scispace - formally typeset
Search or ask a question

Showing papers on "Cardiac cycle published in 1989"


Journal ArticleDOI
TL;DR: In subjects with normal relaxation, increasing chamber stiffness was associated with an enhanced peak early filling velocity and volume and decreased filling during atrial systole, differs strikingly from the proposed influence of chamber stiffness on diastolic filling postulated by several researchers.

296 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the response to endothelin of isolated atrial and ventricular trabeculae from failing human hearts obtained at transplant, and found that the increased developed tension was associated with increased atrial systolic activity.

222 citations


Journal ArticleDOI
TL;DR: The dynamic twist-radial shortening relationship throughout the cardiac cycle in six in situ canine left ventricles is determined, suggesting that models of chamber mechanics that incorporate twisting motion need to account for the matrix surrounding the muscles in addition to the shortening and lengthening of the muscle fibers.
Abstract: Cardiac models have proposed tight coupling between the systolic twisting motion of the left ventricle about its longitudinal axis and muscle shortening. Whether a similar relationship holds during...

116 citations


Journal ArticleDOI
TL;DR: In this paper, a noninvasive and noncontact technique based on the principle of laser speckle interferometry has been developed to record the cardiac displacements observed on the chest wall.
Abstract: A noninvasive and noncontact technique based on the principle of laser speckle interferometry has been developed to record the cardiac displacements observed on the chest wall. These displacements are then reconstructed in the form of three-dimensional plots, during the P, QRS and T-waves of the ECG. A comparison of these patterns shows that the mechanical activity of each region varies significantly during these phases of cardiac cycle. As these displacements depend on the clinical status of the heart, its use with a cardiac patient shows the functional changes of the affected regions in the form of alteration of these patterns.

83 citations


Patent
23 Oct 1989
TL;DR: In this article, the authors proposed a dual-chamber pacemaker with variable V-A delay based on detection of multiple criteria before lengthening the VA delay period, such as stimulating the ventricle at a maximum ventricular rate, and an atrial event must be sensed in a relative atrial refractory period.
Abstract: A dual chamber pacemaker with variable V-A delay based on detection of multiple criteria before lengthening the V-A delay period. Before the V-A delay period can be extended, the pacemaker must be stimulating the ventricle at a maximum ventricular rate, and an atrial event must be sensed in a relative atrial refractory period. During this interval the pacemaker would not respond to an atrial event that was sensed, but the occurrence of the event would be detected. To optimize a ventricular blanking period, in each cardiac cycle, the energy level of the atrial output pulse and the sensitivity of the ventricular sense amplifier are sampled. Based on these dynamic parameters, the duration of the ventricle blanking period is adjusted for each cycle so that a minimum ventricular blanking period can be maintained without cross-talk.

79 citations


Patent
31 Mar 1989
TL;DR: Improved cardiocirculatory assistance is provided to a patient by detecting the onset of ventricular ejection in the cardiac cycle of the patient and selectively increasing intrathoracic pressure in relative phase.
Abstract: Improved cardiocirculatory assistance is provided to a patient by detecting the onset of ventricular ejection in the cardiac cycle of the patient and selectively increasing intrathoracic pressure of the patient in relative phase with respect to the onset of ventricular ejection. Cardiocirculatory output may be observed by a cardiac output monitor (66), while the relative phase of the increase in intrathoracic pressure with respect to the onset of ventricular ejection is adjusted for maximum cardiac output under the control of microcomputer (12). Output pressure line (62) is used to interface system (10) to the patient. The patient interface may include apparatus for supplying high frequency respiration pulses in synchronism with the cardiac cycle. In one embodiment, the pulses are used to inflate a bladder in contact with the thorax.

