A 7-Year-Old MN Boston Terrier With Grain Free Diet-Related Systolic Dysfunction: Our Case Of the Month July 2019
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.
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.
For more information regarding the FDA's report click this link: FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy