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An Epidemiologic Study of First Degree
Atrioventricular Block in Tecumseh, Michigan*
Lawrence V . Perlman, iZ1.D.;O0 Leon D. Ostrander, Jr., M.D.;?
Jacob B. Keller. M.P.H.,$ and Beniamin N . Chiang, M.D.§
PR intervals of 0.22 sec or longer were detected in the electrocardiograms of
95 of 4,678 participants past 20 years of age in the Tecumseh Community
Health Study. The prevalence rates were similar in men and women and remained low through the sixth decade, but increased sharply in succeeding decades.
Nineteen of the 95 persons had some other manifestation of heart disease and
there was a significant association between delayed atrioventricular conduction
and angina pectoris or asymptomatic T wave inversion in participants past 60
years of age. Most of the cardiac abnormalities were found among older
individuals. Atrioventricular block was more constant on second examination
in this group and may have been due in part to sclerosis of the left side of the
cardiac skeleton, as well as specific etiologic types of heart disease. Among
younger and apparently healthy participants the PR interval usually shortened
on repeat examination, frequently to less than 0.22 sec. There was no excess
incidence of cardiovascular disease or mortality among the persons with long
PR intervals during a mean period of observation of four years. Delay in
atrioventricular conduction by itself appears to be a benign condition with no
unfavorable prognostic significance. It is probably a transient finding among
many members of the poputation.
irst degree atrioventricular heart block is defined
Faccording to the length of the PR interval in
those electrocardiograms in which all the normal
atrial impulses are conducted to the ventricles and
induce ventricular activation. The upper limit of the
"normal" PR interval is necessarily arbitrary, but the
most widely accepted criteria are based on intervals
of 0.20 to 0.22 sec. ' - 3
Digitalis and other medications can delay atrioventricular conduction, but most instances of first
'From the University of Michigan School of Public Health,
Ann Arbor.
This work was supported in part by the Cardiovascular
Research Center under Program Project Grant HE-09814
from the National Heart Institute, National Institutes of
Health, U.S. Public Health Service.
Presented a t the Conference on Cardiovascular Epidemiology, sponsored by the American Heart Association, National Heart Institute and Louisiana Heart Association, New
Orleans, March 3-4, 1869.
n'Forn~erly Instn~ctor in Internal Medicine, University of
Alichigan; currently Assistant Professor of hledicine, Marc l ~ ~ e tSchool
te
of Medicine, hlilwaukee.
tAssociate Professor of Internal Lledicine.
$Research Associate in Epidemiolog .
SInternational Postdoctoral ~ e s e a r c KFellow (USPHS No
3F05-01-A 1-S 1 ) .
degree block are not due to drugs.4-6
Atrioventricular block has been studied almost
exclusively in hospital or clinic patients or among
highly selected population samples. 7 - 1 4 Consequently it is recognized as a common finding in certain
specific conditions, but the relationship of the prolonged PR interval to the prevalence and incidence
of the common types of heart disease remains
obscure.
In order to study the prevalence and stability of
first degree atrioventricular block in a free living
' population and to determine any association
behveen delayed conduction and other evidence of
heart disease, the records of all participants in the
Tecumseh Community Health Study with a PR
interval of 0.22 sec or more were examined.
Tecumseh, Michigan is the site of a prospective epidemiologic study of chronic disease, particularly cardiovascular
disease, in a total natural community. Details of these investigations have been published previously.l"-'8
In 1959 and 1960 8,641 persons, 8 8 percent of the entire
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EPIDEMIOLOGIC STUDY OF THE FIRST DEGREE A-V BLOCK
population of the community, participated in the first series of
examinations. All participants gave detailed medical histories
and had thorough physical examinations which were performed by experienced members of the University of Michigan Medical School clinical teaching staff.
Standard 12 lead electrocardiograms, chest roentgenograms and serum cholesterol and blood glucose determinations were obtained from each person. During the first series
of examinations, 80 percent of the adult participants gave
blood specimens for glucose determination one hour after a
100 gm oral glucose challenge, and nearly all unchallenged
persons gave casual blood samples.
Response rates and procedures were similar in the second
series of examinations, which were performed from 1962 to
1965, except that nearly all participants ingested 100 gm
glucose.
