Download Chapter 10 Slides

HESS 509
Chronic Heart Failure
C
H
A
P
T
Chronic heart failure (CHF) is a serious, debilitating, and costly non
communicable condition that presently affects an estimated 5.8 million
Americans.
E
R
T
E
Currently, there are more than 670,000 new (incidence) cases of CHF
every year in the United States; the prevalence is projected to increase to
more eight million over the next 20 years.
N
By 2030, it is expected that one in every 33 (3%) Americans will have CHF,
with the direct and indirect costs of medical management projected to
increase from $39 to $70 billion per year.
HESS 509
C
Chronic Heart Failure
Basic Pathophysiology
H
A
P
T
E
R
T
Chronic heart failure, broadly defined as the inability of the heart to
adequately deliver oxygen to the body, is a not a disease but rather a
clinical syndrome that affects virtually all organ systems. This syndrome
occurs when cardiac output is reduced at rest, or especially during
exertion, and attributable to left ventricular systolic or diastolic
dysfunction or both. (not mentioned by text, but common cause is
chronic hypertension.)
E
N
Systolic Dysfunction – Impairment of left ventricular function likely due to
myocardial ischemia, myocardial infarction or Idiopathic (often post-viral)
Cardiomyopathy.
Systolic Dysfunction causes a reduction in left ventricular ejection fraction (LVEF)
and an increase in left end systolic volume. Thus, the result is a hypo-effective
heart in maintaining systemic circulation
HESS 509
C
Chronic Heart Failure
Basic Pathophysiology
H
A
P
T
E
R
T
E
N
Diastolic dysfunction: resistance to filling is increased in one or both
ventricles, causing elevated diastolic pressure in the ventricles, generally
because of reduced ventricular compliance (possibly due to scar tissue from
past myocardial infarction of ventricular hypertrophy from chronic
hypertension).
These systolic (contractile) and diastolic (relaxation or lusitropic [rate of
myocardial relaxation]) changes to heart function have both peripheral and
central hemodynamic consequences. The central circulation effects include the
following:
• Decreased cardiac output during exercise
• Compensatory ventricular volume overload (high preload)
• Elevated pulmonary and central venous pressures
• In severe cases, elevated left ventricular filling pressures when the person is
resting
Chronic Heart Failure
HESS 509
C
H
In addition to central hemodynamic abnormalities, the reduced cardiac
output in CHF results in peripheral circulatory effects as well:
A
P
T
E
R
• Major disturbances in skeletal muscle metabolism
• Impaired vasodilation
• Renal insufficiency (from poor perfusion), leading to
• Abnormal neuro-hormonal responses, and
• Pulmonary – ventilatory dysfunction
T
E
N
The consequences of this constellation of physiological changes result in the
cardinal signs and symptoms of CHF:
•
•
•
•
Fluid retention (resulting in pulmonary or peripheral edema)
Orthopnea (due to pulmonary edema)
Dyspnea on exertion (also from pulmonary edema)
Fatigue (generalized or localized to leg skeletal muscles, or both) Reduced
exercise tolerance (from all the above
Chronic Heart Failure
HESS 509
C
H
A
P
T
E
R
T
E
Management and Medications
Treatment of Chronic Heart Failure
Treatment for people with CHF has several key features:
•
•
•
•
Identifying and treating the underlying causes and risk factors
Regulating sodium and fluid balance
Pharmacologic therapy to reduce symptoms
Reducing adrenergic stimulation (decreasing cardiac stimulation and
afterload)
N
As CHF becomes more and more severe, more invasive approaches to
managing symptoms include the following: (see text for details on each
category below)
•
•
•
•
Oral or infused inotropic agents to improve contractility
Ventricular pacing to improve cardiac performance
Left ventricular assist device implantation
Cardiac transplantation
HESS 509
C
H
A
P
Chronic Heart Failure
Effects on the Exercise Response
The CHF syndrome results in a number of central, peripheral, and ventilatory
abnormalities that adversely influence the exercise response, irrespective of the
cause of CHF, including these:
T
E
R
T
E
N
• Reduction in cardiac output
• Mismatching of lung ventilation to perfusion (perfusion to ventilation ratio),
causing shortness of breath
• Leg fatigue during exercise due to inadequate blood flow to skeletal muscle
Altered baroreceptor reflexes have also been observed and may contribute to
diminished chronotropic responses or to reduced systolic pressure and reduction
in peripheral perfusion.
Peripheral abnormalities, including the following, also influence the response to
exercise in individuals with CHF
• Reductions in muscle blood flow
• Abnormal redistribution of blood flow
• Reduced vasodilatory capacity
• Endothelial dysfunction
• Abnormal aerobic metabolism biochemistry in skeletal muscle
Chronic Heart Failure
HESS 509
C
H
A
P
T
E
R
T
E
Effects on the Exercise Response
Abnormalities in skeletal muscle metabolism include reduced mitochondrial
enzyme activities, reduction of type I aerobic fibers and reduced contribution of
oxidative phosphorylation; the result is more metabolic acidosis.
