302 Ageing cardiovascular system Flashcards
What ae some examples of how the heart ages?
-Reduced cardiomyocytes
-Relative increase in fibroblasts
-Calcification of heart and vascular structures
Eg. Accumulation of by products of ageing – amyloid, lipofuscin
Combination of above leads to:
Reduced elastic recoil
Myocardial stiffness
Decreased ventricular compliance
Impaired passive filling of the LV
Ultimately lead to problems on systolic and especially diastolic function
How many cardiomyocytes are lost with age regardless of disease?
One third lost between ages of 17 and 90
How does increase in fibroblasts affect the heart?
Collagen production increases => increased cross-linking of fibres => fibrosis in atria and ventricles
Accompanied by detrimental changes elastin => less elasticity within cardiac tissue
What are some effects of ageing on the heart at rest?
No change in resting heart rate
-LV systolic function preserved
Stroke volume and ejection fraction is unchanged
-Diastolic function reduced:
Rate of LV filling in early diastole reduces by 50% between 20 and 80 years
-Passive filling reduced due to:
reduced compliance in stiff ventricle
delay in cardiomyocyte relaxation related to calcium metabolism
-Preserved systolic function (ejection fraction) at expense of diastolic function
Atrial contraction to maintain end-diastolic volumes and pressures
Prolonged contraction to eject blood (with consequent delay in relaxation)
Consequence in some = Heat failure with preserved EF (problem with relaxation)
What are some ageing heart changes to do with excersise?
-Age-related decline in aerobic capacity in absence of CVD
-The max heart rate decreases
-Decreased sensitivity to sympathetic stimulation
Why is exercise good the the ageing heart?
-Blunts decline in VO2 max
-Can reduce decline in cardiac output (max HR still declines)
-Attenuates arterial stiffness
-Protects from increase in fibrosis and apoptosis
-Reduces risk of cardiovascular diseases
What are the changes to the atria with ageing?
-Atrial fibrosis as for ventricles
-Age-dependent increase in size -Atria dilate, atrial volume increases
Early passive ventricular filling impaired (stiff ventricle, poor relaxation)
Increased diastolic filling pressure => atrial dilatation and hypertrophy
Forceful atrial contraction promotes late diastolic filling as compensation
What are the conduction changes in an ageing heart?
Sinoatrial node:
-By age 50 – up to 75% of pacemaker cells lost
-Reduced atrial sympathetic innervation
Atrioventricular node:
-Number of cells unchanged
Pathophysiology:
Fibrosis at SA node, AV node, Bundle of His, Left bundle
ECG:
Prolongation - PR interval, QRS duration, and QT interval
Consequences - Arrhythmia
-AF
-Sinus node disease
-Sinus bradycardia, sinus arrest, AV block, Tachy-brady syndrome
Calcification around the aortic valve can affect AVN and His Bundle promoting syncope in aortic stenosis
What happens to the heart valves in an ageing heart?
-Fibrosis
-Calcification
-Degeneration secondary to ‘wear and tear’
-Superadded effects of atherosclerosis
Consequence:
-Non-significant valvular defects causing murmurs – aortic sclerosis
-Valvular heart disease with haemodynamic compromise or heart failure
What are the 3 layers of arteries?
Tunica intima: connective tissue layer, endothelial layer
Tunica media: connective tissue, smooth muscle, elastic tissue
Tunica adventitia: collagen fibres, elastic tissue
What happens to central elastic arteries like aorta, carotids, and pulmonary with age
-They dilate => increase lumen size
-Intima thickens (↓elastin, ↑ collagen, infiltration smooth muscle) => stiff arteries
-Media – smooth muscle cells ↓, hypertrophy of remaining cells (unclear if effects function)
-Calcification
What happens to the endothelium of blood vessels with age?
-Endothelial dysfunction
-Decreased nitric oxide production
-Free radicals, ↓ endothelial NO synthase
-Decreased vascular smooth muscle relaxation
-Adding to arterial stiffness
-↑ risk of CVD
What causes arteries to become stiff?
Increased collagen and decreased elastin so there is reduced elastic recoil
What is isolated systolic hypertension?
Definition: systolic blood pressure >160 mmHg, with diastolic blood pressure <90 mmHg
Accounts for 60-80% of hypertension in older adults
There’s increased systolic blood pressure, increases afterload => LV hypertrophy and Increased myocardial oxygen demand
Decreased diastolic blood pressure
Perfusion-metabolism mismatch, myocardial ischaemia
This causes a widened pulse pressure
How do diuretics cause postural hypotension?
Volume depletion
