Cardiac tumors are rare in dogs, with an overall incidence rate of only 0.19% (18,21). Among the various types of cardiac tumors, hemangiosarcoma (HSA) is the most common, accounting for 69% of all identified cases according to histologic type (17,18).

Canine cardiac HSA is a highly malignant tumor that arises from pluripotent bone marrow progenitor cells (7,19). Although there was once a hypothesis that it originates from the vascular endothelium, recent evidence supports its bone marrow origin (4,21). The tumor is highly metastatic and can spread to distant organs through hematogenous routes, with the lungs being the most commonly affected site (4). At the time of diagnosis, most cases of HSA have already metastasized (4,11).

Canine cardiac HSA (cHSA) can result in various mild to severe clinical symptoms (17), with pericardial effusion being the most common (17,21). cHSA can also cause right-sided congestive heart failure, decreased preload, and even tamponade. These conditions can result in numerous symptoms such as tachycardia, pulse deficits, weak femoral pulses, ascites, tachypnea/dyspnea, exercise intolerance, lethargy, and acute collapse (11,17,21).

The recommended treatment for cardiac HSA involves surgical removal of the primary tumor in combination with chemotherapy (11,21). Excision of the right atrial mass and subtotal pericardiectomy can offer palliative relief for recurrent cardiac tamponade (4). However, pericardiectomy alone does not prolong survival (15). Studies have shown that adjuvant chemotherapy with doxorubicin after tumor removal significantly increases the median survival time in dogs with cHSA, with reported survival times of up to 318 days after right atrial mass resection and chemotherapy (1,11,21).

The use of mechanical stapling devices in veterinary surgery has become increasingly common in recent years, and the gastrointestinal anastomosis stapler (GIA) is one such tool that has shown promise in various procedures (4,16,20). While the use of staples for cardiac tumor resection has not yet been extensively documented in the veterinary literature, we report a case of one dog with cardiac hemangiosarcoma that underwent resection using a GIA stapler. This case report describes the identification and surgical removal of a hemangiosarcoma located in the right auricle of a neutered 10-year-old dachshund. This case report aimed to evaluate the feasibility and safety of using a stapler for the resection of cardiac tumors in dogs.

A 10-year-old, 9.65 kg, castrated male dachshund was referred to the surgical department at the Veterinary Teaching Hospital of Chungnam National University for the removal of a mass involving the right heart auricle. The patient had a history of multiple pericardiocenteses. Four days before referral, the patient presented to a local hospital with lethargy, poor appetite, and vomiting. Elevated liver enzyme levels, anemia, and pericardial effusion were identified, and pericardial puncture was performed once 4 and 3 days prior.

On the day of referral to Chungnam National University, the patient was ambulatory but lethargic. The heart rate was 180 bpm, which indicated mild sinus tachycardia, with a systolic blood pressure of 160 mmHg and a respiratory rate of 36 bpm. A complete blood count revealed mild thrombocytopenia and normal red blood cell and white blood cell (WBC) counts. The serum biochemical profile revealed mildly increased CRP levels. Plain thoracic radiography revealed generalized cardiomegaly with a VHS of 11.4. 2D-Echocardiography showed a well-demarcated, solid mass close to the original mass with considerable size, a maximum diameter of 3.6 cm, and heterogeneous, highly echogenic parenchyma (Fig. 1A). The mass was found in the auricle, widely attached to the pericardium, and caused pericardial effusion with cardiac tamponade (Fig. 1B). Right atrium collapse was observed in the dilation phase, consistent with the discovery of cardiac tamponade.

Figure 1. Preoperative diagnostic imaging: transthoracic echocardiography (A, B) and computed tomography (C, D). (A) Modified right parasternal long-axis four-chamber view showing the large lesion (asterisk). The mass is sizeable, measuring up to 3.6 cm in maximum diameter, with heterogeneous, highly echogenic parenchyma. (B) At the level of the right parasternal shot-axis view, a well-demarcated, solitary lesion (asterisk) with a nearly round shape is clearly visualized. (C, D) The transverse and sagittal images reveal a heterogeneous lesion (asterisk) situated between the cranial vena cava and the right atrium. The presence of severe pericardial effusion can be observed. Eff, pericardial effusion; CrVC, cranial vena cava; CdVA, caudal vena cava; RA, right atrium; RV, right ventricle; LV, left ventricle.

The left ventricular internal dimension at end-diastole (LVIDd) was 15.7 mm, and the left ventricular internal dimension at end-systole (LVIDs) was 7.5 mm; both were below the normal range (range: 26.38-28.28 mm and 15.79-17.44 mm, respectively). The left ventricular posterior wall at end-diastole (LVPWd) was 15.2, and the left ventricular posterior wall at end-systole (LVPWs) was 19.4 mm; both were thicker than the normal range (range: 5.83-6.86 mm and 9.59-10.88 mm, respectively). These findings suggest left ventricular pseudohypertrophy secondary to cardiac tamponage. No cases of aortic, pulmonary, or mitral regurgitations were observed. Abdominal ultrasonography revealed a 20.3 × 17.8 cm hypoechoic splenic nodule. Based on the echocardiogram results and overall assessment, the likelihood of a splenic tumor co-occurring with a right atrial tumor was the highest.

