Phasic Analysis of Cardiac Cycle on the Basis of. Apex Cardiogram, Phonocardiogram and Carotid Tracing. Vesselin I. ORESHKOV, M.D.

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1 Phasic Analysis of Cardiac Cycle on the Basis of Polygraphic Tracing Apex Cardiogram, Phonocardiogram and Carotid Tracing SUMMARY Vesselin I. ORESHKOV, M.D.* (1) By the use of polygraphic tracing including apex cardiogram, phonocardiogram and indirect carotid tracing, an almost full and precise phasic analysis of the cardiac cycle may be obtained. (2) New methods for the measurement of the ejection period and mechanical systole are presented. Additional Indexing Words: Isovolumic contraction time Initial phase of ventricular contraction Pressure elevation time Ejection period Mechanical systole Protodiastole Isovolumic relaxation time Rapid ventricular filling Slow ventricular filling Active ventricular filling T HE phases of the cardiac cycle and their relationships have been increasingly used in modern cardiology. Cardiac catheterization is not applicable to the measurement of the phases of the cardiac cycle in everyday medical practice. Indirect methods are mainly used for this purpose. But the usual polygraphic tracing including electrocardiogram, phonocardiogram and indirect carotid tracing is not sufficient in this respect. If the apex cardiogram is included and simultaneously recorded with the above mentioned curves, an almost full phasic analysis of the cardiac cycle may be obtained. As is known the apex cardiogram is reliable in timing left-sided events in the cardiac cycle9) which was confirmed by correlating the low-frequency apical vibrations of the apex cardiogram with hemodynamic events within the left heart.10),20) MATERIAL AND METHODS Forty normal subjects (19 women and 21 men) were studied. They ranged in age from 14 to 54 years (average age 28 years). Lead II of the electrocardiogram (ECG), an indirect carotid tracing (CT) from the right carotid artery, a left ventricular apex cardiogram (ACG) and a medium frequency phonocardiogram (PCG) were recorded simultaneously with the person reclining in the left lateral decubitus in apnea at the end of a normal expiration. The identification of the origin of the ACG (left or right apex beat) was based on the configuration of the QRS complex * From the Department of Medicine, Higher Medical Institute, Sofia 31, Bulgaria. Received for publication April 3,

2 Vol. 9 No. 4 ORESHKOV 333 of a precordial lead of the ECG from the point of maximal cardiac impulse. A pulse wave condenser microphone (Boucke-Brecht) for recording CT and ACG, and a crystal microphone for recording heart sounds were used. The microphones were connected to a direct-writing multichannel recorder (Hellige, Model 9400/6). The records were taken at a paper speed of 50mm./sec.; for the purpose of illustration, a few tracings were recorded at a faster speed of 100mm./sec. PHASIC ANALYSIS OF CARDIA CYCLE Systolic Phases: The isovolumic contraction time (C-E interval) was measured by means of a method presented in a previous report of the author:17) from the onset of the systolic wave in the ACG (point C; C from contraction20)) to the onset of the CT minus the delay time of the central pulse wave (from the beginning of the aortic component Fig. 1. Phases of cardiac cycle: IVC=isovolumic contraction (C-E interval); IPC=initial phase of contraction (C-1 interval); PET=pressure elevation time (1-E interval); EP=ejection period (E-D interval); PD=protodiastole (D-2 interval); IVR=isovolumic relaxation (2-0 interval). ECG (H)=electrocardiogram (lead II); CT=carotid tracing; ACG=left ventricular apex cardiogram; C point=onset of ventricular contraction; E point =onset of ejection; D point=end of ejection; O point=opening of the mitral valve; DT=delay time of the central pulse wave; PCG-MF=phonocardiogram-medium frequency; 1=first heart sound; 2=second heart sound. See text.

