Balloon angioplasty for the treatment of native coarctation: results of Valvuloplasty and Angioplasty of Congenital Anomalies Registry.

Data on dilation of 141 native coarctation procedures in 140 patients between 3 days and 29 years of age were submitted to the Valvuloplasty and Angioplasty of Congenital Anomalies (VACA) Registry. Fifteen patients were less than 4 weeks old, 15 between 1 month and 12 months old and 110 patients over 1 year old. The immediate results confirmed that native coarctations could be effectively dilated in both infants and older children. The data do not support any conclusions concerning balloon size relative to results or complications. There were 24 complications (17%) reported with 1 death after 3 days and after intervening surgery in an infant with associated persistent ductus arteriosus. There were 2 early and 6 late "aneurysms" reported after the coarctation dilations with insufficient immediate and no long-term information about the significance of these. The VACA Registry data suggest that dilation of native coarctations can be performed effectively and relatively safely but do not answer whether this procedure should be performed.

Thallium-201 myocardial imaging in anomalous left coronary artery arising from the pulmonary artery. Applications before and after medical and surgical treatment.

Thallium-201 myocardial imaging was performed on six patients with an anomalous left coronary artery arising from the pulmonary artery. Initial images in three children (aged 4 months, 12 months and 2 1/2 years, respectively) demonstrated anterolateral perfusion defects in agreement with the electrocardiographic localization of infarction. Repeat imaging in two patients 2 to 3 months later, after clinical improvement with anticongestive therapy, demonstrated a reduction in the perfusion defect. In 3 other patients (aged 16, 16 and 20 years, respectively) thallium-201 scans performed during exercise stress demonstrated normal myocardial perfusion 7 to 15 years after operation (ligation of anomalous left coronary in two, ligation plus bypass graft in one). Thallium-201 imaging appears to be helpful in monitoring changes in myocardial perfusion before and after medical or surgical treatment of an anomalous left coronary artery, and may shed light on the pathophysiology of the defect. A possible practical limitation of thallium-201 imaging in this condition is the difficulty of imaging subendocardial infarction.

Echocardiography by telephone--evaluation of pediatric heart disease at a distance.

A 24-hour telephone transmission service was established for pediatric echocardiography between a general hospital and a children's hospital 500 km distant. Studies were transmitted in real time for interpretation and diagnosis by a pediatric cardiologist. In the first 9 months of operation, studies were transmitted for 18 children with a median age of 5 months. Image and sound quality was excellent. Complete segmental diagnosis was made in 16 patients, and further study was needed in 2 others. In 8 of the 18 patients a new diagnosis was provided, and in 10 patients diagnosis was confirmed. Congenital heart disease was found in 12 patients, other heart disease in 2 and a normal heart in 4. The population included 2 fetuses whose echocardiograms showed hypoplastic left heart and intracardiac tumor. In 4 patients transport was avoided. This is the first report of echocardiographic transmission by telephone, which was shown to be clearly feasible, cost-effective and diagnostic. It provides emergency access to specialist expertise, and may avoid hazardous and expensive transport of ill children.

Cardiac rhythm, rate and ventricular repolarization properties in infants at risk for sudden infant death syndrome: comparison with age- and sex-matched control infants.

Using 24-hour ambulatory electrocardiographic recordings and 120-lead body surface potential maps, prevailing cardiac rate and rhythm, incidence and frequency of dysrhythm and rate and pattern of ventricular repolarization at the body surface were compared in 17 infants at risk for sudden infant death syndrome (SIDS) and 17 age- and sex-matched control subjects. Sinus rhythm was the prevailing rhythm in both study groups and there were no intergroup differences in average overall awake or asleep sinus rates, nor in temporal variability of sinus rate. Atrial and ventricular ectopic activity were equally uncommon in both study groups. Although there were smooth and bipolar body surface distributions of ST-T and QRST time integrals in both study groups, the average rate of ventricular repolarization (QTc), measured from the 12-lead electrocardiogram, 120-lead body surface potential maps and 24-hour electrocardiography, was consistently shorter in the at-risk group than in the control group. However, temporal variability of QTc was not different between the 2 groups. Thus, significant cardiac dysrhythm and QT prolongation are not found in infants at increased risk for SIDS. Rather, there is an abbreviated ventricular repolarization interval in at-risk infants. In combination with the findings of intergroup similarity of average sinus rate and temporal variability of sinus rate and ventricular repolarization rate, the data suggest a subtle, constant difference in cardiac autonomic activity, most likely an increase in sympathetic tone, in at-risk subjects. The role of this altered cardiac autonomic activity in the causation of SIDS remains undetermined.

Spectral analysis of the EMG and diaphragmatic muscle fatigue during periodic breathing in infants.

