Racial differences in electrocardiograms and vectorcardiograms between black and white adolescents

J. ELECTROCARDIOLOGY 18(4), 1985, 309-314

Original Communications Racial Differences in Electrocardiograms and Vectorcardiograms Between Black and White Adolescents 9By P. SVAMASUm)AR RAO, MD, FAAP, FACC

SUMMARY In a previous s t u d y of 244 normal children, we detected higher leftward, posterior and inferior voltages in blacks than in whites in two groups: 6- to 10-year-old children and in 11- to 14-year-old boys; no difference was found in 3-to-5-year-old children, or 11- to 14-yearold girls. The purpose of this study was to determine if such race-related voltage differences are also present in 15- to 19-year-old adolescents. Biographic data, blood pressure and hemoglobin values, electrocardiogram (ECG), Frank vectorcardiogram (VCG) and echocardiogram were obtained in 59 normal 15- to 19-year-olds (28 blacks and 31 whites); 144 measured parameters and 57 computed variables were analyzed. Many sex-related differences (p<0.05 to 0.001) were seen in both races. R in leads I, AVL and V G, S in Vl, and sum of Svl and Rv6 in the ECG and X to left, terminal X to right and Y inferior in the VCG were higher (p<0.05 to 0.01) in black males than in white males. However, no such differences (p>0.05) were observed between black and white females. To understand the causes of these differences, comparison of the biographic data, blood pressure, hemoglobins and echocardiograms were made. The height, weight, body surface area, chest circumference, A P diameter of the chest, diastolic and systolic blood pressure and left ventrieular (LV) dimension were similar (p>0.1) in all groups. The hemoglobin was lower in blacks than in whites (p<0.05 to 0.01) in both males and females; therefore, it is unlikely to be responsible for the ECG-VCG differences seen in male teenagers. The LV posterior wall was thicker, and the anterior chest wall to mid-LV distance was shorter in black males than in white males. No such racial differences were observed in females. These findings strongly support the theory t h a t thicker LV located closer to the leads used in ECG recording is responsible for increased voltages in ECG and VCG in 15- to 19-year-old black males. Based on these data, it is recommended t h a t in evaluating ECG and VCG voltages, separate normal standards should be used for blacks and whites as well as for males and females of this age group.

In a recent study, 1 we presented electrocardiographic (ECG) and vectorcardiographic (VCG) data of 244 black and white children between the ages of 3 and 17 years and demonstrated the following: a) sex-related ECG-VCG amplitude differences were clearly evident from early adolescence onward in both black and white children; b) higher leftward, posterior and inferior ECG-VCG voltages were present in blacks than in whites in the 6- to 10-yearold children and 11- to 14-year-old boys. No such race-related amplitude differences were observed in 3- to 5-year-olds and 11- to 14-year-old girls; and c) the observed racial difference could not be explained

on the basis of differences in age, weight, height, body surface area, systolic and diastolic blood p r e s s u r e s , h e m o g l o b i n level, a n d echocardiographically determined left ventricular (LV) cavity size. However, the LV posterior wall was thicker and the anterior chest wall to mid-LV distance was shorter in blacks than in whites, but only in 6- to 10-year-olds and 11- to 14-year-old males in whom the ECG-VCG differences were observed. Based on these data, it was recommended t h a t separate normal standards be used for evaluation of ECG and VCG voltages in black and white children over six years of age. Separate normal standards are also suggested for males and females older than 11 years of age. In t h a t study, the number of subjects over 14 years of age was small; therefore, these subjects were excluded from further analysis.' The purpose of this paper is to present the ECG and VCG data of a larger group of 15- to 19-year-olds to document the sex- and racerelated differences in these adolescents.

From tile Department of Pediatrics,MedicalCollegeof Georgia. Augusta. Georgia, U.S.A., and the King Faisal Specialist Itospital and Research Centre, Riyadh, Saudi Arabia. Reprint requests to: Dr. P. Syamasundar Rao, Consultant Pediatric Cardiologist,King FaisalSpecialist Itospital, I'D. Box 335.1, Riyadh 11211. Saudi Arabia.

