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James D Thomas

Publications and source records attributed to James D Thomas.

At least 91 records · Page 5Linked to original sources
PubMed2004

Anatomic M-mode, a pertinent tool for the daily practice of transthoracic echocardiography.

OBJECTIVES: We sought to compare anatomic M-mode (AMM), a new echocardiographic postprocessing option, and conventional M-mode (CMM) using fundamental imaging and tissue harmonic imaging. METHODS: Transthoracic echocardiography was performed in 15 selected patients to analyze the reproducibility of AMM and in 47 patients to assess its clinical value versus CMM. Acquisitions were performed successively: CMM fundamental imaging; CMM tissue harmonic imaging; tissue harmonic imaging cineloops for AMM; and fundamental imaging cineloops for AMM. Quantitative analysis was performed offline. The angle alpha between the CMM line and the septal endocardial interface was calculated and the expected percentage of error in measuring left ventricular diameter was derived. RESULTS: AMM analysis was reproducible. Optimal AMM full echocardiographic definition was obtainable in 77% of the population, whereas CMM was optimal for 49% because of scan line misalignment, causing a measurement overestimation exceeding 5%. CONCLUSION: The ability with AMM to reduce the alpha angle to 0 degrees and, thus, avoid overestimation of left ventricular dimensions might improve follow-up in several pathologic conditions.

Adolescent↗
PubMed2004

Determinant of left atrial dilation in patients with hypertrophic cardiomyopathy: a real-time 3-dimensional echocardiographic study.

To identify the determinants of left atrial (LA) dilation for patients with hypertrophic obstructive cardiomyopathy (HOCM), first we validated LA volume determination by real-time 3-dimensional echocardiography using magnetic resonance imaging in patients. Subsequently, real-time 3-dimensional echocardiography and 2-dimensional Doppler echocardiography were performed in 60 patients with HOCM and in 17 age-matched control subjects. LA volumes and left ventricular (LV) filling pressures were higher for patients with HOCM than in control subjects. By stepwise multilinear regression analysis, LV end-diastolic pressure, resting LV outflow tract pressure gradient, and LV wall thickness were significant determinants of LA dilation. However, tau, -dP/dt, LV stiffness, provokable pressure gradient, and mitral regurgitation did not have any independent relationship with LA volumes. Therefore, it is concluded that LA volume can be accurately determined by real-time 3-dimensional echocardiography; and LA dilation in patients with HOCM is related to LV filling pressure, LV outflow tract pressure gradient, and LV wall thickness.

Atrial Function, Left↗
PubMed2004

Geometric changes of mitral annulus assessed by real-time 3-dimensional echocardiography: becoming enlarged and less nonplanar in the anteroposterior direction during systole in proportion to global left ventricular systolic function.

OBJECTIVE: We sought to investigate the geometric changes of the mitral annulus during systole in relation to global left ventricular (LV) systolic function using real-time 3-dimensional (3D) echocardiography. METHODS: Real-time 3D echocardiography was performed in 23 patients with global LV systolic dysfunction with ejection fraction of 37 +/- 19% and 9 control subjects with ejection fraction of 62 +/- 4%. Volumetric data were divided into 9 rotational apical planes (angle increment = 20 degrees) using 3D software. Nine rotational annular dimensions (ADs) were measured in all planes in early and late systole. Nonplanar angle (NPA) of the annulus between two vectors from two hinge points of the annulus in the anteroposterior plane to the center between two commissures in the commissure-commissure plane was measured during early and late systole. Fractional changes of NPA and AD were defined as changes in percentage during systole. RESULTS: NPA significantly increased during systole (early, 145 +/- 12 degrees; late, 160 +/- 9 degrees; P < .01). Among 9 ADs, 3 anteroposteriorly directed ADs showed the most prominent fractional increases during systole in all patients. Both fractional changes of NPA ( R 2 = 0.87, P < .01) and the anteroposterior dimension, AD 1 ( R 2 = 0.85, P < .01) showed significant positive correlation with global LV systolic function. CONCLUSIONS: Real-time 3D echocardiography demonstrated that saddle shape of the mitral annulus was getting enlarged and less nonplanar mainly in the anteroposterior direction during systole. These geometric changes were proportional to the global LV systolic function.

