Biomedical subjects
Publications and source records attributed to M Tynan.
Thirteen patients underwent transcatheter closure of coronary artery fistulas using interlocking detachable coils alone or combined with fibered coils. Complete occlusion was achieved in 92% of patients; although inadvertent embolization of coils occurred in 23% of patients, all these coils were easily retrieved using snares.
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Twenty-three patients, ranging in weight between 4.9 and 74 kg, underwent stent implantation in branch pulmonary arteries. At first, high-pressure balloons were used for stent implantation but, because of stents slipping off the balloons, subsequently in eight patients, aged 2-18 years and weighing 11-72 kg, Olbert balloons were used. Fifteen stents were implanted in 11 vessels in these 8 patients. No instance of stent slippage occurred during introduction through the sheath or when the stent was passed around the curves of the right heart. In one patient, the fully expanded stent slipped over the wire into the main pulmonary artery. This occurred because of undersizing of the stent. The stent was re-advanced into position and expanded using a larger balloon. No significant complications occurred with these balloons. The use of Olbert balloons for stent implantation in branch pulmonary arteries is recommended.
Balloon dilation is disappointing in maintaining patency of the arterial duct. In neonatal lambs, stent implantation in the arterial duct results in significantly larger ducts with greater pulmonary blood flow than balloon dilation. Little is known, however, about the duration of duct patency after stent implantation. The outcome of stent implantation into the arterial duct in 12 lambs was observed over a period of 1 to 24 months. Stents (Wallstent in 9, Tower stent in 3) were implanted after recanalizing the occluded duct at 2 to 7 days of age. Heparin was given only during the procedure, but no further anticoagulants were used. Angiographic or postmortem evaluations were made at 1, 1.5, 2, 3, 4, 6, 12, 16, and 21 months in a subgroup of 9 lambs who did not undergo reinterventions. The duct was patent in all these except for one studied at 16 months. Neointima initially developed in the center of the stent before extending toward the orifices, eventually burying the metal strands in contact with the wall. From 4 to 6 months onward stenoses were present inside some of the stents. When the stent did not protrude into the aorta, neointima extended over the duct orifice. Metal strands that were not in contact with the duct wall were incompletely covered with endothelial cells, platelets, and fibrin strands, but no thrombi were noted. Late balloon dilation of the stented duct was performed in two lambs increasing the pulmonary artery blood flow. In one lamb the neointimal lining was successfully removed at 14 months with an atherectomy catheter. Stent implantation into the arterial duct can maintain patency up to 21 months and could be considered as an alternative to neonatal systemic to pulmonary artery shunt operations. Neointimal proliferation and stenosis formation, however, is a major limitation that may eventually lead to a reduction in the pulmonary artery blood flow.
The present commercial market supports many nonsteroidal endocardial pacing leads of differing construction. In order to compare the performance of these configurations, we studied the long-term pacing properties of three representative lead types by randomized clinical trial in 99 patients undergoing a first elective VVI implant. Thirty-one patients received sintered platinum leads, 36 activated pyrolytic carbon leads, and 32 vitreous carbon leads. All received generators capable of noninvasive threshold testing. Acute sensing parameters were R wave amplitude and ST segment elevation measured from the endocardial electrogram. Noninvasive voltage thresholds were measured at implantation, 2 days, 1, 3, and 6 months, and yearly thereafter for 5 years. There were no significant differences between leads in pacing or sensing capabilities at implantation. All three demonstrated similar increases in thresholds, peaking at 1 month, then falling to a plateau by 6 months and did not vary significantly thereafter. There were no significant differences in thresholds between leads during 5 years of follow-up. The lowest mean threshold at 5 years was 0.93 V at 0.5 ms. This study suggests that: (1) although these lead types all perform well, none offers any particular clinical advantage over another; (2) the degree of early threshold peaking precludes immediate postimplant output reduction, but later thresholds are sufficiently low to enable reductions in pacing output; (3) safe low energy pacing requires greater attention to the lead-generator combinations; (4) data obtained at subsequent annual follow-up provided no additional useful clinical information to that obtained at 1 year; and (5) in the absence of other differences, cost can be the deciding factor in lead selection.
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Prenatal diagnosis of a congenital coronary artery fistula between the right coronary artery and right ventricle was made by colour Doppler echocardiography at 20 weeks of gestation. Its progression was monitored by serial echocardiography throughout pregnancy and postnatally.
