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Biomedical subjects

R F Leighton

Publications and source records attributed to R F Leighton.

At least 37 records · Page 2Linked to original sources
PubMed1983

Regional sequential motion in the normal left ventricle: nonuniform apical motion.

Timing of the onset and sequence of systolic regional wall motion was examined in the digitized left ventricular cineangiograms of 13 patients with angiographically normal coronary arteries and left ventricular function. Distance--time curves for anterior and inferior wall segments, the aortic valve plane, and apex point were compared to the volume--time curve in each ventricle. No significant differences were found in the onset of motion for the wall segments or for descent of the aortic valve where the sequence of motion was generally uniform. At the apex point, however, the onset of motion was significantly delayed. In addition, reduced velocity of motion in the first half of systole was followed by high velocity motion in the latter half. This apparent nonuniform apical motion may be explained by a geometric relationship of normally contracting myocardial wall fibers adjacent to a thin apical point which has relatively little or no contractile motion of its own.

Cineangiography↗
PubMed1983

[Calculation of the peak systolic wall stress at the equator of the left ventricle by coupled M mode echo and pressure recordings].

The peak systolic wall stress at the equator of the left ventricle (sigma max) is the maximum load that the myocardial fibres bear during contraction. It is an index of the adaptation of the left ventricle to cardiac disease, and, when elevated, it indicates cardiac decompensation. sigma max was calculated by coupled M mode echo-LV pressure recordings in 51 cases: 11 patients without LV disease, 14 patients with aortic stenosis (AS), 14 patients with aortic incompetence (AI), 7 patients with severe mitral incompetence (MI) and 5 patients with cardiomyopathy with dilatation (CMP). sigma max was calculated from Mirsky's formula, the length of the long axis being deduced from the short axis and the diastolic:systolic ratio of these two axes from ventriculography. The normal value of sigma max by this method is 220 dynes 10(3)/cm2 +/- 30 with an upper limit of normal of 280 dynes 10(3)/cm2. sigma max was normal in patients with AS and AI, and increased in the cases of MI and CMP, in positive correlation with LV volume (r = 0,47) and the shape of the LV (long:short axis ratio). No correlations were found between sigma max and maximum LV pressure. The relatively low values of sigma max compared to the results obtained from coupled echo-angio recordings are partly due to the thick walled LV model and, to a large extent, to the lower values of short axis when measured by echo compared to angiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiography↗
PubMed1983

Scintigraphic detection of ventricular aneurysm with thallium-201.

We present two patients who exhibited striking abnormalities on stress thallium-201 scintigrams, suggesting ventricular aneurysm before documentation of this diagnosis by contrast ventriculography. The features of the scintigrams included: (a) a large perfusion defect overlying the cavity of the left ventricle, the defect extending to the periphery of the cardiac image and containing fewer counts than the lung background; (b) relatively increased lung background; (c) increased right-ventricular prominence; and (d) abnormal cardiac contour. Although large aneurysms of the left ventricle can usually be diagnosed from history and physical examination, occasionally they can be more subtle in their manifestations. Appearance of a myocardial perfusion image as described above should alert the physician to the possibility of this diagnosis.

Adult↗
PubMed1979

Quantification of myocardial ischemia and infarction with 201thallium scintigraphy.

A quantitative method for the analysis of 201thallium myocardial scintigrams, developed in an experimental infarcted dog heart model, has been compared with two nonquantitative methods for interpretation of stress myocardial scintigrams in two groups of patients studied with coronary angiography: 11 with normal coronary arteries and 14 with coronary artery disease. Three independent observers interpreted scintigrams which were 1) not computer processed; 2) corrected for background activity in lungs and chest wall; and 3) processed by a computer method which uses a uniform threshold of counts determined from the dog model to define perfusion defects. Interobserver variability as well as sensitivity and specificity of detecting coronary disease were examined. In patients with coronary artery disease interobserver variability was improved by using the computer technique: observers agreed as to the existence of a perfusion defect in 93% of the scintigrams as compared to 55% and 81% for the unprocessed and background-subtracted images respectively. No false positive indications of coronary disease were obtained by any of the three techniques. Use of the computer method did not improve the sensitivity of detecting coronary disease, however--71% compared to 64% for unprocessed images and 79% for background-substracted images. The advantages of this quantitative computer method are increased consistency of interpretation and lack of false positive diagnoses of coronary disease. An improved sensitivity of detection may be gained by varying thallium count thresholds according to anatomic location in the heart.

Animals↗
PubMed1979

Quantification of thallium-201 scintigrams in acute myocardial infarction.

A method has been developed for measurement of myocardial infarct size from thallium-201 scintigrams that depends on computer measurement of levels of radioactivity in the myocardium. In 16 dogs, thallium-201 scintigrams were obtained in the left lateral and left anterior oblique projections 48 hours after ligation of the left anterior descending coronary artery. Scintigraphic results were obtained by two independent observers and were compared with tissue measurements of infarct volume calculated from thallium autoradiograms and nitro-blue tetrazolium (NBT)-stained tissue slices. Infarct volumes derived from tissue measurements were used to develop criteria for the computer scintigraphic technique. There was no significant difference in the scintigraphic measurements made by the two observers. Scintigraphic infarct size in the left lateral and left anterior oblique projections correlated with tissue infarct size with r values of 0.88 and 0.75, respectively, for thallium autoradiography and 0.71 and 0.70, respectively, for NBT tissue staining. The range of infarct volume was 3.3 to 14.8 percent of the left ventricular mass. Results of this study suggest that scintigraphic quantitation of infarct size is feasible in this dog model.

