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Chronic Heart FailureChapter 12

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Pathophysiology

Chronic heart failure (CHF) is characterized by poor cardiac output

Individuals with CHF have depressed systolic function, abnormal diastolic function, or a combination thereof.

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Depressed systolic function (decreased contractility) leads to depressed cardiac output.

Decreased diastolic function is characterized by: •increased resistance to ventricular filling, and •resultant increased ventricular pressure, •higher than normal filling pressures, and •reduced ventricular compliance.

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Several central hemodynamic changes areassociated with CHF:•decreased cardiac output during exercise, or in severe cases at rest•elevated left ventricular filling pressures•compensatory ventricular volume overload•elevated pulmonary and central venous pressures.

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CHF is associated with secondary organ changes

•impaired skeletal muscle metabolism,•renal insufficiency leading to sodium and water retention (edema formation).

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Signs and Symptoms of CHF•fatigue, •dyspnea•reduced exercise tolerance.

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Effects on the Exercise ResponseThe major problem of the patient with CHF is the reduction in cardiac output relative to the demands of the exercise load.•Poor cardiac output underlies a mismatching of ventilation to perfusion in the lung, causing an elevation in physiologic dead space and leading to shortness of breath.•Early fatigue is related to the heart's inability to supply adequate blood flow and oxygen to the working muscles.•Ionotropic (down-regulated receptors) and chronotropic (down-regulated baroreceptors) response of the myocardium is blunted.

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Effects on the Exercise Response

The cumulative effect of peripheral changes in skeletal muscle with CHF is a reduced exercise tolerance as a result of greater glycolysis (increased lactic acidosis, leading to hyperventilation), and reduced oxidative phosphorylation (reduction in ATP supply), reduced type I fibers, and increased type II.

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Effects of Exercise Training

Exercise training may cause improvements in:

•in exercise capacity from peripheral adaptations(e.g., improvements in skeletal muscle metabolism, endothelial function, vasodilatation capacity, and distribution of cardiac output) •rather than from cardiac (central) changes (e.g., central hemodynamics including volumes, ejection fraction, and pulmonary pressures at rest and during exercise).

Research studies have demonstrated that exercise training neither harms nor results in significant benefit to the myocardium in CHF patients

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Recommendations for Exercise Testing (pg. 95, text, next slide)•symptoms are frequently observed under 5 METs, so lower level, moderately incremented, normalized protocols are recommended (Naughton or ramp)•symptoms indicative of unstable or uncompensated CHF are a contraindication•respiratory gas exchange measurements increase precision, optimize risk stratification, and permit assessment of breathing efficiency and patterns; these are particularly useful in clients with CHF•exertional hypotension, clinically significant dysrhythmias, and chronotropic incompetence may occur in CHF•test endpoints should focus on symptoms, hemodynamic responses, and standard clinical indications for stopping (and not target heart rate)

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Recommendations for Exercise Programming (pg. 96, text, table below)

•Peripheral improvements can increase ADL’s, increase functional capacity, and delay disability.•Many patients with CHF will deteriorate irrespective of exercise or medical therapy.•Many patients will experience prolonged fatigue following the exercise session•CHF patients are at higher risk of sudden death

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Recommendations for Exercise Programming

•Status can change quickly, and clients should be reevaluated frequently for rapid changes in weight or blood pressure, worse-than-usual dyspnea or angina on exertion, or increases in dysrhythmias.•Warm-up and cool-down sessions should be prolonged.•Some patients may tolerate only limited work rates and may necessitate lower intensity / longer duration exercise sessions.•Perceived exertion and dyspnea scales should precedence over heart rate and work rate targets.

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End of Presentation