3 334 PHASIC ANALYSIS OF CARDIAC CYCLE Jap. Heart J. J uly, 1968 of the second heart sound to the carotid incisura) (Fig. 1). Apex cardiography is an excellent method for recording the onset of the movements of the heart in systole, i.e. the onset of the isovolumic contraction. There is an exceedingly close correlation between the initial abrupt rise of ACG and the initial rise of the left ventricular pressure curve.20) The E point (E from ejection) marks the opening of the aortic valve, i.e. the end of the isovolumic contraction time and the beginning of the ejection period. The E point usually precedes the peak of the systolic wave in the ACG.16) Support for this conception of the author can be found in the works of Dallocchio et al.10) (1965) and Tavel et al.20) (1965) who later confirmed it by the use of ACG and intracardiac pressure curves simultaneously recorded. The isovolumic contraction time may be divided into two phases: (a) initial phase of ventricular contraction (C-1 interval): from the C point to the onset of the main vibrations of the first mitral sound;9),18),19),21) and (b) ventricular pressure elevation time (1-E interval): from the onset of the main vibrations of the first mitral sound to the E point. Holldack and Wolf12) calculate this same interval as a difference between tension period and transformation time. The ejection period (E-D interval) was measured from the E point to the point where the systolic plateau of the apex cardiographic curve distinctly changes its direction downward (D point) (Fig. 1). The interval between the D point and the second heart sound represents the protodiastole.19) Therefore, the D point marks the end of the ejection period. The mechanical systole (C-D interval) comprises the isovolumic contraction time and the ejection period: from the C point to the D point. Diastolic Phases: The protodiastole (D-2 interval) represents the time interval between the end Fig. 2. Phases of cardiac cycle (continued): RF=rapid filling phase (O-F interval); SF=slow filling phase (F-A interval); A=atrial wave representing active ventricular filling produced by atrial contraction. SW=systolic wave on the ACG; F point=end of rapid ventricular filling. See Fig. 1 for explanation of remaining symbols.

4 Vol. 9 ORESHKOV 335 No. 4 of the ventricular ejection and the closure of the aortic valve.22) It was measured from the D point to the aortic component of the second heart sound (Fig. 1). The isovolumic relaxation time (2-0 or 2-OS interval) is represented by the time interval between the onset of the main vibrations of the aortic component of the second heart sound and the O point in the ACG14) (Fig. 1). Recently there has been some evidence that the O point occurs near the time of mitral valve opening, but especially in mitral stenosis does not correlate as well with the crossing of left ventricular and left atrial pressures as does the mitral opening snap (OS).20) That is why the mitral OS, when present, may be preferred. The phase of rapid ventricular filling (O-F interval) was measured from the O point to the F point in the ACG4),9),10),15) (Fig. 2). This is the so-called rapid filling wave on the ACG. Where there is an OS (PCG), this latter may be used instead of the O point (ACG). The phase of slow ventricular filling (F-A interval) corresponds to the slow filling wave on the ACG which starts at the end of the rapid filling wave (F point) and ends at the beginning of the 'A' wave4),9),15) (Fig. 2). In patients with atrial fibrillation this phase ends at the onset of the systolic wave (F-C interval). The phase of active ventricular filling (due to atrial contraction) is presented by the atrial wave ('A' wave) in the ACG4),9),10),15) (Fig 2). Intersystole: When the P-Q interval is prolonged, there may appear an interval, called intersystole, between the end of the 'A' wave and the onset of the following systolic wave (A-C interval). RESULTS The results are given in Table I. It may be seen that the values of the various phases of the cardiac cycle measured by means of the polygraphic tracing are close to those obtained by a direct method. At the same time it should be borne in mind that in timing left-sided events in the cardiac cycle, heart catheterization is not always more reliable. For instance, there is no abrupt change in the rate of ventricular filling on the ventricular pressure curve at the time of the peak of the rapid filling wave on the ACG.20) The influence of the heart rate on the phases of cardiac cycle may be seen in Table II. As is expected this influence is most conspicuous on the slow ventricular filling phase. Heart rate, too, significantly decreases, the mechanical systole and the ejection period respectively. The isovolumic relaxation time also varies inversely with heart rate. The same tendency appears in the duration of the rapid ventricular filling phase. Such a relationship is not clearly evident in the other phases of cardiac cycle.