309

310

RAO ET A L

Height, weight, blood pressure, chest circumference, anteroposterior (AP) diameter of the chest, hemoglobin, twelve-lead standard ECGs, VCGs using the Frank lead placement system, and M-mode echocardiogram were obtained as previously detailed. '-:3 Ninety-four measurements from each ECG, 20 measurements from the VCG and 13 measurements from the echocardiogram were made again, a s i n the previous study.' Several of the same calculations' were made including the anterior chest wall to mid-LV distance.' Statistical analysis was performed as previously described.'

MATERIALS AND METHODS A total of 59 black and white children of both sexes, including 20 teenagers from the previous study, ~ between the ages of 15 and 19 years, were studied. The subjects were from neighborhood day care centers and from child and youth clinics, or they were children of hospital employees of the Medical College of Georgia. A written, informed consent was obtained in each case. Each child was examined, and children with cardiovascular abnormalities were excluded. Table I

Sex Comparison in 14-19-Year-Old Children RACE VARIABLES

BLACK SEX

MEAN

WHITE

__SD

p VALUE

MEAN

__SD

p VALUE

S,

M F

2.2 1.0

1.9 0.5

< 0.05

2.2 1.2

1.6 1.2

Svl

M F

16.0 9.9

7.2 3.7

< 0.01

11.5 10.6

4.8 3.8

9Rv,,

M F M F

9.8 6.0 24.2 12.7

5.6 3.0 11.1 3.2

< 0.05

8.5 5.5 19.9 15.6

4.6 2.9 6.0 4.6

Rv,

M F

19.4 15.4

7.9 3.4

< 0.05

17.6 12.3

6.7 4.6

< 0.02

Sv4

M F

8.9 4.2

4.7 2.5

< 0.01

12.0 4.2

4.8 2.1

< 0.01

Rv5

M F

22.7 14.9

7.0 6.0

< 0.01

19.8 11.8

5.2 5.1

< 0.001

Sv5

M F

4.5 2.1

3.1 1.1

< 0.01

5.4 2.1

2.2 1.4

< 0.001

Rv6

M F

17.7 12.4

4.6 3.1

< 0.01

14.4 10.1

4.0 2.7

< 0.01

Svl + Rv6

M F

33.7 22.3

8.1 5.7

< 0.01

14.4 10.1

4.0 2.7

< 0.01

S w + Rv5

M F

36.9 23.7

12.3 5.7

< 0.001

31.3 22.4

8.5 5.8

< 0.01

Sv2+ Rv5

M F

45.1 22.6

17.6 5.3

< 0.001

39.7 27.4

10.0 5.8

< 0.01

X to Left

M F

1.80 0.95

0.45 0.35

< 0.001

1.30 0.93

0.38 0.17

< 0.001

X term to Right

M F

0.23 0.06

0.21 0.11

< 0.01

0.39 0.11

0.21 0.17

< 0.001

Y to inferior

M F

1.49 1.10

0.31 0.20

< 0.001

1.27 1.11

0.32 0.38

> 0.1

Z to Anterior

M F

0.67 0.36

0.26 0.09

< 0.001

0.65 0.34

0.25 0.15

< 0.001

Z to Posterior

M F

1.10 0.43

0.34 0.24

< 0.001 _

1.10 0.61

0.38 0.24

< 0.001

Sv2

< 0.01

< 0.05

> 0.1

< 0.05 < 0.05

The electrocardiographic voltages are in mm (1/10 millivolts) and the vectorcardiographic voltages are in millivolts.

J. ELECTROCARDIOLOGY 18 (4), 1985

RACIAL DIFFERENCES IN ECG AND VCG

311

data are not presented here b u t are available from the author) were compared between blacks and whites; no statistical differences (p>O.1) were found.

RESULTS Of the 59 adolescents, there were 31 whites and 28 blacks (33 males and 26 females}, of which there were 15 black males, 13 black females, 18 white males, and 13 white females. Sex-related differences were first s o u g h t in each racial group. Male teenagers had higher leftward, inferior and/or posterior voltages (p<0.05 to 0.001) in the ECGs and VCGs ('lhble I); this was true for both blacks and whites. Therefore, racial comparisons were made in the age-sex matched groups. The heart rate, P wave duration, PR interval, QRS duration, QT interval, P and T wave amplitudes, patterns of QRS complex, and vectorcardiographic loop rotations (the

In the 15- to 19-year-old boys, the electrocardiographic R,, R w,., Sv,, Rv6 and sum of Sv, and Rv6 and vectorcardiographic X to the left, terminal X to the right and Y inferior were higher in blacks than in whites with a p<0.05 to 0.01 (Fig. 1A). In the 15- to 19-year-old girls, no E C G or VCG differences (p>0.1) were observed; a few important ECG-VCG parameters are shown in Fig. lB. The biographic data, namely age, weight, height, body surface area, chest circumference and A P diameter of the chest, were similar for blacks and whites as were the systolic and diastolic blood

15-19 Years Males, Black vs. White 60

9 Black

~ ,5 vQ.