During the first series of examinations, electrocardiograms
had been recorded without regard for the time of glucose
administration, but during the secorid series, all tracings were
recorded before glucose ingestion. In a population study of
this size it is not possible to control the intake of food or use
of tobacco before the examination.
Electrocardiograms recorded from persons past 16 years of
age were classified according to the Minnesota coding system.* Relative weights were calculated from the ratio of the
individual's observed weight to a predicted weight derived
from a sex specific equation which was based on height and
the biacromial and bicristal diameters.1Whest roentgenograms were interpreted by experienced radiologists and the
cardiothoracic ratio was calculated from direct measurements.
Myocardial infarction was diagnosed at the probable level
if the electrocardiogram revealed Q waves which fulfilled the
criteria for the 1-1 or 1-2 classifications of the Minnesota code
(exclusive of the I-2h category ). Primary T wave inversion
greater than 1 mm in leads I, 11, aVL, aVF or V2-Va
(Minnesota codes V-1 and V-2) was considered abnormal.
High amplitude R waves (code 111-1) and complete left
bundle branch block (code VII-1) were also considered
important electrocardiographic signs of disease.
Detailed histories of chest pain were elicited by means of a
standard questionnaire and subjected to strict criteria for the
diagnosis of probable angina pectoris.17 A diagnosis of hypertensive heart disease at the probable level required a systolic
blood pressure of 160 mmHg or a diastolic of 96 mmHg and
R wave amplitudes in the electrocardiogram that fulfilled the
criteria for the 111-1 category of the' Minnesota code. The
blood pressure criteria were not applied to persons receiving
antihypertensive drug treatment.
Table 1-Prevalence
The findings of the cardiac examination were recorded in
detail and a probable diagnosis of valvular heart disease
required a description of characteristic murmurs. Carefully
selected criteria were also applied to the diagnosis of other
clinical conditions such as diabetes mellitus, cerebrovascular
disease and chronic pulmonary disease.
High values for systolic or diastolic blood pressure, serum
cholesterol, relative weight and cardiothoracic ratio were
arbitrarily defined according to the upper quintile of the age
and sex specific distributions of these variables. The blood
glucose was treated similarly, except that the type of test,
casual or postchallenge, was taken into account in the calculation. The known diabetics were added to the upper quintile
of the distributions so that slightly more than 20 percent of
the participants were classified as hyperglycernic.
The interval between examinations varied from 20 to 72
months with a median interval of 47 months. Eighty percent
of the participants in both examinations were re-examined
between 40 and 56 months after their first examination.
Death certificates were obtained for all examined persons
who died, but autopsies were performed infrequently in the
community.
All electrocardiograms from the first series of examinations
in which the PR interval was recorded as 0.21 sec or longer
were reviewed by the three physician authors and the 95
persons whose PR intervals were measured as 0.22 sec or
longer by each reviewer constituted the study population.
The intervals were measured from the start of the P wave
to the first deflection of the QRS complex in leads I1 or 111.
The accepted interval was that which was the longest in the
lead with a clearly defined QRS complex of maximum duration, so that the prolongation of the PR interval was not an
artifact resulting from an isoelectric first portion of the QRS
complex. If the measurements were borderline, inconsistent
or indistinct, the tracing was excluded from the analysis. The
more markedly prolonged intervals were also lneasrlred conservatively, so that in no instance was the interval shorter
than stated.
Prevalence of atriouentriculur block (Table 1 )
First degree atrioventricular block was not detected among participants less than 20 years of age.
