Constrictive effect of thyroxine on the ductus arteriosus in fetal rats

This work was conducted to know whether thyroxine (T4) when injected into fetal rats would induce a constriction of the ductus arteriosus (DA). In Experiment 1, fetal rats on day 20 of gestation were given a subcutaneous injection of 1 or 10 micrograms T4 through the maternal uterine wall, and were autopsied 3 or 6 hr later. Similarly, in Experiment 2, the mother rats were given an injection of hydrocortisone (10 mg/kg) just after fetal T4 injections. In either series of experiments, uninjected littermates served as controls. According to the whole-body freezing and shaving method, the DA was exposed and calibrated under a dissecting microscope. In Experiment 1, the DAs of the T4-injected fetuses, 3 hr later, were significantly smaller in caliber than those of their controls, but recovered 6 hr later. In Experiment 2 with fetal T4 injection followed by maternal hydrocortisone injection, the DAs of the T4-injected fetuses were further smaller in caliber than those of their controls which were clearly shrunken as compared with those of controls in Experiment 1. These results indicate that T4 exerts a constrictive effect on the DA, an effect which is strengthened in the presence of hydrocortisone.     

The response of the isolated ductus arteriosus to transmural stimulation and drugs

1 Responses of isolated ductus arteriosus preparations from near term guinea-pigs and lambs to transmural electrical stimulation and drugs were studied in a low oxygen medium (Po(2) 19 to 28 mmHg).2 Acetylcholine and noradrenaline contracted both vessels in a dose-dependent manner, their threshold being between 10(-8) and 10(-7) M. Transmural stimulation (pulse width 0.2 to 0.6 ms, typically 20 Hz) also contracted the vessels.3 Atropine and phentolamine or dibenzyline selectively blocked responses to acetylcholine and noradrenaline, respectively.4 In the guinea-pig ductus, part of the response to transmural stimulation was due to activation of intrinsic adrenergic nerves since the responses were reduced by alpha-adrenoceptor antagonists, bretylium or prior reserpine treatment, but not by atropine. The response of the lamp ductus to transmural stimulation varied greatly in magnitude and was inconsistently affected by alpha-adrenoceptor blocking drugs.5 There was no evidence that transmural stimulation activated cholinergic nerves in either species.6 After inactivation of alpha-adrenoceptors with dibenzyline, noradrenaline caused a beta-adrenoceptor-mediated relaxation. Both this effect and isoprenaline-mediated relaxation were blocked by propranolol. beta-Adrenoceptor activity was more prominent in the ductus of the guinea-pig than of the lamb.7 Raising the Po(2) from 19-28 to 92-98 mmHg increased the response of the guinea-pig ductus to transmural stimulation suggesting that, in this species, physiological elevation of oxygen tension at birth may increase transmitter release from intrinsic adrenergic nerves. Whether this mechanism would contribute to ductus closure remains an open question.8 We postulate that beta-adrenoceptor-mediated relaxation has a role in maintaining ductus patency in the guinea-pig foetus.     

Echocardiographic diagnosis of thrombus originating from the ductus arteriosus

OBJECTIVES: This study examined the impact of French routine programs urging the combined measles-mumps-rubella immunization of 15-month-old children. METHODS: We applied a cohort analysis to surveillance data collected by general practitioners to estimate the cumulative incidence rate per 1000 unvaccinated children and the proportion of susceptible children, by age and for each birth cohort between 1985 and 1995. RESULTS: More than 70% of unvaccinated children born in 1985 and 1986 had measles by the age of 10. This incidence rate dramatically decreased after implementation of the routine measles-mumps-rubella immunization program in 1989, but the proportion of 5-year-olds susceptible to measles has not decreased appreciably. In 1996, more than 15% of the children born between 1990 and 1995 were susceptible. CONCLUSIONS: The measles vaccine coverage achieved by the French routine immunization program remains insufficient as regards reducing the number of susceptible children.     

Accelerated maturation of fetal ductus arteriosus by maternally administered vitamin A in rats

STUDY OBJECTIVE: Examination of alcohol consumption patterns of male spectators at two major-league baseball stadiums. METHODS: A prospective observational study was conducted at two stadiums over the course of three games at each venue. We approached 1,084 male spectators of drinking age in a consecutive fashion at two junctures: at the entrance gate and during the fifth inning inside the stadium's concourse. Of those approached, 747 (68.9%) participated. After verbal consent, participants completed a questionnaire and blew into a breath analyzer. The results were blinded and later analyzed. RESULTS: Forty-one percent of all participants tested positive for alcohol. The highest consumption occurred in the 20- to 35-year-old age group. In this age group, 50.8% had consumed some alcohol, and 10.8% had a blood alcohol level of .08% (intoxicated) or higher. Almost 5% of all participants tested during the fifth inning collection were intoxicated and claimed to be driving. CONCLUSION: Of the spectators tested, those in the 20- to 35-year-old age group were most likely to have consumed alcohol and to be legally intoxicated. A disturbing number of spectators who had blood alcohol levels of .08% or higher late in the game claimed to be driving home.     