[ ] White Mean + S D

50

'~

t 6 5

1

50

Fig. 1A. Figure showing a comparison of voltage amplitudes of the QRS complex of the ECG and VCG between 15- to 19-year-old black and white males. Note significantly higher voltages in blacks than in whites, with p<0.05 to <0.01.

1'

v

d

5

~

o

,

0

0

RI

RAvL

SVI

RV6

SvI§

X Left

E.C.G.

Y

Inf.

~C.G.

15-19 Years Females, Black vs White

6O

9 Black [] White

50 o

Mean

+

s

D

~_ 40 o - v_.% -

"-: O ^

E E 50 -= o

-

0

^ I0

o.

u') q

20

T

A

~

~

q =

-6 ->

--. 0^

^ =

^ =

,~

I

2

I o

o

RI

RAVL

SVI

RV6

SvI~Rv6

E.C.G.

J. ELECTROCARDIOLOGY 18 (4), 1985

X Left

Y Inf.

V.C.G,

Fig. lB. Comparison of selected ECG and

5 "~ :~ VCG voltage data in the 15-19-year-old

females between blacks and whites did not reveal any statistically significant dif:~ ferences (p>0.1). - -

312

RAO ET A L

olds. ~ Biographic data and blood pressure (Table I I) did not account for these racial differences. The fact that hemoglobin levels were lower in black males than in white males (Table If) could have explained the racial differences, b u t the fact that hemoglobin differences were also found in female s u b j e c t s m a k e s it u n l i k e l y t h a t t h e lower hemoglobin levels in black males is the cause for ECG-VCG differences. Although the LV size, as measured echocardiographically, was not different, the LV posterior wall was thicker and the anterior chest wall to mid-LV distance was shorter in black males than in white males (Fig. 2A). This may account for ECG-VCG amplitude differences. No racial differences in LV wall thickness or in anterior chest wall to mid-LV distance were found in female subjects (Fig. 2B). Thus, this s t u d y of 15- to 19year-olds bridges the gap between our previous study,' wherein racial difference were documented in 3- to 14-year-olds, and those of adults (extensively referenced in our previous paper') showing marked racial ECG-VCG voltage differences. Other studies of sex- and race-related ECG-VCG differences in children and adults were reviewed in our previous publication' and will not be disucssed

pressures (Table II). The hemoglobin values were 9lower (p<0.05) in the black teenagers than in whites (Table II). The left ventricular (LV) internal dimension in diastole measured from the echocardiogram (Figs. 2A and 2B) was not significantly different (p>0.1). However, the LV posterior wall was thicker (p<0.05) and the anterior chest wall to mid-LV distance was shorter (p<0.05) in black males than in white males (Fig. 2A). No such differences were detected in 15- to 19-year-old females in whom racial differences in ECG-VCG parameters were not found (Fig. 2B).

DISCUSSION In this s t u d y sex-related ECG-VCG amplitude differences, with males having higher values than females, were found in 15- to 19-year-olds {Table I) j u s t as had been demonstrated in 11- to 14-yearolds in our previous study.' When age-sex matched teenagers were compared for determ!ning racial differences, black males had higher leftward, posterior and inferior ECG-VCG voltages than ~yhite males (Fig. 1A), while females did not show any race-related differences (Fig. 1B). Again, these data are similar to those observed in 11- to 14-yearTable II

Race Comparison of Biographic, Blood Pressure and Hemoglobin Data AGE/SEX GROUP VARIABLES

15-19 YEARS, MALES RACE

MEAN

_+SD

15-19 YEARS, FEMALES

p VALUE

MEAN

_+SD

p VALUE

Age (years)

B W

15.79 15.73

1.42 1.08

> 0.1

15.60 15.95

0.81 1.46

> 0.1

Weight (kg)

B W

62.58 62.25

12.02 13.58

> 0.1

64.62 18.62 55.37 5.18

> 0.1

Height (cm.)

