The use of echocardiography to measure isometric contraction time

The use of echocardiography isometric contraction time

to measure

Gala1 M. Ziady, M.D.* Tod Hardarson, Ph.D. Roberto Curiel, M.D. London, England

An important approach to the quantification of the contractile state of the left ventricle has been the study of the rate at which intraventricular pressure rises, or the first derivative of ventricular pressure, dp/dt. As the main determinant of the duration of the isometric contraction time is the peak dp/dtl, hence the importance of estimating this time accurately. None of the current methods available for estimating the isometric contraction time is satisfactory. In this paper, we discuss some of the currently available techniques and suggest an alternative method of estimating the isometric contraction time using echocardiography. Methods

Twenty-five subjects were studied. Fifteen patients with primary myocardial disorders, and ischemic heart disease, and 10 normal subjects. The normal subjects were volunteers from the staff of the hospital. None of them had symptoms or signs of heart disease, and their chest radiograph and electrocardiograms (ECG’s) were normal. Five were males and five were females. Their ages ranged between 21 and 52 years with a mean of 30.7 years. Five patients had hypertrophic cardiomyopathy. Their ages ranged from 15 to 52 years. Six patients had congestive cardiomyopathy, their ages ranged from 22 to 51 years. Four patients had ischemic heart disease From the Cardiovascular graduate Medical School, gland. Supported Received Reprint Street,

in part

by a grant

for publication

April

from

Cardiac

the British

Cardiology), Hospital, Heart

Royal London,

PostEn-

Foundation.

10, 1974.

requests: Dr. G. M. Ziady, Agouza, Cairo, Egypt.

*Present address: tals, Cairo, Egypt.

200

Division (Clinical and Hammersmith

Department,

32 Abou Ein

El Mahaseen Shams

University

El Shazly Hospi-

aged 38 to 67 years. All the patients had cardiac catheterization and left ventricular angiography. Coronary arteriography was performed in the group of patients with congestive cardiomyopathy and ischemic heart disease. All the patients had a simultaneous recording of the external carotid pulse, phonocardiogram, an electrocardiographic lead, and a mitral echogram. For the recording, a B-channel Cambridge Scientific Instruments (Type 72112) machine was employed. The position of the phonomicrophone (suction microphone, Type 72352) was chosen so as to display clearly the first high-frequency vibrations of the first heart sound (MI), and the aortic component of the second heart sound. The filter band was f 3 dB. from 25 Hz. to 1 KHz. (manufacturers specifications). The carotid pulse was recorded over the right carotid artery, using a funnel connected by polyethylene tubing to a piezo-electric transducer connected to a pulse amplifier (Cambridge, Type 72354) with a frequency response of + 3 dB. 0.1 Hz. to 100 Hz. and a time constant 1.6 second. An external ECG lead was chosen which showed clearly the onset of ventricular depolarization as a reference lead. The mitral echogram was recorded using an Ultrasonoscope (Smith and Kline Eskoline 20) connected to the Cambridge machine. The photographic paper speed was set at 100 mm. per second. From the recordings, three intervals were measured. First, the external isometric contraction time, calculated as the interval from the first high-frequency vibrations of the first heart sound, to the aortic component of the second heart sound less left ventricular ejection time. Second, the pre-ejection period, calculated as the interval from the beginning of the QRS complex of the ECG to the aortic closure sound, less left

February,

1975, Vol. 89, No. 2, pp. 200-206

~e~tri~~~ar ejection time. Third, the isometric contraction time .as determined by echocardiography, calculated as the interval from the onset of systolic closure of the mitral valve (the R-point) to aortic closure sound less left ventricular ejection time (the ultrasonically derived isometric contraction time) (Fig. 1). The internal isometric contraction time was measured during cardiac catheterization from the left ventricular, the aortic pressure curves, and the ECG in 11 patients using a saline-filled manometer. In three patients, the mitral echogram and the phonocardiogram were recorded simultaneously with the left ventricular pressure curves using a high-fidelity catheter tip manometer Statham SIW. The internal isometric contraction time calculated as the interval from the onset of rise of left ventricular pressure to the point when aortic diastolic pressure is reached.2 All the intervals were measured to the nearest 5 msec. At least five cardiac cycles were used in the calculations, during which the patient was breathing normally. The intervals were corrected for heart rate, using the indices of eissler, Harris, and Sehoenfeld.3 All the patients were well stabilized on their respective therapy and no changes in drug treatment were carried out until the time of cardiac catheterization which was performed one to three days subn ICL 4100 computer was employed for the statistical least-squares correlation of invasive and noninvasive data. One-tail tests of significance were used. Student’s t-test was performed with two-tail tests of significance.

