Biomedical subjects

C P Appleton

Publications and source records attributed to C P Appleton.

49 records · Page 3Linked to original sources

PubMed1987

Influence of recipient atrial contraction on left ventricular filling dynamics of the transplanted heart assessed by Doppler echocardiography.

Recipient atrial remnants retain electrical and mechanical activity after orthotopic cardiac transplantation. This study investigated the influence of recipient atrial contraction timing on Doppler ultrasound mitral flow velocity curves, isovolumic relaxation time, peak early mitral flow velocity (M1), mitral valve pressure half-time and peak mitral flow velocity due to atrial systole (M2). Clearly identifiable recipient atrial electrical activity (P waves) was present in 7 of 10 patients studied early postoperatively 2 to 6 months (mean 2.5) (early group) and in 20 of 24 patients seen 1 to 11 years (mean 3) after transplantation (late group). Median age and gender distribution were similar in both groups. For analysis of its influence on isovolumic relaxation time, pressure half-time and M1, recipient atrial contraction was classified by its position in the cardiac cycle as early systole, late systole or diastole. For analysis of M2, it was classified as early diastole, late diastole or systole. Compared with its occurrence in diastole, recipient atrial contraction in late systole was associated with a shorter isovolumic relaxation time, shorter pressure half-time and higher M1. In early systole it was associated with a longer pressure half-time and lower M1 than in diastole; isovolumic relaxation time was unchanged. Recipient atrial contraction in early diastole resulted in a lower M2 than in systole, whereas simultaneous contraction of recipient and donor atria in late diastole resulted in an increase in M2. These results indicate that the timing of recipient atrial contraction and relaxation significantly influences left ventricular filling dynamics.

Adult↗

PubMed1987

Intraventricular flow during isovolumic relaxation: description and characterization by Doppler echocardiography.

This study describes the characteristics of a prominent Doppler flow velocity signal representing intraventricular flow during left ventricular isovolumic relaxation. The flow during the isovolumic relaxation period was demonstrated in 60 subjects, including 7 with a normal heart, 26 with hypertrophic cardiomyopathy, 10 with aortic valve disease, 9 with a transplanted heart and 8 others. All had normal to hyperdynamic left ventricular systolic function with some degree of cavity obliteration as seen in the apical two-dimensional echocardiographic views. In contrast, this isovolumic relaxation period flow could not be demonstrated in the absence of cavity obliteration in any of 20 patients with either normal or diminished left ventricular systolic function. Isovolumic relaxation period flow was best recorded from the apical transducer position and was directed toward the apex in all patients. By pulsed wave, and with two-dimensional Doppler ultrasound, the isovolumic relaxation period flow originated within a narrow area in the medial portion of the left ventricle along the middle or basal segments of the interventricular septum, but was recorded over a larger area toward the apex. The peak isovolumic relaxation period flow velocity was recorded just basal to the area of cavity obliteration, usually at the level of the papillary muscles, and ranged from 0.4 to 2.3 m/s (mean of 1.0 m/s). This isovolumic relaxation period flow started with aortic valve closure and, in 50 of the 60 patients, it lasted throughout isovolumic relaxation until mitral valve opening. In the other 10 patients (all with hypertrophic cardiomyopathy), it lasted for only a part (mean 63%) of this period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1987

Superior vena cava and hepatic vein Doppler echocardiography in healthy adults.

Pulsed wave Doppler ultrasound recordings of blood flow velocity in the superior vena cava were made in 40 healthy adults (aged 22 to 69 years) during both normal respiration and 10 second episodes of apnea. The forward flow velocity pattern was biphasic, with systolic flow velocity greater than diastolic flow velocity. During apnea, peak flow velocities ranged from 32 to 69 cm/s (mean 45.7 +/- 8.4) during systole and from 6 to 45 cm/s (mean 27.2 +/- 8.3) in early diastole. Systolic flow velocity integrals also exceeded diastolic values. With atrial systole (A wave), forward flow velocities were reduced or flow was reversed. Thirty-nine of 40 subjects had A wave flow reversal during apnea, and in these the ratio of reverse to total forward flow velocity integrals ranged from 1 to 16% (mean 6 +/- 4%). Compared with values during apnea, there were higher mean values with inspiration and lower values with expiration for velocities and flow velocity integrals. Hepatic vein tracings, when adequate (12 of 40 subjects), showed forward flow characteristics similar to those from the superior vena cava, but with more frequent and larger A wave and ventricular end-systole (atrial V wave) flow reversals. Superior vena cava flow velocity variables were calculated in subgroups to assess the effects of age, respiratory pattern and increased venous return. This study defines normal Doppler ultrasound superior vena cava and hepatic vein flow velocities and their variation with respiration in healthy adults. These results can be used for comparison with patterns found in disease states.

