Download Rheumatic Heart Disease Epidemiology

Rheumatic Heart Disease Epidemiology
III. The San Luis Valley Prevalence Study
By WILLiAm E. MORTON, M.D., DR.P.H., ARnxum L. WAwqIEm,, M.D., M.P.H.,
JOHN V. WEIL, M.D., CARLETON L. SHMOCK, JR., M.D., JOSEPH SNYDER, M.D.,
AND JoHN A. LicHTY, M.D., M.P.H.
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SUMMARY
After epidemiologic data had suggested the existence of a high-risk rheumatic
fever (RF) region in Colorado, examination of 3,737 children in a careful prevalence
study in that region, the San Luis Valley yielded 14 cases of rheumatic heart
disease (RHD) for a prevalence rate of 3.7/1,000. This rate was significantly
higher than the rate of 1.7/1,000 among Denver children of the same age screened
by a similar method and followed for a similar period for ascertainment of diagnoses.
Although the current high RHD risk in the San Luis Valley had been thought
to be due to the relative impoverishment of this part of the state, the RHD and
history-of-RF prevalence rates did not correlate with socioeconomic indices by
county within the Valley as expected. An ethnic difference in RHD prevalence
seen in Denver did not exist in the San Luis Valley, which led to speculation about
(1) pattems of school attendance in small towns versus urban areas, and (2) the
probability that the influence of poverty as an RHD-risk factor operates on a
community rather than on a family or individual level.
Additional Indexing Words:
Rheumatic fever
Ethnic group inicidence
School children study
seemed to be associated with poorer socioeconomic circumstances than elsewhere in the
state in 1960. The mortality and morbidity
statistics which constituted the majority of the
data in that report were, by themselves,
insufficient evidence of the reality of this
apparent risk pattern, so that further proof
was needed that the RF incidence or the RHD
prevalence, or both were significantly higher
in the San Luis Valley than elsewhere in
Colorado. Because of the existence of a recent
accurate estimate of RHD prevalence among
Denver school children,2 3 it seemed that a
reasonable estimate of comparative RHD risk
could be obtained by a prevalence survey
using similar methodology among San Luis
Valley school children. We believed that RHD
prevalence data could probably be obtained
more quickly than incidence data for a disease
as rare as RF is becoming in this country.
Hopefully, the RHD prevalence study might
IN A PRECEDING paper' epidemiologic
data were reviewed which indicated that
in the San Luis Valley of south central
Colorado a higher risk of rheumatic fever
(RF) and rheumatic heart disease (RHD)
From the Department of Public Health and
Preventive Medicine, University of Oregon Medical
School, Portland, Oregon, and the Departments of
Preventive Medicine and Medicine, University of
Colorado Medical School, and the Colorado Department of Public Health, Denver, Colorado.
Supported by the Colorado Heart Association and
by the Chronic Disease Section of the Colorado
Department of Public Health and was conducted
during the senior author's tenure of the position of
research epidemiologist for the supporting institutions.
Address for reprints: William E. Morton, M.D.,
Department of Public Health and Preventive Medicine, University of Oregon Medical School, Portland,
Oregon 97201.
Received October 20, 1969; revision accepted for
publication January 7, 1970.
Circulation, Volume XLI, May 1970
Socioeconomic status
773
MORTON ET AL.
774
indicate whether the higher RF and RHD
risks, if substantiated, were uniform or localized within the region. This paper describes
the methods and results of that study in the
San Luis Valley.
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Methods
With the approval of the San Luis Valley
Medical Society and the county education
officials, arrangements were made to examine all
children in the fifth through the eighth grades in
all public and parochial schools in all six counties
in the San Luis Valley in January 1965. Extensive
preliminary community education about the study
and its purposes was conducted by the Colorado
Heart Association.
Since accurate heart disease prevalence estimates were the goals of the study, all students
were examined independently by two experienced
physicians to reduce the risk of overlooking cases.
Examinations consisted of precordial auscultation
on each student while in the erect and supine
positions plus palpation of the femoral pulses as
in previous studies.4 Although the Denver heart
disease prevalence study had included electrocardiographic screening in addition to the physician
screeners, funds and personnel were not available
for such an intensive effort in the San Luis Valley.