The effect of indomethacin tocolysis on fetal ductus arteriosus constriction with advancing gestational age

OBJECTIVE: Our purpose was to determine whether continuing exposure to indomethacin tocolysis is associated with an increased incidence of constriction of the human fetal ductus arteriosus with advancing gestational age. STUDY DESIGN: Fetal echocardiograms were reviewed in 61 cases in which the pregnant women were treated for preterm labor with indomethacin (25 mg orally every 6 hours). Density function analysis and regression analysis were used to assess the effect of indomethacin tocolysis on ductal constriction with advancing gestational age. RESULTS: A total of 193 fetal echocardiograms were obtained for 72 fetuses. Ductal constriction developed in 50% of the fetuses ranging from 24.7 to 35.0 weeks' gestation. Fetuses with indomethacin-induced ductal constriction demonstrated a greater increase in systolic flow velocities with advancing gestational age compared with the nonconstricted group (p < 0.05). Constriction was detected at a mean gestational age of 30.9 +/- 2.3 weeks at an average of 5.1 +/- 6.0 days after initiation of therapy. Ductal constriction occurred by 31 weeks' gestation in 70% of the affected fetuses. After discontinuation of indomethacin therapy, all follow-up echocardiograms demonstrated a return to nonconstricted ductal flow velocities. No significant adverse neonatal outcomes were attributed to indomethacin use. CONCLUSIONS: A dramatic yet reversible increase in the incidence of indomethacin-induced ductal constriction occurs at 31 weeks' gestation. However, ductal constriction can occur at any gestational age. With indomethacin tocolysis, weekly fetal echocardiography is warranted for the duration of therapy.     

Mechanisms of action of isoflurane on contraction of rabbit conduit artery

Isoflurane may cause differential effects on different vascular beds of the same animal species. The mechanisms of this action have not been elucidated. Accordingly, we compared in rabbit aorta and femoral artery the effects of isoflurane (1-3.3%) in isolated rings (endothelium denuded) activated by norepinephrine, and isoflurane effects on Ca2+ fluxes from the sarcoplasmic reticulum in skinned strips. When < 30 nM norepinephrine was used to cause ring contraction, isoflurane increased the force of contraction in aortic rings, but decreased force in femoral arterial rings. At 30 nM norepinephrine stimulation, 3.3% isoflurane decreased the force and, in the presence of verapamil, isoflurane actually increased the force in both arterial types. In skinned strips of both arterial types, isoflurane present during Ca2+ uptake decreased the caffeine-induced tension transients, whereas isoflurane present during Ca2+ release enhanced the transients. Isoflurane potentiated the depression of the tension transients by ryanodine. Isoflurane directly caused contracture even in the absence of caffeine. Thus, isoflurane has similar cellular mechanisms of action in the aortic and femoral arterial smooth muscle: inhibiting Ca2+ influx through the sarcolemma, decreasing Ca2+ uptake by the sarcoplasmic reticulum, and enhancing caffeine-induced Ca2+ release from the sarcoplasmic reticulum.     

Aneurysm of the nonpatent ductus arteriosus in the newborn

Aneurysm of the nonpatent ductus arteriosus in the newborn is a rare, but potentially fatal condition. Of reported ductal aneurysm up to 1969, diagnosis was made at autopsy only. We report here to our knowledge for the first time on a two week old infant with correct preoperative angiographic diagnosis followed by a successful surgical cure.     

Effectiveness of five-loop coils to occlude patent ductus arteriosus

Coil occlusion of patent ductus arteriosus with 5-loop coils was undertaken in 10 patients without coil embolizations, and with 90% immediate occlusion and 100% occlusion at follow-up. We conclude that 5-loop coil occlusion of patent ductus arteriosus is safe and effective.     