OBJECTIVE: To assess the outcome of arterial duct occlusion with coils chosen according to the duct morphology. DESIGN: Retrospective study. SETTING: Paediatric cardiology centre. PATIENTS: Coil occlusion was attempted in 57 patients aged 0.5 to 15 (median 3.7) years and weighing 5-59 (median 14) kg between January 1991 and December 1995. A residual leak was present in 8 patients after umbrella closure and in 4 patients after duct ligation. METHODS: Coils of 4 different types were implanted through 4 or 5 F femoral artery catheters. Platinum or Interlocking Detachable 0.018 inch coils were deployed completely inside tubular ducts. Gianturco or PDA controlled release 0.038 inch coils were implanted to straddle short, post ligation and post umbrella ducts. RESULTS: Coil implantation was successful in 54/57 patients. At 1 year the cumulative occlusion rate was 53/57 ducts (93%) on an intention to treat analysis. A single coil was implanted in 37 (69%), 2 coils in 10 (19%), 3 coils in 3 (5%) and 4 coils in 4 (7%) of the 54 successful procedures. Duct occlusion was documented at the end of the procedure in 31%, by the following day in 83%, by 6 weeks in 87%, by 6 months in 96%, and by 1 year in 98%. Coil embolisation occurred in 6/58 procedures (10%), with a 50% rate in the first year of implantation (1/2 patients) falling to 7% in the last year (3/42 patients). All embolised coils were easily retrieved. CONCLUSIONS: Occlusion of small to moderate size arterial ducts, including residual post umbrella or post ligation ducts, was readily accomplished by coils selected according to the duct anatomy. This has both cost and practical benefits.
Enlargement of the peroneus longus muscle is a common occurrence in patients with forefoot pes cavus, and may contribute to the cavus deformity. The present study compares the morphology of up to five lower leg muscles from 17 patients with forefoot pes cavus with those of normal muscles. Eight cases had an identifiable neurogenic cause for the cavus. In four cases of hereditary motor-sensory neuropathy, the tibialis anterior showed more severe damage than the peroneus longus. In two cases of cerebral palsy, fibre atrophy and increased oxidative enzyme activity were observed. In nine clinically idiopathic cases, the histological appearances ranged from normal to generalised fibre atrophy or hypertrophy in individual muscles. There was a trend for the mean fibre area to be greater in peroneus longus than in tibialis anterior in six of the idiopathic group of patients. The muscle cross-sectional area on magnetic resonance imaging was correlated closely with the mean fibre area measured on tissue sections. In idiopathic forefoot pes cavus, fibre hypertrophy in peroneus longus (relative to tibialis anterior) may contribute to the cavus deformity. Muscle fibre hyperplasia may contribute to the peroneal muscle enlargement in Friedreich's ataxia. In none of the cases was peroneus longus enlargement due to fat or fibrous tissue replacement.
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Oxygen free radicals, such as the superoxide anion, are known to mediate damage to the cerebral microcirculation following traumatic brain injury. The purpose of this study was to determine if superoxide dismutase (SOD), a scavenger of superoxide anion, could alter posttraumatic cortical blood flow. Following barbiturate anesthesia, rats were surgically prepared for moderate fluid percussion brain injury. Cortical blood flow contralateral to the site of injury was measured using laser-Doppler flowmetry. Laser-Doppler flowmetry assesses flow by measuring cell volume and velocity, which are multiplied electronically to give flow. Starting 10 min before injury, animals received either superoxide dismutase (24,000 U/kg bolus, followed by continuous infusion of 1600 U/kg/min) or an equal volume of saline. Blood pressure, heart rate, and cortical blood flow were measured up to 1 h posttrauma. Rats receiving superoxide dismutase had significantly higher cortical blood flow posttrauma (F = 6.91, p < 0.02). One hour posttrauma, the blood flow in SOD-treated rats was 89 +/- 8% of preinjury baseline, whereas this value was only 66 +/- 6% of control in saline-treated rats. SOD caused not only greater blood velocity but also less reduction in cortical blood volume after injury. There were no significant differences between the groups with respect to blood pressure or heart rate. This study further supports the role of oxygen radical-mediated cerebrovascular dysfunction following traumatic brain injury and is the first to show the beneficial effect of SOD on cortical blood flow following fluid percussion brain injury.
