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Biomedical subjects

M Dick

Publications and source records attributed to M Dick.

At least 91 records · Page 5Linked to original sources
PubMed1988

Comparison of single and double balloon valvuloplasty in children with aortic stenosis.

To compare the effectiveness of the single and double balloon techniques, the short-term results of percutaneous balloon valvuloplasty were assessed in two consecutive groups of children with valvular aortic stenosis. In 16 children (aged 3 months to 17 years) the single balloon technique was utilized; the ratio of balloon diameter to valve anulus diameter was 0.96 +/- 0.03 (mean +/- SEM). In 11 children (aged 3 months to 21 years) the double balloon technique was utilized in which two balloons are positioned across the valve and inflated simultaneously; the ratio of the balloon diameter sum to valve anulus diameter was 1.32 +/- 0.05. The groups were similar in age, weight, cardiac output, prevalvuloplasty gradient and valve anulus diameter. Overall, valvuloplasty reduced the peak systolic gradient by 53% from 80 +/- 4 to 38 +/- 3 mm Hg (p less than 0.0001). In the single balloon group the gradient decreased from 82 +/- 6 to 46 +/- 4 mm Hg (p less than 0.0001), whereas in the double balloon group the gradient decreased from 76 +/- 5 to 26 +/- 4 mm Hg (p less than 0.0001). The peak systolic gradient after valvuloplasty was 43% lower in the double balloon group (p less than 0.01). Furthermore, the single balloon technique reduced the gradient by an average of 43% compared with a 67% reduction with the double balloon technique (p less than 0.001). The short-term complications of valvuloplasty were similar, with an increase in aortic insufficiency occurring in three children in each group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Obstruction to left coronary artery blood flow secondary to obliteration of the coronary ostium in supravalvular aortic stenosis.

Supravalvular aortic stenosis is characterized by obstruction of the left ventricular outflow tract distal to the aortic valve, and may result in diminished coronary artery blood flow. This report describes the cases of 2 patients in whom obstruction to left coronary artery flow was caused by obliteration of the coronary ostium itself. This mechanism differs from the more commonly recognized cause--valve leaflet adhesion to the obstructing ridge of aortic tissue. The coronary artery obstruction found in these 2 patients required direct enlargement of the left coronary ostium in both. This mechanism of impaired coronary artery flow deserves emphasis, as traditional methods of extended patch aortoplasty may fail to relieve the coronary ostial narrowing.

Aorta↗
PubMed1988

Interactions in the discrimination and absolute judgement of orientation and length.

An asymmetric model is described for interactions in the perception of two dimensions (length and orientation) of a single visual stimulus. Two methods were used to test these interactions, and models for the interpretation of the possible outcomes of these tests are discussed. A length discrimination task showed facilitation (decreased reaction time) when orientation was covaried with length, and interference (increased reaction time) when random orientation variation was introduced. A smaller effect was seen when length was varied in an orientation discrimination task in a correlated or random fashion. Analysis of sequential effects showed that reaction times are fastest on repetition trials and are slowed by either the need to change the response or the need for additional sensory processing. With the second method, it was found that the amount of information transmitted in the estimation of orientation was not affected by the introduction of the redundant dimension of length, but that there was a significant gain in the amount of information transmitted in the estimation of length by the addition of the redundant dimension of orientation. It is concluded that orientation is probably a perceptual primitive of the visual system whereas length is a computed variable.

Adult↗
PubMed1988

Endotoxinaemia in sickle cell disease.

Fifty-nine children with sickle cell anaemia (HbSS) or associated haemoglobinopathies were studied prospectively using a chromogenic Limulus amoebocyte lysate assay to detect circulating endotoxin. The 41 children with HbSS (mean age 8 years 9 months) had more serious disease than the 18 with HbSC disease (n = 14) or HbS-beta-thalassaemia (n = 4) (mean age 7 years 2 months), with a greater degree of splenomegaly, lower haemoglobin, and higher white cell counts, platelet counts and bilirubin values (P less than 0.05 for all). Twenty-nine children with HbSS had evidence of poor reticuloendothelial function, with red cell pitting of greater than or equal to 2%. Three of these 29 had low levels of endotoxin in plasma (0.12-0.24 endotoxin units (EU)/ml); two were clinically well, one had a painful crisis. Eight of 18 children with other sickle haemoglobinopathies had greater than or equal to 2% pitted red cells; none was endotoxinaemic. Therefore, in 37 patients with reticuloendothelial dysfunction, three were endotoxinaemic; all had sickle cell anaemia. Although not statistically significant, this suggests that endotoxinaemia may occur predominantly in patients with reticuloendothelial dysfunction, and is compatible with the hypothesis that systemic endotoxinaemia can derive from the intestine especially when reticuloendothelial function is depressed.

