The role of nitric oxide in digoxin-induced arrhythmias in guinea-pigs

We have investigated the effects of nitric oxide synthase inhibitor (L-NAME), nitric oxide precursor (L-arginine) and nitric oxide donor (sodium nitroprusside) on digoxin-induced arrhythmias both in guinea-pig isolated hearts and in anaesthetised animals. Sodium nitroprusside (0.1 mumol kg-1 min.-1 for 70 min.) caused a marked inhibition in mortality and arrhythmia score but L-NAME (10 mg kg-1) and L-arginine (30 mg kg-1 intravenous bolus followed by 10 mg kg-1 min.-1 for 60 min.) treatments were ineffective in anaesthetised guinea-pigs. None of the drugs markedly affected the time of onset of first arrhythmias or ventricular fibrillation incidence. In isolated heart experiments, nitric oxide generated by either L-arginine (1 mM) or sodium nitroprusside (1 mM) significantly reduced the arrhythmia score whereas L-NAME (1 mM) had no effect. Ventricular fibrillation incidence was totally abolished by sodium nitroprusside and none of the hearts treated with L-arginine had an irreversible ventricular fibrillation. L-NAME decreased ventricular tachycardia duration but increased ventricular fibrillation duration. There were no marked changes in the time of onset of first arrhythmias with these drugs in in vitro experiments. These results suggest that nitric oxide may play a modulatory role in the digoxin-induced arrhythmias in guinea-pigs.

The role of tyrosine kinase in hypoxic constriction of sheep pulmonary artery rings

Complex and incompletely understood mechanisms underline the vascular responses to hypoxia. Recent studies showed that the tyrosine kinase pathway is involved in vasoconstriction of vascular smooth muscle. Therefore, the aim of this study was to determine the tyrosine kinase pathway for the hypoxic contraction in large-diameter sheep pulmonary artery rings in vitro by studying the effects of selective inhibitors of tyrosine kinase and of a protein tyrosine kinase inhibitor. Lowering the pO2 from 96 to 5 mm Hg caused a contraction in arteries precontracted with 5-hydroxytryptamine (5-HT) but not under resting force. Preincubation of arteries with the tyrosine kinase inhibitors, genistein and tyrphostin, abolished the hypoxic contraction without affecting 5-HT contractions. Inhibition of tyrosine phosphatase activity by sodium orthovanadate increased the hypoxic vasoconstriction in 5-HT-precontracted arteries. These results suggest that the tyrosine kinase pathway is involved in hypoxic pulmonary vasoconstriction in sheep isolated pulmonary artery rings.

In vivo Ty1 reverse transcription can generate replication intermediates with untidy ends

Ty1 retrotransposition, like retroviral replication, is a complex series of events requiring reverse transcription of an RNA intermediate, RNA-primed minus- and plus-strand DNA synthesis, multiple strand transfers, and precise cleavages of the template and primers by RNase H. In this report, we examine the structure of in vivo Ty1 replication intermediates, specifically with regard to the behavior of reverse transcriptase upon reaching template ends and to the precision with which RNase H might generate these ends. While the expected 3' termini were always identified, terminal nontemplated bases were also observed at all of the RNA and DNA template ends examined. Nontemplated A residues were most common at all 3' ends, although C residues were preferentially added to minus-strand termini paused at the 5' end of capped Ty1 RNA. In addition, we observed that RNase H removal of the tRNA primer and of the polypurine tract was not always precise or efficient. Finally, we noted numerous instances of Ty1 reverse transcriptase transferring from normal Ty1 template ends to various tRNA templates, with continued synthesis to specific modified bases. A similar pattern was obtained for Ty2, indicating that template ends offer unique opportunities for these two related reverse transcriptases to generate errors.

Residual and recurrent shunts after implantation of Cook detachable duct occlusion coils

OBJECTIVE

To assess the presence and outcome of Doppler detectable shunts following implantation of the Cook detachable PDA coil.

DESIGN

Prospective study.

SETTING

Tertiary paediatric cardiac centre.

PATIENTS

76 consecutive patients undergoing coil implantation (80 procedures).

MAIN OUTCOME MEASURES

Detection and colour Doppler echocardiographic appearance of residual or recurrent shunts, the timing of the appearance of recurrent shunts, and the time taken for spontaneous resolution of these shunts.

