Introduction

Cardiac tamponade (CTP) is the most common pericardial emergency in dogs.¹ It is frequently secondary to neoplastic or idiopathic causes.¹ When pericardial effusion (PE) with CTP is identified, it requires a percutaneous pericardiocentesis (PP). However, PE may relapse over time.¹ Repeating PP may not be the best treatment option in dogs requiring frequent drainage because of potential complications (arrhythmias, laceration of the coronary artery, infections, or cardiac perforation) and serial anesthetic requirements.² Adjunctive treatment options for heart base tumors, such as ectopic thyroid carcinomas, include chemotherapy, surgical resection, or radiotherapy combined with different surgical options to manage recurrent PE, such as pericardiectomy (via thoracoscopic or thoracotomy approach) or percutaneous balloon pericardiotomy.^3–6 If these procedures are not possible, an alternative palliative technique for managing recurrent PE may be considered. This report aims to present the placement of a subcutaneous pleural access port^ab in the pericardial cavity as an alternative palliative technique to manage recurrent PE in two dogs with a cardiac mass presumed to be an ectopic thyroid carcinoma.

Case Report

Case 1

A 13 yr old neutered female springer spaniel, weighing 13.5 kg, was referred to Hospital Veterinario Puchol for evaluation of ascites. On initial physical examination, the dog was mildly depressed with a grade V/VI left apical holosystolic murmur detected with concomitant weak femoral pulses and moderate abdominal distension. An echocardiogram revealed severe PE with evidence of CTP, and a heterogeneous, irregular, 5.7 × 6.1 cm mass was identified originating from the heart base (Supplementary Video I). Severe mitral valve thickening, consistent with degenerative mitral valve disease, and moderate left atrial and ventricular enlargement were also noted (ACVIM stage B2). A fine-needle aspirate of the mass and PP were performed under general anesthesia. A total of 180 mL of hemorrhagic fluid was retrieved from the pericardial sac. The dog developed tachypnea and a mixed respiratory pattern during recovery. Thoracic radiographs were performed and revealed pulmonary edema, most consistent with left-sided congestive heart failure, likely due to degenerative mitral valve disease and increased preload following successful pericardiocentesis. Treatment with furosemide (1 mg/kg IV q 1 hr) and pimobendan (0.15 mg/kg IV q 12 hr) was started. Clinical and radiographic signs of congestive heart failure resolved after initiation of medical therapy. Cytology of the mass was consistent with an epithelial neoplasm. Thyroid carcinoma was suspected based on the echocardiographic appearance, location, and cytologic results. The owners declined pericardiectomy or pericardiotomy and only agreed to initiate chemotherapy treatment. Toceranib phosphate (35 mg per os [PO], 2.6 mg/kg, three times weekly) was started, but relapse of PE with CTP occurred 3 days later, requiring repeat PP. A total of 5 PPs were performed over the next 4 wk. Surgical intervention was again declined, and instead, the owner consented to a novel treatment involving percutaneous placement of a fenestrated catheter port device into the pericardial space to control PE. The patient was anesthetized and placed in left lateral recumbency. A 14-gauge cannula^c was inserted into the pericardial space to drain PE from the right hemithorax, in the fifth intercostal space at the level of the costochondral junction, under ultrasonographic guidance. The amount of PE was estimated based on a volume of fluid enough to facilitate pericardial access and ensure the patient remained stable during the procedure (absence of CTP). The cannula stylet was removed, and a 50 cm guidewire was inserted through the cannula (Figure 1A). The cannula was then removed and a 10.5 Fr Peel-Away introducer^d, flushed with sterile saline, was placed over the guidewire (Figure 1B). Finally, the dilator and guidewire were removed. A 9-French round tip fenestrated silicone tube^a was placed into the pericardial site (Figure 1C) under fluoroscopic and ultrasonographic guidance, ensuring that the fenestrations remained completely inside the pericardiac sac (Supplementary Video II). At that point, the Peel-Away introducer was removed (Figure 1D). The silicone tube was placed over a guidewire^e, supporting and improving catheter movement. A small skin incision was performed 10–15 cm dorsally and caudally to the introducer to allow for the placement of the subcutaneous silicone reservoir port^a. The silicone tube was passed subcutaneously toward the skin incision and connected to the reservoir port. Thoracic radiographs confirmed the correct device placement (Figure 2A). The patient was discharged the day after with amoxicillin/clavulanic acid (22 mg/kg PO q 12 hr) for 7 days. Cardiac treatment with furosemide (1 mg/kg PO q 12 hr) and pimobendan (0.25 mg/kg PO q 12 hr) was continued. The port was re-examined 7 days later, and 40 mL of hemorrhagic fluid was removed using the specific port needle^a (Figure 2B). Chemotherapy treatment was modified, and carboplatin (250 mg/m²) was administered in four sessions, with intervals of 20–30 days, alternating between IV and intrapericardial administration. Pericardial effusion was noted to decrease progressively, and the patient was reported to be feeling well at each visit. Correct catheter placement was assessed by ultrasound guidance and by proper fluid drainage when PE was present. The catheter remained patent, and no complications associated with the implant (arrhythmias, infection, or pleural effusion) were identified during ultrasound and electrocardiographic monitoring. The last visit was performed 145 days after port implantation. There was no significant reduction in cardiac size of the neoplasm in the echocardiogram, and the left cardiac enlargement due to mitral valve disease continued to progress. Pericardial effusion was minimal, and 38 mL of pericardial fluid was removed. The patient was lost to follow-up in the following months; the owner reported that the patient died of recurrent pulmonary edema at the referral center 3 mo later after the final visit at the authors’ institution.