Based on previous experience, the omission of
electrocardiographic screening in this study
would be expected to lessen the observed
prevalence rate of congenital heart disease (e.g.,
10 of 80 CHD cases would have been missed in
the Denver study had electrocardiographic
screening been excluded) but to have little or no
effect on the observed RHD rate (e.g., none of
the 29 Denver RHD cases would have been
missed if screening by electrocardiograms had not
been used).
Students judged to have definite or suspected
heart disease by either primary examiner were
reexamined in February 1965 by cardiologists
who had, in addition, a 14 by 17-inch PA chest
roentgenogram and a 14-lead electrocardiogram
available. For a diagnosis of RHD to be
established at secondary screening or follow-up
examinations, a murmur was required to be of
grade II/VI or more loudness, to have typical
characteristics and radiation, not to be abolished
by respiratory or position changes, to be
accentuated by exercise, and to be agreed upon
by two or more observers. Although the initial
screeners were instructed to screen with a high
index of suspicion, final diagnoses were applied
by conservative standards, often after referral by
the family physician for further studies. Family
physicians were informed of the results of the
reexamination by letter and handled the diagnos-
tic and therapeutic referrals according to their
usual practices.
Individuals whose cardiac status remained
uncertain after the cardiologists' examinations
("possible heart disease" or "probably normal,
reexamine in 2 years") were usually told that
their hearts were probably normal and activities
need not be limited. Follow-up examinations 1T
to 2 years later usually resolved the doubt in favor
of normality, although in several instances,
progression of auscultatory and electrocardiographic signs resulted in additional diagnoses
which were not certain initially. Because these
additional cases which resulted from the followup procedure had been originally identified as
suspects in January 1965, they were regarded as
components of the prevalence rates based on the
original survey rather than as new cases manifested in the interval between survey and formal
follow-up. It is understood that prevalence rates
based on a survey which included persistent
follow-up procedures would almost always be
higher than rates based on the same survey
without follow-up or with only brief follow-up
procedures. Similar follow-up procedures were
used for previous prevalence estimates among
Denver parochial school children with which the
San Luis Valley results are compared.
Results
Of the 3,751 students enrolled in grades 5
through 8 at the time of the examinations,
3,737 (99.6%) were examined. Refusals were
commonest among older girls. According to
table 1, 50.8% of the students examined were
boys, and 52.7% belonged to the Hispano
ethnic group ("Spanish-American," usually
Spanish surnamed). Ethnic group age distributions in table 2 show that the Hispano
children tended to be slightly older than the
others in the same grades, a phenomenon
noted previously by Dodge and co-workers.5
Table 1
San Luis Valley, Grades 5-8, January 1965: Sex
and Ethnic Distributions of Students Examined
Total
Ethnic group
Male
Female
Hispano
Other white
Oriental
Negro
Total
973
996
835
913
11
2
1899
a
2
1838
No.
% of
total
1969
1748
16
4
3737
52.7
46.8
0.4
0.1
100.0
Circulation, Volume XLI, May 1970
RHEUMATIC HEART DISEASE EPIDEMIOLOGY
Table 2
San Luis Valley, Grades 5-8, January 1965: Age
and Ethnic Distributions of Students Examined
Age
(yr)
Hispano
Ethnic group
Other
white
white
Total
10 or less
11
12
13
14
15 or more
255
423
461
468
275
87
308
401
426
458
136
19
3
6
7
3
1
0
566
830
894
929
412
106
Total
1969
1748
20
3737
Non-
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Fourteen cases of definite RHD were
identified among the 3,737 students examined,
a prevalence rate of 3.7/1,000. Pertinent
characteristics of these 14 cases are listed in
table 3. Five of the 14 were known to the
current family physicians; four of the affected
children were on a regular prophylactic
penicillin regimen, and one had lapsed from
prophylaxis. One case (case 1793), in which
the sole apparent auscultatory valvular abnormality was mitral stenosis, is the only case
of this type encountered during a school
survey in the senior author's experience (three
previous surveys produced 45 cases of RHD
from screening of 25,749 children2' 6). None of
the 14 school children with RHD had had
cardiac catheterization or surgery as of June
1967. One (case 1923) had been seen at the
University of Colorado Medical Center where
our diagnosis was substantiated (U156416).
