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Showing papers on "Cardiac cycle published in 1974"


Journal ArticleDOI
TL;DR: Observations indicate that, in patients with diffuse myocardial involvement, isovolumic indices are not reliable for detecting depressedMyocardial function and that ejection phase contractile indices appear to offer a preferable mode for assessing myocardIAL function in the basal state.
Abstract: Indices derived from both the isovolumic and ejection phases of left ventricular systole have been advocated as a means of defining the basal level of contractility, but their comparative reliability for separating patients with obvious myocardial disease from a normal population has not been documented Accordingly, indices of myocardial function were measured and compared in 36 patients, 22 with normal and 14 with abnormal ventricular function, using optimal techniques of pressure measurements by cathetertip micromanometry, signal digitizing at 1 msec intervals with averaging of multiple beats, and left ventriculography by biplane cineangiography Isovolumic indices derived from developed pressure (DP), including V max, dP/dt/DP at DP = 5, 10, and 40 mm Hg, demonstrated no sensitivity for identifying depressed myocardial function ( P > 01 in each instance) Using total pressure (TP), V max, peak (dP/dt/TP), and peak dP/dt served to separate the two patient populations from a statistical standpoint ( P < 0001), but individual values in the two groups showed considerable overlap By contrast, the simplified ejection phase velocity indices, mean velocity of circumferential fiber shortening (mean Vcf) and mean normalized systolic ejection rate (MNSER) showed superior sensitivity for identifying normal and abnormal patient groups and manifested minimal overlap of individual values ( P < 0001) These observations indicate that, in patients with diffuse myocardial involvement, isovolumic indices are not reliable for detecting depressed myocardial function and that ejection phase contractile indices appear to offer a preferable mode for assessing myocardial function in the basal state

200 citations


Journal ArticleDOI
TL;DR: Echocardiographic studies of the pulmonary valve obtained in 63 adults showed an oblique position of the valve images in diastole, slow valve opening slopes, sizable posterior displacement of the cusp echoes with atrial systole, and a relatively short right ventricular pre-ejection period.
Abstract: Echocardiographic studies of the pulmonary valve were obtained in 63 adults. Patients with normal pulmonary artery pressure (22 cases) showed an oblique position of the valve images in diastole, slow valve opening slopes (≤ 300 mm/sec), sizable (> 2 mm) posterior displacement of the cusp echoes with atrial systole (`a' dip), and a relatively short right ventricular pre-ejection period. In contrast, pulmonary valves in pulmonary hypertension (mean pressure > 20 mm Hg, 41 cases) appeared straight in diastole with rapid opening slopes (> 350 mm/sec) and prolonged pre-ejection periods (P 40 mm Hg) when uncomplicated by severe right heart failure. In the latter instance rapid valve opening slopes were associated with large `a' dips. Echocardiography appears to ...

171 citations


Journal ArticleDOI
TL;DR: There are significant limitations to the use of the premature atrial stimulation technique for estimating sinoatrial conduction time, and the transition from compensatory to less than compensatory atrial return cycles failed to indicate sinus node capture by an atrial premature depolarization.
Abstract: The premature atrial stimulation technique was investigated as a method of measuring sinoatrial conduction time in the rabbit. Fifteen studies were performed in which intracellular recordings were obtained from a sinus node cell and atrial electrical activity was recorded from the crista terminalis by a surface electrogram. An additional ten studies were performed without microelectrode recordings. Atrial premature depolarizations late in the cardiac cycle produced compensatory atrial return cycles, but earlier premature depolarizations produced less than compensatory return cycles. Compensatory return cycles only occurred with atrial premature depolarizations that failed to capture the sinus node cell. The transition from compensatory to less than compensatory return cycles occurred with late atrial premature depolarizations that failed to capture the sinus node. Therefore, the transition from compensatory to less than compensatory atrial return cycles failed to indicate sinus node capture by an atrial premature depolarization. Although these premature depolarizations were too late to capture the sinus node cell, they still shortened the sinus node and atrial return cycles to make the atrial return cycle less than compensatory. This shortening of the sinus node return cycle was due to a shortening of the sinus node action potential by electrotonic interaction between sinus node and adjacent cells during repolarization. The electrotonic effect resulted in shortening of the sinus node action potential and accounted for the poor correlation ( r = 0.64) between estimated and measured values of sinoatrial conduction time. These data indicate that there are significant limitations to the use of the premature atrial stimulation technique for estimating sinoatrial conduction time.

