Echocardiographic and electrocardiographic findings in Irish Wolfhounds eating high‐pulse or low‐pulse diets

Abstract

Background

Apparently healthy dogs of various breeds eating nontraditional, high‐pulse diets can have larger left ventricular diameter, lower systolic function, and more ventricular premature complexes (VPCs) compared with dogs eating traditional, low‐pulse diets. It is unknown whether Irish Wolfhounds eating high‐pulse diets have similar cardiac abnormalities.

Hypothesis/Objectives

To compare electrocardiographic and echocardiographic findings between Irish Wolfhounds eating high‐ or low‐pulse diets.

Animals

Ninety‐seven Irish Wolfhounds.

Methods

Retrospective study of Irish Wolfhounds that had echocardiography performed at dog shows between October 2018 and May 2021. Demographic information, echocardiographic measurements, cardiac rhythm (1‐minute lead II rhythm strip), and main diet were recorded retrospectively. Diets were classified as high‐pulse or low‐pulse based on the presence and location of pulses (peas, lentils, chickpeas, or dry beans) on the ingredient list.

Results

Thirty‐five of 97 Irish Wolfhounds (36%) were eating high‐pulse diets and 62 of 97 (64%) were eating low‐pulse diets. There were no significant differences between diet groups in echocardiographic measurements. A significantly higher percentage of dogs in the high‐pulse diet group (6/35 [17%]) had VPCs compared with those in the low‐pulse diet group (1/62 [2%]; effect size = 0.15 [95% confidence interval: 0.004‐0.31]; P = .005).

Conclusions and Clinical Importance

In this retrospective study of apparently healthy Irish Wolfhounds, high‐pulse diets were associated with a higher prevalence of VPCs which could represent early cardiac abnormalities.

Abbreviations

BCS

body condition score

DCM

dilated cardiomyopathy

IWCM

Irish Wolfhound cardiomyopathy

VPC

ventricular premature complex

1. INTRODUCTION

Some dog breeds, such as Doberman Pinschers and Great Danes, are predisposed to primary dilated cardiomyopathy (DCM). However, secondary forms of DCM that have drug, nutritional, toxin, or infectious causes also can affect dogs. ¹ There is an ongoing investigation of a recently identified secondary form of DCM associated with diet. ² The specific cause of this diet‐associated DCM is not yet known but appears to be linked to intake of diets high in pulses (ie, peas, lentils, chickpeas, and dry beans) and, possibly, potatoes and sweet potatoes. ³ , ⁴ Apparently healthy dogs eating these diets, often referred to as “nontraditional diets,” have a larger left ventricular diameter, lower systolic function, higher cardiac troponin I, and more ventricular premature complexes (VPCs) compared with dogs eating low‐pulse diets; these changes can improve after diet change. ⁵ , ⁶ , ⁷ , ⁸

Irish Wolfhounds are predisposed to a specific form of primary DCM known as Irish Wolfhound Cardiomyopathy (IWCM), which appears to have a genetic link. ⁹ , ¹⁰ , ¹¹ , ¹² , ¹³ In IWCM, key findings include atrial fibrillation, progressive left atrial dilation disproportionate to the degree of left ventricular dilation, and, often, minimal change in estimated myocardial function. ¹⁴ Effect of diet on cardiac function in IWCM is largely unknown. In addition to IWCM, a small number of Irish Wolfhounds with more typical echocardiographic findings of DCM like that seen in Doberman pinschers have been included in some studies of diet‐associated DCM. In a retrospective study, 1/56 dogs with DCM eating nontraditional diets was an Irish Wolfhound. ¹⁵ In a prospective study, 1/51 dogs with DCM eating nontraditional diets and 3/16 dogs with subclinical cardiac abnormalities eating nontraditional diets were Irish Wolfhounds. ¹⁶ Echocardiographic and electrocardiographic evaluations of large numbers of Irish Wolfhounds describe reference ranges and prevalence of cardiac abnormalities. ¹⁴ , ¹⁷ However, it is unknown whether apparently healthy Irish Wolfhounds eating high‐pulse diets have electrocardiographic or echocardiographic differences compared with those eating low‐pulse diets.

Therefore, the objective of this study was to compare electrocardiographic and echocardiographic findings between Irish Wolfhounds eating high‐ or low‐pulse diets. We hypothesized that Irish Wolfhounds eating high‐pulse diets would have significantly larger left ventricular diameter, lower systolic function, and more VPCs compared with Irish Wolfhounds eating low‐pulse diets.

