CHRONIC CONSTRICTIVE PERICARDITIS. II. ELECTROKYMOGRAPHIC STUDIES AND CORRELATIONS WITH ROENTGENKYMOGRAPHY, PHONOCARDIOGRAPHY, AND RIGHT VENTRICULAR PRESSURE CURVES VICTOR A. McKUSICK The Clinic of General Medicine and Experimental T, herapeutics of the National Heart Institute (Cardiovascular Clinic, U. S. Marine Hospital, Baltimore, Md.) and the Department of Medicine, The Johns H opkins University and H. ospital Received for publication August 13, 1951 This is a report of electrokymographic findings in twenty patients who had chronic constrictive pericarditis. Clinical aspects of these cases are described in detail in an accompanying paper (1). In addition three patients were studied who had pericardial calcification without the constrictive syndrome. The ob- jectives of these studies were several: (I) Gillick and Reynolds (2, 3) described an electrokymographic (EKY) pattern which from their studies appeared to be quite characteristic of this condition. It was desirable to know how diagnos- tic this pattern is. (II) The value of electrokymography in evaluating results of operation was studied. (III) Correlative studies with roentgenkymography (RKY) were made to determine to what extent the latter method will demon- strate the characteristic pattern. (IV) Bloomfield et al. (4) and Hansen et al. (5, 6) have reported what they believe to be a fairly pathognomonic pattern of the right ventricular pressure curve in constrictive pericarditis. It was thought that simultaneous recordings of the EKY and the right ventricular pressure curve might shed light on the genesis and significance of each. (V) It was hoped to elucidate the nature of the protodiastolic sound of constrictive pericarditis by determining what is happening mechanically by means of simul- taneously recorded electrokymograms. Electrokymography (7, 8, 9, 10) is a method for detailed analysis of move- ment of individual points on the x-ray silhouette of the heart and great vessels. For details of the instrument! and its use, reference is made to the literature which now records a fairly extensive experience with the method. The tech- nique used for most of the studies has been described elsewhere (10). For the most part the carotid pulse was used for timing purposes. Figure 1 indicates the areas from which recordings of border movement were made as well as the conventions employed in labelling tracings. Of the twenty cases of constrictive pericarditis five have been studied only Pre-operatively, seven have been studied both before and after operation, and +The electrokymograph used in most of these studies was a commercial model manu- factured by the Cambridge Company, Ossining, New York. 27 28 VICTOR A. McKUSICK eight have been. studied at least once one to nine years following pericardec- tomy. ELECTROKYMOGRAPHIC FINDINGS The characteristic electrokymographic change of constrictive pericarditis (Figs. 2 and 3) is found in the ventricular border tracings and consists of a simplified pattern of “flat-tops and V’s”, the two limbs of the “V” representing systolic ejection and ventricular filling respectively, and the “flat-tops’’ repre- senting diastolic standstill. The characteristics of this pattern are as follows: (1) There are no secondary curves which ordinarily occur during isometric contraction, early ejection, and isometric relaxation due to positional and ro- tational movements. This is probably due to the fact that the encased heart is Fic. 1. Indicated ‘here are the positions on the cardiovascular silhouette from which electrokymographic recordings were made and the convention for labeling the individual tracings. not free to make the extra movements responsible for the inscription of these secondary components. (2) Ventricular filling is very rapid. The filling limb of the “V” is characteris- tically steeper than, or at least as steep as, the emptying limb. High atrial pressure on both the right and left side has been an invariable finding of cardiac