Download Postural Variation in Second Sound Splitting

Postural Variation in Second Sound Splitting*
I. C. MacKenzie;** M. E. Rosenberg;** G. Kroll, M.D.;? and
M. Brandfonbrener, M.D.;
Pbonocardiograms were obtained of 30 normal men in the supine and sitting
positions. They demonstrated significantly greater S2 splitting and respiratory
variation in S2 in the sitting position. However, several individuals showed wider
splitting or greater variation while supine. Fixed splitting occurred in three
subjects while supine and five others while sitting, but in no normal subject was
splitting fixed in both positions.
1866, Potainl first described the normal inI ncrease
in splitting of the second heart sound
with inspiration. Unlike the first heart sound, which
is composed of several components which do not
correspond well temporally, to valve closure, the
second sound has been well documented to be
For editorial comment, see page 4
produced by both aortic and pulmonic closures.
Boyer and C h i ~ h o l m Aygen
,~
and B r a ~ n w a l d and
,~
Castle and Jones4 found that both aortic and
pulmonic closures vary with respiration. From 12
percent to 50 percent of the variation in splitting is
accounted for by change of the Q-A2 interval.
Splitting of the second heart sound has been
found to vary in certain states. Shah and Slodki5
found that advancing age brought a gradual decrease in second sound splitting, and that hypertension correlated with a prolonged Q-At interval and
reduced splitting. Right bundle branch block causes
wide ~ p l i t t i n g ,but
~ respiratory variation is usually
preserved. DePasquale and associates7 found that
right ventricular failure was associated with fixed
wide splitting and left-sided failure with reduced or
paradoxic splitting. A patient with biventricular
failure may demonstrate normal splitting with slight
or paradoxic respiratory variation.
Tests of cardiac function have been devised that
utilize observation of the splitting of the second
heart sound. Cobbs and co-workerss found that
pulmonary embolism produced a wide fixed split,
the degree of splitting increasing with the severity
*From the Veterans Administration Research Hospital and
Northwestern University hledical School, Chicago.
"Medical student.
+Assistant Professor of Medicine.
$Professor of Medicine.
Reprint requests: Dr. Brandfonbrener, 303 East Chicago Aoenue, Chicago 60611
of embolism. Differences in the respiratory variation
of the Q-A2 and Q-P2 intervals may help differentiate chronic constrictive pericarditis from African
cardiomy~pathy.~
In constrictive pericarditis there
is inspiratory shortening of Q-A2 interval which
causes inspiratory splitting, with a fixed Q-P2. In
biventricular failure due to cardiomyopathy, Q-Aa is
fixed while Q-P2 is either fixed or moves very little.
Auscultation of the second heart sound is especially
helpful in the diagnosis of congenital heart disease.
It remains an important clinical means of differentiating the Eisenmenger form of atrial septa1
defect ( ASD ), from other causes of Eisenmenger's
syndrome.1° In the former the splitting is more
likely to be fixed. Both ASD and VSD cause wide
splitting in proportion to the shunted blood flow7
but relatively fixed splitting occurs in ASD. Relatively Exed widely split S2 is a helpful sign when a
significant shunt exists in children over five years of
age. In ASD fixed splitting is associated with
simultaneous delay in aortic and pulmonic closure.
Breen and Rekatel1 pointed out that a child
suspected of ASD must be auscultated in the sitting
position as some normal children have fixed wide
splitting in the supine position. Castle and associates12 also found that some children have fixed
narrow splitting in the sitting position. Final cardiac
evaluation must therefore be done supine, immediately after sitting and after sitting several minutes.
A few studies have been done concerning the
effect of posture on second sound splitting. ASD
shows wide splitting in the supine and sitting
positions. Standing has been found to decrease the
wide splitting associated with pulmonary embolus.'
Castle studied 116 children with respect to the
effects of posture, heart rate, sex, age, height and
weight on second sound splitting and found wider
CHEST, VOL. 63, NO. 1, JANUARY, 1973
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POSTURAL VARIATION IN SECOND SOUND SPLITTING
splitting and greater respiratory variation in the
sitting versus supine position. After sitting five
minutes, girls showed 7 msec wider splitting. No
other variable significantly affected splitting.
There have been no adequate studies showing the
effect of posture on splitting of the second heart
sound in adults. One study showed greater respiratory variation in splitting in the supine position13
than sitting, but most subjects in this study showed
relatively fixed splitting, ie respiratory variation of
less than 10 msec. This study investigated the effects of posture on second sound splitting in a
population of normal men.