RESULTS

Immediate occlusion was achieved in 52 patients. At one month 63 patients had complete occlusion and after three months the duct was completely occluded in 67 patients. In 27 cases small residual shunts were detected on echocardiography 10 minutes after the completion of the implantation procedure; 15 of these had resolved by 24 hours and 20 had resolved by three months. Recurrent shunts were detected after apparent initial complete occlusion in 11 cases 24 hours after coil implantation and in two cases one month after the procedure. Six recurrent shunts resolved on later follow up. Residual shunts appeared as single jets after implantation of a single coil, but up to three separate jets were detected after implantation of multiple coils.

CONCLUSIONS

Spontaneous resolution of small residual shunts occurs in most patients. The recurrence of small shunts after apparent complete occlusion suggests that recanalisation of the duct may occur in a small percentage of patients up to one month after occlusion. Residual shunts may take the form of multiple residual jets that may require implantation of further coils to achieve complete duct occlusion.

Predictors of adverse outcome in cancer patients with candidemia

BACKGROUND

Many factors, including severity of illness, neutropenia, intravenous catheter management, and drug therapy may affect the outcome of candidemia in cancer patients.

METHODS

The records of all patients at M. D. Anderson Cancer Center who developed one or more positive blood cultures for Candida spp between January 1, 1988, and December 31, 1992, were retrospectively reviewed. Four hundred ninety-one episodes of candidemia were identified, for which 476 had complete medical records, which were reviewed in detail.

RESULTS

By 3-month follow-up, 52% of the patients had died. Neutropenia, higher APACHE III score, and visceral dissemination were associated with poor prognosis. Cure rates, adjusted for severity of illness, were similar for fluconazole and amphotericin B treatment. Exchange of central venous catheters was associated with a modest improvement in prognosis.

CONCLUSION

Several factors that influence the outcome of candidemia in cancer patients have been identified. These factors may be relevant for the clinical management of cancer patients with candidemia, and for the design of therapeutic trials.

Replication errors during in vivo Ty1 transposition are linked to heterogeneous RNase H cleavage sites

We previously identified a mutational hotspot upstream of the Ty1 U5-primer binding site (PBS) border and proposed a novel mechanism to account for this phenomenon during Ty1 replication. In this report, we verify key points of our model and show that in vivo RNase H cleavage of Ty1 RNA during minus-strand strong-stop synthesis creates heterogeneous 5' RNA ends. The preferred cleavage sites closest to the PBS are 6 and 3 bases upstream of the U5-PBS border. Minus-strand cDNA synthesis terminates at multiple sites determined by RNase H cleavage, and DNA intermediates frequently contain 3'-terminal sequence changes at or near their template ends. These data indicate that nontemplated terminal base addition during reverse transcription is a real in vivo phenomenon and suggest that this mechanism is a major source of sequence variability among retrotransposed genetic elements.

The epidemiology of hematogenous candidiasis caused by different Candida species

The medical records of patients with hematogenous candidiasis at M. D. Anderson Cancer Center (Houston) between 1988 and 1992 were retrospectively reviewed. There were 491 episodes of infection (6 per 1,000 admissions), 79% of which occurred outside the intensive care unit setting. A significant decrease in incidence was observed among patients with leukemia over the study period, together with a relative decrease in Candida albicans and Candida tropicalis infections and an increase in Candida krusei and possibly Candida glabrata infections. In the multivariate analysis, fluconazole prophylaxis provided strong protection against the development of C. tropicalis infection (odds ratio [OR] = 0.08) and C. albicans infection (OR = 0.15), in comparison with protection against infections due to other species, but it was the single most important determinant for the relative increase in C. krusei (OR = 27.07) and C. glabrata (OR = 5.08) infections. In conclusion, there has been a substantial shift in the epidemiology of hematogenous candidiasis caused by different Candida species in recent years. Fluconazole appears to be playing a major role in this observed shift.

In vitro activity of a new echinocandin, LY303366, compared with those of amphotericin B and fluconazole against clinical yeast isolates

The in vitro activity of LY303366, a new echinocandin derivative, was evaluated with 191 yeast isolates by a broth microdilution method. The MICs at which 50% of the isolates were inhibited were 0.125 microg/ml for Candida albicans and C. tropicalis, 0.25 microg/ml for C. krusei, C. kefyr, and C. glabrata, and 2.0 microg/ml for C. parapsilosis.

