Download Maximal Exercise Tolerance in Chronic

Maximal Exercise Tolerance in Chronic
Congestive Heart Failure*
Relationship to Resting Left Ventricular Function
Edgar S. Carell, MD; Srinivas Murali, MD; Douglas S. Schulman, MD;
Tulio Estrada-Quintero, MD; and Barry F. Uretsky, MD
The relationship between maximal exercise tolerance
and resting radionuclide indexes of left ventricular systolic and diastolic function were evaluated in 20 ischemic and 44 idiopathic cardiomyopathy patients with
New York Heart Association class 2-4 chronic congestive
heart failure. Left ventricular ejection fraction, peak
systolic ejection rate, peak diastolic filling rate, time to
peak filling from end-systolic volume, and fractional
filling in early diastole were measured from the radionuclide ventriculogram. All patients underwent symptom-limited exercise testing with on-line measurement
of oxygen consumption. In the ischemic group, all of the
radionuclide indexes correlated poorly with maximal
exercise oxygen consumption (Vo2max) except the peak
systolic ejection rate which correlated modestly (r=0.58,
p<0.05). Peak systolic ejection rate was significantly
lower (p<0.01) as were the peak diastolic filling rate and
fractional filling in the first third of diastole (p<0.05)
in ischemic patients with marked exercise intolerance
(Vo2max-14 mL/kg/min) compared with those with
preserved exercise tolerance (Vo2max >14 mL/kg/min).
In the idiopathic group, none of the radionuclide indexes
correlated well with Vo2max; and all indexes were similar
in patients with and without marked exercise intolerance.
Impaired exercise tolerance is the most frequent
symptom of chronic congestive heart failure
(CHF).' Previous studies in CHF patients have
shown a poor correlation between resting indices of
left ventricular systolic function and indices of maximal exercise tolerance.2-5 There is speculation that
resting right ventricular ejection fraction may predict exercise tolerance in some patients, although this
is controversial.4'6'7 Diastolic left ventricular dysfunction defined as an impairment of ventricular
relaxation, abnormal chamber stiffness, or muscle
stiffness often accompanies systolic dysfunction in
the majority of chronic CHF patients and may be an
important determinant of symptoms, functional capacity, and possibly survival.6'8'10 A few small studies
have suggested a direct correlation between exercise
*From the Division of Cardiology, University of Pittsburgh
School of Medicine, Pittsburgh.
Manuscript received January 19, 1993; revision accepted February 14, 1994.
These data suggest that (1) resting left ventricular ejection
fraction poorly predicts maximal exercise capacity in
both ischemic and idiopathic cardiomyopathy and
(2) resting peak systolic ejection rate, peak diastolic
filling rate, and fractional filling in early diastole may
predict exercise tolerance in ischemic but not idiopathic
(Chest 1994; 106:1746-52)
cardiomyopathy.
CHF=congestive heart failure; FF= fractional filling in the
first third of diastole; HRPFR=peak diastolic filling rate
normalized to resting heart rate; LVEF=left ventricular
ejection fraction; NYHA=New York Heart Association;
PFR=peak diastolic filling rate; SER=normalized left
ventricular peak systolic ejection rate; TPF=time to peak
filling from end-systolic volume; Vco2max=maximal carbon dioxide production; VEmax= maximal minute ventilation; Vo2max=maximal oxygen consumption
Key words: congestive heart failure; exercise tolerance;
left ventricular diastolic function; left ventricular systolic
function
tolerance and left ventricular diastolic filling in CHF
patients.11'12 Heart failure patients with preserved
exercise tolerance have been shown to have a higher
peak diastolic filling rate during exercise compared
with those with marked exercise intolerance.5 The
majority of patients in these studies, however, had
CHF because of ischemic heart disease. Whether left
ventricular diastolic filling predicts exercise tolerance
in CHF patients who suffer from idiopathic cardiomyopathy has not been carefully studied.
