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Biomedical subjects

W J Manning

Publications and source records attributed to W J Manning.

At least 145 records · Page 8Linked to original sources
PubMed1992

Two-dimensional and Doppler echocardiographic determinants of the natural history of mitral valve narrowing in patients with rheumatic mitral stenosis: implications for follow-up.

Fifty patients with rheumatic mitral stenosis were studied with serial two-dimensional and Doppler echocardiography to determine the natural history of changes in mitral valve area and its relation to transmitral gradients and mitral valve morphology. Over the 39-month observation period (range 7 to 74 months) the decline in valve area was 0.09 +/- 0.21 cm2/year. In addition, there were significant increases in total echocardiographic score (p = 0.0001), severity of mitral anulus calcification (p = 0.05) and severity of mitral regurgitation (p = 0.0007). Patients with an echocardiographic score greater than or equal to 8 had a more progressive course. In addition, patients with a more progressive course (decline in valve area greater than or equal to 0.1 cm2/year) had a significantly greater initial mean gradient (p = 0.01), peak gradient (p = 0.007) and total echocardiographic score (p = 0.0008). Initial valve area did not correlate with the rate of stenosis progression. Of 22 patients with an echocardiographic score less than 8 and a peak mitral gradient less than 10 mm Hg, only 1 patient (5%) had a more progressive course, compared with 80% of those with a total echocardiographic score greater than or equal to 8 and a gradient greater than or equal to 10 mm Hg. The rate of mitral valve narrowing in individual patients with rheumatic mitral stenosis is variable. Patients whose valve disease progresses rapidly are those with a greater mitral valve echocardiographic score and higher peak and mean transmitral gradients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Enhanced left ventricular diastolic filling associated with long-term endurance training.

Normal aging is associated with an impairment in early left ventricular diastolic filling. To test the hypothesis that long-term endurance exercise training is associated with enhanced ventricular diastolic filling indices, we compared transmitral pulsed Doppler inflow spectra in healthy young adults; healthy elderly, sedentary subjects (sedentary old); and healthy elderly, endurance athletes (master athletes). Our data demonstrate that, despite an increase in left ventricular mass, early diastolic filling was enhanced in master athletes compared to the sedentary old. Blood pressure of both master athletes and the sedentary olds was greater than the young adults, but the higher blood pressure did not correlate to changes in filling parameters. Resting systolic function and heart rate were not significantly different in all three different groups. Early left ventricular filling indices in master athletes more closely resemble transmitral inflow patterns of healthy young adults. Long-term endurance exercise is associated with physiologic hypertrophy and ventricular filling dynamics more characteristic of the young than the old.

Adult↗
PubMed1992

Use of transoesophageal echocardiography to detect left atrial thrombi before percutaneous balloon dilatation of the mitral valve: a prospective study.

OBJECTIVE: Systemic emboli related to atrial thrombi are a well known complication of percutaneous balloon dilatation of the mitral valve. The presence of left atrial thrombi therefore, is believed to be a contraindication to balloon dilatation. The purpose of this study was to determine the frequency of left atrial thrombi in patients referred for balloon dilatation of the mitral valve, the added benefit of pre-procedural transoesophageal echocardiography, and to identify factors that predicted left atrial thrombi. DESIGN: Prospective study over a 14 month period of 20 consecutive patients by cross sectional transthoracic echocardiography 24-48 hours before balloon dilatation of the mitral valve and by transoesophageal echocardiography immediately before the procedure. RESULTS: One patient had a left atrial thrombus detected by transthoracic study. Two patients (10%) had left atrial thrombi identified by transoesophageal echocardiography. In both valve dilatation was not attempted and the thrombi were confirmed at surgery. The remaining 18 patients all underwent successful balloon dilatation of the mitral valve without clinical evidence of an embolic event. No association was found between patient age, mitral valve area, transmitral gradient, left atrial size, presence of atrial fibrillation, severity of mitral regurgitation, cardiac output, or the presence of left atrial swirling and an increased prevalence of atrial thrombi. CONCLUSION: Left atrial thrombi are often seen despite long term systemic anticoagulation in patients referred for balloon dilatation of the mitral valve. The frequency of unsuspected left atrial thrombi detected by transoesophageal echocardiography was similar to the reported frequency of embolic events after balloon dilatation of the mitral valve. Transoesophageal echocardiography for the identification of left atrial thrombi is strongly recommended in all patients before balloon dilatation of the mitral valve including those treated with systemic anticoagulation and those who have had a normal transthoracic echocardiographic study.

