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Biomedical subjects

Y A Weiss

Publications and source records attributed to Y A Weiss.

At least 19 recordsLinked to original sources
PubMed1993

Ventricular arrhythmia in Duchenne muscular dystrophy: prevalence, significance and prognosis.

The prevalence and prognostic value of ventricular arrhythmias were examined in 45 Duchenne muscular dystrophy patients without congestive heart failure and followed up for 3 yr. Baseline evaluation included 24 h ECG monitoring, systolic time intervals measurement (preejection period/left ventricular ejection time PEP/LVET), echocardiogram and vital capacity tests. Fifteen patients (33%) had ventricular premature beats (VPB > or = 2 h-1). More complex ventricular ectopy (Lown grades 3, 4A, 4B) occurred in 12 patients (27%), who had abnormal ventricular contractility (PEP/LVET > 0.48) and an area of akinesia or dyskinesia. Complex VPB were present on presentation in only 3 of the 30 survivors (10%) but were detected in 6 of the 15 patients (40%) who died. Patients who died suddenly were more likely to have had documented complex ventricular arrhythmias (6 of 9; 66%). It is concluded that: (1) significant arrhythmias frequently coexist with asymptomatic left ventricular dysfunction and wall motion abnormalities; (2) complex VPB as well as left ventricular dysfunction and dilated cardiomyopathy are risk factors for sudden death.

Adolescent↗
PubMed1988

Systolic time intervals in Duchenne muscular dystrophy: evaluation of left ventricular performance.

The purpose of this study was to evaluate the prevalence of latent cardiac heart failure in Duchenne's muscular dystrophy (DMD). Systolic time intervals (STI) were measured in a cross-sectional study of a group of 177 patients 6-21 years old. Total electromechanical systole (QS2), left ventricular ejection time (LVET), and pre-ejection period (PEP), were corrected for heart rate by means of regression equations obtained from 33 normal subjects (QA2 I, LVET I, PEP I). Mean STI values were significantly different from those observed in an age-matched control group. PEP I was prolonged, LVET I was abbreviated, while QS2 I remained unaltered. STI varied significantly with age. Abnormal values were uncommon before age 10 years. The most critical period was 14-16 years, with an abrupt increase in prevalence from 35 to 72%. Such changes point to the practical use of the STI for clinical decision making especially for surgery.

Adolescent↗
PubMed1988

Difference in response of vascular resistance to orthostasis in patients with borderline and sustained essential hypertension.

Changes in hemodynamic parameters following 50-degree head up tilt were studied in a population of 78 males, including 30 patients with sustained essential hypertension, 30 patients with borderline hypertension, and 18 normotensive controls of the same age. The increase in vascular resistance following tilt was significantly higher in hypertensive subjects. In patients with sustained hypertension, baseline vascular resistance was significantly higher than in normotensive controls, and it was strongly correlated with its change following orthostasis. In patients with borderline hypertension, baseline vascular resistance was similar to that of normotensive controls and did not correlate with its change following orthostasis. The latter result suggests an abnormality in the autonomic nervous control in patients with borderline hypertension, possibly mediated by cardiopulmonary mechanoreceptors in the low pressure system.

Adult↗
PubMed1988

Renal and systemic hemodynamics in borderline hypertension.

Cardiac output (CO), renal blood flow (RBF), and glomerular filtration rate were measured in 29 young patients with borderline hypertension, in comparison with 26 normotensive controls of the same age and sex. In patients with borderline hypertension, both CO and RBF were significantly increased, whereas the RBF/CO ratio remained within the normal range. No significant changes in glomerular filtration rate and renal filtration fraction were observed. The study clearly demonstrated that renal ischemia was absent in young patients with borderline hypertension.

Adolescent↗
PubMed1987

Tilt test in essential hypertension. Differential responses in heart rate and vascular resistance.

