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Biomedical subjects

M G Sutton

Publications and source records attributed to M G Sutton.

At least 19 recordsLinked to original sources
PubMed2001

Reappearance of myocytes in ovine infarcts produced by six hours of complete ischemia followed by reperfusion.

BACKGROUND: In this study we tested the hypothesis that delayed reperfusion of ischemic myocardium-too late to save myocytes-attenuates infarct expansion and improves collagen synthesis. METHODS: The hypothesis was tested in a sheep model of anteroapical infarction that has no collateral blood flow to the area at risk. After coronary ligation or arterial occlusion for 1 or 6 hours, sheep had serial hemodynamic and quantitative echocardiographic studies before and after infarction and 2, 5, 8, and 12 weeks later. Hearts were examined by light and electron microscopy at 2 and 12 weeks; hydroxyproline and ratios of type I/III collagen were measured at 12 weeks. RESULTS: After coronary occlusion, left ventricular (LV) function progressively decreased and size increased to form an anteroapical aneurysm. After 1 hour of ischemia, neither resting LV size nor function changed; the infarct contained a midmyocardial scar between epicardial and endocardial muscle. After 6 hours of ischemia, LV function was significantly better than that in nonperfused sheep. Two weeks after 6 hours of ischemia, no viable myocytes were visible by light microscopy, but electron micrographs showed rare intact nucleated myocytes with scarce cytoplasmic myofibrils. At the 12th week epicardial and endocardial myocytes reappeared in the infarct. Infarct collagen type I/III ratios were 1.2 in reperfused groups and 0.7 in nonperfused sheep. CONCLUSIONS: Delayed reperfusion causes loss and subsequent reappearance of ovine epicardial myocytes, improves collagen type I/III ratios, and attenuates LV dilatation and loss of function. One hypothesis to explain the reappearance of myocytes is that reperfusion partially reverses an incomplete apoptotic process.

Animals↗
PubMed2000

Bicuspid aortic valves are associated with aortic dilatation out of proportion to coexistent valvular lesions.

BACKGROUND: Bicuspid aortic valves (BAVs) are associated with premature valve stenosis, regurgitation, and ascending aortic aneurysms. We compared aortic size in BAV patients with aortic size in control patients with matched valvular lesions (aortic regurgitation, aortic stenosis, or mixed lesions) to determine whether intrinsic aortic abnormalities in BAVs account for aortic dilatation beyond that caused by valvular hemodynamic derangement alone. METHODS AND RESULTS: Diameters of the left ventricular outflow tract, sinus of Valsalva, sinotubular junction, and proximal aorta were measured from transthoracic echocardiograms in 118 consecutive BAV patients. Annular area was measured by planimetry, and BAV eccentricity was expressed as the ratio of the right leaflet area to the total annular area. Seventy-seven control patients with tricuspid aortic valves were matched for sex and for combined severity of regurgitation and stenosis. BAV patients (79 men and 39 women, aged 44.1+/-15.5 years) had varying degrees of regurgitation (84 patients [71%]) and stenosis (48 patients [41%]). Within the bicuspid group, multivariate analysis demonstrated that aortic diameters increased with worsening aortic regurgitation (P:<0.001) and advancing age (P:<0.05) but not with the severity of aortic stenosis. BAV patients had larger aortic diameters than did control patients at all ascending aortic levels measured (P:<0.01), despite advanced age in the control patients. CONCLUSIONS: Aortic dimensions are larger in BAV patients than in control patients with comparable degrees of tricuspid aortic valve disease. Although more severe degrees of aortic regurgitation are associated with aortic dilatation in BAV patients, intrinsic pathology appears to be responsible for aortic enlargement beyond that predicted by hemodynamic factors.

Adult↗
PubMed1997

Global cardiac function using fast breath-hold MRI: validation of new acquisition and analysis techniques.

Calculation of global cardiac function parameters has been validated using fast, segmented k-space, breath-hold, gradient-echo, magnetic resonance images. Images of phantoms, experimental animals, normal volunteers, and patients were acquired with a 1.5 T clinical scanner. Humans were imaged using two phased-array surface coils in multicoil mode. Myocardial contours were extracted using a new interactive, semi-automated method based on the active contour model method. Images were acquired in the short-axis orientation, and, using a new imaging and analysis strategy, in rotating plane long-axis orientations, to provide better definition of the valve planes and the apex, and also to reduce the number of slices (compared with the short-axis method) required to sample the whole heart. Validation was accomplished through calculation of the volumes of phantoms and left and right ventricular masses of animal hearts. Functional parameters from MRI were compared with those from echocardiograms and radionuclide angiograms in normal volunteers and patients, respectively.