Adolescent↗
PubMed1988

Concealed paroxysmal atrioventricular block: diffuse congenital atrioventricular conduction system disorder with nonpropagated His bundle depolarizations.

A 2 1/2-year-old girl with bradycardia and left bundle branch block at birth began to experience "night cries" when deeply asleep. Electrophysiological study demonstrated congenital diffuse atrioventricular conduction disease with concealed paroxysmal atrioventricular block, nonpropagated His bundle depolarizations, severe sinus node abnormality, and a low atrioventricular junctional escape rhythm with probable reciprocation. After pacemaker implant, the "night cries" ceased.

Bradycardia↗
PubMed1988

Repair of interrupted aortic arch in infancy.

Twenty-one patients undergoing repair of interrupted aortic arch between December of 1979 and January of 1987 were reviewed to determine the cause(s) of late morbidity and mortality. Ten underwent staged repair, and 11 had complete repair including all coexisting defects at the initial operation. Sixty-two percent are alive and clinically well 6 months to 6 years after the initial operation. Among the five patients who died late postoperatively, four had severe left ventricular outflow tract obstruction. Two other patients have had surgical relief of severe subaortic stenosis. In addition, significant recurrent or residual coarctation was found in four patients; it was relieved by balloon angioplasty in two patients, and two had surgical repair. None of the most recent seven patients, however, have had a residual ascending-descending aortic gradient. Careful follow-up for the detection of previously masked or newly developed left ventricular outflow tract obstruction is imperative and may be lifesaving.

Aorta, Thoracic↗
PubMed1988

Arterial repair for transposition of the great arteries and large ventricular septal defect in early infancy.

Arterial repair for transposition of the great arteries and large ventricular septal defect (VSD) may be superior to atrial correction, but the risk of either approach in early infancy has been high. The results of early correction were therefore assessed in 12 children with transposition of the great arteries and a large VSD who underwent arterial repair. Patients ranged in age from 3 to 90 days (median age, 19 days) and in weight from 2.5 to 3.7 kg. The VSD was infundibular in eight, inlet in three, and muscular in one. Coronary artery anomalies were present in five patients, including one patient with a single left coronary artery. There was one early death (8%) in the only patient with a pulmonary artery band. There were no late deaths. The 11 survivors have been followed up from 2 to 59 months (mean follow-up period, 20 months) and remain free of cardiac symptoms. Catheterization (n = 5) and Doppler echocardiography in all patients show no significant left ventricular outflow obstruction, aortic insufficiency, or residual VSD. Catheterization documented normal pulmonary artery pressure and unobstructed coronary arteries. Only one patient had significant pulmonary stenosis and underwent successful reoperation. These data indicate that arterial repair and VSD closure can be successfully performed in early infancy with low mortality and morbidity. Repair in this age group is advocated before changes of pulmonary vascular disease occur.

Angiography↗
PubMed1987

Gall stones in sickle cell disease in the United Kingdom.

The prevalence of gall stones was studied prospectively by abdominal ultrasound examination in 131 patients with sickle cell disease aged 10-65 years. Of 95 patients with homozygous sickle cell disease, 55 (58%) had gall stones or had had a cholecystectomy. Gall stones were present in four out of 24 (17%) patients with haemoglobin S + C disease and two out of 12 (17%) with haemoglobin S beta thalassaemia. The presence of gall stones was not related to sex, geographical origin, or haematological variables and was not associated with abnormal results of liver function tests. Symptoms typical of biliary colic were reported by 32 out of 47 adult patients with gall stones, and cholecystitis or cholestasis was diagnosed in 18. Cholecystectomy was performed in 29 patients with good relief of symptoms in most cases. Postoperative complications were common, occurring in 10 of the 28 patients who could be evaluated, but not generally serious; they were considerably lessened by a preoperative exchange transfusion that reduced the haemoglobin S concentration to below 40%. It is suggested that all patients with sickle cell disease should be screened for gall stones and that elective cholecystectomy should be performed in those with symptoms or complications.

Adolescent↗
PubMed1987

Parallel and serial processes in motion detection.

