Biomedical subjects
Publications and source records attributed to D Atar.
An unusual case of newborn unilateral dislocated hip is presented. The condition was refractory to conservative treatment. The cause was found during surgery at the age of 1 month: the adductors were replaced by myofibromatosis. The tumor was excised and at follow-up a normal hip was noted.
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The effect of magnesium deficiency on postischemic myocardial dysfunction (myocardial stunning) in an open-chest swine model was studied. Twelve swine were assigned either to low magnesium diet or control diet. Myocardial stunning was assessed by measuring regional wall thickening by epicardial Doppler before and after brief occlusion (8 min) of the left anterior descending coronary artery. Serum magnesium levels decreased significantly in the experimental group only. Glutathione levels were 42.6% lower in the magnesium deficient swine than in controls. Stunning time was significantly prolonged from 32.8 +/- 3.1 min in the control group to 43.8 +/- 4.6 min in the hypomagnesemic swine. In conclusion, magnesium deficiency is associated with prolonged recovery from myocardial stunning.
We tested the hypothesis that acute, intravenous (i.v.) magnesium (Mg2+) supplementation would protect against myocardial stunning in an in situ swine model of regional ischemia and reperfusion and that a concomitant inhibitory effect on platelet aggregation would be elicited. An open-chest model was used, with transient occlusion of the left anterior descending coronary artery (LAD) for 8 min. Regional contractile function was assessed by measuring wall thickening fraction with epicardial Doppler crystals. One control group (n = 6) and two treatment groups were studied: group I (n = 6) received 750 mg MgSO4 before occlusion; group II (n = 6) received 1 g MgSO4 after the occlusion. Both protocols produced significant hypermagnesemia. In group I, platelet aggregation was measured before and after Mg2+ treatment using platelet-rich plasma (PRP) and various agonists (ADP 5 and 10 mM and collagen 1 mg/ml). As compared with controls, both treatment groups experienced significantly less postischemic dysfunction, with systolic function returning more quickly to baseline. Furthermore, platelet aggregation was significantly decreased immediately after Mg2+ infusion. Inhibition of platelet aggregation induced by Mg2+ treatment occurs concomitantly with significant amelioration of postischemic myocardial dysfunction.
The aim of the study described here was to correlate coronary artery (CA) stenosis pressure gradients calculated by quantitative coronary arteriography (QCA) to invasively measured transstenotic pressure drops in patients with anginal symptoms and with known or suspected coronary artery disease. Furthermore, the known mathematical models are improved by introducing (1) pressure catheter-corrected minimal stenosis area, (2) modification of flow assumptions, and (3) stenosis exit angle. Included in the study were 45 patients with 61 stenoses. The visually estimated CA lesion severity in these non-complex stenoses was in the equivocal range of 40-70%. All measurements were performed after intracoronary administration of nifedipine and nitroglycerin. Stenosis dimensions were assessed from magnified cinefilms, using hand-held calipers. Highly significant overall correlation was found between measured and calculated pressure gradients with correction for the impact of the intracoronary catheter (P < 0.00001, r = 0.84). In particular, a substantial number of stenoses with haemodynamically-insignificant pressure gradients were identified by hydrodynamic calculations. In conclusion, the great majority of the coronary artery stenoses could be classified reliably by QCA as being haemodynamically insignificant or significant, respectively.
A model of coronary artery thrombosis which: (1) provides a stable thrombus; (2) incorporates intimal injury; (3) has a low mortality rate; (4) responds predictably to thrombolytic therapy, and (5) is technically simple, was developed. Intimal injury was produced proximal to a critical stenosis and followed by the infusion of a blood and thrombin mixture into the injured segment. After thrombus formation flow remained absent in all control animals (n = 7). Microscopy showed intimal injury and coronary thrombosis with platelets adherent to the subendothelium. In animals treated with tissue plasminogen activator (n = 7) flow returned to > 60% of baseline at 20.2 +/- 7.7 min and was cyclical. Mortality and complications were infrequent. This model is useful in investigations of reperfusion therapy.
