Biomedical subjects

D A Halon

Publications and source records attributed to D A Halon.

8 recordsLinked to original sources

PubMed1992

Atrial natriuretic peptide in severe heart failure: response to controlled changes in atrial pressures during intravenous nitroglycerin therapy.

Atrial natriuretic peptide (ANP) levels were measured in 17 patients with severe congestive heart failure (New York Heart Association functional class IV), and the response of the peptide was studied during changes in cardiac filling pressures induced by a 24-hour infusion of nitroglycerin. In the control state plasma ANP levels (687 +/- 551 pg/ml) were 10-fold normal. During the administration of nitroglycerin, natriuretic peptide levels decreased (p less than 0.005) with changes matching very closely the decreases in pulmonary arterial wedge and right atrial pressures, a 1% mean decrease in the peptide level for every 1.5 to 2% mean change in atrial filling pressures. In patients with hemodynamic tolerance to constant-dose nitroglycerin infusion, the resulting increase in atrial pressures was accompanied by an appropriate secondary increase in the plasma ANP level. During the 24-hour study period there was a direct linear relationship between both wedge (r = 0.93, p = 0.007) and right atrial (r = 0.93, p = 0.008) pressures and the plasma ANP level, with a zero-pressure ANP intercept near normal (69 pg/ml for wedge, 174 pg/ml for right atrial pressure). The findings were no different in a subgroup of five patients receiving simultaneous treatment with captopril, except that plasma renin activity was higher and the aldosterone level lower than in the control group by a factor of approximately 2.5. The close relationship and tracking of atrial pressure and natriuretic peptide curves suggested that the sensitivity of the atrial stretch response to changes in atrial filling pressures was maintained in severe congestive heart failure.

Aged↗

PubMed1992

Usefulness of intracoronary isosorbide dinitrate in alleviating myocardial ischaemia during coronary balloon angioplasty.

The effect of intracoronary isosorbide dinitrate on provoked myocardial ischaemia during percutaneous transluminal coronary angioplasty (PTCA) was studied in 60 patients who had at least 1 mm electrocardiographic (ECG) ST segment deviation during a 70 s control balloon inflation period. Isosorbide dinitrate (dose 1 mg, 2 mg or 3 mg) or placebo (saline) was administered by slow intracoronary injection, and the ST segment changes recorded again during an identical dilatation period 2-4 min later. Following injection of isosorbide dinitrate, the severity of ST segment deviation decreased (1 mg -31 +/- 30%, P = 0.03; 2 mg -51 +/- 35%, P = 0.0001; 3 mg -36 +/- 32%, P = 0.002) during coronary balloon inflation, and the time until onset of 1 mm ST deviation was prolonged (1 mg +79 +/- 137%, P = 0.06; 2 mg +85 +/- 87%, P = 0.02; 3 mg +78 +/- 109%, P = 0.02). With the 3 mg dose, the time to maximum ECG change increased (+37 +/- 87%, P = 0.02). In the placebo group, there was a small decrease in the severity of ST segment deviation in patients receiving placebo (-23 +/- 32%, P = 0.03), but no change in the time to its onset or in the time to maximum ST deviation. Isosorbide dinitrate did not alter heart rate, systolic arterial pressure or the rate-pressure product at maximum ST segment change, implying that when isosorbide was administered by direct intracoronary injection, a direct cardiac effect was responsible for the major anti-ischaemic effect of the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗

PubMed1991

Effect of nisoldipine on exercise performance in heart failure following myocardial infarction.

The effects of the second generation calcium channel blocking drug nisoldipine on subjective and objective measurements of exercise performance were studied in 19 patients with moderate to severe heart failure (9 New York Heart Association functional class 2, 9 class 3 and 1 class 4) due to fixed ventricular dysfunction following myocardial infarction. Nisoldipine (10 mg 3 times daily) or placebo were administered for 8 weeks in a double-blind parallel study, assessing exercise performance by symptom-limited treadmill exercise testing using a modified Naughton protocol. Nisoldipine was well-tolerated and produced a small increase in peak estimated workload performed (6.2 +/- 2.9 to 8.2 +/- 3.0 METs, p = 0.06). The rate of perceived exertion (Borg scale) increased from 17.5 +/- 2.2 to 18.8 +/- 1.2 (p less than 0.02). The higher workload was performed at a lower peak systolic blood pressure (p = 0.03), higher peak heart rate (p = 0.06) and identical double product (NS). There was no change in resting and peak heart rate and blood pressure or in exercise performance in patients receiving placebo. Resting left ventricular ejection fraction, measured by radionuclide ventriculography, was unchanged after 8 weeks both in the placebo (21 +/- 9 to 20 +/- 9%) and nisoldipine (34 +/- 17 to 36 +/- 19%) groups.

Aged↗

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↗