Biomedical subjects

Ann C Tweddel

Publications and source records attributed to Ann C Tweddel.

7 recordsLinked to original sources

PubMed2005

Flow-mediated changes in pulse wave velocity: a new clinical measure of endothelial function.

AIMS: To test whether measuring hyperaemic changes in pulse wave velocity (PWV) could be used as a new method of assessing endothelial function for use in clinical practice. METHODS AND RESULTS: Flow-mediated changes in vascular tone may be used to assess endothelial function and may be induced by distal hyperaemia, while endothelium-mediated changes in vascular tone can influence PWV. These three known principles were combined to provide and test a novel method of measuring endothelial function by the acute effects of distal hyperaemia on upper and lower limb PWV (measured by a recently developed method). Flow-mediated changes in upper and lower limb PWV were compared in 17 healthy subjects and seven patients with stable chronic heart failure (CHF), as a condition where endothelial function is impaired but endothelium-independent dilator responses are retained. Corroborative measurements of PWV and brachial artery diameter responses to endothelium-dependent and -independent pharmacological stimuli were performed in a further eight healthy subjects. Flow-mediated reduction of PWV (by 14% with no change in blood pressure) was found in normal subjects but was almost abolished in patients with CHF. PWV responses appear to be inversely related to and relatively greater than brachial artery diameter responses. CONCLUSION: The method may offer potential advantages of practical use and sensitivity over conduit artery diameter responses to measure endothelial dysfunction.

Adult↗

PubMed2005

The effect of ventricular pacing on measurements of left ventricular function: a comparison between echocardiographic methods and with radionuclide ventriculography.

AIMS: Different methods exist for measuring left ventricular function echocardiographically; each may be error prone due to the abnormal pattern of ventricular activation during pacing. METHODS AND RESULTS: Echocardiography was undertaken on 307 patients with permanent pacemakers; a subset of 57 underwent radionuclide ventriculography. Intrinsic and paced beats were analysed for left ventricular function by: Simpson's bi-plane, Teicholz M-mode, wall-motion scoring and 'eyeball' assessment. Agreement between techniques and with radionuclide ventriculography were compared according to intrinsic or paced beats. Echocardiographic measures of ejection fraction give mean values 5% higher than radionuclide ventriculography (Simpson's 30+/-9%, vs. Teicholz 30+/-13% vs. radionuclide ventriculography 25+/-9%, p=0.03). Agreement between Simpson's, Teicholz and radionuclide ventriculography by Bland-Altman analysis showed poor agreement (Simpson's vs. Teicholz range (4xSD)=57%, Simpson's vs. radionuclide ventriculography=36%, Teicholz vs. radionuclide ventriculography=46%, p=0.02), the level of agreement deteriorates with ventricular pacing (Simpson's vs. Teicholz range=61%, Simpson's vs. radionuclide ventriculography=34%, Teicholz vs. radionuclide ventriculography=47%, p=0.02). The correlation between wall motion analysis and radionuclide ventriculography is moderately poor (all subjects r=0.58, ventricular pacing r=0.52, not pacing r=0.66). CONCLUSION: Echocardiography and radionuclide ventriculography are the only non-invasive techniques to assess left ventricular function in the paced population. Results are poorly interchangeable and the accuracy of any comparison dependent on the underlying rhythm.

Echocardiography↗

PubMed2005

"Pure" diastolic dysfunction is associated with long-axis systolic dysfunction. Implications for the diagnosis and classification of heart failure.

