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H Haddad

Publications and source records attributed to H Haddad.

At least 19 recordsLinked to original sources
PubMed2003

The modulation of simple reaction time by the spatial probability of a visual stimulus.

Simple reaction time (SRT) in response to visual stimuli can be influenced by many stimulus features. The speed and accuracy with which observers respond to a visual stimulus may be improved by prior knowledge about the stimulus location, which can be obtained by manipulating the spatial probability of the stimulus. However, when higher spatial probability is achieved by holding constant the stimulus location throughout successive trials, the resulting improvement in performance can also be due to local sensory facilitation caused by the recurrent spatial location of a visual target (position priming). The main objective of the present investigation was to quantitatively evaluate the modulation of SRT by the spatial probability structure of a visual stimulus. In two experiments the volunteers had to respond as quickly as possible to the visual target presented on a computer screen by pressing an optic key with the index finger of the dominant hand. Experiment 1 (N = 14) investigated how SRT changed as a function of both the different levels of spatial probability and the subject's explicit knowledge about the precise probability structure of visual stimulation. We found a gradual decrease in SRT with increasing spatial probability of a visual target regardless of the observer's previous knowledge concerning the spatial probability of the stimulus. Error rates, below 2%, were independent of the spatial probability structure of the visual stimulus, suggesting the absence of a speed-accuracy trade-off. Experiment 2 (N = 12) examined whether changes in SRT in response to a spatially recurrent visual target might be accounted for simply by sensory and temporally local facilitation. The findings indicated that the decrease in SRT brought about by a spatially recurrent target was associated with its spatial predictability, and could not be accounted for solely in terms of sensory priming.

Analysis of Variance↗
PubMed2002

Modulation of the perception of temporal order by attentional and pre-attentional factors.

When two stimuli are presented simultaneously to an observer, the perceived temporal order does not always correspond to the actual one. In three experiments we examined how the location and spatial predictability of visual stimuli modulate the perception of temporal order. Thirty-two participants had to report the temporal order of appearance of two visual stimuli. In Experiment 1, both stimuli were presented at the same eccentricity and no perceptual asynchrony between them was found. In Experiment 2, one stimulus was presented close to the fixation point and the other, peripheral, stimulus was presented in separate blocks in two eccentricities (4.8 degrees and 9.6 degrees ). We found that the peripheral stimulus was perceived to be delayed in relation to the central one, with no significant difference between the delays obtained in the two eccentricities. In Experiment 3, using three eccentricities (2.5 degrees, 7.3 degrees and 12.1 degrees ) for the presentation of the peripheral stimulus, we compared a condition in which its location was highly predictable with two other conditions in which its location was progressively less predictable. Here, the perception of the peripheral stimulus was also delayed in relation to the central one, with this delay depending on both the eccentricity and predictability of the stimulus. We argue that attentional deployment, manipulated by the spatial predictability of the stimulus, seems to play an important role in the temporal order perception of visual stimuli. Yet, under whichever condition of spatial predictability, basic sensory and attentional processes are unavoidably entangled and both factors must concur to the perception of temporal order.

Analysis of Variance↗
PubMed2001

Low oxygen tension and autologous plasma enhance T-cell proliferation and CD49d expression density in serum-free media.

BACKGROUND: As cellular immunotherapy with ex vivo expanded cells becomes more widely used to treat a variety of illnesses, optimization of culture parameters, to maximize cell production and function, is essential for continued success. The effects of reduced oxygen tension and autologous plasma on T-cell expansion, receptor expression, apoptosis, and cytolytic activity in serum-free media were investigated. METHODS: PBMCs derived from whole blood samples were activated with anti-CD3 and anti-CD28 MAb in serum-free (AIM V) medium containing IL-2, and maintained at 5% and 20% oxygen tension. In some cases cultures were supplemented with 2% autologous plasma. RESULTS: Low oxygen enhanced T-cell expansion 13- and 4.8-fold in serum-free and plasma-supplemented media, respectively. Autologous plasma also had a beneficial effect on T-cell cultures. Plasma-supplemented cultures expanded 74-fold more than serum-free cultures at low oxygen tension, and 43-fold more at high oxygen tension. Several samples expanded very poorly under serum-free conditions, and reasonable cell numbers were obtained only from plasma-supplemented cultures. CD49d expression density increased 3-fold to 4-fold in cultures supplemented with plasma. In contrast to our previous findings in serum-containing media, IL-2 receptor expression kinetics were unaffected by oxygen tension. No effects caused by oxygen tension or autologous plasma on expression of other surface antigens (CD4, CD8, CD44, CD95) were observed. DISCUSSION: Low oxygen tension and autologous plasma greatly increase expansion of T cells, thereby decreasing the time needed for production of cells for prophylaxis. Increased CD49d expression density may translate into improved migration and cytotoxicity.