This study compares the use of hand-held calipers to automated quantitative coronary arteriography in assessing coronary artery stenosis severity. 48 stenoses in the visually estimated range of 30-90% were evaluated in two orthogonal projections. Absolute stenosis dimensions and calculated transstenotic pressure gradient (PG) were compared. Hand-held calipers were of limited value in assessing absolute stenosis dimensions (SD = 0.32 mm, r = 0.80). However, the correlation found in the assessment of percent diameter stenosis (SD = 7.7%, r = 0.83) and PG (SD = 1.3 mm Hg, r = 0.83) was acceptable. In particular, the allocation into hemodynamically significant (n = 30) and nonsignificant (n = 18) stenoses, according to the criterion of a PG > 30 mm Hg, was accomplished identically by both methods.
An unusual case is presented in which minor soft tissue injury may have caused premature asymmetrical closure of the proximal tibial physis resulting in a 30 degrees genu recurvatum that necessitated corrective osteotomy. Awareness of the possibility of a hidden physeal injury in the presence of soft tissue injury and a normal radiograph may lead to its early recognition and treatment.
Myocardial stunning, defined as a reversible decrease in contractility after ischemia and reperfusion, may be a manifestation of reperfusion injury caused by free oxygen radical damage. The aim of this study was to test the hypothesis that pretreatment with coenzyme Q10 (ubiquinone), believed to act as a free radical scavenger, reduces myocardial stunning in a porcine model. Twelve swine were randomized to receive either oral supplementation with coenzyme Q10 or placebo for 20 days. A normothermic open-chest model was used with short occlusion (8 min) of the distal left descending coronary artery followed by reperfusion. Regional contractile function was measured with epicardial Doppler crystals in ischemic and nonischemic segments by measuring thickening fraction of the left ventricular wall during systole. Stunning time was defined as the elapsed time of reduced contractility until return to baseline. Coenzyme Q10 concentrations were measured in blood and homogenized myocardial tissue by high performance liquid chromatography. Plasma levels of reduced coenzyme Q10 (ubiquinol) were higher in swine pretreated with the experimental medication as compared to placebo (mean 0.45 mg/l versus 0.11 mg/l, respectively). Myocardial tissue concentrations, however, did not show any changes (mean 0.79 micrograms/mg dry weight versus 0.74 micrograms/mg). Stunning time was significantly reduced in coenzyme Q10 pretreated animals (13.7 +/- 7.7 min versus 32.8 +/- 3.1 min, P < 0.01). In conclusion, chronic pretreatment with coenzyme Q10 protects ischemic myocardium in an open-chest swine model. The beneficial effect of coenzyme Q10 on myocardial stunning may be due to protection from free radical mediated reperfusion injury. This protective effect seems to be generated by a humoral rather than intracellular mechanism.
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The effect of magnesium sulphate infusion on ex vivo platelet aggregation in 11 female Yorkshire swine was observed using platelet-rich plasma and different agonists (ADP 5 mM; ADP 10 mM and collagen 1 mg/ml). Infusion of 1 g MgSO4 over 1 h produced a significant decrease in platelet aggregability. A dose-dependent effect of different ADP concentrations on platelet aggregation was noticed. Platelet inhibition was most consistent when using ADP 5 mM. We estimate this concentration of agonist as optimal in swine. The swine model is a good choice for investigation of in vivo platelet activation, especially with regard to cardiovascular research. We conclude that there is an inhibitory effect of supplemental magnesium on ex vivo platelet aggregation in swine with initial normomagnesaemia.
