Seismic-wave attenuation associated with crustal faults in the new madrid seismic zone.

The attenuation of upper crustal seismic waves that are refracted with a velocity of about 6 kilometers per second varies greatly among profiles in the area of the New Madrid seismic zone in the central Mississippi Valley. The waves that have the strongest attenuation pass through the seismic trend along the axis of the Reelfoot rift in the area of the Blytheville arch. Defocusing of the waves in a low-velocity zone and/or seismic scattering and absorption could cause the attenuation; these effects are most likely associated with the highly deformed rocks along the arch. Consequently, strong seismic-wave attenuation may be a useful criterion for identifying seismogenic fault zones.

Seismic activity and faulting associated with a large underground nuclear explosion.

The 1.1-megaton nuclear test Benham caused movement on previously mapped faults and was followed by a sequence of small earthquakes. These effects were confined to a zone extending not more than 13 kilometers from ground zero; they are apparently related to the release of natural tectonic strain.

Recurrent intraplate tectonism in the new madrid seismic zone.

For the first time, New Madrid seismicity can be linked to specific structural features that have been reactivated through geologic time. Extensive seismic reflection profiling reveals major faults coincident with the main earthquake trends in the area and with structural deformation apparently caused by repeated episodes of igneous activity.

Distribution and dynamics of Japanese beetles along the Indianapolis Airport perimeter and the influence of land use on trap catch.

As part of a program to minimize the accidental transportation of Japanese beetles (Popillia japonica) through cargo aircraft to areas where they are not established, a 4-yr trapping project was initiated to study the relative distribution and dynamics of the beetles along a trap line around the Indianapolis International Airport. Land use influence on beetle abundance (trap catch) was assessed using a geographic information system. Trap catch was consistently high in some locations and low in others. In general, high trap catches occurred near agronomic land planted with corn or soybeans, which are both preferred hosts of adult beetles. Low trap catches generally occurred in areas lacking preferred host plants. The amount of agronomic land within 500 m of the traps was always positively correlated with trap catch. Average trap catches were highly correlated by location from year to year, indicating stability of the relative distribution of the beetles along the trap line. Because high trap catches consistently occurred in the same locations, it can be inferred that trapping can be an effective method to monitor Japanese beetle populations. Taking airport-owned agronomic land out of corn and soybean production near the cargo terminals may reduce beetle activity in these areas.

Long-term outcome and prognostic determinants in children with hypertrophic cardiomyopathy.

OBJECTIVES: We sought to determine clinical, angiographic, and echocardiographic predictors of survival in children with isolated hypertrophic cardiomyopathy (HCM) in a large pediatric centre. BACKGROUND: Sudden death is a catastrophic outcome of HCM in childhood but has been difficult to predict. Current therapies might provide for improved outcome if factors identifying high risk can be identified. METHODS: Records of 99 patients diagnosed with HCM from 1958 to 1997 at <18 yr were reviewed for clinical, angiographic (n = 62) and echocardiographic (n = 83) predictors of survival outcome. The effects of clinical characteristics on sudden death (including resuscitated sudden death) were individually tested in Cox's proportionate hazard modeling. RESULTS: Seventy-one subjects were male. Median age at diagnosis was 5.0 yr with a medical follow-up interval of 4.8 yr. Thirty-seven of 97 patients had a family history of HCM. Ambulatory electrocardiograms (ECG) in 78 patients demonstrated supraventricular tachycardia in 16 and ventricular tachycardia in 21. Death or resuscitated sudden death occurred in 18 patients. Sudden death rate was 2.7%/yr after age 8 yr. Cox's proportionate survival modeling revealed increased corrected QT interval (QTc) dispersion on ECG (relative risk [RR] 1.61 per 20 ms increment, p < 0.0003), ventricular tachycardia (VT) on ambulatory ECG (RR 3.75, p < 0.006) and myocardial bridging of the LAD coronary (RR 12.0, p < 0.003) to be associated with reduced time to death or resuscitated sudden death. CONCLUSIONS: Detailed assessment of ECGs, ambulatory ECGs, and coronary angiography can assist in identifying which children with HCM are at risk for sudden death.

Arrhythmia and mortality after the Mustard procedure: a 30-year single-center experience.

