July's Case of the Month- 2022

July 2022 Case of the Month - Left Atrial Rupture in a Chihuahua

Patient Information 

Age: 12 years

Gender: Spayed Female

Breed: Chihuahua

Weight: 10.3 pounds

History

Presented for echocardiogram due to heart murmur since July 2021, 5 month history of coughing, and recent finding of ascites. An abdominocentesis was performed 2 days prior to the echocardiogram and the patient had been started on Furosemide 10mg orally every 12 hours. 

Echocardiogram procedure

Tipper was bright, alert, and responsive at the beginning of her procedure. A mild amount of pericardial effusion was initially noted at the beginning of the scan. About halfway through the echocardiogram, the volume of pericardial effusion rapidly increased, the patient became acutely lethargic and the heart rate dropped. Mask O2 was delivered and a pericardiocentesis was performed due to the patient’s clinical decline and concern for cardiac tamponade. Only about 4mL of non-clotting blood was obtained from pericardiocentesis, however the patient clinically improved following the procedure and there was visible improvement of the effusion on ultrasound. Referral to a facility with 24 hour monitoring was recommended, but ultimately declined. Tipper was clinically stable at the conclusion of the echocardiogram and pericardiocentesis.

Abnormal Echocardiogram Findings

• The mitral valve is diffusely thickened especially the anterior leaflet with prolapse into the left atrial lumen during systole.

•  There is severe eccentric mitral regurgitation present.

• There is severe left atrial enlargement (LA:Ao 3.0, normal under 1.6). 

• There is moderate left ventricular dilation (normalized LV diastolic diameter 2.0, normal under 1.7). 

• Mild right atrial and ventricular dilation (subjective).

•  Mild thickening of the tricuspid valve with mild TR and the velocity (3.8 m/s) is consistent with moderate pulmonary hypertension (57 mmHg). 

• There is a moderate pericardial effusion which does not appear to be causing tamponade. The echocardiogenic character of this effusion changes from hypoechogenic to having a more soft tissue appearance. This is consistent with an acute bleed and clot formation.

Diagnosis

• Chronic degenerative valve disease causing severe mitral and mild tricuspid regurgitation. The LA is significantly dilated indicating a high risk for clinical signs going forward. 

•   Moderate pulmonary hypertension is noted, which is likely secondary to chronic LA pressure elevation.   

• However there is a pericardial effusion likely secondary to left atrial rupture.   Blood pressure should be assessed and if normal/high, therapy should be started such as an ACE inhibitor then amlodipine.  The reduced systemic pressure will decrease the left atrial pressure and hence likelihood of continued left atrial breed.

Recommendations

Apart from blood pressure reduction, there is no specific treatment for left atrial rupture.  Pericardiocentesis should only be performed if there is cardiac tamponade. It frequently recurs.

With this degree of left heart changes, the risk for spontaneous congestive heart failure is elevated and cardiac supportive medications are indicated as below.  Pimobendan 0.2 – 0.3 mg/kg by mouth every 12 hours should be given to slow progression.  Assessment of progression in the future will help predict long term outcome, however prognosis is guarded at this stage (late B2). Evidence for ACE inhibitors is equivocal at this stage.  Unfortunately, the patient will always be at risk for recurrent CHF, development of arrhythmias/LA tear, syncope and/or sudden death in the future.

Close monitoring for development of associated clinical signs (development of increased breathing rate, labored breathing, exercise intolerance, cough or collapse episodes) is recommended. Monitoring of sleeping breathing rates is recommended as the best way to screen for CHF at home with less than 35 breaths/minute being normal.

Elective anesthesia is not advised, as there is high risk for complication such as heart failure.

Omega fatty acid supplementation and mild salt restriction may also be of some long term benefit.

A screening BP is recommended as hypertension makes mitral regurgitation worse.

A recheck echocardiogram is recommended in 4-6 months to screen for progression, sooner if clinical signs arise. If the results are similar, the recheck interval can be increased to 9 – 12 months.

Follow up 

Tipper was started on Pimobendan (1.25mg orally twice daily), Furosemide (10mg orally twice daily), and Enalapril (2.5mg orally twice daily). 

The week following Tipper’s echocardiogram, pericardiocentesis, and initiation of her cardiac medications,
Tipper’s owner reported she was feeling much better and acting her normal self. 

Two months later, Tipper’s cardiac disease is still being managed, however ascites was noted again at that time, so her primary care veterinarian started her on Spironolactone in addition to her other cardiac medications. No signs of cardiac tamponade have been reported. 

Special thanks to Montpelier Veterinary Hospital and Simon Swift, MA, VetMB, CertSAC, DipECVIM-CA (Cardiology), MRCVS with DVMStat  for their collaboration on this case.