Adult↗

PubMed1986

Alpha 1- and alpha 2-adrenoceptor stimulation: changes in venous capacitance in intact dogs.

The peripheral circulatory effects of alpha 1-adrenoceptor stimulation with methoxamine hydrochloride were compared with those of alpha 2-stimulation with UK 14304-18 in 12 intact dogs. Doses of each agent were infused to increase systemic vascular resistance and arterial pressure 50 and then 100% above control. Heart rate was controlled with atropine. At the higher dose, methoxamine increased mean aortic pressure (PAo) from a control of 77.3 +/- 1.6 to 152.9 +/- 3.2 mmHg, mean circulatory filling pressure (MCFP) from 8.0 +/- 0.4 to 13.3 +/- 1.3 mmHg, and central blood volume (CBV) from 21.3 +/- 1.1 to 25.9 +/- 1.5 ml X kg-1, whereas cardiac output did not change. UK 14304-18 increased PAo from 78.1 +/- 2.6 to 148.9 +/- 2.7 mmHg, MCFP from 7.9 +/- 0.4 to 10.6 +/- 0.4 mmHg, and CBV from 21.0 +/- 1.1 to 24.1 +/- 1.5 ml X kg-1, whereas cardiac output decreased from 151.7 +/- 9.4 to 126.3 +/- 5.8 ml X kg-1 X min-1. Mean circulatory filling pressure and CBV were higher with methoxamine than with UK 14304-18. Effective vascular compliance, determined by serial measurements of MCFP during ganglionic blockade after rapid changes in blood volume, decreased from a control value of 1.9 +/- 0.1 to 1.3 +/- 0.3 ml X mmHg-1 X kg-1 with methoxamine, but did not change with UK 14304-18 (1.9 +/- 0.1 ml X mmHg-1 X kg-1). At any given change in blood volume, there was a higher MCFP with alpha 1-stimulation compared with alpha 2-stimulation. Both agents decreased unstressed vascular volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Pulmonary venous flow velocity: relation to hemodynamics, mitral flow velocity and left atrial volume, and ejection fraction.

Abnormal pulmonary venous flow velocity patterns are present in multiple cardiac disease states, but the determinants of pulmonary venous flow velocity have not been fully elucidated. To determine the relative importance of several proposed factors that could influence pulmonary venous flow, anatomic, hemodynamic, and Doppler mitral and pulmonary venous flow velocity data were compared in 50 consecutive patients undergoing cardiac catheterization for clinical reasons. Pulmonary venous diastolic flow velocity was most strongly related to left ventricular isovolumetric relaxation time (r = -0.59), left ventricular end-diastolic pressure (LVEDP, r = 0.50), left atrial minimum volume (r = 0.50), mitral deceleration time (r = -0.50), and early diastolic mitral flow velocity (r = 0.45). Pulmonary venous systolic flow velocity related best with left atrial minimum volume (r = -0.45) and left atrial ejection fraction (r = 0.44). Pulmonary venous systolic flow velocity integral also showed the strongest relation with left atrial minimum volume (r = -0.48). Relations between pulmonary venous flow velocity and velocity time integrals and other variables were sometimes significantly different, apparently caused in part to differences in heart rate. These results suggest that pulmonary venous diastolic flow velocity is influenced by the same factors that influence early left ventricular diastolic filling; pulmonary venous systolic flow velocity relates best to left atrial volume and atrial ejection fraction and does not relate to left ventricular ejection fraction. Future studies analyzing pulmonary venous flow velocity variables should include data on both peak velocities and velocity time integrals as well as left atrial size and function.