The objective of our study was to compare the relationship between maximal exercise tolerance and
resting left ventricular systolic and diastolic function
in chronic CHF patients with ischemic cardiomyopathy to those with idiopathic cardiomyopathy.
METHODS
15261
Study Patients
Sixty-four patients with left ventricular systolic dysfunction
(left ventricular ejection fraction .45%) and New York Heart
Association (NYHA) functional class 2-4 chronic CHF, who were
referred to our Cardiac Functional Testing Laboratory for func-
1746
Maximal Exercise Tolerance in Patients with Chronic CHF (Carell et al)
Reprint requests: Dr. Murali, University of Pittsburgh Medical
Center, 538 Scaife Hall, 3550 Terrace Street, Pittsburgh, PA
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Table 1-Characteristics of Study Patients
Mean age, yr
Ischemic
Idiopathic
(n=20)
(n=44)
49+11
57+10
(range, 33-73) (range, 21-81)
Sex
Male
Female
NYHA class
2
3
4
Exercise parameters
Exercise HR, beats/min
Exercise BP, mm Hg Systolic
Diastolic
VE, L/min
Vco2max, L/min
Vo2max, mL/kg/min
Anaerobic threshold Vo2
*Probability value less than 0.05.
18
2
36
8
7
27
15
2
7
6
141 ± 34
140 + 29
78 ±11
57 + 20
1.5 ±0.9
14.0+5.6
11.9 +4.5
158 + 26*
155 + 28
80+9
59 + 22
1.9+ 1.0
17.4 +5.6*
13.6 +4.3
tional capacity assessment were retrospectively studied. The CHF
was due to either ischemic (n=20) or idiopathic cardiomyopathy
(n=44). Ischemic patients had angiographically documented
multivessel coronary artery disease and idiopathic cardiomyopathy patients had CHF in the absence of significant coronary
disease, valvular disease, hypertensive or hypertrophic heart disease or heart disease due to systemic illness. Patient characteristics are listed in Table 1. This idiopathic patient group was significantly younger than the ischemic group.
Exercise Tolerance Assessment
Maximal exercise testing was performed in all patients who
were in the postprandial state using either an incremental multistage treadmill protocol (Modified Naughton Protocol) with
2-min stages'3 or an electronic bicycle ergometer protocol
(Wasserman Ramp protocol) starting at a workload of 10 W and
increasing it by 10 w every minute.14 All patients exercised until
the development of severe dyspnea or leg fatigue. Patients who
discontinued exercise due to angina were excluded from the
study. All patients were on a stable medical regimen comprising
digoxin, diuretics, angiotensin-converting enzyme inhibitors, nitrates, hydralazine, and antiarrhythmic drugs in various combinations at the time of the exercise test. None of the medications
were withheld on the day of the test. No patient was receiving
either 3-adrenergic blockers or calcium-channel blockers. During
each test, continuous on-line breath-by-breath measurement of
minute ventilation, oxygen consumption (Vo2), and carbon dioxide production was performed using a Sensormedics Metabolic
Cart. Lactate threshold or onset of anaerobic metabolism (anaerobic threshold) was noninvasively derived from the aforementioned metabolic parameters, using previously described criteria.15 17 The exercise data were comparable in the two groups
except that the idiopathic patients achieved a significantly higher
maximal exercise heart rate and Vo2 (Vo2max) compared with
ischemic patients (Table 1).
parallel hole collimator. The study was formatted at 32 frames per
cardiac cycle. The best left anterior oblique position that separated the left ventricle from the right ventricle and left atrium was
chosen. Using a commercial computer program (SAGE), semiautomatic regions of interest were generated over the left
ventricle for each frame in the cardiac cycle using a combined
second derivative and count threshold algorithm. A background
region was automatically generated lateral or inferior to the left
ventricle in the end-systolic frame, thus avoiding overlap with
high-count background area in the spleen or descending aorta.
From the regions of interest, a high temporal resolution background corrected left ventricle time activity curve was obtained.
