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Biomedical subjects

E Craige

Publications and source records attributed to E Craige.

At least 19 recordsLinked to original sources
PubMed1991

The influence of left ventricular relaxation in determination of the intensity of the aortic component of the second heart sound.

In a study of the aortic component of the second heart sound (A2) intensity, using 10 dogs, miniature cardiac accelerometers were attached to the exposed left ventricle (LV) at the apex, and to the surface of proximal aorta, to obtain LV and aortic surface acceleration. Manometer tipped catheters were used to detect aortic systolic pressure and diastolic pressure and time constant of left ventricular pressure fall "T". Drugs (Nitroprusside, Dobutamine and Methoxamine) altered aortic pressure, LV contraction and LV relaxation. When T was +/- 35% of control, the aortic systolic pressure and diastolic pressure were good predictors of A2 intensity. When LV relaxation was impaired, increasing T greater than 135% of control, the A2 intensity for any given aortic pressure was reduced. When relaxation was hyperactive, decreasing T less than 65% of control, A2 intensity was increased. Aortic pressure/T which assessed both aortic pressure and relaxation ability, is a better determinant of A2 intensity than aortic systolic pressure or aortic diastolic pressure alone.

Animals↗
PubMed1987

Disparity between ejection and end-systolic indexes of left ventricular contractility in mitral regurgitation.

To examine left ventricular function in mitral regurgitation (MR), we compared the ejection phase indexes of left ventricular contractility with maximal systolic elastance (Emax) in an experimental preparation of MR. In eight anesthetized open-chest dogs, pressure-volume loops were derived during afterload manipulation with methoxamine and nitroprusside from simultaneous left ventricular pressure and dimensional (sonomicrometry techniques) data before and after creation of MR. From these data maximal systolic elastance (Emax), the end-systolic pressure-volume relationship (ESPVR), and the end-systolic stress-volume relationship (ESSVR) were determined by linear regression analysis. After creation of MR, end-diastolic volume increased significantly (40 +/- 13 to 53 +/- 18 ml, p less than .001); likewise end-systolic volume increased (28 +/- 11 to 33 +/- 15 ml, p less than .05). Ejection fraction increased after MR (35 +/- 6% to 44 +/- 8%, p less than .005), as did the mean velocity of fiber shortening (0.62 +/- 0.20 to 1.02 +/- 0.39 sec-1, p less than .02). In contrast, Emax declined significantly (4.63 +/- 2.5 to 3.54 +/- 1.94 mm Hg/ml, p less than .05); ESPVR and ESSVR showed similar directional changes. An inverse relationship was found between systolic elastance and end-diastolic volume in both control and MR states. When Emax, ESPVR, and ESSVR were normalized to end-diastolic volume, they were unchanged after MR. These results suggest that either there was a decline in left ventricular contractile state after MR, or that contractility was unchanged (if elastance is normalized for increased contractility, but occurred as a consequence of increased preload with no significant change in afterload.

Animals↗
PubMed1986

Mechanism of the dicrotic pulse.

The dicrotic pulse is an abnormal carotid pulse found in conjunction with certain conditions characterised by low cardiac output. It is distinguished by two palpable pulsations, the second of which is diastolic and immediately follows the second heart sound. In the course of open chest canine studies of the second heart sound, micromanometers and an electromagnetic flow meter were used to study proximal aortic haemodynamic function in both strong and weak beats. It was found that the incisural notch of the aortic pressure signal is not strongly dependent on the extent of left ventricular ejection, and is of essentially normal amplitude even in beats having greatly reduced aortic flow. In contrast, the magnitude of the systolic upstroke of the aortic pressure pulse is strongly determined by the magnitude of left ventricular ejection and is considerably reduced in weak beats. With low cardiac output the relative size of the incisural notch becomes exaggerated in comparison with the overall pulsation, thus creating the characteristic M shaped waveform of the dicrotic pulse.

Animals↗
PubMed1985

Influence of the aortic component of the second heart sound on left ventricular maximal negative dP/dt in the dog.

Maximal negative left ventricular dP/dt is widely used as a measure of isovolumic muscular relaxation of the left ventricle. In the course of canine experiments designed to elucidate the hemodynamic events responsible for the aortic component of the second heart sound, high-fidelity left ventricular pressure and dP/dt signals were recorded and accelerations detected on the root of the aorta and epicardium at the cardiac apex. The second heart sound was coincident with maximal negative dP/dt and affected its magnitude to a variable and unpredictable extent. This may account for some of the unexpected variations in magnitude of maximal negative dP/dt that have been described in various disease states and in laboratory experiments where the effects of physiologic and pharmacologic interventions have been studied.

Animals↗
PubMed1985

Origin of the third heart sound: comparison of ventricular wall dynamics in hyperdynamic and hypodynamic types.

To investigate the left ventricular wall dynamics conducive to the third heart sound (S3) in both hyper- and hypodynamic filling conditions, eight dogs were studied in which an S3 was produced by hypoxemia and in eight others by acute mitral regurgitation. Pulse transit sonomicrometry crystals were used to measure external left ventricular dimension dynamics in the two principal axes. A miniature accelerometer was used to detect the epicardial S3 vibration. The development of the S3 was invariably associated with an increased peak velocity of long-axis external dimensional expansion in early diastole. This enhanced long-axis filling activity was not dependent on increased global chamber or short-axis filling dynamics and sometimes occurred when global filling rate was unchanged. In addition, the short-axis filling rate was sometimes reduced as the S3 developed. It is concluded that the common denominator of S3 generation in this acute dog model is exaggerated long-axis diastolic expansion activity which is present in both hyper- and hypodynamic left ventricular filling.

