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Biomedical subjects

D A Halon

Publications and source records attributed to D A Halon.

71 records · Page 4Linked to original sources
PubMed1983

The use of calcium with verapamil in the management of supraventricular tachyarrhythmias.

Verapamil, a calcium channel blocking drug, terminates supraventricular arrhythmias but may have a negative inotropic effect and produce peripheral vasodilatation and hypotension. We studied the efficacy of intravenous calcium gluconate in reversing or preventing the hypotensive effect of verapamil in 31 patients with atrial tachyarrhythmias. In 21 instances, verapamil was given first, and in 13 calcium was used as pretreatment before the administration of verapamil. Calcium gluconate, when given as pretreatment, prevented the fall in blood pressure induced by verapamil, and when given after verapamil restored blood pressure to control values. The administration of calcium did not alter the antiarrhythmic effect of verapamil.

Adult↗
PubMed1983

Frame by frame analysis of left ventricular function. Quantitative assessment of regional and temporal function.

We made a frame by frame analysis of the left ventricular cineangiogram to quantitate normal regional left ventricular function. Two different methods were used: contraction of the left ventricle towards a fixed point at the center of its long axis, and a pattern of contraction normal to the outline of the ventricle. Each method was used with and without correction for rotation and translational movement during systole. Left ventricular contraction and relaxation were represented graphically on a three-dimensional perspective plot and also using contour mapping techniques. The normal values and standard deviation were calculated for the extent, velocity and time course of ventricular contraction and relaxation in each region of the ventricle. The study provided a graphic visual display of the regional contractile pattern of the normal ventricle.

Adult↗
PubMed1983

Constrictive pericarditis following coronary-artery bypass grafting in a patient with chronic asymptomatic pericardial disease.

Constrictive pericarditis is a rare complication of open-heart surgery. We describe a patient who was found at the time of coronary artery bypass surgery to have asymptomatic pericardial thickening and subsequently developed rapidly progressive constrictive pericarditis. At operation for pericardiectomy, the bypass graft to the posterior descending coronary artery was found to be strangled by fibrous tissue while the remaining two bypass grafts were patent. Following pericardiectomy, the patient made a good recovery.

Chronic Disease↗
PubMed1983

Recurrent obstruction and thrombolysis of the right coronary artery.

A patient presented twice with the hyperacute phase of inferior wall myocardial infarction. Emergency coronary angiography was undertaken on each occasion and the occluded right coronary artery reopened by intracoronary thrombolysis using urokinase. The patient subsequently underwent successful percutaneous transluminal coronary angioplasty to dilate the underlying subtotal obstructive lesion in the proximal right coronary artery. The sequence of events in this patient demonstrates that (1) acute coronary thrombolysis can preserve ventricular myocardium, (2) recurrent thrombolysis can be performed successfully in the same artery in the same patient, and (3) coronary angioplasty may be an effective method of dilating the underlying coronary narrowing after coronary thrombolysis.

Adult↗
PubMed1983

Nonsurgical myocardial revascularization: initial experience with percutaneous transluminal coronary angioplasty.

Coronary artery atheromata obstruct coronary blood flow and produce myocardial ischemia. Percutaneous transluminal coronary angioplasty (PTCA) was performed to dilate narrowed coronary arteries on 16 occasions in 15 patients with severe proximal coronary artery narrowings and significant clinical angina pectoris. The lesions involved the left-anterior descending (LAD) coronary artery in nine patients (10 dilatation procedures), the right coronary artery (RCA) in five, and the circumflex coronary artery in one. Successful dilatation was achieved on nine occasions (56%): in 7 of the 10 LAD lesions (70%), in 2 of the 5 RCA lesions (40%), but not in the patient with circumflex disease. Successful dilatation was accompanied by a significant improvement in symptoms and in myocardial performance, as judged by atrial pacing MUGA (multigated) ventriculography. The ischemic response of the ventricle to stress the significantly reduced or abolished. PTCA is a useful, nonoperative method for dilating obstructed coronary arteries and for improving myocardial blood flow.

Adult↗
PubMed1982

Regional left ventricular ejection fraction from real-time two-dimensional echocardiography.

We studied regional left ventricular contraction patterns and ejection fraction from real-time two-dimensional echocardiograms in 8 normal subjects, 11 patients with coronary artery disease and 2 with congestive cardiomyopathy. The ventricle was divided into 12 regions and for each region, we calculated ejection fraction using a method which integrated the incremental volumes of a series of hemicylinders constructed within that region. The data obtained were displayed graphically to provide a detailed picture of regional ventricular function. Normal subjects had a uniform regional ventricular pattern (regional ejection fraction 54-74%). In patients with coronary disease, we found varying degrees of regional ventricular contraction abnormalities. In congestive cardiomyopathy global hypokinesis was present, and regional ejection fraction was reduced in all areas (11-39%). The study showed that two-dimensional echocardiography is a useful non-invasive bedside technique which may provide detailed quantitative information relating to regional left ventricular contraction abnormalities.

Adolescent↗
PubMed1981

The use of thallium 201 myocardial imaging to exclude myocardial infarction after dissection in congenital coarctation of the aorta.