Adult↗
PubMed1992

Remnant of the common pulmonary vein mistaken for a left atrial mass: clarification by transoesophageal echocardiography.

Faulty incorporation of the common pulmonary vein leaves it as a distinct structure posteriorly, into which the pulmonary veins empty. This "chamber" is separated from the anterior "fetal" left atrium (containing the left atrial appendage and communicating with the mitral valve) by a diaphragm, and is known as cor triatriatum, one of the rarest of cardiac malformations. Less pronounced but still incomplete regression of this vein would result in the persistence of a portion of the common pulmonary vein appearing as a mass along the lateral wall of the left atrium at the junction of the left atrial appendage and left upper pulmonary vein. In two patients, both referred for evaluation of a left atrial mass, transoesophageal echocardiography identified the "mass" as a remnant of the common pulmonary vein. Cardiologists need to be aware of this structural remnant and its possible variants so as to avoid misdiagnosis of this prominence as an atrial tumour or mass.

Aged↗
PubMed1992

Assessment of intracardiac shunts with gadolinium-enhanced ultrafast MR imaging.

Dye dilutional techniques are widely accepted for the assessment of intracardiac shunts, but current techniques require arterial access or radioisotope injection. Ultrafast (less than 500 msec) magnetic resonance (MR) imaging is ideally suited for the evaluation of an indicator during passage through the heart. Twenty patients were studied, including 13 with shunts. Four-chamber, T1-weighted images were obtained during bolus injection of gadopentetate dimeglumine. A single image was obtained in 420 msec, with repetitive images acquired after each QRS complex. After the contrast material was injected, there was pronounced signal intensity enhancement in the right atrium, followed by the right ventricular cavity, left atrium, left ventricular cavity, and descending aorta. Patients with substantial intracardiac shunts demonstrated early recirculation. First-pass contrast material-enhanced MR imaging is a promising new technique for the rapid assessment of intracardiac shunts. Combined with anatomic and functional MR imaging techniques, it can help provide a comprehensive noninvasive evaluation of suspected intracardiac shunts or provide follow-up in patients with known shunts.

Adult↗
PubMed1991

Factors in myocardial "perfusion" imaging with ultrafast MRI and Gd-DTPA administration.

Ultrafast magnetic resonance imaging (MRI) and first pass observation of an interstitial contrast agent are currently being used to study myocardial perfusion. Image intensity, however, is a function of several parameters, including the delivery of the contrast agent to the interstitium (coronary flow rate and diffusion into the interstitium) and the relaxation properties of the tissue (contrast agent concentration, proton exchange rates, and relative intra- and extracellular volume fractions). In this study, image intensity during gadopentetate dimeglumine (Gd-DTPA) administration with T1-weighted ultrafast MR imaging was assessed in an isolated heart preparation. With increasing Gd-DTPA concentration, the steady-state myocardial image intensity increased but the time to reach steady state remained unchanged, resulting in an increased slope of image intensity change. A range of physiologic perfusion pressures (and resulting coronary flow rates) had insignificant effects on kinetics of Gd-DTPA wash-in or steady-state image intensity, suggesting that diffusion of Gd-DTPA into the interstitium is the rate limiting step in image intensity change with this preparation. Following global ischemia and reperfusion, transmural differences in the slope of image intensity change were apparent. However, the altered steady-state image intensity (due to postischemic edema) makes interpretation of this finding difficult. The studies described here demonstrate that although Gd-DTPA administration combined with ultrafast imaging may be a sensitive indicator of perfusion abnormalities, factors other than perfusion will affect image intensity. Extensive studies will be required before image intensity with this protocol is fully understood.