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6 Vol. 9 No. 4 ORESHKOV 337 DISCUSSION When measuring isovolumic contraction time from the onset of the main vibrations of the first mitral sound to the onset of the CT minus the delay time of the central pulse wave,13) the initial phase of ventricular contraction (before the closing of the A-V valves) is not included. Neither is this phase included when isovolumic contraction time is calculated as a difference between the mechanical systole (1 sound-2 sound) and the ejection period (from the onset of the CT to the carotid incisura).5),11) By the use of these methods, only the ventricular pressure elevation time is determined. When measuring isovolumic contraction time from the onset of the systolic wave (ACG) to its peak2)-4),21) the interval read is longer than the real one because the opening of the aortic valve (E point), as mentioned above, precedes the peak of the systolic wave. This subject was discussed in detail in a previous work of the author.17) The isovolumic contraction time measured from the first mitral sound to the beginning of the CT,19) in fact, represents the ventricular pressure elevation time plus the delay time of the carotid pulse wave. The initial phase of ventricular contraction (C-1 interval) has its own diagnostic significance. The author showed that this interval was a more reliable index in the diagnosis of mitral stenosis than the transformation time (Q-1 interval).18) The ejection period measured from the onset of the CT to the carotid incisura5),6),12) includes the protodiastole during which there is no ejection. The real time of ejection corresponds to the E-D interval. The period of maximal ventricular ejection and the period of slow ventricular ejection cannot be determined exactly by the use of ACG or CT. The C-D time interval on the ACG completely corresponds to the mechanical systole determined on the basis of cardiac catheterization. The mechanical systole measured from the first to the second heart sound includes the protodiastole which belongs to the diastole,23) while the initial phase of ventricular contraction (before the closing of the A-V valves) is not included. It should be emphasized that it is much more difficult or even impossible to determine the onset of the protodiastole by the use of the CT only (Fig. 1). The ACG makes possible the isovolumic relaxation time to be measured (2-0 interval) in the absence of an OS. The values of the 2-0 interval obtained in this study-mean (70-130) }15.8msec.-correspond to those obtained by the same method by other authors: Coulshed and Epstein9) (1963)-mean 101 (71-150)msec.; Benchimol and Ellis5) (1967)-mean 103 (50-140) }22msec. These values are bigger than the duration of the iso-

7 338 PHASIC ANALYSIS OF CARDIAC CYCLE Jap. Heart J. July, 1968 volumic relaxation time measured by cardiac catheterization (on the average by 20msec.).1),7),23) It should be emphasized that the O point corresponds to the direct hemodynamic consequence of mitral opening rather than to the opening itself.5) Therefore, it is to be expected that the O point should follow mitral opening. This error, because it is systematic and so small, should not restrict the clinical applicability of the 2-0 interval.5) According to Dallocchio et al.10) (1965), the ACG provides much more detailed information and appears to be much superior for the identification of the elements of ventricular diastole than the left intraventricular pressure curve. Apex cardiography is the only simple indirect method of assessing diastolic events on the left side of the heart.9) The influence of the heart rate on the phases of cardiac cycle is a problem for itself. It will not be discussed here. REFERENCES 1. Arevalo, F. and Sakamoto, T.: Am. Heart J. 67: 651, Benchimol, A., Dimond, E. G., and Carson, J.: Am. Heart J. 61: 485, Benchimol, A. and Dimond, E. G.: Brit. Heart J. 24: 581, Benchimol, A. and Dimond, E. G.: Am. J. Cardiol. 12: 368, Benchimol, A. and Ellis, J. G.: Am. J. Cardiol. 19: 196, Blumberger, K. and Meiners, S.: Cardiology, vol. 2 (edited by A. A. Luisada), McGraw-Hill, New York, p , Braunwald, E., Moscovitz, H. L., Amram, S. S., Lasser, R. P., Sapin, S.O., Himmelstein, A., Ravitch, M. M., and Gordon, A.J.: J. Appl. Physiol. 8: 309, Braunwald, E., Fishman, A. P., and Cournand, A.: Circulat. Res. 4: 100, Coulshed, N. and Epstein, E.: Brit. Heart J. 25: 697, Dallocchio, M., Bricaud, H., Drouet, B., Bonativa, J.-P., and Broustet, P.: Arch. Mal. Coeur 58: 1078, Frank, M. and Kinlaw, W.: Am. J. Cardiol. 10: 800, Holldack, K. and Wolf, D.: Herzschall-Fibel, Thieme, Stuttgart, p. 11, Jezek, V.: Cardiologia (Basel) 43: 298, Legler, J. F., Benchimol, A., and Dimond, E. G.: Brit. Heart J. 25: 246, Martinez-Lopez, J. I.: Sth. med. J. (Bgham, Ala) 58: 1197, Oresbkov, V.: Vatr. bol. (Sofia) 4: 223, Oreshkov, V.: Cardiologia (Basel) 47: 315, Oreshkov, V.: Brit. Heart J. 29: 778, Tafur, E., Cohen, L. S., and Levine, H. D.: Circulation 30: 381, Tavel, M. E., Campbell, R. W., Feigenbaum, H., and Steinmetz, E. F.: Brit. Heart J. 27: 829, Warembourg, H. and Ducloux, G.: Arch. Mal. Coeur 56: 1359, Wiggers, C. J.: Circulatory dynamics. Physiologic studies (in Russian), Publishing house for foreign literature, Moscow, pp. 76, 79, Wiggers, C. J.: Physiology in health and disease, Lee and Febiger, Philadelphia, p. 608, 1944.