86 citations


Journal ArticleDOI
TL;DR: awareness of the existence of the hangout interval and its hemodynamic determinants offers a reasonable mechanism to explain the audible expiratory splitting of the second heart sound found in patients with idiopathic dilatation of the pulmonary artery following atrial septal defect repair and in one additional patient studied with mild valvular pulmonic stenosis.
Abstract: The sound pressure correlates of the second heart sound were studied in 22 patients during diagnostic cardiac catheterization. Simultaneous right ventricular and pulmonary artery pressures were recorded with equisensitive catheter-tip micromanometers together with the external phonocardiogram and ECG. In 12 patients having normal pulmonary vascular resistance (group 1), pulmonic closure sound was coincident with the incisura of the pulmonary artery pressure curve which in turn was separated from the right ventricular pressure trace by an interval denoted hangout. The duration of this interval varied (33-89 msec), was independent of pulmonary artery pressure or resistance and was felt to be primarily a reflection of the capacitance of the pulmonary vascular tree. The absolute value of this interval during inspiration was very similar to the splitting interval and, when subtracted from the Q-P 2 interval, the remaining interval (QRV) was almost identical to the Q-A 2 interval, indicating that the actual duration of right and left ventricular systole is nearly equal. Awareness of the existence of the hangout interval and its hemodynamic determinants offers a reasonable mechanism to explain the audible expiratory splitting of the second heart sound found in patients with idiopathic dilatation of the pulmonary artery following atrial septal defect repair and in one additional patient studied with mild valvular pulmonic stenosis. In nine patients with elevated pulmonary vascular resistance approaching systemic levels (group 2), the absolute value of the hangout interval was markedly reduced (15-28 msec) consistent with the decrease in capacitance of the pulmonary vascular bed and the increased pulmonary vascular resistance known to occur in pulmonary hypertension. In those patients where the duration of right and left ventricular systole were nearly equal, narrow splitting of the second heart sound was present. In those patients where selective prolongation of right ventricular systole occurred, the narrow hangout interval persisted, but the splitting interval was prolonged proportionate to the increased duration of right ventricular systole.

82 citations


Journal ArticleDOI
TL;DR: Left ventricular performance was compared during normal and delayed left ventricular activation in a patient with intermittent left bundle branch block, and LBBB depressed left Ventricular performance, probably by causing a less synchronous ventricular contraction.

69 citations


Journal ArticleDOI
TL;DR: The most prominent influence on beat-to-beat alterations in left ventricular performance in these patients appeared to be mediated through the Frank-Starling mechanism.
Abstract: Sixty-six cardiac cycles in 10 patients with valvular heart disease and depressed left ventricular performance who had atrial fibrillation were analysed by measurement of arterial pressure, R-R interval and the cineangiographically derived end-diastolic volume, ejection fraction, and mean rate of circumferential fibre shortening at the minor left ventricular equator. For each beat the independent influence on left ventricular performance of variations in end-diastolic volume, aortic diastolic pressure and abrupt charges in cycle length was assessed. The most prominent influence on beat-to-beat alterations in left ventricular performance in these patients appeared to be mediated through the Frank-Starling mechanism.

66 citations


Journal ArticleDOI
TL;DR: The temporal relationship of flow pulses in the pulmonary artery, capillaries, and veins was investigated in 10 chronic dog preparations with pulsed ultrasonic flowmeters and a nitrous oxide-body plethysmograph for capillary flow.
Abstract: The temporal relationship of flow pulses in the pulmonary artery, capillaries, and veins was investigated in 10 chronic dog preparations with pulsed ultrasonic flowmeters and a nitrous oxide-body plethysmograph for capillary flow. Implanted pressure transducers in the left atrium provided reference to the conventional atrial pulses: A, C, X-descent, V, and Y-descent. Left atrial contraction produced an A-wave pressure transient followed by retrograde flow up the veins. The C-pressure pulse occasionally produced a minimal trough in the venous flow pattern. Early in ventricular systole, X-descent in left atrial pressure preceded a venous flow pulse of modest amplitude, which began prior to the onset of the pulse of capillary flow. On average, right ventricular ejection was followed in 37 msec by the major flow pulse in the capillaries, which in turn was followed 68 msec later by the onset of venous flow. This venous flow pulse was simultaneous with a rise in left atrial pressure, the V-wave. With the onset of diastole, the Y-descent in atrial pressure preceded a major venous flow pulse. With accelerated heart rate, separation of the V and Y venous flow pulses was lost, and a monophasic pulse was found.