Prevalence rates were low among both men and
women during the third through sixth decades, but
rose progressively in the succeeding decades.
o f PR Intervals of 0.22 Second or Longer in Tecumseh Study Population, 1959-1960
20-29
Men
Number examined
Number with long PR interval
Rate per 1000
Women
Number examined
Number with long PR interval
Rate per 1000
Total
Number examined
Number with long PR interval
Rate per 1000
30-39
40-49
Age Groups
50-59
60-69
70-79
CHEST, VOL. 59, NO. 1, JANUARY 1971
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80+
Total
PERLMAN ET AL
Table 2--Comparative Prevalence o f Other Cardiac Abnormalities in Persons with Prolonged PR Intervals
and the Remainder o f the Tecumseh Population
20-39
Age
PR interval 2 0 . 2 2 second
Number in Population
40-59
60
+
With
Without
With
Without
With
31
2385
21
1578
43
1
32.3
5
2.1
0
0
18
11.4
6
139.5**
17
24.7
32
13.4
1
47.6
108
68.4
15
348.8**
121
195.2
Without
620
Number with MI
Rate per 1OOO
Number with AP
Rate per 1OOO
Number with HHD
Rate per 1OOO
Number with RHD
Rate per 1OOO
Number with T wave inversion
Rate per 1000
Number with LBBB
Rate per 1OOO
Number with any abnormality
Rate per 1OOO
3
96.8**
'
**P <0.01 (bssed on one tailed test)
tthis person also had angina pectoris
*P<0.05
MI = Myocardial infarction; AP
=
Angina pectoris; HHD = Hypertensive heart disease; RHD = Rheumatic heart disease;
LBBB = Left bundle branch block.
Relationship of atrioventriculur block to other manifestations of heart disease (Table 2)
Course of persons with first degree atrioventricular
block detected on first examination
Nineteen of the 95 persons with a prolonged PR
interval had some other evidence of heart disease.
Four had myocardial infarction, four angina pectoris, three hypertensive heart disease, one rheumatic heart disease ( mitral stenosis ) , seven asyrnptomatic T wave inversion (Minnesota code V-1, V2 ) and one left bundle branch block and angina
pectoris. T wave inversion and angina pectoris were
significantly more frequent among the persons past
60 years of age with atrioventricular block than
among the remainder of the Tecumseh population
of the like age. The proportion with any abnormality was also significantly greater than expected
among participants 20-39 years of age and those
past 60.
Repeat examination. Sixty-three persons with a
PR interval of 0.22 sec or lonser participated in the
second series of examinations. The PR interval in
the second electrocardiogram was the same or
longer for 17 persons and shorter for 46. Thirty-four
of the latter had PR intervals less than 0.22 sec at
the time of the second examination.
The PR interval shortened more frequently
among the 41 participants less than 60 years of age
(Table 4 ) . Those who had shorter PR intervals on
the second examination tended to have faster heart
rates in the second electrocardiogram than in the
first, although the relationship between changes in
Relationship of first degree atrioventricular heart
block to coronary heart disease risk factors (Table
3)
The prevalence of systolic and diastolic hypertension, high relative weight, hypercholesterolemia,
hyperglycemia and high cardiothoracic ratios among
participants with prolonged PR intervals did not
differ significantly from the prevalence of these
conditions in the total population.
Table S P r e v a l e n c e o f Coronary Heart Disease
Risk Factors among Tecumseh Participants with
Long PR Intervals
Systolic blood pressure
Diastolic blood pressure
Relative Weight
Cholesterol
Glucose
Cardiothoracic ratlo
No.
Determinations
No.
High
Values
95
95
92
91
91
84
19
16
24
19
20
16
Perrent
Elevated
20
17
26
21
22
19
CHEST, VOL. 59, NO. 1, JANUARY 1971
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43
EPIDEMIOLOGIC STUDY OF THE FIRST DEGREE A-V BLOCK
Table 4--Changes i n PR Interval at Second Examination According t o Age and Length o f Interval at t h e
T i m e of First Examination
20-39
Age Groups
Duration of P R interval
Numtxr
Number
Number
Number
Number
0.22-0.24
examined twice
with shorter P R
with P R less than 0.22
wit,h unchanged P R
with longer P R
0.25
21
16
13
3
2
+
4
4
3
0
0
the PR interval and the heart rate was not consistent ( Table 5 ) .
Persons whose PR intervals were the same or
longer on re-examination had a slightly higher
prevalence of other signs of heart disease but a
lower prevalence of coronary heart disease risk
factors than individuals whose PR intervals were
shorter ( Table 6 ) .
The duration of the PR interval on the first
examination was unrelated to the stability of the
abnormality. Six of the seven persons with intervals
longer than 0.25 sec when first examined had
shorter intervals at the time of reexamination and
three were less than 0.22 sec.