Left ventricular ejection fraction (LVEF) was calculated as left
ventricular end-diastolic counts minus left ventricular endsystolic counts divided by left ventricular end-diastolic counts.
The time activity curve data was fitted using a fourth Fourier
transform series. The maximum first derivative during diastole
was used to establish peak diastolic filling rate (PFR) which was
then normalized to end-diastolic counts. Since PFR is affected by
heart rate, it also was normalized to resting heart rate (HRPFR). '8
The time to peak filling from end-systolic volume (TPF) and
fractional filling in the first third of diastole (FF) were derived.'9
Peak systolic ejection rate (SER) also was determined from the
maximum first derivative during systole of the time activity curve.
Data Analysis
Based on the Vo2max, ischemic and idiopathic groups were
arbitrarily divided into those with relatively preserved maximal
exercise tolerance (Vo2max >14 mL/kg/min) and those with
impaired maximal exercise tolerance (Vo2max '14 mL/kg/
min). This arbitrary classification was based upon previously described survival differences in these groups.20 Student's t test was
utilized for comparison of data between ischemic and idiopathic
cardiomyopathy groups and between patients with relatively
preserved exercise tolerance and those with impaired exercise
capacity. Analysis of variance was used to compare data among
patients stratified by NYHA functional class. Correlations between radionuclide indexes and exercise variables were performed using the Pearson product moment correlation. Kendall
rank correlation was used to correlate radionuclide and exercise
parameters with NYHA functional class. Statistical significance
was defined as a probability value of less than 0.05. All data are
expressed in mean ± SD.
RESULTS
Radionuclide Data
All resting radionuclide parameters were comparable in the ischemic and idiopathic patient groups
(Table 2). The LVEF, SER, and PFR were considerably reduced in both groups (normal LVEF, 69 + 7%;
SER, 3.6 ± 0.7 end-diastolic count [EDC]/s; PFR,
3.2 ± 0.7 EDC/s); TPF and FF also were lower (normal TPF, 138 + 28 ms; FF, 40 ± 16%). Resting heart
Table 2-Resting Radionuclide Data
in the Study Patients
Parameters
Radionuclide Angiography
Each patient also underwent multiple gated blood pool cardiac
scintigraphy at rest in the supine position. Red blood cells were
labeled using standard in vivo techniques with 25 mCi of
technetium 99m. Imaging was done with a General Electric
Starcam mobile camera equipped with a medium sensitivity
LVEF, %
SER, EDC/s
PFR, EDC/s
TPF, ms
FF, %
Ischemic
(n=20)
Idiopathic
(n=44)
25+10
27±9
1.3 ± 0.7
1.3 ±0.6
1.4 +0.6
1.3 ±0.5
117+41
28±10
128±62
Probability
23+12
CHEST / 106 / 6 / DECEMBER, 1994
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NS
NS
NS
NS
NS
1747
3.0
50
40
1.5
-1
20
10 15 20 25 30
V02 max (ml/min/kg)
3.5
3.0 C) 2.5-1
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1.5 - *
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C))
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I
5I
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0.01
5z.
r=.58
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-
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r=.45
a.
cn
18
5 10 15 20 25 30
V02 max (ml/min/kg)
0.00
5 10 15 20 25 30
V02 max (ml/min/kg)
250
200
en
150-
*~~~~~
r=.32
r=.-10
50
1.5:)
1 .C
0.C
0.C
v- 0.0,
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r
10
15
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25
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5
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= 0.0'
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5 10 15 20 25 30 35
V02 max (ml/min/kg)
0.0(
25C
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-
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ae
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25
30
V02 max (ml/min/kg)
FIGURE 1. Correlation between resting radionuclide measures of
left ventricular function and maximal exercise tolerance in
ischemic cardiomyopathy patients. Correlation with Vo2max was
(p=NS) for LVEF, PFR, TPF, and FF but modest and significant (p<0.05) for SER and HRPFR.
poor
was
21
In
."