Acute Disease↗
PubMed1978

Serum chromium and angiographically determined coronary artery disease.

Human aortas sampled from populations where there is little advanced atheromatous plaque formation contain higher concentrations of chromium than do aortas from populations in which atheromatosis is prevalent. In the present study serum cholesterol, triacylglycerols, and chromium (Cr3+) concentrations were measured in 32 subjects in whom coronary artery disease was assessed by cineangiography. The distribution of subjects with diseased and normal arteries overlapped below 5.50 microgram of chromium per liter. Only subjects free of coronary artery disease had chromium concentrations greater than or equal to 5.50 microgram/liter. The role of chromium was assessed in the context of the selected risk factors: cholesterol, triacylglycerols, and systolic and diastolic blood pressure. The group with coronary artery disease had significantly lower serum chromium concentrations than did the group with normally patent arteries.

Adult↗
PubMed1975

Percutaneous transfemoral coronary arteriography without systemic anticoagulation--a review of 648 consecutive procedures.

Experience with 648 consecutive percutaneous transfemoral coronary arteriograms and left ventriculograms performed in a teaching laboratory without the use of systemic anticoagulation during the procedure was reviewed. Only 1 death was felt to be related to a procedure, and this occurred 3 weeks after a myocardial infarction. There were 10 myocardial infarctions or emboli, 8 cerebral vascular accidents, and 7 femoral artery complications. Only 1 patient experienced a residual neurologic change following a procedure-related cerebral vascular accident, and this was a mild visual field defect. Clotting of the catheter without sequelae but necessitating procedural changes occurred in 10 instances. The transient nature of the neurologic deficits and the low mortality suggest that the emboli which occurred in these patients were small, possibly platelet-fibrin accumulations. It is postulated that with the use of careful technic larger emboli capable of producing myocardial infarction with shock or disabling cerebral vascular accidents can be prevented, even in a training situation. However, smaller embolic phenomena probably cannot be completely avoided by the use of careful technic, and it is for prevention of small emboli that systemic anticoagulation with heparin may be of value.

Angiocardiography↗
PubMed1975

Left ventricular pressure responses in post-angiographic angina.

Alterations in left ventricular end-diastolic pressure and in dp/dt observed in ten patients with coronary heart disease who developed angina pectoris following left ventricular cineangiography were compared with those of six other patients who developed angina spontaneously and with patients who underwent left ventricular cineangiography without experiencing angina. In the patients with post-angiographic angina there was a greater increase in end-diastolic pressure than that seen in the other patients, but there was no significant change in dp/dt. Changes in left ventricular pressure associated with post-angiographic angina would appear to reflect the combined effects of increased preload provided by the contrast material and of ventricular dysfunction including diminished compliance associated with angina. A rise in end-diastolic pressure greater than 20 mmHg following left ventricular cineangiography should alert the physician that the patient may be having myocardial ischemia.

Angina Pectoris↗
PubMed1975

Postural changes in left ventricular and mitral valvular dynamics in the systolic click - late systolic murmur syndrome.

Marked changes in the auscultatory pattern with posture have been noted in patients with mid-systolic clicks and/or late systolic murmurs (MSC-LSM). MSC tend to move earlier in systole and LSM become longer and often louder when patients assume upright posture. Systolic prolapse of the mitral leaflets with mild regurgitation account for MSC-LSM; earlier and greater prolapse with more and prolonged regurgitation associated with a reduced left ventricular volume (LVV) in the upright position would explain the auscultatory changes. Twenty-two patients with MSC-LSM were studied supine and at 45 degrees head-up tilt, recording intracardiac pressures, cardiac outputs, systolic time intervals, and performing LV cineangiography. Systolic prolapse of one or both mitral leaflets was demonstrated in all patients. Left ventricular end-diastolic and end-systolic volumes both decreased significantly at 45 degrees in all sixteen technically satisfactory studies. Greater mitral prolapse was noted upright in 12 of 14 studies with enough sinus beats to judge. The amount of mitral regurgitation was mild in all, and changes in amount from supine to upright posture could not be discerned angiographically. THE FINDINGS, SUGGEST THAT THE AUSCULTATORY CHANGES OCCURRING WITH UPRIGHT POSTURE IN PATIENTS WITH MSC-LSM are related to greater prolapse of the mitral leaflets which is associated with a small LVV in the upright position.

Angiocardiography↗
PubMed1975

Abnormal left ventricular wall motion at mid-ejection in patients with coronary heart disease.

The degree of inward motion at mid-ejection was examined for seven segments on the silhouettes of left ventriculograms taken in the 30 degrees RAO projection in patients with normal coronary arteries. The pattern of wall motion described in these patients was used to distinguish abnormalities in mid-systolic wall motion. One or more abnormally contracting segments were found at mid-ejection of 27 of 42 patients with obstructive coronary artery disease and normal end-systolic wall motion. Of the 57 segments found in these patients, 41 or 72% corresponded to sites of significant coronary artery obstruction. Seven patients had electrocardiographic evidence of prior infarction. Following coronary graft surgery in eight patients improved motion was found in association with graft patency in seven priviously delayed segments and two new areas of delayed wall motion associated with nonpatent grafts and electrocardiographic changes of infarction appeared. We postulate that some of the myocardial fibers in late contracting segments have been injured or infarcted and are able to contract effectively only during the latter half of ejection when ventricular wall tension is reduced.

Cineangiography↗