The results from the ten normal subjects are shown in Table I. The results from the patients group are shown in Table II. The isometric contraction time as measured by the ultrasound method showed an excellent correlation with the y recorded isometric contraction time , P ( 0.01) @‘ig. 2). The external isometric on time correlated at only the 50 per cent level with the internal isometric contraction time and was significantly shorter than the internal isometric contraction time (P < 0.01). The i e contraction time as determined by ultr method discriminated well between the normal group and the group of patients (P ( 0.011, while with the external iso-

American

Fig. I. A schematic illustration of the .~ethods used ts measure the isometric contracticcr, time edernally. Cl, carotid incisura; Cp, exteraai carotid puke tracing; Cu, carotid upstroke; ECG, electrocardiogram: @ICT, externai isometric contraction time; LYEF, Ieft ~~~t~~c~ar ejection time; PCG, phonocardiogram; PEP, pre-erection period, UCG, ultrasound of the mitral valve; and ITICT, ultrasound :sometric contraction time.

T I. measurements of ~xt~r~~~ isometric zraction time, pre-ejection ~~Itraso~i~aII~ isometric contra.ctio al subjects

Mean SD. S.E.M. All

values

43.9 10.6 3.4

32.8 11.9 3.7

.59.3 X1.6 3.7

in milliseconds.

ETCT = external PEP = pre-ejection

isonetric

contracticn

period. 3.D. = standard deviation. S.E.M. = sianderd error of the UICT = ultrasonically measured

mean. isometric

time.

rontraetim

con-

tine.

Ziady, Hardarson,

and Curie1

60 L5

50 40

20

CORRELATION

10

COEFFICIENT R = 0.92 PC 0.01

0 0

10

20

30

40

50

60

70

60

90

100

IICT

Fig. 2. The least-square relationship between the ultrasonically and the internally determined one (IICTL The measurements

determined are recorded

isometric contraction in milliseconds.

time

WICT),

Table II. Measurements of internal isometric contraction time, ultrasound isometric contraction external isometric contraction time, and pre-ejection period in patients group. NO.

Diagizosis

KZCT

UZCT

EZCT

PEP

1 2 3 4 5 Mean

HOCM HOCM HOCM HOCM HOCM

53 40 22 52 41.7

68 42 27 52 41 46.0

53 28 16 42 31 34.0

104 96 60 122 81 92.6

6 7 8 9 10 11 Mean

COCM COCM COCM COCM COCM COCM

96 75 64 -

92 86 IS 79 95 96 87.8

54 72 41 43 76 81 61.2

113 156 123 115 154 145 137.7

12 13 14 15 Mean

IHD IHD IHD IHD

80 56 59 72 66.7

61 31 49 52 48.2

120 94 100 127 110.2

84 79.7

62 46 78 62.0

time,

All values in milliseconds. COCM = congestive cardiomyopathy. ETCT = external isometric contraction time. HOCM = hypertrophic obstructive cardiomyopathy.

IHD = ischemic heart disease. PEP = pre-ejection period IICT = internally determined UICT = ultrasound determined

metric contraction time the results were not significant. The pre-ejection period also showed significant difference between the normal and the patients values (P ( 0.001) (Fig. 3). Taking all the subjects as one group, the external isometric contraction time was found to be significantly shorter than the ultrasound measured isometric contraction time (P (0.001) and also shorter

than the internal isometric contraction time (P ( 0.01). The simultaneous recording of the mitral echogram and the left ventricular pressure curves using a catheter-tip manometer showed that the B-point of the mitral echogram coincides exactly with the onset of left ventricular contraction (Fig. 4).

202

isometric isometric

February,

contraction contraction

time. time.

1975, Vol. 89, No. 2

-; ._----. _-- PEP

EiC

The isometric contraction time is the interval from the onset of left ventricular contraction to the opening of the aortic valve.4 The main determinant of the duration of the isometric contraction time is the rate of rise of pressure within the left ventricle (dp/dt).1,5 Other factors include the astolic pressure of the left ventricle and the a.ortic diastolic pressure. Various methods have been suggested to measure the duration of the isometric contraction time. Having access to rect pressure tracings, isometric contraction e can be calculated from .the point when the left ventricular pressure starts to rise, to the point when the aortic diastolic pressure is reached. Braunwald, Fishman, and Cournand6 have reported average values for the isometric contraction time in patients without cardiac disability, recorded directly during thoracotomy. For an isometric contraction time starting with the onset of left ventricular pressure rise, their average value was 61 zk 12.1 msec., the average me-ejection period was 115 _t 11.7 and the &onset of left ventricular systole 52 2~ 6.7 msec. These values are useful for comparison with inirect methods, although techniques using the nset of subendocardial and papillary muscle co~tractiou as a starting point for the isometric contraction time would tend to give higher values7 Apart from certain technical and physections to the direct method, it cannot be repeated serially, hence the need for easily derived, repeatable noninvasive methods unaccompassed by procedural hazards to the patients. The mitral component of the first heart sound has been taken to represent the onset of isometric contraction. Several objections have been raised to the use of this method. It is doubtful whether the first high-frequency vibraof the first heart sound represent in actual the mitral valve closure.s,Q Mitral valve re is not completed until left ventricular contraction has already started. From the techical point of view, the mitral component of the rst heart sound may be difficult, or impossible, to identify with certainty. Furthermore, the first high”frequency vibrations of the first heart sound bear no constant relationship to the onset of left ventricular isometric contraction.lOThe 1 value in the present study, howagreement with those reported by other w~r~er~.2,11