77 citations


Journal ArticleDOI
TL;DR: It was determined that sampling sequentially end diastole yielded the most precise estimates (i.e., exhibiting minimum variability within a cycle) of the vessel measures, and randomly within the cycle was best.
Abstract: Most computer methods that quantify coronary artery disease from angiograms are designed to analyze frames recorded during the end-diastolic portion of the cardiac cycle. The purpose of this study was to determine if end diastole is the best portion of the cardiac cycle to sample, or if other sampling schemes produce more precise and/or reproducible estimates of coronary disease. 20 cinecoronary angiograms were selected at random from a controlled clinical trial testing the effects of plasma lipid lowering on atherosclerosis. Sampling schemes included sequential and random sampling of two to five frames within the complete cardiac cycle, systole, and diastole. Three vessel measures and percent stenosis were evaluated for each sampling scheme. From the sampling experiment, it was determined that sampling sequentially end diastole yielded the most precise estimates (i.e., exhibiting minimum variability within a cycle) of the vessel measures. With regard to reproducibility (i.e., similar values across cycles), sampling randomly within the cycle was best. Overall, the average diameter of a vessel segment was the most precise and the most reproducible of the measures. Sample size calculations are given for each of these measures under the best sampling scheme.

63 citations


Journal ArticleDOI
TL;DR: The results indicate that microstructural consideration offer a realistic representation of the left ventricle mechanics.
Abstract: A model of left ventricular function is developed based on morphological characteristics of the myocardial tissue. The passive response of the three-dimensional collagen network and the active contribution of the muscle fibers are integrated to yield the overall response of the left ventricle which is considered to be a thick wall cylinder. The deformation field and the distributions of stress and pressure are determined at each point in the cardiac cycle by numerically solving three equations of equilibrium. Simulated results in terms of the ventricular deformation during ejection and isovolumic cycles are shown to be in good qualitative agreement with experimental data. It is shown that the collagen network in the heart has considerable effect on the pressure-volume loops. The particular pattern of spatial orientation of the collagen determines the ventricular recoil properties in early diastole. The material properties (myocardial stiffness and contractility) are shown to affect both the pressure-volume loop and the deformation pattern of the ventricle. The results indicate that microstructural consideration offer a realistic representation of the left ventricle mechanics.

61 citations


Journal ArticleDOI
TL;DR: Because of the ease with which Doppler echocardiographic measurements of transmitral flow during early diastole (E velocity) and atrial systole (A velocity) can be used to calculate the E/A ratio as a single index of diastolic performance, this method has become most popular for clinical detection of left ventricular diastolics dysfunction.

57 citations


Journal ArticleDOI
TL;DR: In conclusion, gated perfusion imaging with Tc-99m MIBI, provides useful functional information as an adjunct to perfusion Imaging.
Abstract: Left ventricular function is an important prognostic indicator in patients with coronary artery disease. We have assessed a method of providing this information as an adjunct to myocardial perfusion imaging using Tc-99m MIBI (2-methoxy-2-methyl-isopropyl-1-isonitrile). Two separate studies, at rest and during exercise, were performed following an injection of 400-600 M Bq of Tc-99m MIBI in 62 patients. Cardiac gating permitted excellent myocardial edge definition during the cardiac cycle. Radionuclide fractional shortening (RFS) was calculated from the anteroposterior (AP) and the septum to lateral wall (SL) axes in diastole and systole. Results were compared with echocardiographic fractional shortening (EFS) and the ejection fraction (EF) obtained from the gated equilibrium blood pool using Tc-99m-labelled red blood cells. The RFS in the AP axis correlated closely with echocardiographic FS (r = 0.89, P less than 0.001). The RFS in both axes was averaged to provide a global RFS. Global RFS correlated closely with LV radionuclide EF (r = 0.83, P less than 0.001). Inter- and intra-observer reproducibility studies have shown a variability for the procedure of less than 10%. In conclusion, gated perfusion imaging with Tc-99m MIBI, provides useful functional information as an adjunct to perfusion imaging.

