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Biomedical subjects

M M Ibrahim

Publications and source records attributed to M M Ibrahim.

At least 19 recordsLinked to original sources
PubMed1991

Effect of the degree of effort on exercise echocardiography for the detection of restenosis after coronary artery angioplasty.

To determine whether the accuracy of exercise echocardiography is affected by the degree of effort during exercise, we examined 101 patients who had 6 months earlier undergone successful coronary artery angioplasty, with resting and immediate postexercise echocardiography and same-day coronary angiography. A positive exercise echocardiographic response was defined as the development of a new or worsening wall motion abnormality postexercise, compared with resting wall motion. Significant coronary disease (greater than 50% diameter stenosis) was present in 48 patients, 38 of whom had single-vessel disease and 10 of whom had two-vessel disease. Exercise echocardiography correctly identified 32 patients with significant disease (sensitivity 67%) and 44 patients without significant disease (specificity 83%). The effect of the degree of exercise effort on the sensitivity and specificity of the test was evaluated by three criteria; (1) the percentage of maximum predicted heart rate (MHR), (2) the duration of exercise (DUR), and (3) the double product (DP). To determine the influence of the degree of effort upon sensitivity and specificity, the effort criteria were compared between patients with true positive (TP) tests to those with false negative tests (FN), and in patients with true negative (TN) tests compared with those with false positive (FP) tests. No significant differences were detected in MHR, DUR, or DP between TP versus FN patients or between TN versus FP patients. These results indicate that for symptom-limited exercise echocardiography in postangioplasty patients, neither sensitivity nor specificity is significantly affected by the degree of effort during exercise.

Angioplasty, Balloon, Coronary↗
PubMed1990

Effect of gonadal steroid hormones on the metabolic rate of the cold-acclimated gonadectomized male and female Chalcides ocellatus (Forskal).

Male and female Chalcides ocellatus were gonadectomized and cold acclimated at 15 degrees for 1 week. Lizards were injected with testosterone and estradiol, and their oxygen consumption was determined at 15 degrees. Testosterone and estradiol caused a significant increase in the whole body rate of oxygen consumption in male and female lizards, respectively.

Acclimatization↗
PubMed1987

Effect of regression of left ventricular hypertrophy following sotalol therapy on diastolic function in hypertensive patients.

The effects of changes in left ventricular mass following beta-adrenergic blockade therapy (sotalol) on left ventricular filling indices were examined in 16 patients with essential hypertension aged 46 +/- 8.3 years (mean +/- s.d.). The peak atrial to peak early diastolic velocity (A:E) ratio and the peak filling rate (PFR = peak early diastolic velocity X mitral annulus area) were measured by the use of pulsed Doppler left ventricular inflow time-velocity plots following placebo and after 8-12 weeks of sotalol monotherapy (160 mg/day). Compared with normal controls of similar age, our patients had a larger left ventricular mass and impaired left ventricular filling indices. Following sotalol, mean arterial pressure (MAP) decreased by 14%, the heart rate by 15% and left ventricular mass by 11%, while diastolic filling improved (A:E 17% and PFR 21%). Six patients had a decrease in left ventricular mass of greater than 15% (group A); other patients (group B) showed a smaller reduction. In spite of comparable changes in MAP and heart rate in groups A and B, the patients in group A showed a smaller degree of improvement in the A:E ratio. It is concluded that sotalol can induce regression of left ventricular hypertrophy and improve left ventricular filling in hypertensive patients, and it seems that improvement in diastolic filling is related to a reduction in afterload rather than to a decrease in left ventricular mass.

Adult↗
PubMed1985

Blood pressure responses to care procedures in ventilated preterm infants.

Responses of mean aortic blood pressure to sequences of routine care procedures in 22 ventilated, preterm infants were studied daily for the first 3 days of life. In the first 11 infants standard care procedures were used, whereas the next 11 infants were preoxygenated by a preceding 10% increase in inspired oxygen concentration; in these infants, chest physiotherapy was entirely omitted while the frequency of endotracheal suctioning was reduced. A total of 259 blood pressure responses were recorded. In general, responses were biphasic, consisting of an initial blood pressure drop followed by a greater blood pressure rise of longer duration. Baseline blood pressure, as well as the minimum and maximum blood pressure during the care procedures, increased with gestational age and with postnatal age. The blood pressure drop was most pronounced in the infants requiring the most intensive ventilatory support and was reduced by modifying the care procedures. The blood pressure rise was the least in the infants receiving pancuronium and phenobarbitone. Eight infants, 4 in each group, had intraventricular haemorrhage; in these infants, the care procedures induced more pronounced blood pressure drops in the first day of life when compared to the infants without haemorrhage.