catheterization in these cases (1) and is probably largely responsible for rapid filling. Elastic recoil of the rigid pericardium and of the thoracic cage structures to which it may be adherent might theoretically produce a rapid outward movement of the ventricular border in early diastole. At present there is no proof of this latter concept. In fact evidence of adhesions to the thoracic cage was notably absent in most of the cases in whom pericardectomy was per- formed. . (3) Ventricular filling comes to an abrupt end early in diastole and there is standstill of the ventricular border for the remainder of diastole. This is merely CHRONIC CONSTRICTIVE PERICAF ts 29 “an expression of the long recognized (11, 12) impediment to ventricular filling “Gn this condition. Other less constant electrokymographic features are as follows: (I) A late systolic plateau indicating, perhaps, an impediment to systolic emptying (Fig. 123 456 VENTRIGLE EKY NORMAL VENTRICLE EKY CONSTRICTIVE PERICARDITIS \ CAROTID PULSE gam, 2 ea “ Schematic representation of the normal ventricular border electrokymo- ease ticles fox : -top and V electrokymogram of constrictive pericarditis with carotid Pe trac g iming purposes. Phases of cardiac cycle: 1-2, isometric contraction; 2~3 arly ejection; 4~5, late ejection (“proto-diastole”); 5-6, isometric relaxation rae ost often seen over the upper left ventricular border (LV3 or LV4). nce ng to Stumpf (13) the late systolic or medial plateau was described in ee : ymograms by Heckmann, who applied to it the same significance we e to the corresponding EKY finding. (II) An ‘‘over-shooting” phenomenon 30 VICTOR A. McKUSICK is occasionally seen. This consists of a small rise above the main level of the diastolic plateau occurring at the end of rapid diastolic filling (Fig. 4). (ITD In the main pulmonary artery EKY there may be long flat diastolic plateaus which may indicate constriction of the pulmonary artery (Fig. 5). However, it may well be that they are an expression of close relationship between pul- apaeeeuannonvanmumnannarona neste? pennants ie MES ETT ibaees i atie askaecerieen te” ORUGR URCERNGS Et caahemasaceuers ee er enre Ser tuoannce anes CU anes PeAMeL ete E20 Seen ea a pes panes ae ain a: y eeeeneesont ae : 2 : a aesree’ es otto anata eet et Hee beapeeteries fas eteea: sims “Oa - eeer cen, | Sat eee ne! ja, Same Bein Vereeeeh : : Sainersngenecsrsceetressesemenseseaee BEFORE OPERATION AFTER OPERATION S.W.A. Fic. 3. This patient, case 1 (1), attained clinical cure from pericardectomy. Pre-operative electrokymograms showed an abnormal pattern of ventricular border movement of the “fiat-top and V” variety. Post-operatively the pattern returned to normal. monary ‘capillary’ pressure, pulmonary artery diastolic pressure, right ven- tricular diastolic plateau pressure, and mean atrial pressure. (IV) Dampening or obliteration of right auricular pulsations is frequently encountered. (V) Un- usually prominent pulsations may be recorded in a dilated superior vena cava. These recordings have the same contour as right atrial pressure recordings (1). Table I is a tabulation of the electrokymographic findings in this study. The characteristic “flat-top and V” pattern may not be demonstrable under CHRONIC CONSTRICTIVE PERICAn_ «TIS , 31 two circumstances: 1) tachycardia and 2) concealment of the lower ventricular borders by left pleural effusion and/or high left diaphragm due to ascites. A heart rate of more than about 120 will cause a fusion of the “Vs” and oblitera- tion of the diastolic plateau. The typical pattern may be suspected, however, from the presence of a steep filling limb and a V bottom. The typical pattern is always most prominent over the lower borders of the ventricles. Pleural ‘Fis. 4, This patient, case 13 (1), had continuation of manifestations of constriction in spite of two cardiac decortications. Shown here are a roentgenkymogram and, superimposed on it for purposes of graphic