Adult↗
PubMed1997

Distortions of the mitral valve in acute ischemic mitral regurgitation.

BACKGROUND: In the absence of papillary muscle rupture, the precise deformations that cause acute postinfarction mitral valve regurgitation are not understood and impair reparative efforts. METHODS: In 6 Dorsett hybrid sheep, sonomicrometry transducers were placed around the mitral annulus (n = 6) and at the tips and bases of both papillary muscles (n = 4). Later, specific circumflex coronary arteries were occluded to infarct approximately 32% of the posterior left ventricle and produce acute 2 to 3+ mitral regurgitation. Before and after infarction, distance measurements between sonomicrometry transducers produced three-dimensional coordinates of each transducer every 5 ms. RESULTS: After infarction, the annulus dilated asymmetrically orthogonal to the line of leaflet coaptation, but the annular area increased only 9.2% +/- 6.3% (p = 0.02). At end-systole, posterior papillary muscle length increased 2.3 +/- 0.9 mm (p = 0.005); the posterior papillary muscle tip moved closer to the annular plane and centroid, and the anterior papillary muscle tip moved away. CONCLUSIONS: Small deformations in mitral valvular spatial geometry after large posterior infarctions are sufficient to produce moderate to severe mitral regurgitation. The most important changes are asymmetric annular dilatation, prolapse of leaflet tissue tethered by the posterior papillary muscle, and restriction of leaflet tissue attached to the anterior papillary muscle.

Animals↗
PubMed1997

Diagnosis of a persistent coronary fistula after ventricular septal defect patch closure.

Penetrating chest trauma can result in multiple clinical syndromes depending on the structures involved. Tamponade, valvular regurgitation, ventricular septal defect (VSD), conduction system abnormalities, and coronary lacerations have been reported. We report a case of right ventricular free wall laceration, VSD, and coronary artery fistula involving a septal perforator.

Adult↗
PubMed1996

Venous thromboembolism: detection by duplex scanning.

PURPOSE: The usefulness of transcranial Doppler monitoring in identifying emboli in the arterial circulation has been established. We attempted to extend this technique to identify embolism in the venous circulation and to note any changes in embolism rate with anticoagulation. METHODS: From March to July 1993, 218 patients were evaluated by duplex scan for deep venous thrombosis. RESULTS: Sixty patients had positive study results; 26 scans (43%) demonstrated embolism. In five patients (19%) the emboli were also seen on a B-mode image, enabling us to estimate embolus size, which ranged from 200 to 5000 micrometer. Embolus counts varied from 5 to 800 per minute. Deep venous thrombosis was located in the iliofemoral vein in 2 patients, superficial femoral/profunda vein in 8, saphenofemoraal junction in 1, popliteal vein in 1, and the calf in 10. Concomitantly, studies in 158 patients were negative for deep venous thrombosis; embolism was detected in 4 patients (3%) in this group. In patients taking heparin, the embolus counts decreased 50% or more within 24 hours, and all embolism was abolished within 72 hours. Two patients died of pulmonary embolus. CONCLUSIONS: Patients with duplex scans that are positive for deep venous thrombosis have a high incidence of ongoing embolism. Heparin appears effective in eliminating the microemboli detected. The relationship among microembolism, deep venous thrombosis, and clinically significant pulmonary embolism remains to be elucidated.

Femoral Vein↗
PubMed1994

Muscular false tendons, aberrant left ventricular papillary musculature, and severe electrocardiographic repolarisation abnormalities: a new syndrome.

Three patients (age 18-39 years; two men) with normal exercise capacity, normal left ventricular function, large muscular false tendons within the left ventricle, and anomalously placed papillary muscles associated with giant T wave inversion on the electrocardiogram are described. The absence of adverse cardiovascular events at long-term follow up (mean 13 years) indicates that this is a benign unrecognised syndrome.

Adult↗
PubMed1993

Magnetic resonance jet velocity mapping in mitral and aortic valve stenosis.