Of the six participants who were taking digitalis
at the time of the first examination, four had
intervals of 0.22 sec, one of 0.24 sec and one of 0.26
sec. Four of these persons were re-examined and the
interval was shorter in two and unchanged in two.
Two of the 63 persons examined twice had angina
pectoris and one had evidence of a myocardial
infarction at the time of first examination. Two of
the remaining 60 persons developed new cardiovascular disease during the mean interval of observation of four years. This incidence rate of 33 per 1000
was similar to the rate of 30 per 1000 for all
participants past 20 years of age in both examinations. A 76-year-old woman sustained an inferior
myocardial infarction and a 67-year-old man gave a
history of myocardial infarction without confirmatory electrocardiographic evidence.
40-59
0.22-0.24
15
14
12
1
0
0.25
+
1
1
0
0
0
60
+
0.22-0.24
0.25+
20
10
6
8
2
2
1
0
0
1
Mortality. Sixteen of the 95 persons with a
prolonged PR interval died during the interval
between examinations for a mortality rate of 168
per 1000 which was similar to the age adjusted rate
of 160 per 1000 for all other Tecumseh participants
during the same time period. Most of the deaths
occurred among older persons and those with other
evidence of heart disease. A higher proportion of
persons with PR intervals longer than 0.24 sec also
died (Table 7). Because longer intervals and heart
disease were more common among older participants, the relative contribution of these factors to
mortality cannot be ascertained (Table 8 ) .
The causes of death among the 16 fatalities who
had previously detected first degree atrioventricular
block were similar to the conditions responsible for
deaths in the general Tecumseh population of
similar age during the same period (Table 9 ) .
First degree atrioventricular heart block was not
observed in the electrocardiograms of any participants less than 20 years of age during the first series
of examinations in Tecumseh, Michigan. The prevalence of prolonged PR intervals was only 13 per
1,000 among the 4,015 persons from 20 through 59
years of age with no appreciable difference between
the sexes or from one decade to another. The
prevalence increased sharply in the succeeding decades, so that 43 of the 95 participants with delayed
Table M h a n g e s in PR Interval According t o Presence
Table 5--Changes in P R Interval at Second Examination
of Ocher Signs of Cardiac Diseare or Number
of Predisporing Conditions
According t o Changes in Heart Rate
Between the T w o Exantinations
PR interval at
second examination
Number of persons
Range of heart rate change
Mean change of heart rate
Median change of heart rate
Numher faster
Numtwr slower
Numt)cr unchanged
Shorter
Same or longer
46
-26 to 19
2/min
2/min
27
14
5
17
- 19 to 16
- 3/min
- 4/min
5
10
2
+
+
+
+
Changes in P R interval
Shortened
To
Same or
<0.22 longer
Total
Number of persons
Number with other cardiac
disease
Percent with other cardiac
disease
Number of risk factors
Risk factors per person
CHEST, VOL. 59, NO. 1, JANUARY 1971
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46
34
17
7
4
4
15
39
.85
12
33
.98
23
12
.71
PERLMAN ET AL
Table 7-Mortality Among Tecumseh Participants with
Prolonged PR Intervals According t o Age, Presence of
Other Direares and Duration o f PR Interval of 0.25 Sec
o r Longer During a Mean 4 Year Period o f Observation
Table &Relationship
o f Age t o Other Diseases
and PR Intervals o f 0.25 Sec or Longer
20-39
Age
20-39
40-59
60
Other diseases*
Present
Absent
PR interval
0.224.24
0.25
+
+
No.
persons
No.
died
Percent
No.
Percent
died survived survived
31
21
43
1
1
14
3
5
53
30
20
29
97
95
67
23
72
11
5
48
7
12
67
52
93
82
13
12
4
16
31
69
9
84
69
'Cardiac abnormalities as in Table 2 and diabetes mellitus
atrioventricular conduction were detected among
the 663 persons 60 years of age or older.
