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Vitamin D levels in Dogs with Chronic Valvular Heart Disease | VETgirl Veterinary Continuing Education Podcasts

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In today’s VETgirl veterinary continuing education podcast, we review whether Vitamin D plays a role in heart disease in dogs. Vitamin D deficiency, as determined via serum 25-hydroxyvitamin D [25(OH)D] concentrations, is associated with worsened cardiac function, heart failure symptoms, and prognosis in human heart failure patients. Supplementation of vitamin D in such patients improves cardiac function and improves prognosis. A 2014 study in dogs demonstrated that serum 25-hydroxyvitamin D concentrations are lower in dogs with CHF secondary to either CVHD or DCM than in normal dogs. So, Osuga et al out of Japan wanted to evaluate if an association exists between vitamin D status and all stages of CVHD, as well as investigate if any association exists between vitamin D status and echocardiographic parameters of cardiac structure and function in these canine patients.

This was a cross-sectional study, and 43 dogs with CVHD were categorized according to the ACVIM Consensus Statement into specific stages (e.g., B1, B2, C, or D). The dogs in stage C and D were combined as one heart failure group. Stage B1 had 14 dogs, B2 had 17 dogs, and the heart failure C/D group had 12 dogs overall. Several of these dogs were on medications at the time of diagnosis. In the B1 group, 2 dogs were on ACEI; in the B2 group, 7 dogs were on ACEI, while 2 dogs were on spironolactone; and in the C/D group, a wide variety of CHF medications were used including ACEI, pimobendan, loop diuretics, spironolactone, digoxin, nitrates, and beta-blockers. All of these dogs had an echocardiogram performed and serum samples drawn on the same day. Serum BUN, creatinine, phosphorus, and total calcium were measured in addition to 25-hydroxyvitamin D concentrations. Exclusion criteria included any systemic disease that might impact vitamin D metabolism, or any other form of documented heart disease.

So, what’d they find in this study? First, the age differed significantly between different stages (specifically between the B1 and C/D group, but not the B2 and C/D group). As for clinicopathologic findings, the BUN was significantly higher in the B2 versus B1 group; no other group differences were observed among groups in creatinine, phosphorus or total calcium. Lastly, there was no correction of 25-hydroxyvitamin D and age, body weight, or body condition score. As for Vitamin D levels, the median serum 25-hydroxyvitamin D levels were significantly lower in the B2 and C/D group, as compared with the B1 stage. There was no statistically significant difference between levels in the B2 and C/D group, however. Specifically, 25-hydroxyvitamin D levels were 54.4 nmol/L in the B1 group, 35.8 nmol/L in the B2 group, and 13.1 nmol/L in the C/D stage group. This study did find significant negative correlations of 25-hydroxyvitamin D with BUN, left ventricular end-diastolic diameter normalized for body weight, left ventricular fractional shortening, left atrial-to-aortic root ratio, among other echocardiographic parameters.

Overall, this study suggested that vitamin D status may correlate directly with the stage of chronic valvular heart disease and structural cardiac changes as detected by echocardiography, both of which are markers for disease severity. Vitamin D is believed to be involved in the regulation of cardiac remodeling by reducing hypertrophy, fibrosis, renin-angiotensin-aldosterone-system activity, and proinflammatory cytokines. Parathyroid hormone is known to be involved in myocardial remodeling, thus vitamin D suppression of PTH may additionally blunt these effects. Vitamin D may also promote cardiac relaxation via effects on calcium handling with myocytes.

So, VETgirl’s take on this study? This study and the prior study (Kraus) are likely just scratching the surface of the interactions of vitamin D, calcium and myocardial function but it is a very interesting and potentially exciting new avenue of investigation in veterinary cardiology. Although a statistically significant difference was not detected between groups B2 and C/D, gross evaluation of the data shows that a difference does appear to exist, thus one has to wonder if this lack of statistical significance was merely a matter of insufficient power of the study (e.g., small numbers in groups). The complex interactions of various body systems never cease to amaze!

The bottom line? Serum vitamin D concentrations appear to negatively correlate with advancing chronic valvular heart disease in dogs as assessed by disease staging and echocardiographic assessment of cardiac structure and function. This correlation included dogs that had not yet progressed to congestive heart failure, but stay tuned for future studies.

Abbreviations:
[25(OH)D] – 25-hydroxyvitamin D
CVHD – Chronic valvular heart disease
DCM – Dilated cardiomyopathy
BUN – blood urea nitrogen
ACVIM – American College of Veterinary Internal Medicine
B1 CVHD: Chronic valvular heart disease w/ no heart enlargement
B2 CVHD: Chronic valvular heart disease w/heart enlargement but no heart failure
C CVHD: Chronic valvular heart disease w/congestive heart failure
D CHVD: Chrnonic valvular heart disease with refractory CHF (exceeding thresholds for what is considered high-dose diuretic therapy)
ACEI: angiotensin converting enzyme inhibitors
Nmol/L: nanomol per liter
BCS: Body condition score
LVEDDN: Left ventricular end-diastolic diameter normalized for body weight
LF-FS: left ventricular fractional shortening
LA/Ao: Left atrial-to-aortic root ratio
RAAS – Renin-angiotensin-aldosterone-system
PTH – Parathyroid hormone

References:
1. Osuga T, Nakamura K, Morita T, et al. Vitamin D Status in Different Stages of Disease Severity in Dogs with Chronic Valvular Heart Disease. J Vet Intern Med 2015;29:1518-1523.

2. Kraus MS, Rassnick KM, Wakshlag JJ, et al. Relation of vitamin D status to congestive heart failure and cardiovascular events in dogs. J Vet Intern Med 2014;28(1):109-15.

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