55 citations


Journal ArticleDOI
TL;DR: These experiments show a complex LAo flow pattern; an initial small anterograde flow in the early systole is reversed to a backflow at midsystole and a second flow pulse corresponds to a pressure peak ("foramen spike") in the LAo pressure trace.
Abstract: We report for the first time the flow events corresponding to the pressure patterns in the left and right aorta (LAo and RAo) during the cardiac cycle in the caiman (Caiman crocodylus ssp). These experiments show a complex LAo flow pattern; an initial small anterograde flow in the early systole is reversed to a backflow at midsystole. At the end of systole there is again a small anterograde flow. This second flow pulse corresponds to a pressure peak ("foramen spike") in the LAo pressure trace. The observed pattern is compatible with the view that the foramen Panizzae is obstructed by the medial cusp of the RAo valve during part of the systole. LAo pressure remains normally above right ventricular pressure throughout the cardiac cycle and there is thus no contribution to LAo flow from the right ventricle. The net flow in the LAo normally equals the flow through the foramen Panizzae and is very small compared with the systemic flow in the RAo.

Journal ArticleDOI
TL;DR: It is hypothesized that the mechanism responsible for the positive effect of ejection is length-dependent activation via the larger volume of a beat that ejects compared to one held isovolumic at end-systolic volume.
Abstract: We studied the effect of ejection on end-systolic pressure in isolated heart preparations. Ejecting beats were compared with isovolumic beats having the same volume as at end systole. While holding end-systolic volume constant, various stroke volumes, including negative stroke volumes (volume injected during systole), were imposed using a predetermined volume command. After switching contraction mode between ejecting and isovolumic, we measured the immediate and steady changes in end-systolic pressure. In the first isovolumic beat after switching from steady-state ejecting beats, the change in end-systolic pressure was variable, depending on the stroke volume. The end-systolic pressure of the ejecting beat exceeded that of the isovolumic beat on average by up to 18 mm Hg with small stroke volume, but the ejecting end-systolic pressure became lower than isovolumic with either large stroke volume (stroke volume/end-systolic volume less than 0.96) or with negative stroke volume. During the transient phase following a switch from ejecting to isovolumic, the end-systolic pressure gradually decreased to a steady state. Consequently, even in steady state, ejecting end-systolic pressure exceeded isovolumic pressure over a significant range of stroke volume (stroke volume/end-systolic volume less than 1.18). After returning contraction mode from isovolumic back to ejecting, we observed responses that were a mirror image. These results indicated that in addition to negative uncoupling effect, ejection exerts positive effects on ventricular end-systolic pressure that are manifest both quickly and gradually. We hypothesized that the mechanism responsible for the positive effect is length-dependent activation via the larger volume (both at the initiation of contraction and averaged over a cardiac cycle) of a beat that ejects compared to one held isovolumic at end-systolic volume. The results with volume injection were consonant with this concept.

Patent
11 Aug 1989
TL;DR: In this article, a conditioning pulse trigger is used to generate a conditioning inversion or saturation pulse at a time selected in accordance with the predicted R-wave (40 n-1 ) of one cardiac cycle.
Abstract: A cardiac monitor (62, 64) monitors the cardiac cycles of a patient in an examination region (10). Each cardiac cycle includes an R-wave (40) at the beginning of the end-diastole. A conditioning pulse trigger (74) enables a preconditioning pulse control (34) to generate a conditioning pulse (42) at a time selected in accordance with the R-wave (40 n-1 ) of one cardiac cycle. More specifically, an R-wave predictor (72) predicts when the next R-wave (40 n ) will occur and the conditioning pulse trigger enables the application of the conditioning pulse (42 n ) a selected duration before the next predicted R-wave (40 n ). An imaging sequence trigger (78) enables an image sequence controller (24) to start an imaging sequence in an imaging window (44 n ) in conjunction with the R-wave (40 n ). Preferably, the imaging sequence starts immediately with the R-wave (40 n ) such that the end-diastole stage of the heart is imaged. In this manner, a conditioning pulse, such as an inversion pulse or a saturation pulse, is applied in one cardiac cycle to affect the imaging sequence in the next cardiac cycle. The application of the preconditioning pulse is timed such that the longitudinal magnetization of the blood (54) is near zero (56) during the imaging sequence while the transverse magnetization of cardiac tissue (52) has substantially recovered by the imaging sequence.

