Introduction
Dilated cardiomyopathy (DCM) in cats is a serious cardiac condition that has seen historical fluctuations in prevalence, notably linked to taurine deficiency in the 1980s. Following the identification of this link, taurine was widely added to commercial cat foods, leading to a significant reduction in DCM cases. However, recent attention has been drawn to a potential association between certain diets and DCM in both dogs and cats, with reports to the U.S. Food and Drug Administration (FDA) highlighting diets that are grain-free or contain pulses like peas, chickpeas, and lentils.
While the primary focus has been on dogs, where studies indicate that cardiac function can improve with diet changes and taurine supplementation, the situation in cats warrants further investigation. Anecdotal reports from veterinary cardiologists suggest a potential increase in feline DCM cases. This study aims to survey cardiologists about their recent experiences with feline DCM and to retrospectively review individual cases, with a particular focus on diet, echocardiographic findings, taurine status, and outcomes following dietary interventions. Our hypothesis is that there may be a perceived increase in DCM diagnoses, a correlation with high pulse (high PL) diets, and that outcomes might be influenced by diet changes, even in cases not linked to taurine deficiency.
Animals, Materials, and Methods
Part One: Cardiologist Survey
A comprehensive electronic survey was distributed to board-certified veterinary cardiologists. The survey gathered information on their general approach to managing cats with DCM, including practices related to measuring taurine levels, supplementing taurine, and changing diets. It also inquired about their caseload of feline DCM cases over the preceding two years and their perception of any changes in prevalence. Cardiologists were further asked about cases suspected of having a nutritional etiology and their outcomes.
Part Two: Retrospective Case Review
Cardiologists who expressed willingness to participate in the retrospective portion of the study were invited to submit data from cats recently diagnosed with DCM. Cases from two major small animal hospitals were also included. Medical records were meticulously reviewed for inclusion criteria, which focused on specific echocardiographic measurements indicative of DCM, such as left ventricular internal dimension at end-systole and fractional shortening, alongside subjective assessment of global left ventricular systolic dysfunction. Cases with specific hypertrophy criteria or prior diagnoses of hypertrophic cardiomyopathy were excluded.
Data collected for each eligible cat included signalment, clinical signs, physical examination findings, initial echocardiogram results, and any measured taurine and N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations. Crucially, detailed diet history at the time of diagnosis and any subsequent diet changes were recorded. Outcomes, including survival time, were carefully documented. Diets were classified as either “low pea/lentil” (low PL) or “high pea/lentil” (high PL) based on the presence of peas, pea fractions, or lentils within the first 10 ingredients listed on the product’s label.
Data Analysis
Statistical analyses were performed to compare various parameters between diet groups and to assess factors influencing survival time. This included descriptive statistics, Shapiro–Wilks tests for data distribution, Kaplan–Meier curves and log-rank tests for survival analysis, and Cox proportional hazards analysis for multivariable modeling.
Results
Part One: Cardiologist Survey Insights
Of the 52 completed surveys, a majority of cardiologists reported that they “always” or “sometimes” measure taurine concentrations (59%) and supplement taurine (80%) in cats diagnosed with DCM, regardless of documented deficiency. Most also indicated that they “always” or “sometimes” change the diet of cats with DCM (65%). While most cardiologists did not perceive an increase in feline DCM cases over the past two years (77% reported numbers had not changed), 15% did report an increase. Furthermore, 38% of cardiologists reported seeing at least one cat with suspected diet-associated DCM in the last two years, with 15% of these cases showing documented taurine deficiency. Some cardiologists (25%) also reported cases of suspected diet-associated DCM that showed clinical or echocardiographic improvement after a diet change, even without documented taurine deficiency.
Part Two: Retrospective Case Study Findings
A total of 37 cats met the inclusion criteria for the retrospective study. Twenty cats were categorized into the low PL diet group, and 14 into the high PL diet group, with three having incomplete diet histories. No significant differences were observed between diet groups in terms of age, sex, breed, body condition score, or initial echocardiographic measurements. However, cats in the high PL diet group had a significantly higher body weight at diagnosis (P = 0.049).
Taurine concentrations were measured in only 13 cats, with only two (both in the low PL diet group) found to have plasma taurine levels below the reference range. No cats had documented low whole blood taurine concentrations. Elevated NT-proBNP concentrations were noted in all 10 cats for which this biomarker was measured.
Regarding outcomes, a significant difference in survival time was observed. Cats in the high PL diet group that changed their diet after diagnosis (n=8) lived significantly longer (median survival of 290 days) than those in the high PL group that did not change their diet (n=6; median survival of 2 days, P = 0.014). Furthermore, cats eating high PL diets that changed their diet also had a significantly longer survival time compared to cats eating low PL diets (n=20; median survival of 10 days, P = 0.004). This improved survival in cats eating high PL diets who changed their diet was also supported by Cox proportional hazards analysis (P = 0.025).
Discussion
This study provides valuable insights into the current landscape of feline DCM. The survey results suggest that while taurine deficiency may still occur, it is not the primary finding in most cases seen by cardiologists today. The low incidence of measured taurine deficiencies and the lack of a significant association between taurine supplementation and survival in the retrospective study indicate that other factors may be at play in feline DCM.
The most compelling finding from the retrospective analysis is the significantly longer survival time observed in cats fed high PL diets that subsequently changed their diet. This observation strongly supports the hypothesis that a diet-associated DCM, potentially unrelated to taurine deficiency, may exist in cats. The results align with findings in dogs, where diet modification has been linked to improved cardiac outcomes. The improved survival in this subgroup, irrespective of initial diet type, suggests that diet change itself might be a critical intervention.
Despite these findings, the study acknowledges several limitations. The retrospective nature, small sample size, and potential for bias in case selection and diet reporting necessitate caution in drawing definitive conclusions. The lack of comprehensive follow-up echocardiographic data and consistent measurement of cardiac biomarkers like NT-proBNP limits the ability to fully assess the impact of interventions on cardiac function. Furthermore, the definition of DCM and diet classification could be refined in future research.
Conclusions
This study suggests that while taurine deficiency is less common in current feline DCM cases, diet may play a significant role. The improved survival rates in cats on high PL diets that changed their food point towards a potential diet-associated etiology for DCM in some felines. Further prospective research is crucial to elucidate the precise role of diet, identify specific causative factors, and establish optimal management strategies. In the interim, it is recommended that owners of cats diagnosed with DCM consider changing their cat’s diet to one free from peas and lentils, alongside standard veterinary care, until more definitive information becomes available.
Acknowledgements
The authors extend their gratitude to the Barkley Fund for their financial support. They also thank the participating cardiologists for their contributions to the survey and case submissions, as well as the veterinary technicians who assisted in gathering additional owner information.
Disclosures
Several authors have disclosed potential conflicts of interest, including receiving research funding, giving sponsored lectures, or providing professional services to various animal health companies such as Aratana Therapeutics, Elanco, Hill’s Pet Nutrition, Nestlé Purina PetCare, and Royal Canin.
Abbreviations
- 2D: Two-dimensional
- ACEI: Angiotensin-converting enzyme inhibitor
- CHF: Congestive heart failure
- DCM: Dilated cardiomyopathy
- FDA: United States Food and Drug Administration
- High PL diet: Diet with peas or lentils in the top 10 ingredients on the ingredient list
- LA:Ao: Ratio of the left atrial to aortic dimensions
- Low PL diet: Diet with no peas or lentils in the top 10 ingredients on the ingredient list
- NT-proBNP: N-terminal pro-B-type natriuretic peptide