Blood Pressure↗
PubMed1985

Contractile performance following regression of left ventricular hypertrophy in hypertensive patients.

The left ventricular end systolic stress-end systolic dimension (ESS-ESD) relation was used to assess the effect of regression in left ventricular hypertrophy on myocardial contractility in 14 hypertensive patients (mean age 47 years) treated with guanfacine (a sympatholytic central alpha-adrenergic agonist) for 10 weeks. Echocardiography (M-mode under two-dimensional guidance) was used to determine left ventricular dimensions, posterior wall thickness (PWT) and septal thickness (ST) before and during the last week of therapy. Left ventricular mass (LVM) expressed as cross-sectional area (CSA) and meridianal wall stress at end systole were derived. Echocardiography was carried out at rest and during i.v. infusion of sodium nitroprusside to alter left ventricular afterload. A minimum of four systolic arterial pressure-ESD points were available for analysis and the value for the slope ESS-ESD was calculated for each patient. Guanfacine produced a significant decrease (P < 0.005) in arterial pressure, wall thickness and CSA. The linear ESS-ESD slope was similar in patients with and without left ventricular hypertrophy and did not change in the whole group or in four patients who had a decrease in CSA of > 10%. It is concluded that guanfacine can induce regression of left ventricular hypertrophy in hypertensive patients and that a decrease in LVM does not influence the intrinsic contractile performance of the left ventricular.

Adult↗
PubMed1984

Maternal-fetal relationships in the parathyroidectomized rat. Intestinal calcium transport, serum calcium, immunoreactive parathyroid hormone and calcitonin.

We studied the role of the parathyroids in the adaptation of intestinal Ca transport that occurs during pregnancy, and whether maternal hypoparathyroidism causes fetal hyperparathyroidism. Serum Ca of pregnant parathyroidectomized (PTX) rats was significantly greater than nonpregnant, PTX animals. Intestinal active Ca transport was increased 2.1- and 2.2-fold by pregnancy in intact and PTX rats, respectively. Serum levels of immunoreactive parathyroid hormone (PTH) were nondetectable in PTX-pregnant rats. Fetuses from PTX rats appeared grossly normal. The serum PTH was not different in fetuses from PTX compared to fetuses from intact mothers and serum Ca, Mg, and P were normal. Thus, alleviation of maternal hypocalcemia during pregnancy in PTX rats may be due to an adaptive increase in intestinal Ca transport, which does not require the parathyroids. Fetuses from PTX mothers were euparathyroid and were protected from Ca deficiency during pregnancy.

Animals↗
PubMed1982

Maintenance of normocalcemia by continuous infusion of the synthetic bovine parathyroid hormone (1-34) in parathyroidectomized rats.

This work was conducted to estimate the replacement dose of the synthetic bovine parathyroid hormone [PTH(1-34)] that is required for maintenance of serum calcium (Ca) in parathyroidectomized (PTX) rats. Male rats were PTX and used in this study only if serum Ca was reduced to at least 7 mg/dl. We found that a solution of 2% cysteine, 150 mM NaCl, and 1 mM HCL was superior to 20 mM acetic acid for maintenance of biological activity of PTH (1-34) in situ during the period of hormone infusion studied. The PTH dose-calcemic response relationship was investigated using PTH in doses of 0.6, 1, and 3 U/h. The infusion of 1 U PTH per hour raised Ca to the normal level, whereas rats infused with 0.6 U/h were hypocalcemic and 3 U/h resulted in marked hypercalcemia. To extend this observation we carried out an infusion of 1 U PTH per hour for 14 days. We found that this infusion rate of bovine PTH (1-34) provided a relatively stable level of serum calcium with modest fluctuation from normocalcemic to somewhat hypercalcemic levels for the entire 14-day period of PTH infusion. Serum calcitonin was also elevated during the infusion period and then returned to the initial level when PTH treatment was stopped. After the minipumps containing PTH were removed, the serum Ca dropped rapidly to 5 mg/dl, which was significantly lower than the control (vehicle-infused) or initial values of serum Ca (7 mg/dl). Infusion of PTH at 3 U/h for 4 days did not produce this rebound hypocalcemia after the pumps were removed. Serum Ca in those experiments returned to the initial level after hormone treatment was discontinued.