Animals↗
PubMed1991

First-pass nuclear magnetic resonance imaging studies using gadolinium-DTPA in patients with coronary artery disease.

Nuclear magnetic resonance (NMR) imaging has been shown to accurately portray cardiac anatomy and function. To investigate the potential of NMR imaging for the assessment of coronary stenosis in patients with chest pain, ultrafast NMR imaging in conjunction with a T1 (longitudinal relaxation time) contrast agent was performed in 17 patients with chest pain who had undergone cardiac catheterization. These included 12 patients with significant coronary artery stenoses and 4 who underwent repeat NMR study after myocardial revascularization. Cardiac images at rest were obtained during rapid intravenous injection of gadolinium-DTPA (0.04 mM/kg). Electrocardiographic-gated images were acquired over 380 ms, with repetitive images obtained every 3 to 4 s. After contrast injection, there was pronounced signal enhancement in the right ventricular cavity, followed by enhancement in the left ventricular cavity and myocardium. Regional myocardium perfused by a diseased vessel demonstrated a lower peak signal intensity (p = 0.001) and lower rate of signal increase (p = 0.001) than did myocardium perfused by coronary arteries without stenosis. Repeat NMR study after revascularization showed an increase in peak signal intensity (p less than 0.002). These results demonstrate the clinical potential of dynamic gadolinium-DTPA-enhanced NMR imaging for the assessment of coronary artery disease in patients with chest pain. In combination with anatomic and functional NMR imaging, this technique has the potential to provide a comprehensive noninvasive cardiac evaluation of patients with suspected coronary artery disease.

Adult↗
PubMed1991

Coronary arteries: breath-hold MR angiography.

The authors describe a method for performance of ultrafast magnetic resonance (MR) angiography of coronary arteries with a standard clinical MR system and a body coil. Each image was obtained within a single breath hold by using an electrocardiography-gated, segmented, ultrafast, gradient-echo pulse sequence with an incremental excitation flip angle for the eight phase-encoding steps acquired per segment. By using overlapping 4-mm-thick sections, the coronary arteries were routinely depicted from the coronary ostia distally at MR in healthy subjects. Ultrafast MR angiography of the coronary arteries is feasible with use of a standard body coil. This technique offers considerable potential as an investigational tool and, with further development, may become a clinically useful imaging application.

Adult↗
PubMed1990

Measurement of left ventricular mass in rats using electrocardiogram-gated magnetic resonance imaging.

To evaluate the ability of electrocardiogram (ECG)-gated magnetic resonance (MR) imaging to assess in vivo left ventricular (LV) mass in the rat, we studied 20 healthy adult Sprague-Dawley and Fischer 344 rats and 8 additional rats that underwent scanning after induction of volume overload by aortic leaflet disruption. ECG-gated spin-echo pulse sequences were used to acquire a series of 1-mm thick modified short-axis images of the left ventricle. The area enclosed by the endocardial and epicardial borders of the left ventricle was multiplied by the interslice distance and specific gravity of myocardium to obtain calculated slice mass. Total LV mass was obtained by summing the individual slices. The calculated value for LV mass was then compared with the LV mass as determined at postmortem examination. Linear regression analysis showed an excellent correlation of MR-estimated mass (x) with autopsy-measured LV mass (y) (y = 0.90x + 65, r = 0.98). For this method intraobserved and interobserver slice correlations were 0.97 and 0.96, respectively. There was no significant difference in LV mass as determined from a series of diastolic vs. systolic images in a subset of six animals. Over a mean of 6.5 wk of observation, LV mass increased by 40% in the animals subjected to aortic leaflet disruption. These results demonstrate that MR imaging is highly accurate for the non-invasive in vivo assessment of LV mass in the adult rat.

Animals↗
PubMed1989

Pulsed Doppler evaluation of atrial mechanical function after electrical cardioversion of atrial fibrillation.

