Showing papers on "Cardiac cycle published in 1971"

Assessment of regional myocardial performance from biplane coronary cineangiograms.

Abstract: Bifurcations of coronary arteries provide a myriad of natural landmarks on the epicardial surface. With biplane coronary cineangiograms, these bifurcations can be located in space and followed in time. By calculating the spatial distances between bifurcations on successive cine frames, multiple epicardial segment lengths and their dynamic changes during the cardiac cycle can be determined. In 5 animals with epicardial metal markers sutured near the coronary bifurcations, epicardial segment lengths measured from opacified bifurcations correlated closely with those obtained from metal markers (SEE = 2.2%). Epicardial segment lengths were not affected by intracoronary injection of contrast medium in the first 5 to 6 cardiac cycles. Biplane coronary Cineangiograms of 11 patients were analyzed. Measurements of individual segment lengths yielded reproducible curves reflecting various phases of ventricular contraction and filling. These curves allowed quantitation and simultaneous comparison of the onset, duration, extent and rate of segment shortening in multiple and selected areas of the heart. In 5 patients, the extent of shorteing was 1 to 19 percent along the septum, 17 to 27 percent on the free wall and 10 to 15 percent at the base of the left ventricle. Mechanical activation of the left ventricle began from the antereoseptal area at the apex and progressed toward the base and the posterior surface. In 5 of 6 patients with coronary artery disease, localized abnormalities of contraction were found in areas of previous myocardial infarction or at regions supplied by the stenotic arteries. The diseased segments showed either systolic lengthening or marked reduction in rate and extent of shortening. The onset of shortening was frequently delayed. In addition to defining the anatomic details of the coronary circulation, biplane coronary cineangiograms provide a wealth of physiologic information regarding the dynamic changes in geometry, dimensions and movements of the heart. As the first step to utilizing this physiologic information, this study has demonstrated the validity, feasibility and clinical usefulness of this technique in assessing regional myocardial performance in man.

Assessment of myocardial contractility in children and young adults from ventricular pressure recordings.

Abstract: The index V pm (the actual or physiologic maximal shortening velocity of the contractile element) has been obtained from the analysis of left ventricular pressure recordings and then applied to the assessment of myocardial contractility in man Pressures during the isovolumic period of ventricular systole were recorded during routine catheterization of 46 patients with a variety of cardiac lesions The quantity V pm , that is (dp/dt/kp) max , was compared with the hemodynamic evaluation of each patient based on the left ventricular end-diastolic pressure, ejection fraction and left ventricular end-diastolic volume V pm was selected for this study since it appeared to be largely independent of load and does not require biplane angiocardiography and extrapolation analyses Preliminary results suggest that a value of V pm greater than 16 sec −1 indicates normal myocardial function; lower values indicate abnormal function In several instances this index was not in agreement with the hemodynamic measures, but in most cases the clinical assessment supported the conclusion drawn from V pm This study suggests that reliable guides to myocardial contractility can readily be obtained from high fidelity pressure recordings alone

Change in left ventricular volume during angiocardiography.

Abstract: Seven selective left ventricular angiocardiograms that permitted measurement of end-diastolic volume for 5 consecutive cardiac cycles were analyzed. Neither end-diastolic volume nor end-systolic volume changed significantly between the first and second cycles after ventricular opacification. A progressive increase in the major and minor ventricular semiaxes occurred beginning with the third opacified cycle. Correspondingly, the average end-diastolic volume and end-systolic volume increased by 6.9 ml and 3.4 ml, respectively, between the second and third cardiac cycles. Ventricular volumes progressively increased between the third and fifth cardiac cycles in each patient. These data suggest that sodium diatrizoate has a negative inotropic effect on left ventricular myocardium by the third cardiac cycle after injection. Physiologic information from cineangiocardiography should be derived from the first 2 cardiac cycles after opacification.

A useful muscarinic parameter and the differential recording of atrial and ventricular tension in the perfused rabbit heart.

Abstract: 1. A simple method of recording right atrial tension from the Langendorff perfused rabbit has been described; it is based on the “transverse” method of recording cardiac contractions described by Beckett (1970). 2. Right atrial and ventricular tensions were recorded by transducers attached to threads stitched into the right atrium and right ventricle, the heart being retained and prevented from rotating by two threads stitched into the intraventricular septum as described by Beckett. 3. Right ventricular diastolic tension was adjusted to 7.5 g. Interference with the atrial record by ventricular systole was overcome by adjustment of diastolic right atrial tension to its optimal value between 1 and 1.5 g. 4. Sympathetic nerve stimulation and infusions of sympathomimetic drugs increased atrial and ventricular tension development and ventricular rate but no differential effects were observed. Conversely, vagal nerve stimulation and particularly infusions of muscarinic drugs markedly depressed atrial tension development at a time when ventricular tension and rate were little affected. 5. Besides providing an additional pharmacological parameter, the main advantage of recording atrial tension is in the quantitative evaluation of muscarinic activity in the whole perfused heart. Further, measurement of right atrial tension affords a useful method of detecting muscarinic activity in those drugs (e.g. ganglion stimulants) which have mixed parasympathetic and sympathetic cardiac actions.

Electrical activity of a single fibre of the human embryonic heart

Abstract: The hearts of 7–12 week old human embryos were investigated by means of intracellular microelectrodes. Average heart rate was 91 beats per minute. The cardiac pacemaker was localized in the sinus venosus. The mean amplitude of action potentials amounted in the pacemaker fibres to 58 mV, in the atrium to 90 mV and in the ventricles to 110 mV. The isolated left auricle exhibits spontaneous activity. The atria are electrically isolated from the ventricles and excitation is conducted by a preferential pathway, most probably by the atrio-ventricular node and bundle.