62 citations


Journal ArticleDOI
TL;DR: It was concluded that atrioventricular valveclosure is a necessary event in the production of S1 and that at least in some individuals tricuspid valve closure is related to its second high frequency component.
Abstract: Eight subjects with complete atrioventricular heart block were studied with simultaneous echocardiography and phonocardiography to investigate the role of the mitral and tricuspid valves in the genesis of the first heart sound (S1). Mitral valve motion was studied in all cases and tricuspid patterns in three. At P-R intervals less than 0.20 sec, mitral leaflet closure was completed by ventricular systole. Below P-R values of 0.20 sec there was an inverse relationship between P-R and S1 amplitude. With P-R between 0.20 and 0.50 sec atrial systole closed the mitral valve without recordable sound. Beyond P-R intervals of 0.50 sec there was reopening of the mitral valve and secondary closure initiated by ventricular systole which was coincident with S1. The extent of mitral leaflet separation at the onset of ventricular systole correlated with S1 amplitude. Pre-ejection period was not related to S1 intensity. Over a wide range of P-R intervals in two subjects with a split S1, tricuspid valve closure was simul...

60 citations


Journal ArticleDOI
TL;DR: In moderate to severe pulmonary stenosis, the exaggerated leaflet motion after atrial systole probably reflects increased right ventricular end-diastolic pressure and force of atrial contraction which, in the face of a normal or reduced pulmonary arterial pressure, produces a positive gradient across the valve in end- diastole.
Abstract: Echocardiographic tracings of the pulmonary valve were examined in 14 patients with isolated pulmonary stenosis, 20 normal subjects, 26 patients with pulmonary hypertension, 10 patients with a left to right shunt and 28 patients with various forms of heart disease other than pulmonary stenosis. Because of the plane of pulmonary valve motion and the angle of the ultrasonic beam, usually the echoes from only one posterior pulmonary leaflet were recorded. In normal patients atrial systole caused slight posterior motion of the pulmonary valve leaflet in late diastole (average 3, range 0 to 7 mm). The degree of valvular motion after atrial systole (the a wave) increased with inspiration. The position of the leaflet at the onset of ventricular systole varied with the depth of the a wave and the length of the P-R interval, but in the normal subjects the leaflet always returned to a base line or closed position at some time during the respiratory cycle. In 10 patients with moderate or severe pulmonary stenosis (gradient 50 to 142 mm Hg) the depth of the a wave increased markedly (average 10, range 8 to 13 mm). In patients with a gradient of more than 65 mm Hg (8 of 10) the leaflet never returned to a base line or closed position before ventricular systole. In three of four patients with mild pulmonary stenosis (gradient less than 50 mm Hg) and all patients with a left to right shunt or heart disease without pulmonary involvement the a wave was within the normal range. In 25 of 26 patients with pulmonary hypertension no a wave was present. In moderate to severe pulmonary stenosis, the exaggerated leaflet motion after atrial systole probably reflects increased right ventricular end-diastolic pressure and force of atrial contraction which, in the face of a normal or reduced pulmonary arterial pressure, produces a positive gradient across the valve in end-diastole.