visualization, some of the electrokymograms. In each “frame” of the roentgenkymogram border movement is read from bottom to top. The records sh the over-shooting phenomenon at the end of rapid ventricular filling. ” effusions or a high diaphragm are likely to make it difficult or impossible to study the complete ventricular silhouette. In the differential electrokymographic diagnosis, bradycardia, as in com- plete heart block, is the principal condition which can produce “lat-tops and V’s” simulating those of constrictive pericarditis (Fig. 7). The distinguishing feature, however, is that bradycardia, unlike pericarditis, produces a filling limb less steep than the emptying limb. Furthermore there are likely to be secondary waves in bradycardia and none in constrictive pericarditis. A possible source of error to be avoided is having the small segment of the 32 VICTOR A. McKUSICK ee Fic. 5. This patient, case 2 (1), had auricular fibrillation at the time of these pre-operative EKY’s and RKY’s. The EKY’s show, in addition to the characteristic ventricular border pattern, abnormally flat diastolic intervals in the pulmonary artery tracings (PA). There are late systolic plateaus in LV4. The roentgenkymogram, in addition to revealing conspicu- ous diastolic plateaus, demonstrates, first, the large amplitude of pulsations at the left border in spite of generalized pericardial involvement and secondly, the effect of tachycardia in producing obliteration of the diastolic plateaus. Note the evidence of calcification on the left border. TABLE I ELECTROKYMOGRAPHIC FINDINGS NUMBER PATHOGNO- seers On ops | ATYPICAL | NORMAT AND V’s” mm —_— 1 | Pre-operative studies in constrictive pericarditis.......--- 12 ii i 4 Post-operative studies in constrictive pericarditis.......- 14 5* | oF Asymptomatic pericardial calcification... 6... . 00ers 3 | 3 * All five of these studies were in patients whose manifestations of constrictive pericarditis con- tinued after operation. + All nine of these studies were in patients who had clinical cures of their constrictive pericarditis following pericardectomy (Figs. 3 and 8). ventricular silhouette from which recording is made too near one Or the other end of the pick-up slit. As the University of Pennsylvania group (14, 15) has CHRONIC CONSTRICTIVE PERICA. .TIS 33 pointed out, in the EKY head of conventional design the sensitivity falls off sharply toward the ends of the slit. If the ventricular border were located near one end of the slit in diastole an artefactual diastolic “flat-top” might result whereas, if the border were too near an end of the slit toward the end of a4 systole, a medial, or systolic, plateau might occur. It is interesting to observe that the “‘flat-top” is largely wasted time for the heart—cardiac activity is at a standstill. It is clear, therefore, as has been con- firmed by study of output after atropine administration (16), that speeding the Fic. 6. These kymograms from Case 11 (1) show 1 i i extensive calcification of th border and the characteristic “flat-top and V” pattern. of the Tele hears constricted heart will improve cardiac output without expense to cardiac fillin Tn mitral stenosis, on the other hand, cardiac output is likely to drop with ne. celeration of the heart because of shortening of the left ventricular filling time which may be critical in mitral valve narrowing. Change in cardiac out ut with atropinization may be a point for differentiation between mitral stenosis and constrictive pericarditis. The characteristic ventricular motion which is recorded electrokymographi- cally as a “flat-top and V” pattern is occasionally very obvious in Auorosce on physical examination or at operation. Roessler (17) states that occasionally 34 VICTOR A. McKUSICK in some areas the ventricular motion may have ‘“‘a great amplitude with a rapid diastolic outward movement.” He also mentions the important differential point: ‘It reminds one, at first glance, of that seen...in marked bradycar- dia.’”’ Several of the cases in this series, particularly cases 3 and 8, had relative absence of constricting calcification in the region of the cardiac apex with what was in essence a herniation of the ventricle at that site. Fluoroscopically, this area of the ventricle showed movement which was grossly “‘flat-top and V” in character. The cases in whom this characteristic type of ventricular movement was apparent on physical examination are those in whom part of the left ante- L-LVp _ LW. 8-15-48 Fic. 7. This patient did not have constrictive pericarditis. He had chronic auricular flutter with complete atrio-ventricular dissociation. Note the auricular flutter waves in L60-LA. The pattern in RB1 and L-LV2 simulates that of constrictive pericarditis as fre- quently occurs in the presence of bradycardia. The pattern differs from constrictive peri- carditis in that first, the filling limb of the ‘““V” is less steep than the ejection limb and sec- ondly, secondary components, especially isometric relaxation are clearly indicated in some tracings (e.g. L-LV3). rior costal cage had been removed for pericardectomy but the manifestations of constriction continued after operation. Cases 13 and 14 (1) were of this type. In early diastole the ventricle expands rapidly and produces a forceful impact against the hand. Case 20 (1) in contrast to these two cases, for this patient, who has had apparent cure from pericardectomy with normal electrokymo- grams, has normal cardiac action as seen and felt through a large operative defect in the left anterior chest wall.’ 2 Under the term “diastolic heart beat” Wood (18) has recently re-emmphasized the diag- nostic value of systolic retraction and diastolic lift or impact which is a simple physical ex- pression of the “flat-top and V” pattern of the EKY. CHRONIC CONSTRICTIVE PERICARDIT . 35 ’ «Flat-top and V” type of movement may even be discernible electrocardio- graphically: In case 14 (1), V3 was recorded over the center of the chest defect There was a fairly consistent negative spike occurring soon after the T-wave and due probably to jarring of the electrode by the water-hammer effect at th end of ventricular filling. € Fic. 8. This patient, case 15 (1), had only roentgenkymograms pre-operatively A. : . : The left border shows conspicuous diastolic plateaus. Also demonstrated are the high right diaphragm due to hepatic enl a . . - ‘D rgement and fullness in the region of the superior vena eae seudies ‘tially an all to believe that the electrokymographic pattern bed -or-none reaction, i.e., it has no value in localizin raatriction as an ae to the surgeon. With the current surgical philosophy eto ean be removed to as large an extent as possible, information A oration of maximal constriction may be of less importance (19). did mat ee casts io seine calcification without the constrictive syndrome ee ws at-top and V” pattern. It is not always easy to identify a pericardial calcification as ‘‘asymptomatic.’”’ One of our patients who was subsequently VICTOR A. McKUSICK so labeled had bouts of left ventricular failure. It was be- lieved that this was due to his hypertension ; that constrictive pericarditis was not the cause is probably proved by the abse tern in electrokymograms. nee of the “‘flat-top and V”’ pat- RB, LY, -LERVY LL, Fic. 8 B. These electrokymograms show return to a normal pattern ment. The patient attained clinical cure. Rhy of ventricular border move- FINDINGS OF ROENTGENK YMOGRAPHY da very close correlation was found between EKY’s 8). Since the electrokymograph as used in these ate calibration of border excursion, one must rely on the roentgenkymograms for information as to absolute amplitude of border movement and on the electrokymograms for demonstration of diag- nostic changes in the pattern of border movement. However, more often than not the roentgenkymograms also show the “flat-top and V”’ pattern. Since in electrokymography amplitude of recordings can be