Uncovering the Hidden Pressure Chamber

Symptoms

An 8-year-old female spayed mixed-breed dog, presented for clinical evaluation after showing pronounced lethargy, severe systemic fatigue, and a distinctly elevated, rapid heart rate during physical examination.

Further abdominal assessment revealed noticeable fluid distension alongside a palpably enlarged, structurally abnormal spleen, signalling widespread systemic strain requiring urgent diagnostic imaging.

Visualisation

Imaging Modalities Used: Transthoracic Echocardiography (M-Mode, B-Mode, Spectral Doppler) and Abdominal Ultrasonography.

The Ultrasound Revelation

  • Right Atrial Mass: A 1.5  x 1.8 cm lesion originating on the external right atrial wall.

  • Hemopericardium & Tamponade: Severe fluid buildup in the pericardial sac (aspirate confirmed pure blood) creating cardiac tamponade physiology.

  • Pseudohypertrophy: Severe underfilling of both left and right ventricles leading to secondary wall thickening (IVSd 1.3 cm, LVFWd 2.36 cm) and elevated ejection fraction (95%).

  • Abdominal Findings: Concurrent enlarged, heterogeneous spleen paired with abdominal ascites, pointing toward a primary cardiac hemangiosarcoma with potential splenic involvement or multicentric disease.

Next Steps:

  • Perform emergency therapeutic pericardiocentesis to relieve tamponade pressure and restore cardiac output.

  • Conduct a full abdominal ultrasound further to evaluate splenic architecture and stage for metastatic spread.

  • Submit pericardial fluid for cytology, keeping low diagnostic sensitivity in mind.

  • Discuss surgical options (pericardiectomy/splenectomy) and prognosis with the owner.

Important Lessons

  • Recognise Pseudohypertrophy: Cardiac tamponade severely reduces preload, causing collapsed chamber dimensions that can easily mimic hypertrophic cardiomyopathy or true myocardial thickening.

  • Look Beyond the Chest: Finding hemopericardium should always prompt a complete abdominal search particularly inspecting the spleen to rule out multicentric hemangiosarcoma.

Mixed Breed Dog