JANUARY VOL. 51

CirculIation

1975 NO. 1

AN OFFICIAL JOlURNAL ofthe AMERICAN HEART ASSOCIATION

EDITORIAL

Echocardiographic Examination of the Left Ventricle of echoes from the posterior left ventricular wall. These echoes most likely originated from the epicardium and at times possibly the pericardium. With the early techniques it was not easy to identify the echoes in each case because the gain settings frequently varied from one study to another. Another inherent problem was that there were several areas of the posterior left ventricular wall from which one could obtain similar echoes. Thus the examination was difficult to standardize when trying to compare one patient with another. Furthermore, only one left ventricular segment was used to assess over-all ventricular function. Such a technique could be particularly misleading when examining a ventricle with segmental impairment, such as occurs with coronary artery disease.9 Despite these problems, the technique proved to be of some value in following a given individual. Investigators used this application to study changes in left ventricular wall motion and location during exercise,3' 4following vasoactive drugs5 and following cardiac transplantation.'0 Thus although the examination of echoes from the posterior left ventricular wall, especially the epicardial echoes, has significant limitations, it can still be of some value in specific situations. Investigators have looked at echoes from the base of the heart or the mitral annulus in order to assess left ventricular function." It was noted that when one records echoes from the mitral annulus or the mitral ring with the transducer near the cardiac apex, one can record an echo which exhibits a pattern of motion very similar to an inverted ventricular volume curve. It was postulated that the motion of this echo was in some way related to left ventricular stroke volume." In fact an empirical formula was devised for estimating left ventricular stroke volume12 using the

MUCH OF THE recent enthusiasm for echocardiography stems from claims that this diagnostic tool can be used to evaluate left ventricular performance. As with any new development in medicine, misconceptions and misunderstandings have arisen. Some of the reasons for the confusion can be better understood if one knows how the various echocardiographic techniques for examining the left ventricle evolved and how they are still evolving. There have been many proposed echocardiographic applications for looking at left ventricular function. Probably the first approach was to look at echoes originating from parts of the posterior left ventricular wall. In early studies Edler noted that the echo from the "posterior wall of the heart" moved anteriorly about a centimeter with ventricular systole.' He also observed that with aortic valve incompetence the range of motion of this echo increased. This observation essentially went unnoticed until attention was again drawn to the "posterior wall echo" for the diagnosis of pericardial effusion.2 It became obvious that this echo originated, at least in part, from the left ventricle and investigators began using it to examine ventricular function.3 8 One of the problems with these studies was that the various components of the echoes from the left ventricular wall were not recognized at that time. Most of the early studies involved recording a dominant, singular echo or group From the Department of Medicine, Indiana University School of Medicine and the Krannert Institute of Cardiology, Marion County General Hospital, Indianapolis, Indiana. Supported in part by the Herman C. Krannert Fund, and USPHS

Grants PHS HE-09815-08, HL-6308-HL-5363-HL-5749. Address for reprints: Dr. Harvey Feigenbaum, Departmert of Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202.

