The cardiovascular changes with age can separated into those seen while at rest and those seen during exercise (Table 3.20), (Table 3.21).
At rest, systole and isovolumic diastole become prolonged, i.e. the heart contracts and relaxes more slowly . The slower contraction process results in an increased pre-ejection period (PEP/LVET). Left ventricle ejection time is also increased. The P-R, QRS, and Q-T intervals are lengthened, due to slower conduction. The amplitude of the QRS com plex, actually the R wave, is decreased.
There is a decrease in cardiac output from the 3rd to the 9th decade, approximately 1% per year. This is due a decrease in stroke volume. This is coupled with an increase in A-V O2 difference, as tissue must extract more of the oxygen from the blood that reaches it.
A Gradual cardiac hypertrophy of 50 g in 30 years, is the usual finding. This is related to the increased workload placed on the left ventricle due to increased systemic arterial stiffness (decreased compliance) and hypertension (Table 3.22), and also to decreased ventricular and possibly pericardial compliance.
Ventricular filling is slower due to increased stiffness and end-diastolic pressure is usually higher. Valves, particularly the mitral valve begin to regurgitate, increasing left ventricle work and dilating and hypertrophying the left atrium.
Plasma catecholamines rise, while myocardial catecholamine levels fall and the sensitivity of the heart to the actions of catecholamines decreases.
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