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A 7-Year-Old MN Boston Terrier With Grain Free Diet-Related Systolic Dysfunction: Our Case Of the Month July 2019

Keywords

History

Clinical Signs

Exam Findings

Images

Initial ECHO: Decreased systolic function. Fractional shortening 23%.
Initial ECHO: Eccentric MR.
Initial ECHO: Well demarcated tumor associated with the aortic root; 2.5cm x 2.74cm. No impingement on great vessels is noted.
Recheck ECHO: Improved systolic function. Fractional shortening 37%.
Recheck ECHO: Eccentric MR.
Recheck ECHO: Well demarcated tumor associated with the aortic root; 3.29x 2.7cm. The tumor remains benign in nature (ie no impingement on blood flow), however the measurements are mildly increased.
Recent studies have increased public awareness of a possible link between certain diets (grain free, boutique brand, exotic ingredient) and systolic dysfunction in some dogs. While causation remains largely unknown, instituting a simple diet change can typically lead to dramatic improvement in cardiac function and clinical signs in those affected. Often clinically silent, many affected dogs can benefit from supportive medications such as Pimobendan depending on severity seen on ultrasound. Other dogs on these diets are found to have normal cardiac structure and function, with no medications necessary or cause for clinical concern. Screening is a valuable tool to understand risk and help improve outcome for any dog on a grain free, boutique brand or exotic ingredient diet. 
Below is an ultrasound case of a small breed dog with valve disease on a grain free diet that was found to have significant cardiac dysfunction (uncommon in this signalment) which improved with simply a diet change. 
Many thanks to Andi Parkinson, BS, RDMS of IntraPet Imaging (Baltimore, MD) for providing the beautiful images for this interesting case and to our very own Maggie Machen Lamy, DVM, DACVIM (Cardiology) for her detailed interpretation.

History

Initial Evaluation: The patient presented for examination due to coughing more recently. Was at swim therapy after MPL surgery and therapist heard new heart murmur. PE grade 2/6 heart murmur, harsh lung sounds, moderate effort. The patient is on a grain free lamb and lentil diet. Current Medications: Lasix 20mg PO BID-TID (3-5mg/kg/day), Pimobendan 5mg in AM and 2.5mg in PM.

Ultrasound findings and recommendations from initial echocardiogram are as follows: Chronic degenerative valve disease causing moderate mitral and mild tricuspid regurgitation. Moderate LA dilation is noted, which is concerning for progression in the future. In this small breed with CVD, the systolic dysfunction is striking and unusual. Possible causes include secondary to grain free diet (taurine deficiency), infarct to the myocardial wall, or simply primary dysfunction. Given the recent information on grain free diets, first step is either submit a taurine level and/or change the diet and supplement taurine. Taurine-deficiency is the sole cause of treatable dysfunction, although this patient will still have underlying CVD. Certainly continuing Pimobendan is also recommended, for cardiac support. With moderate LA dilation, there is some risk for CHF, however it is unclear if the Lasix initiated was necessary at this phase. Use of an ACE-I is recommended for long term anti-fibrotic benefit. Further investigation into the cough is recommended through screening chest radiographs, as potentially simple cough suppression may benefit QOL. Finally, a cardiac tumor associated with the aortic root is also identified. The most likely tumor type given this location and the history is a chemodectoma, however other differentials cannot be ruled out. Chemodectomas are often incidental findings, only causing clinical signs if blood flow is obstructed, pericardial effusion occurs, or a metastatic lesion causing systemic issues. The prognosis with cardiac chemodectomas is fair, with a MST of 1-2 years. The limiting factor is often hemorrhage into the pericardium. Other sequelae include impingement of cardiac blood flow secondary to tumor growth, or metastasis to the thorax or abdomen. At this time this is considered an incidental finding, and is unlikely to be causing an clinical issues due to it’s small size.

Plan: Consider screening chest radiographs as discussed. Consider hydrocodone if needed. If no h/o CHF or current concern, consider wean to lower dose: Give 15mg PO q12h. Continue Pimobendan as prescribed. Institute Benazepril 5mg PO q12h. Consider submit taurine levels and/or supplement taurine twice daily. Change to commercial non-grain free diet.

Patient presented 8 months later for lethargy. Current medications: Benazapril 5mgs twice daily, Pimobendan 5mgs a.m. and 2.5mgs p.m., Lasix 10mgs p.m. Blood pressure was 160mmHg. A recheck echocardiogram was performed.

Image Interpretation

8 month follow up evaluation: Chronic degenerative valve disease causing moderate mitral and mild tricuspid regurgitation persists. Stable moderate LA dilation is noted, and the LV dimension is unchanged.  Most importantly, the LV function has improved (30-35% compared to 23-27% previously). Given that the diet was changed (taurine not supplemented), this would imply a causation link in hindsight with the grain free diet which is great news. Continue Pimobendan and Benazepril as prescribed, however no clear indication for Lasix therapy at this time and this can be discontinued. The tumor remains benign in nature (ie no impingement on blood flow), however the measurements are mildly increased. Continued monitoring is advised. No clear cardiac cause of lethargy is identified given overall improvement.
Plan: Discontinue Lasix therapy. Continue PImobendan and Benazepril as prescribed. Recheck echocardiogram recommended in 6 months to continue to screen for progression, sooner if problems arise.

Outcome

Omega fatty acid supplementation and mild salt restriction may also be of some long term benefit. Monitor for development of a cough, labored breathing, exercise intolerance or collapse episodes. Serial monitoring of SRRs is recommended as the best way to screen for progression towards CHF at home.

Comments

For more information regarding the FDA's report click this link: FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy

Videos

Initial ECHO: Left ventricle.
Initial ECHO: Eccentric MR.
Initial ECHO: Well demarcated tumor associated with the aortic root; 2.5cm x 2.74cm. No impingement on great vessels is noted.
Recheck ECHO: Left ventricle.
Recheck ECHO: eccentric mitral vlave.
Recheck ECHO: Well demarcated tumor associated with the aortic root; 3.29x 2.7cm. The tumor remains benign in nature (ie no impingement on blood flow), however the measurements are mildly increased.