No findings were suggestive of metastasis to other abdominal organs or lymph nodes. For specific diagnosis of the masses and metastatic evaluation, thoracic and abdominal computed tomography (CT) was performed. In the thoracic window, a large amount of soft tissue-dense fluid was observed between the heart and pericardium, with irregular margins, showing heterogeneous enhancement. A mass of approximately 20.2 × 12.8 × 11.5 mm was identified in the vicinity of the right atrium (Fig. 1C, D). The spleen was slightly enlarged and extended towards the front of the bladder. Two low-density and homogeneous parenchymal circular masses were observed on the ventral side of the head and trunk of the spleen, measuring 23 × 21 × 19 mm and 30 × 26 × 26 mm, respectively.

Surgical treatment was planned on the day of CT diagnosis because of the risk of cardiac tamponade. The patient was pre-administered midazolam (Midazolam_® Bugwang Pharm CO, Korea, 0.2 mg/kg IV) for sedation and anxiolysis. Anesthesia was induced with alfaxalone (Alfaxan_®, Jurox Pharm CO, Australia, 3 µg/kg IV) and maintained with isoflurane inhalation. Cephazolin (Cephazolin_®, Jongeundang Pharm CO, Korean, 22 mg/kg IV) was injected as a prophylactic antibiotic every 90 min. The surgery involved a 4-5 right-sided thoracotomy, subtotal pericardiectomy, and removal of the mass attached to both the auricle and pericardium.

The SpO2 level dropped to as low as 60% during surgery but was maintained between 60-90% through continuous bagging. After pericardiectomy, the SpO2 level gradually increased and recovered to 95%. Resection of the mass was performed using an articulated linear cutting stapler (ENDOPATH-ETS-FLEX-45_® standard, Johnson & Johnson, USA) (Fig. 2). After resection, minor bleeding occurred from the stump, which was controlled with an additional cruciate suture using prolene 6-0. Once no additional bleeding or oozing was confirmed, a thoracostomy tube was inserted, and the surgical field was closed in the usual manner. The patient underwent a stable splenectomy for histological examination. Postoperatively, the patient was monitored for cardiorespiratory function during hospitalization in an oxygen cage; the patient recovered well.

Figure 2. Resection of the right auricular cardiac hemangiosarcoma. (A) The tumor located in the right atrial auricle (asterisk) was exposed through a fourth intercostal space incision. (B) The tumor (asterisk) was excised using an articulated surgical stapler. Cr, cranial; Cd, caudal; D, dorsal; V, ventral; RV, right ventricle.

On the 2nd postoperative day, the patient exhibited spontaneous appetite and normal fluid intake, and all vital signs were stable. However, the thoracostomy tube revealed a milky hemorrhagic fluid. Despite no significant findings on chest and abdominal radiographs, fluid analysis revealed a triglyceride level > 2.5 times the normal level, suggestive of a chylothorax. On the 3rd day, the milky appearance of the fluid disappeared, and the drainage amount decreased to 0.07 mL/kg/hr, leading to the removal of the drain. On the 5th day, intravenous fluid and remifentanil constant-rate infusion were discontinued. While scheduled for discharge on the 7th day, the patient experienced white foamy vomiting and nasal discharge of white fluid in the early morning, with a body temperature of 38.3°C and a heart rate of 183 bpm, indicative of mild cyanosis and panting. Thoracic radiography revealed a severe alveolar pattern throughout the right lung. A complete blood count revealed mild leukocytosis, lymphocytosis, and thrombocytopenia. The serum biochemical profile indicated a substantial increase in C-reactive protein (CRP) levels, which were eight times the normal range. Subsequently, cardiopulmonary arrest occurred, and despite 20 min of cardiopulmonary resuscitation, the patient did not survive. The cause of the patient’s death could not be determined because of the sudden onset of the event and rapid deterioration of symptoms. Autopsy could not be performed because the guardian did not provide consent following the patient’s death.

Histopathological examination revealed several distinct characteristics (Fig. 3). The spleen presented with a large nodule comprising a moderately cellular, infiltrative mass of spindle cells arranged in streams and anastomosing vascular channels, consistent with splenic hemangiosarcoma. The myocardium of the right auricle was similarly disrupted by a moderately cellular, unencapsulated mass showing several features of metastatic hemangiosarcoma, including blood-filled channels lined with spindle cells, along with a mitotic count of three. The pericardium displayed regional expansion by a moderate cellular mass resembling the previous masses with a mitotic count of one, supporting the diagnosis of a presumed metastatic hemangiosarcoma.