Phonocardiograms were obtained from 33 men, between
22 and 25 years of age. Each had a normal cardiorespiratory
system by history and clinical examination. No attempt was
made to correlate age, height, weight, pulse, blood pressure
or respiratory rate with splitting because of the fairly narrow
distribution of these variables in these subiects.
,
, and because
of previous studies showing slight or no differences produced
by these factors.12-1.1
A Sanborn 4-channel photographic recorder was used to
record responses from a Bowles high frequency chest microphone. Recordings were made at 75 or 100 mm per second.
Respiratory motion was recorded from a pressure sensitive
tambour attached to a blood pressure cuff around the subject's chest. Lead 2 of the ECG was simultaneously recorded.
Each subiect rested several minutes in the s u ~ i n ewsition.
A phonocardiogram, as described above, was then recorded
from the second left intercostal space. The subject then sat
up and a second recording was taken after sitting 30 seconds.
A final recording was made after sitting five minutes. Three
to five normal respiratory cycles were included in each
recording and the average maximum and minimum splitting
was obtained. Three of the original 33 recordings were
discarded because of interference.
Table l-Average Splitting Intervalr i n Supine and
Sitting Position. (30 S u b j w u ) .
Position
Respiratory
Phase*
Average
Difference Standard
AGPC*' Deviation
(msec)
(msec)
Supine
Inspiratorg
Expiratory
Average variation
11.8
24.8
17.0
11.5
7.5
8.1
Sitting
30 seconds
Inspiratory
Expiratory
Average variation
47.4
21.5
25.9
13.0
7.8
10.8
Sitting
5 minutes
Inspiratory
Expiratory
Average variation
48.2
21.2
24.0
13.6
9.4
10.5
'Average of values for 3 to 5 respiratory cycles.
'AC =Aortic closure.
PC = Pulmonic closure.
variation in the sitting positions, although five had
most variation while supine. Three of 30 showed
fixed splitting (defined as respiratory variation less
than 10 rnsec) while supine, and five others showed
this after sitting five minutes. All of the subjects
demonstrating "fixed splitting in some position
showed respiratory variation greater than 12 msec
in one of the other positions.
. .
Table 1 summarizes the average splitting intervals found in inspiration and expiration in each of
these body positions. In the supine position, inspiratory splitting was 41.8 msec, standard deviation
k 11.5, after sitting 30 seconds 47.4 msec +13.0, and
after sitting five minutes 48.2 msec k13.6. Average
expiratory splitting in the three positions was 24.8
msec k7.5; 21.5 msec 27.8; and 24.2 msec k 9 . 4
respectively. Splitting of S2 in the sitting position in
inspiration is statistically significantly greater than
that in the supine position (P<.01). Also, the respiratory variation in splitting is significantly greater in the sitting position than in the supine
(P<.Ol).
Subjects demonstrated variations in patterns of
splitting. Seventeen of 30 had wide splitting in
upright postures after both 30 seconds and five
minutes, but three of 30 had widest splitting while
supine. Twenty-one of 30 had greater respiratory
The results of this study agree with the analysis
of respiratory variation of S2 splitting by Castle and
co-workers.12 One other publication concerning
postural variation in adults showed contradictory
results.13 Castle's study gave results similar to those
reported here, for postural variation in children: 21
to 38 msec supine, 21 to 45 msec sitting 30 seconds,
and 24 to 48 msec sitting five minutes. This suggests
that the same factors causing respiratory variation
in children occur in young adults. It is also apparent
that a significant fraction of normal adults, as well
as children, have fixed splitting in either supine or
sitting positions.
A well-known mechanism of respiratory variation
in second sound splitting has been proposed from
animal and human experiments. Inspiration causes
decreased intrathoracic pressure, increased right
ventricle filling and prolonged Q-P2. Pulmonary
vascular capacity increases and left ventricular
filling decreases, causing a shorter Q-A2. During
expiration, the above sequence is reversed, causing
longer Q-Az, shorter Q-P2 and decreased splitting.
Other factors such as the differential pressures
between the abdominal and thoracic cavities are
less easy to quantitate but are probably quite
significant.
