Expansion
Arteries stiffen, diastolic function declines, and maximum heart rate falls
Expansion
Vessels
- Elastin is replaced by collagen, so arteries stiffen
- Systolic pressure rises and diastolic falls, giving isolated systolic hypertension and a wide pulse pressure
- Endothelial nitric oxide production declines
Heart
- Diastolic dysfunction: the ventricle stiffens, early filling falls, and the atrial kick becomes more important
- Modest concentric hypertrophy
- Reduced beta-adrenergic responsiveness, so less increase in rate and contractility for a given catecholamine level
- Maximum heart rate falls, approximately 220 minus age
- Loss of sinoatrial pacemaker cells, predisposing to sick sinus syndrome and atrial fibrillation
Reflexes
- Blunted baroreflex, so more orthostatic hypotension
The practical consequences are that older patients tolerate tachycardia, hypovolaemia and loss of sinus rhythm poorly, because each of these attacks the filling that their stiff ventricles already struggle to achieve.