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Biomedical subjects

M S Sutton

Publications and source records attributed to M S Sutton.

At least 55 records · Page 3Linked to original sources
PubMed1987

The effect of chronic pulmonary hypertension on left ventricular size, function, and interventricular septal motion.

The effect of right ventricular pressure overload secondary to chronic pulmonary arterial hypertension on left ventricular size and function and on interventricular septal motion was studied in 13 patients in whom coronary artery disease, hypertension, and hypoxemia were excluded. Regional and global left ventricular function were assessed by computer-assisted analysis of two-dimensional directed M-mode echocardiograms obtained within 24 hours of a hemodynamic study. Septal position and motion were further analyzed by delineating seven points along the right and left sides of the septum during a single cardiac cycle. All echocardiographic data were compared to those of 10 normal subjects. Mean values for right ventricular systolic, mean pulmonary artery and pulmonary capillary wedge pressures were: 71 +/- 26 mm Hg, 46 +/- 16 mm Hg, and 7 +/- 1 mm Hg, respectively. Septal motion was interpreted from the M-mode echocardiograms as normal in seven patients (group I) and abnormal in the remaining six patients (group II). The only hemodynamic parameter which distinguished these two patterns was delta P, the transseptal systolic pressure gradient across the interventricular septum, which was significantly different (p less than 0.02) in group I (delta P = 65 +/- 16 mm Hg) from that of group II (delta P = 21 +/- 24 mm Hg). As a result of abnormal septal position, the septal-free wall dimensions of the left ventricle were reduced, but there was no evidence of depressed left ventricular performance in these patients. We conclude that resting left ventricular function is well preserved in patients with pulmonary hypertension, despite significant alterations in septal position and left ventricular size.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Unreliability of hemodynamic indexes of left ventricular size during cardiac surgery.

Pulmonary artery diastolic (PADP) and wedge pressures (PAWP) and left ventricular end-diastolic pressure (LVEDP) are commonly used to estimate left ventricular (LV) preload. To assess the ability of hemodynamic indexes of preload to estimate anatomical preload, or LV volume, we studied 45 patients during a coronary (18 patients) or aortic valve (27 patients) procedure and compared epicardial two-dimensional echocardiographic LV cavity area with simultaneous measurements of PADP, PAWP, and high-fidelity LVEDP. Pulmonary artery diastolic pressure, PAWP, and their percent change after bypass did not correlate with absolute values (before or after bypass) or percent change in LVEDP. Percent change in LV area correlated weakly with percent change in PADP (r = .34, p less than .03) but not with changes in PAWP or LVEDP. Changes were opposite in direction in 45% (PADP), 50% (PAWP), and 67% (LVEDP) of patients. In conclusion, both PADP and PAWP were poor guides to LVEDP and neither reflected changes in LV size. Thus, hemodynamic indexes of preload should be used with caution during cardiac operations.

Adult↗
PubMed1987

Mechanisms of action of diltiazem in isolated human atrial and ventricular myocardium.

A comparative study of human atrial fibers (HAF), human ventricular fibers (HVF), frog ventricle, and frog skeletal muscle demonstrated marked differences in tension development in the presence of diltiazem. There was no significant difference between the tension developed by HAF and by HVF over a range of diltiazem concentrations when the differences in resting membrane potential were corrected by increasing external K+ concentration. In human myocardium, diltiazem resulted in both a voltage and use-dependent blockade of the calcium channel. Comparison of the tension-dose response curves in human myocardium, frog ventricle and skeletal muscle showed that diltiazem was most effective at decreasing tension in frog heart, and least effective in skeletal muscle with human myocardium being intermediate. In skeletal muscle, neither tension development nor the birefringence signal related to the Ca2+ release from the sarcoplasmic reticulum was significantly altered by Diltiazem in concentrations less than 10(-6) M, but in concentrations greater than 10(-5) M both were suppressed. Diltiazem suppressed tension in human myocardium over the range of membrane potentials associated with Ca2+ channel activity, while at more positive potentials, diltiazem appeared to have little effect on the tension-voltage relations. Diltiazem had no effect upon tension development induced by acetyl strophanthidin in human myocardium or upon the Ca2+ sensitivity of chemically skinned atrial or ventricular fibers. Thus the tension-suppressant effect of diltiazem in human myocardium appears to be mediated by a combination of voltage-dependent block of the Ca2+ channel and inhibition of Ca2+ release from internal stores, and not from alterations in either Na+-Ca2+ coupled transport or Ca2+ sensitivity of the myofilaments.

