JACC Vol. 16. No. 1 July 1990:80-1

80

ALAIN COHEN SOLAL, MD, JEAN MARC C~A~E~NA~~,

MD, RENfi ~~~~~~N,

Paris, France

lotion of oxy~ uptake(~~*~ da~ng exe* from relstionsestablished in normalsubjectsbetweenVOZand worklOadin watts(W) maybe inaccurate in patientsWith chronic hetul failure because thesepatientscouldmanifest delayed$41zkineticsat finalstagesof exercise.‘fo test the ~y~t~~~ thatevenat lowlevelsof work,~tien~ exhibit a lower$%I& thando~rna~ sobj~, 77~~~~ withheart fathweand27controlsubjectswitha normalbeartor witb d&ease otherthanheartfailureunderwentbicycleexercise withrespiratory gasanalysis.Workloadwasincreased by 10 W/I& freman initial29 W. V02 0mlhln per kg) was measured every15s. TheAV~~AWratiowass~g~fi~tty reduced onlyin themostseverely tm~ir~ stank in heart

In patients with chronic heart failure, exercise capacity is limited because of fatigue or dyspnea, or both. maximal oxygen uptake has been proposed as an index of circulatory reserve in these patients, necessitating respiratory gas analysis during exercise-an expensive. complex and sometimes poorly tolerated technique (l-3). it is generally assumed that during exercise the oxygen uptake ~~0~) at identic~ work lpad and the slope of the relation between the increase of VOzand the increase of work are not different in the patient with mild chronic heart failure and the normal subject (4)for submaximalexercise. For these reasons, it has been considered that $4 could be predicted without respiratory gas analysis. Others (5,6) have found a reduced slope of the relation between ir02 and work load (AqO.JAW)in patients with circulatory disorders, suggesting that peripheral muscles require anaerobic metabolism to perform work. HowFver, measuring this slope only from the rest and the final VOZcan be misleading because a reduced slope calculated

Fromthe !kvice de Cardiologie. Hopital Bichat. Paris, France. This Work was suworted by @ants from the Soci&! FranCake de Cardiologie. the Federation Franpbe de Cardiologie and the Institut National des Sciences et de Ia Recherche akin, paris. M~usC~Pt received Cktober 24. 1989; revised ~us~~pt received Jamtar~ 24,1990. accepted February 12.1990. &&S&&UU: Alain Cohen !%I. MD, Service de Cardiotogie. HopiU Bichat, 46 me Hem-i Huchard. 75018 Paris. France. QEXQ by the American College of Cardiology

faibareChEsC-D ~~‘95 0.05). Qass B patients s of 280 W, whereasclass ratio at Z20 W. en witha low incremental workrateprotect, cornwith bench ~rrn~ subjects or patientswtt~out pa s ob~rvationsagger t both;accordingly, indirectestimatesof VU&~~ut~rne~~ derivedfrom intensityor duratianof exercisein sack ~~~~ areover~t~mat~.

by this methodcolaid ue trJ redM~edirOt nineties only at the end of exercise. , little is known about the kinetics of the increase in $‘O, during bicycle exercise in patients with chronic heart failure of various degrees of severity. To answer the ques:ion concerning patients with chronic heart failure exhibiting a reduced %‘02only al the end of exercise or from the be~nnin~ of exercise, we have compared 60, stage by stage in a large population of patients with various degrees of chronic heart failure and in sedentary subjects without heart failure. S lady ~a~~~ (TableI). Among patients who entered the institution for chronic heart failure between 1986and 1988, 77 (64 men, 13 women) who exercised with a IO W/min protocol were considered for this study. Ages ranged from 28 to 70 years (mean 51 k 9). Thirty idio~~t~i~~ardi~myo~athy~12 ~s~~~rn~~ c mitral stenosis, 12aortic reg~~~tat~o~,5 and 1 chronic constrictive pericarditis. All patients with cardiomyopathy had an ejection fraction ~40% or an enlarged left ventricle (~ho~ardiogr~hic left ventricular diameter >3 corned, Admin~stra~~~sf drugs was ant sto before the test; most of the patients were receivingdiuretics and none had pulmonary congestion or significantperipheral edema at the time of the test. All patients stopped exercise

CHF = chronic heart failure; F = female; M = male; Peak iJO = peak oxygen uptake: subgroups C C-D adapted from Ref 2: values are mean values + SD (*p < 0.05 versus control): male/female ratio was not statislically different between each chronic hearl failure group and the conld group khi-square and two-tailed Fisher’s exact test).