Aged↗

PubMedDate not supplied

Flow velocity acceleration in the left ventricle: a useful Doppler echocardiographic sign of hemodynamically significant mitral regurgitation.

Doppler echocardiography is a sensitive method to detect mitral regurgitation in patients with both native and prosthetic valves. However, estimates of the amount of mitral regurgitation remain semiquantitative, and even severe mitral regurgitation may be underestimated in the presence of markedly eccentric regurgitant jets or acoustic shadowing of the left atrium by mitral or aortic prostheses. This report describes the Doppler findings in 10 patients with severe native valve mitral regurgitation (angiographic grade III or IV) and in 15 patients with severe bioprosthetic mitral regurgitation that required valve replacement. An increase in peak mitral flow velocity above normal values was seen in eight of 10 patients with severe native valve mitral regurgitation (greater than or equal to 130 cm per second) and 11 of 15 patients with severe prosthetic valve mitral regurgitation (greater than or equal to 210 cm per second). One of 10 patients with a native valve and four of 15 patients with a bioprosthetic valve appeared to have only a localized left atrial systolic flow disturbance, incorrectly suggesting that the mitral regurgitation was mild. However, in all patients with severe mitral regurgitation, a low velocity (less than 100 cm per second) flow signal could be recorded in the left ventricle that was directed toward the mitral valve in systole. This flow signal showed a gradual increase in velocity as the sample volume was moved toward the mitral valve, with an abrupt further increase on entry into the left atrium. This signal was continuous with antegrade mitral flow and had the same orientation as mitral regurgitation recorded by continuous wave technique from the apex. A similar flow signal was not recorded in the left ventricle of any individual in a control group of 30 patients who had no mitral regurgitation or who had angiographic grade I or II mitral regurgitation. These findings suggest that acceleration of left ventricle flow toward the mitral valve in systole is only recorded when there is hemodynamically significant mitral regurgitation that is approximately equal to angiographic grade III or IV. Recognition of this Doppler finding may help in the estimation of mitral regurgitation severity, especially in difficult diagnostic situations.

Aged↗

PubMedDate not supplied

Variability of Doppler echocardiographic indexes of left ventricular filling in transplant recipients and in normal subjects.

This study examines the reproducibility and variability of pulsed wave Doppler versus continuous wave Doppler ultrasound indexes of left ventricular filling in cardiac allograft recipients and in normal subjects. The following indexes were studied: isovolumic relaxation time, pressure half-time, peak early mitral flow velocity, and peak mitral flow velocity after atrial systole. Intraobserver and interobserver variability were assessed by regression analysis. Individual components of variance (subject, reader, beat, day, and tracing) were estimated in a subset of five patients and five normal subjects, and estimated total variance defined for each group. Temporal (day-to-day) variability for 95% confidence was estimated for these patients and for normal subjects. Temporal variability in the group from which the subsets were drawn was measured from absolute and percent change in values on two occasions. Estimated and observed 95% confidence limits were compared. Intersubject variability was the largest component of variance in both transplant recipients and in normal subjects. For all indexes in transplant recipients (in the absence of rejection) and normal subjects, observed absolute mean differences (+/- 2 standard deviations) between values from recordings taken on two different days were larger than the 95% confidence limits estimated from the components of variance analysis. The observed 95% limits for transplant recipients versus normal subjects were as follows: isovolumic relaxation time, 20 msec versus 6 msec; pressure half-time, 16 msec versus 9 msec; peak early mitral flow velocity, 32 cm per second versus 17 cm per second; and peak mitral flow velocity after atrial systole, 28 cm per second versus 10 cm per second.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

Doppler flow velocity patterns of the superior vena cava, inferior vena cava, hepatic vein, coronary sinus, and atrial septal defect: a guide for the echocardiographer.

Pulsed-wave Doppler provides the echocardiographer the advantage of range resolution; confusion as to the source of Doppler shift information is unusual. One area of the heart that may lead to interpretive difficulties, however, is the right atrium because the right atrium receives blood flow from three venous sources and from the left atrium when an atrial septal defect is present. Our article presents information on the normal pulsed-wave Doppler spectral displays for the superior vena cava, inferior vena cava, hepatic vein, and coronary sinus. Because it is clinically pertinent, methods on how to differentiate these normal venous flow patterns from atrial septal defect flow will be emphasized.