-
5C _
*
a
r=. 15
a
V02 max (ml/min/kg)
comparable in both
per minute).
groups
(82 ± 17
vs
90 ± 16 beats
Relationship Between Resting Radionuclide Data
and Maximal Exercise Capacity
In the ischemic group, resting LVEF, PFR, TPF,
and FF correlated poorly (p=NS) with Vo2max
(r=0.38, 0.34, -0.10, and 0.32, respectively); howthere was a modest significant correlation with
SER (r=0.58; p<0.05) and HRPFR (r=0.45; p<0.05
[Fig 1]). On the other hand, in the idiopathic group,
Vo2max correlated poorly (p= NS) with resting LVEF
(r=0.21), PFR (r=0.25), SER (r=0.21), TPF (r=0.15),
ever,
FF (r=-0.14), and HRPFR (r=0.18 [Fig 2]).
In both groups, the resting LVEF was similar in
patients with preserved (Vo2max >14 mL/kg/min)
and impaired (Vo2max S14 mL/kg/min) exercise
tolerance (Fig 3). The PFR was significantly less in
ischemic patients with impaired exercise tolerance
(1.09+0.53 vs 1.63±0.50 EDC/s, p<0.05) as were
HRPFR (0.013 ± 0.007 vs 0.022 ± 0.009 EDC/s/beats
per minute; p<0.05) and FF (31.2 ± 9,4 vs
49.6±11.0%, p<0.O1). The SER also was signifi1 748
2.g
2.C
10
0 1
rate
I
r= -14-
50
5
(ml/min/kg)
max
0.
ioo
*
I0 %-r=.25
10 15 20 25 30 35
V02
E 00
70
60
50
40
-
n
5
10 15 20 25 30 35
V02 max (ml/min/kg)
5
3.5
3.C
a
o 0.02
I
0.0
0
30
1.0
r~. 0.5
10
~0la 0.03
0.0
70
60
50
40
30
20
10
r=.34
0.04
eto
1
* *
*
a
2.0
1 .5
-1
20
V02 max (ml/min/kg)
-
.
a)u
30
1.0
0.0 5
5
5
2.5
40
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a
0.5 -_
10
3.0
50
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2.0
0
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E3
T
2.5
5
10
V02
15 20 25 30 35
max
D
5
10 15 20 25 30 35
(ml/min/kg)
V02 max (ml/min/kg)
FIGURE 2. Correlation between resting radionuclide measures of
left ventricular function and maximal exercise tolerance in idiopathic cardiomyopathy patients. All measures of resting left
ventricular systolic and diastolic function correlated poorly
(p=NS) with Vo2max.
cantly lower in ischemic patients with poor exercise
tolerance (1.05 ±0.5 vs 2.1 ±0.8 EDC/s; p<0.01),
but there was no difference in TPF. In the idiopathic
patient group, PFR, HRPFR, SER, TPF, and FF all
were similar in patients with and without preserved
exercise tolerance. In both groups, change in heart
rate with exercise (maximal exercise heart rate minus
resting heart rate) was significantly lower in patients
with impaired exercise tolerance compared with
those with preserved exercise tolerance (44±32 vs
88 ± 26 beats per minute, p<0.01, in ischemic patients and 56 ± 23 vs 75 ± 13 beats per minute,
p<0.01, in idiopathic patients).
Relationship of Radionuclide and Exercise Data
to New York Heart Association Functional Class
There were no significant differences in the radionuclide indexes among NYHA class 2, 3, and 4 patients (Table 3). Resting LVEF, SER, PFR, TPF, and
FF correlated poorly with NYHA functional class
(r=-0.19, -0.29, -0.24, -0.17, and -0.21, respectively). There was a significant correlation between
Vo2max and NYHA functional class (r=-0.80,
Maximal Exercise Tolerance in Patients with Chronic CHF (Carell et al)
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p40.01
30
a
0
2-
20i
lw
rr,~ "
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0o
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...