msec

Patients -

160

Patients

Patients ---

/--

Fig.

3.

A

comparison

Of

the

duflition

:C

determined isomef;rie externa! isometric contra&m time period (PEP) in normal subjects an6 tive car~iom~o~at~~ HXXXvf), and ;IHD).

dtrasonicalty

Ri!lliSKOildS

of

the

coatrartiam time f@XTl, ad prein patients with kchemic heart

he pre-ejection period cornpn”n~+~ the electrical ~e~ola~~ation time, el@c~r~-rnecb~~~~~~ couniing, and the isometric ~~~~~~~~~ former two have not been observe ac~l~~ic ~ane~vers~

~aometric co~tractio~ time.’ ric cont~~ction time canno ariations

in the

patients with complete 1 er with hemibloc~.~z,13 It

bundle branch block, s been ~b~w~ that the

branch block iyl the absence of left

Ziady, Hardarson,

and Curie1

Fig. 4. The simultaneous recording of the mitral echogram tipped catheter (LVP), Lv dp/dt, and electrocardiographic actly with the onset of left ventricular pressure rise.

WCG), left ventricular pressure using lead. The B-point of the mitral echogram

a manometercoincides ex-

PCG ECG Fig. 5. The simultaneous recording of the external carotid pulse curve (CP), mitral echogram diogram (PCG), and electrocardiographic lead from a patient with congestive cardiomyopathy. the mitral echogram is well-defined.

systole.15This point is usually defined with confidence in normal subjects, but may be difficult to determine in patients with heart diseases. Spodick and KumaP felt that this method fulfilled their criteria in their study of normal subjects. However, wide variations in the type of tracings illustrated in reports from various laboratories, and difficulties in obtaining satisfactory records in patients with thick chest walls, obesity, emphysema, and some types of heart diseases have made this method somewhat less than idea1.9,17,18 The normal mitral echogram was described by

204

(UCG), phonocarThe B-point of

Edler.lg With the onset uf ventricular diastole, the anterior leaflet of the mitral valve moves rapidly anteriorly to a sharp peak, the E-point; following this rapid valve opening, the anterior leaflets move posteriorly or toward a closed position. After some minor oscillations during diastole, the valve opens again following atria1 contraction. At the onset of systole, the curve falls abruptly forming segment B-C as designated by Edler (Fig. 51. The B-point forms a shelf on the closing downstroke of the mitral valve echo. We have found it to be constant and reproducible from one subject to another and in the same sub-

February,

1975, Vol. 89, No. 2

ta another. sometimes,the ntified, bnt if the transduce directed toward a point between the edge of the valve and the mitral annulus, the B-point will usually be clearly seen The B-point is often more evident in patients with an abnormally functionmg left ventricle, than in patients with a- normally functioning left ventricle or in normal inlsZoWe tested the time relationship of the with the onset of isometric contraction of ventricle in three patients by simultaneously recording the mitral echogram with the left ventricular pressure curves as recorded through a catheter-tip manometer (Fig. 4). We found in these patients that the -point coincided with the onset of rise of le ventricular pressure curve. In the eleven patients in whom we orded the internal isometric contraction time cardiac ~atheter~atio~, an excellent correlation was found between the internally measured and the ~trasonically measured isometric contraction time (Fig. 2). The mean isometric contraption time as measured by the ultrasound was found to be 5.7 msec. longer than the isometric contraction time. ~lthougb the difference was not significant, this was not an unexpected finding, because the internally reworded isometric contraction time in s calculated from pressure curves ugh saline-filled manometer with elay in the system. earliest onset of systole, contraction of the and the ‘subendocardial oes not give rise to an apelevation in intracavitary pressure, derable deep intramuscular pressure rise has been recorded in dogs’ before the left v ricular pressure starts to rise. e of the limitations of the method of using the ultrasound is the fact that a satisfactory ram with a clear B-point may take time to obtain. This applies espen whom the mitral valve cially to normal peo leafiets are thin an ove very fast. Neverthe1s study that the isometric ~~ntr~~tion time as measured by the ultrasound ethod is convenient, sensitive, and physioloc metho o measure the isometric contraction time. It is well suited for bedside evaluation of patients with myocar al disease and their differentiation from normal subjects. It seems superior to the external isometric contraction time and it

diae ~~theteri~atio~ patients

due t

have to a

Con.

contraption time were scussed. ~~t~asQ~ieally erived isometric ~~ntra~tio~ time nal carotid pulse trac measured.

