Showing papers on "Cardiac cycle published in 1968"
TL;DR: Marked respiratory velocity variations with inspiratory increases occurred during and after exercise, and reduction of flow velocity in abdominal breathing and the Muller maneuver is consistent with the formation of a local area of inferior vena caval collapse at the diaphragm.
Abstract: The velocity of flow and pressure in the venae cavae of four normal conscious subjects was studied. Velocity was measured with a catheter-tip electromagnetic transducer. The effects of respiration, Valsalva and Muller maneuvers, coughing, and exercise were studied. Caval blood velocities during breath holding showed marked cardiac pulsations, being maximal at the time of ventricular systole and minimal or reversed at atrial systole. Peak velocities during ventricular systole ranged from 30 to 45 cm/sec in the inferior, and from 10 to 35 cm/sec in the superior, vena cava. A second diastolic forward flow velocity ranged from 36 to 76% of the systolic peak. During inspiration, velocity transiently increased. Reduction of flow velocity in abdominal breathing and the Muller maneuver is consistent with the formation of a local area of inferior vena caval collapse at the diaphragm. During the Valsalva maneuver, abrupt reduction in caval flow was seen that persisted throughout the strain. There was immediate overshoot when the strain was released. Coughing produced a reduction of flow velocity with backflow in the superior vena cava. In leg exercise, inferior caval flow velocity rose immediately, and it remained high during recovery. Marked respiratory velocity variations with inspiratory increases occurred during and after exercise.
202 citations
TL;DR: These studies indicated that the major left-to-right shunt and pressure gradient occurred over an interval encompassing late ventricular systole and early diastole, and there was augmentation of the left- to- right shunt during atrial contraction.
Abstract: This study was conducted to determine the instantaneous pressure-flow relationships across secundum atrial septal defects. Simultaneous right and left atrial pressures and the pressure difference (determined with an analog computer) were recorded with matched catheter systems. Biplane cineangiocardiography was used to evaluate the timing of the shunts in various phases of the cardiac cycle. These studies indicated that the major left-to-right shunt and pressure gradient occurred over an interval encompassing late ventricular systole and early diastole. Also, there was augmentation of the left-to-right shunt during atrial contraction. Minute right-to-left shunting and pressure gradients occurred at two times in the cardiac cycle: (1) with the onset of ventricular contraction; and (2) during early ventricular diastole (heart rate, 80 to 100 beats/min). Detection of systemic right-to-left shunts by dye curves was enhanced by relatively slow heart rates (prolonged diastasis) which allowed the shunted blood to...
140 citations
TL;DR: Intravascular pressures, distributions of blood oxygen, dye-dilution curves, cineradiography, and electromagnetic flowmeters in major vessels suggest a highly directional flow of systemic and pulmonary venous blood through reptilian hearts.
Abstract: Intravascular pressures, distributions of blood oxygen, dye-dilution curves, cineradiography, and electromagnetic flowmeters in major vessels suggest a highly directional flow oE systemic and pulmonary venous blood through reptilian hearts. The lacertilian right aortic arch contains blood from the pulmonary, and the left from the pulmonary or sometimes both pulmonary and systemic veins. Traces made of the pressure and blood flow show that the lacertilian and chelonian cava venosum and pulmonale are functionally distinct. Atrioventricular valves probably prevent regurgitation during ventricular systole and form an obstruction between the cava arteriosum and venosum during ventricular filling. The muscular ridge approaches the ventral ventricular wall at systole forming a functional ventricular septum. Low pulmonary vascular resistance favors pulmonary ejection before systemic. In Pseudemys the balance between pulmonary and systemic resistance causes a left-to-right shunt during respiration and a right-to-left shunt during diving; the latter probably reduces the expenditure of cardiac energy during hypoxia. Pressure traces and cineradiography indicate separation of systemic and pulmonary venous returns in alligators. The left ventricle perfuses both aortic arches and the right the pulmonary arch. Right ventricular pressure may exceed pulmonary pressure during ejection suggesting an impedance in the pulmonary outflow tract. Pulmonary resistance in crocodilians may increase during diving, instituting a right-to-left shunt.
83 citations
TL;DR: The electron microscopic structure of heart muscle and the ultrastructural basis of cardiac contraction have been reviewed and the importance of sarcomere dispersion and "fiber slippage," which may lead to disordered ventricular function, have been discussed.
Abstract: The electron microscopic structure of heart muscle and the ultrastructural basis of cardiac contraction have been reviewed. The relation between muscle length and developed tension has been explained in terms of the structure of the sarcomere, which is the basic unit of contraction. Using the derived length-tension curve of the sarcomere, developed tension has been attributed to the overlap of thick and thin filaments within the sarcomere, lending support to the "sliding" mechanism in heart muscle. It has been shown that initial sarcomere length is a function of ventricular filling pressure and that this relation explains the normal limits of the heart as a pump, including: (1) the Starling mechanism whereby increased diastolic volume (EDV) engenders an increased stroke volume (SV), (2) the upper limits to ventricular filling pressure and volume, and (3) the normal range to the ventricular ejection fraction (SV/EDV). Further, ultrastructure helps to define the processes which occur with acute and chronic ventricular dilatation. In this regard, the importance of sarcomere dispersion and "fiber slippage," which may lead to disordered ventricular function, have been discussed.
