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Showing papers on "Cardiac cycle published in 1978"


Journal ArticleDOI
TL;DR: Simulated isopotential surface maps during both activation and recovery are in good agreement with data for humans reported in the literature.
Abstract: A digital computer model is presented for the simulation of the body surface electrocardiogram (ECG) during ventricular activation and recovery. The ventricles of the heart are represented in detail by a three-dimensional array of approximately 4000 points which is subdivided into 23 regions. Excitation sequence and cellular action potential data taken from the literature are used to determine the spatial distribution of intracellular potentials at each instant of time during a simulated cardiac cycle. The moment of the single dipole representing each region is determined by summing the spatial gradient of the intracellular potential distribution throughout the region. The resulting set of 23 dipoles is then used to calculate the potentials on the surface of a bounded homogeneous volume conductor with the shape of an adult torso. Simulated isopotential surface maps during both activation and recovery are in good agreement with data for humans reported in the literature.

363 citations


Journal ArticleDOI
TL;DR: The effect of atrialventricular versus ventricular pacing and contraction were studied in seven open‐chest dogs and the right or left ventricular apical areas were consistently superior as ventricular paced sites.
Abstract: The effect of atrialventricular versus ventricular pacing and contraction were studied in seven open-chest dogs. Cardiac output, left ventricular, left atrial, right atrial and pulmonary artery pressures were recorded. The right or left ventricular apical areas were consistently superior as ventricular pacing sites. Appearance of cannon A waves within the pre- or ejection period produced a significant decrease in left ventricular and systemic blood pressure, and cardiac output with a concomitant increase in right atrial, ventricular and pulmonary pressures. Prominent “v” waves were also observed during these periods. Reducing the basic driving cycle length from 400 to 300 msec caused a marlted deterioration of all hemodynamic parameters with the appearance of mechanical alternans. Random VA conduction or ventricular pacing in the presence of com-plete AV and VA heart block appeared to offer a more favorable hemodynamic result than constant 1:1 VA conduction. It is concluded that maintenance of a physiologic AV interval permitting atrial contraction to appear outside of pre- or ejection period of ventricular systole is an important determinant or ventriculor function during cardiac pacing.

134 citations


Patent
24 Nov 1978
TL;DR: In this article, an antiscattering masking frame has alternate parallel slits and bars at equal intervals exposing substantially half the area of presentation of an X-ray sensitive film in alternate, equally spaced area strips during, e.g., diastole.
Abstract: X-ray apparatus and method for producing discrete images of a human organ in fluctuating motion, e.g., the heart and related vessels. Each image is derived at a selected time related to the cardiac cycle. The images are independently presented on respective discrete areas within a common image plane. A source of X-rays irradiates the organ. A physiological synchronizer produces timing signals within the cardiac cycle for controlling the periods of transmission of the X-ray beam through the organ during, for example, end diastole and end systole. An antiscattering, masking frame has alternate parallel slits and bars at equal intervals exposing substantially half the area of presentation of an X-ray sensitive film in alternate, equally spaced area strips during, e.g., diastole. The frame is repositioned in response to a signal from the synchronizer for actuating it relative to the film such that the bars then cover the sensitized areas of the film and expose substantially the remaining half of the film during systole. The image elements are interdigitally juxtaposed to present the diastolic and systolic images in an interlaced pattern. Relative displacements of the organ during a cardiac cycle may be determined from the juxtaposed image elements.

70 citations


Journal ArticleDOI
01 Jul 1978-Chest
TL;DR: These cases illutstrate that this new noninvasive technique may provide sufficient quantitative preoperative detail in patients with left atrial tumors to obivate the risk and expense of caridac catheterization.

68 citations


Journal ArticleDOI
TL;DR: Valve opening and closure times in dogs under varying hemodynamic conditions suggest that in the intact heart alpha, rapid mitral cusp closure at the end of diastole is initiated and completed by ventricular systole alone, and beta, the ventricular isovolumic contraction period might be shorter than assumed.
Abstract: The exact times of mitral valve opening and closure were determined in dogs under varying hemodynamic conditions in 143 cardiac cycles (five experiments). Radiopaque markers had been sutured to the cusps and the valve annulus 7-124 wk before the studies. Valve opening and closure times were correlated with simultaneously obtained high-fidelity intracardiac pressures. Closure of the mitral valve was completed 5-105 ms after the atrial-ventricular pressure crossover; the time interval between the onset of ventricular systole and the instance of complete valve closure varied less (10-40 ms). These observations suggest that in the intact heart alpha, rapid mitral cusp closure at the end of diastole is initiated and completed by ventricular systole alone, and beta, the ventricular isovolumic contraction period might be shorter than assumed. Opening of the valve during ventricular relaxation was characterized by 1) initial separation of the markers placed on the free edges of the cusps, of variable duration, apparently due to alterations in ventricular geometry, and 2) a rapid opening motion which clearly preceded the diastolic pressure crossover by 5-60 ms. This finding would suggest that ventricular isovolumic relaxation might be shorter than generally accepted, although the mechanism of early opening is not adequately explained by the data.