Journal ArticleDOI
TL;DR: Active atrial transport (atrial systole) progressively increases its contribution to overall transmitral blood flow with increasing heart rate during mild exercise, mainly mediated by an increase in flow velocity which is related to increased atrial contractility.
Abstract: 1. The change in the relative contribution of the early passive and later active phases of transmitral flow to left ventricular filling was studied using Doppler echocardiography in ten normal male subjects during mild exercise. 2. The peak velocity of passive flow increased during exercise by a mean of 16% whereas peak velocity of active flow increased by a mean of 89%. Hence the ratio of the peak velocities decreased in a linear fashion with a correlation coefficient of r = -0.95. 3. The ratio of the Doppler-derived velocity-time integrals (equivalent to the ratio of flow) of the two phases of transmitral flow also showed a significant negative linear correlation of r = -0.97. 4. Active atrial transport (atrial systole) progressively increases its contribution to overall transmitral blood flow with increasing heart rate during mild exercise. This effect is mainly mediated by an increase in flow velocity which is related to increased atrial contractility.

Journal ArticleDOI
TL;DR: Myocardial gated tomoscintigraphy with hexakis-(2 methoxy-isobutyl-isonitrile) labelled with 99Tcm, is more suitable to resolve precisely the size of myocardial infarct than nongated 201T1 tomoscintsigraphy.
Abstract: Myocardial gated tomoscintigraphy with hexakis-(2 methoxy-isobutyl-isonitrile) labelled with 99Tcm, is more suitable to resolve precisely the size of myocardial infarct than nongated 201Tl tomoscintigraphy. Gated tomography gives short axis slices at eight points in the cardiac cycle. A quantitative method to analyse heart wall activity and its motion is proposed. In two groups of patients, one with inferior infarct and the other with anterior infarct, the time-activity curves show a maximum in systole for healthy regions and a flattened curve in akinetic regions. Gated tomoscintigraphy assesses more accurately the size of the injured regions because there is no averaging between systolic and diastolic activity as in 201Tl tomoscintigraphy. This method should permit a better follow-up of patients with myocardial infarct.

Book ChapterDOI
TL;DR: Variation in the size of the cerebral ventricles during the cardiac cycle suggests that the choroid plexus may play a greater role as a source of CSF pulsation that currently is acknowledged.
Abstract: CSF pulsation suggests variation in the size of the cerebral ventricles during the cardiac cycle. The arterial blood flow and venous outflow are two major components that contribute to the variation. High-resolution MR imaging with cardiac gating provides sharp delineation of the cerebral ventricles with clear boundaries. Subtle changes in the size of the ventricles during the cardiac cycle are measurable with high precision and accuracy by using a sophisticated automated edge-detection algorithm. In 12 normal individuals, the cerebral ventricles were examined, and the size of the lateral ventricles showed a 10–20% change during the cardiac cycle. The pattern is complex but similar in appearance to the intracranial pressure pulse waveform. The variation suggests that the choroid plexus may play a greater role as a source of CSF pulsation than currently acknowledged.

Journal ArticleDOI
TL;DR: Myocardial contrast echocardiography demonstrates that coronary blood flow is primarily subendocardial in distribution during diastole and subepicardial during systole.
Abstract: This study was performed to examine the transmural (endocardial vs. epicardial) heterogeneity of myocardial blood flow during the cardiac cycle (systole vs. diastole). Twenty-four contrast echocardiographic injections were performed in seven open-chest anesthetized dogs either into left anterior descending or circumflex coronary artery or into the aortic root. Two-dimensional echocardiography in short-axis view was performed and was digitized off-line into a 256 x 256 pixel matrix with 256 gray levels/pixel. All end-diastolic and end-systolic frames before and to peak contrast were analyzed. A region of interest corresponding to the most intensely opacified myocardial segment was traced, the mean videodensity measured, and the frame of initial contrast appearance detected. The region of interest was divided into three equal parallel layers corresponding to the endocardial, midcardial, and epicardial myocardium. When the echocardiographic contrast effect initially appeared in diastole, the increment in videodensity was greater for the endocardium (131 +/- 48%) than for the epicardium (71 +/- 37% of the increment in videodensity of the entire wall) (p less than 0.05). This inhomogeneity subsequently disappeared in the following end-systolic frame. When the initial echocardiographic contrast effect appeared in systole, intensity was higher in epicardium (136 +/- 83%) than in endocardium (60 +/- 60%) (p less than 0.05). However, in the following diastole, intensity was not significantly different for the two layers. Thus, myocardial contrast echocardiography demonstrates that coronary blood flow is primarily subendocardial in distribution during diastole and subepicardial during systole.

