. On Doppler echocardiography, right-to-left shunt flow through the defect was found and confirmed by contrast echocardiography. Based on these diagnostic findings and clinical signs, the dog was diagnosed as right-to-left shunting ventricular septal defect. Phlebotomy and oxygen supplement were performed, but the dog died the day after presentation.
Key words : dog, ventricular septal defect, Eisenmenger’s syndrome, echocardiography.
Introduction
Ventricular septal defect (VSD) is a congenital heart dis- ease resulting from incomplete development of the membra- nous or muscular ventricular septum and it accounts for about 7.5% of all congenital heart defects in dogs (13). It is often classified by the location of the defect: perimembranous, supracristal, muscular, and inlet. Among them, the most com- mon form of VSD is high perimembranous type, which are located in the left ventricular outflow tract (LVOT) just prox- imal to the aortic valve. In the other way, it can be divided into nonrestrictive and restrictive types according to hemody- namic status (15).
Cardiac catheterization and angiography is used to con- firm the diagnosis and is performed when contemplating sur- gical correction for the defect (4,15). However, this procedure is usually unnecessary since the advent of echocardiography and is sometimes undesirable if a patient is at high-risk for general anesthesia.
The aims of this report are to describe an uncommon case of a large VSD attended with Eisenmenger's syndrome in a dog and its diagnosis by echocardiography.
Case
A 4-year-old castrated male Dachshund, weighing 8.2 kg was presented at the Seoul National University Veterinary Medical Teaching Hospital with a chronic history of dysp- nea and cyanosis. Syncope has recently occurred on excite- ment for 2 months.
On physical examination, the dog was consistently cyan- otic and tachypneic. Heart rate was 110 beats/min and heart
murmur was indistinct due to loud respiratory sound. Femo- ral pulse was weak, so fluid therapy were immediately per- formed (normal saline 100 ml/h, Voluven® 5 ml/kg bolus for 30 minutes) and then systolic blood pressure was measured at 115 mmHg.
Electrocardiography showed wandering pacemaker, inverted QRS wave on lead II, and 190 degree of cardiac axis, sug- gesting right ventricular hypertrophy (Fig 1). Complete blood count revealed marked polycythemia with a hematocrit of 79.7% (reference range: 35.0-55.0%; hemoglobin 28.3 g/dl, reference range: 10.0-18.0 g/dl) and leukocystosis (21990 /ul, reference range: 6000-17000 /ul). Serum biochemistry pro- files were unremarkable.
Thoracic radiographs showed mild right-sided cardiac enlargement and overall pulmonary hypovascularity (Fig 2A, B).
On 2-dimensional echocardiographic examination, a large defect (approximately 1 cm) was seen in the LVOT region just proximal to the aortic valve (Fig 3A). Furthermore, dilated right atrium and ventricle with right ventricular hypertrophy, flattening of interventricular septum, paradoxical septal motion during systole and diastole, dilated main pulmonary artery without any stenotic lesion were observed, suggesting right ventricular volume and pressure overload with pulmonary hypertension.
On Doppler echocardiography, bi-directional shunt flow through the defect was revealed on right parasternal short axis 5 chamber view and right-to-left shunting was con- firmed by spectral Doppler studies with a peak velocity of 1.52 m/s from right to left ventricle direction, which is higher than left to right direction (Fig 3B, 4). On contrast echocar- diography (bubble study), 3 ml agitated saline was injected rapidly through the cephalic vein. Microbubbles entered directly the left ventricle through the defect from the right ventricle and were observed in abdominal aorta immediately after injection.
1Corresponding author.
E-mail: heeyoon@snu.ac.kr
344 Sookyung Yun, Boeun Kim, Hwayoung Youn, Mincheol Choi and Junghee Yoon
Based on these diagnostic findings and clinical signs, the dog was diagnosed as perimembranous type VSD with Eisenmenger’s syndrome (right-to-left shunting). Although phlebotomy and oxygen supplement were performed, the dog died the day after the presentation at home.
Discussion
Ventricular septal defect (VSD) is a relatively common congenital heart disease in dogs as in human. The clinical signs and the prognosis of VSD largely depend on the size and location (type) of the defect (6,8,9,15). With a typical, small restrictive VSD, the shunting was hemodynamically
insignificant, which means it may not create any measurable volume overload of the chambers and/or pulmonary circula- tion. In a large non-restrictive VSD, however, left-to-right shunting of blood causes increased pulmonary blood flow and sustained pulmonary arterial hypertension (6,16,19). Over the time, shear stress on pulmonary vascular wall causes active pulmonary vasoconstriction and gradual pulmonary microvascular remodeling (pulmonary vascular disease) (7,19).