As a consequence of these central and peripheral maladaptation, exercise
tolerance and quality of life are dramatically reduced in people with CHF. They
achieve only ~50% of the age-predicted VO2peak of healthy individuals, impairing
their ability to participate in activities of daily living
N
Journal Article - Congestive Heart Failure More Bad News From Exercising
Muscle?
HESS 509
C
H
A
P
T
E
R
T
E
N
Chronic Heart Failure
Effects of Exercise Training
Improvements after endurance training in CHF because of peripheral
adaptations:
• Improved skeletal muscle metabolism (strength training may also be of
benefit to help prevent muscle wasting)
• Improved endothelial function
• Increased vasodilatory capacity and redistribution of cardiac output
These peripheral changes overshadow central hemodynamic changes, which
include cardiac chamber volumes, ejection fraction, and pulmonary pressures
at rest and during exercise. Exercise therapy for individuals with CHF improves
physical functioning, quality of life, and morbidity and mortality.
HESS 509
C
H
A
P
T
E
R
T
E
N
Chronic Heart Failure
Recommendations for Exercise Testing
Exercise testing can be valuable in objectively characterizing the severity of CHF
and evaluating the efficacy of therapeutic interventions. The standard exercise
ECG usually offers little insight, and exercise intolerance can be more
appropriately characterized via these methods:
• Respiratory gas exchange response to exercise
• Quantification of work capacity
• Identification of the pathophysiological abnormalities
HESS 509
C
H
A
P
Chronic Heart Failure
Recommendations for Exercise Testing
The following considerations relate to exercise testing with this population (see
also table 10.1 – next slide):
T
E
R
T
E
N
• Symptoms are frequently observed under 5 metabolic equivalents (METs).
• Lower-level, moderately incremented, individualized protocols are
recommended (Naughton or ramp).
• Unstable or acutely decompensated CHF is a contraindication.
• Respiratory gas exchange measurements (including VO2peak, VT, VE/VCO2
slope) increase precision, optimize risk stratification, and permit assessment
of breathing efficiency and patterns.
• Six-minute walk tests supplement the graded exercise test but are not a
surrogate for measured respired gas analysis.
• Exertional hypotension, clinically significant dysrhythmias, and chronotropic
incompetence may occur in CHF, so 12-lead ECG should be monitored during
testing.
• Test endpoints should focus on symptoms, hemodynamic responses, and
standard clinical indications for stopping (not a target heart rate).
HESS 509
Chronic Heart Failure
C
H
A
P
T
E
R
T
E
N
Exercise Testing Considerations for CHF (FYI)
HESS 509
Chronic Heart Failure
C
H
A
P
T
E
R
T
E
N
Recommendations for Exercise Programming
Most individuals with CHF should:
• Be referred to cardiac rehabilitation,
• Follow the Basic Exercise Prescription Recommendations,
• and graduate to a home-based program aimed at maintaining physical
functioning.
Potential complications and outcomes for individuals with CHF differ
significantly compared to the standard cardiac rehabilitation population,
including the following:
•
•
•
•
Many individuals with CHF will deteriorate irrespective of interventions.
Risk of sudden death is higher.
Prevalence of psychosocial and vocational problems is higher.
Some individuals experience prolonged fatigue after only a single exercise
session.
Absolute contraindications to exercise in CHF include:
• Left ventricular outflow obstruction
• Decompensated CHF
• Unstable dysrhythmias
Chronic Heart Failure
HESS 509
Special Considerations for CHF
C
H
A
P
T
E
R
T
E
N
• Status can change quickly, and clients should be reevaluated frequently for signs of
acute decompensation, 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 clients may tolerate only limited work rates and may need lower-intensity
and longer-duration exercise sessions.
• Duration of activity may need to be adjusted to allow clients more opportunity to
rest and to progress at their own pace.
• Some clients may better tolerate discontinuous training involving shorter sessions
of exercise interspersed with periods of rest.
• Perceived exertion and dyspnea scales should take precedence over heart rate and
work rate targets.
• Isometric exercise should be avoided.
• Electrocardiogram monitoring is required for persons with a history of ventricular
tachycardia, cardiac arrest, or exertional hypotension.
• Consider ancillary study data (e.g., exercise echocardiogram, radionuclide studies,
hemodynamic studies, ventilatory gas analysis) when developing the exercise
program. In general, do not exceed a work rate that produces wall motion
abnormalities, a drop in ejection fraction, a pulmonary wedge pressure greater
than 20 mmHg, or the ventilatory threshold.
END