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The outcome of 40 consecutive newborns and children with normal cardiac connections presenting with unoperated (i.e., no previous surgical or balloon dilation treatment) aortic coarctation since the introduction of balloon dilation as a treatment option (group A) was compared retrospectively with that of a similar cohort of 38 patients (group B) presenting in the period immediately before the introduction of balloon dilation. Group A consisted of 18 newborns (< 30 days) and 22 children and Group B consisted of 20 newborns and 18 children. In group A, 30 patients had balloon dilation but 10 underwent surgery because of parental preference, unfavorable anatomy or for logistic reasons. Group B had conventional surgical repair by various methods. All patients were followed up clinically by Doppler echocardiography and, when possible, by magnetic resonance imaging. Repeat cardiac catheterization was only performed in those with suspected recoarctation. Survival and freedom from reintervention were investigated using Kaplan-Meier analysis. Patients of all ages in group A and those who had balloon dilation were at higher risk for reintervention (25 and 30%, respectively, at 1 year) than those in group B or those who had surgery (20 and 18%, respectively, at 1 year). Mortality was not significantly different between groups A and B, but there were 2 neonatal deaths directly attributable to the dilation procedure. Two patients developed aneurysms after dilation. Balloon dilation is an effective treatment for unoperated coarctation, but the recoarctation rate appears to be higher than for surgery.
OBJECTIVES: We sought to determine the incidence of late perfusion defects attributable to coronary artery mobilization in patients undergoing anatomic correction for complete transposition of the great arteries. BACKGROUND: Anatomic correction (arterial switch procedure) is currently the surgical treatment of choice for complete transposition. From its conception, there has been concern about the impact on myocardial perfusion of the coronary artery mobilization and reimplantation involved in the correction. Previous studies have demonstrated myocardial perfusion defects in patients after correction, although a causal relation between coronary mobilization, and perfusion abnormality has not been established. METHODS: In a case-comparison study designed to test this hypothesis, 29 children underwent imaging with technetium-99m 2-methoxy isobutyl isonitrile (technetium-99m mibi). Ten had undergone anatomic correction (arterial switch group; interval from operation 6.9 +/- 1.42 years [range 4.9 to 9.1]); 9 had required noncoronary open heart surgery for other cardiac lesions (post-bypass group; interval from operation 5.6 +/- 3.6 years [range 1.0 to 13.25]); and 10 had had no surgical procedure (control group). The latter group comprised children with atrial or ventricular septal defects who required a radionuclide study for shunt calculation. Planar studies were performed in all 29 children, and additional tomographic acquisition was achieved in 25. To assess reversibility of perfusion defects both an exercise and a rest planar study were performed in the arterial switch group. RESULTS: Perfusion abnormalities were observed in seven of the nine children in the postbypass group and in all 10 children in the arterial switch group. The frequency of perfusion defects in these two groups was similar, with at least 25% of the tomographic segments reported being abnormal. The control group had significantly fewer defects than the other two groups (p = 0.02), with only 8% of the tomographic segments judged to be abnormal. In all except one patient in the arterial switch group, the segments reported as abnormal on the planar exercise study were either abnormal or equivocal on the rest study, indicating a fixed abnormality. CONCLUSIONS: Although the precise etiology of these perfusion abnormalities cannot be defined from this study, these data suggest that their origin is related more to the insult of open heart surgery itself than to the coronary manipulation involved in the arterial switch procedure. The functional importance requires further study.
The Eighth Survey of Staffing in Cardiology was conducted with an index date of 30 September 1992. The total number of cardiologists in England and Wales, defined as individuals trained in the specialty and spending at least 40% of their professional time working in it, was 358. Of these 11 were part time, defined as six sessions or less, giving a number in whole time (or near whole time) equivalents of 352.5. The number of individuals increased from 1991 by 18 (5.3%). There were 71 cardiologists in Scotland and Northern Ireland, making a total for the United Kingdom of 429 individuals (423.5 whole time equivalents), which is 7.3 per million population. A total of 44 Districts serving 8.8 million people have no resident cardiologist. There has been little improvement since the 1991 survey. An additional 34 Districts with populations greater than 250,000 have only one cardiologist: we have clear evidence of inadequate provision of care in most of these, a situation that is inevitable within the resources provided. A wider threat to the provision of a satisfactory level of cardiological care throughout the United Kingdom will follow from changes in the organisation of the National Health Service and in the new requirements for training of future cardiologists because these changes will make major new demands on consultant time which cannot be met within existing resources. A crisis will be averted only if a rapid and major expansion of the consultant grade can be achieved.