Congenital total lipodystrophy and peripheral pulmonary artery stenosis

Multiple peripheral pulmonary artery stenoses were detected in three patients with congenital generalised lipodystrophy. This association, which has not been described before, may be clinically important in patients with lipodystrophy who present with impaired exercise tolerance or heart murmurs.

Multiple cardiac rhabdomyomas: tuberous sclerosis or not?

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Laser valvotomy with balloon valvoplasty for pulmonary atresia with intact ventricular septum: five years' experience

OBJECTIVE

To assess immediate and medium term results of transcatheter laser valvotomy with balloon valvoplasty in selected infants with pulmonary atresia and intact ventricular septum.

DESIGN

Prospective study.

SETTING

Tertiary cardiac unit.

PATIENTS

All infants with pulmonary atresia and intact septum with no more than minor tricuspid valve hypoplasia referred between November 1990 and June 1995. Laser valvotomy was attempted in nine infants of median age 4-5 days and median weight 3.6 kg.

INTERVENTION

The pulmonary valve was perforated using a 0.018 inch fibreoptic guidewire attached to a NdYag laser and introduced through a catheter positioned beneath the valve. After perforation the valve was dilated with progressively larger balloons.

MAIN OUTCOME MEASURES

Successful laser valvotomy and balloon dilatation, complications, pulse oximetry, right ventricular outflow velocities, and need for surgical treatment.

RESULTS

Valvotomy was successful in all but one case, the failure being due to laser breakdown. After perforation the valve was dilated to 6-8 mm diameter. Prostaglandin E was withdrawn immediately in six of the eight duct dependent infants, and 28 and 49 days later in two. No patient required an aortopulmonary shunt. Two patients had repeat valvoplasty at 20 days and three months of age, respectively; one required infundibular resection and closure of the atrial septum at age four and one is awaiting similar treatment.

CONCLUSIONS

Laser valvotomy with balloon valvoplasty is safe and effective treatment for selected patients with pulmonary atresia and intact ventricular septum and should be considered as first line treatment in place of surgical valvotomy.

Right ventricular outflow stent implantation: an alternative to palliative surgical relief of infundibular pulmonary stenosis

OBJECTIVE

Preliminary assessment of the use of stents for palliative relief of right ventricular infundibular stenosis as an alternative to palliative surgical ventricular outflow enlargement.

DESIGN

Descriptive clinical study.

PATIENTS

Four patients with right ventricular outflow obstruction, aged between 2 and 15 years. One had had previous palliative surgery for pulmonary atresia, one had hypoplastic pulmonary arteries after palliative surgery for tetralogy of Fallot, one had multiple congenital abnormalities, and one had hypertrophic cardiomyopathy.

SETTING

Tertiary paediatric cardiac centre.

METHODS

After initial echocardiographic diagnosis the extent of right ventricular outflow obstruction was assessed by angiography. Balloon expandable stainless steel stents (Johnson & Johnson) were deployed in the right ventricular infundibulum.

MAIN OUTCOME MEASURES

Improvement in right ventricular outflow assessed by ventriculography and change in right ventricular/ left ventricular pressure ratio, change in systemic oxygen saturation, freedom from arrhythmias, and sustained improvement in echocardiographic indices of obstruction.

RESULTS

Mean right to left ventricular pressure ratio fell from 0.95 to 0.35 in the three patients with intact ventricular septum. Oxygen saturation increased from 76% to 91% in the patient with tetralogy. No arrhythmias were detected. Improvement was maintained at mean follow up of 9.7 months in three cases, but one patient required stent enlargement 17 months later because of neoendothelial proliferation within the stent.

CONCLUSION

Stent implantation provides an effective alternative to palliative surgical enlargement of the right ventricular infundibulum. Neoendothelial proliferation causes reduction in lumen in some cases, but this may respond to redilatation.

Prolonged local infusion of streptokinase in pulmonary artery thrombosis with nephrotic syndrome

A child with nephrotic syndrome presenting with right heart failure and severe pulmonary hypertension due to pulmonary artery thrombus was treated with locally administered streptokinase infusion. Streptokinase infusion was continued for 8 days, eventually leading to complete dissolution of thrombus.