>20

mYrGn

per kg); 25 in da

measu

72 years (beam 42 c 1% The m

subjects with (n = 7) or

ing to clinical, radio~og~~and ech~ardiogra~h~~ exions; only patients with a peak Vcll, >20 mllmin per g were selected for this study (Table 1).

rest period, work rate was increased in all patients by IOW each minute after an initial 26)W work load. y gas analysis was performed 11system wits the use of xi& (~~~~ a~~~y~~~s.In was measured with a jewelmounted turbine with the temperature continuoclsly monitored. The oxygen analyzer is a polygraphic sensor, the carbon d~~%~de analyzer an infrared optical system. Oxygen Mater and carbon dioxide production (~~~*~ were calculated from standard fo~u~as. Data were processed on line by a microprocessor programmed to correct for delays between signals for volume and gas concentration. to per-

decrease in the h dis etween a decrease o between %QZand work load, and the end of exercise with the same slope, we measured VS, stage by stage. Values are here reported every 2 min and calculated by the mean of the three values obtained during the last 45 s of each stage (to compensate for possible ~Mct~atio~sof %Q). As the aumber of patients decreased as work load increased, we considered only the first tO min of exercise. Statistics. Values are reported as mean values 2 SB.

to identify groin differences. ~oatrol subjects and chronic heap f~~ore then matched by age by aKan~i~g control and failure-%and control and chronic heart faila order of ascending age. Beginning with the Y

JACC Vol.16.No. I July199o:SO5

COHENSOLALETAL. OXYGENUPTAKEINCHRONlCHEARTFAlLURE

82

Table

Table2. The AirO,/AWRatio(mUminof 0, per watt) AirO,lAW I I .05_+0.38 11.44f 1.48(-3.6;17.2) 10.05r 1.61(-18.0: 3.7) 8.75 + 2.14*(-31.4: -8.8) 10.22+ 2.04

Control CHF-A CHF-B CHFGD CHF

4. Age-Matched ComparisonBetweenthe ControlGroup

and the ChronicHeartFailure-BGroup

Valuesare mean values + SD (*p < 0.05 versus control withthe95% confidence interval limits); abbreviationsas in TableI.

subject, each was matched within 2 years to a chronic heart failure-Bor chronic heart failure-Cpatient. For the matching process, patients with chronic heart failure were drawn randomly from each range of 2 years. Comparison was carried out with a paired t test. A value of p < 0.05 was considered significant.

Characteristic No. Age Male/femaleratio Weight Peak 90, (mUminper kg) Ai’O_JdW (m!/miaper W) 60, rest ire, 20 W *0,40 w iro,6Ow 902 a9 w \ioz 100w

p Value

Control

CHF-B

12 522 11 IOM.2F 67 c 8 25.5 r 4.5

12 51 + IC lOM,2F 692 12 17.02 1.0*

co.001

11.0* 1.7

9.5 z 1.2*

co.05

4.1 f 0.6 9.3 I? 1.3 12.0+ 1.1 14.8? 1.8 17.5+ 2.2 20.5 f 2.7

4.7 !I 1.3 a.1 + 1.7 10.5r 2.0* 12.7+ 1.8* 14.2+ l.O* 16.3+ 0.7*

-

co.05 co.05 co.05 CO.aOl

Groupswere idehticalregardingage, male/femaleratio and body weight; the AvOz/AWratio was significantlylower in the CHF-B group: i’Oz was lower in this latter group beginning with the 40 W stage; abbreviations as in Table I.