Journal ArticleDOI
01 Feb 1989-Heart
TL;DR: Gallop sounds seem to be closely related to changes in ventricular inflow velocity, and thus to the effects of forces acting on blood flow, and are responsible for sudden deceleration of flow during rapid ventricular filling.
Abstract: To investigate the relation between changes in left ventricular inflow velocity and the timing of third and fourth heart sounds, simultaneous phonocardiograms and continuous wave Doppler traces were recorded in 48 patients (aged 17-78) with heart disease and in 21 normal children. The onset of the first vibration of the third heart sound coincided with peak left ventricular inflow blood velocity to within 5 ms in all but two of the patients. The mean (SD) difference between the two events was 5 (5) ms, which did not differ significantly from zero. The relation was similar in patients with primary myocardial disease (11), and in those with valve disease (26), hypertension (five), and coronary artery disease (four). In the normal children, the mean interval was 2.5 (5) ms--not significantly different from zero. By contrast, the first deflection of the fourth heart sound consistently preceded the timing of peak atrial inflow velocity by 55 (10) ms. Agreement was much closer between the onset of atrial flow and the onset of the atrial sound (mean difference 1 (5) ms, not significantly different from zero). Gallop sounds seem to be closely related to changes in ventricular inflow velocity, and thus to the effects of forces acting on blood flow. The forces underlying the third sound seem to arise within the ventricle and are responsible for sudden deceleration of flow during rapid ventricular filling. The fourth sound, occurring at the onset of the "a" wave, is more likely to arise from dissipation of forces causing acceleration of blood flow--that is, atrial systole itself.

Journal ArticleDOI
TL;DR: Current generations of permanent pacemakers, which may have a combination of dualchamber and sensor technologies, will permit the restoration of normal cardiac physiology (AV synchrony and/or rate response) in most patients.
Abstract: Properly timed atrial systole may alter systolic performance by the mechanism of Starling's law of the heart, which states that the extent of systolic myocardial fiber shortening is dependent on the degree of diastolic fiber stretch, or preload. However, the atrial contribution to physiological need and thus is critical in developing the proper cardiac output response to exercise. Current generations of permanent pacemakers, which may have a combination of dualchamber and sensor technologies, will permit the restoration of normal cardiac physiology (AV synchrony and/or rate response) in most patients.

