Download Effects of Exercise Training

HESS 509
Heart Transplantation
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Heart transplantation is the gold standard treatment for selected individuals
with end-stage heart failure who continue to have symptoms despite optimal
medical and device therapy.
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Heart transplantation significantly improves quality of life and dramatically
increases survival (90% and 70% after 1 and 5 years, respectively, with a median
survival of 10 years).
Despite receiving a healthy heart in an orthotopic heart transplant (which
involves the complete removal of the recipient’s own heart), most people
continue to experience some exercise intolerance due to peripheral muscle
dysfunction and reduced aerobic capacity.
HESS 509
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Heart Transplantation
Effects on the Exercise Response
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Because the donor heart’s innervation is transected in order for the heart to be
transplanted, immediately after transplantation there is no parasympathetic
or sympathetic innervation to the heart.
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Some people demonstrate signs of partial cardiac re-innervation, so most
heart transplant recipients must rely on circulating catecholamines to
provide adrenergic stimulation to the heart.
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This results in heart transplant recipients having different heart rate (HR)
and hemodynamics, both at rest and during exercise, when compared to
healthy individuals with a normal heart. Thus,
• Resting HR is increased ~20 beats/min.
• Onset of increased HR is delayed for the first several minutes of
exercise.
• This is followed by an increase in HR that is more gradual than normal.
• Peak HR is slightly lower than normal (~150 beats/min)
• Heart rate may remain near its peak value for several minutes during
recovery.
• Return to resting levels is delayed
HESS 509
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Heart Transplantation
Effects on the Exercise Response
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The systemic circulation is also affected by heart transplantation because the
heart is denervated, which disrupts the baroreflex control mechanisms
(baroreceptors are also present in the auricles of the heart and vena cava),
that maintain the balance between cardiac output and vascular resistance.
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Thus,
• Blood pressure at rest is often mildly elevated.
• Systolic pressure is lower than normal at peak exercise.
• Cardiac output is lower than normal at peak exercise (≈60-70% peak
cardiac output compared to that in age-matched healthy
controls)
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Heart Transplantation
Effects of Exercise Training
The clinical and physiological benefits of exercise training in heart
transplantation recipients include the following:
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Resting HR and blood pressure are lower.
Maximal HR is higher.
Peak VO2 and VO2 at ventilatory threshold are higher.
Submaximal exercise endurance is improved.
Blood lactate concentrations are lower at the same work rate.
Ventilatory efficiency improves.
Exertional fatigue and dyspnea are diminished
HESS 509
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Heart Transplantation
Management and Medications
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Medical management of organ transplantation requires immunosuppressive
drug (see Table 14.1 below – FYI )
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Controlling immune system rejection of the donor heart and avoiding the
adverse side effects of immunosuppressive therapy are thus primary
concerns following heart transplantation. Acute graft rejection is common,
especially within the first year.
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Heart Transplantation
Recommendations for Exercise Testing
Exercise testing for heart transplant recipients can be done with either a
treadmill or a stationary cycle ergometer and should follow a conservative
exercise testing protocol that has relatively small increases in work rate per
stage - e.g., 0.5-1.0 metabolic equivalents
Measuring respired gases allows accurate quantification of functional
capacity . Peak VO2 in untrained cardiac transplant recipients is generally
≤20 to 25 mL O2 · kg−1 · min−1
Although isolated cases of chest pain associated with accelerated graft
atherosclerosis have been observed, autonomic denervation reduces the
likelihood of angina symptoms, especially during the initial months or
years following surgery when partial re-innervation is less likely.
Radionuclide testing is more useful for diagnosis of ischemic heart disease
than the ECG.
Only professionals who are experienced with exercise testing in highrisk populations should perform an exercise test in a heart transplant
recipient
HESS 509
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Heart Transplantation
Recommendations for Exercise Training
Exercise training is strongly recommended for this population, including both
aerobic and resistance exercise.
• Improvements in peak VO2 range between 15% and 40%
• Resistance exercise is also strongly encouraged, with the goal of
improving muscle strength and bone density and to prevent the
adverse effects that antirejection medications have on skeletal
muscle. During upper-limb strength or flexibility evaluations,
sternal precautions should be strictly observed in the initial
weeks or months following heart transplantation.
• The use of HR alone to guide exercise intensity is not appropriate
in this population. It is not uncommon for heart transplant
recipients to achieve an exercise HR that exceeds 85% of measured
peak HR. Combined assessment of systolic blood pressure
and rating of perceived effort (RPE) (recommended range 11-14
out of 20) is a better gauge of exercise training intensity
HESS 509
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Heart Transplantation
Recommendations for Exercise Training
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Important considerations during exercise programming:
• Progress conservatively, as severe deconditioning is common, especially if
prolonged bed rest was required before surgery.
• Intermittent exercise throughout the day may be needed until longer,
continuous exercise can be tolerated.
• Range of motion and stretching exercises are important for the upper body
to restore normal thoracic biomechanics after sternotomy. However, these
exercises should be limited for up to 6 to 8 weeks after surgery.
• The RPE is the preferred method of monitoring exercise intensity,
particularly as the individual progresses to an independent exercise
program.
• Longer periods of warm-up and cool-down are indicated because the
physiological responses to exercise are delayed.
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