Download Cardiac Pathophysiology B

Cardiac Pathophysiology
Part B
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Heart Failure
• The heart as a pump is insufficient to meet
the metabolic requirements of tissues.
• Can be due to:
– dysfunction of the left ventricle
– dysfunction of the right ventricle
– or due to inadequate perfusion despite
normal or elevated cardiac output
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Classification of Heart Failure
• Acute –develops quickly
• Chronic – conditions gradually increase
demands on the heart; when the heart and
circulatory system can no longer adapt the
result is heart failure
– Can lead to acute failure with excessive
cardiac demand
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Four broad consequences of
heart failure
•
•
•
•
Congestion – blood backs up
Activation of circulatory compensations
Cardiac output declines
Death
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Types of Heart Failure
• High output vs. Low output
• High output
– Anemia
– Septicemia
– Hyperthroidism (thyrotoxicosis)
– Beriberi
• Low output
– Decreased pumping ability and cardiac output
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• Right-sided vs. Left sided Heart Failure
• Right-sided HF
– Most common cause is left heart failure
– Can occur independently in primary lung
disease conditions
• COPD, ARDS, cystic fibrosis
• Cor pulmonale
• Left-sided HF
– Decreased output to body
– Blood backs up
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Systolic vs. Diastolic HF
• Systolic – decreased contraction leads to
decreased output and poor perfusion of
tissues
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Contractility is reduced by diseases
that disrupt myocyte activity
– Most common cause is myocardial infarction
– Myocarditis
– Myocardopathies
• When contractility decreases, stroke
volume decreases, and left ventricular
end-diastolic volume (LVEDV) increases.
• This causes dilation of the heart and
increased preload
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Preload can also increase with
excess plasma volume
– I.V. Fluid administration
– Renal failure
– Mitral valve disease
• Increased LVEDV at first increases C.O.,
but over time can cause dysfunction of
sarcomeres (stretched too far) and
decreased contractility
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Increased afterload is usually due
to increased peripheral resistance
– Hypertension
• Left ventricle works harder to overcome
resistance, and hypertrophies.
• Hypertrophy causes changes in the myocytes.
• Also see deposition of collagen between
myocyctes which can disrupt contractility and
make ventricle more likely to dilate and fail.
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Leads to increased blood pressure
and pulmonary congestion →
– Dyspnea
– Orthopnea – difficulty breathing in any
position other than upright
– Coughing up frothy sputum
– Chest pain –due to hypoxia at heart
– Fatigue/confusion
– Skin is pale, cold, sweaty
– Pulse and lung sounds abnormal
– Decreased urine output
– Edema
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Treatment is aimed at breaking the
cycle of decreasing contractility and
increasing preload and afterload.
• Oxygen, nitrates and morphine – improve
myocardial oxygenation, help relieve
coronary spasm while lowering preload
through systemic vasodilation.
• I.V. inotropic drugs such as dopamine or
dobutamine – increase contractility of the
heart and can raise B.P. in hypotensive
individuals.
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• Diuretics – reduce preload
• ACE inhibitors – reduce preload and
afterload by decreasing aldosterone levels
and reducing peripheral venous resistance
• Beta-blockers have been helpful in some
people
• Coronary by-pass
• Salt restriction
• Heart transplant
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Diastolic Heart Failure
• See symptoms and signs of heart failure, a
preserved ejection fraction, and abnormal
diastolic function
• Accounts for 25 -40% of all cases of heart
failure
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Diastolic H.F. Results from:
• Decreased compliance of left ventricle and
abnormal diastolic relaxation- results in
increased pressure in ventricle at the end
of diastole
• Pressure is reflected back into the atrium
and pulmonary circulation
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Major causes:
• Hypertension – induced myocardial
hypertrophy and myocardial ischemia with
ventricular remodeling
• Aortic valvular disease
• Mitral valvular disease
• Cardiomyopathies
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Signs and symptoms are similar to
systolic heart failure
• Diagnosis made by echocardiography and
heart cateterization
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Management
• Improve ventricular relaxation and prolong
diastolic filling times to reduce diastolic
pressure
• Calcium channel blockers, beta-blockers,
and ACE inhibitors have been used with
success
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