Adolescent↗
PubMed1987

The normal diameter of the fetal aorta and pulmonary artery: echocardiographic evaluation in utero.

Measurements of the fetal aorta and pulmonary artery can aid in the detection and diagnosis of congenital heart defects. In a prospective study of 403 normal fetuses whose gestational ages were between 14 and 42 weeks, two-dimensional (2D) real-time and M-mode echocardiography were used to measure the diameters of the aortic root and the pulmonary artery in utero. The goals were to establish norms for the diameters of these structures as a function of both gestational age and biparietal diameter, to compare measurements obtained in systole and diastole, and to compare 2D and M-mode measurements. A high correlation was found between measurements made during systole and diastole (r = .994 for aorta, r = .996 for pulmonary artery) and between 2D and M-mode measurements for each vessel (r = .992 for aorta, r = .973 for pulmonary artery). The differences between systolic and diastolic measurements and between M-mode and 2D measurements were small (2.2-4.6%) for both the aorta and the pulmonary artery. The norms established here provide an objective standard for comparison when a cardiac anomaly involving a fetal aorta or pulmonary artery of abnormal size is suspected. The results indicate that a sonographic facility need not have M-mode equipment to obtain technically adequate measurements.

Aorta↗
PubMed1986

Effects of nitroglycerin in patients with angina, normal coronary arteries, and left ventricular hypertrophy.

The coronary hemodynamic and left ventricular mechanical responses to nitroglycerin were studied in eight patients with angina, normal coronary arteries, and pressure overload left ventricular hypertrophy (POLVH) and in five control subjects. Elevated mean and end-diastolic pressure and end-diastolic meridional stress characterized the POLVH group, although systolic meridional stresses were not significantly different from the control group. Thermodilution coronary sinus flow and estimated myocardial oxygen consumption declined significantly following nitroglycerin in both patient groups. Systolic and diastolic mechanical loads also decreased in both groups, although diastolic tone remained elevated in the patients with POLVH. The decrease in coronary sinus flow in the POLVH group was in excess of that expected from the decrease in systolic mechanical load, which suggests a combination of perfusion pressure-dependent decreases in coronary flow as well as an increased resistance to coronary inflow in these patients. The beneficial clinical response to nitroglycerin may reflect the lowered myocardial metabolic demand as well as the decrease in diastolic myocardial tensile and compressive forces.

Adult↗
PubMed1985

Relative wall thickness analysis by two-dimensional echocardiography.

M-mode echocardiographic relative wall thickness (RWT) has been used extensively as an index of left ventricular hypertrophy. To determine whether the more extensive tomographic sampling and enhanced spatial orientation provided by two-dimensional echocardiography (2DE) might improve the value of RWT analysis, we compared 2DE and M-mode RWT in 69 subjects (19 normals, 13 with aortic stenosis, 22 with aortic regurgitation, and 15 with congestive cardiomyopathy). M-mode results correlated relatively weakly with 2DE RWT (r = 0.62 at end diastole; r = 0.81 at end systole). End-systolic M-mode values were larger than 2DE results, while end-diastolic M-mode values were generally smaller than 2DE results (both p less than 0.001). Thus, in congestive cardiomyopathy M-mode RWT was larger than 2DE end-diastolic results and therefore failed to distinguish between cardiomyopathy, aortic regurgitation, and normals. We conclude that M-mode and 2DE analysis of RWT yield disparate results. Moreover, 2DE may enhance the value of RWT in the assessment of left ventricular hypertrophy due to volume overload and cardiomyopathy.

Adolescent↗
PubMed1984

Left ventricular mechanics in dilated cardiomyopathy.