Among persons past 60 years of age with prolonged PR intervals, angina pectoris and asymptomatic T wave inversion were significantly more
frequent than expected but the majority of the
participants with first degree atrioventricular block
had no other evidence of heart disease. Among the
total of 95 persons with delayed atrioventricular
conduction there was no excess incidence of death
or new events of coronary heart disease.
Seventy-three percent of participants (46 of 63)
with delayed conduction at the time of the &st
examination who were re-examined had a shorter
PR interval on the second electrocardiogram and
Number of persons
Number with other diseases
Number with PR interval 20.25
31
3*
4*
.4ge Groups
10-59
60+
21
2
2
43
1st
7t
'one person had both
tfour persons had both
more than half had decreased to less than 0.22 sec.
The conduction delay remained the same or increased more often among older persons and those
with other signs of heart disease.
Shortening of the PR interval occurred more
frequently when the heart rate at the second
examination exceeded that at the first, and stable or
more marked delays in conduction tended to be
associated with slower heart rates, although there
were many exceptions to these trends.
Only six persons with a prolonged PR interval
were taking digitalis, which was not an important
factor in the variability of the atrioventricular conduction time.
Because some of the participants in the first series
of examinations ingested 100 gm of glucose before
the electrocardiogram was recorded, changes in test
conditions may have influenced the PR interval on
the second examination. The particular individuals
who received glucose before the electrocardiogram
was recorded could not be identified.
Table 9--Causer of Death and Previously Detected Abnormalities of Persons
with Prolonged PR Intervals on First Examination Electrmardiogrant
Antemortem
Conditions
Sex
Age
M
M
M
M
M
M
M
58
67
72
77
78
86
90
Took digitalis
F
F
F
37
63
66
AP
AP
Took digitalis
F
71
72
DM
F
F
76
F
F
F
77
86
90
ECG Findings
(Minn. Code)
Risk Factors
Cause of Death
G, CTR
lcl I
Accident
CHF
CV A
CVA
C V.A
hl I
MI
MI
AP
111-1, V-2
111-1, V-2
V-2
VII-2
V-2
V-2
V-2
VII-1
SBP, DBP, C
SBP, CTR
SBP
MI
SBP, DBP, RW
RW
G
hl I
CVA
SBP, DBP, RW, C
CA Gall Bladder
CV.4
CTR
CA IJrinary Bladder
SBP
CHF
CVh
Pneumonia
MI = myocardial infarction; AP = angina pectoris; DM = diabetes; CVA = stroke; C H F = congestive heart failure; SBP =
systolic hypertension; DBP = diastolic hypertension; RW = high relative weight; C = high cholesterol; G = high glucose;
CTR = high cardiothoracic ratio on x-ray; 111-1 = high amplitude R waves; V-2 = T wave inversion; VII-1 = complete left
bundle branch block; VII-2 = complete right bundle branch block.
CHEST, VOL. 59, NO. 1, JANUARY 1971
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EPIDEMIOLOGIC STUDY OF THE FIRST DEGREE A-V BLOCK
A review of data from an earlier study of the
effect of a 100 grn glucose challenge on the electrocardiograms of 53 men revealed no consistent
changes in the PR interval during two hours of
observation.20 Electrocardiograms were recorded in
the fasting state and at four successive 30-minute
intervals after glucose ingestion. The PR intervals of
most subjects remained the same and the few
changes observed were slight and inconsistent.
Among these 53 men, glucose ingestion did not
result in prolongation of a previously normal or
borderline interval to a duration greater than 0.22
sec in any instance. These findings suggest that prior
glucose ingestion at the time of the first electrocardiogram was probably not an important factor in
the variability of the PR interval between examinations.
Since the mean PR intervals increased with age in
the Tecumseh population, one might have anticipated fewer instances of shortening on re-examination. However, several other electrocardiographic
findings such as high amplitude R waves and
inverted T waves were as variable as the PR
interval among Tecumseh participants.21 Extremes
of physiologic measurements tend to regress toward
the mean on re-examination, and the PR interval
does not appear to be an e ~ c e p t i o n . ~ ~
The older individuals with long PR intervals
frequently had other evidence of heart disease
which could be implicated in their delayed conduction. Even those without specific abnormalities had
more persistent prolongation of the PR interval.