44 citations


Journal ArticleDOI
TL;DR: Echocardiography has the potential to localize pacing catheters which are occasionally difficult radiologically or electrocardiographically and failure to recognize catheter echo patterns may result in errors in eChocardiographic interpretation.
Abstract: Thirty patients with right ventricular (RV) and 15 with coronary sinus (CS) pacing catheters were studied by M-mode echocardiography. RV catheters, detected in 23, appeared as linear echoes in the right ventricle during mitral valve recordings in 12, adjacent or superimposed on the tricuspid valve (TV) in 14, and immediately anterior to aortic root and pulmonary valve echoes in two with a redundant loop in RV outflow. In three with complete heart block, prominent systolic anterior movements of the TV occurred when atrial systole coincided with ventricular systole, probably due to catheter-induced TV "buckling" or exaggerated TV annular motion. Catheter echoes mimicked TV recordings in three, since its motion pattern was similar, although delayed and mimicked prolapsing right atrial myxomas in two because of multilayered complexes behind TV, while reverberations cluttering the left ventricle simulated structural echoes present in that cavity. CS catheters, detected in 14 as linear echoes in the area of atrial septum recorded behind the TV, showed typical small humps in late diastole/early systole. Cross-sectional echocardiography with a mechanical sector scanner demonstrated RV catheters at the RV apex in five of seven patients, while CS catheters were detected near the base of the atrial septum in three of five patients. Echocardiography has the potential to localize pacing catheters which are occasionally difficult radiologically or electrocardiographically. Failure to recognize catheter echo patterns may result in errors in echocardiographic interpretation.

39 citations


Journal ArticleDOI
TL;DR: The findings suggest that the duration, rate, and magnitude of atrial filling and emptying may be, in the intact heart, determined by the movements of the atrioventricular junction.
Abstract: The variations in ventricular–atrial mitral annular position during the cardiac cycle and the simultaneous changes in left atrial silhouette area (obtained by angiography after injections of contrast material into the main pulmonary artery) were investigated in six experiments on intact dogs with chronically implanted intracardiac markers. Frame-by-frame measurements of the angiograms (120 frames/s) were used to determine, under various hemodynamic conditions, the duration, magnitude, and average rate of the mitral annular motion and of the simultaneous changes in left atrial area during atrial filling (ventricular systole) and atrial emptying (early in ventricular diastole). The mitral annulus was seen to move towards the ventricular apex during systole and towards the atrium early in diastole with the duration, average rate, and magnitude of displacement (although varying widely) showing good statistical correlations (P < 0.0005–0.005) with the changes in projected left atrial area. These findings sugge...

26 citations


Journal ArticleDOI
TL;DR: This analysis, which is the first complete analysis of the echocardiogram in the newborn, provides a normal range of septal and ventricular wall dynamics as well as right and left ventricular and left atrial function and has clinical implications in that it may allow early recognition of both congenital and perinatal myocardial disease.
Abstract: Computer analysis of the M-mode echocardiogram in 50 normal newborns provided measurements of wall thicknesses and chamber size and, in addition, assessment of right and left ventricular wall, septal, and cavity dynamics throughout the cardiac cycle. Data obtained with this new technique indicated that (1) right and left ventricular cavity functions are similar in the normal newborn, (2) right and left ventricular cavity filling and emptying vary directly with peak rates of septal and ventricular wall thinning and thickening, respectively, and (3) there is a close time relationship among maximum left atrial dimension, minimum left ventricular dimension, and mitral valve opening. This analysis, which is the first complete analysis of the echocardiogram in the newborn, provides a normal range of septal and ventricular wall dynamics as well as right and left ventricular and left atrial function and has clinical implications in that it may allow early recognition of both congenital and perinatal myocardial disease.