BACKGROUND: Magnetic resonance (MR) phase-shift velocity mapping is an established method for measurement of nonturbulent intravascular flow. Shortening the echo time of the MR sequence to 3.6 msec allowed application of the technique to turbulent jet flow. The objective of this study was validation of MR jet velocity mapping in patients with cardiac valve stenosis. METHODS AND RESULTS: We used a 0.5-T Picker MR machine to measure peak poststenotic jet velocity in 15 consecutive patients recruited with known valve disease (six mitral stenosis, three of these restudied after valvoplasty, and 11 aortic stenosis). On the same day as the MR study, these patients underwent independent Doppler echocardiographic measurement of peak jet velocity. The results of 10 further MR investigations of aortic stenosis are also reported and compared with Doppler studies performed within 6 months. Of the 29 MR studies, 28 (97%) produced interpretable velocity maps, the one failure being attributed to misplacement of the imaging slice in a case of severe aortic stenosis. Agreement between MR and Doppler measurements of peak jet velocity in the recruited group was as follows: n = 18; range, 1.4-6.1 m/sec; mean, 3 m/sec; mean of differences (MR-Doppler), 0.23 m/sec; standard deviation of differences, 0.49 m/sec. CONCLUSIONS: In vivo MR peak jet velocity measurements agree well with those made by Doppler ultrasound. The technique, which is not subject to restricted windows of access and has potential for further refinements, could contribute to improved evaluation of stenoses, especially at locations where ultrasonic access is limited.

Aortic Valve Stenosis↗
PubMed1991

Doppler echocardiographic study of porcine bioprosthetic heart valves in the aortic valve position in patients without evidence of cardiac dysfunction.

To study the natural history of the hemodynamic performance of bioprosthetic heart valves, Doppler echocardiograms were recorded in a group of clinically stable patients at 2 and 5 years after replacement of native aortic valves with bioprosthetic valves. Eighteen patients completed a 2-year and 26 patients a 5-year follow-up examination. The effective orifice areas of identical models of bioprosthetic valves (Hancock II) were determined in vitro in a left-sided heart pulse duplicator system. In vivo Doppler-derived effective orifice areas were compared with the in vitro measurements for the same valve size. At both the 2- and 5-year follow-up examinations, the Doppler-derived effective orifice area was significantly less than the in vitro area (p less than 0.0001 at each interval). Ten of 16 valves evaluated serially decreased greater than 0.20 cm2 in the Doppler-derived effective orifice area between studies. The mean decrease in effective orifice area in valves evaluated serially was 0.25 +/- 0.29 cm2 (p less than 0.005). The peak transaortic gradient increased from 21 +/- 6 to 27 +/- 8 mm Hg (p less than 0.01). The mean transaortic gradient increased from 12 +/- 4 to 15 +/- 7 mm Hg (p less than 0.05). It is concluded that serial Doppler echocardiographic studies demonstrate a deterioration in the hemodynamic performance of bioprosthetic valves over time in patients with no symptoms or signs of valvular dysfunction and that Doppler echocardiography may be useful for identifying subclinical bioprosthetic valvular dysfunction.

Adult↗
PubMed1991

Relationship between placental blood flow and combined ventricular output with gestational age in normal human fetus.

STUDY OBJECTIVE: The aim was to quantify the changes in placental blood flow and combined ventricular output with gestational age in normal human fetuses to determine the percentage of total cardiac output that placental blood flow represented, and whether this changed with age. DESIGN: Two dimensional echocardiographic images of the umbilical vein, the proximal aorta and proximal main pulmonary artery were obtained, and cross sectional areas calculated from vessel diameters. Doppler velocity signals were recorded from each vessel and digitised to obtain velocity-time integrals. Placental blood volume flow and combined ventricular output were calculated as the products of flow velocity time integrals and cross sectional areas of the umbilical vein, and of the great arteries respective. SUBJECTS: Subjects were 64 normal human fetuses aged between 20 and 42 weeks gestation. MEASUREMENTS AND MAIN RESULTS: Placental flow and combined ventricular output both increased exponentially with gestational age (r = 0.79, and r = 0.84; both p less than 0.001). Placental flow correlated linearly with combined ventricular output (r = 0.69; p less than 0.01) and comprised almost one third of total cardiac output throughout the second and third trimesters. CONCLUSIONS: These data describe the relationship between placental blood flow and combined ventricular output with age in the normal human fetus and provide a substrate by which placental insufficiency and resulting intrauterine growth retardation may be recognised early.

Cardiac Output↗
PubMed1990

Assessment of the hemodynamic response to acetyl-strophanthidin by Doppler echocardiography in normal subjects and in those with coronary artery disease or idiopathic dilated cardiomyopathy.