OBJECTIVES: Our purpose was to assess the risk factors for late mortality, loss of sinus rhythm and atrial flutter after the Mustard operation. BACKGROUND: The Mustard operation provides correction of cyanosis with low surgical risk in transposition of the great vessels. However, right ventricular failure, loss of sinus rhythm, atrial flutter and death are frequent long-term complications. METHODS: Records of 534 children who underwent the Mustard operation at a single center since 1962 were reviewed for demographic, anatomic, electrocardiographic and physiologic predictors and outcomes. RESULTS: There were 52 early deaths (9.7%). Survival analysis was undertaken for 478 early survivors with a mean follow-up interval of 11.6 +/- 7.2 years. There were 77 late deaths (16.1%), with sudden death (n = 31) the most frequent cause. Survival estimates were 89% at 5 years and 76% at 20 years of age. Risk factors were an earlier date of operation, operative period arrhythmia and an associated ventricular septal defect. Risk (hazard) of late death declined in the first decade, with further peaks in the second decade. Sinus rhythm was present in 77% at 5 years and 40% at 20 years. Loss of sinus rhythm was associated with previous septectomy, postoperative bradycardia and late atrial flutter. Freedom from atrial flutter was 92% at 5 years and 73% at 20 years of age. Risk factors for atrial flutter were the occurrence of perioperative bradyarrhythmia, reoperation and loss of sinus rhythm during follow-up. Risk of atrial flutter demonstrates a late increase. CONCLUSIONS: Ongoing loss of sinus rhythm and late peaks in the risk of atrial flutter and death necessitate continued follow-up.

Risk factors for atrial tachyarrhythmias after the Fontan operation.

OBJECTIVES: The purpose of this study was to define the incidence and risk factors for atrial tachyarrhythmias after the Fontan operation. BACKGROUND: Atrial tachyarrhythmias cause morbidity after the Fontan operation. Causative factors may be affected by the type of systemic to pulmonary connection. METHODS: The Fontan operation was performed in 270 consecutive patients between 1982 and 1992. The mean age at operation was 7.0 +/- 4.3 years. Direct atriopulmonary connection was used in 138 patients (51%), total cavopulmonary connection in 94 (35%) and right atrial to right ventricular connection in 38 (14%). RESULTS: Atrial tachyarrhythmias were seen early postoperatively in 55 patients (20%), preoperative atrial tachyarrhythmia being the only risk factor. Follow-up was achieved for 228 early survivors (97%) at a mean interval of 4.4 years. There were 20 late deaths. Late atrial tachyarrhythmias were noted in 29% of patients who received an atriopulmonary connection, 14% of those who received a total cavopulmonary connection and 18% of those who received a right ventricular connection (p < 0.02). Significant risk factors as determined by univariate and multiple logistic regression analysis were atriopulmonary connection type (odds ratio 0.40 for total cavopulmonary relative to atriopulmonary connection [p < 0.05] and 0.37 for right ventricular relative to atriopulmonary connection [p = 0.08]), longer follow-up interval (odds ratio 1.32 for each consecutive year [p < 0.002]) and atrial tachyarrhythmia in the operative period (odds ratio 6.31 [p < 0.0001]). CONCLUSIONS: Early postoperative atrial tachyarrhythmias, length of follow-up and atriopulmonary connection are significant independent risk factors for the presence of late atrial tachyarrhythmias.

A pedigree-based genetic appraisal of Boxer ARVC and the role of the Striatin mutation.

The objective of this paper was to investigate by pedigree-based genetic means the origins and inheritance of arrhythmogenic right ventricular cardiomyopathy (ARVC) in UK Boxers and assess the role of the proposed causal mutation in the gene, Striatin (STRN). All ARVC cases traced back to a small number of imported American dogs deriving from the group of Boxers studied by Harpster (1983) to define the disease, strongly suggesting that the disease is the same in the two countries. Dogs with and without the STRN mutation were found in both ARVC affected and normal Boxers showing that the mutation is not responsible for the disease. Evidence was found that the STRN mutation is, however, genetically linked with the gene responsible on the same chromosome. The linkage implies that the two genes can separate by meiotic recombination such that both ARVC-affected and ARVC-unaffected lines of dogs may carry either the STRN mutation or its wild-type allele. These have been found. Homozygotes for the STRN mutation tended to be severely affected at early ages, suggesting that there is an interaction between the known effects of the STRN mutation on the cardiomyocyte and ARVC.

Body weight, blood pressure, and electrolyte excretion of young adults from six ethnic groups in Hawaii.

There is positive correlation between high dietary intake of sodium and prevalence of hypertensive disease. Dietary potassium shows a negative correlation with this prevalence. Racial background of subjects may affect such relationships. This is a study of the relationships between ethnicity and blood pressure in young adults of six ethnic groups in Hawaii. Body weight, electrolyte excretion, which may reflect intake, and blood pressure of the subjects are reported here. Caucasians and Hawaiians and part-Hawaiian young adults tended to be taller and heavier than the Chinese, Filipinos, Japanese, and Koreans. Both systolic and diastolic pressures were significantly higher in males than in females (all races combined). No significant differences between sexes or races were found in urinary excretion of sodium and potassium or in urinary sodium:potassium ratios. Body weight and Quetelet's Index but not sodium:potassium ratio correlated significantly with diastolic pressure.