25 citations


Book ChapterDOI
01 Jan 1978
TL;DR: The phenomenon of ‘Gap in A-V Conduction’ was originally described by Moe and associates (559) where a zone within the cardiac cycle was reached where in premature atrial responses no longer conducted to the ventricles.
Abstract: The phenomenon of ‘Gap in A-V Conduction’ was originally described by Moe and associates (559) During experiments designed to evaluate conduction characteristics with the canine heart, it was noted that premature atrial beats evoked progressively earlier in the cardiac cycle conducted to the ventricles with prolonged P-R intervals With decreasing prematurity a zone within the cardiac cycle was reached where in premature atrial responses no longer conducted to the ventricles However, as the atrial responses were made even more premature, conduction resumed Within this context, the term ‘gap in A-V conduction’ as originally used, defined a zone within the cardiac cycle where in premature atrial impulses failed to evoke ventricular responses while atrial beats of greater and lesser prematurity did

23 citations


Journal ArticleDOI
TL;DR: It appears that the "a dip" on the pulmonary valve is influenced by dual mechanisms: pressure differences between the pulmonary artery and the right ventricle in late diastole and the left atrial events, and also reflecting the instantaneous pressure differences across the pulmonary valves following atrial systole.
Abstract: It has been shown that the echographic motion of the posterior aortic wall in diastole is closely related to the underlying left atrial events, possibly due to the anatomical proximity of the two structures. We observed that the pulmonary artery shares a similar close anatomical relationship with the left atrium. The present study in 55 consecutive patients with adequate echocardiographic recordings of the aortic root and the pulmonary valve demonstrates that the diastolic waveforms of the pulmonary valve and the posterior aortic wall are nearly identical in early diastole. The pulmonary valve e-f slope correlated with the posterior aortic wall O-R slope (r = 0.95) and the S2-f interval (second heart sound to f on the pulmonary valve) correlated closely with the S2-R interval (second heart sound to R on the posterior aortic root) (r = 0.94)). No significant correlation was found between the pulmonary valve e-f slope and the pulmonary artery pressures. The presence and amplitude of the maximum "a dip," on the other hand, correlated with the presence of pulmonary hypertension, with some notable exceptions. In addition, the "a dip" on the pulmonary valve and the depth of the A wave on the posterior aortic wall were significantly correlated (r = 0.85). It appears that the "a dip" on the pulmonary valve is influenced by dual mechanisms: pressure differences between the pulmonary artery and the right ventricle in late diastole and the left atrial events. Thus, the early diastolic waveform of the pulmonary valve, like the posterior aortic wall waveform, may primarily reflect underlying left atrial events and is not a measure of pulmonary artery pressure. The late diastolic waveform "a dip" has a dual mechanism, related in part to the underlying left atrial events, and also reflecting the instantaneous pressure differences across the pulmonary valve following atrial systole.

20 citations


Journal Article
TL;DR: GSA is a simple, safe means of evaluating left ventricular ejection fraction and regional wall motion noninvasively, and results were highly reproducible.
Abstract: The efficacy of gated synchronous acquisition (GSA) after cardiac blood pool labelling in assessing left ventricular function (ejection fraction and regional wall motion) was evaluated in 31 patients within 24 hours of contrast left ventricular angiography. With the R-wave of the electrocardiogram as a physiologic marker, radionuclide data recorded into an on-line computer allowed construction of cardiac blood pool images during sequential periods of the cardiac cycle. The images, of high count density, have good spatial resolution and can be viewed repetitively in real time in a cine mode. The ejection fractions calculated from the left ventricular time-activity curves corrected for background activity correlated well with the ejection fractions determined from dimension analysis of the contrast left ventricular angiograms (r = 0.87). The results were highly reproducible (r = 0.97). Results of analysis of left ventricular wall motion were similar with the two types of angiograms in 26 of the 31 subjects. GSA is a simple, safe means of evaluating left ventricular ejection fraction and regional wall motion noninvasively.