Adult↗
PubMed2004

Mitral annular motion as a surrogate for left ventricular ejection fraction: real-time three-dimensional echocardiography and magnetic resonance imaging studies.

AIMS: To validate the accuracy of mitral annular motion assessed by real-time three-dimensional echocardiography (RT3DE) as a surrogate for determination of the left ventricular function in comparison with magnetic resonance imaging (MRI). METHODS AND RESULTS: Forty-seven patients with a variety of cardiac pathologies underwent both RT3DE and MRI exams. After 3D data sets were transferred to a PC with a custom-made program, nine consecutive rotational apical plane images (20 degrees apart) were displayed. The two mitral leaflet insertion points were manually identified in each plane. The geometry of the mitral annulus was reconstructed from a total of 18 coordinates (x, y, z), and the changes in mitral annular area and mitral annular motion along the apical long axis were calculated. The left ventricular ejection fraction (LVEF) determined by MRI was 41+/-18%, and 24 patients had LVEF<50%. Mitral annular motion (y) obtained by RT3DE was 11+/-5 mm and correlated moderately well with LVEF (x) measured by MRI (r=0.84, y=0.25x+0.43, p<0.0001). The mitral annular motion<12 mm was a good threshold for detecting LVEF<50% with 96% sensitivity, 85% specificity, and 91% accuracy. CONCLUSION: Mitral annular motion determined by RT3DE correlated moderately well with LVEF; and systolic motion, <12 mm, accurately detected LV dysfunction.

Adult↗
PubMed2004

Frank-Starling mechanism contributes modestly to ventricular performance during atrial fibrillation.

OBJECTIVES: The aim of this study was to assess whether Frank-Starling mechanism has an independent effect on left ventricular (LV) performance in atrial fibrillation (AF). BACKGROUND: Ventricular performance in AF depends on variable contractility through the interval-force mechanism based on the ratio of preceding and pre-preceding RR intervals (RR(p)/RR(pp)). The impact of end-diastolic volume (EDV) variability, through the Frank-Starling mechanism, is not well understood. METHODS: We induced AF in 16 open chest dogs. RR intervals, LV pressure, LV volume, and aortic flow were collected for >400 beats during rapid AF (ventricular cycle length 292 +/- 66 ms). In six of the dogs, additional data were collected while average ventricular cycle length was prolonged from 258 +/- 34 ms to 445 +/- 80 ms by selective vagal nerve stimulation of the AV node. RESULTS: The relations of maximal LV power (LVPower) and peak LV pressure derivative (dP/dt) versus RR(p)/RR(pp) were fitted to the equation y = A * (1 - EXP (RR(p)/RR(pp)min - RR(p)/RR(pp))/C) and the residuals (RES) of these relations were analyzed. LVPower and dP/dt strongly correlated with RR(p)/RR(pp) (r(2) = 0.67 +/- 0.12 and 0.66 +/- 0.12, P < .0001 for all correlations). Importantly, RES-LVPower and RES-dP/dt showed linear correlation with EDV (r(2) = 0.20 +/- 0.14 and r(2) = 0.24 +/- 0.17, P < .01 for all correlations). In the six dogs with slowed average ventricular rate, the slope of both residual relationships (RES-LVPower vs EDV and RES- dP/dt vs EDV) decreased (P < .03 for both). CONCLUSIONS: The Frank-Starling mechanism contributes to ventricular performance in AF independently of the interval-force effects of the beat-to-beat variability in cardiac contractility. The Frank-Starling mechanism is sensitive to the average ventricular rate.

Action Potentials↗
PubMed2004

The Coapsys device to treat functional mitral regurgitation: in vivo long-term canine study.