The influence of altered chamber shape on the evaluation of left ventricular (LV) mechanics in idiopathic dilated cardiomyopathy (IDC) is unknown. Nine patients with IDC and 7 subjects with normal LV function were studied with simultaneous LV pressure and M-mode echographic recordings in order to derive LV meridional wall stress. The major axis of the left ventricle, determined from the left ventriculogram at rest, allowed for derivation of circumferential wall stress. The IDC group was characterized by larger end-diastolic and end-systolic LV volumes, increased LV mass, depressed angiographic ejection fraction and more spherical LV chamber shape. Both end-systolic meridional (114 +/- 30 kdyne/cm2) and circumferential (251 +/- 73 kdyne/cm2) wall stresses were elevated in patients with IDC, although the ratio of these stresses was less than normal (2.2 +/- 0.1 vs 2.7 +/- 0.2, respectively). LV load alteration with phenylephrine or nitroglycerin allowed for construction of end-systolic stress-minor-axis dimension and end-systolic stress-minor-axis shortening relations. Similar mean slopes of the meridional end-systolic stress-dimension relation were noted in IDC and normal subjects, although the line was displaced to the right in IDC. The slope of the circumferential end-systolic stress-dimension relation was, however, decreased in patients with IDC. Moreover, the end-systolic stress-fractional minor-axis shortening relation in patients with IDC was displaced downward from the normal relation supporting depressed contractile function in these IDC patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Antianginal effects of nitroglycerin patches.

Nitroglycerin (NTG) patches provide potentially therapeutic NTG blood levels for 24 hours, but their effects on exercise tolerance (ExT) in patients with angina have not been well characterized. Therefore, blinded, randomized trials were performed of the acute effects of both low-dose and maximal-tolerated-dose NTG patches and placebo on ExT in 14 patients with coronary artery disease and typical exertional angina. The bicycle exercise protocol of the National Institutes of Health was used and sublingual NTG administered as a positive control. In 7 subjects, low-dose patches produced no statistically significant effect on ExT at 4, 8 or 24 hours after administration. Comparable doses of sublingual and oral isosorbide dinitrate, NTG ointment and transmucosal NTG in previous studies have produced effects similar to those of conventional doses of sublingual NTG. Maximally tolerated doses of 2 types of NTG patches were then tested. The first (n = 8, mean NTG dose delivered 25 mg) produced increases in ExT of 82 and 72 seconds at 4 and 8 hours, respectively (both p less than 0.01), but was ineffective at 24 hours. The second patch type (n = 5, mean NTG dose delivered 22 mg) was also ineffective at 24 hours. Furthermore, even at maximal doses, peak effects on ExT were about half of those of sublingual NTG. Thus, NTG patches, even at maximal doses, appear to have smaller therapeutic effects than other long-acting nitrates and are ineffective at 24 hours. These results suggest rapid attenuation of NTG effect during prolonged maintenance of constant blood levels.

Administration, Topical↗
PubMed1984

Amrinone in the treatment of chronic cardiac failure.

The efficacy and safety of oral amrinone were examined in 17 patients with moderately severe to severe heart failure that was refractory to standard medical therapy and vasodilators. The short-term and 28 week response to open amrinone therapy was assessed first, followed by a placebo-controlled, double-blind withdrawal study of two 13 week stages in nine patients. Rest and exercise ventricular function were determined before and after 32 hours of amrinone; aerobic capacity was serially assessed. After 2 hours, 1.64 mg/kg amrinone produced a 40% (p less than 0.001) increase in cardiac output and a 32% (p less than 0.02) decrease in pulmonary wedge pressure without altering heart rate or blood pressure. The exercise cardiac index-wedge pressure curve obtained 32 hours after the first oral dose was significantly shifted (p less than 0.05) above control values. A sustained improvement in maximal oxygen uptake was noted during long-term open amrinone therapy. Subsequently, seven of the patients randomized to placebo therapy had a significant deterioration of symptoms or exercise tolerance, or both. After 4 weeks of readministration of amrinone, clinical stability was once again established and exercise tolerance was improved by Weeks 8 to 16. Adverse effects of thrombocytopenia (one patient) and hepatic dysfunction (one patient) attributable to amrinone were observed. It is concluded that amrinone is effective in the long-term treatment of chronic cardiac failure.

Aged↗
PubMed1983

Anatomic validation of left ventricular mass estimates from clinical two-dimensional echocardiography: initial results.