Journal ArticleDOI
TL;DR: The observation of SAM in patients without HCM indicates that its presence during single dimensional echocardiography is neither diagnostic nor specific for HCM, LVOT obstruction or mitral regurgitation, and contradicts the assumption that the anterior mitral valve leaflet plays a significant role in the mechanism ofLVOT obstruction.
Abstract: The systolic anterior motion (SAM) of valve structures in the mitral echogram in hypertrophic cardiomyopathy (HCM) has previously been considered to be anterior motion and re-opening of mitral valve leaflets, causing left ventricular outflow tract (LVOT) obstruction and mitral regurgitation. Fifteen patients with HCM underwent cardiac catheterisation and were also examined by M-scan and mechanical real-time B-scan techniques. In all patients SAM was seen during M-scan echocardiography. The mitral valve leaflets were visualised during the entire cardiac cycle during real-time B-scanning without showing any re-opening in systole. Thickened papillary muscles have been observed in 12 patients and prominent chordae tendineae moving in the opposite direction to the anterior mitral valve leaflet in 10 patients. Four patients with SAM did not show mitral regurgitation during left ventricular angiography. In two patients without fixed haemodynamic obstruction, a complete SAM touching the interventricular septum was observed with prolonged apposition in one case. These findings suggest that SAM is due to the motion of chordae tendineae and/or papillary muscles traversing the single dimensional ultrasonic beam in systole, thus producing single linear or multiple spotty echoes within SAM. The mechanism of the upward motion of the subvalvular mitral valve apparatus in systole appears to be due to forceful contraction of the apical left ventricular posterior wall. The observation of SAM in patients without HCM also indicates that its presence during single dimensional echocardiography is neither diagnostic nor specific for HCM, LVOT obstruction or mitral regurgitation, and contradicts the assumption that the anterior mitral valve leaflet plays a significant role in the mechanism of LVOT obstruction. The salient feature of all conditions associated with abnormal mitral subvalvular motion is hyperkinetic contraction of the apical left ventricular posterior wall. Hyperkinetic left ventricular ejection appears to be the main factor in the complex development of an LVOT gradient in hypertrophic cardiomyopathy.

Journal ArticleDOI
TL;DR: Six infants with anomalous connection of the pulmonary veins to the coronary sinus were studied with single crystal echocardiography, and an echo-free space measuring 7 to 9 mm was identified behind the posterior left atrial wall; this space was thought to represent the common pulmonary vein.
Abstract: Six infants with anomalous connection of the pulmonary veins to the coronary sinus were studied with single crystal echocardiography. The posterior left atrial wall echo was identified by its continuity with the left ventricular posterior wall echo during a sweep from the left atrium to the left ventricle. In five of the six infants an echo-free space measuring 7 to 9 mm was identified behind the posterior left atrial wall; this space was thought to represent the common pulmonary vein. In four of these five, and also in the remaining infant, a highly mobile linear echo with a double wave form per cardiac cycle was recorded behind the posterior aortic wall and anterior mitral leaflet echoes. Echocardiographic contrast studies after the injection of saline solution into the coronary sinus disclosed that this additional echo was produced by the anterior wall of the coronary sinus. The anatomic connection of the pulmonary veins were established in each patient with pulmonary cineangiography. In four of the six patients all four pulmonary veins were connected to the coronary sinus by way of a common pulmonary vein; in the remaining two patients three of four pulmonary veins were connected to the coronary sinus, while the left upper lobe pulmonary vein was connected to the left innominate vein. The coronary sinus was greatly enlarged in each patient.

Journal ArticleDOI
TL;DR: The left atrial echocardiogram is an aid in the diagnosis of mitral regurgitation and provides a rough index of the severity of the lesion.
Abstract: The motion of the posterior wall of the normal left atrium has not been studied systematically. The superoposterior portion of the left atrium is adynamic throughout the cardiac cycle, whereas the inferoposterior portion is displaced posteriorly with left atrial filling during ventricular systole. In the present study, the left atrial diameter (LAD), the left atrial systolic motion (LASM) and the left atrial systolic velocity (LASV), were determined in the following groups of patients: 34 normals; eight patients with either coronary artery disease or aortic stenosis; six patients with aortic insufficiency; and three patients with ventricular septal defect. The results obtained were compared to 15 patients with angiographically documented mitral regurgitation. In the last group, the LAD (4.2 +/- .19 cm) and LASV (12.3 +/- 1.23 cm) and LASM (1.2 +/- 0.4 cm) were significantly greater reflecting the early accentuated filling of the left atrium induced by mitral regurgitation. As well, the product of these three parameters was greater in the mitral regurgitation group (63.2 +/- 7.34 cm3/sec) than in the other groups and patients with mild to moderate regurgitation had a significantly lower value than those with moderate to severe regurgitation (45.7 +/- 4.1 vs 78.5 +/- 10.9, P less than 0.02). The left atrial echocardiogram, therefore, is an aid in the diagnosis of mitral regurgitation and provides a rough index of the severity of the lesion.