controlled, the character- istic pattern may be demonstrated even in areas with little motion by roent- cenkvmoerabphy. As might be anticipate and RKY’s (Figs. 4, 5, 6, studies provides no means for accur CHRONIC CONSTRICTIVE PERICARDITIS | 37 In constrictive pericarditis roentgenkymograms may show normal or in- creased amplitude of contraction in some or most areas of the ventricular sil houette. It has been held (20) that this increased pulsation is the result of summation of contraction of right and left ventricles. The explanation is prob- ably a simple one: the ventricle contracts with compensatory increase in . lt tude in all areas where there is relatively less impediment to motion Coue 3 and 8 (1) had essentially a herniation of the heart in the region of the marcia apex where, because of greater mobility, one might anticipate resistance to rac development of constriction. Obviously this paradoxically large amplitude ; ventricular border excursion may be a source of confusion if the voentaenol ce or clinician anticipates diminished excursion as the only kymographic oes constrictive pericarditis. It is our experience that the cases with areas of i creased excursion show the lateral plateaus on RKY and “‘flat-top and V’s” in- EKY especially prominently in these same areas. For greatest succ son demonstrating the “flat-top and V” pattern by roentgenkymo ae in should be taken in right and left anterior oblique positions as well i he conventional postero-anterior projection. asm the SIMULTANEOUS RECORDING OF EKY AND RIGHT HEART PRESSURE CURVES Figure 9 represents a simultaneous recording of EKY and right heart pr sure curves. The ventricular pressure curve shows an artefactual flattening at the peak pressure level. The point of main interest is the timing of th a ly diastolic ‘‘dip” (1) as indicated by comparison with the EKY The “di . oe during the phase of rapid filling of the ventricle. . vee _Superficially the simultaneous EKY and ventricular pressure curv similar to the tracings of ventricular volume and ventricular pressure rec , di ‘d by Katz (21) from a model using the turtle heart. These curves were pre er ted as evidence for a suction action of the relaxing ventricle. Cotton 02) sinted out that the presence of a narrowing in the inflow system was neces ‘ary fe recording the diastolic “dip” from the model. This narrowing vevented " stantaneous equilibrium of pressure between the reservoir and the ventriculas evs with a resulting early diastolic ‘dip.’ In clinical constrictive pericarditis ocalized pre-ventricular inflow obstruction is absent (1) in the majority (prob ably all) of cases. For this reason the analogy to Katz’ model i vot apparent to the writer. # noe sppazent hase on auricular Pressure tracing also shows, during the ventricular filling roughly he P ee from calibrated recordings has been found to be of identity tonet me a = ute amplitude as that in the ventricle. This quantitative vortion. ee . er wit the close similarity in the contour of the early diastolic Aestolne wt e ventricular and auricular curves may be evidence that the early olic “dip” is a bona fide cardiodynamic phenomenon. 39 ‘Mme RECUUNBOSEQUGUSL. "ELATA SO AUAVaREDENDAANON’ ecrurgeeel SNARE RTE SARADE NB” ABEC HOES RT SABER SRARNEN” mud Rst eR Tes DUERERUCHUR EEE, «PRBUNRS A SES BEGAN ME day chERO REE RSH I Ag SMG irae reuasebaT eS ste aen, “HE Bei EUSUTULUEEane” savelneat ‘SOUSESEDERE ANG. “SUURORESGEA ESI zneae 50 szeyee “15 al SASAEULURGUEMEpEARE. sengaRatE if CARESEDERERAUE Nay.” Thee aaa Matinee ota rr JH 5 SAPARD CONTRA TO HEN oES cs PeaNR ANGURES NERDS SBEARATENY GET! SOURRRRMATONERUOREREES GUnetTEN BEUESEGAUARRNRDEBER ERAT Ueess: Bcrator eeeteHLLLTY dttuEs MAMRERBSEGIGENERDAD s2eeEnty: MACHU ENGNNRNEANR” ana TER Ey ag MARSHOLDEU SOG RA NAR ae. “HeRTT EN ENSRESEEASESP” .cHEH ENED! case 13 (1), has a split second sound but in addition a prominent GENERAL COMMENTS CHRONIC CONSTRICTIVE PERICARDITIS 2 ReRCRESCHNERS TRERREO 