Lev23 has described a nonspecific fibrotic change in
the conductive tissues of the hearts of elderly
persons which he termed sclerosis of the left side of
the cardiac skeleton. This process may produce
atrioventricular or intraventricular block.
Only two elderly Tecumseh participants had both
complete bundle branch block and a prolonged PR
interval; both had angina pectoris and one died of a
myocardial infarction. Although coronary heart disease was the most obvious clinical disease in these
two persons, their conduction disturbances could
have been due to sclerosis of the cardiac skeleton.
This condition may account in part for the longer
mean PR intervals among the older members of the
Tecumseh population and the higher prevalence of
both delayed atrioventricular conduction and bundle branch block among participants past 60 years
of age.
Long PR intervals were significantly correlated
with several cardiac abnormalities, particularly in
persons past 60 years of age. On the other hand,
most of the Tecumseh participants with delayed
conduction had no evidence of heart disease and the
PR interval frequently was normal at the time of
reexamination. Much of what is arbitrarily defined
as first degree atrioventricular block is probably the
upper end of the normal distribution of PR interval
measurements. In otherwise healthy persons less
than 60 years of age, a prolonged PR interval
appears to be a benign and often transient finding.
ACKNOWLEDGMENT: The authors are grateful to Dr.
Frederick H. E stein, Director of the Tecumseh Community
Health Study, g r his helpful advice and suggestions, to Mr.
ohn Napier, Associate Director for Field Operations, for his
elp in assembling the data and to the entire staff for their
efforts in collecting the comprellensive information about the
study population.
i!
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apparently healthy people. Trans Assoc Life Ins Med Dir
Amer 36:44, 1952
2 Blackbum H, Keys A, Simonson E, et al: The electrocardiogram in population studies. A classification system.
Circulation 21 : 1160, 1960
3 Friedberg CK: Diseases of the Heart, (3rd ed ) Philadelphia, W. B. Saunders, 1966 pp 587-588
4 Lewis T, Drury AN, Iliescu CC: Some observations upon
atropine and strophanthin. Heart 9:21, 1921
5 Lewis T, Drury AN, Iliescu CC, et al: Observations
relating to the action of quinidine upon the dog's heart;
with special reference to its action on clinical fibrillation
of the auricles. Heart 9:55, 1921
6 Kayden HJ, Brodie BB, Steele JM: Procaine amide, a
review. Circulation 15: 118, 1957
7 Lown B, Aron W, Ganong W, et al: Adrenal steroids and
atrioventricular conduction. Amer Heart J 50:760, 1955
8 Soffer, A: Delayed conduction in dystrophica myotonia.
Dis Chest 40:594, 1961
9 Weed C, Bruce RA, Kurlander D, et al: Heart block in
ankylosing spondylitis. Arch Int Med 117:801, 1966
10 Graybiel A, McFarland RA, Gates DS, et al: Analysis of
the electrocardiograms obtained from 1,000 young aviators. Amer Heart J 27:524, 1944
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13 Yano K, Sawayema T, Johnson K, et al: Frequency and
prognosis of atrioventricular and intraventricular conduction disturbances in adult health study subjects of Hiroshima ABCC. Jap Circ J 31: 1665, 1967
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disease. Amer J Cardiol20:618, 1967
15 Francis T Jr: Aspects of the Tecumseh study. Pub Health
Rep 79:963, 1961
I 6 Napier JA: Field methods and response rates in the
Tecumseh Community Health Study. Amer J Pub Health
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17 Epstein FH, Ostrander LD Jr, Johnson BC, et al: Epidemiological studies of cardiovascular disease in a total
community-Tecumseh,
Michigan. Ann Intern Med
62:1170, 1965
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PERLMAN ET AL
total natural community, Tecumseh, Michigan. Circulation 31 :888, 1965
19 Montoye HJ, Kjelsberg MO, Epstein FH: The measurement of body fatness: a study in a total community. h e r
J Clin Nutr 16:417, 1965
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Reprint requests: Dr. L. Ostrander, University of Michigan,
130 South First Street, Ann Arbor 48104
The Lure of Discovery, Thrill of Danger and Hidden Hazards of
Arctic ~ x ~ l o r a t i o n
This gruesome but apocalyptic story begins on July 11,
1897. On this date, three Swedish explorers, Salomon