Blood Flow Velocity↗

PubMedDate not supplied

Relationship of left atrial pressure and pulmonary venous flow velocities: importance of baseline mitral and pulmonary venous flow velocity patterns studied in lightly sedated dogs.

Prior clinical and animal studies have shown a markedly different relationship between left atrial pressure and the systolic fraction of pulmonary venous flow but have not discussed possible reasons for this discrepancy. To examine the possibility that these disparate results are due to differences in baseline mitral and pulmonary venous flow velocities, we recorded both velocities with left atrial and left ventricular pressure under different loading conditions in eight lightly sedated normal dogs. With constant atrial pacing at 85 beats/min, mean left atrial pressure was increased from 5.3 +/- 1.1 mm Hg at baseline to 16.1 +/- 1.7 mm Hg with volume and methoxamine infusion (p < 0.05). As left atrial pressure increased, the operating compliance of the left atrium decreased, whereas left atrial volumes and ejection fraction increased. Baseline pulmonary venous diastolic flow velocity was larger than systolic velocity (66 +/- 9 versus 36 +/- 11 cm/sec), with the systolic fraction of pulmonary venous flow 31% +/- 8%. With increasing left atrial pressure, pulmonary venous diastolic velocity did not change, but peak systolic velocity (57 +/- 16 cm/sec) and the systolic fraction (48% +/- 9%) both increased (p < 0.05). Changes in pulmonary venous diastolic flow velocity closely followed changes in early diastolic mitral flow velocity (r = 0.85, p < 0.05). Mean left atrial pressure, or change in mean left atrial pressure, was related to the ratio of pulmonary venous systolic to diastolic velocity time integral (r = 0.59 to 0.62, p < 0.01) and the pulmonary venous systolic fraction (r = 0.58 to 0.60; p < 0.01). When expressed as change from baseline, these variables showed even stronger correlations with left atrial pressure (r = 0.72 to 0.76, p < 0.001). These results are consistent with previous animal and clinical results that indicate pulmonary venous diastolic flow is closely related to early mitral flow velocity, whereas systolic flow is determined primarily by left atrial systolic function. The markedly different relationships observed between left atrial pressure and pulmonary venous systolic flow in animal and clinical studies are most likely due to different baseline flow velocity patterns and differences in left atrial systolic reserve. Future studies investigating these relationships should include data on mitral and pulmonary venous flow velocities as well as left atrial size and systolic function.

Animals↗

PubMedDate not supplied

Visualization of the hepatic veins: new approaches for the echocardiographer.

Visualization and cardiac Doppler interrogation of the hepatic veins has become an important and integral part of the routine echocardiographic examination. The challenge lies in adequate visualization of the hepatic veins by use of the standard subcostal approach. This article proposes alternate approaches when the standard view yields unsatisfactory visual and cardiac Doppler information.

Echocardiography, Doppler↗

PubMedDate not supplied

Feasibility of obtaining pulmonary venous flow velocity in cardiac patients using transthoracic pulsed wave Doppler technique.

The purpose of this study was to determine, in an adult population, the percentage of patients in whom high quality pulmonary venous flow velocity recordings can be obtained using current transthoracic pulsed wave Doppler techniques. Pulmonary venous and mitral flow velocity variables obtained with a pulsed wave Doppler method were used for the indirect assessment of left ventricular (LV) diastolic function and LV filling pressures. The general clinical use of these methods, however, remains uncertain because the transthoracic success rate of obtaining all components of pulmonary venous flow velocity has been variable, and sometimes reported to be as low as 30% to 60%. Mitral and pulmonary venous flow velocity variables were obtained using pulsed wave Doppler signals in 200 consecutive adult patients (mean age 68.2 +/- 11.4 years) in normal sinus rhythm who were referred for echocardiographic study. Six cardiac sonographers and five ultrasound systems were used. The success rate for obtaining pulmonary venous systolic and diastolic flow velocity was 95%, reverse flow velocity at atrial contraction was 90%, and the duration of reverse flow at atrial contraction was 89%. In the 5% to 11% of patients in whom pulmonary flow velocities could not be adequately recorded, the most common reasons were depth limitations of the pulsed wave Doppler machine, marked cardiac enlargement, or left atrial wall motion artifact. The success rate also was influenced by the ultrasound equipment used, individual variation among sonographers, and even the type (impaired, pseudonormal, restricted) of associated mitral filling pattern. Given current machine technology, sonographer education, and daily practice, high quality, complete recordings of pulmonary venous flow velocity can be obtained in approximately 90% of adult patients using the precordial transthoracic Doppler technique. These results suggest that using these variables as an aid for evaluating LV diastolic function and filling pressures may have broader clinical applicability than previously appreciated.