Figure 3. Histopathology of the myocardium of the right auricle (A, B). Histopathology shows features of metastatic hemangiosarcoma, characterized by a moderately cellular, unencapsulated mass with blood-filled channels lined by spindle cells.

This paper reports the successful resection of cardiac hemangiosarcoma in a dog using a surgical stapler. Despite repeated thoracocentesis, due to the continuous pericardial effusion, the right atrium tumor was resected to reduce the risk of cardiac tamponade and subsequent sudden death. At the time of echocardiography and CT scan, a considerable amount of pericardial effusion was already confirmed, and there was no option other than surgical resection or total pericardiectomy to improve the patient’s subsequent quality of life. Fortunately, on imaging tests, the tumor was limited to the right atrium; therefore, it was possible to resect the tumor to an extent that minimally affected cardiac function.

Cardiac HSA has a very poor prognosis, with a median survival time (MST) of only 7.1-12 days when left untreated (11,21). However, several studies have shown that surgical resection alone can provide an MST of 42-86 days, whereas surgery with chemotherapy can increase MST to 116-189 days (11,19,21). In cases where incomplete resection or metastasis is present, the addition of chemotherapy can still provide a significant increase in survival time, with a reported survival time of 177 and 318 days, respectively (1,4). These findings demonstrate the benefits of surgical resection and chemotherapy in the treatment of cardiac HSA. Although there is limited research on radiation therapy, a recent publication highlighted its advantages, including being well-tolerated by patients, lowering the frequency of pericardiocentesis, and providing an MST of 79 days (14).

The self-cutting stapling device used in cardiac hemangiosarcoma resection is useful for tumor resection because of its stability, convenience, and associated shorter surgical time and fewer complications (4,15,20). Stainless steel staples in cardiac surgery provide effective closure with minimal tissue trauma, hemorrhage, and inflammatory response while minimizing the risk of air embolism when compared to manual suturing (10,20). Additionally, the use of articulated devices is advantageous compared to the thoracoabdominal stapler due to the possibility of adjusting the stapler angle in difficult-to-operate situations where tumors are attached to organs with unique anatomical characteristics (5,12,15). Moreover, in the case of cardiac tumors, handling the heart is difficult because the heart beats dynamically, and excessive handling can affect the hemodynamic function of the heart, leading to instability of vital signs during anesthesia (3,8); further, fragile tissues can easily rupture due to tumor invasion and local inflammation (6,13). Therefore, adjusting the angle of the device’s articulation is more useful for tumor resection than adjusting the tumor at various angles, as it ensures a safer surgery.

In this case, the patient developed a chylothorax on the 2nd postoperative day. The incidence of chylothorax after thoracic surgery is approximately 0.42% in human medicine (20). The cause of postoperative chylothorax is unclear, but it is assumed to be caused by damage to the thoracic duct during surgery; damage to lymphatic vessels around the ascending aorta, cranial vena cava, or pulmonary artery trunk; or by increased pressure in the cranial vena cava (2,9). Most patients (83.3%) recover with conservative treatments such as low-fat diets and chest tube drainage (21). In this case, the amount of chyle in the drain decreased significantly, the milky appearance disappeared within 2 days of chylothorax occurrence, the related treatment was terminated, and the chest tube was removed.

The likely cause of death of this patient was aspiration pneumonia. Although the patient had an elevated white WBC until postoperative day 5, no specific radiographic findings or respiratory-related clinical symptoms were observed. Despite this, sudden clinical respiratory symptoms appeared on the 7th day, and an increase in pulmonary opacity was confirmed, leading to the assumption that respiratory problems were responsible for the patient’s death. The increase in CRP and decrease in WBC count were attributed to overwhelming inflammation in the body, whereas nasal discharge indicated upper respiratory tract infection. Although the patient had a good appetite during hospitalization, forced feeding to meet daily caloric requirements may have contributed to aspiration. It is possible that acute pneumonia progressed because of silent aspiration before the onset of clinical symptoms of the respiratory system.

The current study documents a removal of a hemangiosarcoma found in the right atrium of a dog, using an articulated surgical stapler. The articulated surgical stapler used in this case offers a distinct advantage over traditional staplers by allowing more precise access in accordance with the heart’s movements, thereby greatly reducing the risks of inadequate resection or cardiac damage. Consequently, it facilitates successful surgeries and can potentially decrease the overall duration of the operation.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2022R1C1C1010464).

Conceptualization: D.-H.K; Data curation: W.-J.K., K.-M. K. and W.-J.L.; Formal analysis: W.-J.K.; Investigation: W.-J.L, C.-H.M.; Supervision: D.-H.K; Writing - original draft: W.-J.K.; Writing - review & editing: H.-B.L., S.-M.J, D.-H. K. All authors have read and agreed to the published version of the manuscript.

The authors have no conflicting interests.