Clopidogrel is converted to its active metabolite by cytochrome P450 isoenzymes and irreversibly inhibits platelet activation by antagonizing the adenosine-diphosphate (ADP) receptor. It is frequently used in cats with hypertrophic cardiomyopathy (HCM) to prevent thromboembolic complications. However, significant interpatient variability of the response to clopidogrel therapy has been suspected. In this study, we assessed the impact of single nucleotide polymorphisms (SNPs) within ADP receptor (P2RY1, P2RY12) and cytochrome P450 isoenzyme (CYP2C41) genes on platelet inhibition by clopidogrel administration in cats with HCM. Forty-nine cats completed the study, and blood samples were obtained before and after clopidogrel therapy to assess the degree of platelet inhibition based on flow cytometry and whole blood platelet aggregometry. Plasma concentrations of clopidogrel metabolites were measured after the last dose of clopidogrel. Whole blood platelet aggregometry revealed a significant reduction of platelet inhibition by clopidogrel in cats with the P2RY1:A236G and the P2RY12:V34I variants. The association with the P2RY1:A236G variant and clopidogrel resistance remained significant after adjustment for multiple comparisons. This study demonstrated that a genetic polymorphism in the P2RY1 gene altered response to clopidogrel therapy and suggests that clinicians may consider alternative or additional thromboprophylactic therapy in cats with the P2RY1:A236G variant.

Small molecule inhibitors are an emerging class of novel therapeutic agents that inhibit the function of specific proteins with the potential for neutralizing deleterious downstream effects (Bond et al., 2013). One class of these compounds include cardiac myosin inhibitors, which are being investigated for their potential therapeutic uses in a vast array of disease processes including hypertrophic cardiomyopathy (HCM) (Alsulami & Marston, 2020;Argirò et al., 2021).

Hypertrophic cardiomyopathy (HCM) is the most prevalent inherited cardiac disease in humans and cats and lacks efficacious pharmacologic interventions in the preclinical phase of disease. LV outflow tract obstruction (LVOTO) is commonly observed in HCM-affected patients and is a primary driver of heart failure symptoms and reduced quality of life. Novel small-molecule cardiac myosin inhibitors target actin-myosin interactions to alleviate overactive protein interactions. A prospective, randomized, controlled cross-over study was performed to evaluate pharmacodynamic effects of two doses (0.3 and 1 mg/kg) of a next-in-class cardiac myosin inhibitor, aficamten (CK-3773274, CK-274), on cardiac function in cats with the A31P MYBPC3 mutation and oHCM. Dose-dependent reductions in LV systolic function, LVOT pressure gradient, and isovolumetric relaxation times compared to baseline were observed. Promising beneficial effects of reduced systolic function warrant further studies of this next-in-class therapeutic to evaluate the benefit of long-term administration in this patient population.

In a colony of rhesus macaques at California National Primate Research Center (CNPRC), naturally occurring hypertrophic cardiomyopathy (HCM) classified by left ventricular hypertrophy without obvious underlying diseases has been identified during necropsy over the last two decades. A preliminary pedigree analysis suggested a strong genetic predisposition of this disease with a founder effect. However, the mode of inheritance was undetermined due to insufficient pedigree data. Since 2015, antemortem examination using echocardiographic examination as well as other cardiovascular analyses have been performed on large numbers of rhesus macaques at the colony. Based on antemortem examination, HCM was diagnosed in additional 65 rhesus macaques. Using HCM cases diagnosed based on antemortem and postmortem examinations, the heritability (h2) was estimated to determine the degree of genetic and environmental contributions to the development of HCM in rhesus macaques at the CNPRC. The calculated mean and median heritability (h2) of HCM in this colony of rhesus macaques were 0.5 and 0.51 (95% confidence interval; 0.14–0.82), respectively. This suggests genetics influence development of HCM in the colony of rhesus macaques. However, post-translational modifications and environmental factors are also likely to contribute the variability of phenotypic expression. Based on the pedigree analysis, an autosomal recessive trait was suspected, but an autosomal dominant mode of inheritance with incomplete penetrance was also possible. Further investigation with more data from siblings, offspring, and parents of HCM-affected rhesus macaques are warranted. Importantly, the findings of the present study support conducting genetic investigations such as whole genome sequencing to identify the causative variants of inherited HCM in rhesus macaques.

Cardiac malformations are sporadically diagnosed in domestic species; however, little literature is available for this group of developmental anomalies in goats. We performed a retrospective study to catalog congenital cardiac conditions in goats submitted to the University of California–Davis, Veterinary Medical Teaching Hospital, Anatomic Pathology Autopsy Service. From 2000 to 2021, of 1,886 goat autopsies, 29 cases of cardiac malformations were identified (1.5%). Thirteen were ≤ 2-wk-old, 8 were 1–6-mo-old, and 8 were adults 2–9-y-old. The most common malformations were ventricular septal defect (VSD; 21 of 29), atrial septal defect or persistent foramen ovale (10 of 29), and double-outlet right ventricle (3 of 29). Nine cases had > 1 malformation, typically including a VSD. Conditions that had not been reported in the goat included double-outlet right ventricle (3), tetralogy of Fallot (1), cor triatriatum sinister (1), and mitral valve dysplasia (1). Two adult cases were incidental and not suspected clinically. Cardiac malformations occur not uncommonly in goats and should be considered in a wide age range.