Periodic breathing occurs commonly in full-term and preterm infants. The mechanisms which switch breathing on and off within a cycle of periodic breathing are not certain. Since immature infants may experience diaphragmatic muscle fatigue, one potential switching mechanism is fatigue. Power spectra of the electromyogram, uncontaminated by the electrocardiograph artifact, were studied for evidence of diaphragmatic muscle fatigue during spontaneous periodic breathing in infants. A fall in the high-frequency (103-600 Hz) power and an increase in the low-frequency (23-47 Hz) power during periodic as compared with normal breathing would indicate fatigue. This effect was not observed in any of the infants studied. Hence, there is no evidence that periodic breathing is the result of diaphragmatic muscle fatigue. This finding suggests that the effect of drugs such as theophylline in eliminating periodic breathing may be unrelated to the fact that they also reduce fatigue.

Reverse systolic flow in dilated pulmonary arteries demonstrated by colour Doppler imaging.

OBJECTIVE: To compare patterns of reverse systolic flow in pulmonary arteries in children with dilated and normal pulmonary arteries. DESIGN: Retrospective survey. SETTING: Tertiary pediatric cardiology referral centre. PATIENTS AND METHODS: Colour Doppler images were reviewed on 45 children, aged three months to 17 years, with normal or dilated main pulmonary arteries. The patients included were unoperated, and had isolated lesions and good parasternal short axis colour Doppler images of the main pulmonary artery with no significant pulmonary insufficiency. There were 19 patients with idiopathic dilation of the pulmonary artery, seven with moderate sized atrial septal defect, seven with moderate pulmonary valve stenosis, two with pulmonary hypertension and 10 children who were normal. Reverse flow was identified by adjacent red and blue areas without aliasing. RESULTS: Reverse systolic flow extending into early diastole was seen in 27 of the 35 patients and in two of 10 normals (P = 0.003). The main pulmonary artery was substantially dilated in the patient group compared with normals. CONCLUSIONS: Significant reverse systolic flow was found in main pulmonary arteries dilated idiopathically, or from pressure or volume overload. Reverse flow may be related to excessive capacitance of the main pulmonary artery in these patients.

Follow-up after patch aortoplasty for coarctation of aorta.

BACKGROUND: Patch aortoplasty (PA) for coarctation of aorta (COA) can lead to aneurysm formation at the repair site. X-ray, echocardiogram and computed tomography are unreliable for diagnosis of this complication. OBJECTIVE: To evaluate prospectively patients with PA for COA by magnetic resonance imaging (MRI) to detect presence of aneurysm at the repair site. DESIGN: All patients who underwent PA at the authors' institution were identified. MRI was performed in transverse and long axis oblique views on all patients except those who had, or were going to have, aortic angiography for other reasons. Details of the surgical procedure were obtained from the hospital records. RESULTS: Of the 18 patients studied, 15 had MRI and three had aortic angiography. Age at PA ranged from one week to 13.3 years (mean 6.3 years). The interval from PA to MRI or angiography was 9.5 years (range four to 12.5). No aneurysm was detected in any patient. Recoarctation was diagnosed in two patients not previously suspected but discovered on MRI. At PA the intimal shelf causing coarctation was either not excised or only minimally trimmed in 14 of 15 instances. CONCLUSIONS: The incidence of late aneurysm formation following PA for COA is low in the authors' patients, possibly due to minimal intimal damage at repair, although these patients should be followed longer. MRI was useful for assessment of aneurysm and restenosis.

Infantile hypertrophic cardiomyopathy with QT prolongation.

A neonate presented with neonatal myocardial dysfunction and long QT interval with subsequent appearance of hypertrophic cardiomyopathy at one week of age. Maternal glucose metabolism was normal. By 15 months of age the hypertrophy had largely resolved but the long QT persisted. The possible relationship between these conditions is discussed.

Trends in the prevalence of congenital heart disease: comprehensive observations over a 24-year period in a defined region of Canada.

OBJECTIVE: To determine the prevalence of congenital heart disease (CHD) in the three Maritime provinces, and to study prevalence differences among provinces and defined regions within these provinces. DESIGN: Each province was divided by counties into regions. All cases of CHD who were born alive in the study area between 1966 and 1989 were entered in a registry. Prevalences were analyzed for each province and for selected regions per year, per 1000 live births, and by diagnosis made by one year of age and by the 16th birthday. Comparison was then made with prevalences of a group who had severe lesions. INTERVENTIONS: Excepting a small number of CHD cases who were diagnosed by autopsy only, diagnosis was made by pediatric cardiologists using appropriate procedures, including cardiac ultrasound and cardiac catheterization. SETTING: The only tertiary care centre for children's heart disease in the provinces of Nova Scotia, New Brunswick and Prince Edward Island, areas of relative geographic isolation (combined population of 1.75 million people). MAIN RESULTS: A statistically significant positive linear trend occurred in these provinces during the study. The recorded prevalence of CHD in New Brunswick was significantly lower. Pooled prevalences by the first and 16th birthdays (8.0 and 12.5 per 1000 live births, respectively) of two regions of highest prevalence for 1980-86 were significantly higher (P < 0.05) than the pooled prevalence rate of all the remaining regions. Prevalence rates of a group with severe lesions were stable for 1976-86 in all regions. CONCLUSIONS: Differences in prevalence of CHD among provinces and regions were related to ascertainment levels. Prevalence of CHD with diagnosis by the first and 16th birthdays were approximately 8.0 and 12.5 per 1000 live births, respectively. The prevalence rate of a severe lesion group was a stable measure.