2. MATERIALS AND METHODS

Data were collected for this study from cardiology screening clinics performed at national and regional Irish Wolfhound specialty shows. The Irish Wolfhound Foundation advertised the screening clinics and assisted in the recruitment of both breeding‐age hounds as well as retired, veteran Irish Wolfhounds. The Irish Wolfhound Club of America encourages annual screening examinations via electrocardiography for all Irish Wolfhounds. The Irish Wolfhound Foundation provided incentives by subsidizing the costs of examinations. Examinations included an echocardiogram performed by 1 of 2 authors who are board‐certified veterinary cardiologists (WDT or SLR). Echocardiography was performed using standard techniques ¹⁸ with the dogs standing, and measurements were made on 3 consecutive cardiac cycles on 2‐dimensional and M‐mode echocardiograms. Irish Wolfhound Cardiomyopathy was defined by the findings of both left ventricular chamber dilation and left ventricular systolic myocardial dysfunction together with left atrial enlargement. ¹⁴ As part of the examination, dogs had a standing, 1‐minute lead II rhythm strip performed. The ECGs were reviewed by 1 of the same 2 board‐certified veterinary cardiologists.

To be eligible for this retrospective cohort study, dogs had to have an echocardiogram performed at 1 of the shows between October 2018 and May 2021, be at least 1 year of age, be primarily eating a dry (kibble) diet (since the current episode of diet‐associated DCM appears to be primarily associated with dry diets), ² , ³ and have sufficient diet information to be able to categorize their diet as high‐ or low‐pulse. Each dog's main diet (ie, the diet providing the majority of the dog's calories) at the time of the echocardiogram was determined either at the time of the show or by contacting the owner or breeder afterward. For the purposes of the study, dogs were categorized as eating a high‐pulse diet if the main diet included pulses in the top 10 ingredients on the ingredient list and as low‐pulse diets if there were no pulses in the top 10 ingredients. If the food label was not collected for an individual dog within 6 months of the time of the echocardiogram, an internet archive website (Wayback Machine, https://archive.org/web/) was used to identify the ingredient list from the diet on the date as close as possible to the date of the echocardiogram. For dogs in which the exact flavor of the product could not be determined, the ingredient lists for all possible products containing the known dietary information (eg, Brand X grain‐free chicken diet) were reviewed. If insufficient information was available to make diet categorization possible (eg, if the exact flavor could not be determined, and 1 possible flavor of a product included peas and another flavor did not include peas), the dog was excluded from the study. Diet pulse and pulse/potato scores for each dog were calculated as previously described. ¹⁶ Dogs that were eating a homemade or raw diet were excluded from the analysis. Dogs that were known to have cardiac disease from previous echocardiograms also were excluded. For dogs that had multiple echocardiograms at shows, data from the first echocardiogram was used for analysis. Dogs' body weights were reported by the owners, and body condition score (BCS) was assessed by investigators using a 9‐point scoring system. ¹⁹

2.1. Statistical analysis

Data distributions were tested with visual inspection and Shapiro‐Wilk tests. Since many were not normally distributed, data are reported as median (range) or frequency (percentage). The 2 diet groups were compared using Mann‐Whitney U tests for continuous variables and chi‐square tests for categorical variables. These analyses were performed with commercially available software (SPSS 25.0, IBM Corp). Effect sizes and 95% confidence intervals for the difference in proportions and difference in medians ²⁰ were calculated with statistical software (Rstudio 2022, R Foundation for Statistical Computing, https://www.r-project.org) using the low‐pulse diet group as the reference group. P‐values < .05 were considered significant.

3. RESULTS

Between October 2018 and May 2021, 148 Irish Wolfhounds had first‐time echocardiograms. Dogs were excluded from analysis for the following reasons: Eating a raw or homemade diet as the main diet (n = 31), dogs with previously‐known heart disease (n = 10), and dogs for whom the main diet could not be determined in sufficient detail to allow for categorization (n = 10). Ninety‐seven dogs were eligible for the study and were included in the final analysis. Of these dogs 35 (36%) were eating high‐pulse diets and 62 (64%) were eating low‐pulse diets. There were no significant differences between diet groups in age (P = .20), sex (P = .87), body weight (P = .60), BCS (P = .31), prevalence of atrial fibrillation (P = .79), or echocardiographic measurements (all P > .05; Table 1). However, a significantly higher percentage of dogs in the high‐pulse diet group (6/35 [17%]) had VPCs compared with those in the low‐pulse diet group (1/62 [2%], P = .005; Table 1). For dogs in which the exact number of VPCs during the 1‐minute ECG were recorded (4 of 7 dogs), VPC number ranged from 1 to 7. The other 3 dogs were all noted to have single VPCs. Two dogs with VPCs had the same owner and were eating the same diet, although none of the dogs were closely related.