Treatment of enteric fever with pefloxacin for 7 days versus 5 days: a randomized clinical trial

In this prospective study of enteric fever, 22 patients received 400 mg of pefloxacin twice daily for 5 days (group A) and 24 received 400 mg of pefloxacin twice daily for 7 days (group B). Causative microorganisms were Salmonella typhi (8 in group A, 11 in group B) and Salmonella paratyphi B (14 in group A, 13 in group B). The clinical cure and bacterial eradication rates were 96% (21 of 22) in group A and 100% in group B. In conclusion, 5-day oral administration of pefloxacin was as effective as 7-day treatment of enteric fever caused by Salmonella spp.

Management of invasive candidal infections: results of a prospective, randomized, multicenter study of fluconazole versus amphotericin B and review of the literature

We conducted a prospective, randomized, multicenter study comparing fluconazole and amphotericin B in the treatment of candidal infections. One hundred and sixty-four patients (60 of whom were neutropenic) with documented or presumed invasive candidiasis were assigned to treatment with either fluconazole (400 mg daily) or amphotericin B (25-50 mg daily; 0.67 mg/kg daily for neutropenic patients). Clinical response and survival rates were assessed at 48 hours, after 5 days, and at the end of therapy. Overall response rates to fluconazole and amphotericin B were similar (66% and 64%, respectively). There were no differences in response as related to site of infection, pathogen, time to defervescence, relapse, or survival rates between the groups. Adverse effects were more frequent with amphotericin B (35%) than with fluconazole (5%; P < .0001). The results of this study confirm that fluconazole is as effective as but better tolerated than amphotericin B in the treatment of candidal infections.

Transcatheter occlusion of the arterial duct with Cook detachable coils: early experience

OBJECTIVE

To assess the effectiveness of modified, controlled release Gianturco coils for transcatheter occlusion of the arterial duct.

DESIGN

Prospective study, approved by local medical ethics committee.

SETTING

Tertiary paediatric cardiac centre.

PATIENTS

43 patients with left to right shunting through the arterial duct, two of whom had a residual leak after surgical ligation and three had residual shunting after previous Rashkind umbrella implantation.

INTERVENTION

Transcatheter delivery of one or more coils to the arterial duct.

MAIN OUTCOME MEASURES

Complete occlusion of the arterial duct, based on intention to treat and judged by Doppler echocardiography. Absence of flow disturbance in the branch pulmonary arteries and the descending aorta following the procedure. Assessment of cost of the disposable items used.

RESULTS

At a median follow up period of three months complete duct occlusion was achieved in 37 (86%) of the 43 patients. No flow disturbance in the branch pulmonary arteries or the descending aorta was detected in any patient. The median cost of disposable items used during the procedure was 342 pounds.

CONCLUSIONS

The Cook detachable coil is an effective and financially attractive alternative to the Rashkind umbrella for closure of the arterial duct.

Acute tamponade in a newborn infant caused by a massive cystic teratoma

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Fluconazole versus amphotericin B in the treatment of hematogenous candidiasis: a matched cohort study

PURPOSE

To compare the efficacy and toxicity of fluconazole and amphotericin B in the treatment of hematogenous candidiasis in cancer patients.

PATIENTS AND METHODS

A matched cohort study of cancer patients with hematogenous candidiasis was conducted. Forty-five patients with hematogenous candidiasis who received fluconazole (200 to 600 mg/day) in an open-label trial at the University of Texas M. D. Anderson Cancer Center, Houston, Texas, between February 1990 and June 1992 were matched to 45 patients treated with amphotericin B (0.3 to 1.2 mg/kg/day) for the same diagnosis. Criteria for matching included the following prognostic variables at the initiation of therapy: pneumonia, neutropenia (< 1,000 cells/mm3), number of positive blood cultures before therapy, infecting Candida species, underlying disease, and the simplified acute physiology score. Response and survival at 48 hours, after 5 days of therapy, and at the end of therapy, as well as toxicity rates were obtained. Other post hoc analyses were performed. Differences in outcomes were assessed by the McNemar, the sign, and the log rank tests.