The use of a mobile gamma camera with thallium 201 myocardial imaging is described to exclude myocardial infarction in a patient admitted to the coronary care unit in shock and with clinical, enzyme, and ECG changes consistent with infarction. The patient suffered from acute aortic dissection associated with congenital coarctation of the aorta. The myocardial scan excluded transmural myocardial injury.

Adult↗
PubMed1981

Regional ejection fraction of the normal left ventricle.

Regional ventricular function is important in assessing the functional significance of muscle fibrosis and ischemia in coronary artery disease. We have investigated three different methods of computerized quantification of the regional left ventricular function in 20 normal subjects. Method 1 divided the left ventricle into eight rectangular regions and corrected for rotatory and translational movement of the heart during systole. Method 2 was similar to Method 1, but corrected for shortening of the long axis of the left ventricle. Method 3 assumed radial inward contraction using a polar system of coordinates after correcting for rotatory and translational movement. The values obtained for the regional ejection fraction and regional volumes were calculated and compared for each region.

Cardiac Catheterization↗
PubMed1980

Hypertrophic nonobstructive cardiomyopathy as a cause of angina pectoris.

Four patients with severe classic angina pectoris and no evidence of myocardial infarction are described. All had ECG changes compatible with myocardial ischemia. Coronary arteriography showed normal coronary arteries (except for minor narrowing in one patient) and marked hypertrophy of the left ventricle without left ventricular outflow tract obstruction. The diagnosis of hypertrophic nonobstructive cardiomyopathy was confirmed by the presence of small left ventricular diastolic and systolic volumes with a supernormal ejection fraction indicative of a hypercontractile state of the left ventricle. Treatment with beta-blocking agents reduced myocardial work, improved diastolic compliance and decreased patients' anginal symptoms. Hypertrophic nonobstructive cardiomyopathy is an important cause of typical angina pectoris in patients who have normal coronary arteries on coronary angiography.

Adult↗
PubMed1980

Evaluation of myocardial perfusion by thallium-201 imaging at rest and during exercise. Comparison with ECG stress testing.

In order to assess the accuracy of thallium-201 cardiac imaging at rest or during exercise in detecting permanent or transient myocardial damage, we studied 49 patients with angiographically documented coronary disease (31 with previous myocardial infarction) and 29 patients with normal coronary arteries. The resting thallium scan was significantly more accurate in detecting previous myocardial infarction (31 patients) than the resting ECG (22 patients) (P < 0.01). The combination of thallium imaging and ECG stress testing revealed reversible myocardial ischemia in 41 of the 49 patients (84%), compared with 28 of 49 (57%) detected by ECG stress testing alone (P < 0.01). Thallium imaging was more accurate in ruling out coronary disease (26 of 29 patients, 90%) than ECG stress testing (19 of 29 patients, 65%) (P < 0.05). In patients with previous myocardial infarction, thallium imaging alone or in combination with ECG stress testing was not significantly more sensitive than ECG stress testing alone.

Coronary Circulation↗
PubMed1979

Serial echocardiography during the first 3 mth of life in normal neonates.

Echocardiography was performed in 13 normal neonates on the first day of life and repeated after 1 wk, 1 mth and 3 mth. Measurements were made of cardiac chamber size and wall thickness, mitral, tricuspid and pulmonary valve motion, right and left ventricular systolic time intervals, and of fractional left ventricular shortening (%deltaS) and mean velocity of circumferential fibre shortening (mean Vcf). During the study there was a relative decrease in right ventricular cavity size and wall thickness with an increase in the pulmonary valve EF slope, indicating a fall in pulmonary artery pressure with regression of the right ventricle. Left ventricular size and thickness increased while LVET became longer, possibly the consequence of an increasing left ventricular afterload. There was not a significant change in %deltaS and mean Vcf during the study period. The greatest change from right to left ventricular preponderance occurred between 1 wk and 1 mth of life and was accompanied by changes in the mean frontal QRS axis of the electrocardiogram. The study shows that significant changes occur in the echocardiogram during the first 3 mth of life; neonatal echocardiograms should be interpreted not only in relation to the baby's weight, but also to its age.

Atrial Function↗
PubMed1978

Left ventricular function in beta-thalassemia and the effect of multiple transfusions.

Left ventricular performance was studied in 23 young patients with severe chronic anemia due to beta-thalassemia major and intermedia. The patients were divided into three groups according to the number of blood transfusions they had received. The left ventricle (LV) was enlarged in patients who had not received blood and larger still in patients who had received multiple transfusions. Echocardiography and systolic time interval measurements showed that systolic function of the LV was good in all the patients and that there was no statistical difference in systolic function in patients who had and those who had not received multiple transfusions. Heart rate was increased in the latter group. Stroke index and cardiac index were high, especially in patients in Group 3. The diastolic closure rate (EF slope) of the anterior mitral leaflet and its amplitude of movement were increased, but less so in Group 3; this may reflect an alteration in diastolic LV distensibility. The results indicate that despite the presence of cardiomegaly and severe clinical congestive heart failure, LV performance is well preserved in patients with beta-thalassemia, even in those who have received repeated blood transfusions. Clinical cardiac failure is the consequence of volume overload and abnormal chamber compliance. There was no evidence in this of a congestive cardiomyopathy.