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KOCHEMIC
IDIOPATHIC
IDIOPATHIC
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P'0., 5
40.0
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IDIOPATHIC
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IDIOPATHIC
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IDIOPATHIC
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FIGURE 3. Resting radionuclide measures of left ventricular function in ischemic and idiopathic cardiomyopathy patients by degree of exercise impairment. The SER, PFR, HRPFR, and FF were significantly (p<0.05) lower in idiopathic cardiomyopathy patients with marked exercise intolerance (Vo2
.14 mL/kg/min, open bars) compared with those with preserved exercise capacity (Vo2max >14
mL/kg/min, hatched bars).
p<0.01). This relationship was evident even when
the ischemic and idiopathic patient groups were analyzed separately. Maximal exercise heart rate, maximal minute ventilation (VEmax), Vo2max, and Vo2 at
anaerobic threshold were significantly lower in
NYHA class 3 and 4 patients compared with class 2
patients (Table 4). Further, the maximal exercise
Table 3-Relationship of Radionuclide Parameters to
New York Heart Association Class
heart rate and Vo2max were significantly lower in
class 4 patients compared with class 3 patients.
DISCUSSION
Exercise Tolerance in Congestive Heart Failure
Since chronic CHF patients often are symptomatic
only during exertion, it is important to assess their
functional status in terms of their exercise tolerance.21'22 Clinical classification of CHF severity such
NYHA functional class relies solely upon the patient's subjective assessment of his or her degree of
physical impairment and may therefore be inadequate in grading CHF.2223 Objective assessment of
exercise tolerance by noninvasive measurement of
as
Parameters
LVEF, %
SER, EDC/s
PFR, EDC/s
TPF, ms
FF, %
NYHA
Class 2
NYHA
Class 3
NYHA
Class 4
(n=34)
(n=22)
(n=8)
28±8
1.6±0.6
1.4 +0.5
134 ±50
29±11
25±11
1.2 ±0.7
1.2 ±0.5
123±41
25±9
24±9
1.1±0.5
1.4 ±0.5
115 +47
21±12
Table 4-Relationship of Exercise Parameters to New
York Heart Association Class
Class 2
NYHA
Class 3
NYHA
Class 4
Parameters
(n=34)
(n=22)
Exercise HR, beats/min
Exercise BP, mm Hg
169±24
140±21*
(n=8)
117±25ft
155 ± 25
81±9
68 ± 20
2.4±0.9
20.5 ± 4.7
15.8+3.9
151±35
78 ±10
49 ± 17*
125 ± 18t
75 ±12
42 ± 191
NYHA
Systolic
Diastolic
VEmax
Vco2max
Vo2max
Anaerobic threshold Vo2
1.2±0.5*
0.8±0.41
12.8 ± 1.3*
8.4 ± 1.1 f I
10.7±2.0*
7.8±1.3t
*Probability value less than 0.01, NYHA class 3 vs class 2.
IProbability value less than 0.01, NYHA class 4 vs class 2.
4Probability value of less than 0.05, NYHA class 4 vs class 3.
Vo2max (aerobic capacity) and anaerobic threshold
during incremental upright exercise therefore has
been suggested as a more reliable measure of functional status in chronic CHF patients.22 Maximal exercise Vo2 or Vo2max is determined by cardiac output response to exercise and maximal oxygen extraction.24 Oxygen extraction by metabolizing tissues is
not generally impaired in chronic CHF patients'5
and may in fact be augmented when compared with
normal subjects.25-27 Therefore, Vo2max primarily
reflects the level of cardiac output achieved during
maximal exercise, ie, cardiac reserve. Impaired exercise tolerance in chronic CHF, however, is not only
related to skeletal muscle underperfusion, but also to
peripheral abnormalities such as impaired peripheral
vasodilatory capacity, muscle atrophy, and decreased
oxidative metabolism.28-30
In this study, none of the resting radionuclide
measures of left ventricular systolic or diastolic
CHEST / 106 / 6 / DECEMBER, 1994
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1749
function correlated with NYHA functional class. In
fact, there were no significant differences in any of
the radionuclide indexes among the different functional classes. Correlation between Vo2max and
NYHA class was good but not excellent in both
ischemic and idiopathic cardiomyopathy patients.