Journal ArticleDOI
TL;DR: Using a catheter with 2 transducers, one mounted at the tip and one 9 cm proximal to it, enabled transvalval pressure waveforms to be recorded in 8 horses.
Abstract: Using a catheter with 2 transducers, one mounted at the tip and one 9 cm proximal to it, enabled transvalval pressure waveforms to be recorded in 8 horses. A simultaneous electrocardiogram acted as a time base. The changing waveforms produced in the chambers of the heart and great vessels are described and related to the events of the cardiac cycle. The effect of second degree AV block, ectopic beats, a pan diastolic murmur and chronic obstructive pulmonary disease are described.

Journal ArticleDOI
TL;DR: Only after correction of the background radiation is it possible to evaluate the severity of various types of cardiac insufficiency; this can be obtained by integrating the impulse during systole and subtracting this from the impulse rate over the left ventricle during a complete cardiac cycle.
Abstract: During evaluation of cardiac function using 99mTc human serum albumen (functional scintigraphy during contraction of the left ventricle), it is necessary to take account of the background radiation which is derived from the lungs and great vessels overlying the heart. Only after correction of the background radiation is it possible to evaluate the severity of various types of cardiac insufficiency; this can be obtained by integrating the impulse during systole and subtracting this from the impulse rate over the left ventricle during a complete cardiac cycle. Apart from the background correction derived from the systolic-diastolic variation, it is necessary to obtain adequate resolution by examining 100 frames per second, an adequate picture matrix (4-K) in order to obtain adequate spacial resolution and accurate measurements of systole and diastole. The latter should be obtained not from the E.C.G., but directly from the volume curve of the left ventricle as determined by the isotope method.

Journal ArticleDOI
01 Oct 1978-Heart
TL;DR: It is suggested that the failure of anterograde conduction at relatively late atrial coupling intervals was caused by a short AH functional refractoriness produced by the pre-excitation of the lower AV junction by a partial AV nodal bypass.
Abstract: Of 8 patients with the short PR interval, normal QRS complex syndrome studied recently, 3 reported here displayed gaps in anterograde conduction. Atrial premature beats at decreasing coupling intervals conducted with minimal AH prolongation until a zone within the cardiac cycle was reached where conduction failed at a supra-Hisian level. Conduction resumed at earlier atrial coupling intervals and was associated with a sudden increase in the AH interval and the appearance of atrial echo beats with earliest atrial activation on the proximal coronary sinus electrogram. It is suggested that the failure of anterograde conduction at relatively late atrial coupling intervals was caused by a short AH functional refractoriness produced by the pre-excitation of the lower AV junction by a partial AV nodal bypass. Conduction resumed only when early atrial premature beats found the extranodal pathway refractory and were transmitted with decremental delay through the AV node.

Journal ArticleDOI
TL;DR: The recognition of these pressure transients on an otherwise smooth ventricular, aortic, or pulmonary arterial pressure places in proper perspective their role in the production of the second heart sound.
Abstract: Sudden momentary fluctuations of left ventricular, aortic, right ventricular, and pulmonary arterial pressure were noted during isovolumic relaxation of the respective ventricles. The presence of such transients raised questions related to their meaning and significance. The purpose of this report is to emphasize the nonartifactual nature of these pressure transients and to describe their origin and significance in the cardiac cycle. Pressure transients were observed in 31 of 32 patients with normal aortic valves, and in 17 patients with normal pulmonary valves in whom right-sided measurements were made. Such transients, however, were absent on the left ventricular and aortic pressure recordings of three patients with calcific aortic stenosis. These sudden changes in pressure are indicative of momentary compressions and rarefactions of the blood that occur within the ventricles and their respective arterial chambers. Whenever present, pressure transients were noted to occur coincident with the major aortic or pulmonary components of the second sound. Since intraarterial sound pressure is derived from the pressure signal by filtering the low frequencies and amplifying the high frequencies, one can deduce that intraarterial sound pressure is in fact a representation of these pressure changes. The recognition of these pressure transients on an otherwise smooth ventricular, aortic, or pulmonary arterial pressure places in proper perspective their role in the production of the second heart sound.