60 citations



Journal ArticleDOI
TL;DR: Afferent discharges were recorded from the left cardiac sympathetic nerve or the third sympathetic ramus communicans of anaesthetized cats of anaesthetic cats.
Abstract: 1. Afferent discharges were recorded from the left cardiac sympathetic nerve or the third sympathetic ramus communicans of anaesthetized cats. Twenty-one single units with baroreceptor activity were obtained. 2. The receptors of each unit were localized to the extrapulmonary part of the pulmonary artery, determined by direct mechanical probing of the wall of the pulmonary artery after death of the animals. Conduction velocity of the fibres ranged from 2·5 to 15·7 m/sec. 3. Afferent discharges occurred irregularly under artificial ventilation. The impulse activity was increased when pulmonary arterial pressure was raised by an intravenous infusion of Locke solution, or by occlusion of lung roots, and decreased by bleeding the animal from the femoral artery. 4. Above a threshold pressure, discharges occurred synchronously with the systolic pressure pulse in the pulmonary artery. A progressive further rise in pressure did not produce an increase in the number of impulses per heart beat. Occlusion of lung roots initially elicited a burst of discharges but the number of impulses for each cardiac cycle gradually decreased. 5. The receptors responded to repetitive mechanical stimuli up to a frequency of 10/sec, but failed to respond to stimuli delivered at 20/sec. 6. The results provide further evidence for the presence of afferent fibres in the cardiac sympathetic nerve. These afferent fibres are likely to provide the spinal cord with specific information only on transient changes in pulmonary arterial pressure.

Journal ArticleDOI
TL;DR: A step-by-step approach to cardiac diagnosis utilizing a chest X-ray and echocardiography is described and used to study a normal infant and six infant patients with angiocardiographically-proven complex congenital heart malformations.
Abstract: A step-by-step approach to cardiac diagnosis utilizing a chest X-ray and echocardiography is described and used to study a normal infant and six infant patients with angiocardiographically-proven complex congenital heart malformations The heart is divided into three major anatomical segments in order to localize the atrial and ventricular chambers and determine the relationship of the great arteries The atrial chambers are localized by noting the position of the liver on the X-ray The right atrium is on the same side as the liver with few exceptions The ventricular chambers are localized by echocardiographically identifying the tricuspid and mitral valves They are a part of the morphologically right and left ventricles, respectively As a general rule, the atrioventricular valve whose anterior leaflet is continuous with the posterior margin of a semilunar valve is the mitral valve The atrioventricular valve whose anterior leaflet is not continuous with a posterior semilunar valve margin is the tricu

Patent
01 Nov 1974
TL;DR: In this paper, a heart assist device is controlled in a normal mode of operation to counterpulsate with the heart and produce a blood flow waveform corresponding to the flow waveforms of the heart being assisted.
Abstract: A heart assist device is controlled in a normal mode of operation to counterpulsate with the heart and produce a blood flow waveform corresponding to the flow waveform of the heart being assisted. A blood pump in the device is connected serially between the discharge of a heart ventricle and the vascular system, and during the normal mode of operation, the pump is operated to maintain a programmed pressure at the ventricle discharge during systolic cardiac pulsation. A pressure transducer detects the pressure at the ventricle discharge and a hydraulically powered, closed-loop servomechanism controls the displacement of a piston in an expansible chamber receiving the blood from the ventricle, in such a way that programmed pressure is maintained in the chamber. Means are provided for recording the piston displacement as a function of time during ventricular systole. During diastole, the piston motion is reversed, and servo-controlled to duplicate the recorded displacement waveform while the piston contracts the chamber volume and expels blood into the vascular system. In this way the output blood from waveform produced by the pump during diastole is the same as the output flow waveform produced by the ventricle during the previous systole. In the event that the heart beat stops or becomes severely arrhythmic, the device switches to an autonomous mode of operation and a waveform generator in the pump controls provides an ideal blood flow waveform independent of cardiac pulsations.

Journal ArticleDOI
TL;DR: It is concluded that A/H corresponds best to LVDS and is a useful noninvasive measurement of this property of the left ventricle.
Abstract: This study was made to determine whether the A wave of the apexcardiogram (ACG), a reflection of the late diastolic response of the left ventricle to atrial systole, corresponded in a quantifiable way to left ventricular late diastolic stiffness (LVDS). Using a combined ultrasonic and hemodynamic technique, the slope of the late diastolic left ventricular pressure/diameter relationship (ΔP/ΔD) was calculated in 25 patients and used as a measure of effective LVDS. Most patients had valvular heart disease, all were in sinus rhythm and none had regional abnormalities of contraction. An ACG was recorded in all and the ratio of the size of the A wave to the total amplitude of the ACG wave (A/H) was calculated. When A/H was more than 11%, left ventricular hypertrophy (LVH) and the presence of a fourth heart sound were the rule in the group of patients studied. Using A/H as an independent variable, correlation coefficients were obtained for ΔP, ΔD, ΔP/ΔD, left ventricular end diastolic pressure (LVEDP), and left...