Full recovery of atrial mechanical activity may not occur immediately after successful electrical cardioversion of atrial fibrillation to sinus rhythm. To examine the time course of recovery of left atrial mechanical function, serial two-dimensional, M-mode and transmitral pulsed Doppler echocardiographic studies were performed in 21 patients after elective direct current cardioversion of atrial fibrillation of 3 weeks' to 24 months' duration (mean 5 months). Over 3 months of follow-up, there were significant increases in both peak A wave velocity (p less than 0.005) and percent atrial contribution to total left ventricular filling (p less than 0.005). Compared with values in a normal control population, peak A wave velocity and percent atrial contribution to total left ventricular filling did not return to normal until 3 weeks after cardioversion in patients who remained in sinus rhythm. Left atrial dimension also decreased over the follow-up period (p less than 0.05) in patients with persistent sinus rhythm. These results may have important implications in guiding the appropriate duration of anticoagulant therapy after cardioversion, and in clinically assessing the hemodynamic benefit of restoring sinus rhythm in an individual patient.

Aged↗
PubMed1989

Pulsed Doppler echocardiographic determination of the time course of left ventricular filling: validation with cineangiography.

Several noninvasive techniques are used to evaluate left ventricular diastolic function, but none has optimally characterized the time course of left ventricular filling. We have developed a method to characterize left ventricular filling, by integrating Doppler measurements of flow velocity across the mitral valve. The purpose of the present study was to compare this new method with contrast left ventriculographic assessment of left ventricular filling. Pulsed Doppler studies were obtained within 24 hours of left ventriculography in 15 patients: three normal subjects, seven with coronary disease, two with mitral stenosis, and three with dilated cardiomyopathy. Patients with myocardial infarction, regional wall movement abnormalities, or aortic regurgitation were excluded. Doppler-derived relative left ventricular filling was compared to filling from right anterior oblique left ventriculograms. Doppler and angiographic filling curves were qualitatively different in normal subjects and in patients with mitral stenosis and cardiomyopathy. For individual patients, however, the Doppler and angiographic filling curves were qualitatively similar, with a strong correlation between Doppler and angiographic estimates of percent filling (r = 0.95; p less than 0.001). These preliminary observations suggest that Doppler echocardiography may provide a reliable assessment of the time course of left ventricular diastolic filling. Further studies are warranted and should include more patients with diverse cardiac abnormalities.

Adult↗
PubMed1988

Ozone effects on growth and assimilate partitioning in alfalfa, Medicago sativa L.

Alfalfa (Medicago sativa L.) were exposed to O(3) concentrations varying between 118 x 10(-6) microg cm(-3) (0.06 ppm) and 157 x 10(-6) microg cm(-3) (0.08 ppm) for 6 h per day 5 days per week for several weeks. Typical plants were sacrificed weekly, and growth parameters were measured. O(3) reduced overall growth, relative growth rates and unit leaf rates in alfalfa before it was cut, indicating that O(3) had reduced photosynthesis. However, after the alfalfa was cut, these same parameters indicated that in some cases, O(3)-stressed plants had greater photosynthetic rates than controls during regrowth. O(3) also altered dry matter partitioning. Roots were most affected, followed by leaves and stems, respectively. In general, O(3) reduced photosynthate production and reduced the proportion of photosynthate partitioned to roots relative to leaves and stems. This could reduce starch reserves in alfalfa, and be detrimental to stand longevity. However, the post-cutting study indicated that at least some alfalfa cultivars may be able to acclimate to O(3)-stress, though plants did not fully recover from pre-cutting differences.

Journal Article↗
PubMed1988

Effects of ozone and simulated acid rain on birch seedling growth and formation of ectomycorrhizae.