Animals↗
PubMed1982

Some physiological changes during anesthesia for laparoscopy.

Twenty women studied for diagnostic or therapeutic laparoscopy with intraperitoneal insufflation of carbon dioxide. There were circulatory changes, dysrrhythmias, elevated central venous pressure and arterial blood pressure, hypercarbia, decrease in pH and increased peak air way pressure. With abdominal decompression all changes returned to within normal values.

Adult↗
PubMed1981

Factors influencing cardiac hypertrophy in hypertensive patients.

1. Seventeen male patients with essential hypertension were studied after 4 weeks of placebo and after 8 weeks of beta-adrenoceptor-blockade therapy with atenolol (100 mg/kg). 2. The influence of the following factors on left ventricular wall thickness and left ventricular mass index as determined by echocardiography was examined: patient's age, duration of hypertension, arterial pressure, blood pressure variability, supine heart rate, maximal exercise heart rate, left ventricular wall stress and 24 h urinary catecholamines. 3. Left ventricular mass index was related to systolic blood pressure (r = 0.54, P less than 0.05) and to extent of increase in heart rate with maximal exercise (r = 0.62, P less than 0.05). No significant correlation was present between mass index and other variables. 4. After atenolol therapy, left ventricular mass index decreased by 14 g/m2 (12%). Changes in mass were related to its initial value (r = 0.69, P less than 0.01) and to % change in wall stress (r = 0.64, P less than 0.05). Patients who had a decrease in mass index of 10% or greater had an initially lower diastolic pressure (P less than 0.001). Other factors did not appear to influence significantly the regression of hypertensive left ventricular hypertrophy.

Adult↗
PubMed1979

Left ventricular function in rheumatic mitral stenosis. Clinical echocardiographic study.

Echocardiography was used to examine the extent and significance of impairment in left ventricular function in 20 patients with rheumatic mitral stenosis. Indices of left ventricular performance--normalised mean rate of circumferential fibre shortening (Vcf), ejection fraction, normalised posterior wall velocity, and stroke volume were reduced. The impairment in left ventricular function was related to the degree of functional disability (NYHA), right ventricular dilatation, and left atrial enlargement. Vcf was inversely related to both the internal right ventricular diameter (r=-0.767, P less than 0.001) and the degree of left atrial enlargement (r=-0.554; P less than 0.05). The normalised velocity of the interventricular septum and the maximum systolic and diastolic endocardial velocities were also reduced. These results suggest that abnormalities in contractility of left ventricular myocardium are responsible for the impaired myocardial function in patients with mitral stenosis and that such impairment is clinically significant.

Echocardiography↗
PubMed1977

Electrocardiogram in evaluation of resistance to antihypertensive therapy.

The effect of blood pressure control on the evolution of electrocardiographic evidence of left ventricular hypertrophy was investigated 50 patients with hypertension who were followed up for an average period of nine years. Blood pressure response to treatment was determined both from casual office readings and from weekly averages of twice daily home readings. Changes in the ECG, judged from both alteration in QRS voltage and in ST-T segment, were related to the degree of arterial pressure control. Usually, both home and office arterial pressure responded similarly to antihypertensive therapy, but when there was a difference, electrocardiographic changes correlated best with home prssure averages. Reduction in maximum precordial QRS voltage (Sv1+Rv5-6) correlated best with changes in home systolic pressure (r = .460; P less than .001), but correlation with diastolic pressure variation either at home or in the office did not attain statistical significance (P greater than .10). The present data stress the importance of home pressure measurements in the management of some patients with hypertension and provide evidence that casual office readings may sometimes misjudge the effectiveness of antihypertensive therapy.

Adult↗
PubMed1976

Use of systolic time intervals in studying hypertension.

Systolic time intervals were measured in 54 hypertensive patients divided into three groups according to severity of hypertension, variability of blood pressure levels and presence or absence of a hyperkinetic heart. The three groups were: borderline hypertension (BLH), fixed essential hypertension (FEH) and hyperkinetic essential hypertension (HEH). Systolic time intervals (STI) provided information indicating an increased cardioadrenergic drive in BLH and HEH. This was supported by finding that propranolol abolished the increased contractility found at rest in BLH and HEH.

Adult↗