Consequently, pulmonary vascular resistance increases and if pulmonary arterial pressure approached the systemic level or even overcome, shunt direction would be bidirectional or reversed (right-to-left). At this stage, the patient may clini- cally manifest dyspnea, cyanosis and secondary polycythemia due to systemic hypoxemia. This is called Eisenmenger’s syndrome (ES), the final and irreversible stage of VSD (1,17,19). In humans, the large VSD (greater than 1.5 cm in diameter) is responsible for about 10% of all VSD patients and the likelihood developing ES in these group is about 50%, whereas the defect is small (about less than 3 mm in diameter) in about 75% of all patients, and only 3% of them may develop ES (8,19).
Interestingly, according to a recent retrospective study (13), VSD tends to be observed in conjunction with another car- diac defect in almost half of the cases (48%) and usually with pulmonary stenosis (65%). The authors could not find another cardiac anomalies including PS in this patient. Car- diac catheterization and angiography could be used to con- firm isolated VSD, however, it was thought to be irrational because of the patient’s poor conditions and obvious clinical Fig 1. Electrocardiogram of the dog with right to left shunting ventricular septal defect shows presence of S-wave in lead I, II & III with right QRS axis deviation (190 degree), suggesting right ventricular hypertrophy.
Fig 2. Right lateral (A) and ventrodorsal (B) thoracic radio- graphs from the dog with a large VSD. Although there is no obvious cardiomegaly, relatively round right side heart and underperfused pulmonary vasculature are observed.
Fig 3. Flattening of interventricular septum during systole and diastole, suggesting right pressure overload (A). Main pulmonary artery is dilated compared to the aorta (B).
Right-to-left Shunting Ventricular Septal Defect in a Dog 345
signs reflecting shunt reversal.
Echocardiography provides not only detailed imaging of cardiac anatomy but also methods for estimating the pulmo- nary to systemic flow ratio (Qp/Qs), the interventricular pres- sure gradient across the VSD, the pressure within the chambers of the hearts and pulmonary arterial pressure, shunt direction when combined with Doppler and contrast echocar- diography (2,10,14,18). They are essential information for making a decision on therapeutic approaches in VSD patient (1,15). In this case, maximal velocity of shunting blood flow was 1.52 m/s, then interventricular pressure was only about 9 mmHg. Therefore, the dog was diagnosed with severe pul-
monary hypertension as pulmonary artery systolic pressure was 124 mmHg.
In summary, this case report describes clinical and diag- nostic imaging characteristics of a large VSD with Eisen- menger’s syndrome in a dog. It is considered that echo- cardiography is the useful tool for diagnosing the cardiac defect and it is necessary for evaluating the prognosis in VSD patients.
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Fig 4. 2-dimensional (A) and color Doppler echocardiographic examination (B) with left parasternal long axis 4 chamber view. Right atrium and ventricle are dilated and even larger than left chambers. A large perimembranous VSD (arrow) is observed (A) and blood flow passes through the defect on color Doppler examination (B).
Fig 5. Color and continuous wave Doppler examination in right parasternal short axis 5 chamber view. Right-to-left shunt flow is observed with a peak velocity of 1.52 m/s from right ventricle to left ventricular outflow tract direction.
Fig 6. Contrast echocardiography in left apical long axis 4 chamber view (A). Air bubbles (arrows) passed through the defect from right ventricle to left ventricle. Air bubbles (arrows) were seen in abdominal aorta right after injecting the agitated saline (B).
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개에서 발생한 우-좌 단락 심실 중격 결손 증례
윤수경·김보은·윤화영·최민철·윤정희1
서울대학교 수의과대학
요 약 : 4년령의 중성화된 수컷 Dachshund가 만성적인 호흡곤란 및 청색증을 주증으로 내원하였다. 혈액검사에서 헤 마토크리트 79.7%의 심각한 적혈구증가증이 확인되었다. 흉부 방사선 영상에서는 경도의 우심 종대가 관찰되었다. 심 초음파 검사에서 좌심실유출로 대동맥판막 근위부에서 큰 심실 중격 결손이 확인되었으며, 도플러 검사에서 이 결손 을 통한 우-좌 션트가 확인되었으며 조영 심초음파를 통하여 최종적으로 확진되었다. 이러한 진단적 결과 및 환자의 임상증상을 바탕으로 환자는 우-좌 단락 심실 중격 결손증으로 진단되었다. 사혈 및 산소 공급을 실시하였으나 환자는 내원 다음날 집에서 사망하였다. 본 증례보고에서는 심초음파를 통한 우-좌 단락 심실 중격 결손증의 진단을 서술하였다.
주요어 : 개, 심실중격결손, 아이젠멘거 증후군, 심초음파