Ree

athy 61, congestive emit heart disease (4 results were ~orrelate~ wit metric ~a~tr~~t~~~ ti metric ~ontra~tio~. tim

showed

less correlation

wit

shorter (I? ( 0.01). The ‘§o~et~ie contraction time showed a s~~~~~~ ~~~~~i~~i~~ti~~ value to the external iso~~~r~~ ~~~~t~~ct~~~ t for ~~ere~tiati~g the normal subjeds from patients’ group. &&ley Zoltart

I-.

2.

3.

ratefbl to Professor 3, F. Go for their great help and a for his assistance in reviewing the ~~~~~c~~~t.

Agress, C. M., and Wegner, S.: The ~ete~~~na~ts of lek ventricular isometric contract~Qm time, Jap. Heart J. 9:169, 1968. .1 et al.: True Metzger, C. C., Chough, C. B., Kroetz, F. isovolurnic contraction time and its c~~e~ati~~ with easily measured external indices ~fv~~t~~c~~~r contracSty, Circulation ~~~~~~~1. 31, 1 Weissler, A. M., Harris, W. S., and SchoePrfeld, C. II.: Bedside techniques for the e~a~~~~~~ of ventricubr function in man, Am. J. Car&ol. 23.577, 1969.

Ziady, Hardarson,

4. 5.

6.

10.

11.

12.

206

and Curie1

Rushmer, R. F., Finlayson, B. L., and Nash, A. A.: Movements of the mitral valve, Circ. Res. 4:337, 1956. Beck, W., and Schrire, V.: An attempt at the assessment of myocardial contractility from phonocardiographically measured time components of ventricular contraction in patients with prosthetic aortic valves, Circulation 33489, 1968. Braunwald, E., Fishman, A. P., and Cournand, A.: Time relationship of dynamic events in the cardiac chambers, pulmonary artery, and aorta in man, Circ. Res. 4~100, 1956. Dieudonne, J. M.: Tissue-cavitary difference pressure of the dog left ventricle, Am. J. Physiol. 213:101, 1967. Dibartolo, G., Nunez-Dey, D., Muiesan, G., et al.: Haemodynamic correlates of the first heart sound, Am. J. Physiol. 201~888, 1961. Weissler, A. M., Lewis, R. P., and Leighton, R. F.: The systolic time intervals as a measure of left ventricular performance in man, in: Progress in Cardiology, Yu, P. N., and Goodwin, J. F., editors. ed. 1. Philadelphia, 1972, Lea and Febiger. Luisada, A. A., MacCanon, D. M., Coleman, B., et al.: New studies on the first heart sound, Am. J. Cardiol. 28:141, 1971. Frank, M., and Kinlaw, W. B.: Indirect measurement of isovolumic contraction time and tension period in normal subjects, Am. J. Cardiol. 10~800, 1962. Baragan, J., Fernandez, F., Coblence, B., et al.: Left ven-

13.

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16. 17.

18. 19. 20.

tricular dynamics in complete right bundle branch block with left axis deviation of QRS, Circulation 42~797, 1970. Baragan, J., Fernandez, F., Sozutek, Y., et al.: Chronic left complete bundle branch block. Phonocardiographic and mechanocardiographic study of 30 cases, Br. Heart J. 30:196, 1968. Bourassa, M. G., Boiteau, G. M., and Allenstein, B. J.: Hemodynamic studies during intermittent left bundle branch block, Am. J. Cardiol. 10:792, 1962. Bush, C. A., Lewis, R. P., Leighton, R. F., et al.: Verification of systolic time intervals and the true isovolumic contraction time from the apexcardiogram by micromanometer catheterization of the left ventricle and aorta, Circulation 42:(Suppl. 3)1, 1970. Spodick, D. H., and Kumar, S.: Isovolumic contraction period of the left ventricle, AM. HEART J 76:498,1968. Benchimol, A., and Dimond, G.: The normal and abnormal apexcardiogram, its physiologic variations, and its relation to intracardiac events, Am. J. Cardiol. 12~368, 1963. Benchimol, A., and Dimond, G.: The apexcardiogram in ischaemic heart disease, Br. Heart J. 24581, 1962. Edler, I.: Ultrasonic cardiography in mitral valve stenosis, Am. J. Cardiol. 19:18, 1967. Feigenbaum, H.: Clinical application of echocardiography, Progr. Cardiovasc. Dis. 14531, 1972.

February,

1975, Vol. 89, No. 2