August AndrCe, an engineer; Nils Strindberg, a college
teacher; and Knut Fraenkel, a civil engineer, aiming at
making scientific observations and, if possible, to reach
the North Pole, took off in the car of the balloon, the
Eagle, from Danes Island, Spitzbergen. They were
obliged to land after a flight of 65 hours. Contact with
them was lost on July 13, 1897. They continued on foot
for months after landing on White Island. Their bodies
were found by the crew of a scientific expedition on this
island just north of the 80th parallel in 1930. Subsequently, there was much speculation about the ultimate
tragedy of these three explorers. Some assumed that they
fmze to death. Others thought that they died of starvation or of food poisoning from contaminated canned
goods. Also, the possibility of a fatal accident was advanced. Still others suggested that their death was due
to suffocation resulting from air-tight sealing of their tent
by heavy snow. On close scrutiny, however, all of these
assumptions were adjudged untenable. A fairly reasonable supposition was the possibility of carbon monoxide
poisoning originating from their primus stove. But at the
time their bodies were discovered, the tent was worn and
tattered and there was a pint and a half of paraffin in
their stove, indicating that the stove had been turned off.
The following pertinent details in the book by Sundman
seem to be convincing (The Flight of the Eagle, New
York, Pantheon Books, 1970). "In 1952, a Danish doctor, E. A. Tryde, published a book on the AndrCe expedition. Trvde had read AndrCe's diarv and had taken notes
of all the conscious or unconscious references to the
symptoms of an illness from which the three men had
suffered. He discovered that quite early on their journey
across the ice they had suffered from fever, cramps,
diarrhea, stomach pains, muscular pains, rashes and
small boils. These symptoms pointed toward the likelihood that their illness was trichinosis which they contracted by eating infected bear meat. In the AndrCe
Museum at c r a n i a , Sweden, Tryde discovered remnants
of two polar bears shot during the explorer's journey
across the ice. Microscopic examination revealed that
both bears had been infected with trichinae. According
to additional notations in Andrk's diary, the three explorers had eaten at least 20 meals from these bears.
There was good reason to believe that some of the bears
they had shot earlier were also infected." Moreover,
Andrke and his companions consumed bear's liver as a
delicacy, being unaware of the severe toxic effect of
excessive amounts of vitamin A contained in the liver of
polar bears and not knowing that Eskimos habitually
abstain from eating bear's liver. There has been a salutary, steep decline in the prevalence of trichinosis in the
United States during recent years. Even so, the estimated figures given by Most (JAMA 193:871, 1965) are
quite startling. In trichinosis, inflammatory changes are
brought about by the larval worms (Trichinella spiralis)
at diverse anatomic sites. with encvstation in several of
the striated muscles (diaphragm, intercostals, pectoral,
deltoid, biceps, gastrocnemius etc) . Encysted larvae may
remain alive-in the muscle for a year. s;mptoms includk
periorbital edema, pronounced myalgia, fatigue, precordial pain, tachycardia, hypotension, diarrhea, fever
which may reach 105.8"F. Subungual splinter hemorrhages may be observed. Myocarditis may be a grave
complication. Neurologic involvement may result in
headache, blurred vision, photophobia, tinnitus, convulsions, delirium, coma, spastic paralysis, monoplegia, hemiplegia and polyneuritis. Dyspnea may be due to involvement of the thoracic muscles, the diaphragm, pulmonary
congestion and pulmonary parenchymal infiltration.
Blood eosinophilia and muscle biopsy are of importance
in diagnosis. Specific skin test (detectable in 15-20 minutes) may not be positive until after the third week of
illness. Serologic tests are often negative during the early
phase of the disease. Bentonite flocculation test and
complement fixation test are likely to be positive in 8 0 to
90 percent during the fourth or fifth week of the disease.
The new broad spectrum anthelmintic, thiabendazole
(Mintezol, Merck, Sharp & Dohrne) has been found to
be of high therapeutic value.
Andrew L. Banyai, M.D.
CHEST, VOL. 59, NO. 1, JANUARY 1971
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