Four-week-old paper birch (Betula papyrifera Marsh.) seedlings, inoculated or non-inoculated with the ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker & Couch and grown in steamed or non-steamed soil, were exposed to ozone (O(3)) and/or simulated acid rain (SAR). Plants were exposed to O(3) for 7 h per day on 5 days per week for 12 weeks. O(3) concentrations were maintained between 0.06 and 0.08 ppm. SAR was applied 10 min per day on 2 days per week. O(3), SAR, soil regime and mycorrhizal treatment did not significantly affect any of the measured variables. Interactions between O(3) and SAR, SAR and mycorrhizal treatment, soil regime and mycorrhizal treatment and ozone and soil regime had significant effects. Treatment of seedlings with pH 3.5 SAR caused increases in growth which were more apparent in birch exposed to O(3). Mucorrhizal treatment caused increased growth in non-steamed soil, while growth appeared to decrease in steamed soil. Birch seedlings grew much better in steamed soil. The implications of increased growth in steamed soil may demonstrate the importance of looking at the secondary effects of pollutants on soil-borne organisms.

Journal Article↗
PubMed1988

Atmospheric ozone: formation and effects on vegetation.

Ozone (O(3)) is present both in the troposphere and the stratosphere. Troposphere O(3) is predominantly produced by photochemical reactions involving precursors generated by natural processes and to a much larger extent by man's activities. There is evidence for a trend towards increasing tropospheric O(3) concentrations. However, tropospheric O(3) is known to account for only 10% of the vertical O(3) column above the earth's surface. The stratosphere accounts for an additional 90% of the O(3) column. There is evidence to suggest that there are losses in the stratospheric O(3) due to the updraft of O(3) destroying pollutants generated by both natural processes and by human activity. Such a loss in stratospheric O(3) can result in alterations of incidence in the ultraviolet (UV) radiation to the earth's surface. Tropospheric O(3) is known to be highly phytotoxic. Appropriate exposures to O(3) can result in both acute (symptomatic) and chronic (changes in growth, yield or productivity and quality) effects. Chronic effects are of great concern in terms of both crops and forests. A number of experimental techniques are available to evaluate the chronic effects of O(3) on plants. There are limitations attached to the use of these techniques. However, results obtained, with such techniques are valuable if interpreted in the appropriate context. Among all field evaluation techniques, open-top chambers are the most frequently used method for evaluating the chronic effects of O(3) on crops. The National Crop Loss Assessment Program (NCLAN) of the United States is the largest such effort. However, given the limitations of the open-top chambers and the experimental aspects of NCLAN, its results must be interpreted with caution. On the other hand, acute effects can be evaluated with less complexity through the use of biological indicator plants. The numerical modelling of such effects are also far less complicated than establishing numerical cause and effects relationships for chronic effects. Confounding the acute or chronic responses of plants to O(3), is the presence of other kinds and forms of pollutants in the ambient atmosphere and the incidence of pathogens and pests. The resulting complex interactions and joint effects on plants are poorly understood. Future research must address these issues. In the final analysis we have re-emphasized the fact that plant health is the product of its interaction with the physical and chemical climatology and pathogens and pests. What we have described in this context is the importance of tropospheric O(3) within the chemical climatology of our environment and its effects on vegetation.

Journal Article↗
PubMed1987

The impact of ozone on assimilate partitioning in plants: a review.

Numerous studies have shown that ozone (O(3)) reduces plant growth and changes assimilate partitioning. The pattern of such changes varies with species, but trends suggest a comprehensive model. O(3) generally reduces the amount of dry matter in the whole plant. In plants which have not flowered or set fruit, and at low O(3) levels, the remaining available assimilate is generally diverted to leaves and stems at the expense of roots and crowns. As the plant matures, flowers and develops seeds, these sinks receive a relatively high proportion of the available assimilate. O(3) may reduce the number of flowers or seeds, but the remaining seeds often have a total dry matter accumulation comparable to that in non-stressed plants. At higher O(3) levels, assimilate accumulation is greatly depressed, and partitioning changes are not as obvious. However, it is significant that the storage organs of plants-those organs which supply energy for new growth in perennial plants such as trees-are the organs most affected by O(3)-induced partitioning changes when O(3) concentrations are in the range commonly observed in polluted ambient air.

Journal Article↗