Dietary fiber and cholesterol metabolism in rabbits and rats.

Rabbits fed semipurified diets have elevated plasma cholesterol levels, and they oxidize [26-14C]cholesterol to expired 14CO2 more slowly than rabbits on a natural ingredient diet. Addition of several different types of fibrous material to a semipurified diet failed to prevent the hypercholesterolemic response. Rats on semipurified diets also oxidized [26-14C]cholesterol more slowly and tended to have somewhat higher plasma cholesterol levels than rats on commercial feed. Cholesterol oxidation was not stimulated by addition of fibrous materials to the semipurified diet, but rats fed a semipurified diet containing raw potato starch oxidized cholesterol at a rate comparable to that of rats on commercial diet. Raw potato starch was poorly digested by the rats. Cooked potato starch was well digested and failed to stimulate the rate of oxidation of cholesterol. A semipurified diet containing raw potato starch did not produce a hypercholesterolemic response in rabbits, even though the raw starch was well digested.

Plasma cholesterol levels in rabbits fed low fat, low cholesterol diets: effects of dietary proteins, carbohydrates and fibre from different sources.

Rabbits become hypercholesterolemic when transferred from commercial feed to a low fat, cholesterol-free semisynthetic diet. The role of different dietary components in mediating this effect was investigated by varying the composition of the semisynthetic diet and of the commerical feed. Addition of alfalfa to the semisynthetic diet prevented the normal hypercholesterolemic response, but other plant products, including several with high fibre content, were ineffective. Increasing the content of powdered cellulose appeared to enhance the response. A commercially formulated diet in which the alfalfa and soybean meal components were replaced by ground corn and oats did not produce a significant elevation of plasma cholesterol. Substitution of different sugars or starches for the dextrose in the semisynthetic diet gave variable results, but of those tested, only potato starch prevented the hypercholesterolemia. The type of protein used in the semisynthetic diet had a marked influence on the level of plasma cholesterol. Semisynthetic diets containing proteins from animal sources gave higher plasma cholesterol levels than those containing proteins from plant sources. Very low levels were obtained with a low choline semisynthetic diet containing soy protein isolate, and supplementation with choline and methionine only raised the level to that normally obtained with commercial feed. Replacement of the salt mixture in the semisynthetic diet by one specially recommended for rabbits made no significant difference to the hypercholesterolemic response. Prevention of coprophagy did not significantly affect plasma cholesterol levels in rabbits on either commerical or semisynthetic diets. Growth performance was generally better on commercial feed than on semisynthetic diets but there was no direct correlation between weight gain and level of plasma cholesterol in rabbits on the different semisynthetic diets.

Long-term outcome of mothers of children with complete congenital heart block.

OBJECTIVES: To determine the health of mothers of offspring with complete congenital heart block (CHB) both at the time of delivery of the affected child and in the long-term, and the percentage of mothers and children with CHB who had anti-SSA/Ro and/or SSB/La antibodies. PATIENTS AND METHODS: Sixty-four mothers of 64 children with CHB (seen between 1964 and 1993) were identified through the Cardiology database of The Hospital for Sick Children, Toronto, Canada. Medical information from these of children with CHB was evaluated. Data were obtained from the mothers by mailed questionnaire, telephone interview, and/or from the attending physicians. The presence of anti-Ro antibodies and anti-La antibodies were evaluated by ELISA assay. RESULTS: The mean age at the time of delivery of the first child with CHB was 28 +/- 6 years. At the time of delivery 42 (66%) mothers were healthy, 2 (3%) had systemic lupus erythematosus (SLE), 2 (3%) had linear scleroderma, 2 (3%) had rheumatoid arthritis; 3 (5%) had a history of rheumatic fever (but were otherwise well), 1 (2%) had Sjogren's syndrome (SS), and 12 (19%) had an undifferentiated autoimmune syndrome (UAS) (arthralgia, myalgia, photosensitivity, skin vasculitis, Raynaud's phenomenon). The mean time to follow-up from deliver to study was 121 +/- 88 months. The mean maternal age at study was 38 +/- 9 years. Three of 12 mothers who initially had a UAS progressed to SLE (average follow-up time of 80 months, median 96), and 2 developed SS (with average follow-up time 140 months, median 132) and 1 went into remission. The mean follow-up time for the other mothers who did not develop an autoimmune disease was 150 +/- 102 months. Thirty-six of the 42 initially healthy mothers remained well. One mother developed SLE; 1 developed hyperthyroidism; 1 developed anky-losing spondylitis; and 3 developed an UAS. The mean follow-up time of the 36 mothers who remained healthy was similar (123 +/- 97 months) to the 6 initial healthy mothers who developed an autoimmune disease (121 +/- 36 months). Anti-Ro and/or anti-La antibodies were positive in 32 of 53 (60%) mothers tested. Fourteen of the 53 mothers were symptomatic at the time of delivery and 39 were asymptomatic. Anti-Ro and/or anti-La antibodies were positive in 12 of 13 mothers tested at the time of delivery. CONCLUSIONS: The long-term maternal outcome in our cohort was very good as most of the initially healthy mothers remained well at follow-up. Twenty-five percent of the mothers with a UAS and only 2% of the initially healthy mothers developed SLE. The development of an autoimmune disease in an asymptomatic mother identified by the birth of a child with CHB was less common in our study than in previous studies. However, close follow-up of mothers with UAS is warranted.