Antigens, CD↗
PubMed2001

The management of patients who have suffered an acute myocardial infarction in a tertiary care centre.

BACKGROUND: The standard of management after acute myocardial infarction (MI) includes beta-blockers and acetylsalicylic acid (ASA). Angiotensin-converting enzyme (ACE) inhibitors and lipid-lowering agents are indicated for some patients, and calcium channel blockers should generally be avoided. It is suspected that many patients with MI are not discharged from hospital with optimal medical management. OBJECTIVES: To determine what proportion of patients in a tertiary care hospital with acute MI are discharged on optimal medical therapy, and to identify what barriers exist to obtaining optimal treatment for as many patients as possible. PATIENTS AND METHODS: Charts were retrospectively reviewed for 717 patients with acute MI admitted to the Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia from January 1, 1997 to April 30, 1999. Charts were reviewed for demographics, comorbidities, investigations performed, and medications on admission and discharge. When discharge medications did not match the optimal medical management, the chart was reviewed for the reasoning behind the decisions. RESULTS: In-hospital mortality was 9.6%. Among 648 patients who survived to discharge, 577 (89.0%) were discharged on a beta-blocker, 261 (40.3%) on an ACE inhibitor, 105 (16.2%) on a calcium channel blocker and 578 (89.2%) on ASA. Patients 65 years of age or older were less likely than their younger counterparts to be discharged on a beta-blocker (272 of 315 [86.3%] versus 305 of 333 [91.6%], P<0.04) and more likely to be discharged on a calcium channel blocker (70 of 315 [22.2%] versus 35 of 333 [10.5%], P<0.0001). No significant difference in the use of beta-blockers or calcium channel blockers was found between men and women (beta-blockers: 385 of 432 [89.1%] men versus 192 of 216 [89.9%] women, P<0.92); calcium channel blockers (67 of 432 men [15.5%] versus 38 of 216 women [17.6%], P<0.50). Among patients with low density lipoprotein greater than 3.5 mmol/L, 158 of 200 (79.0%) were discharged on a lipid-lowering agent. Among patients with documented ejection fraction less than 40%, 94 of 103 (91.3%) were discharged on an ACE inhibitor. Most patients had acceptable contraindications to the medications that they did not receive. CONCLUSIONS: The study centre showed much better use of appropriate medications than has been previously described, showing that optimal medical therapy can be achieved for the vast majority of patients with acute MI.

Adrenergic beta-Antagonists↗
PubMed2001

Myocardial scintigraphy correlates poorly with coronary angiography in the screening of transplant arteriosclerosis.

BACKGROUND: Coronary angiography remains an important screening tool for transplant coronary arteriosclerosis (TxCAD) after heart transplantation despite criticism that it underestimates the incidence of TxCAD. In an effort to improve TxCAD incidence estimation, several methods of screening have been proposed. In the present study, the incidence of TxCAD assessed by both yearly coronary angiography and stress myocardial scintigraphy imaging was reviewed. PATIENTS AND METHODS: Ninety-nine consecutive primary heart transplantations were performed from 1988 to 1999. The standard immunosuppression protocol consisted of the introduction of antilymphocyte globulin and steroids, while maintenance therapy was with cyclosporine, imuran and steroids. Coronary angiography and a stress 2-methoxyisobutyl-isonitrile perfusion scan were performed yearly. TxCAD was defined by angiographic evidence of luminal abnormality by catheterization, or a perfusion abnormality at rest or after stress on myocardial scintigraphy. RESULTS: The mean recipient age was 49+/-12 years and the mean donor age was 33+/-13 years. The etiology of heart failure was ischemic cardiomyopathy (50%), dilated cardiomyopathy (41%) and congenital heart disease (9%). The freedom from angiographic TxCAD was 92% at one year, 64% at five years and 35% at eight years. The freedom from nuclear imaging TxCAD was 92% at one year, 69% at five years and 44% at eight years. However, a diagnosis of TxCAD by angiography only correlated with a diagnosis of TxCAD by nuclear imaging 52.8% of the time in the same patient, with a median time between studies of one month. CONCLUSION: The overall incidence of TxCAD diagnosed by angiography and nuclear imaging appears similar but correlates poorly in patients, casting doubt on the routine use of myocardial scintigraphy for screening TxCAD.