00/0) MM SUNSUUEERERESSEE (GENERA ONCE! Frc. 10. This patient uy a s = u ae) q wo > UO mt ao a wy a oO UO a wo vo a ~ oO S Z 9 wa} wn u Pp oO Yo ° <3 gq Zz 5 a oO = 9° wu) mr Sg oe) ° wm ° a o RS aH Jd q 3 O° a 3S Oo ee} wn Sg a OQ 2 2 m Q, od ou 3 ee ° oO o WW ° 2 a oO me a oO hd Bl Zo q a o 2 wD a yy ~ ° WwW so oO rm hd i oO xO oO wv 8 a he # wm a ° 8 uo ao wv) wo op & 4-27-50 * ae ‘i Sasi ok <= aie — * J.H. Sie reac eee 5 onan nanan naese oot aw, 3 VICTOR A. McKUSICK Bie atin = NE —— —— eS =; a it PRESSURE & RT, AUR GURVE ty WW x > 2m w7 “oo ul : a a. 38 ventitious protodiastolic sound. That the fundamental physiologic defect in constrictive pericarditis is an d impediment to diastolic filling of the ventricle is quite generally accepted. The observations reported here lend further support to this thesis. The several phenomena observed in this condition are all based on the filling defect: 1. The “flat-top and V” pattern of the EKY. 2. The a o nw Vv AESS2 s.20 o Pre 2. Bw OS Bs d2e BS. 2 Bkuw BEBE one e eee hw YO BE AaB Er SE Po Baw Oe Bea ‘a tO ao pi RO oa > MeERZESBEE omg BO wD aS & = HpomeapaeE SZeacgekeoss gmI Fg RB 20 4 wo ® a wo Go eo sO a ao oP 5 OoUG cS OAEA > Rea EGS Oo oO. 3 VE HHT SB Seg S wees Saas s DBmo Ms a augevaeso so ga G > S8RSe Rx 53 4.8.8 & © ae odovH Ga REREZ es abo aees wn So 8s oa 8 Baw Ae V8 8 Ee USF ee Suu: 22 3 3 mY 25 NBA SSB wH BOHR SE 8 a3 S9oo se one od sevEBEstge eo SAUDE 8 eg wags, Pad wn ~ seaea a. mig VW Hn > ™o ne en ee wo Wow SD i 2 34 Ss ga egeega Fe tA Sey SG 2 2 A oy BE VAws & & ao Zim x S & Oo or OR “2a gees SegoR SA we BOE BREE 26538 & ,a di- and diastolic plateau of the ventricular pressure a? ventricular filling. However, undoubtedly, there is, in such cases ventricular volume studies of Bing (25). defect of ventricular emptying as well. That such is the case appears to be in That many cases of constrictive pericarditis have some degree of cardiac cated by the residual enlargement (24) is not inconsistent with the view that the predominant defect 4. The large diastolic excursions of the ballistocardiogram (23). is one of 5. The ‘diastolic heart beat’ of Wood (18). 3. The early diastolic ‘dip curves (1). rotodiastolic sound 1s p esented in an accompanying The me relationships when heart r filling and with the abrupt halt a. | f the ti ously. been pr ing of the diastolic plateau. Probably the d simultane innt “dip” is bona fide. chronous with the end of rapid ventricu STOLIC SOUND OF CONSTRICTIVE PERICARDITIS a water-hammer phenomenon. A -early diastolic T THE PROTOD Clinical aspects of this finding have article (1). Figure 10 is representative 0 yn sounds and EKY are recorde in filling which occurs at the beg sound is, at least in part, evidence that the 5 40 VICTOR A. McKUSICK SUMMARY AND CONCLUSIONS 1. The electrokymographic pattern of “flat-tops and V’s” is highly diagnostic of chronic constrictive pericarditis. 2. At present one must rely on roentgenkymography for information as to absolute amplitude of ventricular border movement and on electrokymography for details of the pattern of that movement. However, more often than not, roentgenkymograms also show the “flat-top and Vv” pattern. 3. Electrokymograms are a valuable index of results of pericardectomy. 4, Normal patterns of ventricular border movement were found electroky- mographically and roentgenkymographically in three cases of clinically asymp- tomatic pericardial calcification. 5. The early diastolic “dip” during the rapid filling phase. 