Journal ArticleDOI
TL;DR: Both the mathematical model and canine experiments showed that relatively low-amplitude ITP variations, rising synchronously with the onset of cardiac systole and having an optimal duration, assist the failing heart by augmentation of aortic flow.
Abstract: The hemodynamic effects of phasic variations in intrathoracic pressure (ITP) timed to the cardiac cycle were predicted by a mathematical model and were compared with data from canine experimental studies. The model was used to predict the hemodynamic effects of changing the onset of the ITP rise relative to the start of cardiac systole, as well as the hemodynamic effects of changes in the duration and amplitude of the ITP rise. The predictions of the model were compared with hemodynamic data from seven anesthetized dogs. Cardiac function was depressed with large doses of verapamil and propranolol, and the hearts were atrioventricular sequentially paced at a rate of 72 beats/min. Phasic ITP variations were generated by a perithoracic vest and were electronically timed to the cardiac cycle. The model predicted, and the experimental data confirmed, that phasic intrathoracic pressure variations generated by vest inflation, timed to the cardiac cycle, can augment both peak and mean aortic flow. The following predictions of the model were also confirmed by the experimental data: 1) Maximum flow augmentation occurs when the onset of the ITP rise is simultaneous with the onset of left ventricular isovolumic contraction, and the ITP rise has a duration of 400 msec. 2) The magnitude of the flow augmentation is a function of the amplitude of the ITP rise. The experimental data showed that there was little further flow augmentation when the ITP rise was greater than 30-40 mm Hg. 3) The magnitude of flow augmentation was inversely proportional to the peak left ventricular elastance (Emax). The best fit between the measured and predicted flow augmentations was obtained for an assumed Emax of 0.5 mm Hg/ml, while Emax measurements in three dogs, using a volume conductance catheter and transient vena caval occlusion, yielded values of 0.4-1.6 mm Hg/ml. Thus, both the mathematical model and canine experiments showed that relatively low-amplitude ITP variations, rising synchronously with the onset of cardiac systole and having an optimal duration, assist the failing heart by augmentation of aortic flow. The degree of cardiac assistance decreases if the ITP variations do not rise synchronously with the onset of systole, or if their duration is not optimal. Thus, properly applied ITP variations may be used as an efficient, noninvasive method to temporarily assist the failing heart.

Journal ArticleDOI
TL;DR: The haemodynamic response to SVT differs significantly between the two types of reciprocating tachycardia, particularly as regards cardiac output and blood pressure, and is mainly influenced by the temporal relationship between atrial and ventricular systole, independent of the rate of contraction.
Abstract: SUMMARY In 16 subjects with paroxysmal supraventricular tachycardia (SVT) we sought a relationship between haemodynamic changes associated with artificially induced arrhythmias and the electrophysiological properties of the related atrioventricular (A V) nodal reentry circuit. In 10 patients (group 1) induced SVT was typical (long AH) and caused a significant fall in cardie output (–720 ml min-1) and arterial systolic pressure (–18 mmHg). In six subjects (group 2), induced SVT was atypical (long HA ) and did not significantly alter the output of the heart and systolic pressure, despite the elicitation of similar tachycardia. The opposite AV nodal reciprocation pattern which resulted in a substantial increase in AH/HH in group 1 and in a slight rise of the same variable in group 2, may explain these haemodynamic differences. In fact, atrial and ventricular systoles occurred simultaneously and impeded the ventricular filling in the former group, while a regular subsequence of contraction was maintained in the latter group. In group 2, systolic arterial pressure and cardiac output fell to the same level as in group 1 when right atrial pacing, at a similar rate of SVT, determined an increase of AH/HH similar to that observed during typical tachycardia. Thus, the haemodynamic response to SVT differs significantly between the two types of reciprocating tachycardia, particularly as regards cardiac output and blood pressure, and is mainly influenced by the temporal relationship between atrial and ventricular systole, independent of the rate of contraction. The different conduction velocities of the reciprocating circuit limbs and their interrelation seem to be major determinants of the haemodynamic pattern of SVT.

Journal ArticleDOI
TL;DR: The preliminary assumption, that the coupling between cardiac and locomotor rhythms during cycling was on the basis of a single ischemic muscle group, has apparently been disproven and there was considerable varia tion among subjects, refuting the authors' hypothesis.
Abstract: During some rhythmic exercises, the heart and exercise rates may become coupled (be within 1% of each other). If the intraarterial and skeletal intramus cular pressure cycles were reciprocal, blood flow to exercising muscle should be maximized and cardiac load minimized. In this study the authors tested the hypothesis that, while coupling is present, the phase lag between the pedaling and cardiac contraction cycles is consistent and appropriate. Twenty-seven sub jects pedaled, at a frequency natural to them, on an electronically braked bicy cle ergometer that held the power output constant regardless of pedaling rate. To assess the phase lag between pedal thrust (two per revolution) and heart beat, pedal-gated plots of the electrocardiography signal were generated throughout the most coupled five-minute work load for each of the 9 subjects in whom the rates were within 1% of each other for at least two consecutive four- second samples taken every fifteen seconds. During this interval of thirty-sec onds in...

