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Determinants Of Exercise Capacity In Patients With Left Ventricular Dysfunction As Assessed By Six-Minute Walk Test

Contact Person: Nikolay P Nikitin (nimed@silk.org)


Clinical, hemodynamic and echocardiographic characteristics of the patients are given in Table 1. Twenty eight patients were in NYHA functional class I, 44 patients in class II and 44 patients in class III. The study patients were taking a variety of medications, including angiotensin-converting enzyme inhibitors, diuretics, digitalis, beta-blockers, nitrates and aspirin.

Table 1. Characteristics of the study patients
Age (years) 55+/-11
Weight (kg) 76+/-13
Heart Rate (beats/min) 82+/-12
Systolic Arterial Pressure (mm Hg) 130+/-21
Diastolic Arterial Pressure (mm Hg) 82+/-12
NYHA class 2.14+/-0.78
Left Atrial Size (mm) 45+/-7
LV Mass Index (g/m2) 140+/-43
LV End-Systolic Volume Index (ml/m2) 77+/-36
LV End-Diastolic Volume Index (ml/m2) 120+/-38
LV Ejection Fraction (%) 34+/-6
Isovolumic Relaxation Time (ms) 79+/-25
Peak Velocity of Early Filling (m/s) 0.54+/-0.13
Peak Velocity of Atrial Filling (m/s) 0.42+/-0.14
PE/PA ratio 1.47+/-0.64
Deceleration Time of Early Filling (ms) 140+/-29
Data are expressed as mean value +/- SD. NYHA, New York Heart Association; LV, left ventricular; PE/PA ratio, ratio of early wave to atrial wave peak velocity.

Only one patient was unable to perform the 6 MW test, 9 patients completed the walk with breaks in continuity. The mean distance walked was 277+/-114 m. Hemodynamic, echocardiographic and Doppler-derived variables correlated with 6 MW test distance on univariate analysis are listed in Table 2. A significant inverse correlation also existed between NYHA functional class and 6 MW test distance (r=-0.435, p=0.000).

Table 2. Correlations between six-minute walk test distance and hemodynamic, echocardiographic, and Doppler-derived parameters
Parameter r Regression equation p Value SEE
HR -0.362 y=552.56-3.35 x 0.000 107.14
SAP 0.255 y=100.37+1.36 x 0.006 111.15
DAP 0.219 y=108.13+2.06 x 0.019 112.15
LA size -0.378 y=540.96-5.82 x 0.000 106.43
LVM index -0.436 y=438.26-1.15 x 0.000 103.46
LVESV index -0,549 y=411.52-1.74 x 0.000 96.04
LVEDV index -0.512 y=464.11-1.56 x 0.000 98.76
LVEF 0.509 y=-35.82+9.25 x 0.000 98.93
IVRT 0.580 y=70.32+2.62 x 0.000 93.61
PE -0.413 y=469.85-358.00 x 0.000 104.66
PA 0.802 y=3.81+658.98 x 0.000 68.72
PE/PA ratio -0.778 y=481.30-138.50 x 0.000 72.23
DT 0.618 y=-64.36+2.44 x 0.000 90.37
r, correlation coefficient; SEE, standard error of the estimate; HR, heart rate; SAP, systolic arterial pressure; DAP, diastolic arterial pressure; LA, left atrial; LVM, left ventricular mass; LVESV, left ventricular end-systolic volume; LVEDV, left ventricular end-diastolic volume; LVEF, left ventricular ejection fraction; IVRT, isovolumic relaxation time; PE, peak velocity of early filling; PA, peak velocity of atrial filling; PE/PA ratio, ratio of early wave to atrial wave peak velocity; DT, deceleration time of early filling; y, six-minute walk test distance; x, respective parameter.

The strongest univariate determinants of 6 MW test distance were Doppler-derived indices of LV diastolic filling. When the multivariate regression analysis was performed, only PA wave velocity (F to enter 192.71, multiple R = 0.79), PE/PA ratio (F to enter 115.22, multiple R = -0.37), and heart rate (F to enter 80.98, multiple R = -0.12) emerged as independent determinants of 6 MW test distance.

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Nikitin, NP.; (1998). Determinants Of Exercise Capacity In Patients With Left Ventricular Dysfunction As Assessed By Six-Minute Walk Test. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Available at URL http://www.mcmaster.ca/inabis98/medicine/nikitin0578/index.html
© 1998 Author(s) Hold Copyright