Adolescent↗
PubMed2000

Sirolimus, a new potent immunosuppressant agent for refractory cardiac transplantation rejection: two case reports.

Rejection remains a major cause of both early and late morbidity and mortality following heart transplantation despite major advances in immunosuppressive therapy. A major hurdle in the successful management of patients who have undergone heart transplantation is preventing and treating graft rejection. Cyclosporine, mycophenolate mofetil, azathioprine, tacrolimus (FK506) and OKT3 are well documented, effective immunosuppressive medications that prevent and treat acute or chronic rejection following heart transplantation. One of the macrolide antibiotics, sirolimus, is known to have immunosuppressant activity. In two patients with chronic rejection of cardiac grafts refractory to usual antirejection medications, sirolimus was successfully used to suppress graft rejection. Both patients continued to be rejection free after 10 months of sirolimus treatment despite significant decreases in doses of other immunosuppressants.

Administration, Oral↗
PubMed1999

Progressive scoliosis in early, non-progressive CNS injuries: role of axial muscles.

Forty-three patients with progressive neurological deficits involving axial musculature, starting 3-6 years after non-progressive brain injuries insults are described. Losses of function followed period of several years of stable motor deficits. Subsequent losses were stereotypic, with loss of ambulation and scoliosis, followed by loss of word articulation, malalignment of the mandible and ultimately neurogenic impairment of swallowing. Physical therapy, serial castings and spinal instrumentation palliated specific musculoskeletal problems but did not alter the relentless loss of various functions. The balanced action of paired axial muscles (i.e. spine, proximal muscle groups of the lower extremities, oropharynx, mastication) is regulated by the brainstem with modulation by the cerebral hemispheres. The clinical evolution in these patients suggest that, in the absence of normal input from the cerebral hemispheres, some patients have a progressive loss of these brainstem mechanisms. The most resistant functions (last ones to be lost), seem to be the ones phylogenetically most relevant for survival, such as suction and swallowing.

Adult↗
PubMed1999

Ten-year heart transplantation experience at the MARITIME HEART CENTER: does volume affect results?

OBJECTIVE: To evaluate the experience of a small volume Canadian heart transplantation centre. DESIGN: Ninety-four consecutive primary heart transplants were performed from 1988 to 1998 at the Maritime Heart Center, Halifax, Nova Scotia, with 100% follow-up. Kaplan-Meier survival analysis was used. RESULTS: The mean recipient age was 48.5+/-12.3 years and donor age 33+/-13.2 years. Eighty per cent of recipients were men. The prevalence of elevated pulmonary vascular resistance (4 or more Wood units) was 20.2%. Etiology of heart failure was ischemic cardiomyopathy (50%), dilated cardiomyopathy (40.9%) and congenital heart disease (9.1%). Survival was 85.9% at one year (n=71), 75.3% at five years (n=33) and 60.5% at eight years (n=8). There was a trend toward survival benefit with human leukocyte antigen (HLA) -DR matching, body mass index ratio of donor to recipient greater than 0.8, ischemic time less than 90 mins and male donors. There was no effect on survival with donor or recipient age, recipient sex, diabetes, hypertension, hypercholesterolemia, elevated pulmonary vascular resistance and HLA-A/B mismatch. CONCLUSIONS: Excellent survival at one and five years following heart transplantation is reported that compares favourably with results published by the International Society for Heart and Lung Transplantation.

Adolescent↗
PubMed1998

Surgical correction of scoliosis in patients with generalized seizures. Risk of vertebral body fracture.