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amplitude of the mitral ring echo together with a gross estimate of left ventricular size,13 which in retrospect actually included part of the right ventricle. This initial technique was indeed crude, but it did help to stimulate interest in the possibility of using echocardiography to estimate left ventricular volumes. Although there have been very few recent studies involving the echoes from the base of the heart, these echoes probably do possess useful information concerning left ventricular function, and they may warrant further investigation. A measurement of left ventricular wall thickness became possible when it was noted that the posterior left ventricular endocardial echo could be recorded by increasing the gain and by careful direction of the ultrasonic beam. 4 The wall thickness measurement compared favorably with similar measurements made at autopsy, surgery,14 and angiography."5 16 The endocardial echo also proved to be valuable in assessing posterior left ventricular wall motion. It was probably more reliable than the epicardial echo because the endocardial echo could be standardized better. Rediscovery of the interventricular septal echoes greatly improved the examination of the left ventricle. Edler identified echoes from the interventricular septum in the region of the left ventricular outflow tract. However, the septal echoes were largely ignored until it was noted that by recording echoes from the interventricular septum deeper in the ventricle, one could obtain an estimate of the right and left ventricular size. '7 This observation then led to the possibility of obtaining an internal dimension of the left ventricle between the interventricular septum and the posterior left ventricular endocardium.'8 '9 The identity of the endocardial and septal echoes was subsequently verified by intracardiac injections of indocyanine green dye.20 When this dye is injected in the left ventricle, it produces a cloud of echoes which outlines the borders of the left ventricular cavity. The original study to correlate the echocardiographic dimensions and left ventricular angiographic volumes was done in 1968 at which time the majority of patients undergoing cardiac catheterization had congenital or valvular problems.'8, 21 Although the initial studies were relatively crude, were done by a number of inexperienced people, and were not done simultaneously, the correlations were quite good and the results were encouraging. Several members of the original group that did this cooperative study went on independently to substantiate the clinical usefulness of using the distance between the septum and the posterior left ventricular endocardium to estimate ventricular volumes.22, 23 These observations were confirmed by subsequent investigators,24-26 and this particular

technique is probably responsible for much of the enthusiasm for using echocardiography to examine the left ventricle. One of the problems in using a single dimension to estimate ventricular volumes was that the dimension had to be standardized so that it was similar in all patients. It became readily apparent that one could obtain more than one dimension through the left ventricle. For example in a normal left ventricle which tapers toward the apex, a dimension taken near the left ventricular apex would be smaller than one through the body of the left ventricle. In order to make certain that the ultrasonic dimension was taken through the body of the left ventricle, it was determined that parts of both mitral valve leaflets or chordae should be present in the echocardiographic tracing.27 As the ultrasonic beam would approach the cardiac apex, these valvular structures would not be present. One might find echoes from the papillary muscles, but these echoes did not exhibit the characteristic rapid valvular motion during diastole. Thus requiring the recording of echoes from both mitral valve leaflets gave some assurance that the ultrasonic dimension was being obtained through the body of the ventricle and not near the cardiac apex. There was also the possibility of directing the ultrasonic beam too closely towards the base of the heart. Again the criteria of requiring both mitral valve leaflets prevented this error since the posterior leaflet usually would no longer be recorded if the ultrasonic beam was directed too superiorly. In addition one frequently lost the posterior left ventricular echo with this type of ultrasonic orientation. Although one might continue to record excellent interventricular septal echoes, the left atrium might now represent the posterior wall echo. Thus requiring parts of the mitral valve as well as the septum and posterior left ventricular endocardium to be present when obtaining the echocardiographic left ventricular dimensions provides some assurance that one is obtaining the same dimension on every patient. One further precaution when using this echocardiographic technique is that the left ventricular dimension will be influenced by the interspace in which the transducer is placed. The normal placement of the transducer is usually along the left sternal border, approximately in the fourth intercostal space. However this position varies since the relationship of the heart to the chest is different from one patient to another. The standard left ventricular dimension requires that the transducer is in a mid-position with relationship to the left ventricular cavity. This midposition means that the ultrasonic beam is essentially perpendicular to the mitral valve echoes and is aimed almost directly posteriorly into the chest. In addition Circulation, Volume 51, January 1975