Acute Disease↗
PubMed1985

Abnormal diastolic mechanical vibration transmission characteristics of the left ventricle.

In 18 open chest canine experiments, the ability of the left ventricle to transmit a mechanical vibratory tone from base to apex has been studied. An artificial tone source of constant amplitude and frequency was applied to the base of the exposed left ventricle. A miniature vibration sensor was applied to the anterior epicardium near the ventricular apex. This permitted us to obtain a heart surface phonocardiogram, in order to detect the portion of the source vibration which was transmitted to the apex. In three of the dogs, the heart surface phonocardiogram from the apex was compared with simultaneous intraventricular phonocardiograms which showed the amplitude of the vibration which reached the intraventricular blood mass. It was found that the normal ventricle transmits the tone from base to apex almost exclusively during systole, when the ventricle is contracted and stiff. In marked contrast, the normally relaxed and soft ventricle fails almost completely to transmit the tone to the apex. In conditions of poor relaxation ability of the left ventricle due to global hypoxemia, manifested by a long "Time Constant T", an abnormal diastolic transmission of the tone to the apex occurred during early diastole. We have defined this abnormal early diastolic "crescendo-decrescendo" type of transmissibility as "Type 1". The Type 1 transmission is related to impaired relaxation of the ventricle and is a manifestation of one or more abnormal ventricular muscle properties, such as myocardial stiffness, viscosity and density. In conditions of left ventricular hemodynamic failure caused by global hypoxemia, a separate abnormal mid-to-late diastolic "crescendo" type of transmissibility was found, and is defined as "Type 2".(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Mechanical vibration transmission characteristics of the left ventricle: implications with regard to auscultation and phonocardiography.

Systolic-diastolic phasic alteration of left ventricular mechanical vibration transmissibility was studied in an open chest canine preparation. A continuous vibratory tone was applied to the base of the heart, and a miniature heart surface vibration sensor applied to the epicardium near the ventricular apex. This allowed the detection of the percent of the vibration that was transmitted from source to sensor. These data were compared with those from intracardiac phonocardiograms obtained using a micromanometer-tipped catheter. It was found that in systole, the ventricle transmitted a vibratory tone from the cardiac base to the apex so that it was readily detected by the heart surface sensor. In marked contrast, during diastole the relaxed ventricle failed almost completely to transmit the vibration to the apical position. When the dog experienced heart failure during hypoxia, the ventricular diastolic vibration transmissibility was found to equal or exceed that of the systolic phase.

Animals↗
PubMed1983

Left bundle branch block and mechanical events of the cardiac cycle.

Left bundle branch block (LBBB) is associated with a prolongation of the interval from the QRS onset to the onset of left ventricular (LV) ejection. The locus and prevalence of specific sites of delay were examined in 56 patients with complete LBBB using echocardiography, phonocardiography and external pulse recordings. The results were compared with those in 52 control subjects without LBBB. The onset of the QRS complex was used as the initial reference point of measurement of time intervals. The following abnormalities were found in patients with LBBB: (1) delayed mitral valve closure (Q-MC greater than 0.08 second) was the major site of delay in 23% of patients; (2) prolongation of the LV isovolumetric contraction time (greater than 0.06 second) was the major site of delay in 41%; (3) both Q-MC and LV isovolumetric contraction time were prolonged in 18%; and (4) in 26% of patients the onset of ventricular contraction determined by the onset of the increase of the apex impulse was delayed (Q-VC greater than 0.07 second). The most common cause of delayed ejection was a prolonged LV isovolumetric contraction time, which occurred in 59% of patients. A control group of 20 patients with abnormal LV function but without LBBB had a low incidence of the 3 types of delay in LV ejection (0 to 15%). Thus, the major abnormalities in the cardiac cycle in LBBB are due to the conduction defect and not to LV dysfunction. The results of this study suggest the presence of variable abnormalities of conduction in complete LBBB.

Adolescent↗
PubMed1983

The apex impulse in mitral stenosis: graphic explanation of the palpable movements at the cardiac apex.

Simultaneously recorded phonocardiograms and apexcardiograms of 39 patients with mitral stenosis (MS) were retrospectively analyzed. A notch on the upstroke of the apexcardiogram coincidental with the first heart sound (S1) occurred in 18 (47%) of the patients. The notch ratio or vertical distance from the onset of the apical impulse to the notch ratio or vertical distance from the onset of the apical impulse to the notch as a percentage of the total upstroke was measured and compared with the mean mitral diastolic gradient obtained at cardiac catheterization. Statistical analysis showed a significant relation (r = 0.61; p less than 0.01) between notch ratio and the mean mitral diastolic gradient. This study reaffirms that the complex palpable movements at the cardiac apex, consisting of a "tap" representing S1 occurring perceptibly after the onset of the apex impulse itself, are a useful diagnostic sign of MS. Furthermore, a graphic measurement of the extent of delay of S1 with respect to the onset of the apical thrust can provide a rough measure of the severity of the valvular obstruction.

Adult↗
PubMed1983

First heart sound in Ebstein's anomaly: observations on the cause of wide splitting by echophonocardiographic studies before and after operative repair.

Preoperative echophonocardiographic study of a 31 year old woman with Ebstein's anomaly and an atrial septal defect showed wide splitting of the first heart sound with an interval of 0.08 second between mitral valve and tricuspid valve closure. After application of the anterior tricuspid leaflet and anuloplasty, the mitral and tricuspid valves closed at the same time and there was a single first heart sound. These findings suggest that delayed tricuspid valve closure in Ebstein's anomaly is due to the abnormally large size and increased excursion of the anterior tricuspid leaflet rather than associated right bundle branch block or sluggish right ventricular contraction.

Adult↗