OBJECTIVE: We evaluated the capability of the Myocor Coapsys device (Myocor, Inc, Maple Grove, Minn) to reduce functional mitral regurgitation in a canine model of dilated cardiomyopathy. METHODS: Functional mitral regurgitation with heart failure was induced in 7 dogs by rapid ventricular pacing. The Coapsys device, which consists of anterior and posterior epicardial pads connected by a subvalvular chord, was then implanted. Heart failure was maintained by continued pacing for 8 weeks. Hemodynamic and echocardiographic measurements were performed at pre- and postsizing and after 8 weeks. The Coapsys subvalvular chord was cut to verify that maintenance of valve competency was due to the device. RESULTS: All implants were performed off-pump without atriotomy. Mitral regurgitation was reduced in all animals; mean mitral regurgitation grade was reduced from 2.9 +/- 0.7 to 0.7 +/- 0.8 (P =.00005) and was maintained at 0.8 +/- 0.8 after 8 weeks, without hemodynamic compromise or structural damage to the mitral valve. Mitral regurgitation returned to 3.6 +/- 0.8 (P =.102 versus presizing) after cutting the Coapsys subvalvular chord. CONCLUSION: The Coapsys device consistently and chronically reduced functional mitral regurgitation. This device is in clinical trials in the United States.

Animals↗
PubMed2004

Combination of pulsed-wave Doppler and real-time three-dimensional color Doppler echocardiography for quantifying the stroke volume in the left ventricular outflow tract.

Real-time three-dimensional (3-D) color Doppler echocardiography (RT3D) is capable of quantifying flow. However, low temporal resolution limits its application to stroke volume (SV) measurements. The aim of the present study was, therefore, to develop a reliable method to quantify SV. In animal experiments, cross-sectional images of the LV outflow tract were selected from the RT3D data to calculate peak flow rates (Q(p3D)). Conventional pulsed-wave (PW) Doppler was performed to measure the velocity-time integral (VTI) and the peak velocity (V(p)). By assuming that the flow is proportional to the velocity temporal waveform, SV was calculated as alpha x Q(p3D) x VTI/V(p), where alpha is a temporal correction factor. There was an excellent correlation between the reference flow meter and RT3D SV (mean difference = -1. 3 mL, y = 1. 05 x -2. 5, r = 0. 94, p < 0. 01). The new method allowed accurate SV estimations without any geometric assumptions of the spatial velocity distributions.

Animals↗
PubMed2004

Off-pump mitral valve repair using the Coapsys device: a pilot study in a pacing-induced mitral regurgitation model.

PURPOSE: The purpose of this study was to evaluate the ability of the Myocor Coapsys device to restore leaflet apposition and valve competency off-pump in a canine model of functional mitral regurgitation (MR). DESCRIPTION: The Coapsys device was surgically implanted in 10 dogs after MR induction by rapid ventricular pacing. The Coapsys consists of anterior and posterior epicardial pads connected by a subvalvular chord. The annular head of the posterior pad was positioned at the annular level to draw the posterior leaflet and annulus toward the anterior leaflet. Final device size was selected when MR was minimized or eliminated as assessed by color flow Doppler echocardiography. EVALUATION: All implants were placed off-pump without atriotomy, and mean MR grade was reduced from 2.9 +/- 0.7 to 0.6 +/- 0.7 (p < 0.001) acutely. No hemodynamic compromise was noted. CONCLUSIONS: The Coapsys device consistently and significantly reduced or eliminated functional MR acutely. Further study will be required to assess the chronic stability of the repair in this animal model.

Animals↗
PubMed2004

Registration of real-time 3-D ultrasound images of the heart for novel 3-D stress echocardiography.

Stress echocardiography is a routinely used clinical procedure to diagnose cardiac dysfunction by comparing wall motion information in prestress and poststress ultrasound images. Incomplete data, complicated imaging protocols and misaligned prestress and poststress views, however, are known limitations of conventional stress echocardiography. We discuss how the first two limitations are overcome via the use of real-time three-dimensional (3-D) ultrasound imaging, an emerging modality, and have called the new procedure "3-D stress echocardiography." We also show that the problem of misaligned views can be solved by registration of prestress and poststress 3-D image sequences. Such images are misaligned because of variations in placing the ultrasound transducer and stress-induced anatomical changes. We have developed a technique to temporally align 3-D images of the two sequences first and then to spatially register them to rectify probe placement error while preserving the stress-induced changes. The 3-D spatial registration is mutual information-based. Image registration used in conjunction with 3-D stress echocardiography can potentially improve the diagnostic accuracy of stress testing.