TABLE 1.

Clinical, echocardiographic, and electrocardiographic findings in 97 Irish Wolfhounds.

Variable	High‐pulse diet	Low‐pulse diet	P‐value	Effect size (95% CI)
n	35	62
Age (years)	4.6 (1.6‐8.8)	3.6 (1.8‐8.9)	.20	0.5 (−0.3, 1.3)
Sex
Female	22 (63%)	40 (64%)	.87	−.01 (−.22, .18)
Male	13 (37%)	22 (36%)
Body weight (kg)	65 (45‐85)	63 (44‐81)	.60	1 (−2, 6)
Body condition score (1‐9)	5 (4‐7)	6 (4‐8)	.31	0 (0, 0)
Pulse score 16	42 (16‐104)	0 (0‐11)	<.001	37 (23, 46)
Pulse/potato score 16	68 (16‐121)	0 (0‐43)	<.001	68 (39, 79)
Electrocardiography
Atrial premature complexes	1 (3%)	6 (10%)	.21	−.07 (−.18, 0.05)
Atrial fibrillation	4 (11%)	6 (10%)	.79	.01 (−.13, .16)
Ventricular premature complexes	6 (17%)	1 (2%)	.005	.15 (.004, .31)
Echocardiography
IVSd (cm)	0.98 (.63‐1.41)	1.00 (.60‐1.44)	.62	−.02 (−.10, .07)
LVIDd (cm)	5.19 (4.42‐6.59)	5.15 (4.35‐6.41)	.70	.04 (−.16, .24)
LVWd (cm)	1.05 (.81‐1.31)	1.10 (.78‐1.54)	.13	−.05 (−.11, .02)
LVIDs (cm)	3.26 (2.46‐4.76)	3.35 (2.59‐4.59)	.86	−.01 (−.17, .15)
LA:Ao	1.18 (.93‐1.55)	1.22 (.97‐2.18)	.90	−.01 (−.06, .06)
Fractional shortening (%)	34.75 (26.83‐44.80)	35.19 (26.80‐49.66)	.67	.46 (−1.55, 2.51)
IWCM	2 (6%)	3 (5%)	.85	.01 (−.09, .11)

Note: Each dog's main diet was categorized as high‐pulse if the main diet included pulses in the top 10 ingredients on the ingredient and as low‐pulse if there were no pulses in the top 10 ingredients. Results are presented as frequency (percentage) or median (range). The low‐pulse diet group was used as the reference to compute effect size and 95% CI.

Abbreviations: 95% CI, 95% confidence interval; IVSd, interventricular septum in diastole; IWCM, Irish Wolfhound Cardiomyopathy ¹⁴ ; LA:Ao, ratio of the left atrial to aortic diameters; LVIDd/s, left ventricular internal diameter at end‐diastole/systole; LVWd, left ventricular posterior wall in diastole.

4. DISCUSSION

In this study, VPCs were significantly more common in apparently healthy Irish Wolfhounds eating high‐pulse diets compared with those eating low‐pulse diets. This result is consistent with findings from a study of 188 dogs of 4 different breeds (Doberman Pinschers, Golden Retrievers, Miniature Schnauzers, and Whippets) eating diets with peas, lentils, or potatoes in the top 10 ingredients compared with those eating diets without those ingredients in the top 10 ingredients. ⁶ In that study, significantly more dogs eating diets high in pulses or potatoes (4/39 [10%]) had VPCs compared with dogs without those ingredients in the top 10 (3/149 [2%]). ⁶ Other cross‐sectional studies and prospective studies of apparently healthy dogs eating nontraditional diets do not report data on VPCs. ⁵ , ⁸ , ²¹ , ²² , ²³ , ²⁴ , ²⁵ While the prevalence rates of VPCs for the 2021 Adin et al. study (10%) ⁶ and the current study (17%) are relatively low, they are consistent with the findings from a prospective study of dogs eating nontraditional diets with subclinical cardiac abnormalities in which 2/16 dogs (13%) had VPCs at the time of diagnosis, with 1 of these dogs experiencing sudden death during the 9‐month study period. ¹⁶