Mechanism of changes in the second heart sound in aortic stenosis

Abstract: The dynamic correlates of the second heart sound were studied by right and left heart catheterization in 15 subjects with pure aortic valve stenosis and in 6 subjects who had no cardiac lesion. The duration of left ventricular systole is not, as previously thought, prolonged in aortic stenosis. Left ventricular ejection is prolonged because of late closure of the aortic valve related to the higher level of left ventricular pressure compared to that of aortic pressure (pressure gradient). In addition, there is a delay in the time of occurrence of the aortic incisura in relation to valve closure. The sum of both these delays (aortic valve closure in relation to end of systole; incisura in relation to valve closure) explains the delay of the aortic component of the second heart sound, which occurs either at the time of the pulmonary component or after it (reverse splitting). The changes of the second heart sound were found to be grossly proportional to the magnitude of the pressure gradient across the aortic valve and, therefore, significant in evaluating the severity of the lesion.

Pressure-flow studies in man: effect of atrial systole on ventricular function in mitral stenosis

Abstract: The effect of atrial contraction on left ventricular function in six patients with varying degrees of mitral stenosis was determined by utilizing the pressure gradient technique to measure instantaneous aortic blood flow and pressure. Aortic flow was measured as ventricular rate was controlled by right ventricular pacing to create A-V (atrioventricular) dissociation at varying rates (90-150 beats/min). At each heart rate, beats with preceding P waves, effective atrial systole, were grouped according to the duration of the P-R interval. Beats without P waves served as controls. There was always a significant increase in stroke volume, created by effective atrial systole, but the P-R interval at which it took place was different for each patient. There was no difference in the stroke volume for beats preceded by P waves having a P-R interval within the range of 0.05-0.20 sec. These beats were grouped for each patient, subjected to regression analysis, and compared to control beats. The absolute and percent change created by effective atrial systole was inversely proportional to the severity of the disease as determined by mitral valve orifice size. Effective atrial systole plays less of a role in augmenting left ventricular function in patients with mitral stenosis than in patients with normal valves.

Arterial pulse wave velocity and left ventricular tension period in cardiac arrhythmias

Abstract: Peripheral pulse wave velocity, measured by a non-invasive photoplethysmographic technique, was constant and independent of variations in cardiac cycle length and, therefore, of arterial diastolic pressure in seven out of eight cases of atrial fibrillation and in four cases with ventricular premature beats. It seems, therefore, that the blood pressure itself is not an important factor in the regulation of pulse wave velocity. Left ventricular tension period, estimated indirectly by the same technique, was inversely related to the preceding cycle length. Premature beats of atrial and ventricular origin had longer left ventricular tension periods than sinus beats.

The second heart sound in atrial septal defect.

Abstract: Ventricular and arterial pressure tracings, electrocardiograms and phonocardiograms were studied in 4 normal subjects and 52 patients with atrial septal defect After excluding cases in which complicating factors were involved, 10 cases of secundum type and 3 cases of primum type were studied in detail Contrary to previously held beliefs, right ventricular systole is not longer than left ventricular systole in these patients Therefore, pulmonary valve closure still occurs very close to aortic valve closure, as in normal subjects However, the incisuras of the large arteries are more widely separated than in normal subjects The explanation for the wide splitting of the second heart sound is based on recent work that attributes the sound components to vibrations of the blood, valves and walls of the large arteries at the time of the aortic and pulmonary arterial rebounds Patients with atrial septal defect have a dilated pulmonary artery This causes a slower reaction of the wall and a later occurrence of both the pulmonary incisura and the pulmonary component of the second heart sound

Roentgenologic determination of the variations in heart volume during the cardiac cycle.

Abstract: Variations in heart volume during systole and diastole have been investigated by roentgenologic methods by several authors. Contradictory results have been reported. JONSELL (1939) believed that the difference between the diastolic and systolic volumes could amount to about 20 per cent of the diastolic value, but that the usual difference obtained in determinations in young adults was about 15 per cent. HUBACHER & NYFFELER (1946) also recorded a difference between the diastolic and systolic volumes and suggested the use of this difference for the calculation of the stroke volume. LIND (1950) observed in a series of 18 children that the variations in the heart volume during the cardiac cycle could be as great as 10 to 15 per cent of the mean heart volume. The diastolic volume was usually the greater but the systolic was sometimes more than or equal to the diastolic volume. KJELLBERG et colI. (1951) recorded no statistically significant difference between the cardiac volume during systole and diastole; HALL et colI. (1961) considered this difference to be small (not

Timing of chest X-ray exposures in relation to the cardiac cycle

Abstract: Without using sophisticated physiological methods it is not possible to tell at what part of the cardiac cycle a particular chest radiograph was exposed. Even in the presence of a Starr Edwards valve with a radio-opaque ball it is often uncertain exactly when exposure of the film occurred. For example, following aortic valve replacement, if the ball lies against the rim, exposure may be in diastole or, alternatively, during isometric contraction or relaxation of the left ventricle, both of which are systolic events. With the ball between the rim and the top of the cage timing may be either at the beginning or towards the end of ventricular ejection.

Synchronized pulsed cardiac planigraphy.

Abstract: The authors describe sagittal and transverse axial planigraphy of the cardiac ventricles during angicardiography and selective coronary arteriography. The blurring effect of cardiac motion is eliminated by controlled intermittent x-ray exposures during the planigraphic sweep, the instant of exposure being predetermined and programmed to occur at an identical point in each cardiac cycle.