Telemedicine activity at a Canadian university medical school and its teaching hospitals.

Dalhousie University Medical School and its teaching hospitals have been providing clinical telemedicine services since 1987. The object of the present study was to assess the extent and growth of telemedicine at the medical school and teaching hospitals, as well as to evaluate the obstacles to its deployment. This was achieved by conducting structured personal interviews with telemedicine providers. Twenty telemedicine programmes were identified, of which 15 were operational and five were being planned. The number of established telemedicine projects had doubled in the six months preceding the study. A wide variety of telemedicine services were provided, ranging from clinical consultations in a number of medical specialties to patient education, grand rounds and continuing medical education. These services were provided to sites in a wide area in the Maritime region and internationally. The three most important obstacles to the implementation of telemedicine were a lack of knowledge about telemedicine (80% of respondents), time constraints (75%) and funding (70%).

Paediatric echocardiography by telemedicine--nine years' experience.

In 1987 we established a realtime echocardiography service by telemedicine from the paediatric cardiology department of a tertiary-care hospital in Halifax. The service was initially provided to single regional hospital but was expanded to six regional hospitals in the three Canadian Maritime Provinces. The system used a dial-up broadband video-transmission service provided by the telephone companies. Records of all transmissions were kept prospectively and reviewed to January 1997. A total of 324 transmissions were made. During 1995-96 there were 135 studies: 69 (51%) were urgent examinations of newborn children and 30 (22%) were urgent examinations of older children; repeat studies and postoperative checks (usually for pericardial effusion) accounted for the other 36 studies (27%). The images were of broadcast quality except in five cases where problems with transmission or poor sedation occurred. A comparison of 26 transmitted studies with repeat, 'in person' studies showed no important discrepancies in diagnosis. During the two-year study period, the cost of the network (equipment leasing costs and telecommunications costs) was C$90,000. Use of the telemedicine network saved unnecessary patient transfer in 31 cases. The cost of the transportation avoided was C$100,000-C$118,000. This review confirms our preliminary findings that broadband echocardiography transmission provides a service comparable in availability and accuracy to that provided in our paediatric cardiology division.

Gemella species endocarditis in a child.

Organisms of the genus Gemella can, on occasion, cause serious systemic illness. The present paper reports a successfully treated case of endocarditis in a 12-year-old girl with congenital heart disease caused by species of Gemella. The child presented with cough, fatigue and decreased appetite without fever. Echocardiogram demonstrated marked mitral insufficiency with flail posterior mitral valve leaflet, mitral valve vegetations, and an enlarged left atrium and ventricle. While being treated with vancomycin, the child initially had persistent bacteremia, which resolved after the addition of gentamycin; the course of therapy was completed with penicillin G and gentamycin once antimicrobial susceptibilities were available. Attempts to identify the species of Gemella were unsuccessful in the local laboratory, and at reference laboratories in Canada and the United States. The isolate is undergoing further evaluation to determine its taxonomic status.

Detection of pulsed gamma rays above 100 GeV from the Crab pulsar.

We report the detection of pulsed gamma rays from the Crab pulsar at energies above 100 giga-electron volts (GeV) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) array of atmospheric Cherenkov telescopes. The detection cannot be explained on the basis of current pulsar models. The photon spectrum of pulsed emission between 100 mega-electron volts and 400 GeV is described by a broken power law that is statistically preferred over a power law with an exponential cutoff. It is unlikely that the observation can be explained by invoking curvature radiation as the origin of the observed gamma rays above 100 GeV. Our findings require that these gamma rays be produced more than 10 stellar radii from the neutron star.

Radio imaging of the very-high-energy gamma-ray emission region in the central engine of a radio galaxy.

The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10(12) electron volts and are bright sources of very-high-energy (VHE) gamma-ray emission, it is not yet known where the VHE emission originates. Here we report on radio and VHE observations of the radio galaxy Messier 87, revealing a period of extremely strong VHE gamma-ray flares accompanied by a strong increase of the radio flux from its nucleus. These results imply that charged particles are accelerated to very high energies in the immediate vicinity of the black hole.