Cardiac pathology associated with hypertension and chronic kidney disease in aged cats

Hypertension is a common condition in older cats, often secondary to chronic kidney disease (CKD). Although the heart is one of the organs damaged by hypertension, the pathology of the feline hypertensive (HT) heart has been poorly studied. The aim of this retrospective study was to describe the gross and microscopic pathology of hearts obtained from cats at post-mortem examination and to compare cats diagnosed with hypertension with cats of similar age and kidney function for which antihypertensive treatment was not deemed clinically necessary. Hearts from 32 cats were examined‒18 from HT and 14 from normotensive (NT) cats. The prevalence of CKD was 72.2% vs. 78.6% in the HT and NT groups, respectively. The time-averaged blood pressure over the longitudinal follow-up from diagnosis was significantly higher in the HT group compared with the NT group (153.4 ± 20.8 vs. 133.9 ± 19.3 mmHg; P = 0.0106), respectively. HT cats, when compared with NT cats, had a thicker left ventricular free wall (7.67 [5.45-9.29] vs. 5.07 [4.72-7.16] mm; P = 0.001) and interventricular septum (6.92 [6.26-7.56] vs. 4.96 [4.15-6.46] mm; P = 0.008) and higher ventricular weight as a percentage of body weight (0.34 [0.29-0.36] vs. 0.28 [0.21-0.31]%; P = 0.02), respectively. Myocardial fibrosis was present in 72% of cases with no significant difference in the prevalence (P = 0.45) or score (P = 0.81) between the HT (1 [0.75-2]; 77.8% scoring one or above) and NT cats (1 [0-2]; 64.3% scoring one or above). Similarly, the population prevalence of myocyte hypertrophy, myofibre disarray and microvascular change was 71.9%, 50% and 43.7%, respectively, and did not differ significantly between groups. These results suggest that age-related cardiac pathology, exacerbated by azotaemic CKD, in cats is very common. The role that hypertension plays in mediating these pathological changes is uncertain.