AIMS: To investigate regional systolic function of the left ventricle, to test the hypothesis that "pure" diastolic dysfunction (impaired global diastolic filling, with a preserved ejection fraction > or = 50%) is associated with longitudinal systolic dysfunction. METHODS AND RESULTS: One hundred thirty subjects (31 patients with asymptomatic diastolic dysfunction, 30 with diastolic heart failure, 30 with systolic heart failure; and 39 age-matched normal volunteers) were studied by conventional and tissue Doppler echocardiography. Global diastolic function was assessed using the flow propagation velocity, and by estimating left ventricular filling pressure from the ratio of transmitral E and mitral annular E(TDE) velocities (E/E(TDE)); and global systolic function by measurement of ejection fraction. Radial and longitudinal functions were assessed separately from posterior wall and mitral annular velocities. Global and radial systolic function were similar in patients with "pure" diastolic dysfunction and normal subjects, but patients with either asymptomatic diastolic dysfunction or diastolic heart failure had impaired longitudinal systolic function (mean velocities: 8.0+/-1.2 and 7.7+/-1.5 cm/s, respectively, versus 10.1+/-1.5 cm/s in controls; p<0.001). In subjects with normal ejection fraction, global diastolic function correlated with longitudinal systolic function (r=0.56 for flow propagation velocity, and r=-0.53 for E/E(TDE) ratio, both p<0.001), but not with global systolic function. CONCLUSION: Worsening global diastolic dysfunction of the left ventricle is associated with a progressive decline in longitudinal systolic function. Diastolic heart failure as conventionally diagnosed is associated with regional, subendocardial systolic dysfunction that can be revealed by tissue Doppler of long-axis shortening. Diagnostic algorithms and definitions of heart failure need to be revised.

Cross-Sectional Studies↗

PubMed2003

Subclinical left ventricular dysfunction in asymptomatic patients with Type II diabetes mellitus, related to serum lipids and glycated haemoglobin.

The aim of the present study was to measure regional ventricular function at rest and during stress in order to assess if patients with Type II diabetes have subclinical myocardial dysfunction and if it is related to risk factors. Seventy subjects (35 patients with Type II diabetes with no symptoms, signs or history of heart disease, and 35 age- and sex-matched healthy controls) had echocardiography at rest and during dobutamine stress. Myocardial velocities were measured off-line from digital loops of colour tissue Doppler. Subendocardial function was assessed from the mean longitudinal velocities of four basal segments (apical views) and radial function from the velocities of the basal posterior wall (parasternal view). Systolic functional reserve was calculated as the increase in velocity from baseline. Longitudinal peak systolic velocity was lower in patients with diabetes, at rest (5.6 +/- 1.4 compared with 6.5 +/- 1.1 cm/s) and at peak stress (10.9 +/- 2.8 compared with 14.3 +/- 2.1 cm/s) (both P <0.01). Functional reserve was impaired in patients with diabetes (+5.4 +/- 2.0 compared with +7.7 +/- 1.7 cm/s; P <0.01). Radial systolic velocity was higher in patients with diabetes (5.4 +/- 1.3 compared with 4.7 +/- 1.4 cm/s; P <0.05). Resting longitudinal systolic function correlated inversely with low-density lipoprotein-cholesterol ( r =-0.53), glycated haemoglobin ( r =-0.48), age ( r =-0.41) and diastolic blood pressure ( r =-0.38) (all P < 0.05). Peak stress systolic velocity correlated inversely with glycated haemoglobin ( r =-0.46) and age ( r =-0.44) (both P < 0.01). In conclusion, patients with Type II diabetes and no clinical heart disease have impaired subendocardial function of the left ventricle at rest and peak stress, which is related to glycated haemoglobin and serum low-density lipoprotein-cholesterol.

Aged↗

PubMed2002

Arterial distensibility: acute changes following dynamic exercise in normal subjects.

The time course of acute changes in large artery distensibility immediately and for 60 min following maximum treadmill exercise in normal subjects was characterized by simultaneously measuring upper and lower limb pulse wave velocity (PWV). A new oscillometric technique was used, which has proven to be sensitive to changes in distensibility induced by acute changes in vascular tone independently of blood pressure. The observed changes in PWV are attributable to changes in vascular tone corresponding to recovery from a systemic net constrictor response and a local net dilator response to exercise with persisting postexercise vasodilatation. They are inadequately explained by associated changes in blood pressure and cannot be attributed to changes in heart rate or viscosity. Modeled as a system of n coupled linear differential equations, the minimum (and adequate) order required to reproduce these patterns was n = 1 for the upper and n = 2 for the exercising lower limb. The economy of the solution suggests entrainment among the multiple interactive mechanisms governing vasomotor control.