Changes in hemodynamic parameters following 50-degree head-up tilt were studied in a population of 56 men, including 35 subjects with sustained essential hypertension and 21 age-matched normotensive controls. The increase in heart rate following tilt was similar in groups and exhibited the same reduction in response with age. The increase in vascular resistance following tilt was strongly and positively correlated with both age and baseline vascular resistance. The latter finding was observed mainly in hypertensive subjects. The study provided evidence that differentiated responses of heart rate and vascular resistance may be observed following orthostasis. In both normal and hypertensive subjects, the age dependence of heart rate response possibly reflected differences in baroreceptor reflex control of parasympathetic and sympathetic activity. In hypertensive subjects, the vascular response was amplified with age and baseline vascular resistance, suggesting a role for structural changes of the vessels in the increased vascular response.

Adult↗
PubMed1987

Hemodynamic effects of the anti-hypertensive agent ketanserin in hypertension in man.

The hemodynamic changes caused by ketanserin, an anti-hypertensive agent with S2-serotonergic receptor and alpha 1-adrenoceptor blocking properties, are reviewed in patients with essential hypertension. The hemodynamic profile associates a decrease in total peripheral resistance, an unchanged cardiac output, and a modest reflex cardiac stimulation. Whether the drug reverses the other hemodynamic abnormalities of essential hypertension, such as reduced arterial and venous compliances and increased cardiac mass, remains largely unknown. Evaluation of the changes in arterial and venous systems will be important in the view that the pharmacological profile of ketanserin could be involved in the modifications of the arterial wall observed in hypertension and atherosclerosis.

Blood Pressure↗
PubMed1982

Prospective study of predictive factors determining borderline hypertensive individuals who develop sustained hypertension: prognostic value of increased diastolic orthostatic blood pressure tilt-test response and subsequent weight gain.

Repeat hemodynamic determinations in supine and tilting positions were performed in 23 young men with borderline hypertension (HBP). The mean duration of follow-up was 48 months. During the study 11 patients had no change in hemodynamic parameters (group II), while 12 patients exhibited significant increase in systolic (p less than 0.001) and mean (p less than 0.01) arterial pressures (BP) and in body weight (p less than 0.05) (group I). In this latter group, the initial hemodynamic pattern included supine elevations in cardiac output (CO) and heart rate (HR) and significant increase in diastolic orthostatic BP. After follow-up, the group I primary supine increases in CO and HR were followed by secondary supine increases in total peripheral resistance (p less than 0.01) and systolic (p less than 0.001) and mean (p less than 0.01) BP with lower CO (p less than 0.05) and HR (p less than 0.001). In addition, it was shown during long-term follow-up in group I patients that : (1) the increase in systolic BP per unit age was negatively correlated with initial age (p less than 0.001), (2) the increase in BP was positively correlated with weight gain (p less than 0.05), and (3) the diastolic orthostatic hypertension disappeared. This study provides evidence that, in patients with borderline HBP having supine elevations of CO and HR, the subsequent development of sustained HBP can be expected, with follow-up observation of lower supine HR and disappearance of diastolic orthostatic hypertension accompanied by rapid weight gain.

Adult↗
PubMed1979

Guanfacine kinetics in patients with hypertension.

Guanfacine kinetics were studied in 19 patients with hypertension after single and repeated oral doses. The single-dose study was performed in two homogeneous groups who received 2 mg (n = 9) and 4 mg (n = 10). The plasma concentrations were fitted in a two-compartment open model with first-order absorption. After a lag time of 0.8 hr, the absorption occurred rapidly (t 1/2 congruent to 0.53 hr). The fast and slow elimination phases occurred with t 1/2s of 2 and 19 hr. At therapeutic levels the percent of drug in red blood cells (55%) was independent of total drug concentration. Peak plasma levels had small interindividual variations. Comparison of kinetic parameters and AUC at the two doses studied demonstrated that their bioavailability was equal and the kinetics were linear. In a multiple-dosing study, performed in the same subjects, the plasma levels at steady state were in good agreement with the predicted values (p less than 0.001) and proportional to daily dosage. A single method based on four blood samples collected after 24, 28, 32, and 36 hr allows a reasonable prediction of the effective steady-state plasma levels during chronic dosing with guanfacine.

Adult↗
PubMed1978

Total effective compliance of the vascular bed in essential hypertension.