B W

170.9 170.3

10.04 10.32

> 0.1

164.7 162.1

5.7 3.5

> 0.1

BSA (m 2)

B W

1.72 1.73

0.21 0.22

> 0.1 > 0.1

1.68 1.60

0.22 0.12

> 0.1

Chest Circ. (cm.)

B W

78.8 83.5

10.3 8.4

> 0.1

75.5 78.3

9.9 7.4

> 0.1

AP Diam. Chest (cm.)

B W

18.8 19.9

1.95 2.70

> 0.1

17.4 18.15

3.30 1.51

> 0.1

BP Systolic (mmHg)

B W

111.5 113.7

7.6 10.9

> 0.1

104.1 101.5

8.6 11.5

> 0.1

BP Diastolic (mmHg)

B W

76.5 73.2

6.6 9.6

> 0.1

67.0 69.8

11.2 10.4

> 0.1

Hemoglobin (gm%)

B W

12.68 13.68

0.71 0.85

< 0.01

11.51 12.74

0.8: 1.2

< 0.05

d. ELECTROCARDIOLOGY 18 (4)~ 1985

RACIAL DIFFERENCES IN ECG AND VCG

15-19 Years Males, Black vs. White 9 I B oE

._c

Block

D

Meon+SD p
15-19 Years Females, Black vs. White II

p(-0.O5

]

T

-I,o

7

9

p>O.I

7

=-

8

"~ c~

"~

~

0

~

0 LVIDd

ACW-MLV

9 B,ock

L [] w,,,o

8 [

9

4

] II [

"a .~

313

"

T

4/ ,o

|

9

.o.,

Meon+SD p>O.I

6

8 p>O.I

7

4

6

0

PWTd

"~

0 LVlDd

ACW-MLV

PWTd

qg. 2A and B. The left ventricular internal dimension in diastole (LVIDd), anterior chest wall (ACW) to mid-left venricular (MLV) distance and left ventricular posterior wall thickness in diastole (PWTd) are compared between 15-to 19-year)ld blacks and whites. There was no racial differences in LVIDd in either males (A) or females (B). The ACW-MLV distance vas shorter and left ventricular pWrRt was thicker (A) in black males than in white males (p<0.05) while there were no ;tatistically significant differences (p>0.1) between black and white females. here. T h e possible causes for racial voltage differences were also reviewed in t h a t s t u d y and will n o t b e reviewed here e x c e p t to s t a t e t h a t thicker LV p o s t e r i o r wall and s h o r t e r a n t e r i o r c h e s t wall to mid-LV distance in 15- to 19-year-old black male subjects, w h e n c o m p a r e d to t h e i r white counterp a r t s , a p p e a r to be responsible for the racial differences. T h e d a t a for this age g r o u p are similar to t h o s e o b s e r v e d in 6- to 10-year-olds and 11- to 14-year-old male s u b j e c t s ? B a s e d on this and the previous study, it is recomm e n d e d t h a t separate normal s t a n d a r d s be used for e v a l u a t i o n of E C G and VCG voltages in black and white children over six y e a r s of age. I t is also sugg e s t e d t h a t s e p a r a t e n o r m a l s t a n d a r d s are n e e d e d for males and females over 11 years of age.

J. ELECTROCARDIOLOGY 18 (4), 1985

REFERENCES t.

2.

3.

4.

RAO,P S, TnAPM~, M K ANDHARI; R J: Racial variations in electrocardiograms and vectoreardiograms between black and white children and their genesis. J Electrocardiol 17:239, 1984 REES,A H, RAO, P S, RIGBY,J J AND MILLER, M D: Echocardiographic estimation of left-to,right shunt in isolated ventricular septal defects. European J Cardiol 7:25, 1978 RAo, P S ANt) "hlAV,,at, M K: Influence of race and sex on echocardiographic measurements in children. J Cardiovasc Ultrasonography 3:75, 1984 Horrrou, J D, SImlmER, H S ANI) LAKATA, E G: Distance correlation for precordial electrocardiographic voltage in estimating left ventricular muscle mass: An echocardiographic study, Circulation 55:509, 1977