Two groups of patients who underwent soft-tissue release of clubfoot are compared. In group I, internal fixation (two Kirschner wires) was used for 6 weeks to retain correction of clubfoot. In group II, no internal fixation was used. Patients from the two groups were operated on by one surgeon using the same procedure. Because there was no statistically significant difference in functional result between the two treatment groups (P = .08; Mann-Whitney Test), the authors recommend avoiding internal fixation (with all the associated problems) in cases of uncomplicated clubfoot, and encourage early removal of the cast and frequent manipulations to prevent stiffness of the joints and reduce the recurrence rate.
Thirty patients had distal hamstring release with modified Green technique: 21 spastic diplegics, 8 spastic quadriplegics, and 1 spastic hemiplegic. The average age at the time of surgery was 6.9 years. The average follow-up was 2.5 years. Average improvement of 40 degrees in the popliteal angle was noted at follow-up. Twenty-three patients improved their gait pattern. Nine patients improved one level of walking ability. A popliteal angle over 50 degrees was defined as recurrent. On the basis of this criterion, the recurrence rate was 12.5% (7/56 knees). In all recurrent cases, however, the tightness was less severe than preoperatively. Noncompliance on the part of parents was the chief reason for recurrence. Distal hamstring release is an effective procedure in treatment of cerebral palsy patients with flexion deformity.
The navicular position was evaluated (according to Simons' criteria) on anteroposterior and lateral roentgenograms of 45 clubfeet that were treated with complete soft-tissue release without internal fixation. The evaluation was performed an average of 28 months after surgery. Position of the navicular correlates well with the functional rating score system. Navicular position can be viewed as an indicator for clubfoot correction. Internal fixation of the talonavicular joint was correlated with favorable correction of deformity.
The reoperated clubfeet of 29 children aged one to 12 years were reviewed. The surgical procedure most often used in revision surgery was recomplete soft-tissue release alone or combined with plantar release, calcaneocuboid fusion, and capsulotomies of the navicular-first cuneiform-first metatarsal joint. In 27 of 29 feet, acceptable results were achieved. Nineteen were excellent and good results. An algorithm that suggests surgical solutions to a variety of clubfoot deformities in different age groups has been developed, as well as an objective rating system, to evaluate the long-term results of revision surgery of clubfeet.
A transmetatarsal pin was used as part of an Ilizarov apparatus to correct equinovarus deformity of a foot in a 7-year-old patient. The pin created synostosis between the metatarsal bones. The synostosis led to persistent flattening of the transverse arch of the foot, producing a painful gait. To avoid this problem, we recommend that the metatarsal wire be placed only through the first and fifth metatarsals rather than through the neighboring metatarsals.
Differences in the care of the pins used in association with the Ilizarov apparatus and technique are found in various countries and institutions. During a recent visit to the Ilizarov Institute in Russia, the methods of caring for the Ilizarov pins were extensively investigated and documented. The U.S. infection rate at pin sites has been reported to be nearly 10%. No specific infection rate has been reported from Russia. What constitutes an infection at the Ilizarov Center in Kurgan was investigated, as were methods of treatment. Our conclusion is that pin care in Russia is conducted under a more vigorous and stringent regimen, but less often, than in the United States. Soviet record keeping is different, and therefore the infection rates cannot be compared. In Kurgan, specific diligence is exercised in addressing the problems at each pin site. Treatment is directed toward alleviating these problems.
Clinical examination and plain roentgenograms have been the main methods of diagnosis and treatment of developmental dysplasia of the hip. Occasionally, concentric reduction cannot be achieved, or the reduction is questionable. A dynamic arthrogram can add more information but is usually performed under general anesthesia. "Mini" computed tomographic imaging demonstrates the femoral head-acetabulum relationship more accurately and produces minimal radiation. Three-dimensional computed tomography is useful in older children, in whom all sections are ossified. Magnetic resonance imaging, particularly 3-D magnetic resonance imaging, demonstrates the nonossified structures. It is the best method of visualization in developmental dysplasia of the hip. The disadvantages of this method include its cost and the lack of dynamic imaging. In the future, new software will overcome these shortcomings.