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Cardiac Pathophysiology Part B

Cardiac Pathophysiology Part B. 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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Cardiac Pathophysiology Part B

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  1. Cardiac PathophysiologyPart B

  2. 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

  3. 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

  4. Four broad consequences of heart failure • Congestion – blood backs up • Activation of circulatory compensations • Cardiac output declines • Death

  5. Types of Heart Failure • High output vs. Low output • High output • Anemia • Septicemia • Hyperthroidism (thyrotoxicosis) • Beriberi • Low output • Decreased pumping ability and cardiac output

  6. 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

  7. Systolic vs. Diastolic HF • Systolic – decreased contraction leads to decreased output and poor perfusion of tissues

  8. 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

  9. 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

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. 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

  15. 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

  16. Major causes: • Hypertension – induced myocardial hypertrophy and myocardial ischemia with ventricular remodeling • Aortic valvular disease • Mitral valvular disease • Cardiomyopathies

  17. Signs and symptoms are similar to systolic heart failure • Diagnosis made by echocardiography and heart cateterization

  18. 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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