Apparent motion was used to explore humans' ability to perceive the direction of motion in the visual field. A marked qualitative difference in this ability was found between short- and long-range motion. For short-range motion, the detection of the direction of motion is characterized by parallel operation over a wide visual field (that is, detection performance is independent of the number of objects in an array). When the positional displacement is large relative to an object's size, the direction of motion is detected in a serial manner. The process of detection is limited in this case by the ability to detect other events, such as appearance and disappearance of an object, and the ability to compute their spatio-temporal relations. The results are consistent with a previously suggested division of the motion detection system into short- and long-range processes. The direction of short-range motion can be perceived in parallel (preattentively), whereas long-range motion is attentive and requires more complicated computations. It seems that the detection of long-range motion is a conjunction task, combining the detection of disappearance and appearance.

Humans↗
PubMed1987

Quinidine syncope in children.

Quinidine syncope and factors associated with it are well known among adult patients treated for cardiac arrhythmias. To define factors that may influence the occurrence of syncope in children taking quinidine, the clinical, anatomic, electrocardiographic, roentgenographic and pharmacologic data were compared in six patients with syncope (Group A) and 22 patients without syncope (Group B). There was a significant (chi-square = 10.2, p = 0.001) relation between heart disease and quinidine syncope: all six Group A (syncopal) patients had heart disease whereas 15 of the 22 Group B (non-syncopal) patients had no structural heart disease. In contrast, no significant difference was noted between Group A and Group B patients in mean age (11.4 versus 11.4 years), mean quinidine serum concentration (2.9 versus 2.3 micrograms/ml), mean corrected QT interval before quinidine (0.43 versus 0.40 second) or mean corrected QT interval during quinidine therapy (0.46 versus 0.46 second) or between those taking digitalis and those not. Two of the six Group A (syncopal) patients died during therapy, one 6 days after initiating therapy and one suddenly at home 6 months after beginning quinidine. Another two of the six Group A patients exhibited hypokalemia (both 2.9 mEq/liter) at the time of syncope, 2 weeks and 6 months, respectively, after initiation of quinidine therapy; both survived. Syncope occurred within 8 days of initiation of quinidine therapy in three of the six patients. Sustained ventricular tachycardia was observed during quinidine associated arrhythmia in three of six patients with syncope; nonsustained ventricular tachycardia or complex ventricular ectopic activity while on this therapy was observed before syncope in the other three patients in Group A.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1987

Percutaneous balloon angioplasty for native coarctation of the aorta.

Twenty-six children, aged 5 weeks to 14.7 years, underwent percutaneous balloon angioplasty for a discrete native coarctation of the aorta. The procedure reduced the systolic coarctation gradient acutely in all children. The mean systolic gradient decreased by 75%, from 48.6 +/- 2.4 before to 12.3 +/- 1.9 mm Hg after angioplasty (p less than 0.001). Long-term results were evaluated in 14 children by follow-up catheterization 12 to 26 months (mean 15.3) after angioplasty. At follow-up, the residual gradient averaged 11.7 +/- 3.7 mm Hg (range -5 to 36) and had not changed from that measured immediately after angioplasty (p = 0.64). Compared with preangioplasty values, the systolic pressure in the ascending aorta had improved substantially at follow-up (116.0 +/- 3.2 versus 143.9 +/- 3.1 mm Hg, p less than 0.001). On the basis of follow-up data, two groups of children were identified: Group 1 consisted of nine children with a good result, defined as a residual gradient less than 20 mm Hg and no aneurysm; Group 2 consisted of five children with a poor result, four with a residual gradient greater than 20 mm Hg (range 25 to 36) and one with an aneurysm at the dilation site. There was no statistical difference between the two groups in age at angioplasty, balloon size, ratio of balloon to isthmus diameters, follow-up duration, heart rate or cardiac output. However, of the four children with a residual gradient greater than 20 mm Hg, two were the youngest in the study, and in two the aorta was inadvertently dilated with a balloon 4 to 5 mm smaller than the isthmus diameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Paradoxical hypertension after repair of coarctation of the aorta in children: balloon angioplasty versus surgical repair.

The incidence and possible causes of paradoxical hypertension were evaluated in eight children who underwent balloon dilatation and seven children who underwent surgical repair of coarctation of the aorta. Both procedures resulted in a significant reduction in the coarctation gradient. Both systolic and diastolic blood pressures increased in the surgical group after repair, whereas systolic pressures decreased and diastolic pressures remained unchanged after balloon angioplasty. In the surgical group, but not in the balloon angioplasty group, plasma catecholamines and plasma renin activity rose during the first 2 days after relief of the coarctation. The data presented in this report support the hypothesis that the sympathetic nervous system and the renin angiotensin system are important mediators of the paradoxical hypertension that occurs after surgical repair of coarctation. Furthermore, balloon angioplasty of coarctation of the aorta does not stimulate either system and thus paradoxical hypertension is not a complication of this procedure.

Angioplasty, Balloon↗