Journal ArticleDOI
TL;DR: The relationship of the form of ventricular anodal strength-interval curves to the types of arrhythmias induced by trains of low-intensity stimuli was studied in 16 dogs and it was found that these relationships may participate in the initiation and the maintenance of arrHythmias.
Abstract: The relationship of the form of ventricular anodal strength-interval curves to the types of arrhythmias induced by trains of low-intensity stimuli was studied in 16 dogs. Strength-interval curves were determined after basic atrial driven beats and after induced premature ventricular depolarizations. The test stimuli for these determinations were 2-msec anodal square waves delivered in 1-msec decrements during the first half of the cardiac cycle and in 10-msec decrements during the last half of the cycle. At each time step, the stimulus intensity was increased in 5-µamp steps until a ventricular response occurred or a level of 1.2 mamp was reached. Three types of strength-interval curves were observed. Each form of the strength-interval curve was associated with a specific type of arrhythmia induced by a train of 50-Hz, 2-msec anodal stimuli of minimum threshold intensity which was applied for periods of up to several minutes. When the minimum threshold in the strength-interval curve following the basic driven beat was lower than the minimum threshold following the induced premature ventricular depolarization, the train of stimuli induced stable ventricular bigeminy. Accelerating ventricular tachycardia followed by ventricular fibrillation resulted if there were deep dips in the strength-interval curves following both the basic driven beats and the premature ventricular depolarizations. When the strength-interval curves following both the basic driven beats and the premature ventricular depolarizations smoothly approached diastolic levels without deep dips or supernormal periods, the train of stimuli caused either occasional premature ventricular depolarizations with long coupling intervals or slow ventricular tachycardia. These relationships may participate in the initiation and the maintenance of arrhythmias.

Journal ArticleDOI
TL;DR: Systolic and diastolic time intervals in 14 cardiac patients with pulsus alternans revealed significant alternation of PEP, IVCT, LVET, ETI, PEPLVET, and carotid dDdt, with better functional values in the strong beats, with greater consistency in the weak beats.


Journal ArticleDOI
TL;DR: It is apparent that hemodynamic measures reflect fundamental characteristics of muscle contraction through which one can derive information pertinent to the contractile properties of heart muscle in approaching the evaluation of the diseased heart.
Abstract: When the physiologist wishes to express the performance of cardiac muscle in quantitative terms, he regularly resorts to three basic parameters, the length, force and time of contraction. He recognizes that in portraying the function of cardiac muscle in these terms he must take into cognizance the initial stretch of the muscle, the load that the muscle is contracting against, the mass of the muscle and the synchrony of the individual muscle fibers comprising the body of the muscle. In physiologic terms he is interested in the preload, the afterload, the synchrony and mass of contracting muscle. When he translates these characteristics of muscle performance into the function of the heart as a whole, the physiologist must resort to common hemodynamic measurements. Thus, the preload of the ventricles is reflected in the enddiastolic pressure and volume, the afterload in measures of aortic resistance and pressure or ventricular systolic force, or both, the length of muscle contraction in the stroke volume expressed relative to the end-diastolic volume, the force of contraction in the pressure-volume changes occurring during systolic contraction, and the time of contraction in the duration of the phases of the cardiac cycle and the time derivatives of the contractile events. It is apparent that hemodynamic measures reflect fundamental characteristics of muscle contraction through which one can derive information pertinent to the contractile properties of heart muscle. In approaching the evaluation of the diseased heart, changes in performance of the cardiac chambers, as reflected in pressure, volume, flow and time alterations, permit one to discriminate the presence, extent and functional effect of cardiovascular disease. Often, a combination of hemodynamic measurements must be obtained to define the presence of cardiac malfunction. Such combinations of hemodynamic measurements allow better definition of cardiac performance than single measures alone. These considerations are pertinent to the application of noninvasive methods in evaluating cardiac performance. It is because noninvasive techniques can reflect hemodynamic events within the cardiac chambers that they are, in fact, useful. Like measures of pressure, volume and flow, modern noninvasive

