Transcript Aging of Skeletal Muscle

Aging of Cardiac Muscle
and
Cardiac Failure
Dr. Franco Navazio
Aging Heart in the Elderly
In absence of specific disease the heart adjusts
very well to advancing age.
Myocardium: Cardiac muscle
syncytium (multi-nucleated)
Endocardium: Internal layer of
heart
Pericardium: External
connective tissue layer of
heart
Valves: openings between
cardiac chambers (atrial
ventricular) or between heart
the arteries (aorta and
pulmonary)
Conduction system: sinoatrial
node (SA) is the pacemaker;
also atrial ventricular node
(AV), Bundle of His, Purkinje
system
Aging Heart: Physiology
Decline in the VO2 Max with advancing age
Minor decline in the cardiac output
Important Variables:
– physical conditions
– dietary habits
Conclusions: Physically fit elderly people
have a cardiac physiology similar to
younger individuals
Physiological Changes with Age
Parameter
VO2 Max (mL x kg x min)
Maximum Heart Rate
20 years
39
194
60 years
29
162
Resting Heart Rate
Max. Cardiac Output (L x min)
EJECTION FRACTION
63
22
70-80%
62
16
50-55%
Resting BP
Total Lung Capacity (L)
120/80
6.7
130/80
6.5
Vital Capacity (L)
5.1
4.4
Residual Lung Volume (L)
1.5
2.0
Body Fat %
20.1
22.3
Cardiovascular Changes with Age
Hypertension: most common treatable cardiovascular change in the elderly
Definition: values above 140/190
In young, if standing BP
but in elderly it may to 20 mmHg
Systolic mumur: 50% of elderly but of very short duration
EXG (or ECG): only nonspecific changes due to aging in voltage
and nonspecific RBBB
Hypotension: diminished baro-reflex response in the elderly. With
age, cerebral blood flow
but autoregulation acts in a
compensatory fashion; some patients maybe affected by
symptomatic orthostatic hypotension
Orthostatic hypotension: drop of 20 mmHg in the systolic and 10 or
more in the diastolic BP on standing upright
*MEMO as well as the post-prandial hypotension
Pathology of the Aging Heart
Changes due to:
• Normal Aging Processes
• Superimposed Processes
(i.e. endocarditis)
• Residuals of other conditions
(i.e. hypertension, bicuspid, aortic valve
Aging Heart
• Size: can atrophy, remain unchanged or develop
moderate hypertrophy. The normal aging heart
demonstrates a modest in L ventricular wall thickness.
Possible enlargement of the L atrium and L ventricular
cavity.
• Cardiac myocytes: in size, not numbers (some
replaced with fibrous tissue). Cardiac myocytes
effective in reentering the cell cycle & proliferating,
partly offsetting cell loss due to necrosis or apoptosis.
• Amyloid deposition: half of those +70 years have some
amyloid deposits in the heart but mostly in small
amount & confined to the atria. Amyloid is not present
in all elderly persons, not even in centenarians.
Aging Heart
• Vasculature (atherosclerosis)
– Walls of large arteries thicken, vessels become
dilated and elongated
– Increase intimal thickness (due to cellular and matrix
deposition)
– Fragmentation of the internal elastic membrane
• Cardiac output (L x min)
– not decreased in healthy older men
– slightly decreased in older women
Age Associated Changes in Cardiac Function
1. Overall in systolic BP due to arterial stiffening
& in plus wave velocity. Reflects resetting of
the baro-receptor reflex to a higher level in the
elderly
2. Myocardial contractility: relaxation is
prolonged in senescent cardiac muscle due the
sarcoplasmic reticulum seugesters less Ca+2
3. Ejection Fraction (EF): no change in resting EF
4. Heart Rate (HR): supine HR does not change,
in sitting and standing positions from 10 to
25%.