AjrO,/AW ratio (Table2). At rest, VO, was not different groups. The AirO,lAWratio was not different in the chronic heart failure (10.2 f 2.0) and the control groups (11.O2 0.3). Only the chronic heart failure-C-D group had a Airo,/AW ratio significantly lower than that of the control group. In the chronic heart failure-B group, the lower ratio failed to achieve significantdifferencewith the control group (95%confidence interval for the difference between means: -18.0; 3.7). No difference was found between the control and_the chronic heart failure-A groups. VO, duringexercise(Table3). During exercise, although consider?ble variation in VO, within each group was observed, VOz was significantly lower in the chronic heart failure group compared with the control group. Patients in group A were not different from control subjects, but irOz became lower as the severity of circulatory failure increased from A to C-D; moreover, this difference appeared more rapidly during exercise as circulatory failure increased from A to C-D. For both results, the difference between the con&okand the chronic heart failure-C groups remained significantwhen the four patients of group D were excluded. TO rule out the possibility that the lower VO, in the chronic heart failure group was in part due to the slightly lower age of chronic heart failure B and C-D groups than among

that of the control group, we matched by age within 2 years in ascending order the control group and the chronic heart failure-B and chronic heart failure-C groups. i’Oz and the Aq02/AWratio remained lower than control in chronic heart failure-B and chronic heart failure-C patients (Tables 4 and 5).

qOz during exercisein patients with heart failure. No prior study has assessed the difference in the kinetics of the increase of irO* during bicycle exercise in such a large population of patients (n = 77) with heart failure. Our study demonstrates that, with this protocol, VO, measured by respiratory gas analysis is lower at identical work load in patients with chronic heart failure than in subjects without heart failure. Moreover, this difference increases with the degree of circulatory failure and in class C-D, VO, is lower than control beginning with the tirst stages of exercise. Finally, considerable intragroup variation for ir0, was observed even indexed to body weight, invalidating the estimation of vOz from the usual nomograms in patients with chronic heart failure.

Table3. OxygenUptake ([email protected]) During Exercise Rest Control CHF-A CHF-B CHF-C-D CHF

4.15 + 0.77 4.34 + 1.14 4.32 -c 1.13 3.88 + 0.74 4.20 2 1.05

20 w 9.01 + a.98 2 8.31 + 7.42 + 8.30 2

1.36 1.91 1.61 1.09* 1.70

40W 11.43+ Il.19 2 10.382 9.25 + 10.39+

1.61 2.26 1.67 1.66* 2.05*

60W 14.11+ 14.03+ 12.87i: 10.77c 12.94?

2.15 2.84 i.% 1.65* 2.61*

Vtiues are meanvaluesf SD (*p < 0.05versus control); abbreviationsas in Table I.

80 W 17.042 17.19f 15.00+ 12.16+ 15.53*

2.54 3.05 1.a5* 1.63* 3.07*

1OOW

12ow

19.76+ 2.94 19.28+ 2.83 16.67+ O.%= 13.75+ 1.86* 18.07+ 2.89+

22.66 2 3.54 21.66 r 2.88 18.252 0.07* 14.19r 0.02* 20.67 + 3.47

JACC Vol. 16, No. 1 July 1990:80-5

Age-Matched ‘Chronic Heart Characteristic

w?x’GEN

COHEN SOLAL ET AL. UPTAKE lN CHRONK

3

Comparison Failure-C G p Value

Control 12

NO.

482

Age Male/female

ratio

10

10&i, 2F

Weight

IF 2 8

Peak 90, (mUmin per kg)

26 -c 5

AiJOzlA W (mVmin per W)

11.2 = 1.5

8.0 + I.S*

Comparison of oxygen uptake during bicycle exercise in patients with chronic heart failure and in normal subjects.

Prediction of oxygen uptake (VO2) during exercise from relations established in normal subjects between VO2 and work load in watts (W) may be inaccura...
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