6. The protodiastolic sound of co ventricular filling and abrupt halt in filling. of the right ventricular pressure curve occurs nstrictive pericarditis is produced by rapid ACKNOWLEDGEMENTS Terry, who stimulated his interest in The writer is greatly endebted to Dr. Luther L. es of the study. Miss electrokymography. Dr. Richard G. Oakley assisted in the early stag Clara King gave valuable technical assistance. ADDENDUM Since this manuscript was prepared two more cases of constrictive pericar- ditis have been studied and submitted to decortication with success. Both showed the kymographic pattern described here. Awareness of the characteris- tic pattern as a result of the detailed electrokymographic analyses makes roent- genkymography more informative and electrokymography less essential to the diagnosis. BIBLIOGRAPHY c constrictive pericarditis. I. Some clinical and laboratory 4. McKusicx, V. A.: Chroni observations. Bull. Johns Hopkins Hosp. 90: 3, 1952. 2. Gituick, F..G., AND Reynoips, W. F:: Clinical application of electrokymography. California Medicine. 70: 407, 1949. 3. GILLIcK, F. G., AND REYNOLDS, W.F.: Electrokymographic obs pericarditis. Radiology. 35: 77, 1950. 4. BLOOMFIELD, R. A., LAUSON, H. D., CouRNAND, W., JR: Recording, of right heart pressures in norm: chronic pulmonary disease and various types of car Invest. 25: 739, 1946. 5. HaNnsEN, ANDERS TYBJOERG: Pressure Measure: hagen, Teknisk Forlag, 1949. P. 190. 6. Hansen, A. T., ESKILDSEN, P., AND GOTZSCHE, auricle and the right ventricle in constrictive pericarditis. C ervations in constrictive A., Breen, E. S., AND RICHARDS, D. al subjects and in patients with diocirculatory disease. J. Clin. ments in the Human Organism. Copen- R.: Pressure curves from the right irculation, 3: 88, 1951. CHRONIC CONSTRICTIVE PERICARDITIS . 41 “4: FENRY, G. C., AND Boone, B. R.: Electrok i - utilizing the roentgenoscope. Am. J. Rete eh 7 neart motion 3, MorGaN, RUSSELL H.: Electrokymography. Am. J. Med. Sc 218: 587, 1949 9, Boone, B.R., EEEINGER G. F., anD GILLIck, F. G.: Electrokymography of ‘the heart an great vessels: principles and application. Ann. Int. Med. 31: 1030, 1949 = 10. Lewis, J. L., Jz., anp Terry, L. L.: Electrokymography—an appraisal if h clinical status. Ann. Int. Med. 32: 36, 1950 oF he Present t1. Lower, R. Tractatus de Corde. Leyden Verbek cial de. ; , 1728, p. 109. Quot j Classic Descriptions of Disease. Charles C Thomas, Sprin eda, oe a in a p06 , geld, 1945. Third edition, 12, Cuevers, N.: Observations on the disea f i Tie Rep, 7: 387, 1842. ses of the orifice and valves of the aorta. Guy’s 13, STUMPF, PLEIKaRT: Roenigenkymo ; graphische B Caan, Thieme, 1996. ip é Bewegungslehre Innerer Organe. Leipzig, 4, Kay, C. F. Woops, J. W., JR., ZmnssErR, H LCF, ; .» JR; , H. F., JR., AND MALVERN, B : van of the electrokymographic method for measurement of dismeton ‘chan a e aorta and pulmonary artery during circulatory disturban Cli oe 238, 1949. ce. J. Clin. Invest. 28: 15. Zinsser, H. F., Jr:, Kay, C. F., anp B : : ’ , , . T., Ad ENJAMIN. . : studies in recording fidelity. Circulation 2 197 Toso" ——_ 16. Lyons, R. H., anp BurweE t, C. S.: Ind , : . oe ? ? en d i i i i i eviearaitig, Brit. Heart J. 8: 33 ous changes in the circulation in constrictive 17, Rogsster, H.: Clinical Roentgenology of | LER, genology of th Springld, Ul, 1943. P. 374 gv of the Cardiovascular System. Charles C Thomas, 18. Woop, F. C., Jounson, J., SCHNAB ,t , Js EL, T. G., JR., Kuo, P. K., a The diastolic heart beat. Read at meeting of the Assoc. of Am “vhye Meet Si 19. Buatock, A., personal communication ala alae aa 20. BERNER, FRIEDRICH: Kymo i i i , : graphic stud i iti i Chinmie 194: 460, 1930, p udies of calcific pericarditis. Archiv fiir Klinische 21. Katz, L. N.: The role played i ; yed by the ventricul: j i i An, J. Phoricl, O54 549, 1920. ricular relaxation process in filling the ventricle. 22. Corron, F. S.: Does the ventricl i ion i sore 17a, 1954 icle exert a suction action in diastole? Am. J. Physiol. 23. ScarporoucH, W. R., McKusic »W.R., K, V. A., AND BAKER, B. M : i i Pm ann Constnichve pericarditis. Bull. Johns Hopkins Hosp 00: bo. | . Pau, O., i tive per; : oe 'ASTLEMAN, B., AND WHITE, P. D.: Chronic constrictive pericarditis: < cases. Arm J. Med. Se. 216: 361, 1948. Sa study . Brine, R. J. x oy 7 aera Ra AND r 'ALHOLT, W.: An estimation of the residual volume eo i i Hesse J, 42: 483, 1951. normal and diseased human hearts in vivo. Am.