Aerobic Capacity & Cardiovascular
Function During Exercise in the Elderly
With age, peak exercise capacity & peak oxygen consumption
slightly but inter-individual variation is substantial
Aerobic capacity 50% between 20 years to 80 years:
Maximal Cardiac Output (CO) 25%
Peripheral O2 utilization 25% (due to in muscle
mass & strength)
Although the stroke volume in older persons is
maintained, age apparently blunts the FrankStarling mechanism
Heart Failure:
Cardiac Output (CO) insufficient to meet physiologic demands
In the elderly, heart failure due to:
• Mostly systemic arterial hypertension
• Coronary artery & valvular diseases (due
to impaired cardiac filling & chronic
volume overload)
• Combined right & left cardiac failure
most common, but isolated occurrence of
left or right also probable
Heart Failure in the Elderly
• Symptoms: dyspnea, orthopnea, fatigue on
exertion and dependent edema
• Severity: classified according to the NY Heart
Association Scale
The Cardiomyopathies:
Myocardial disorders without a known
underlying cause
BUT
where other heart diseases may coexist
Dilated Cardiomyopathy
Hyperthrophic Cardiomyopathy
Restrictive Cardiomyopathy
Dilated
Cardiomyopathy
Normal Heart
Hypertrophic
Cardiomyopathy
Normal Heart
Restrictive
Cardiomyopathy:
The classic example
is the senile cardiac
amyloidosis of the
elderly, especially
over 95 years old.
Normal Heart
Cardiomyopathy: Any heart muscle disorder not
caused by coronary artery disease, hypertension or
congenital valvular or pericardial diseases.
Prevalence of heart failure:
25-54 yrs: 1%
55-65 yrs: 3%
65-74 yrs: 4.5%
+75 yrs: 10%
• > 75% of patients with heart failure +60 years of age
•Primary reason is Coronary Heart Disease (CHD)
•Secondary reason is Hypertension
•Third reason is cardiomyopathy
Sudden Death
• In young athletes (also in middle aged men),
SUDDEN DEATH can occur in patients with
congenital hypertrophic cardiomyopathy
– Usually due to severe arrythmia (ventricular fibrillation)
– If diagnosis is made a cardiac defibrillator should be
implanted.
• The SUDDEN DEATH of runners are usually limited
to 1 case per 15,000 runners per year-- hence, very
rare.
• MEMO: There is still the possibility of
ANAPHYLACTIC SHOCK in runners or walkers, if
stung by a bee.
Syncope in Elderly
Definition: temporary suspension of conciousness due to
cerebral ischemia
Causes
• Orthostatic Hypotension
• Vaso-Vagal Reflex (?)
• Arrhythmias (brady- & tachyarrhythmias)
• Drugs
– Antihypertensives (vasodilators/diuretics)
– Cardiac drugs: beta-blockers, digitalis, anti- arrhythmias, Ca+2
channel blockers, nitrates.
– Recreational: alcohol, marijuana and cocaine.
– Psychiatric: Antidepressants and phenothiazines
Contributory Causes to Heart Failure in the Elderly
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Hypertension (poor elasticity of arterial system)
Alcohol, but only if in excess
Viral infections
Autoimmunity
Heredity (specially for the cardiomyopathies)
Senile amyloid
Diabetes (due to the microvascular disease)
Arrhythmias and especially the TACHYCARDIAS
Conduction System in Aged Heart
• Sinoatrial Node: Increased fibrous tissue; seldom origin for
arrythmias
• Atrio-Ventricular Node: Slight increase in collagen fibers
• Bundle of His: Increased fibrous tissue with higher
frequency of First or Second degree heart block (the
mobitz)
• Also the possibility of: L or R BBB (Bundle Branch Block)
-this is seldom a complete heart block.
• In the conduction system fibrosis occurs: 40%
– Coronary Artery Disease : 20%
– Calcification : 10%
Normal ECG
Ventricular
Fibrillation
Atrial
Fibrillation
Aortic Stenosis:
Narrowing of the aortic orifice of the heart or of the aorta itself
A common condition due to:
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–
–
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Fatty alteration of collagen
Calcification
Rigidity and various degrees of aortic stenosis
Amyloid infiltration of the valves
Age Specific Lesion: The Valves
• Fibrous thickening at sites of closure
• Valvular sclerosis caused by collagen and elastic tissue,
this is a true wear and tear phenomenon
• Calcification of the mitral ring where fatty
degeneration invites deposition of calcium
– Calcifications is detected in 17 to 45% of patients over 90
years of age
– Complications include: heart blocks, infections, embolic