Journal ArticleDOI
TL;DR: The results indicate that in the chicken the chronotropic effects of right vagus stimulation are greater than those of left Vagus stimulation, whereas right and left vagusstimulation are approximately equipotent on ventricular contraction and relaxation.
Abstract: We determined the effects of vagus nerve stimulation on cardiac cycle length and on ventricular contraction and relaxation in 18 chickens anesthetized with pentobarbital. Right vagus stimulation at a constant frequency of 35 Hz prolonged cycle length by 190%, whereas left vagus stimulation at the same frequency increased cycle length by 136%. When one burst of stimuli was delivered to the right vagus nerve each cardiac cycle, but the timing of the stimuli was changed within the cardiac cycle, the response of the avian pacemaker cells varied substantially with the timing of the stimuli. Right and left vagus stimulation at a constant frequency of 20 Hz depressed ventricular contraction by 62 +/- 6 and 52 +/- 6%, respectively, and depressed ventricular relaxation by 56 +/- 7 and 53 +/- 7%, respectively. These results indicate that in the chicken the chronotropic effects of right vagus stimulation are greater than those of left vagus stimulation, whereas right and left vagus stimulation are approximately equipotent on ventricular contraction and relaxation.

Journal ArticleDOI
TL;DR: In normal myocardium in situ, regional abnormalities in wall motion may be associated with alterations of local ventricular activation and refractoriness, factors that in the diseased heart could lead to increased susceptibility to arrhythmias.
Abstract: Transmural multipolar electrodes, sonomicrometers implanted within the left ventricular wall, and cardiac electrical stimulation techniques were used to examine the effect of transient mechanically applied traction to the left ventricular free wall on local electrophysiological properties. Twenty-five open-chest dogs were atrially paced (cycle length 400 ms) followed by insertion of timed premature extrastimuli at left ventricular epicardial pacing sites either in the vicinity of (traction zone) or remote from (nontraction-control zone) the site of left ventricular free wall traction. Electrophysiological recordings were made before and during intermittent left ventricular free wall traction applied in late diastole (rate 25 cm/s; duration 170 ms). In 22 of 25 dogs, application of traction resulted in early local ventricular activation (mean activation advancement 64 +/- 15 ms), altered QRS morphology of the last conducted atrial drive train beat, and a relative prolongation of ventricular refractoriness in the traction zone. Conversely, in the nontraction-control zone, early activation did not occur and refractoriness was unchanged. Alterations in regional myocardial blood flow (assessed by microsphere technique) did not appear responsible for the observed changes. Furthermore, phenol interruption of local sympathetic or combined sympathetic and parasympathetic innervation or verapamil pretreatment had no impact on the mechanically induced electrophysiological changes. Thus, in normal myocardium in situ, regional abnormalities in wall motion may be associated with alterations of local ventricular activation and refractoriness, factors that in the diseased heart could lead to increased susceptibility to arrhythmias.

Journal ArticleDOI
TL;DR: This study shows the effectiveness of using continuous-wave Doppler echocardiography to assess the influence of atrial systole on left ventricular performance in patients with mitral stenosis.
Abstract: Continuous wave Doppler echocardiography was used to assess the hemodynamic role of left atrial systole and its effect on left ventricular performance in 31 patients with isolated mitral stenosis. Fourteen of the patients had mild stenosis, whereas the remaining 17 had severe stenosis. The contribution of atrial systole to the cardiac output was 24% in the patients with mild stenosis and 15% in those with severe stenosis ( p