Journal ArticleDOI
TL;DR: It is indicated that serial echographic evaluation of the interval from tricuspid valve closure to pulmonary valve opening can give an accurate reproducible assessment of right ventricular afterload in many children with congenital heart disease and complete right bundle branch block.
Abstract: The time interval between tricuspid valve closure and pulmonary valve opening, termed the isovolumic contraction time of the right ventricle, was evaluated echographically in 38 normal children and within 24 hours of cardiac catheterization in 53 children with congenital heart disease and normal conduction as assessed with the electrocardiogram. In the 53 patients with congenital heart disease, isovolumic contraction time was strongly influenced by right ventricular afterload, as defined by pulmonary arterial end-diastolic pressure (r = 0.87). It was possible to utilize isovolumic contraction time to separate patients with normal or elevated values for pulmonary arterial end-diastolic pressure. Similar correlations were demonstrated between isovolumic contraction time and mean pulmonary arterial pressure and calculated pulmonary vascular resistance. Evaluation of 15 children with complete right bundle branch block revealed values for isovolumic contraction time that did not significantly differ from those of patients with similar pulmonary arterial end-diastolic pressure but no conduction abnormalities. These findings indicate that serial echographic evaluation of the interval from tricuspid valve closure to pulmonary valve opening can give an accurate reproducible assessment of right ventricular afterload in many children with congenital heart disease and complete right bundle branch block.

Journal ArticleDOI
TL;DR: Interpolating atrial extrasystoles showed that atrial systole influenced the efficacy of capture by a mechanical mechanism and not by an electrotonic mechanism.

Journal Article
TL;DR: "fast-motion" pictures of other body functions are begun, including the cerebral circulation, pulmonary ventilation, biliary excretion, and renal blood flow, compressed into 16 frames per second to improve perception of regional dysfunction, and the degree of certainly of the authors' diagnoses.
Abstract: A significant improvement in cardiovascular nuclear medicine has resulted from imaging the heating ventricles by motion-picture display of the intraventricular distribution of /sup 99m/Tc albumin during 16 phases of the cardiac cycle. We have now begun to make fast-motion pictures of other body functions, including the cerebral circulation, pulmonary ventilation, biliary excretion, and renal blood flow. Data obtained over minutes, hours, or days are compressed into 16 frames per second. These compressed-time images improve our perception of regional dysfunction, and the degree of certainty of our diagnoses. They do so by eliminating the blurring inevitably produced in the usual static images of moving structures, such as the heart, and by revealing small changes in regional function.

Journal ArticleDOI
TL;DR: In atrial fibrillation the length of the cardiac cycle did not affect A,-O interval or mitral valve opening movement duration; however cycle length was clearly related to isovolumic relaxation time, which resulted in a variation in the interval between completion of the mitral valves opening (opening snap) and 0 point.
Abstract: Cardiac events of early diastole were studied in 50 normal subjects and 46 patients with mitral stenosis (MS) by simultaneous recordings of the mitral valve echogram (MVE), phonocardiogram, and apexcardiogram (ACG). Left ventricular isovolumic relaxation time (IRT), measured between A2 and onset of the MVE opening motion, had almost the same values in normals 54 +/- 7 msec, and MS 51 +/- 16 msec. The interval between A2 and the ACG "O" point was approximately double that of IRT: 99 +/- 11 msec in normal subjects, 109 +/- 20 msec in MS. The normal MVE opening motion had a velocity 293 +/- 76 mm/sec and duration 45 +/- 6 msec, values significantly different (P less than 0.001) from 536 +/- 271 mm/sec, 23 +/- 7.5 msec found in MS patients. In atrial fibrillation the length of the cardiac cycle did not affect A2-O interval or mitral valve opening movement duration; however cycle length was clearly related to isovolumic relaxation time. This resulted in a variation in the interval between completion of the mitral valve opening (opening snap) and O point. This interval was longer after a short diastole and vice versa.

Journal ArticleDOI
TL;DR: The occurrence and timing of heart sounds were examined from phonocardiograms taken from the mitral, aortic and tricupsid recording areas in each of 18 horses.
Abstract: The occurrence and timing of heart sounds were examined from phonocardiograms taken from the mitral, aortic and tricupsid recording areas in each of 18 horses. 10 sound events could be identified with each cardiac cycle. Atrial contraction produced up to 3 sound events. The first heart sound consisted of 4 components whereas the second sound was single. Two sound events were associated with the 3rd heart sound in early diastole. The occurrence of third and fourth heart sound components varied between horses and between recording areas. The mitral recording area was considered most satisfactory for routine phonocardiographic studies in horses.