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one can know whether the ultrasonic dimension is in a mid-position by the relationship of the interventricular septum and the anterior wall of the aorta. Normally these two structures are equidistant to the transducer. If one has the transducer too high, then the aortic wall will be closer to the transducer than is the septum. If one has the transducer too low, then the reverse situation exists. Thus by noting the direction of the transducer with relation to the chest wall and also by observing the relationship of the septum to the anterior wall of the aorta, one can have some assurance that the ultrasonic beam is in the midportion of the left ventricle when obtaining the left ventricular dimensions. One of the more common errors in some of the earlier studies was the failure to record the posterior left ventricular endocardial echo. This echo was admittedly more difficult to record than is the posterior epicardial echo. Naturally the dimensions would be somewhat different, and this difference in technique did produce some confusion. Fortunately most echocardiographers now recognize this problem and almost all take measurements from the endocardial echo. As a result of these studies, people began to assume that echocardiography measured left ventricular volume. The fact is that echocardiography does not measure left ventricular volumes. Echocardiography, as described in these studies, provides an internal left ventricular dimension. If one assumes that the ventricle is contracting symmetrically and that it is roughly a prolate ellipse with a uniform shape, then there is a statistical correlation between the dimensions and the corresponding volumes. In a uniformly contracting chamber, such as occurs with congenital and valvular heart disease, or myopathy, these assumptions are reasonably valid. However when the ventricle is segmentally diseased, as occurs with coronary artery disease, the situation is quite different.28 In these patients the two areas of the ventricle examined by the "standard" echocardiographic approach may no longer be representative of the entire ventricle. For example, in a patient who has had an infarction involving the apex of the left ventricle, an examination of the septum and the posterior left ventricular wall may indicate a well contracting ventricle with a large stroke volume. However because the large akinetic or dyskinetic apical segment was not examined on the echogram, this calculation would be grossly too high. On the other hand, if the septum were diseased and moved abnormally, then the calculated stroke volume might be artificially too low. In addition, with a markedly deformed ventricle, such as may occur with an aneurysm, the prolate ellipse model no longer may be satisfactory in calculating the volumes. Of course,

this limitation also is true for the angiographic technique for calculating volumes. Where then do we stand with regard to the echocardiographic evaluation of the left ventricle? In patients with valvular heart disease, congenital heart disease, or diffuse cardiomyopathy, the standard left ventricular internal dimension can provide a reasonably accurate estimate of the corresponding ventricular volumes. One can use these dimensions to calculate diastolic volume, systolic volume, stroke volume, and ejection fraction.23 In addition one can measure the rate of circumferential shortening.29 One may need to make some allowance for dilated hearts whereby the ratio of the long to short axis changes. There are regression equations which have been used to allow for this slight discrepancy.30 This problem is probably not as great as might be anticipated because one can usually predict whether the ventricle is going to be spherical or ellipsoid from the echocardiographic diastolic dimension. In addition the echocardiographic dimension is not a true short axis and undoubtedly includes part of the long axis.21 In patients with coronary artery disease, one probably should use different echocardiographic criteria for the evaluation of the left ventricle. The standard diastolic internal dimension may still give an estimate as to whether or not the over-all left ventricle is dilated. Such a dimension usually involves at least one nonischemic segment of the ventricle. One must remember that this measurement does not necessarily represent left ventricular volume. Such an estimate of left ventricular size might be particularly useful in following patients with an acute myocardial infarction, but even this application remains to be proven. Several groups of investigators have correlated the standard left ventricular echocardiographic dimensions with angiographic ventricular volumes, ejection fractions, and mean rate of circumferential shortening in patients with coronary artery disease.3' Virtually all investigators agree that attempts at measuring stroke volume are fraught with error because of the nonuniform nature of the disease. However one group of investigators feels that the diastolic dimension still provides a useful estimate of diastolic volume even with segmental wall motion abnormalities.32 Another study shows that the mean velocity of circumferential shortening may still be a useful measure of over-all ventricular performance in patients with coronary artery disease.33 One possible explanation for this finding is that even though the dimension may include one ischemic and one nonischemic segment, the nonischemic wall frequently moves excessively. Thus the calculated mean velocity of circumferential shortening may still give a gross estimate of over-all ventricular performance. There remain theoretical