Thus, it would seem that although subjective NYHA
functional class assessment is a somewhat reliable
measure of functional capacity in CHF patients, it
has limitations.
Left Ventricular Systolic Function and
Exercise Tolerance
The results of our study confirm the previous observation that resting left ventricular ejection fraction does not accurately predict maximal exercise
tolerance in chronic CHF.253' The LVEF did not
correlate well with Vo2max, whether CHF was due
to ischemic or idiopathic cardiomyopathy, and there
was no difference in the resting LVEF between patients with relatively preserved exercise tolerance
and those with impaired exercise tolerance. Most
previous studies describing the lack of correlation
between resting LVEF and exercise tolerance in
CHF patients involved small study populations composed predominantly or entirely of patients with ischemic heart disease.2-5 Baker et a14 reported a poor
correlation between LVEF and Vo2max (r=0.08), in
25 men with chronic CHF, 12 of whom had ischemic
heart disease. Franciosa et a12 also described a poor
correlation (r=0.06) between resting LVEF and exercise time in 21 chronic CHF patients, 16 of whom
had ischemic cardiomyopathy. The inability of resting LVEF to predict exercise tolerance in chronic
CHF may relate to several mechanisms. Exercise
tolerance may be preserved in some patients with
poor left ventricular systolic function because of the
ability to tolerate elevated pulmonary artery wedge
pressures without developing dyspnea, increased
pulmonary lymphatic flow that limits pulmonary
venous congestion, preservation of appropriate chronotropic response, adequate left ventricular dilatation during exercise, ability to further activate the
already stimulated neurohormonal mechanisms and
chronic changes in left ventricular compliance that
limit augmentation of filling pressures during exercise.6 Further, right ventricular dysfunction may
coexist, particularly in patients with idiopathic cardiomyopathy and exercise may precipitate ischemia
in some ischemic heart disease patients.32
The relationship between resting SER and exercise
tolerance has not been systematically evaluated previously. Both resting and exercise SER previously
have been shown by Heo et a15 to be similar in
ischemic patients with normal exercise tolerance and
severe exercise intolerance. There are no data corre1 750
lating SER to exercise tolerance in idiopathic cardiomyopathy patients. In the present study, SER was
reduced in both ischemic and idiopathic patients.
There was a modest correlation between resting SER
and Vo2max in ischemic patients. Further, patients
with ischemic disease and impaired exercise tolerance had a significantly lower SER than those with
preserved exercise tolerance (1.05 ± 0.5 vs 2.10 ± 0.80
EDC/s; p<O.Ol). The discrepancy between our findings and those of Heo et a15 may relate to the fact that
Vo2max and not exercise time was used as the measure of exercise tolerance in our study. The Vo2max
is considered a more reliable measure of maximal
exercise tolerance, since unlike exercise time it is reproducible33 and less influenced by body size, state of
conditioning, and physician and patient motivation.24 Like resting LVEF, SER demonstrated a poor
correlation with Vo2max in idiopathic patients. Unlike in the ischemic groups, there were no differences
in SER among idiopathic cardiomyopathy patients
with impaired and preserved exercise tolerance. The
reason for this differential relationship between SER
and Vo2max in the two groups is unclear.
Left Ventricular Diastolic Function and Exercise
Tolerance
Left ventricular diastolic filling abnormalities are
frequently seen in association with decreased left
ventricular systolic function in chronic CHF second-
ary to both ischemic and idiopathic cardiomyopathy.8'1034 Mechanisms include myocardial ischemia, alteration in the physical properties of the myocardium due to myocyte destruction and fibrosis,
increased sympathetic nervous system activity with
f-1-receptor down regulation causing reduced myocardial relaxation rate and change in loading conditions.9 Resting PFR in both groups in this study were
similar and considerably lower than normal. Resting
PFR correlated poorly with NYHA functional class;
and correlation between resting PFR and Vo2max
was poor in both groups. In contrast to idiopathic
cardiomyopathy patients, however, ischemic patients with impaired exercise tolerance had a significantly lower PFR compared with those with preserved exercise tolerance. Soufer et al"l previously
reported in a small study that resting PFR was a good
predictor of maximal exercise Vo2 in CHF patients.