We performed a prospective anatomic validation study to determine the accuracy of left ventricular (LV) mass estimates from clinical two-dimensional echocardiographic (2-D echo) studies. In 21 subjects, antemortem 2-D echo LV mass determinations were compared with anatomic LV weight by postmortem chamber dissection. Major cardiac diagnoses included anatomic LV aneurysm in four, status post aneurysmectomy in one, transmural myocardial infarction in seven, congestive cardiomyopathy in five, rheumatic mitral disease in two, chronic severe mitral or aortic regurgitation in three, amyloid heart in two, and normal heart in three. Marked right-heart dilatation was present in 11 patients and LV thrombus in four. Regression equations derived in vitro for each 2-D echo instrument were used to correct LV mass estimates based on a short-axis, area-length method: uncorrected LV mass = 1.055 x k x 5/6 (AtLt - AcLc) + b, where At = total short-axis LV image area at the high papillary muscle level, Lc = endocardial LV length, k = an instrument-specific regression slope and b = an instrument-specific intercept. LV mass by 2-D echo correlated extremely well with actual LV weight (r = 0.93 slope = 0.85, SEE = 31 g, range 77-454 g). In contrast, M-mode echocardiographic LV mass estimates were less reliable (r = 0.86, SEE = 59 g) in these markedly distorted hearts. These 2-D echo LV mass results compare favorably with reported results from biplane angiography and M-mode echocardiography in more symmetric hearts. Thus, regression-corrected 2-D echo may be the method of choice for determining LV mass in man.

Echocardiography↗
PubMed1981

Replacement of ventricular myocardium with diaphragmatic skeletal muscle: short-term studies.

A pedicled diaphragmatic skeletal muscle graft was used to replace a portion of resected right ventricle in 35 dogs. The graft contracted when electrically stimulated directly or via the phrenic nerve before and after insertion. The electrical pacing threshold was lower for phrenic nerve stimulation (0.9 +/- 0.20 mamp) than for direct graft stimulation (2.3 +/- 1.19 mamp). The heart could be captured and paced by stimulating the muscle graft with higher current (16.2 +/- 4.49 mamp). The delay from pacing stimulus to muscle graft contraction when the graft was paced directly was 10 msec. The epicardial activation time delay when the heart was paced through the muscle graft was 27.0 +/- 9.08 msec. When the muscle graft pedicle was transected, the graft lost its ability to contract. The heart, however, could still be captured electrically through the graft for up to 4 hours. Strain gauge studies of the nonstimulated muscle graft showed tension development during pre-ejection ventricular contraction identical to that of the right ventricle. In the ejection phase, muscle graft tension slowly declined. The stimulated muscle graft developed active tension and echographically demonstrated muscle thickening during contraction. This study demonstrates that a vascularized, neurally innervated diaphragmatic muscle graft can be placed into the right ventricle. The graft retains its ability to contract in response to direct or phrenic nerve stimulation. It can be made to contract during any phase of the cardiac cycle. Thus diaphragmatic muscle grafts may provide a method to augment ventricular cavity size with synchronously contracting muscle.

Animals↗
PubMed1977

The mitral plication suture: a new technique of mitral valve repair.

During 1975, 67 patients underwent attempted repair of mixed mitral valve disease by use of the new mitral plication suture (MPS) technique. Ninety per cent had successful repair and 10 par cent required valve replacement. The MPS is a double, semicircular, buttressed annuloplasty suture that constricts the enlarged mitral annulus to correct mitral regurgitation (MR), supports mitral subunit repair procedures, and yet maintains the flexibility of the mitral annulus. The hospital mortality rate was 6 per cent. There were no late deaths during 10.4 months of follow-up. Six per cent of the patients who had valve repair required subsequent MVR. Their repair operations are considered late failures. Echocardiography, a useful technique for assessing the status of the patients postoperatively, demonstrated normal mitral valve and left ventricular function in the majority of patients; comparisons with replacement valves are documented. Death and morbidity was less frequent than in patients with MVR, both in the hospital and during follow-up. The aggressive policy of mitral valve repair has reduced the number of MVR's from 95 during 1974 to 52 in 1975. Although follow-up is short, we conclude that the new MPS is a valid surgical adjunct to the complete repair of the mitral valve.

Adolescent↗