Algorithms↗
PubMed2003

A randomised trial of an Internet weight control resource: the UK Weight Control Trial [ISRCTN58621669].

BACKGROUND: Obesity treatment is notoriously unsuccessful and one of the barriers to successful weight loss reported by patients is a lack of social support. The Internet offers a novel and fast approach to the delivery of health information, enabling 24-hour access to help and advice. However, much of the health information available on the Internet is unregulated or not written by qualified health professionals to provide unbiased information. The proposed study aims to compare a web-based weight loss package with traditional dietary treatment of obesity in participants. The project aims to deliver high quality information to the patient and to evaluate the effectiveness of this information, both in terms of weight loss outcomes and cost-effectiveness. METHODS: This study is a randomised controlled trial of a weight loss package against usual care provided within General Practice (GP) surgeries in Leeds, UK. Participants will be recruited via posters placed in participating practices. A target recruitment figure of 220 will enable 180 people to be recruited (allowing for 22% dropout). Participants agreeing to take part in the study will be randomly allocated using minimisation to either the intervention group, receiving access to the Internet site, or the usual care group. The primary outcome of the study will be the ability of the package to promote change in BMI over 6 and 12 months compared with traditional treatment. Secondary outcomes will be the ability of the Internet package to promote change in reported lifestyle behaviours. Data will be collected on participant preferences, adherence to treatment, health care use and time off work. Difference in cost between groups in provision of the intervention and the cost of the primary outcome will also be estimated. CONCLUSION: A positive result from this study would enhance the repertoire of treatment approaches available for the management of obesity. A negative result would be used to inform the research agenda and contribute to redefining future strategies for tackling obesity.

Adolescent↗
PubMed2003

Importance of ischemic and viable myocardium for patients with chronic ischemic mitral regurgitation and left ventricular dysfunction.

The objective of this investigation is to determine the importance of ischemic viable myocardium for clinical outcomes in patients with severe chronic ischemic mitral regurgitation and severe left ventricular dysfunction undergoing surgical correction of mitral regurgitation. The study included 54 patients with left ventricular ejection fraction of 27 +/- 9%. Positron emission tomography was performed preoperatively for the identification of ischemic viable myocardium. The patients with a large amount of ischemic viable myocardium (> or =5 segments) had significantly lower 6-month mortality rates than those with less viable myocardium (0 to 4 segments) after the surgery.

Cause of Death↗
PubMed2003

Importance of mitral valve repair associated with left ventricular reconstruction for patients with ischemic cardiomyopathy: a real-time three-dimensional echocardiographic study.

BACKGROUND: Left ventricular (LV) reconstruction surgery leads to early improvement in LV function in ischemic cardiomyopathy (ICM) patients. This study was designed to evaluate the impact of mitral valve (MV) repair associated with LV reconstruction on LV function 1-year after surgery in ICM patients assessed by real-time 3-dimensional echocardiography (3DE). METHODS AND RESULTS: Sixty ICM patients who underwent the combination surgery (LV reconstruction in 60, MV repair in 30, and revascularization in 52 patients) were studied. Real-time 3DE was performed and LV volumes were obtained at baseline, discharge, 6-month and >or=12-month follow-up. Reduction in end-diastolic volumes (EDV) by 29% and in end-systolic volumes by 38% were demonstrated immediately after surgery and remained at subsequent follow-up (P<0.0001). The LV ejection fraction significantly increased by about 10% at discharge and was maintained >or=12-month (P<0.0001). Although the LV volumes were significantly larger in patients with MV repair before surgery (EDV, 235+/-87 mL versus 193+/-67 mL, P<0.05), they were similar to LV volumes of the patients without MV repair at subsequent follow-ups. However, the EDV increased from 139+/-24 mL to 227+/-79 mL (P<0.01) in 7 patients with recurrent mitral regurgitation (MR). Improvement in New York Heart Association functional class occurred in 81% patients during late follow-up. CONCLUSIONS: Real-time 3DE demonstrates that LV reconstruction provides significant reduction in LV volumes and improvement in LV function which is sustained throughout the 1-year follow-up with 84% cardiac event free survival. If successful, MV repair may prevent LV redilation, while recurrent MR is associated with increased LV volumes.