We also hypothesized that dogs eating high‐pulse diets would have larger left atrial and left ventricular measurements and lower fractional shortening, but echocardiographic measurements were not significantly different between the 2 diet groups. This is in contrast to some cross‐sectional ⁵ , ⁸ and most prospective studies ²¹ , ²³ in apparently healthy dogs eating nontraditional diets in which there were no significant differences or changes in left ventricular diameter and measures of systolic function. However, 2 studies in laboratory dogs fed high‐pulse diets for 1 month do not report echocardiographic differences. ²⁴ , ²⁵ Differences in findings could be due to breed or study design. In 1 cross‐sectional study of pet dogs, no echocardiographic differences were identified between diet groups, but dogs eating high pulse/potato diets had significantly higher high‐sensitivity cardiac troponin I concentrations in addition to the previously‐mentioned differences in VPCs. ⁶ It would have been valuable to measure cardiac troponin I in the current study but this is not a standard part of the ongoing Irish Wolfhound screenings.

This study has a number of important limitations. A major limitation of the study is that arrhythmias were determined from a rhythm strip and not from a 24‐hour Holter recording. Therefore, the true prevalence of VPCs and other arrhythmias is unknown. However, Holters are now being performed in Irish Wolfhounds in which VPCs are identified on screening electrocardiograms, so this will provide additional information in the future. The sample size is another limitation since the prevalence of VPCs was relatively low (especially in the low‐pulse diet group), so larger studies are needed and would help to reduce the risk of a type I error. Another important information is that, while dogs had a physical examination and medical history was provided by owners, concomitant systemic diseases as a cause of VPCs were not ruled out. Additionally, body weight was not measured and was owner‐reported so might not be accurate. Body condition score was assessed by different people so there could be some variability in the assessment of this measurement.

Additional limitations include factors related to diet. The ideal classification of diets for research on diet‐associated DCM still is unknown, but it has been refined over time as additional information has been learned about this disease. In the current study, we focused on pulses as ingredients, rather than other less objective characteristics about the diets, based on recent research supporting the role of pulses in this current episode of diet‐associated DCM. ³ , ⁴ Data on diet were initially collected retrospectively and adequate information to be able to categorize diets was not always available. Therefore, it was necessary to contact some owners or breeders to collect this information later (diet history information is now included as a standard part of the examinations performed at dog shows). The duration dogs had been eating the diets at the time of the echocardiogram was not determined so some dogs' diets could have been misclassified based on an unreported recent diet change. Similarly, while we used the ingredient list from a label close to the time of the echocardiogram, some product formulations have changed over time, which could result in higher or lower levels of pulses, and this was not accounted for.

Despite these limitations, this is the second study suggesting an association between high‐pulse diets and VPCs in apparently healthy dogs. Given these results, further investigation into this possible association is warranted.

CONFLICT OF INTEREST DECLARATION

These author declarations are for the last 3 years. Dr. Freeman has received research or residency funding from, given sponsored lectures for, or provided professional services for Aratana Therapeutics, Elanco, Guiding Stars Licensing Co, LLC, Morris Animal Foundation, Nestlé Purina PetCare, and P&G Petcare (now Mars). Dr. Rush has received research funding or travel support from, given sponsored lectures for, or provided professional services for Aratana Therapeutics, Boehringer Ingelheim, Elanco, IDEXX, Increvet, Morris Animal Foundation, and Nestlé Purina PetCare. Dr. Rosenthal has provided professional services for Zoetis and Ceva Animal Health, given a sponsored lecture for Hill's Pet Nutrition, received research support from Nestle Purina PetCare, and received travel support and honoraria from Boehringer Ingelheim. Dr. Tyrrell has provided professional services for Zoetis and Ceva Animal Health and received travel support from Boehringer Ingelheim.

OFF‐LABEL ANTIMICROBIAL DECLARATION

Authors declare no off‐label use of antimicrobials.

INSTITUTIONAL ANIMAL CARE AND USE COMMITTEE (IACUC) OR OTHER APPROVAL DECLARATION

Authors declare no IACUC or other approval was needed.

HUMAN ETHICS APPROVAL DECLARATION

Authors declare human ethics approval was not needed for this study.

Coppinger LM, Freeman LM, Tyrrell WD Jr, et al. Echocardiographic and electrocardiographic findings in Irish Wolfhounds eating high‐pulse or low‐pulse diets. J Vet Intern Med. 2024;38(3):1300‐1304. doi: 10.1111/jvim.17075