Left atrial rupture

From Dog
Severe endocardiosis in a Cavalier King Charles Spaniel, a leading cause of left atrial rupture[1]

Left atrial rupture is an uncommon but serious heart disease of dogs characterized by rupture of the atrial wall of the heart[2].

In dogs, this is usually associated with severe degenerative changes associated with mitral valve endocardiosis, which causes atrial jet lesions that weaken and eventually split the endocardial lining of the heart, usually around the leaflets of the mitral valve or its supporting chordae tendinae[3], leading to hemorrhage through the myocardium and into the pericardial sac.

Although endocardiosis is a leading contributor to this phenomenon, other disease processes may induce the same cardiac trauma, including neoplasia, heartworm disease, fungal infections and valvular endocarditis[4].

A breed predisposition has been reported in the Cavalier King Charles Spaniel[5] and Shetland Sheepdog[6], where rupture of the chordae tendinae is a common cause of congestive heart failure.

Left atrial rupture usually results in elevated left atrial pressure, which leads to pulmonary hypertension and pulmonary effusion. Within the heart itself, mitral valve rupture results in cardiac tamponade, pericardial effusion and pericardial thromboembolism[7], all critically threatening to diastolic relaxation of heart muscle.

In rare cases, this condition can lead to development of secondary atrial septal defects[8].

Clinically affected dogs often present with sudden onset of heart-related symptoms of weakness, poor femoral pulses, cyanosis and respiratory distress[9]. There is usually a history of chronic heart disease in most patients.

On auscultation, a bounding sound is heard over the left apex of the heart. Radiographs usually show left atrial enlargement, enlarged left ventricle and pulmonary veins, increased pulmonary interstitial density, pulmonary effusion and air bronchograms.

Electrocardiograms usually show varying degrees of premature ventricular complexes and atrial fibrillation, with widened P and R waves[10].

Diagnosis is usually confirmed on ultrasonography, demonstrating a thickened, enlarged, and irregular valvular leaflet of normal echogenicity.

A differential diagnosis would include other causes of pericarditis, caval syndrome and neoplasias (chemodectoma, paraganglioma, rhabdomyosarcoma, hemangiosarcoma, lymphoma and mesothelioma).

Some patients may be treated conservatively with sedation and analgesia, as well as furosemide to alleviate pulmonary edema. The use of ACE inhibitors such as benazepril is controversial as they neither alleviate cardiac tamponade or lessen the severity of intra-atrial pressure[11].

In life-threatening cases, pericardial cystocentesis is required to relieve the tamponade[12].

References

  1. University of Cambridge
  2. Komitor DA (1976) Left atrial rupture. Infrequent sequel to chronic microvalvular insufficiency. Vet Med Small Anim Clin 71(5):620-621
  3. Jugdutt BI (1987) Left ventricular rupture threshold during the healing phase after myocardial infarction in the dog. Can J Physiol Pharmacol 65(3):307-316
  4. Smith AN et al (2000) Left ventricular outflow tract to left atrial fistula associated with endocarditis in a dog. J Am Anim Hosp Assoc 36(2):133-136
  5. Serres F et al (2007) Chordae tendineae rupture in dogs with degenerative mitral valve disease: prevalence, survival, and prognostic factors (114 cases, 2001-2006). J Vet Intern Med 21(2):258-264
  6. Reineke, EL et al (2008) Left atrial rupture in dogs: 14 cases (1990–2005). J Vet Emerg Crit Care 18:158–164
  7. Prosek R et al (2003) What is your diagnosis? Pericardial effusion with a clot in the pericardial space likely caused by left atrial rupture secondary to mitral regurgitation. J Am Vet Med Assoc 222(4):441-442
  8. Peddle GD & Buchanan JW (2010) Acquired atrial septal defects secondary to rupture of the atrial septum in dogs with degenerative mitral valve disease. J Vet Cardiol 12(2):129-134
  9. Sadanaga KK et al (1990) Echocardiography and surgery in a dog with left atrial rupture and hemopericardium. J Vet Intern Med 4(4):216-221
  10. Merck Veterinary Manual
  11. Ishikawa T et al (2010) The effect of angiotensin-converting enzyme inhibitors of left atrial pressure in dogs with mitral valve regurgitation. J Vet Intern Med 24(2):342-347
  12. Kurt S & Kovacevic A (2012) Atrial rupture and pericardial effusion as a complication of chronic mitral valve endocardiosis. Schweiz Arch Tierheilkd 154(9):397-401