58 citations
TL;DR: The isovolumetric contraction period of the left ventricle was measured atraumatically by six different cardiographic methods in 50 normal young men and the earliest inception of left ventricular systole appears to be the beginning of isometric contraction.
42 citations
TL;DR: Epicardial electrodes were chronically implanted on the surface of atria and ventricles in 60 patients at the time of open-heart surgery and the safety and ease of implantation enable them to be used routinely for diagnostic and therapeutic application in all patients undergoing open- heart surgery.
Abstract: Epicardial electrodes were chronically implanted on the surface of atria and ventricles in 60 patients at the time of open-heart surgery. Eighteen patients developed bigeminy or multiple premature ventricular contractions associated with slow heart rates in the immediate postoperative period. The ectopic ventricular activity was abolished by pacing the atria or ventricles faster than the spontaneous cardiac rate. In seven patients, low cardiac output associated with low heart rates was improved by pacing at more optimal rates. When feasible, atrial pacing is preferred to ventricular pacing to utilize atrial systole to improve ventricular filling and increase cardiac output. The safety and ease of implantation of these electrodes enable them to be used routinely for diagnostic and therapeutic application in all patients undergoing open-heart surgery.
39 citations
TL;DR: Cardiac and aortic pressures were recorded after stellate ganglionectomy and vagotomy, and the mitral valve was not effectively closed by atrial systoles that were not followed by normally sequenced ventricular systole.
Abstract: Cardiac and aortic pressures were recorded after stellate ganglionectomy and vagotomy. Acute heart block was produced by injecting the atrioventricular node, and atrial and ventricular systoles were controlled electronically to occur independently or in any desired relationship. Angiocardiograms recorded on video tape after injections of 4 ml 69% Renovist into the left ventricle were analyzed with a videodensitometer able to detect small refluxes of contrast medium into the left atrium and correlate them with phases of the cardiac cycle. When ventricular driving was temporarily suspended but atrial driving continued, pressure records indicated mitral valve closure after each atrial systole, but reflux of contrast medium into the atrium occurred after each systole not followed by a normally sequenced ventricular systole. Driving with a 2: 1 atrioventricular stimulation resulted in reflux, with the alternate atrial contraction dissociated from ventricular systole. Thus, the mitral valve was not effectively closed by atrial systoles that were not followed by normally sequenced ventricular systoles.
37 citations
TL;DR: The time of occurrence of rapid movements of the heart valves was detected with the ultrasonic Doppler method in cases of hypertension with or without myocardial involvements, congestive heart failure resulting from these conditions, and aortic regugitation, and then changes in each phase in a cardiac cycle under these conditions were studied.
31 citations
TL;DR: The continuous pressure-volume relationships throughout the cardiac cycle were evaluated in children with tetralogy of Fallot, isolated ventricular septal defect, and patent ductus arteriosus, with marked increase in stroke volume.
Abstract: The continuous pressure-volume relationships throughout the cardiac cycle were evaluated in children with tetralogy of Fallot, isolated ventricular septal defect, and patent ductus arteriosus. Biplane cineangiocardiography and simultaneous left ventricular pressures were utilized for data acquisition. Normal pressure-volume loops demonstrated only small changes in left ventricular volume during the isovolumic periods. In tetralogy of Fallot, there was a decrease in left ventricular volume during the interval of the "isovolumic" contraction with 12 to 43% of the total stroke volume being ejected during this phase. A decrease in left ventricular volume during this time was also found in large ventricular septal defects; however, volume changes during this interval were minimal in those patients judged to have small defects. With large left-to-right shunts of comparable magnitude, the relative area of the pressure-volume loop was greater in patent ductus arteriosus as compared with ventricular defects. Both ...
27 citations
TL;DR: Effects of experimental ventricular pacing on ventricular function were studied on 5 anesthetized dogs and it was revealed that the bulge developing in mid-systole reached its maximum size at the end of the ventricular ejection period and disappeared during the period of isovolumic relaxation of theventricle.
Abstract: Effects of experimental ventricular pacing on ventricular function were studied on 5 anesthetized dogs. The heart was stimulated by bipolar electrodes placed at the right atrial appendage and the epicardium at the apex or base of the left ventricle. Cineangiocardiographic analysis of the left ventricle was made and the sequential change in the shape of the left ventricle during ventricular contraction was compared among each of three stimulation sites.A systolic expansion of the localized area of electrical stimulation was observed during stimulation at the base as well as at the apex of the left ventricle, but not during right atrial stimulation, and it was consistently reproducible in any given experiment. Correlation of individual cine frames to simultaneously recorded ventricular pressures revealed that the bulge developing in mid-systole reached its maximum size at the end of the ventricular ejection period and disappeared during the period of isovolumic relaxation of the ventricle.