Adult↗

PubMedDate not supplied

Effects of alpha 2-adrenergic stimulation with UK 14,304-18 on the heart and peripheral circulation of intact dogs.

To determine the extent of alpha 2-adrenoreceptor control of cardiovascular function, we studied the hemodynamic effects of the relatively selective alpha 2-adrenergic agonist UK 14,304-18 on the heart and peripheral circulation of intact dogs. Administration of increasing intravenous doses of UK 14,304-18 to conscious dogs given atropine to maintain heart rate (HR) resulted in a reproducible increase in mean aortic (AO) pressure (77.6 +/- 5.0 to 136.4 +/- 6.5 mm Hg, p less than 0.05) and reductions in stroke volume (31.7 +/- 2.9 to 17.9 +/- 1.9 ml/kg/min, p less than 0.05) and left ventricular (LV) dP/dt (2,120 +/- 280.0 to 1,463 +/- 196.1 mm Hg/s, p less than 0.05). In ganglion-blocked dogs UK 14,304-18 did not alter the slope of the LV end-systolic pressure-volume relationship when compared with angiotensin and nitroprusside (79.9 +/- 11.1 control vs. 73.3 +/- 8.7 mm Hg/ml/kg UK 14,304-18, p greater than 0.05), nor did it change the volume intercept (-0.46 +/- 0.12 control vs. -0.53 +/- 0.16 ml/kg UK 14, 304-18, p greater than 0.05) indicating no direct effect on LV contractile function. Changes in indices of diastolic function, including the time constant of isovolumic relaxation, time to peak filling, and chamber volume elasticity were similar to those of equipressor doses of angiotensin, indicating no direct effect on LV diastolic function. Effects on the peripheral circulation were studied in dogs undergoing transient acetylcholine-induced circulatory arrest. UK 14,304-18 increased mean circulatory filling pressure (7.9 +/- 0.3 to 10.3 +/- 0.2 mm Hg, p less than 0.05) and the pressure gradient for venous return (7.6 +/- 0.4 to 9.0 +/- 0.3 mm Hg, p less than 0.05). Central blood volume increased with UK 14,304-18 (15.6 +/- 1.1 to 18.7 +/- 1.5 ml/kg, p less than 0.05), but this increase was not sufficient to maintain cardiac output (CO) during the UK 14,304-18 infusion, which decreased from 157.4 +/- 11.1 to 131.5 +/- 8.9 ml/kg/min (p less than 0.01) in the presence of increased LV afterload. The time constant of relaxation of the arterial system increased and the arterial compliance decreased with increasing mean arterial pressure. Thus, this relatively selective alpha 2 agonist does not directly alter cardiac function but increased tone in arterial resistance vessels and in systemic veins. The fall in CO appears to be caused by a mismatch between preload and afterload, which is the net result of quantitatively different effects on systemic veins and arteries.

Adrenergic alpha-Agonists↗

PubMedDate not supplied

Successful treatment of early infective endocarditis and mediastinitis in a heart transplant recipient.

We report a case of bacterial endocarditis in a heart transplant recipient that was diagnosed 6 weeks after operation when a transesophageal echocardiogram revealed vegetations on both sides of the atrial septum. The patient also had postoperative mediastinitis and pericarditis. He underwent two mediastinal explorations, pericardiectomy, and 22 weeks of antibiotics and is free of infection 1 year after transplantation. We presume that the source of infection was contamination of the donor heart by the donor's right lung, which was harvested en bloc with the heart.

Endocarditis, Bacterial↗