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Discussion

A permanent subcutaneous pleural access port in the pericardial space was an alternative technique used to manage recurrent malignant PE in two dogs, whose owners declined more invasive treatment. Percutaneous pericardiocentesis is usually the first-line treatment in emergency care to relieve the symptoms associated with PE and CTP.¹ However, it is not a definitive treatment for recurrent PE or specific diseases such as heart tumors.^3,4 For this reason, intrapericardial catheter placement has been recently described as a safe and effective alternative to PP, allowing repeated drainage for longer periods and reducing potential complication associated with multiple PPs. However, this device requires hospitalization and nursing monitoring because the catheter is placed externally on the skin surface.^7,8 In human medicine, PE aspiration through the pericardial catheter is performed by repeat aspirations with a syringe or with a continuous aspiration system and is maintained until the PE volume is less than 25 mL/day.⁹ The main advantage of prolonged and continuous drainage is that it achieves adhesion between the two layers of the pericardium, preventing the recurrence of PE. This goal can be facilitated by instilling sclerosing agents.⁹ The implantation of a percutaneous catheter in the pericardial space with subcutaneous aspiration port, avoiding external placement, for the management of a malignant pericardial effusion (cardiac hemangiosarcoma) was described recently in a case report, while we performed the second case.¹⁰ The catheter used in this case was a vascular access port designed for long-term infusions and injections; however, it had not been tested as a drainage catheter in cavities. Long-term patency could be compromised because of catheter conformation (e.g., distal end hole), but the catheter was used for pericardial effusion drainage and intrapericardial chemotherapy administration without complications.¹⁰ A commercially available device specifically designed for thoracic drainage is available in veterinary medicine.^11,12 A fenestrated radio-opaque silicone tube is placed in the thorax and connected to a drainage hub located in a subcutaneous pocket, allowing repeated puncture.^11,12 The device is available in two sizes, for larger dogs (9-French) and for small dogs and cats (7-French). We adapted the pleural drainage system for use in the pericardial space for the management of recurrent PE in these two cases. Device size selection was performed based on the manufacturer’s recommendations (dog dimensions) and port placement technique as previously described for pleural location but adapting to pericardial access. The main goals were to avoid the risks described with repeated PP or traditional surgical options and offer a less invasive option to the owners. Furthermore, the pericardial catheter with subcutaneous port could provide an internalized drainage option with lower risk of dislodgment or the need for monitoring compared with an externalized system. The procedure was performed in both cases without any relevant intraoperative or postoperative complications. The most common complication described in previous intrapericardial catheter is the development of arrhythmias.^7,8 No arrhythmias were identified during the procedure or at follow-up visits. However, despite electrocardiographic monitoring being performed during the visit, continuous Holter monitoring was not performed in either case. Other complications associated with drainage catheters could include obstruction with clots or debris. However, the risk of obstruction with the permanent subcutaneous pleural port was reportedly low when the device was used for draining different types of thoracic effusions.^11,12 Veterinary literature does not provide specific indications for the maintenance of percutaneous drainage ports or pericardial catheters (e.g., flushing with heparinized saline or 0.9% sodium chloride), unlike in vascular systems. For this reason, routine flushing was not performed in our cases.¹³ The device remained patent at each recheck appointment, and no other complications (i.e., infection, migration) were observed in our cases. Perioperative prophylaxis was used in both procedures. However, the decision not to administer antibiotics in a clean surgical procedure should be considered in future cases, based on new recommendations and practices in veterinary medicine.¹⁴ Pericardial effusion production was low in both cases after subcutaneous access port implantation. A combination of specific oncologic treatment and the potential benefit of pericardial port placement likely controlled the production of PE in both cases. The presumed cytologic diagnosis in our two cases was an ectopic thyroid carcinoma, being the first-line treatment option was toceranib phosphate. However, inadequate disease control was suspected, so a rescue therapy with carboplatin was started. Intracavitary chemotherapy (pleural or peritoneal) has been described to treat malignant cavitary neoplasm such as mesothelioma and carcinomatosis. Still, there is limited literature regarding intrapericardial cavity administration and treatment indications for other types of neoplasia, such as heart base tumors.^15,16 This chemotherapy administration option was used in the first case and no intracavitary-related complications were observed. Intrapericardial chemotherapy administration could be considered for future cases using the pericardial drainage system described in this report. However, we still lack information on the efficacy and safety of this route. Finally, this procedure requires a minimal postprocedural recovery or hospitalization time and allows easy pericardial drainage during follow-up visits, potentially enabling owners to manage PE at home.

Conclusion

This report describes a feasible palliative technique for managing PE associated with heart base masses in two patients whose owners declined surgical treatment. Long-term studies are needed to evaluate long-term efficacy, complication rate, and indications of this procedure in animals with PE, including those with other cardiac neoplasms and causes of PE.

The authors confirm that informed consent was obtained from the pets’ owners. The patients were managed according to the standard of care described in the JAAHA policy statement.