Journal ArticleDOI
TL;DR: The results indicate that the responses of the receptors to atrial systole are mainly dependent upon the state of contraction of atrial muscle and that the differences between systolic and diastolic discharge are mainly due to the high dynamic component of the stretch during atrial contraction.
Abstract: 1. Action potentials were recorded from filaments of the right cervical vagus in anaesthetized, paralysed cats. Right atrial receptors with type A (twelve units) and Intermediate type (two units) patterns of spontaneous discharge were selected and their responses to changes in atrial volume were analysed. 2. Changes in atrial volume of similar magnitude were produced under four different conditions: a, innervated hearts; b, denervated hearts; c, depression of atrial muscle contractility induced after cardiac denervation and d, non-beating hearts. 3. In innervated hearts the systolic discharge of each receptor showed a characteristic response to changes in atrial volume. Cardiac denervation and depression of atrial contractility markedly altered this response in terms of frequency of discharge threshold and 'sensitivity'. 4. During increments in atrial volume all the receptors but one assumed an Intermediate pattern of discharge. The diastolic firing rate was, however, higher for any given atrial pressure, in innervated hearts than under conditions b, c and d. 5. In innervated hearts the response of the receptors to atrial systole was characterized by a higher frequency of discharge and a lower threshold with respect to the responses of the same receptors to atrial filling. These differences were minimized at high atrial volumes and during depression of atrial contractility. 6. The results indicate that the responses of the receptors to atrial systole are mainly dependent upon the state of contraction of atrial muscle and that the differences between systolic and diastolic discharge are mainly due to the high dynamic component of the stretch during atrial contraction.

Journal Article
TL;DR: During rest and exercise, resting and exercise initial transit radionuclide angiocardiograms provide a large amount of important hemodynamic information with little patient risk or discomfort.
Abstract: Evaluation of cardiac function during stress exercise provides important information unavailable from studies performed at rest. A dequate data are difficult to obtain during exercise because of the brief duration of the cardiac cycle, the rapid transit of tracer through the heart, and patient motion during exercise. During rest and exercise, we performed radionuclide angiocardiograms in the erect position on normal subjects and patients with coronary artery disease (CAD). The electrocardiogram (ECG) was telemetered and the blood pressure was monitored at regular intervals. A prior treadmill exercise test in all subjects with CAD had documented the heart rate-blood pressure (HR-BP) product at which ischemic myocardial changes occurred on ECG. A bicycle ergometer provided a gradually increasing work load from 200 kilopond meters/min to 700 kpm/min to achieve 80% of the maximal HR-BP product achieved during treadmill testing. Cardiac chamber wall motion and volume changes during individual cardiac contractions were assessed at heart rates greater than 200 beats/min. When properly performed, resting and exercise initial transit radionuclide angiocardiograms provide a large amount of important hemodynamic information with little patient risk or discomfort.

Journal ArticleDOI
TL;DR: The data indicate that, as coronary obstruction increases, the strength of the resting cardiac contraction diminishes, and if the heart of any patient is beating strongly, the presence of severe coronary heart disease can be ruled out.

Journal ArticleDOI
TL;DR: The changes produced by acute pericardial tamponade were examined and the myocardial contractility was not impaired, indicating that the vicious cycle of diminished venoatrial gradient→decreased cardiac output→attenuated effect of ventricular systole on atrial filling, and so forth.
Abstract: The changes produced by acute pericardial tamponade were examined. Tamponade produced the expected hemodynamic alteration; namely, depression on cardiac output, left ventricular pressure and LV dp/dt and elevation of right atrial and intrapericardial pressures. The mechanism of the hemodynamic disturbances was that the elevation of the intrapericardial pressure produced a negative atrial transmural pressure and disturbed atrial and ventricle filling producing the vicious cycle: diminished venoatrial gradient leads to decreased cardiac output leads to attenuated effect of ventricular systole on atrial filling, and so forth. The myocardial contractility was not impaired in cardiac tamponade.