BACKGROUND: Pacemaker pocket infection is a potentially serious problem after permanent pacemaker implantation. Antibiotic prophylaxis is commonly prescribed to reduce the incidence of this complication, but current trial evidence of its efficacy is conflicting. A large prospective randomised trial was therefore performed of antibiotic prophylaxis in permanent pacemaker implantation. The intention was firstly to determine whether antibiotic prophylaxis is efficacious in these patients and secondly to identify which patients are at the highest risk of infection. METHODS: A prospective randomised open trial of flucloxacillin (clindamycin if the patient was allergic to penicillin) v no antibiotic was performed in a cohort of patients undergoing first implantation of a permanent pacing system over a 17 month period. Intravenous antibiotics were started at the time of implantation and continued for 48 hours. The trial endpoint was a repeat operation for an infective complication. RESULTS: 473 patients were entered into a randomised trial. 224 received antibiotic prophylaxis and 249 received no antibiotics. A further 183 patients were not randomised but were treated according to the operator's preference (64 antibiotics, 119 no antibiotics); these patients are included only in the analysis of predictors of infection. Patients were followed up for a mean (SD) of 19(5) months. Among the patients in the randomised group there were nine infections requiring a repeat operation, all in the group not receiving antibiotic (P = 0.003). In the total patient cohort there were 13 infections, all but one in the non-antibiotic group (P = 0.006). Nine of the infections presented as erosion of the pulse generator or electrode, three as septicaemia secondary to Staphylococcus aureus, and one as a pocket abscess secondary to Staphylococcus epidermidis. Infections were significantly more common when the operator was inexperienced (< or = 100 previous patients), the operation was prolonged, or after a repeat operation for non-infective complications (principally lead displacement). Infection was not significantly more common in patients identified preoperatively as being at high risk (for example patients with diabetes mellitus, patients receiving long term steroid treatment), although there was a trend in this direction. CONCLUSIONS: Antibiotic prophylaxis significantly reduced the incidence of infective complications requiring a repeat operation after permanent pacemaker implantation. It is suggested that antibiotics should be used routinely.
OBJECTIVE: To assess the incidence and subsequent management of misplaced devices as a complication of therapeutic embolisation procedures. DESIGN: Retrospective review of case notes, cardiac catheterisation reports, and angiograms. SETTING: Tertiary referral centre for congenital heart disease. PATIENTS: 205 consecutive children and adults undergoing therapeutic embolisation for congenital heart disease in the 10 years up to 1 April 1993. This group had 231 therapeutic embolisation procedures at 241 sites using coils, umbrella devices, or detachable balloons. MAIN OUTCOME MEASURES: Incidences of misplacement and retrieval of the device; morbidity and mortality. RESULTS: The incidence of misplacement was 3% (10/332) of devices deployed and 4.3% (10/231) of procedures performed. Retrieval from distal pulmonary arteries was not attempted in two patients, but transcatheter retrieval of coils and umbrellas from systemic and pulmonary vessels, using snares or retrieval baskets, was successful in the remaining eight. There were no deaths or serious sequelae related to the procedure, but one patient required femoral arteriotomy for removal of an umbrella device retrieved only as far as the groin. In four of the five most recent cases, the misplaced device was retrieved and the therapeutic embolisation was completed at the same procedure. CONCLUSIONS: Misplacement of a device during therapeutic embolisation is a recognised complication that can be satisfactorily dealt with by transcatheter retrieval without recourse to surgery. For retrieval to be successful it is important to have a wide selection of retrieval equipment available and to be conversant with its use.
OBJECTIVE: To determine the progression rates to AIDS in women in Dublin. SUBJECTS AND METHODS: 109 HIV-1 seropositive women who presented to the Department of Genitourinary Medicine, St. James's Hospital, Dublin, were included in a retrospective analysis. Of these 101 (93%) were intravenous drug users (IVDUs), 7 were heterosexual partners of IVDUs and one had a hetero-sexual partner of no known risk group. Forty-four women (40%) had had 57 children since the time of their first known HIV seropositive test. Progression rates from CDC Stage 11/111 to AIDS are computed. Progression curves are generated according to the Kaplan-Meier method using the Statistical Analysis Software (SAS). RESULTS: The estimated cumulative progression rate at 5 years was 24% (SE 6.6%). 17 out of 109 (15.6%) developed AIDS. The mean follow up time was 2.8 years (SE 0.2). The prevalence of oesophageal candidiasis taking development of AIDS as the point in time was 9 out of 17 (53%), of Mycobacterium hominis infection (TB) 5 (29%) and of Pneumocystis carcinii pneumonia (PCP) 2 (12%). There was no statistical difference in progression rates to AIDS between those women who had children after becoming infected versus those who had none. CONCLUSIONS: Progression rates to AIDS in Irish women is higher than reported in other studies of homosexual/bisexual men, but is similar to rates estimated for both male and female IVDUs. Oesophageal candidiasis is the commonest presenting AIDS diagnosis followed by TB, while PCP is rare, contrary to the findings of similar studies in the USA.