Journal ArticleDOI
TL;DR: In this paper, the authors discuss normal and abnormal ventricular filling sounds, opening snap, tumor plop, pericardial knock, prosthetic A-V valve click and pacemaker-induced sound.
Abstract: Cardiac diastole usually is acoustically silent even though several hemodynamic events take place in this phase of the cardiac cycle. In some healthy subjects and in many patients with cardiovascular alterations one or more “extra” heart sounds may be heard in diastole, and in them the distinction between normal and abnormal heart sounds must be established. In general, diastolic sounds may be spontaneous in nature or iatrogenic, that is, a consequence of replacement of the atrioventricular (A-V) valve with a caged-poppet prosthesis or a result of pervenous pacemaker implantation. The majority of the sounds emanate from the chambers of the heart. This presentation discusses normal and abnormal ventricular filling sounds, opening snap, “tumor plop,” pericardial knock, prosthetic A-V valve click and pacemaker-induced sound.

Journal ArticleDOI
TL;DR: The decreased discharge during sympathetic stimulation was the result of a decline in left atrial pressure rather than a result of any direct effect on the receptor per se, and the curve for these parameters were not significantly different from each other.
Abstract: Experiments were performed to determine the influence of cardiac sympathetic efferent nerve stimulation on the discharge rate of atrial type B stretch receptors in the anesthetized, open-chest dog. In all experiments, the left stellate ganglion was stimulated following volume expansion. To determine the effects of stellate stimulation, the responses of atrial receptors were observed during the withdrawal of blood in steps following intravascular volume expansion. Stimulation of the stellate ganglion decreased receptor discharge and left atrial pressure in all experiments. A change from a control left atrial pressure of 2.5 cm H2O (in peak left atrial v-wave pressure) resulted in a mean increase in receptor discharge of 6.6 ± 1.4 spikes/cardiac cycle during stellate stimulation; however, a change from a control pressure of 0.0 cm H2O resulted in a mean decrease in receptor discharge of 1.5 ± 1.5 spikes/cardiac cycle. The curves relating the change in atrial receptor discharge to the change in left atrial p...

Journal ArticleDOI
TL;DR: It is postulate that this delayed rapid filling phase of the cardiac cycle is the origin of the filling sound in presystole in the absence of the usual accompanying P wave.

Journal ArticleDOI
TL;DR: The sudden expulsion of the mass from the ventricle to the atrium early in systole represents an in vivo example of the quick release phenomenon.
Abstract: An experimental model of a prolapsing left atrial tumor mass has been utilized In dogs to study the hemodynamic events of the cardiac cycle and the cineangiographic and echocardiographic manifestations of this condition. The characteristic ventricular notch has been correlated with the timing of the expulsion of the simulated tumor mass from the left ventricle to the left atrium. The early notch seen with small simulated tumors delays aortic ejection by 0.02 to 0.03 second and results in abbreviated aortic ejection time and minimal distortion of the E-F slope of anterior mitral leaflet motion in the echocardiogram. Larger masses lead to late ventricular notching, transiently interrupt aortic flow and may displace the anterior mitral leaflet until It impinges on the interventricular septum in mid-diastole and at the onset of systole. A transient systolic Increment of coronary flow is observed after expulsion of the tumor from the left ventricle into the left atrium. There is an echo-free interval immediately after opening of the mitral valve, indicating that tumor motion lags perceptibly behind the initial blood flow through the mitral orifice. The sudden expulsion of the mass from the ventricle to the atrium early in systole represents an in vivo example of the quick release phenomenon.

Journal ArticleDOI
TL;DR: It would appear that transient increases in heart rate induced after AMI reduce myocardial performance in the subsequent period.


Journal ArticleDOI
TL;DR: It was found that the diameter of small vessels normally changes by up to 20% during the cardiac cycle, and the number of small myocardial vessels filled increases when the mean aortic pressure rises by 20 mm Hg, but not when the heart rate doubles.
Abstract: An experimental method of quantitating the functional anatomy of small coronary arteries (0.3–0.1 mm) in regions of the canine myocardium is described. Serial magnification and cine and kine microangiography were optimized by means of a leaf phantom with contrast-filled xylem. It was found that the diameter of small vessels normally changes by up to 20% during the cardiac cycle. The number of small myocardial vessels filled increases when the mean aortic pressure rises by 20 mm Hg, but not when the heart rate doubles.