For those readers concerned with our
diagnostic standards, a description of several
of the borderline RHD cases which were not
counted in the prevalence rate will be
instructive. Table 4 lists seven individuals
whose borderline findings were insufficient to
qualify as chronic rheumatic heart disease in
this study.
L. C. (case 951) was a stolid, welldeveloped, asymptomatic youth with a history
of probable chorea and with two sisters who
had had clinical rheumatic fever. He lived in a
tiny mountain mining community about 40
miles from the nearest physician, and was one
of 17 children whose father had chronic
pulmonary disability. Rheumatic fever proCisrculasion, Volume XLI, May 1970
775
phylaxis was not being maintained for him or
his two sisters. No murmurs were heard on
careful auscultation at rest or after exercise.
Resting blood pressure was 124/48 in the right
arm, supine. The electrocardiogram showed
nodal premature beats, QRS voltage indicative
of left ventricular enlargement (Sv2 + Rv5 = 58
mm; RI, + RI,,= 55 mm), and sinus rhythm
(45/min) at rest. After exertion (20 fast situps) the sinus rate remained fixed at 45/min,
the ventricular rate speeded up to a regular
high-nodal rhythm at 75 beats/min, and no
premature beats were evident; the rhythm
reverted to the pre-exercise pattern after 4
min of rest. The boy denied any symptoms,
and his muscular development supported his
claim of vigorous participation in sports. The
clearly evident ECG abnormalities probably
reflect rheumatic cardiac damage which had
been present for some time, and a good argument could be entered for inclusion of this
individual among those with definite RHD.
E. R. (case 1533) was one of 11 children
whose father had died in an auto accident. At
the initial screening and reexamination in 1965
auscultatory signs were suggestive of aortic
valve deformity but were not sufficient to be
counted as a definite case of congenital heart
disease (past history and family history were
both negative for RF and RHD and there was
no evidence of existing RF). At follow-up
examination in November 1966 there was easy
fatigue, low-grade fever, BP of 104/34 mm Hg
in the left arm (previously 100/66), a grade
III/VI harsh systolic murmur at the right
upper sternal border, and a postexercise
aortic ejection click. After treatment by the
family physician, followed by maintenance of
daily penicillin prophylaxis, reexamination in
January 1967 disclosed disappearance of the
easy fatigability and fever and the aortic
ejection click. At this time BP was 120/66 mm
Hg, the systolic murmur was softer but still
distinctly abnormal, and the aortic component
of the second sound was inaudible. This
episode was interpreted as a relatively mild
acute attack of rheumatic fever with aortic
valvulitis superimposed on a probable congenital valvular deformity. Thirty years ago
776
MORTON ET AL.
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this case would have been counted as RHD
according to then-current diagnostic customs.
In the Colorado statewide sixth-grade survey
in 1949-51 this case would, quite probably,
have been counted as a case of rheumatic and
congenital heart disease. However, the pendulum of aortic valvular etiologic diagnosis
continues to move, and currently most U. S.
cardiologists would label this case as congenital heart disease as we did after considerable
discussion.
In case 1659, with no history of clinical
rheumatic fever or signs of valvular heart
disease, there was a strong family history of
rheumatic fever and an arrhythmia of uncertain duration. At rest the child manifested a
sinus pause every fifth or sixth beat followed
by nodal escape with succeeding beats gradually returning to sinus origin. The heart
sounds reflected the arrhythmia by corresponding cycles of split first sound and
prominent third sound. Exercise (12 vigorous
sit-ups) normalized the rhythm by auscultation and produced no other abnormalities.
There was no history of paroxysmal tachycardia or "palpitations."