The effect of acetyl-strophanthidin, a rapidly acting digitalis-like drug, was measured on peak flow velocity, stroke distance (an index of stroke volume) and minute distance (an index of cardiac output), determined by Doppler echocardiography in 21 subjects with a wide range of left ventricular ejection fractions (12 to 89%, average 47%). For the total study group, peak flow velocity increased from 99 +/- 10 to 110 +/- 13 cm/s (p less than 0.01), and stroke distance increased from 15.1 +/- 3.2 to 16.8 +/- 3.1 cm (p less than 0.01). Minute distance remained unchanged: 1,093 +/- 168 cm before and 1,129 +/- 187 cm after acetyl-strophanthidin (difference not significant). Improvement in Doppler parameters of forward blood flow was significantly (p less than 0.001) greater in subjects with left ventricular ejection fractions less than 60% (+17% for peak flow velocity, +22% for stroke distance and +15% for minute distance) than those with left ventricular ejection fractions greater than or equal to 60% (+4% for peak flow velocity, +2% for stroke distance and -8% for minute distance). These data suggest that Doppler echocardiography is a useful method to assess the efficacy of acute digitalis administration in improving forward blood flow.

Blood Flow Velocity↗
PubMed1990

Endothelium-dependent dilation of the coronary microvasculature is impaired in dilated cardiomyopathy.

Dilator reserve of the coronary microvasculature is diminished in patients with dilated cardiomyopathy. Although increased extravascular compressive forces, tachycardia, and increased myocardial mass can explain some impairment, recent evidence suggests the possibility of intrinsic microvascular disease. We tested the hypothesis that impairment of endothelium-dependent dilation of the microvasculature could be a contributing mechanism. We infused the endothelium-dependent dilator acetylcholine (Ach) (10(-8) to 10(-6) M) and the smooth muscle vasodilator adenosine (AD) (10(-6) to 10(-4) M) into the left anterior descending coronary artery in eight patients with dilated cardiomyopathy (mean ejection fraction, 28%) and seven controls (atypical chest pain). Small vessel resistance was assessed by measuring coronary blood flow (CBF) at constant arterial pressure with a Doppler velocity catheter (corrected for cross-sectional area by angiography). With Ach, control patients increased CBF 232 +/- 40% (mean +/- SEM), whereas CBF did not significantly change in cardiomyopathy patients (41 +/- 24%) (p less than 0.0001, control vs. cardiomyopathy). With AD, control patients increased CBF 422 +/- 56% and cardiomyopathy patients increased CBF 268 +/- 43% (p = 0.13). An index of the proportion of coronary flow reserve attributable to endothelium-dependent vasodilation was obtained by standardizing each patient's Ach dose response to his maximal AD flow response. In seven control patients receiving both Ach and AD, 56 +/- 9% of the maximal AD flow response was attained with the endothelium-dependent vasodilator Ach, whereas in seven cardiomyopathy patients receiving both Ach and AD, only 23 +/- 14% of the maximal AD response was attained (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1990

Coronary atherosclerosis is associated with left ventricular dysfunction and dilatation in aortic stenosis.

Patients with aortic stenosis develop widely variable patterns of left ventricular hypertrophy and dysfunction. We postulated that coronary atherosclerosis (CAD) may be associated with impaired left ventricular function and chamber dilatation in patients with aortic stenosis. Left ventricular mass and volumes were quantified from two-dimensional echocardiography and correlated with coronary angiography in 78 patients with severe aortic stenosis and no previous myocardial infarction or regional wall motion abnormalities. Eighteen patients (group 1) had smooth coronary arteries, 25 patients had irregular coronary arteries with 50% or less stenosis (group 2), and 35 patients had obstructive CAD (group 3). Even though the calculated valve area was similar in all three study groups, group 1 patients had higher values for ejection fraction (65 +/- 9%, 51 +/- 17%, and 48 +/- 13%; p = 0.0002), systolic mass-to-volume ratio (9.2 +/- 3.9, 5.6 +/- 2.8, and 5.2 +/- 2.2; p = 0.0001), and cardiac index (2.9 +/- 0.7, 2.5 +/- 0.7, and 2.3 +/- 0.6 l/min.min2; p = 0.015) than patients in groups 2 and 3, respectively (mean +/- SD). Mean circumferential wall stress was inversely related to severity of CAD. Multivariate analysis showed that CAD is an independent predictor of ejection fraction and mass-to-volume ratio in this group of patients. Thus, in an elderly population with severe aortic stenosis, patients with both obstructive and nonobstructive CAD have an increased incidence of left ventricular enlargement and systolic dysfunction.

Aged↗