RESULTS

Patients were similar with respect to the matching criteria, age, sex, status of underlying disease, use of antibiotics and growth factors, duration of treatment, presence and removal of central venous catheters, disseminated disease, and concomitant infections. Response rates at 48 hours and 5 days were similar between the two study groups. Overall response rates at the end of therapy were 73% for patients treated with fluconazole and 71% for patients treated with amphotericin B (P = 0.78). There were no differences in survival rates or causes of death. Toxicity was observed in 9% of patients treated with fluconazole and in 67% of patients treated with amphotericin B (P < 0.0001). Toxic effects of amphotericin B included nephrotoxicity, hypokaliemia, and fever and chills.

CONCLUSION

Fluconazole is effective and better tolerated than amphotericin B for the treatment of hematogenous candidiasis in cancer patients.

Problems and controversies in the management of hematogenous candidiasis

Hematogenous candidiasis is associated with substantial mortality and morbidity. Amphotericin B has routinely been used to treat this infection. However, tolerance of therapy with amphotericin B is limited by the drug's toxicity. The results of recently completed prospective randomized clinical studies comparing amphotericin B with fluconazole for the treatment of hematogenous candididiasis suggest that fluconazole is as effective as amphotericin B and that fluconazole is better tolerated by patients. Nevertheless, several questions remain to be answered regarding the optimal choice of antifungal agent for both nonneutropenic and neutropenic patients, the dosing schedule and duration of therapy, the role of combination antifungal therapy, and the efficacy of the lipid formulations of polyenes. Controversial issues with respect to the role of central venous catheters in the pathogenesis of hematogenous candidiasis, as well as the roles of cytokines and white blood cell transfusions in the treatment of neutropenic patients with hematogenous candidiasis, also need to be addressed.

Efficacy of fluconazole in the treatment of upper gastrointestinal candidiasis in neutropenic patients with cancer: factors influencing the outcome

Fluconazole has proved to be effective in treating oropharyngeal and esophageal candidiasis in immunocompromised patients. However, sufficient data are lacking regarding the efficacy of this agent in neutropenic hosts. The aim of the present study was to determine the clinical and mycological efficacy of fluconazole and to define the factor(s) affecting the outcome of fluconazole therapy in severely neutropenic patients (peripheral neutrophil count, < 500/microL) with cancer who have oropharyngeal and/or esophageal candidiasis. One hundred eleven patients with 129 episodes of candidal infections were treated with intravenous and consequently oral fluconazole (200 mg/d and 100 mg/d, respectively). Overall clinical cure and mycological eradication rates were 82% and 56%, respectively. Persistent neutropenia (P < .01), infection with a non-albicans strain of Candida (P = .012), and administration of antifungal therapy during the second or a later neutropenic episode (P < .002) were independently associated with a worse outcome. We conclude that fluconazole is effective in the treatment of upper gastrointestinal candidiasis in neutropenic patients with cancer. Effective treatment of the underlying malignancy, with the resultant recovery from neutropenia, and the determination of the species of infecting Candida isolates are required for the prediction of the outcome of antifungal therapy.

Efficacy of a three-day course of azithromycin in the treatment of community-acquired pneumococcal pneumonia. Preliminary report

Azithromycin is an azalide antibiotic with activity against many of the respiratory pathogens and with marked tissue affinity. In a prospective study, the efficacy of a short-course of azithromycin was evaluated in 25 patients with community-acquired pneumococcal pneumonia. Gram-positive diplococci were abundant in the sputum smears of all patients, and Streptococcus pneumoniae was isolated in the sputum cultures of 15; one patient had pneumococcal bacteremia, as well. Azithromycin was administered at a single dose of 1,000 mg on day 1, and 500 mg on subsequent days for a total of three days in 19 patients, five days in four patients, two and four days in one patient each. Defervescence occurred within 24 hours after the first dose. The overall clinical cure and bacteriologic eradication rates were 96% and 93%, respectively. One patient with pneumococcal bacteremia failed to respond and died in respiratory failure. Side-effects were encountered in three (12%) patients. In conclusion, three-day therapy with a total azithromycin dose of 1,500 mg seems effective and safe in patients with community-acquired pneumococcal pneumonia and no underlying pulmonary condition.

