Cardiovascular Diseases in the Ageing Dog: Diagnostic and Therapeutic Problems

Abstract

Increased life expectancy is a common scenario for dogs living in the third millennium, since many advances in canine medicine and surgery, as well as in nutrition and preventive health care, have taken place over the last few decades. According to a study conducted on a population of 9248 subjects, cardiac diseases are the second most prevalent cause of death in the dog, accounting for a percentage of 16.3% (Eichelberg and Seine, 1996). A complete understanding of the pathophysiological mechanisms of cardiovascular diseases in the geriatric dog should include the complete knowledge of diseases primarily involving the cardiovascular system, as well as those affecting other systems with a known influence on cardiovascular function, in addition to a clear understanding of the modifications of the cardiovascular structure and function associated with advanced age. Age-related changes of canine cardiovascular function include decreased blood flow, blood velocity, and arterial compliance and distensibility (Miller et al., 1976; Haidet et al., 1996), as well as increased ventricular systolic and diastolic stiffness associated with prolonged duration of myocardial contractility (Templeton et al., 1976, 1979). A decline in cardiovascular responsiveness to beta-adrenergic stimulation has also been demonstrated in aged dogs (Yin et al., 1979; Haidet 1993). Progressive loss of organ reserve and adaptability, probably due to functional changes in the catecholaminergic system, was proposed as an inciting mechanism for cardiovascular diseases in older dogs by Strasser and colleagues (1997). However, unlike human beings, primary systemic hypertension (i.e. occurring in the absence of any underlying endocrine or renal disease) does not appear to be a common clinical problem in healthy geriatric dogs (Meurs et al., 2000). Furthermore, arteriosclerosis and related ischaemic heart disease are uncommon in the dog, but their real incidence may be underestimated (Falk and Jonsson, 2000). The precise relationship between the above-mentioned negative modifications of cardiovascular function and the development of specific cardiovascular diseases is difficult to ascertain. A recent study reported the overall prevalence of cardiac pathological alterations observed in beagle dogs employed as control subjects in four life-span studies at