Cardiovascular

Cardiovascular

1. Arteries stiffen with age, leading to faster propagation and reflection of the pulse pressure waveform. The reflected waveform augments the pressure at the aortic root. With increasing age, the reflected energy arrives progressively earlier in the cardiac cycle, shifting from early diastole to late systole. Thus, aging causes decreased diastolic and increased systolic pressure (and pulse pressure) and leads to ventricular thickening and prolonged ejection.
2. Slower myocardial relaxation and ventricular hypertrophy lead to late diastolic filling and diastolic dysfunction. Atrial contraction is important to maintain late filling.
3. Reduced venous capacitance decreases the “vascular reserve volume” available to buffer hemorrhage.
4. Reduced baroreceptor reflexes result from increased sympathetic tone, decreased parasympathetic tone, decreased baroreceptor sensitivity, and decreased responsiveness to β-adrenergic stimulation. Thus, hypotension occurs frequently with changes in volume, position, anesthetic depth, and regional anesthetic–induced sympathetic blockade.
5. Maximal heart rate decreases with age while stroke volume remains constant, but end-diastolic volume increases and ejection fraction decreases.
6. Maximal oxygen consumption decreases because of reductions in arteriovenous oxygen tension difference and cardiac output.