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objections to this claim and further confirmation is obviously necessary. One echocardiographic technique for examining the left ventricle in patients with coronary artery disease is to make an effort to record echoes from as many different parts of the left ventricle as possible.34 One can probably examine more of the left ventricle than was initially suspected. Several areas of the septum and posterior ventricular wall can be recorded by tilting the transducer towards the apex with the transducer in the usual position along the left sternal border.34 By placing the transducer in a lower interspace, one can record yet more of the septum and the posterior and inferior ventricular walls. In fact it is probably possible to record echoes very close to the cardiac apex even in patients with coronary artery disease.35 A recent technique describes how one can record the anterior left ventricular wall by moving the transducer a centimeter or two to the left of the sternum so that it no longer lies over the interventricular septum.36 In addition the left ventricle can be examined with the transducer in the subxiphoid area.37 This approach permits one to see yet a different area of the interventricular septum and a portion of the posterior-lateral wall of the left ventricle. All of these different examinations may be useful in detecting akinetic or dyskinetic segments of the left ventricle. It is possible that by examining all of these different areas, one may even be able to quantitate the degree of left ventricular dysfunction. There are several ways in which one can examine the individual portions of the left ventricle. It is possible merely to measure the amplitude of motion of the wall segments.34 Echocardiography probably can measure the amplitude of wall motion with greater accuracy than any other technique, even including left ventricular cineangiography. One may also choose to measure the rate of motion of the wall segment during systole or diastole. Because the sampling rate is a thousand per second, the frequency response will permit reasonably accurate measurements of rates of wall motion. Some investigators have used computors to help analyze this motion and have recorded possibly useful information.38 There is also the possibility that one may measure the amount of thickening of the wall during systole.39 Such a measurement could conceivably be an indicator of ischemic muscle.40 Lastly there is the theoretical possibility that fibrotic, scarred muscle might differ echocardiographically from merely ischemic muscle. Scar tissue, having a higher density, could possibly produce more intense echoes and the scarred walls could be thinner than walls which are only ischemic.34 I must emphasize that some of these possibilities are still only theoretical and remain to be substantiated. They are mentioned

primarily to indicate potential avenues of investigation. There are several important technical problems in examining patients with coronary artery disease. Besides the barrel chest which is commonly found in patients with this disease and which interferes with the transmission of ultrasound, the left ventricular echoes frequently move poorly; and it is difficult to identify echoes which do not move well. One possible way of alleviating this problem is by moving the transducer during the recording so that the ultrasonic beam goes from areas where the walls move well to areas where the walls do not move well.28 In such a way one can connect the two areas and make a more meaningful diagnosis in the area of poorly moving echoes. This technique is particularly useful if one slows the recording speed of the strip chart recorder.35 This method of recording also provides information concerning the over-all shape of the left ventricle. Preliminary observations suggest that this technique might be particularly useful in the detection of left ventricular aneurysms.35 In addition we have noted that a large (3/4 inch), lower frequency (1.6 megaHertz) transducer improves the chances of obtaining recognizable echoes from these frequently difficult patients. Despite these recent technical advances, the echocardiographic examination of patients with coronary artery disease can still be extremely difficult. Thus the examination should only be attempted by a well trained, experienced echocardiographer. There has been interest in using cross-sectional or two-dimensional echocardiography to examine the left ventricle. Single element M-mode echocardiography lacks spatial orientation. Even though Mmode scanning can give some gross impression as to the shape of the ventricle, the accuracy of this approach is definitely limited. This fact also hinders the possibility of obtaining true ventricular volumes with M-mode echocardiography alone. There are several cross-sectional echocardiographic systems which have been developed to record the left ventricular cavity in two dimensions. Actually cross-sectional echocardiography is not new and has been available for over ten years. This technique has been primarily used by the Japanese and has been called " ultrasonocardiotomography. '41, 42 Partially because of the interest in using ultrasound to examine the left ventricle, there has been renewed investigational activity in crosssectional techniques. One method of recording cross-sectional echocardiographic images is by using a standard B-scan echograph similar to the type used for abdominal ultrasonic scans.43-4' An electrocardiogram is used to gate the oscilloscopic image so that only diastole or Circulation, Volume 51, January 1975