Closure of the patent ductus arteriosus by means of cardiac catheterization

Authors report their results with transcatheter closure of patent arterial duct during a period of 1 year. Thirty patients underwent the procedure at the mean age of 5.22 yrs (range 5 mos-22.3 yrs) and mean bodyweight of 19.1 kg (range 5.8-73 kg). There were 9 males and 21 females. The diagnosis of the patent arterial duct was established by physical examination and noninvasive techniques. The procedures were attempted in all patients above 5 kg bodyweight with patent arterial duct and normal pulmonary artery pressure, irrespective of the shunt-size. All procedures were performed under general anesthesia in one session with the diagnostic cardiac catheterisation. Transcatheter closure was successful in 29 patients. In one patient the device embolized into the left pulmonary artery, snaring was unsuccessful, surgical closure of the patent duct and removal of the device took place uneventfully. Control aortography 15 minutes after the coil placement showed insignificant residual shunt through the patent duct in 8 patients (27%), while echocardiography at 1 month proved complete closure in all. The patients were followed by noninvasive methods. No mortality was observed. Authors emphasize the low risk and cost-effectiveness of the procedure. They stress the importance of the patients selection. Authors applied the technique for the first time and introduced it to the regular patient-care practice in Hungary.     

Transcatheter closure of patent ductus arteriosus using controlled-release coils

Controlled-release coils have become available recently for the closure of patent ductus arteriosus (PDA). Transcatheter closure of patent arterial ducts was attempted in 13 patients, ranging in age from 5 months to 15 years, mean 4.1 years. Implantation of controlled-release PDA coils was attempted via the femoral artery through 5 Fr catheters in all cases except one, in whom both the femoral arterial and venous routes were used. The procedure was successful in 10 of the 13 patients. In these, the pulmonary artery systolic pressure ranged between 25 and 42 mmHg and the duct diameter varied from 1.5 to 6 mm at its narrowest point. Six of the patients received a single coil. Two coils were inserted in three patients and three coils in one patient. In three patients the ducts were too large for safe release of the coils, despite attempted implantation of up to three coils simultaneously. These coils were easily withdrawn into the catheter. Immediately at the end of the procedure, the duct was completely occluded in nine of the 10 patients, and in one patient there was a small residual flow. The procedure time varied between 35 min and 2.5 h, mean 81 min and the fluoroscopy time varied from 5 to 78 min, mean 25 min. None of the patients experienced hemorrhage, diminished lower extremity pulse, hemolysis or infection. In one patient, a 5 mm coil embolized into the right pulmonary artery soon after release. It was retrieved with a snare, then 8 mm and a 5 mm coil were implanted satisfactorily in the arterial duct. At follow-up by color Doppler echocardiography, the duct was completely occluded in all patients. Transcatheter closure of patent arterial ducts by controlled-release PDA coils is effective and safe. Even when more than one coil is inserted, it is still cheaper than transcatheter umbrella closure. This method is therefore of great value, particularly in less affluent countries.     

Interaction of heart rate and hypothermia on global myocardial contraction of the isolated rabbit heart

We studied the effects of mild hypothermia on cardiac contractility in isolated rabbit hearts perfused with Krebs-Henseleit solution according to the technique of Langendorff. Isovolumetric left ventricular pressure (LVP) was measured with a fluid-filled balloon. Hearts were paced after induction of atrioventricular block. At low heart rates ( < 30 bpm) mild hypothermia (cooling to 30 degrees C) induced a 32% increase in LVp (146.5 +/- 10 mm Hg at 30 degrees C vs 110.7 +/- 13 mm Hg at 37 degrees C) but this positive inotropic response was progressively lost by increasing heart rate. At pacing rates > or = 90 bpm, lower systolic LVP, higher diastolic LVP, and lower positive and negative LV dP/dt were obtained in hypothermic (93 +/- 12 mm Hg, 55 +/- 18 mm Hg, 584 +/- 137 mm Hg/s, and 323 +/- 57 mm Hg/s at 210 bpm, respectively) compared to normothermic hearts (123 +/- 4 mm Hg, 10 +/- 4 mm Hg, 1705 +/- 145.5 mm Hg/s, and 1155 +/- 78 mm Hg/s at 210 bpm, respectively.) The duration of mechanical diastole was reduced or suppressed in these hearts. Exposure to the beta-adrenoreceptor agonist, isoproterenol, improved this diastolic dysfunction during hypothermia and pacing at high rates, suggesting that the sarcoplasmic reticulum Ca2+ uptake might be involved. Our data are also consistent with an increase in myofilament Ca2+ sensitivity that is opposed by isoproterenol during hypothermia.     

Transvenous "snare-assisted" coil occlusion of patent ductus arteriosus

We have used the "S" Quattro Turbo to treat four neglected dorsal interphalangeal joint dislocations. At an average follow up period of 45 months, there was a mean increase in the range of movement of the PIP joints by 74 degrees and of the IP joint of the thumb or DIP joints by 45 degrees. We recommend this technique for treating dorsal dislocations of the interphalangeal joints of more than 3 weeks duration.