Echocardiography, Three-Dimensional↗
PubMed2003

Determinants of LV diastolic function during atrial fibrillation: beat-to-beat analysis in acute dog experiments.

Left ventricular (LV) diastolic function during atrial fibrillation (AF) remains poorly understood due to the complex interaction of factors and beat-to-beat variability. The purpose of the present study was to elucidate the physiological determinants of beat-to-beat changes in LV diastolic function during AF. The RR intervals preceding a given cardiac beat were measured from the right ventricular electrogram in 12 healthy open-chest mongrel dogs during AF. Doppler echocardiography and LV pressure and volume beat-to-beat analyses were performed. The LV filling time (FT) and early diastolic mitral inflow velocity-time integral (E(vti)) were measured using the pulsed Doppler method. The LV end-diastolic volume (EDV), peak systolic LV pressure (LVP), minimum value of the first derivative of LV pressure curve (dP/dt(min)), and the time constant of LV pressure decay (tau) were evaluated with the use of a conductance catheter for 100 consecutive cardiac cycles. Beat-to-beat analysis revealed a cascade of important causal relations. LV-FT showed a significant positive linear relationship with E(vti) (r = 0.87). Importantly, there was a significant positive linear relationship between the RR interval and LV-EDV in the same cardiac beat (r = 0.53). Consequently, there was a positive linear relationship between LV-EDV and subsequent peak systolic LVP (r = 0.82). Furthermore, there were significant positive linear and negative curvilinear relationships between peak systolic LVP and dP/dt(min) (r = 0.95) and tau (r = -0.85), respectively, in the same cardiac beat. In addition, there was a significant negative curvilinear relationship between dP/dt(min) and tau (r = -0.86). We have concluded that the determinants of LV diastolic function in individual beats during AF depend strongly on the peak systolic LVP. This suggests that the major benefit of slower ventricular rate appears related to lengthening of LV filling interval, promoting subsequent higher peak systolic LVP and greater LV relaxation.

Animals↗
PubMed2003

Effect of stromal-cell-derived factor 1 on stem-cell homing and tissue regeneration in ischaemic cardiomyopathy.

BACKGROUND: Myocardial regeneration via stem-cell mobilisation at the time of myocardial infarction is known to occur, although the mechanism for stem-cell homing to infarcted tissue subsequently and whether this approach can be used for treatment of ischaemic cardiomyopathy are unknown. We investigated these issues in a Lewis rat model (ligation of the left anterior descending artery) of ischaemic cardiomyopathy. METHODS: We studied the effects of stem-cell mobilisation by use of granulocyte colony-stimulating factor (filgrastim) with or without transplantation of syngeneic cells. Shortening fraction and myocardial strain by tissue doppler imaging were quantified by echocardiography. FINDINGS: Stem-cell mobilisation with filgrastim alone did not lead to engraftment of bone-marrow-derived cells. Stromal-cell-derived factor 1 (SDF-1), required for stem-cell homing to bone marrow, was upregulated immediately after myocardial infarction and downregulated within 7 days. 8 weeks after myocardial infarction, transplantation into the peri-infarct zone of syngeneic cardiac fibroblasts stably transfected to express SDF-1 induced homing of CD117-positive stem cells to injured myocardium after filgrastim administration (control vs SDF-1-expressing cardiac fibroblasts mean 7.2 [SD 3.4] vs 33.2 [6.0] cells/mm2, n=4 per group, p<0.02) resulting in greater left-ventricular mass (1.24 [0.29] vs 1.57 [0.27] g) and better cardiac function (shortening fraction 9.2 [4.9] vs 17.2 [4.2]%, n=8 per group, p<0.05). INTERPRETATION: These findings show that SDF-1 is sufficient to induce therapeutic stem-cell homing to injured myocardium and suggest a strategy for directed stem-cell engraftment into injured tissues. Our findings also indicate that therapeutic strategies focused on stem-cell mobilisation for regeneration of myocardial tissue must be initiated within days of myocardial infarction unless signalling for stem-cell homing is re-established.