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systole is recorded. The cross-sectional image is then a composite of multiple cardiac cycles. This approach does provide more than a single dimension by which to estimate ventricular volumes,"4 but it also has several difficulties. First of all a large number of cardiac cycles is required for each individual examination, thus such a study can be quite lengthy. Any arrhythmia or motion of the chest during the examination will naturally distort the picture. In addition this system takes a "slice" through the heart in one plane. One must remember that unlike an angiocardiogram which records the roentgenographic cardiac shadow, an echocardiogram will only detect echoes from structures which are approximately perpendicular to the ultrasonic beam. There are very few planes within the heart to which the cardiac walls are continuously perpendicular. For example when examining the left ventricle with this technique, it is very common for one of the walls to drop out because the fine adjustments needed to continuously record this structure cannot be made. One may record the upper portion of the interventricular septum, but by the time the ultrasonic beam is directed towards the apex, one can no longer clearly identify this structure.46 Interest in real-time echocardiography has been stimulated by an engineering development by Dr. Bom in the Netherlands.47 He developed a multielement system for examining the heart. This system essentially uses 20 transducers which send out parallel ultrasonic beams. The transducers are fired sequentially very rapidly. Because of the very fast electronic switching the transducers are essentially firing simultaneously. This system thus provides 20 virtually simultaneous, parallel, "ice-pick" views of the heart. The end result is an angiogram-like, real-time examination of the heart. A moving picture or video tape presentation of such a recording can be most impressive as one sees the various cardiac structures moving in real-time. This system also has its inherent problems. These problems include such matters as lateral resolution, especially on the individual still pictures, difficulty in recording the cardiac apex in long axis because of limitations in angling the transducer, and the requirements of a large echocardiographic "window," something that is rarely present in adults with coronary artery disease. There is a great deal of current investigation using the multi-element system.48 52 Some of the results in examining patients with congenital heart disease look very promising.5` Further studies are obviously necessary to determine whether some of the problems in examining the left ventricle using this technique can be resolved with further experience and improvements in instrumentation. There are other ways of obtaining real-time, cross-

sectional echocardiographic images. Electronic steering of the ultrasonic beam is being investigated as one means of providing a two-dimensional echocardiogram.53 This approach is very sophisticated and has many theoretical advantages. This work is still in a preliminary state of development. As of now the instrumentation is very complicated and expensive. Investigators have been using mechanically driven transducers which provide a sector scan of the heart. This technique is essentially the approach which the Japanese have used for nearly ten years.41 42 Their transducer was usually in a water bath. More recently this application has been revitalized by placing the transducer on the skin surface.54' 5 A group of physicians at the National Institute of Health have been using such a system to examine several types of cardiac abnormalities.54 They have already reported some possible clinical applications; however, they have not as yet demonstrated any usefulness in evaluating the left ventricle, other than obtaining a cross-sectional recording of the interventricular septum in patients with hypertrophic subaortic stenosis. It is too early to predict whether any of the crosssectional echocardiographic techniques will significantly improve the echocardiographic assessment of left ventricular performance. It seems quite possible that any or all of these techniques should at least provide a qualitative assessment of left ventricular shape, but even that remains to be seen. As of now, all of the cross-sectional instruments are still in the developmental stages, and their full potential is still unknown. These instruments should be considered as potential supplements and not replacements of M-mode echocardiography. One must not forget that the M-mode's ability to record wall motion on a strip chart with a sampling rate of 1000 per second is a tremendous advantage that even the best cineangiocardiogram cannot match. One can obtain information about left ventricular performance by looking at other parts of the echocardiogram besides the left ventricular walls. The mitral valve has been studied extensively as a possible indicator of altered left ventricular hemodynamics. There is evidence that the pattern of mitral valve motion may reflect changes in left ventricular diastolic pressure.56 In patients who have an elevated left ventricular end-diastolic pressure because of poor ventricular compliance and a markedly elevated atrial component, there is a distortion of the mitral valve echo. Closure is altered in a predictable way so that one can tell from the echocardiogram when the left ventricular end-diastolic pressure is markedly elevated. It has also been demonstrated that in patients with severe aortic insufficiency, the mitral valve will frequently close prematurely as the left ven-