STUDY DESIGN: A retrospective evaluation of the outcome of surgical management of progressive scoliosis in institutionalized patients with frequent, uncontrolled, generalized tonic clonic seizures. OBJECTIVES: To determine the safety and stability of internal fixation devices in patients with progressive scoliosis and intractable seizures. SUMMARY OF BACKGROUND DATA: Progressive scoliosis is a common problem in severely disabled patients. It has been the belief among some spine physicians that the coexistence of intractable seizures with progressive scoliosis is a contraindication for surgery, because most of the thoracic and lumbar spine is fixed and "unyielding" after internal fixations, increasing the risk of vertebral fractures. There have been reports of fracture of fixation devices, particularly Harrington rods, under conditions of massive trauma or mechanical stress, such as seizures. METHODS: The authors reviewed the outcome of six profoundly retarded institutionalized patients with a history of intractable seizures who underwent internal fixation of the spine between 1984 and 1987 because of progressive scoliosis. Seizure types and frequency of convulsion were obtained from the institutional charts. Follow-up radiographs of the spine obtained at 1, 3, and 6 months after the surgery and once a year thereafter were reviewed by the radiologist and orthopedic surgeon with special attention paid to fractures, stability of the fusion, and integrity of the instrumentation. RESULTS: Six patients underwent spinal fusion with internal spinal fixation, four patients with Harrington rods and two with Luque rods. All patients had refractory tonic clonic seizures ranging from 11 to 80 generalized tonic clonic convulsions per year for the 10-year follow-up period after surgery. There were no fractures, subluxation, or pseudoarthrosis of the fused vertebrae or the vertebral bodies adjacent to the fusion. There were no fractures of the instrumentation. CONCLUSIONS: The authors' findings suggest that when appropriate fusion is attained, the use of internal fixation devices is not contraindicated in the management of progressive scoliosis in patients with intractable seizures.

Adolescent↗
PubMed1997

Status epilepticus associated with the combination of valproic acid and clomipramine.

An epileptic patient well controlled on valproic acid (VPA) developed a prolonged episode of status epilepticus 12 days after initiation of 75 mg of clomipramine (CMI) to treat depression. Serum level of VPA in the emergency room was unchanged from her previous levels; serum level of CMI was very elevated despite the relatively small dose of CMI. A pharmacokinetic interaction between VPA, an enzyme inhibitor, and CMI has not been described but seemed to have occurred in this patient. Decreased metabolism of CMI and its metabolites, increased free CMI fraction, and precipitation of a nonlinear saturation kinetic state has been described when CMI was used concomitantly with other highly protein-bound, enzyme-inhibiting compounds. This case provides reasonable evidence that the combination of VPA and CMI may result in elevation of levels of CMI and possibly of its metabolites and may precipitate seizures in patients with an underlying predisposition. The elevated serum level of CMI at the time of the seizures, despite the relatively small oral dose of the drug, suggests that VPA may have inhibited its metabolism and/or elimination.

Adult↗
PubMed1996

Kinking and coiling of internal carotid artery with and without associated stenosis. Surgical considerations and long-term follow-up.

Although incidence of coiling and kinking of internal carotid artery has been estimated to be from 10% to 16% in general population, respective clinical significance still remains the ground of controversy. Cerebrovascular hemodynamic changes mainly from kinking and in a lesser degree from coiling, have been documented with oculoplethysmographic and angiographic differences, accompanying positional changes of the head. The opposite view however, that similar variations represent a benign and incidental finding, has been also expressed. In a 24-year period ending March 1994 and with case material of carotid artery surgery totalling 1123 operations, 59 patients with different type of kinking and coiling underwent surgical reconstruction. There were 31 patients with kinking, 14 with coiling and 14 (22%) with associated occlusive process at the origin of the internal carotid artery. In the later, three cases with abdominal aneurysm are also included. Apart from angiographic evidence, particular value was ascribed to symptomatology and ophthalmodynamographic changes, produced in different head positions. Operative indications with the exception of four cases, were determined on the basis of symptoms compatible with brain ischemia. In all instances of isolated kinking and coiling, straightening was obtained by segmental resection of the common carotid artery and end to end anastomosis. In cases with associated occlusion, transection of internal carotid artery at its origin and re-implantation in the lateral aspect of the common carotid, was the remedy of choice.

Adult↗
PubMed1994

Swallowing difficulties and early CNS injuries: correlation with the presence of axial skeletal deformities.