Journal ArticleDOI
TL;DR: Even in an isolated atrial contraction, the inflection point that marks the boundary between slow "atriogenic" closure presumably due to anulus narrowing and rapid closure Presumably due to hemodynamic force was easily identified.
Abstract: Tricuspid valve orifice and tricuspid valve anulus areas were measured simultaneously in the anesthetized dog with a newly developed area-measuring system based on electromagnetic induction. This system permitted real-time monitoring of the area enclosed by the edges of valve leaflets and by the juncture of the valve leaflet and the cardiac wall in situ, without artificial constraint to the valve motion. Right atrial and right ventricular pressures were measured with two catheter-tipped micromanometers. During control state, tricuspid valve orifice area (TOA) increased up to its peak [1.38 +/- 0.26 cm2 (mean +/- SD)] coincidently with either atrial systole or rapid ventricular filling. Atrial contraction evoked distinct presystolic tricuspid anulus narrowing with concomitant slow TOA reduction. This slow TOA reduction began 30.0 +/- 16.1 msec before systolic atrioventricular pressure crossover, and the following rapid TOA decrease was completed 38.7 +/- 12.2 msec after systolic atrioventricular pressure crossover. TOA began to increase 48.4 +/- 30.4 msec before diastolic atrioventricular pressure crossover at the end portion of the isovolumic relaxation phase, opposing residual transvalvular pressure gradient (3.33 +/- 1.79 mm Hg). The slow presystolic TOA decrease was considered to be a reflection of the presystolic anulus narrowing caused by atrial systole. An isolated atrial contraction induced by administering 1 mg acetylcholine chloride into the atrioventricular node artery or by vagus nerve stimulation could produce complete valve closure. Even in an isolated atrial contraction, the inflection point that marks the boundary between slow "atriogenic" closure presumably due to anulus narrowing and rapid closure presumably due to hemodynamic force was easily identified.

Proceedings ArticleDOI
09 Nov 1989
TL;DR: In decerebrated and artificially ventilated cats the impulse activity of cardiac preganglionic fibers was recorded in a closed chest preparation together with ECG, arterial pressure, and respiration and the presence of low-frequency and high-frequency rhythms was demonstrated by parametric spectral and cross-spectral analyses.
Abstract: A signal processing technique is proposed for the extraction of short-term variability rhythms from the discharge of cardiac sympathetic fibers In decerebrated and artificially ventilated cats the impulse activity of cardiac preganglionic fibers was recorded in a closed chest preparation together with ECG, arterial pressure, and respiration The neural signal was fed into an analog spike counter, obtaining a stepwise count signal Beat-by-beat variability series were extracted; the spike-count signal is sampled once per cardiac cycle convolving with a FIR low-pass filter The presence of low-frequency and high-frequency rhythms was demonstrated by parametric spectral and cross-spectral analyses >

Journal ArticleDOI
TL;DR: A method of evaluating the antifibrillatory properties of drugs by their effect on the acceleration of the cardiac rhythm by electric pulses was developed and permitted measurement of fibrillation thresholds and the maximal driving frequency of stimulation.

Proceedings ArticleDOI
Shigeru Eiho1, A. Amano1
19 Sep 1989
TL;DR: In this paper, the 3D shape of each part of the heart is reconstructed in a voxel space by using 11 inner and/or outer boundary curves on 7 transverse, 2 coronal, and 2 sagittal images.
Abstract: The 3-D shape of each part of the heart is reconstructed in a voxel space (32*32*32) by using 11 inner and/or outer boundary curves on 7 transverse, 2 coronal, and 2 sagittal images. Such 3-D shapes can be obtained at 23 cardiac phases in a cardiac cycle. Some quantitative cardiac parameters are calculated from the 3-D data and displayed as 3-D functional images. These include volume changes of each part of the heart, 3-D percent shortening of the regional wall of the left ventricle, and wall thickness. Also described is a hardware system which can display cross-sectional shapes of the pulsating heart, as well as 3-D shapes of each part or combined parts of the heart. >

Journal Article
TL;DR: Results indicate that the rapid cine MRI technique is a useful tool for noninvasively determining regurgitant blood flow in patients with various valvular heart diseases.