Adolescent↗

PubMed2002

Left ventricular long-axis diastolic function is augmented in the hearts of endurance-trained compared with strength-trained athletes.

In order to determine left ventricular global and regional myocardial functional reserve in endurance-trained and strength-trained athletes, and to identify predictors of exercise capacity, we studied 18 endurance-trained and 11 strength-trained athletes with left ventricular hypertrophy (172+/-27 and 188+/-39 g/m(2) respectively), and compared them with 14 sedentary controls. Global systolic (ejection fraction) and diastolic (transmitral flow) function, and regional longitudinal and transverse myocardial velocities [tissue Doppler echocardiography (TDE)], were measured at rest and immediately after exercise. In endurance-trained compared with strength-trained athletes, resting heart rate was lower (59+/-11 and 76+/-9 beats/min respectively; P<0.001), and the increase at peak exercise was greater (+211% and +139% respectively; P<0.001). In addition, exercise duration, workload, maximal oxygen consumption and global systolic functional reserve (but not peak ejection fraction) were higher in the endurance-trained athletes, and resting global diastolic function (E/A ratio 1.62+/-0.40 compared with 1.18+/-0.23; P<0.01) (where E-wave is peak velocity of early-diastolic mitral inflow and A-wave is peak velocity of mitral inflow during atrial contraction) and long-axis diastolic velocities (E(TDE)/A(TDE) ratio 2.2+/-1.2 compared with 1.1+/-0.3; P<0.01) (where E(TDE) and A(TDE) represent peak early- and late-diastolic myocardial or tissue velocity respectively) were augmented. Systolic velocities were similar. Exercise capacity was best predicted from end-diastolic diameter index and E/A ratio at rest, and end-diastolic volume index and diastolic longitudinal velocity during exercise (r=0.74, n=43, P<0.001). In conclusion, endurance-trained athletes had higher left ventricular long-axis diastolic velocities, augmented global early diastolic filling, and greater chronotropic and global systolic functional reserve. Maximal oxygen consumption was determined by diastolic loading and early relaxation rather than by systolic function, suggesting that dynamic exercise training improves cardiac performance by an effect on diastolic filling.

Adult↗

PubMed2002

Estimation of global left ventricular function from the velocity of longitudinal shortening.

AIMS: To determine if global ventricular function can be assessed from the long-axis contraction of the left ventricle, we compared pulsed-wave Doppler myocardial imaging of mitral annular motion to radionuclide ventriculography. METHODS AND RESULTS: We studied 51 patients (56 +/- 10 years, 11 women) with a radionuclide ejection fraction of 52 +/- 13% (15%-70%). Peak systolic velocities of medial and lateral mitral annular motion correlated with ejection fraction (0.55 and 0.54, respectively; P < 0.001), as did the time-velocity integrals (0.57 and 0.58, respectively; P < 0.001). Correlations were higher in normal ventricles (0.62-0.69) than in patients with previous myocardial infarction (0.39-0.64). Patients with anterior myocardial infarction had the lowest correlations (0.39-0.46). The best differentiation of normal (> or = 50%) from abnormal (< 50%) ejection fraction was provided by peak systolic velocity > or = 8 cm/sec for the medial (sensitivity 80%, specificity 89%) or lateral (sensitivity 80%, specificity 92%) mitral annulus. CONCLUSION: Global left ventricular function can be estimated by recording mitral annular velocity. The implementation of a cutoff limit of 8 cm/sec gave a simple guide for differentiating between normal and abnormal left ventricular systolic function that might be useful clinically in patients without regional wall-motion abnormalities. However, in patients with important segmental wall-motion abnormalities during systole, left ventricular longitudinal shortening is an imperfect surrogate for ejection fraction.

Echocardiography, Doppler, Pulsed↗