Animals↗
PubMed2003

Improvement in diastolic intraventricular pressure gradients in patients with HOCM after ethanol septal reduction.

We sought to validate measurement of intraventricular pressure gradients (IVPG) and analyze their change in patients with hypertrophic obstructive cardiomyopathy (HOCM) after ethanol septal reduction (ESR). Quantitative analysis of color M-mode Doppler (CMM) images may be used to estimate diastolic IVPG noninvasively. Noninvasive IVPG measurement was validated in 10 patients undergoing surgical myectomy. Echocardiograms were then analyzed in 19 patients at baseline and after ESR. Pulsed Doppler data through the mitral valve and pulmonary venous flow were obtained. CMM was used to obtain the flow propagation velocity (Vp) and to calculate IVPG off-line. Left atrial pressure was estimated with the use of previously validated Doppler equations. Data were compared before and after ESR. CMM-derived IVPG correlated well with invasive measurements obtained before and after surgical myectomy [r = 0.8, P < 0.01, Delta(CMM - invasive IVPG) = 0.09 +/- 0.45 mmHg]. ESR resulted in a decrease of resting LVOT systolic gradient from 62 +/- 10 to 29 +/- 5 mmHg (P < 0.001). There was a significant increase in the Vp and IVPG (from 48 +/- 5to 74 +/- 7 cm/s and from 1.5 +/- 0.2 to 2.6 +/- 0.3 mmHg, respectively, P < 0.001 for both). Estimated left atrial pressure decreased from 16.2 +/- 1.1 to 11.5 +/- 0.9 mmHg (P < 0.001). The increase in IVPG correlated with the reduction in the LVOT gradient (r = 0.6, P < 0.01). Reduction of LVOT obstruction after ESR is associated with an improvement in diastolic suction force. Noninvasive measurements of IVPG may be used as an indicator of diastolic function improvement in HOCM.

Cardiomyopathy, Hypertrophic↗
PubMed2003

Nitroprusside in critically ill patients with left ventricular dysfunction and aortic stenosis.

BACKGROUND: Vasodilators are considered to be contraindicated in patients with severe aortic stenosis because of concern that they may precipitate life-threatening hypotension. However, vasodilators such as nitroprusside may improve myocardial performance if peripheral vasoconstriction is contributing to afterload. METHODS: We determined the response to intravenous nitroprusside in 25 patients with severe aortic stenosis and left ventricular systolic dysfunction. Patients were included in the study if they had been admitted to the intensive care unit for invasive hemodynamic monitoring of heart failure and if they had a depressed ejection fraction (<or=0.35), severe aortic stenosis (aortic-valve area, <or=1 cm2), and a depressed cardiac index (<or=2.2 liters per minute per square meter). Patients were excluded if they had hypotension, defined as either the need for intravenous inotropic or pressor agents or a low mean systemic arterial pressure (<60 mm Hg). Patients were enrolled irrespective of other, coexisting valve disease or coronary artery disease. RESULTS: At base line, the mean (+/-SD) ejection fraction was 0.21+/-0.08; the aortic-valve area was 0.6+/-0.2 cm2, with peak and mean gradients of 65+/-37 and 39+/-23 mm Hg, respectively; and the cardiac index was 1.60+/-0.35 liters per minute per square meter. After six hours of therapy with nitroprusside (at which time the dose had been increased to a mean of 103+/-67 microg per minute), the cardiac index had increased to 2.22+/-0.44 liters per minute per square meter (P<0.001 for the comparison with base line). After 24 hours of nitroprusside infusion (dose, 128+/-96 microg per minute), the cardiac index had increased further, to 2.52+/-0.55 liters per minute per square meter (P<0.001 for the comparison with base line). Nitroprusside was well tolerated and had minimal side effects. CONCLUSIONS: Nitroprusside rapidly and markedly improves cardiac function in patients with decompensated heart failure due to severe left ventricular systolic dysfunction and severe aortic stenosis. It provides a safe and effective bridge to aortic-valve replacement or oral vasodilator therapy in these critically ill patients.

Aged↗