Abstract
High salt dry expanded diets are commercially available for cats to increase water intake and urine volume, as part of the prevention or treatment of naturally occurring urinary stone formation (calcium oxalates and struvites). However, chronic high salt intake may have potential cardiovascular adverse effects in both humans, especially in aging individuals, and several animal models. The objective of this prospective, randomized, blinded, and controlled study was to assess the long-term cardiovascular effects of high salt intake in healthy aged cats. Twenty healthy neutered cats (10.1±2.4 years) were randomly allocated into 2 matched groups. One group was fed a high salt diet (3.1 g/Mcal sodium, 5.5 g/Mcal chloride) and the other group a control diet of same composition except for salt content (1.0 g/Mcal sodium, 2.2 g/Mcal chloride). Clinical examination, systolic and diastolic arterial blood pressure measurements, standard transthoracic echocardiography and conventional Doppler examinations were repeatedly performed on non-sedated cats by trained observers before and over 24 months after diet implementation. Radial and longitudinal velocities of the left ventricular free wall and the interventricular septum were also assessed in systole and diastole using 2-dimensional color tissue Doppler imaging. Statistics were performed using a general linear model. No significant effect of dietary salt intake was observed on systolic and diastolic arterial blood pressure values. Out of the 33 tested imaging variables, the only one affected by dietary salt intake was the radial early on late diastolic velocity ratio assessed in the endocardium of the left ventricular free wall, statistically lower in the high salt diet group at 12 months only (P = 0.044). In conclusion, in this study involving healthy aged cats, chronic high dietary salt intake was not associated with an increased risk of systemic arterial hypertension and myocardial dysfunction, as observed in some elderly people, salt-sensitive patients and animal models.
Highlights
On one hand, salt is a vital element for physiologic functions, including extra cellular fluid volume and blood pressure (BP) homeostasis, but on the other hand salt in excess may have potential deleterious cardiovascular effects [1]
In the present prospective study, BP, heart rate, cardiac morphology as well as myocardial function remained unaffected in healthy aged cats fed a HSD (1.3% sodium content and 2.27% chloride as fed) for 24 months, as compared with those fed a control diet (CD) similar in all respects except for the salt content (0.35% sodium, 0.70% chloride)
Cats in each diet group were deliberately matched with regard to both renal and cardiac function, as respectively assessed by glomerular filtration rate (GFR) and tissue Doppler imaging (TDI) examination
Summary
Salt is a vital element for physiologic functions, including extra cellular fluid volume and blood pressure (BP) homeostasis, but on the other hand salt in excess may have potential deleterious cardiovascular effects [1]. Several studies have already focused on the renal and cardiovascular safety of these high salt diets, and all reported the absence of significant adverse effect on systemic arterial BP, while significantly increasing water intake and decreasing urine specific gravity in comparison with cats fed a control diet [15,16,19,20]. None of the latter studies focused on the potential deleterious effects of high-salt diets on global and regional myocardial function using sensitive imaging techniques such as tissue Doppler imaging (TDI). Aged cats are known to be at risk for both systemic arterial hypertension [21,22] and chronic kidney diseases [23], two conditions that can be worsened by high-sodium diets in salt-sensitive humans and laboratory animals [24,25,26,27]
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