20 citations
TL;DR: Atrial and ventricular systoles were controlled electronically in non-thoracotomized dogs with acute heart block and Videodensitometer analysis of selective left ventricular videoangiograms showed presystolic reflux to the left atrium during regular cardiac driving with long atrial-ventricular intervals.
Abstract: Atrial and ventricular systoles were controlled electronically in non-thoracotomized dogs with acute heart block. Videodensitometer analysis of selective left ventricular videoangiograms showed presystolic reflux to the left atrium during regular cardiac driving with long atrial-ventricular intervals. Atriogenic mitral valve closure after relatively isolated atrial systole was not as effective as closure either by optimally timed atrial and ventricular systoles or by ventricular systole alone.
TL;DR: The results indicate that ventricular injury is dependent (in part) on the contractile state of the ventricular myocardium at impact.
01 Mar 1968
TL;DR: Pulsatile characteristics of blood flow in major pulmonary veins were determined from chronically implanted dogs and five distinct positive flow maxima or waves are proposed to describe the variety of waveforms observed over a cardiac cycle.
Abstract: : Pulsatile characteristics of blood flow in major pulmonary veins were determined from chronically implanted dogs. From these data, five distinct positive flow maxima or waves are proposed to describe the variety of waveforms observed over a cardiac cycle. These five waves appear to change in amplitude and relative position among dogs, with respiration and under physiologic stress, and thereby permit an explanation of the different patterns that have been reported by other investigators. The general appearance of the flow waveform is particularly sensitive to heart rate. Four of the five flow waves are attributed to left heart action. One wave corresponds to the effects of right ventricular ejection transmitted through the pulmonary vascular bed. Limited data from respiration maneuvers and pharmacologic intervention provide changing waveform patterns which support these conclusions. Dissimilar waveforms were recorded simultaneously from some pairs of lobar veins. (Author)
TL;DR: Impedance plots were obtained before and after corrective surgery in patients with a variety of left ventricular outflow tract and aortic valve lesions, providing quantitative measurement of flow resistance throughout the cardiac cycle in a variety-of- cardiac and great vessel lesions.
Abstract: A hydraulic fluid impedance plot is produced by plotting instantaneous differential pressure against phasic blood flow across a vascular segment. This simple plot quantitatively and compactly describes the changes in flow resistance (impedance) throughout the entire cardiac cycle. Impedance plots were obtained before and after corrective surgery in patients with a variety of left ventricular outflow tract and aortic valve lesions. Although present techniques are still limited, impedance plots now provide quantitative measurement of flow resistance throughout the cardiac cycle in a variety of cardiac and great vessel lesions.
TL;DR: Correlation between these parameters has established a relationship between two Doppler signals and fetal cardiac cycle, which probably occurs during isometric contraction phase of the fetal ventricles.
TL;DR: Evaluation of data is simplified and valvular gradients can be measured with greater precision when the wide variability in duration of cardiac cycle and intracardiac pressures usually present during atrial fibrillation are abolished by ventricular pacing.
Abstract: A technic to simplify hemodynamic evaluation during atrial fibrillation by right ventricular pacing is described. The hemodynamic data obtained at cardiac catheterization during atrial fibrillation with and without right ventricular pacing were compared in 3 cases. Evaluation of data is simplified and valvular gradients can be measured with greater precision when the wide variability in duration of cardiac cycle and intracardiac pressures usually present during atrial fibrillation are abolished by ventricular pacing.
TL;DR: Evidence was presented that the added indicator cleared the right atrium within one cardiac cycle, under the conditions of the experiment, and a mathematical model was constructed to express the relationship of indicator concentration in pulmonary arterial blood to the indicator injection rate, the residual fraction of right ventricular blood, and the heart rate.
TL;DR: High speed color motion pictures of the heart in 10 dogs have shown rapid phasic color changes in the right atrium which alternate between red and cyan with each cardiac cycle, although the cause of these color changes is not yet known.
Abstract: SummaryHigh speed color motion pictures of the heart in 10 dogs have shown rapid phasic color changes in the right atrium which alternate between red and cyan with each cardiac cycle. Frame by frame measurement of color at 10 msec intervals throughout one cardiac cycle in one dog has shown a major red peak beginning approximately 195 msec after the onset of the P wave. Although the cause of these color changes is not yet known, they may result from phasic changes in coronary arterial flow through the atrial wall.
TL;DR: Wherein the ventricular diastolic interval is not disturbed, as seen in nodal rhythm with atrioventricular (A-V) dissociation or in complete A-V block, the amplitude of the arterial pulse is significantly influenced by the presence or absence of effective atrial systole.
Abstract: Atrial systole significantly contributes to the arterial pulse. In ectopic beats, without preceding atrial systole, the arterial pressure pulse is significantly diminished. Wherein the ventricular diastolic interval is not disturbed, as seen in nodal rhythm with atrioventricular (A-V) dissociation or in complete A-V block, the amplitude of the arterial pulse is significantly influenced by the presence or absence of effective atrial systole.