The Importance
of Maximal Graded Exercise
Testing in the Diagnosis
and Treatment of Eating Disorders
Susie
McMinn, M.S.
Exercise
Physiology
Pediatric
Cardiology Associates
Dallas,
Texas
Background
I
currently administer maximal GXTs to pediatric patients who visit our practice
with potential heart problems. A growing portion of that population
is eating disorder patients. In response to this increasing demand,
we established an eating disorder clinic including a cardiologist, exercise
physiologist, nutritionist, psychologist, and a nurse practitioner to administer
a complete rehabilitation program. Our current recovery protocol
has developed over the last 3 years in response to what we have learned
about the physiological and psychological course of recovery for this diverse
and difficult population. Maximal exercise stress testing has become
an important part of that process.
The
Patients
Most
of our patients are female, between the ages of 11 and 18. They come
to us with varying degrees of an eating disorder, but most have quantifiable
cardiac problems including:
atrophy
of ventricle walls and decreased cardiac muscle mass
incompetent
(leaky) cardiac valves
systolic
dysfunction
bradycardia
arrthymias
chest
pain
low
blood pressure
decreased
amplitude of T wave and QRS complex
increase
in QT interval (especially with rapid weight loss)
autonomic
alteration of HR variability (HR max suppressed)
In addition
they are usually withdrawn, angry and are actively denying their problem.
They are also usually taking an antidepressant.
Rehabilitation
Initially,
we used maximal exercise testing early in the rehabilitation process to
access cardiac vulnerability during exercise. We quickly learned
that exercise testing needed to be delayed to later in the recovery process
for several reasons. In the early days of our program at least half
of our exercise tests were positive for arrthymias. We often saw
cardiac dysfunction during exercise testing despite normal resting ECGs
and echocardiograms. In addition, we had trouble dealing with patients
who were still denying the severity of their problem. Although denial
continues to be a problem for most of our patients regardless of the amount
of time they have been in our program, delaying our maximal exercising
tests until 3 months into rehabilitation has resulted in fewer positive
tests and a greater ability to communicate with the patients about healthy
exercise habits.
Most
of out patients use exercise as a means of controlling body weight and
therefore, often abuse it. They are very anxious to reach the exercise
testing stage of our rehabilitation, so we have been able to use it as
a reward for diligent nutritional and psychological work by the patient.
Also, we needed to refeed these patients and obtain normal resting ECGs
and echocardiograms prior to exercise testing in order to ensure that our
rehabilitation process was safe for the patient.
There
is no classic eating disorders patient. From our experience over
the last three years, we have realized that these patients are not easily
stereotyped. Therefore we have instituted a conservative approach
to rehabilitation that employs broad parameters so that all patients can
safely recover from the above-mentioned cardiac complications. During
the first 3 months of rehabilitation the patients are completely restricted
from exercise. Instead they are required to focus on weight gain
and psychological and family problems
After
our patients complete 3 months of refeeding and psychological counseling
they perform a maximal treadmill test using the modified Bruce protocol.
They must first obtain clearance from their nutritionist and psychologist
before testing. We do not test any patients who arrive at the lab
and have lost weight as of their last visit, have a resting HR < 50
or a systolic BP < 90 mmHg.
Exercise
rehabilitation involved 3 maximal stress tests at 3 month intervals with
modest but increasing exercise prescriptions in the interim. If any
ground is lost in terms of weight or psychological problems we restrict
exercise and restart that portion of the rehabilitation from the beginning.
Exercise poses a risk for these patients not only because of the physical
consequences of their starvation, but due to their extreme and unhealthy
exercise habits. We attempt to teach them moderation and to respect
the physical consequences of their eating disorder and excessive exercise.
Summary
Eating
disorder patients are not easily described or understood. They come
in all shapes and sizes and attempting to find commonality between them
regarding their psychological problems is very difficult. However,
certain cardiac dysfunctions are extremely common in this group including,
bradycardia, cardiac wall thinness, incompetent (leaky) cardiac valves
and low blood pressure. Maximal exercise stress testing has been
invaluable to our diagnostic and rehabilitation effort with these patient.
We believe that it is an essential part of eating disorder rehabilitation,
despite the infrequency of its use in many rehabilitation programs.
In
addition, we have noticed a significant number of patients, at least during
their first maximal exercise test, who were unable to generate a maximal
heart rate (> 15 beats lower that predicted HR max) despite lengthy exercise
test times and the appearance of maximal exertion. We suggest that
this may be evidence of altered autonomic control of HR variability, and
seems to be one of the last symptoms to abate during rehabilitation.
This question is an excellent research problem for anyone interested in
exercise and eating disorders.
Copyright
©1997-2000 American Society of Exercise Physiologists. All Rights
Reserved.
ASEP
Table of Contents
Questions/comments