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tricular diastolic pressure rises.57 This finding usually indicates the need for aortic valve surgery. Several groups of investigators have attempted to use the mitral valve to estimate mitral valve flow. Some physicians have looked at the rate of rise of initial mitral valve opening58 and others have looked at the separation between the anterior and posterior mitral leaflets during diastole.59 There is probably some validity to both approaches in that the mitral valve does seem to move faster and with greater amplitude when larger amounts of blood flow across it. However none of the techniques have been developed to the point that they can be used in a very practical manner at the present time. Further study and refinement of these techniques are obviously necessary. There have been some observations that the aortic valve motion may reflect flow across the aortic valve. It has been noted that with severe hypertrophic subaortic stenosis60 27 or even with discrete subaortic stenosis,6' there may be mid-systolic closure of the aortic valve as blood flow into the aorta is impeded by the obstruction. In patients with low cardiac output or mitral insufficiency, the aortic valve frequently gradually closes during systole.27 A recent study suggests that there even may be a correlation between the amplitude and duration of aortic valve separation and aortic valve flow. 62 These observations again need verification, but they do indicate other possible ways of using the echocardiogram to look at left ventricular hemodynamics. Although there remain significant limitations in the echocardiographic examination of the left ventricle, there is still a great deal of valuable information that can be obtained from this examination provided that one appropriately and carefully uses the echocardiographic techniques which have been described. With the increasing number of good investigators entering the field, and with the many potential technical and engineering improvements yet to be explored, there is every reason to believe that some of these limitations will be eliminated and that echocardiography will become one of the best methods available for judging left ventricular performance. HARVEY FEIGENBAUM, M. D.

after exercise. Am Heart J 79: 36, 1970 5. KRAUNZ RF, RYAN TJ: Ultrasound measurements of ventricular wall motion following administration of vasoactive drugs. Am J Cardiol 27: 464, 1971 6. CARSON P, KANTES L: Left ventricular wall movement in heart failure. Br Med J 4: 77, 1971 7. WHARTON CF, SMITHEN CS, SOWTON E: Changes in left ventricular movement after acute myocardial infarction measured by reflected ultrasound. Br Med J 4: 75, 1971 8. FOGELMAN AM, ABBASI AS, PEARCE ML, KATTUS AA: Echocardiographic study of the abnormal motion of the posterior left ventricular wall during angina pectoris. Circulation 46: 905, 1972 9. LUDBROOK P, KARLINER JS, LONDON A, PETERSON KL, LEOPOLD GR, O'ROURKE RA: Posterior wall velocity: An unreliable index of total left ventricular performance in patients with coronary artery disease. Am J Cardiol 33: 475, 1974 10. PoPP RL, SCHROEDER JS, STINSON EB, SHUMWSAY NE, HARRISON DC: Ultrasonic studies for the early detection of acute cardiac rejection. Transplantation 11: 543, 1971 11. ZAKY A, GRABHORN L, FEIGENBAUM H: Movement of the mitral ring: A study of ultrasoundcardiography. Cardiovasc Res 1: 121, 1967 12. FEIGENBAUNI H, ZAKY A, NASSER WK: Use of ultrasound to measure left ventricular stroke volume. Circulation 35: 1092, 1967 13. FEIGENBAuM H, HELMEN CH, NASSER WK, HAINE CL: Estimation of left ventricular diastolic volume using ultrasound. (abstr) Circulation 36 (suppl II): 11-106, 1967 14. FEIGENBAuM H, PoPP RL, CHIP JN, HAINE CL: Left ventricular wall thickness measured by ultrasound. Arch Intern Med 121: 391, 1968 15. SJOGREN AL, HYTONEN I, FRICK MH: Ultrasonic measurements of left ventricular wall thickness. Chest 57: 37, 1970 16. TROY BL, PORIBO J, RACKLEY CE: Measurement of left ventricular wall thickness and mass by echocardiography. Circulation 45: 602, 1972 17. PoPP RL, WOLFE SB, HIRATA T, FEIGENRAUMI H: Estimation of right and left ventricular size by ultrasound. A study of the echoes from the interventricular septum. Am J Cardiol 24: 523, 1969 18. FEIGENBAUM H, WOLFE SB, PoPP RL, HAINE CL, DODGE HT:

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Correlation of ultrasound with angiocardiography in measuring left ventricular diastolic volume. (abstr) Am J Cardiol 23: 111, 1969 CHAPELLE M, MENSCH B: Etude des variations due diametre ventriculaire gauche chez l'homme par echocardiographic transthoracique. Arch Mal Coeur 11: 1505, 1969 FEIGENRBAUi H, STONE JM, LEE DA, NASSER WK, CHANG S: Identification of ultrasound echoes from the left ventricle using intracardiac injections of indocyanine green. Circulation 41: 615, 1970 FEIGENR3AuIJ H, PoPP RL, WOLFE SB, TROY BL, POMBO JF, HAINE CL, DODGE HT: Ultrasound measurements of the left ventricle: A correlative study with angiocardiography. Arch Intern Med 129: 461, 1972 PoPP RL, HARRISON DC: Ultmsonic cardiac echography for determining stroke volume and valvular regurgitation. Circulation 41: 493, 1970 PONIRO JF, TROY BL, RUSSELL RO JR: Left ventricular volumes and ejection fraction by echocardiography. Circulation 43:

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Determinations of left ventricular volumes by ultrasound. Circulation 44: 575, 1971 25. GIBSON DG: Measurement of left ventricular volumes in man Circulation, Volume 51, January 1975

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echocardiography-comparison angiographs. Br Heart J 33: 614, 1971

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26. MURRAY JA, JOHNSTON W, REID JM: Echocardiographic determination of left ventricular dimensions, volumes and performance. Am J Cardiol 30: 252, 1972 27. FEIGENBAUM H: Clinical applications of echocardiography. Prog Cardiovasc Dis 14: 531, 1972 28. FEIGENBAUM H: Echocardiography. Philadelphia, Lea & Febiger, 1972, p 199 29. COOPER RH, O'ROURKE RA, KARLINER JS, PETERSON KL, LEOPOLD GR: Comparison of ultrasound and cineangiographic measurements of the mean rate of circumferential shortening in man. Circulation 46: 914, 1972 30. TEICHHOLZ LE, KREULEN TH, HERMAN MV, GORLIN R: Problems in echocardiographic volume determinations: Echo-angiographic correlations. (abstr) Circulation 46 (suppl II): 11-275, 1972 31. RATCHIN RA, RACKLEY CE, RuSSELL RO: Serial evaluation of left ventricular volumes and posterior wall movement in the acute phase of myocardial infarction using diagnostic ultrasound. Am J Cardiol 29: 286, 1972 32. RATCHIN RA, BoYD CN JR, RACKLEY CE, MORASKI RE, RuSSELL RO JR: Quantitative echocardiography: Correlations with ventricular volumes by angiography in patients with coronary artery disease with and without wall motion abnormalities. (abstr) Circulation 48 (suppl IV): IV-48, 1973 33. LUDBROOK P, KARLINER JS, PETERSON K, LEOPOLD G, O ROURKE RA: Comparison of ultrasound and cineangiographic measurements of left ventricular performance in patients with and without wall motion abnormalities. Br Heart J 35: 1026, 1973 34. JACOBS JJ, FEIGENBAUM H, CORYA BC, PHILLIPS JF: Detection of left ventricular asynergy by echocardiography. Circulation 48: 263, 1973 35. FEIGENBAUNM H: Use of echocardiography in evaluating left ventricular function. Second World Congress on Ultrasonics in Medicine. Excerpta Medica, in press 36. CORYA BC, FEIGENBAUM H, RASMUSSEN S, BLACK MJ: Anterior left ventricular wall echoes in coronary artery disease. Am J Cardiol, in press 37. CHANG S, FEIGENBAUM H: Subxiphoid echocardiography. J Clin Ultrasound 1: 14, 1973 38. GIBSON DG, BROWN D: Measurement of instantaneous left ventricular dimension and filling rate in man using echocardiography. Br Heart J 35: 1141, 1973 39. WIRTH J, WENZELIDES K: Heart muscle thickening measurement with ultrasound. Cor Vasa 12: 112, 1970 40. GOLDSTEIN S, WILLEM DE JONG J: Changes in left ventricular wall dimensions during regional myocardial ischemia. Am J Cardiol 34: 56, 1974 41. NAGAYAMA T, NAKAMURA S, HAYAKAWA K, KoMio Y: Ultrasonic cardiokymogram. Acta Med Univ Kagoshima 4: 11-229, 1962 42. EBINA T, OKA S, TANAKA M, KOSAKA S: The ultrasonotomography for the heart and great vessels in living human