D. R. (case 3756) had no history of clinical
rheumatic fever, but her father had had
rheumatic carditis in childhood. At the initial
examination in early 1965 and again in
December 1966 she had a prominent apical
midsystolic click. When the girl was erect, the
click was loudest at the apex and was
transmitted to the lower left sternal border,
the left infra-axillary area, and posteriorly to
the left lung base. The click was inconstant
when she was supine but it was unaffected by
C)
respiratory changes or by moderate exercise
C1)
(12 fast sit-ups). At the two initial 1965
examinations four observers agreed that no
murmurs were audible, but by December 1966
two observers could hear a grade II/VI, higha)
pitched, early systolic murmur at the apex and
UL several centimeters laterally in the erect
position only (normal first sound). One
c:
observer heard an inconstant, grade I/VI,
a)
Q~localized apical, mid-diastolic rumble in the
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MORTON ET AL.
Table 5
San Luis Valley, Grades 5-8, January 1965: Age Distribution of Rheumatic Heart
Disease and of a History of Past Acute Rheumatic Fever: Cases and Rates per 1,000
Examined
Age
(yr)
10 or less
11
12
13
14 or more
Total
Rheumatic heart disease
Prevalence rates
Cases
Crude
Smoothed*
2
1
3
8
0
1.2
3.4
8.6
0.0
2.1
2.6
4.5+
4.7
5.5+
14
3.7
3.9
3.5+
Past rheumatic fever
Prevalence rates
Cases
Crude
Smoothed*
20
23
26
35
17
35.3
27.7
29.1
37.7
32.8
30.8
30.1
31.7
33.3
35.9
121
32.4
32.2
*Rates smoothed by 3-level moving-mean method to compensate for spontaneous variations
due to small numbers of cases.
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Table 6
Ethnic Distributions of Rheumatic Heart Disease and of a History of Past Acute
Rheumatic Fever among Students in Grades 5-8 in the San Luis Valley and in Denver
Parochial Schools: Rates per 1,000 Examined
Location
and
ethnic group
San Luis Valley
Hispano
Other white
Nonwhite
Denver
Hispano
Other white
Nonwhite
Number
examined
3737
1969
Rheumatic
heart disease
Cases
Rates
14
7
7
0
1748
20
6470
11
1161
5108
202
less than pansystolic, and there was disagreement over the diastolic murmur, this girl was
not counted as having a definite case of
RHD.
Table 5 shows that the overall prevalence
rate of RHD was 3.7/1,000 examined, while a
history of past acute rheumatic fever was
found among 32.4/1,000 students. The latter
rate was based on 121 individuals who, after
careful review, had a reasonable history of
clinical rheumatic fever diagnosed by a
physician. We did not include 35 others for
whom the diagnosis had been made by a
nonmedical person, was probably misunderstood by the parent, or was probably mistaken. When the age-specific rates of RHD
and of a history of RF were smoothed
arithmetically to compensate for spontaneous
fluctuations due to small numbers,2 then the
3
8
0
Cases
3.7
3.6
4.0
0.0
121
1.7
83
2.6
1.6
0.0
Past history of
rheumatic fever
Rates
52
69
0
18
63
2
32.6
26.4
39.5
0.0
12.8
15.5+
12.3
9.9
tendencies of both to increase with age
became more clearly apparent.
To judge the frequencies of RHD and of a
history of RF among these San Luis Valley
children, we have compared these rates with
rates observed about 2 years earlier among
children of the same grade level in the Denver
parochial schools (table 6). The prevalence
rates of RHD and of a history of RF were
both more than twice as high among the San
Luis Valley children as among the Denver
children (P < 0.001 for both comparisons).
RHD prevalence did not differ significantly
between Hispanos and Anglos (other whites)
in the San Luis Valley (P > 0.25) or between
Denver and the San Luis Valley among
Hispanos (P > 0.05), but the RHD prevalence rate differed significantly between Hispanos and Anglos in Denver (P <0.005) and
Circulation, Volume XLI, May 1970
RHEUMATIC HEART DISEASE EPIDEMIOLOGY
779
Table 7
San Luis Valley Socioeconomic Indices from the 1960 U.S. Census*
1959 family income
Mean 1959
income of all
employed
persons
County
Less than
$10,000
or more
$3,000
(% of families) (% of families)
Alamosa
Rio Grande
Mineral
Saguache
Conejos
Costilla
$2,903
2,716
2,460
2,179
2,158
1,687
28.6
36.0
17.9
47.3
49.1
62.8
San Luis Valley
Colorado
$2,486
3,671
40.6
18.3
Education
Persons aged
Persons aged
14-17 yr
25 yr or more
(% in
(median school
school)
yr completed)
8.5+
8.3
0.0
8.9
5.2
2.3
7.1
14.6
Population
per
household
Ratio of
nonworkers
to
workers
89.8
85.7
t
83.5
86.8
71.7
11.3
10.6
11.4
8.9
8.7
7.6
3.41
3.59
2.73
3.60
4.15
4.19
1.75
1.94
t
1.94
2.61
3.69
84.8
89.4
9.9
11.7
3.70
3.21
2.23
1.60
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*Means and percentages computed from population-weighted county data. County data obtained from U.S.