Five-year experience with implantable defibrillators in children.

Cardioverter-defibrillators were implanted in children aged 4 to 16 years over a 5-year period with no mortality and eventual clinically appropriate shocks in 6 of 11 patients. Both transvenous and epicardial implantable cardioverter-defibrillators were safe and effective in children resuscitated from sudden death or at high risk for sudden death.

Chronotropic competence of the sinus node in congenital complete heart block.

Electrocardiograms taken at rest of 2 children with transplacental exposure to anti-Ro antibody but 1:1 atrioventricular conduction demonstrated sinus node disease. Treadmill exercise testing of 28 patients with congenital complete heart block found 3 patients with chronotropic incompetence of the sinus node.

Clinical efficacy and safety of intravenous Amiodarone in infants and children.

The effectiveness and safety of intravenous amiodarone in children are not well established. This study reviewed its use in 30 infants and children for life-threatening tachyarrhythmias: 18 patients (19 episodes) with supraventricular tachycardia, and 12 with ventricular tachycardia. Eighteen patients had structural heart defects with arrhythmias that occurred after surgery. The mean loading dose was 5 mg/kg infused over 1 hour, with a starting maintenance dose of 5 micrograms/kg/min. In 18 treatment episodes, amiodarone was used alone or in combination with digoxin. Thirteen patients received amiodarone combined with other antiarrhythmic agents. Intravenous amiodarone was effective or partially effective in 94% of patients, achieving a therapeutic effect in a median time of 1 day (range 1 hour to 5 days). The mean effective maintenance dose was 9.5 micrograms/kg/min (13.7 mg/kg/day), and median treatment duration was 5 days (range 1 to 30). Adverse effects occurred in 18 patients (58%), however none necessitated termination of amiodarone therapy. Potentially significant electrocardiographic abnormalities occurred in 5 patients during combination antiarrhythmic therapy with propafenone. Sinus bradycardia requiring temporary postoperative pacing occurred in 3 patients treated with amiodarone alone. Intravenous amiodarone used alone or in combination therapy is an effective treatment for resistant, life-threatening arrhythmias in infants and children. Combination drug therapy with propafenone must be used cautiously. Potential bradycardia pacing may be necessary during administration of amiodarone after surgery.

Accuracy of surface electrocardiograms for differentiating children with hypertrophic cardiomyopathy from normal children.

Most patients with hypertrophic cardiomyopathy have abnormal electrocardiograms. In this study of 37 matched pairs in the pediatric age group, the 12-lead electrocardiogram did not differentiate between affected and normal children reliably enough to allow it to be used as a screening test in the general population.

Spontaneous aortic thrombosis in a neonate presenting as coarctation.

Spontaneous aortic thrombosis in the neonate is a rare entity of uncertain etiology with a high mortality. To our knowledge, this is the first report of a newborn surviving surgical treatment of spontaneous thrombosis of the thoracic aorta.

Ion binding by X-537A. Equilibrium and rate of complexation of Co(2+) in methanol.

The reaction of X-537A (XH) with Co(2+) in methanol to form the complex CoX(+) has been studied fluorometrically to determine the equilibrium constant as a function of temperature. The effect of complexation on the proton NMR spectrum of the X-537A was studied to determine the kinetics of complex formation. Comparing the data for the reaction XM(+) leads to X(-) + M(2+) in methanol at 25 degrees for several M(2+) we find that the equilibrium constants increase in the order CoX(+) less than MnX(+) and span only a factor of 5 while the rate constants increase in the order NiX(+) less than CoX(+) less than MnX(+) and span a factor of more than 100.

Torsade de pointes, acquired complete heart block and inappropriately long QT in childhood.

After spontaneously acquiring complete heart block, two children presented with torsade de pointes as a result of inappropriate prolongation of the QT interval. Although both remain well following pacemaker insertion, their cases illustrate the importance of QT interval assessment in patients with atrioventricular block, and demonstrate that syncopal episodes, and possibly sudden death, in children with acquired heart block can be due to bradycardia-induced ventricular tachyarrhythmias, rather than extreme bradycardia per se.