Adolescent↗
PubMed1978

Computer prediction of left ventricular complicance throughout diastole in normal patients.

This study deals with the development of a computer program to predict instantaneous left ventricular complicance, as defined by the tangent modulus E, throughout diastole. Diastole is divided into discrete time intervals according to the major events which occur: the start of isovolumic relaxation (aortic valve closure), mitral valve opening, the point of minimum left ventricular pressure, the junction of the rapid and slow filling phases, the start of atrial systole, and the peak of the 'a' wave. Each interval is separated into subintervals. Over each subinterval two mechanisms are assumed to operate: myocardial relaxation or contraction producing a pressure change without an accompanying volume change, followed by explansion of the left ventricle at constant pressure. Although these mechanisms occur simultaneously in the intact heart, they are treated sequentially in a multistage computer program that employs the finite element technique to determine the displacements within a thick-walled ellipsoidal shell. The smaller the time interval between successive stages, the closer is the approximation to the actual continous process of myocardial relaxation, contraction, and distension. Diastolic determinants revealed in this investigation are the mechanical properties of the myocardium, the state variables of pressure and volume, and the control variables of wall thickness and cavity size. In isovolumic relaxation, the myocardium relaxes and the ventricular wall thickens to reduce intracavitary pressure. The relaxation process continues and intraventricular pressure falls to a minimum (0-point) while ventricular volume increases after mitral valve opening. In the succeeding phases, excluding atrial systole, ventricular filling pursues, the properties of the myocardium change, there is an increase in tone (possibly due to myocardial contraction), the wall thins and intraventricular pressure rises. Computer prediction shows that at the start of diastole the tangent modulus is approximately 6 times the enddiastolic value, and is nearly 0 at the onset of the slow filling phase. Tangant modulus is a useful index by which to distinguish normal from abnormal patients provided the characteristics of E as a function of time are recognized and compared throughout diastole.

Compliance↗
PubMed1977

Thrombosis on Björk-Shiley aortic valve prosthesis. A case report and review of the literature.

A patient who developed thrombosis on a Björk-Shiley aortic valve prosthesis is reported. The patient presented with severe angina pectoris and the main physical findings were absence of the closing click of the prosthetic valve and the presence of systolic and diastolic aortic murmurs. Echocardiography showed early closure of the mitral valve and depressed left ventricular function. An emergency operation was performed and the clot was removed. The patient's recovery was uneventful and he is well one year after surgery. Awareness of the possibility of valve thrombosis is necessary in view of the need for emergency surgical treatment. The literature on the subject is reviewed.

Adult↗
PubMed1976

Regional ventricular dysfunction in coronary artery disease.

Percentage asynergy, ejection fraction (EF), left ventricular end diastolic pressure (LVEDP) and the site of coronary artery narrowing or obstruction were measured in 69 patients with significant coronary artery disease. Complete obstruction in the first third of the left anterior descending artery (LAD) produced a mean asynergy of 49% associated with an ejection fraction of 40% and a LVEDP of 19mm Hg. The extent of asynergy was modified by the nature of the underlying coronary artery anatomy and the protective circulation. Complete obstruction in the main right coronary artery produced a mean asynergy of 20% associated with an EF of 67% and LVEDP of 6 mm Hg. Complete obstruction in the first third of the circumflex artery produced a mean asynergy of 15% associated with an EF or 74% and LVEDP of 14mm Hg. Subtotal obstruction in the first third of the LAD produced a mean asynergy of 25% associated with an EF of 62% and LVEDP of 7mm Hg. The damage produced by a LAD obstruction was extensive while that of a right or circumflex obstruction was mild. Patients always had a high percentage asynergy after two episodes of myocardial infarction. A negative linear relationship was found between percentage asynergy and EF. There was a rough positive linear relationship between LVEDP and percentage asynergy.

Blood Pressure↗
PubMedDate not supplied

Exercise testing in patients with chest pain and normal coronary arteries: improving test specificity by use of a simple logistic model.

Despite an exercise electrocardiogram (ECG) positive for ischemia by established criteria, many patients referred for coronary angiography to evaluate chest pain are found to have angiographically normal coronary arteries (NCA). Exercise ECG were analyzed from 27 patients with chest pain and angiographically NCA and 28 patients with chest pain and coronary artery disease (CAD) using univariate and multivariate logistic regression analysis. We derived the following logistic model for the logit probability of CAD: 3 + SEX x 4 - METs x 0.7 + STDV5 x 0.8, where SEX = 0 for female and SEX = 1 for male, METs = maximal estimated work load (metabolic equivalents) and STDV5 = horizontal or downsloping ST depression (mm) in V5. A logit probability > or = 0 identified CAD with a sensitivity of 79% and a specificity of 89%. The model correctly identified 28/36 (78%) patients with CAD, and 7/10 (70%) patients with NCA (correct diagnosis 76%; p < 0.02) in a separate random group of 46 unselected patients with positive exercise tests undergoing diagnostic coronary angiography.

Adult↗