Quinolones in treatment of human brucellosis: comparative trial of ofloxacin-rifampin versus doxycycline-rifampin

Quinolones have been reported to be active against Brucella species in vitro. In this prospective randomized study, the efficacy and safety of the combination of ofloxacin plus rifampin were compared with the efficacy and safety of doxycycline plus rifampin, both combinations administered for a 6-week period in treatment of brucellosis. Sixty-one patients were enrolled in the study, and 49 had blood or bone marrow cultures positive for Brucella melitensis. Thirty patients received 200 mg of doxycycline plus 600 mg of rifampin once daily, and 31 patients were treated with 400 mg of ofloxacin plus 600 mg of rifampin once daily for 6 weeks. Nine patients in each group had complications of the disease. There was one therapeutic failure in the ofloxacin-rifampin treatment group, and one patient from each group relapsed (3.3% of those in the doxycycline-rifampin treatment group versus 3.2% of those in the ofloxacin-rifampin treatment group). Gastric discomfort was the major side effect observed in 13 patients (43.3%) who received doxycycline plus rifampin, whereas only 2 patients (6.5%) treated with ofloxacin plus rifampin complained of gastric irritation. These results suggest that the combination of ofloxacin plus rifampin administered for 6 weeks is as effective as doxycycline plus rifampin given for the same period, regardless of the presence of complications of the disease.

Factors influencing prognosis in bacteremia due to gram-negative organisms: evaluation of 448 episodes in a Turkish university hospital

A total of 448 episodes of bacteremia due to gram-negative organisms observed during the 7-year period between 1983 and 1989 at Hacettepe University Hospitals were studied for evaluating the factors influencing the prognosis. The overall mortality rate was 45.0%. The mortality rates were not significantly different in "rapidly fatal" and "ultimately fatal" disease groups (48.3% and 45.5%, respectively), whereas it was significantly less (34.8%) in the "nonfatal" disease group compared with the "rapidly fatal" category. There were great differences in the mortality rates among different diseases within the same disease category. Shock, multi-organ failure, source of infection, hospital service, appropriateness of antibiotic therapy, and place of acquisition of infection were found to affect prognosis significantly in multivariate analysis. In conclusion, the identification of prognostic factors is a further step for making necessary interventions in reducing the mortality rate associated with bacteremia due to gram-negative organisms. Underlying disease is still an important prognostic factor; however, a new approach is needed for classification of underlying diseases.

Long-term oral ciprofloxacin in the treatment of prosthetic valve endocarditis due to Pseudomonas aeruginosa

Prosthetic valve endocarditis caused by Pseudomonas aeruginosa is refractory to medical treatment alone and early valve replacement is necessary. We describe a 40-year-old patient in whom endocarditis developed in the early postoperative period, and reoperation was not considered feasible. Ciprofloxacin was administered orally in order to suppress bacteremia for 36 months. Long-term oral ciprofloxacin may provide an opportunity in the treatment of prosthetic valve endocarditis caused by Ps. aeruginosa in patients who are unfavorable candidates for reoperation.

An unexpected potent positive chronotropic effect of (15S)-15-methyl-prostaglandin E1 in the isolated guinea-pig right atria

The effects of (15S)-15-methyl-prostaglandin E1, a synthetic analog of PGE1, other stable prostaglandins, histamine and noradrenaline were studied on the isolated spontaneously beating right atria from guinea-pig, rat and rabbit. When compared with other prostaglandins, histamine and noradrenaline, 15-methyl analog of PGE1 has the most potent positive chronotropic effect and the highest affinity as indicated by a significantly higher pD2 value as compared to other tested analogs in the isolated guinea-pig right atria. Neither the 15-methyl analog of PGE1 nor other stable prostaglandins induced any effect on the atria from rat and rabbit when relatively higher concentrations were used. 15-Methyl-PGE1 did not induce a positive inotropic effect. The maximum positive chronotropic response to 15-methyl-PGE1 was found to be about 60% of that of noradrenaline and histamine but almost equal to that of PGE1. These results were taken as evidence that 15-methyl-PGE1 has an unexpected potent positive chronotropic effect on the isolated spontaneously beating guinea-pig right atrium. The possible mechanism of the action of 15-methyl-PGE1 are discussed.