Journal Article
TL;DR: Diastolic determinants revealed in this investigation are the mechanical properties of the myocardium, the state variables of pressure and volume, and the control variables of wall thickness and cavity size.
Abstract: This study deals with the development of a computer program to predict instantaneous left ventricular complicance, as defined by the tangent modulus E, throughout diastole. Diastole is divided into discrete time intervals according to the major events which occur: the start of isovolumic relaxation (aortic valve closure), mitral valve opening, the point of minimum left ventricular pressure, the junction of the rapid and slow filling phases, the start of atrial systole, and the peak of the 'a' wave. Each interval is separated into subintervals. Over each subinterval two mechanisms are assumed to operate: myocardial relaxation or contraction producing a pressure change without an accompanying volume change, followed by explansion of the left ventricle at constant pressure. Although these mechanisms occur simultaneously in the intact heart, they are treated sequentially in a multistage computer program that employs the finite element technique to determine the displacements within a thick-walled ellipsoidal shell. The smaller the time interval between successive stages, the closer is the approximation to the actual continous process of myocardial relaxation, contraction, and distension. Diastolic determinants revealed in this investigation are the mechanical properties of the myocardium, the state variables of pressure and volume, and the control variables of wall thickness and cavity size. In isovolumic relaxation, the myocardium relaxes and the ventricular wall thickens to reduce intracavitary pressure. The relaxation process continues and intraventricular pressure falls to a minimum (0-point) while ventricular volume increases after mitral valve opening. In the succeeding phases, excluding atrial systole, ventricular filling pursues, the properties of the myocardium change, there is an increase in tone (possibly due to myocardial contraction), the wall thins and intraventricular pressure rises. Computer prediction shows that at the start of diastole the tangent modulus is approximately 6 times the enddiastolic value, and is nearly 0 at the onset of the slow filling phase. Tangant modulus is a useful index by which to distinguish normal from abnormal patients provided the characteristics of E as a function of time are recognized and compared throughout diastole.

Journal ArticleDOI
TL;DR: The instantaneous flow (ordinate) -volume (abscissa) relationship showed a loop which rotated in a counterclockwise direction accompanied by rapid downslopes during early diastole in groups I and III, and the steepness of the early diastsolic downslope was markedly decreased in groups II and IV.
Abstract: Cineangiograms of 20 patients were analyzed with a computer to calculate instantaneous left ventricular volume and the rate of volume change (dV/dt, flow) for a cardiac cycle. Patients were divided into four groups : group I-normal, group II-mitral stenosis, group III-left ventricular volume overload, and group IV-coronary artery disease. The instantaneous flow (ordinate) -volume (abscissa) relationship showed a loop which rotated in a counterclockwise direction accompanied by rapid downslopes during early diastole in groups I and III. The steepness of the early diastolic downslope was markedly decreased in groups II and IV. In order to evaluate the findings numerically, flow at the early 20% of diastolic volume change (F20), F20 corrected with peak diastolic flow (F20/Fd) and F20 corrected with peak systolic flow (F20/Fs) were measured. F20/Fs and F20/Fd were significantly lower in groups II and IV than in groups I and III. On the other hand, stiffness constant obtained during later diastole stayed within normal limits in groups I and II, but the index was increased in groups III and IV. Possible mechanism for the decreased flow during early diastole, i.e., delayed relaxation during early diastole in groups II and IV, and dissociation between early diastolic relaxation and the stiffness constant obtained during later diastole in groups II and III are discussed.

Book ChapterDOI
01 Jan 1978
TL;DR: The value of the echocardiogram can be considerably increased if a simple computing technique is used, and transverse left ventricular dimension, measured as the distance between the septum and posterior wall endocardium, is displayed continuously throughout the cardiac cycle.
Abstract: Echocardiography may be used to study patients after mitral valve surgery in two separate ways. The first of these, direct observation of the prosthesis1 or homograft2, has been valuable in determining its normal appearance and, in the case of mechanical prostheses, in detecting abnormalities of movement caused by degeneration or thrombosis. However, it is an approach with limitations, since records of this type may be totally normal in spite of severe malfunction. We have therefore found it more informative to direct our attention not primarily at the prosthesis, but at the effects of the prosthesis or homograft on the pattern of left ventricular wall movement during filling. Although direct inspection of the echocardiogram may give useful information, particularly in the presence of mitral paraprosthetic regurgitation3, the value of the method can be considerably increased if a simple computing technique is used, and transverse left ventricular dimension, measured as the distance between the septum and posterior wall endocardium, is displayed continuously throughout the cardiac cycle.