Census of Population: 1960. Part 7. Colorado. U.S. Government Printing Office, 1962.
tData not available.
Table 8
San Luis Valley, Grades 5-8, January 1965: County Distribution* of Rheumatic Heart
Disease and of a History of Past Acute Rheumatic Fever; Cases and Rates per 1,000
Examtined
Rheumatic
No.
examined
County
Alamosa
Rio Grande
Mineral
Saguache
905
1,073
Conejos
Costilla
Total for
San Luis
Cases
Valley
31
421
910
397
2
1
0
4
7
0
3,737
14
heart disease
Rates
2.2
0.9
0.0
9.5+
7.7
0.0
3.8
History of
rheumatic fever
Cases
Rates
46
24
3
11
28
9
50.8
22.4
96.8
26.1
30.8
22.7
121
32.4
*Counties arranged in order from highest to lowest socioeconomic rank; see table 7.
between Denver and the San Luis Valley
among Anglos (P <0.001). All the foregoing
comparisons for prevalence of a history of
rheumatic fever were highly significant
(P < 0.005), although the reliability of a past
history of RF did not approach the reliability
of our identifications of RHD.
Since we postulated socioeconomic stress as
a major determinant of the San Luis Valley's
high RHD risk, it was only natural to inspect
the range of values of the socioeconomic
indices within the valley (table 7) before
considering the county-specific RHD prevalence rates. With the exception of Mineral
County, all of these counties ranked poorer
than the Colorado mean values in the percentCirculation, Volume XLI, May 1970
age of families with income less than $3,000/
year. Also, all the counties except Mineral
seemed to fit readily into a rough order from
least to most poverty-stricken (top to bottom
of table 7). Unfortunately, methodologic
limitations prevented the direct accumulation
of socioeconomic data for each examined
child.
When tabulated by county (table 8), the
RHD prevalence rate exceeds the Valley
average in Conejos and Saguache counties and
is lower than average in Alamosa, Costilla,
Mineral, and Rio Grande counties. The two
counties with high RHD prevalence rates are
not contiguous; Saguache County lies at the
northern end of the Valley, the Conejos
MORTON ET AL.
780
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County is one of two at the southern end. The
small numbers for each county make one wary
of sampling error. In surprising contrast, the
frequency of a history of RF was highest in
Mineral and Alamosa counties. The small
numbers in Mineral County allow one to
question the reliability of this rate, but
perhaps it is significant that the county seat of
Alamosa County is the largest town and
probably the commercial center of the San
Luis Valley. To compound the discrepancy
between prevalence rates of RHD and of a
history of RF, neither rate correlates directly
with the socioeconomic indices shown in
table 7.
Despite the significantly higher prevalence
rate of RHD in the San Luis Valley than in
Denver, the number of RHD cases was still
exceeded by the number of cases of congenital
cardiovascular malformations among the San
Luis Valley students: 26 cases or a prevalence
rate of 7.0/1,000 examined. These included
several cases of particular interest and will be
described in a future publication.
Discussion
As of 1963-67 the prevalence rate of RHD
in school children in grades 5 through 8 was
significantly higher in the San Luis Valley
than in Denver according to the results of two
extensive studies which employed similar
screening methods and similar periods of
follow-up for ascertainment of diagnoses. In
agreement, though less reliable, is the significantly higher frequency- of a history of RF
among children in the San Luis Valley than in
Denver. This geographic difference probably
did not exist in 1949-51, according to the
evidence gathered in a statewide survey of
sixth grade students," 5 and its duration in the
future is uncertain, possibly dependent upon
economic and sociocultural factors.