However, in that study only 9 patients were evaluated; the mean LVEF was 40% suggesting a somewhat different patient population compared with the
present study; and majority of patients had left ventricular dysfunction secondary to ischemic disease.
We also noted a moderate correlation between HRPFR and Vo2max in ischemic patients. The HRPFR
also was significantly lower in ischemic patients with
impaired exercise tolerance compared with those
Maximal Exercise Tolerance in Patients with Chronic CHF (Carell et al)
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with preserved exercise tolerance, and this difference
was not apparent in the idiopathic group. Perhaps the
mechanism for exercise intolerance is different in
patients with ischemic and idiopathic cardiomyopathy. Ischemic patients in our study who had lower
PFRS may have had significant silent myocardial ischemia at rest and therefore a poorer exercise tolerance. Further, silent myocardial ischemia induced by
exercise may have increased left ventricular stiffness,
thus contributing toward a rapid rise in left ventricular filling pressures and limiting exercise tolerance.5
This interesting hypothesis also may explain the lack
of correlation between resting PFR and exercise tolerance in idiopathic cardiomyopathy patients. Further studies are needed to clarify if this, in fact, is the
case.
Other measures of diastolic function such as TPF
and FF were also reduced in both groups and correlated poorly with NYHA class. The TPF and FF
correlated poorly with exercise tolerance in both ischemic and idiopathic cardiomyopathy patients.
However, like PFR, FF was significantly lower in ischemic patients with poor exercise tolerance compared with those with preserved exercise tolerance.
Limitations
Our findings have to be interpreted in the context
of certain limitations. First, exercise studies and radionuclide angiography were not performed on the
same day. The studies were done within 3 months of
each other, and there may have been intercurrent
change in the patient's left ventricular systolic or diastolic function between the two tests. Every effort
was made to ensure that patients were clinically stable between the tests, thus making a significant
change less likely. All the exercise studies were conducted after the patient was familiarized with the
exercise laboratory and personnel with an initial test.
Second, patients were on various medical regimens
for the treatment of CHF, and we cannot exclude
possible influences of drug therapy on the study results. The different relationships observed between
radionuclide parameters and exercise tolerance in the
ischemic and idiopathic patient groups could be explained by the different medical regimens in the two
groups. Every patient was maintained on a stable
medical regimen between the time of radionuclide
study and the exercise test, and none of the ischemic
heart disease patients developed angina during exercise. Finally, limitations of the radionuclide ventriculogram in accurately measuring diastolic function should also be borne in mind.35
CONCLUSION
Despite these limitations, we can draw several
conclusions from this study. Subjective assessment of
NYHA functional class in CHF patients correlates
well with objective measures of maximal exercise
tolerance but not measures of resting left ventricular
systolic or diastolic function. Resting LVEF is a poor
predictor of maximal exercise tolerance in patients
with CHF due to ischemic or idiopathic cardiomyopathy. Resting SER, PFR, and FF may be useful in
predicting maximal exercise tolerance in ischemic
but not idiopathic patients. Larger, prospective studies are needed to confirm these observations.
ACKNOWLEDGMENT: We thank Alfred Cecchetti for assistance with statistical analysis and Margaret Altvater for preparation of the manuscript.
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3 Higginbotham MB, Morris KG, Conn EH, et al. Determinants
of variable exercise performance among patients with severe
left ventricular dysfunction. Am J Cardiol 1983; 41:51-60
4 Baker BJ, Wilen MM, Boyd LM, et al. Relation of right
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