subjects by means of the ultrasonic reflection technique. Jap Heart J 8: 331, 1967 43. KING DL: Cardiac ultrasonography: A stop-action technique for imaging intracardiac anatomy. Radiology 103: 387, 1972

44. KING DL, JAFFEE CO, SCHMIDT DH, ELLIS K: Left ventricular volume determination by cross-sectional cardiac ultrasonography. Radiology 104: 201, 1972 45. TEICHHOLZ LE, COHEN MV, SONNENBLICK EH, GORLIN R: Detection of abnormalities of left ventricular wall motion by B-scan ultrasonography. (abstr) Circulation 48 (suppl IV): IV-127, 1973 46. KING DL: Cardiac ultrasonography: Cross-sectional ultrasonic imaging of the heart. Circulation 47: 843, 1973 47. BOM N, LANCEE CT, HONKOOP J, HUGENHOLTZ PC: Ultrasonic viewer for cross-sectional analyses of moving cardiac structures. Biomed Eng 6: 500, 1971 48. KLOSTER FE, ROELANDT J, TENCATE FJ, BOM N, HUGENHOLTZ PG: Multiscan echocardiography. II. Technique and initial clinical results. Circulation 48: 1075, 1973 49. ROELANDT J, KLOSTER FE, TENCATE FJ, VANDoRP WG, HONKOOP J, BOM N, HUGENHOLTZ PG: Multidimensional echocardiography. An appraisal of its clinical usefulness. Br Heart J 36: 29, 1974 50. Popp RL, BROWN OR, HARRISON DC: Diagnostic accuracy of an ultrasonic multi-transducer cardiac imaging system. (abstr) Circulation 48 (suppl IV): IV-125, 1973 51. SAHN DJ, TERRY R, O'ROURKE R, LEOPOLD G, FRIEDMAN WF: A new technique for the non-invasive study of cyanotic congenital heart disease. (abstr) Circulation 48 (suppl IV): IV81, 1973 52. KING DL: Real-time cross-sectional ultrasonic imaging of the heart using a linear array multi-element transducer. J Clin Ultrasound 1: 196, 1973 53. THURSTONE FL: Electronic beam scanning for ultrasonic imaging. Second World Congress on Ultrasonics in Medicine. Excerpta Medica, in press 54. GRIFFITH JM, HENRY WL: A sector scanner for real-time twodimensional echocardiography. Circulation 49: 1147, 1974 55. EGGLETON RC: Ultrasonic visualization of the dynamic geometry of the heart. Second World Congress on Ultrasonics in Medicine. Excerpta Medica, in press 56. KONECKE LL, FEIGENBAUM H, CHANG S, CORYA BC, FISCHER JC: Abnormal mitral valve motion in patients with elevated left ventricular diastolic pressures. Circulation 47: 989, 1973 57. PRIDIE RB, BEHAM R, OAKLEY CM: Echocardiography of the mitral valve in aortic valve disease. Br Heart J 33: 296, 1971 58. PENNOCK R, KINGSLEY B, KAWAI N, KIMBIRIS D, SEGAL BL: Stroke volume and cardiac output measured by echocardiography. (abstr) Am J Cardiol 25: 121, 1970 59. FISCHER JC, CHANG S, KONECKE LL, FEIGENRBAuMi H:

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Echocardiographic examination of the left ventricle. H Feigenbaum Circulation. 1975;51:1-7 doi: 10.1161/01.CIR.51.1.1 Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231 Copyright © 1975 American Heart Association, Inc. All rights reserved. Print ISSN: 0009-7322. Online ISSN: 1524-4539

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