Although the data which led to this
investigation in the San Luis Valley had
strongly suggested that socioeconomic factors
were at fault, this study has revealed no
simple socioeconomic correlation within the
Valley. In Costilla County, the poorest in the
Valley by a noticeable margin (table 7), no
RHD cases were identified and the prevalence
rate for history of RF was below average.
The two counties with high RHD rates,
Conejos and Saguache, had average RF
history rates and slightly below-average mean
income values. The surprisingly high RF
history rate in Alamosa County, the "wealthiest" in the Valley, might be explained by (1)
more frequent visits to physicians and greater
chance of diagnosis of RF, or by (2) higher
RF incidence rate associated with more
frequent streptococcal transmission due to
higher rates of interpersonal contacts in
residents of the commercial center of the
Valley.
We have shown previously that in Denver
the socioeconomic distribution of the Hispanos was strongly skewed toward the lower
end of the scale in comparison to other whites
(Anglos).2 3 Although the more limited census data available from the San Luis Valley
did not permit an exact comparison, there was
no question but that a similar ethnic-socioeconomic contrast existed in the San Luis Valley
as well. A major social difference observable
in these two surveys was that in Denver most
of the impoverished Hispano children attended ghetto schools with others from similar
circumstances, whereas impoverished Hispanos in the San Luis Valley usually attended
the only school in town along with the
complete spectrum of other children. This
difference is presented as the probable reason
for the high RHD prevalence rate in both
Hispanos and Anglos in the San Luis Valley
and for the significantly higher RHD rate
among Hispanos than Anglos in Denver. This
phenomenon suggests that perhaps the influence of poverty on occurrence of RHD
operates on a community level rather than an
individual or family level. In a poor small
community (or in those poor small communities with high RHD risk) the risk may apply
fairly uniformly to all persons, no matter what
their individual levels of wealth may happen
to be. In cities large enough to have socially
"functional" ghettos, the high RHD risk may
be sequestered within the ghetto. This concept
Circulation, Volume XUL, May 1970
781
RHEUMATIC HEART DISEASE EPIDEMIOLOGY
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requires more specific data for firm acceptance.
This study's confirmation of the suspicions
raised by analysis of the routinely available
mortality and morbidity data indicate that, at
least in Colorado, more attention should be
paid to the routine statistics collected by the
state health department. It would follow, too,
that RF control programs based on exceedingly finite funds and personnel might be most
effective if applied in regions where the need
appears greatest. Further, routine attention to
data such as these would permit recognition of
non-effective control programs and measurement of the benefits of effective control
programs. Objective quantitative data are just
as valuable for the diagnosis and treatment of
health problems of the community as for the
diagnosis and treatment of health problems of
the individual.
Circulation, Volume XLI, May 1970
References
1. MORTON WE, LICHTY JA: Rheumatic heart disease epidemiology: II. Colorado's high-risk
low-socioeconomic region in 1960. Submitted
to Amer J Epidem
2. MORTON WE, HUHN LA, LICHTY JA: Rheumatic
heart disease epidemiology: I. Observations in
17,366 Denver school children. JAMA 199:
879, 1967
3. MORTON WE: Ethnic classification error in a
heart disease prevalence study among Denver
parochial students. Submitted to Public Health
Reports
MORTON
WE, HUHN LA: Heart disease detection
4.
in school children. Amer J Cardiol 16: 688,
1965
5. DODGE HJ, MARESH GJ, MoRRs NM: Prevalence
of heart disease in relation to some population
characteristics of Colorado school children.
Amer J Public Health 48: 62, 1958
6. MORTON W: Heart disease prevalence in two
Colorado communities. Amer J Public Health
52: 991, 1962
Rheumatic Heart Disease Epidemiology: III. The San Luis Valley Prevalence
Study
WILLIAM E. MORTON, ARTHUR L. WARNER, JOHN V. WEIL, CARLETON L.
SHMOCK, JR., JOSEPH SNYDER and JOHN A. LICHTY
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Circulation. 1970;41:773-781
doi: 10.1161/01.CIR.41.5.773
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Copyright © 1970 American Heart Association, Inc. All rights reserved.
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