Besides different respiratory muscle action in
CHEST, VOL. 63, NO. 1, JANUARY, 1973
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MAC KENZIE ET AL
different b o d y positions, another mechanism m a y
c a u s e m o r e variation i n splitting f o u n d in t h e sitting
position. T h e m e a n central venous pressure (CVP)
is less in t h e sitting position t h a n s u p i n e and the
c a r d i a c o u t p u t l o ~ e r . ' ~ >Rl i~g h t h e a r t o u t p u t
( R O ) affects t h e Q-P2 interval. The plot of RO vs
CVP on the Starling c u r v e is steeper a t lower filling
pressures. Inspiratory a n d expiratory m o v e m e n t s
causing t h e s a m e variation in CVP in the sitting
position should c a u s e slightly g r e a t e r respiratory
variation i n right-sided output in this position. T h i s
should c a u s e greater variation i n t h e Q-P2 interval
a n d second s o u n d splitting in t h e sitting position.
The clinical implications of this s t u d y a r e t h a t if
o n e encounters difficulty i n appreciating splitting of
S2 w h e n t h e patient is supine, t h e n auscultation
s h o u l d also be p e r f o r m e d w h e n the p a t i e n t is
sitting. Exploring different areas a l o n g t h e LSB
w i t h t h e stethoscope d i a p h r a g m is, of course, also
helpful. If fixed or relatively fixed splitting is h e a r d
either sitting o r lying, auscultation in t h e other
position m a y clarify whether o r not the splitting is
really fixed.
1 Potain PC: Note sur les dedonblements nonnaux des
bruits du coeur. Bull Soc Med Hop Paris (Series 2 ) 3: 138168, 1866
2 Boyer SH, Chisholm AW: Physiologic splitting of the
second heart sound. Circulation 18: 1010-1011, 1958
3 Aygen MM, Braunwald E : Splitting of the second heart
sound in normal subjects and in patients with congenital
heart disease. Circulation 25:328-345, 1962
4 Castle RF, Jones KL: The mechanism of respiratory
variation in splitting of the second heart sound. Circulation 24: 180-184, 1961
5 Shah PM, Slodki hlD: The Q-11 interval. Circulation
29:551-561, 1964
6 Leatham A: The second heart sound, key to auscultation.
Acta Cardiol 19:395-416, 1964
7 DePasquale NP, Burch GE, Phillips JH: The second
heart sound. Am Heart J 76:419-431, 1968
8 Cobbs BW, Logue RB, Dorney ER: The second heart
sound in pulmonary embolism and pulmonary hypertension. Am Heart J 71:843-844, 1966
9 Reid JV: The second heart sound in biventricr~larfailure
due to African cardiomyopathy. An1 Heart J 68:38-40,
1964
10 Wood P: The Eisenmenger syndrome or pulnionary hypertension with reversed central shunt. Br \led J 2:701709,1958
11 Breen WJ, Rekate AC: Effect of posture on splitting of
the semnd heart sound. JAhIA 173: 1326-1328, 1960
12 Castle RF, Hedden CA, Davis NP: Variables affecting
splitting of the second heart sound in normal children.
Pediatrics 43: 183-191, 1969
13 Jacono A, Bnonanno C, Perna N: Le modificazioni del
secondo tono cardiaco indotte daile variazioni posturali.
Minerva Cardioangiol 13:653-657, 1965
14 Harris A, Sutton G: Second heart sound in normal subjects. Br Heart J 30:739-742, 1968
15 Naimark KA, Wasserman K: The effect of posture on
pulmonary capillary flow in man. J Clin Invest 41:949954, 1962
16 Mchlichael J, Sharpey-Shafer EP: Cardiac output in man
by a direct Fick method. Br Heart J 6:33-40, 1944
Apropos of Productivity
The Latin name of t h e mason-bees, Chalicodoma,
means pebble-house. All these bees build their nests
of calcareous clay mixed with sand and saliva; this sets
the form of a hard mortar. T h e nests are rounded objects. Their outer surfaces are left rough like rustic
architecture. Several bees may build close together so
that their combined nests form a sort of comb and there
may be cooperation between a number of bees putting
a final coat of mortar around the finished structure. T h e
inner walls of the nests are always smooth. They are
filled with honey, sainfoin and broom flowers being
favorite sources. Fabre calculated that collecting mud
to build a cell and journeying to a sainfoin for honey
involved journeying for 9%miles to complete and store
one cell. T o provision all the cells and put on the final
cover would mean flying for 275 miles.
Andrews C: T h e Lives of Wasps and Bees,
New York, American Elsevier, 1969
CHEST, VOL. 63, NO. 1, JANUARY, 1973
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