We reviewed the neurological findings in 36 adults with history of perinatal brain injury that required gastrostomy due to progressive swallowing difficulties in a population of 624 institutionalized patients. A stereotypic pattern of progression of deficits was observed. Risk factors that correlated with increased risk of swallowing disorders included: presence of multiple handicaps; progressive deformities of the spine and extremities; decreased range of motion of mandible, laterognathism and other mandibular asymmetries. These findings suggest that spinal deformities and swallowing difficulties are part of a spectrum of impaired function of paired axial muscles in this population. The identification of these risk factors may help in the long-term care plan of severely impaired patients whose survival is extended by the use of feeding tubes.

Adolescent↗
PubMed1994

Carotid artery surgery and the principle of prophylaxis: recurrence in operated and nonoperated patients.

A total of 700 carotid endarterectomies have been performed over a 24-year period at the authors' institute; of these patients 632 (90.3%) had unilateral and 68 (9.7%) had bilateral disease. Some 71 patients who declined operation were followed-up to obtain the natural history of carotid disease. The operative results were compared against this untreated group of patients. Surgical endarterectomy was recommended for a recovered stroke in 190 patients (27.1%), progressive ischaemia in 20 (2.9%) and transient ischaemic attacks in 410 (58.6%). A group of 100 patients with non-specific symptomatology, who were considered 'symptom-free', were also operated on; none of these died or developed permanent postoperative neurological defects. The mean age of patients was 56 (range 28-86) years. The overall operative mortality rate was 0.8%. Perioperative neurological deficits occurred in 0.5% and temporary cranial nerve injury in 1.8%. The follow-up covered a period of 10 years, but was in several instances extended to 14 years. The incidence of late neurological events in the patients having an endarterectomy was 3%. In the non-operated group, 12% of normotensive and 18% of hypertensive patients developed symptoms. The 10-year postoperative survival rate was 80% in the symptom-free group of patients, 70% in those with transient ischaemic attacks and 60% in those who had a previous stroke.

Adult↗
PubMed1994

Abdominal aneurysmectomy and determinants of improved results and late survival. Surgical considerations in 672 operations and 1-15 year follow-up.

The present communication is concerned with 672 abdominal aneurysmectomies performed over a period of 24 years. All aneurysms with diameter 4 cm and above, were considered for surgery. Emphasis is given on factors determining post operative results and late survival. There was an age ranging from 38 to 92 years (mean 68.3). Elective surgery was performed in 434 cases with mortality 2.8%. In 100 symptomatic patients mortality was 4%. In 115 cases emergency undertaking was necessary. From this particular group, 80 cases represent formal rupture with mortality 41%. In the remaining 35 patients with symptomatology compatible with "impending rupture" mortality was 6%. There were 5 cases with inflammatory aneurysm with no incidence of death and 18 with simultaneous renal reconstruction. Mortality in the latter group was 11%. Risk factors including heart disease, hypertension and other associated pathology, were responsible for the majority of early deaths within the period of 30 post operative days and late mortality. Concerning late deaths, cardiac cases were predominant (24%), followed by cerebrovascular insufficiency (8%), cancer (5%) and chronic pulmonary disease (6%). In the overall follow-up, parameters such as hypertension with and/or without associated heart disease, symptomatology due to aneurysm and other associated pathology, were comparatively used in selective group of patients. Late mortality was investigated among three groups of patients and classified according to the 60, 70 and 80 decade of life. An entry form listing pertinent data was constructed and completed on the base of direct information from 489 (72.7%) and indirect from 183 (27.3%) patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[Fibrous dysplasia in children].

The authors report a series of 19 children (ten boys and nine girls) presenting fibrous dysplasia with an average follow-up of 7 years 10 months. Twenty five bones were involved. The average age at diagnosis was 9 years (range 3 years to 14 years). Fatigue fractures and pains were the main reasons for consultation. The most frequent anatomic sites were the femur, the tibia and the humerus. In six cases it was decided to simply watch the children without any treatment. The clinical results were good for 18 children. In two cases the initial radiological lytic aspect remained at the longest follow-up. Nine complications (among which two iterative fractures and three recurrences) occurred. None of the cases developed malignant transformation. The authors discuss the different possibilities of treatment with a review of the literature.

Adolescent↗