Total effective vascular compliance, hemodynamic parameters, cardiopulmonary (CPBV) and total blood volumes (TBV) were determined in 31 men, including nine normotensive controls and 22 permanent essential hypertensive patients. The effective compliance was calculated from the changes in central venous pressure recorded simultaneously with the changes in blood volume obtained after a rapid dextran infusion. In hypertensives, compliance was significantly reduced (1.55 +/- 0.6 vs 2.25 +/- 0.11 ml./mm. Hg/Kg. in controls) (P less than 0.001) and negatively correlated with blood pressure (P less than 0.01), cardiac index (P less than 0.01), and the CPBV/TBV ratio (P less than 0.01). These results suggest that venous compliance contributes to the control of cardiac output in essential hypertension.

Adult↗
PubMed1978

Repeat hemodynamic determinations in borderline hypertension.

Repeat hemodynamic determinations were performed in 37 young men with borderline hypertension. The duration of the follow up study was 47 +/- three months. At each determination, those with borderline hypertension were compared to a group of matched normal subjects. Blood pressure increased from the first to the second determination, but the increase was significant only for systolic (P less than 0.001) and mean (P less than 0.01) arterial presssures. Cardiac index and heart rate, which were initially increased, decreased significantly (P less than 0.02; P less than 0.01, respectively) and decreased to normal values; total peripheral resistance increased (P less than 0.01); blood and plasma volumes decreased (P less than 0.01). At the first determination, the cardiac index-heart rate correlation was significant (P less than 0.01) and the cardiac index-blood volume correlation was not. At the second determination, on the contrary, the cardiac index-total blood volume correlation was significant (P less than 0.001) whereas the cardiac index-heart rate correlation was not. The study provides evidence that patients with borderline hypertension, over a short-term period, show (1) a greater increase in systolic than in diastolic pressure, (2) a return of cardiac output toward normal values through a decrease both in heart rate and blood volume, and (3) an increased importance of volume factors in the cardiac output control.

Adult↗
PubMed1978

Pharmacokinetics of intravenous and oral pindolol in hypertensive patients with chronic renal failure.

1. The pharmacokinetics of intravenous and oral pindolol were determined in 24 hypertensive patients with normal or impaired renal function. 2. In patients with normal renal function, the total clearance of the drug was the sum of both the renal and non-renal clearances in equal parts. The non-renal clearance was found to equal the hepatic clearance directly measured from the hepatic extraction ratio and hepatic blood flow. 3. Compared with patients with normal renal function, patients with chronic renal failure exhibited (i) unchanged transfer rate constants and distribution volumes, (ii) decreased total body clearance with decreased renal clearance and unchanged non-renal clearance. 4. Analysis of data obtained after oral administration of the drug by the Loo-Riegelman method showed that the pindolol absorption kinetic was non-linear. Compared with patients with normal renal function, patients with chronic renal failure exhibited (i) a significantly decreased fraction of dose effectively absorbed, (ii) an increased initial rate of absorption. The initial rate of absorption was inversely correlated with creatinine clearance. 5. The study provided evidence that in patients with renal insufficiency, (i) no increase in the metabolism of the drug accompanied the decrease in renal function, and (ii) decreased bio-availability was associated with a reduced fraction of the dose effectively absorbed and an increased rate of absorption.

Administration, Oral↗
PubMed1978

(+)-Propranolol clearance, an estimation of hepatic blood flow in man.

1 Hepatic blood flow was determined before and during (+)- and (+/-)-propranolol plasma concentration plateaus in 19 patients with suspected renal hypertension and normal liver function. 2 Hepatic blood flow significantly decreased (P less than 0.001) during (+/-)-propranolol administration and remained unchanged during (+)-propranolol administration. 3 Hepatic extraction ratio was 74 +/- 1% (+/-)-propranolol and 79 +/- 2% for (+)-propranolol. 4 Total propranolol clearances were determined during the steady-state achieved by a constant infusion. A highly significant positive relationship was observed (r = +0.86; P less than 0.01) between hepatic blood flow and (+)-propranolol clearance. The slope of the curve was 1.05 +/- 0.27. 5 The result implies that the total clearance of (+)-propranolol constitutes an accurate estimation of basal hepatic blood flow in subjects with normal liver function.

Adult↗
PubMed1978

Renovascular hypertension. Relationship between hepatic blood flow and plasma renin activity.

Hepatic blood flow and peripheral plasma renin activity were determined in 15 true renovascular hypertensive patients and in 13 patients with essential hypertension. In the renovascular hypertensives, plasma renin activity and hepatic blood flow were negatively correlated ( p less than 0.01). In contrast, no relationship was observed in the essential hypertensives. The study suggests that hyperactivity of the renin-angiotensin system could induce splanchnic arteriolar constriction in patients with renovascular hypertension.

Adult↗
PubMed1978

Total effective compliance, cardiac output and fluid volumes in essential hypertension.

Total effective compliance, hemodynamic parameters, extracellular fluid volume, cardiopulmonary (CPBV) and total blood (TBV) volumes were determined in 32 men, including 14 normotensive controls and 18 sustained essential hypertensive patients. The effective compliance was calculated from the changes in central venous pressure recorded simultaneously with the changes in blood volume obtained after a rapid Dextran infusion. In normotensive controls, compliance was 2.08 +/- 0.09 ml/mm Hg/kg and was positively correlated with plasma (r = 0.79) and extracellular fluid (r = 0.84) volumes. In hypertensives, compliance was significantly reduced (1.49 +/- 0.06 ml/mm Hg/kg; P is less than 0.001) and was correlated negatively with the CPBV/TBV ratio (r = -0.75) and positively with the plasma volume/interstitial fluid volume ratio (r = 0.84). These results suggest that in normotensives, there is a regulatory mechanism between volume and compliance and that this contributes to maintaining filling pressure and cardiac output within normal ranges. In hypertensives, the reduced compliance could participate in the maintenance of normal values of cardiac output and extracellular fluid volume by influencing the partition of intravascular and extracellular fluid volumes.

Cardiac Output↗
PubMed1978

Arterial compliance in permanent essential hypertension: preliminary report.

Systemic arterial compliance was measured in 22 patients with permanent essential hypertension and compared with 11 sex- and age-matched normal normal subjects. Determinations were made from analysis of the monoexponential blood pressure-time curve during diastole, according to a simple visco-elastic model. Arterial compliance was significantly decreased (P less than 0.001) in hypertensives. In the overall population, arterial compliance was negatively correlated to age (P less than 0.005) and blood pressure (P less than 0.001), suggesting that the changes in compliance could be attributable to the level of blood pressure per se and/or to the rigidity of the arterial wall. Administration of vasoactive substances (angiotensin and sodium nitroprusside) enabled a strong negative relationship (P less than 0.01) between arterial compliance and diastolic blood pressure to be demonstrated in each individual. The slope of the curve was not dependent on age and represented the ability to decrease compliance per unit rise in pressure. The slope was steeper in hypertensives, suggesting a change reactivity of the arterial wall in these patients.

Adult↗
PubMed1977

Effect of certain antiadrenergic agents on systolic time intervals in essential hypertension.

Systolic time intervals, including preejection period (PEP) and left ventricular ejection time (LVET), were studied in patients with permanent essential hypertension before and after intra-venous administration of propranolol 0.2 mg/kg (11 patients), clonidine 0.002 mg/kg (10 patients) and methyldopa 2 mg/kg (12 patients). With propranolol, diastolic blood pressure was unchanged and the heart rate decreased, whilst PEP and LVET were significantly prolonged (P less than 0.001). Clonidine caused a fall in blood pressure (P less than 0.001), heart rate was slightly reduced, PEP was prolonged (P less than 0.001) and there was a significant decrease in LVET at 5 min. With methyldopa, no significant effect was observed after intravenous injection, but 7 days oral administration produced the identical effect as clonidine. These observations suggest that certain antihypertensive drugs may impair left ventricular performance and depress myocardial contractility.

Adult↗
PubMed1977

[Problems in practical management of essential hypertension].

A study of 100 men with arterial hypertension showed that: 1) hypertension was predominantly moderate with 14% index of placebo reactivity; 2) only 3 patients had a surgically curable etiologic factor; 3) frequent associated findings were hereditary factors (60%), overweight and metabolic disorders (30 to 40%). Such results suggest that: a) hypertension could be treated, in the majority of patients, without preliminary etiologic investigations and, b) non invasive hemodynamics techniques are required to evaluate arterial and cardiac lesions which are the dominant factors in the prognosis.

Humans↗