Antiarrhythmic drug therapy for atrial fibrillation: focus on atrial selectivity and safety

Atrial fibrillation (AF) is a highly prevalent arrhythmia and responsible for significant morbidity, mortality and health care cost. The prevalence of AF is expected to increase markedly with the aging population. The use of conventional antiarrhythmic agents has been limited by potentially fatal ventricular proarrhythmia. Rhythm control could become the preferred treatment strategy for AF if antiarrhythmic agents that are similarly or more effective, but safer, than currently approved AF agents become available. A subanalysis of the Atrial Fibrillation Follow-Up Investigation of Rhythm Management (AFFIRM) trial data showed that normal sinus rhythm confers a survival benefit in AF, suggesting that rhythm control, if achieved without the adverse effects related to current antiarrhythmic medications, may offer a significant survival advantage over rate control. Considerable work has been performed to explore novel, potentially safer antiarrhythmic drug targets for AF therapy, and some of these drug targets are currently being tested in experimental and clinical proof of concept studies. This article summarizes relevant aspects of the cellular electrophysiology of AF and reviews the actions of pharmacological agents being considered for the prevention and treatment of AF, focusing on atrial selective antiarrhythmic agents. A variety of drugs that inhibit the atrium-specific ultra rapid delayed rectifier potassium current (IKur) are being evaluated pre-clinically, but human experience with these agents is limited. The acetylcholine-activated current (IKACh) is another novel candidate target for atrial-specific drug therapy. The constitutively active form of this current is increased in human AF and pharmacological inhibition might be of therapeutic value. Certain drugs have IKACh blocking properties, but similar to IKur-blockers, none have been shown to have pure selectivity for this current. Newer agents being studied also include gap junction modulators and angiotensin-converting enzyme inhibitors. There is great hope that at least some of these agents will ultimately be available for effective and safer clinical treatment and prevention of AF.

Identification of H-ras mutations in urine sediments complements cytology in the detection of bladder tumors

BACKGROUND

Urinary cytology has long been used as a noninvasive screen for the detection of urinary tract cancer but is limited by the generation of false positive and false negative results. More recently, molecular changes associated with urothelial neoplastic progression have been identified in DNA from urine sediments, demonstrating an alternative approach for identifying neoplastic change in the bladder.

PURPOSE

The purpose of this prospective study was to determine the value of detection of H-ras (also known as HRAS) mutations in urine sediment DNA as a clinical indicator of tumor presence, recurrence, and/or progression.

METHODS

Urine sediments were collected from 100 patients presenting with bladder tumors, with follow-up samples collected from 19 patients. DNA extracted from urine sediments was analyzed for changes in exon 1 of the H-ras gene, using single-strand conformation polymorphism (SSCP) analysis. A representative number of aberrant H-ras/SSCP migrating bands were excised and sequenced to confirm the presence of a mutation. Human bladder specimens were obtained from patients (93 of the 100 patients initially and 18 of the 19 patients studied by follow-up) and histologically evaluated for tumor content and grade.

RESULTS

Mutations in exon 1 of the H-ras gene were detected in urine sediments from 44% (44 of 100) of the patients; concordant results were obtained by cytologic analysis, where 33% (31 of 93) of the patients displayed positive cytology. Analysis of the distribution of abnormalities with tumor grade revealed greater detection of low-grade (1-2) lesions using ras analysis (47%) compared with cytology (16%). In contrast, cytology was more effective in identifying the presence of carcinoma in situ. Combined results from these two approaches substantially increased the sensitivity of tumor detection, resulting in the identification of tumors in 60% of patients.

CONCLUSIONS

Identification of H-ras mutations in DNA from urine sediments facilitates the detection of low-grade bladder tumors and, in combination with cytology, increases the overall tumor detection from 33% to 60%. Preliminary results in patient follow-up suggest that detection of H-ras mutations may have some clinical utility in detecting the presence of abnormal cells in the absence of an overt lesion following cystoscopy or positive cytology.

Screening of human bladder tumors and urine sediments for the presence of H-ras mutations

A series of 111 human bladder tumors were screened using oligonucleotide mutant specific probes, restriction enzyme analysis and single-stranded confirmation polymorphism (SSCP) for the presence of H-ras activation events. Thirty-three tumors were found to harbor H-ras mutations where a glycine to valine (G-->T) change in codon 12 was the most common point mutation recorded (26 tumors). Additional mutations involved glycine to cysteine at codon 13 (2 tumors) and glutamine to arginine/lysine/leucine at codon 61 (3/1/1 tumors, respectively). Ambiguous signals recorded with oligonucleotide probes were further analyzed using SSCP analysis revealing the presence of H-ras mutations in restricted regions of some tumors. The apparent sensitivity of SSCP enabled us to extend this study to DNA isolated from urine sediments where 4 of the 9 patients studied showed representation of mutant H-ras. Our study demonstrates a sensitive, non-invasive assay for the screening of urine-borne cells, with no requirement for prior knowledge of the mutational change at the H-ras locus.

[Hepatic involvement in the course of ovarian hyperstimulation syndrome]

The authors report the case of hepatic damage with a favorable outcome, occurring during severe ovarian stimulation which had anatomico-clinical features which distinguished it from the three cases previously reported due to its exclusively cytolytic nature and the histological lesions produced. The physiopathological mechanisms involved are discussed.

[Acute respiratory distress syndrome caused by tuberculosis]

The adult respiratory distress syndrome (ARDS) is rarely due to tuberculosis. Two new cases are reported here. Both were female patients, aged 33 and 41 years. The first, of North African origin, was admitted for epigastralgia, hyperpyrexia and intestinal problems. She underwent an exploratory laparotomy, which only showed oedematous mesenteries. Hepatic and lymph node biopsies revealed an ongoing tuberculosis. On the 4th postoperative day, she developed ARDS. Despite an initial period of improvement after proper treatment (antituberculous drugs, steroids, positive pressure ventilation) had been started, she died 27 days later. In the other patient, smoker and alcoholic, the diagnosis of tuberculosis relied only on bacterial culture of various excretions. She also died after 8 days of treatment. In both patients, the symptoms were atypical. The febrile non cardiogenic pulmonary oedema of sudden onset masked the typical miliary mottling pattern on chest X-rays. The life-threatening character of this condition requires that rapid histological studies are carried out to obtain an early diagnosis. Indeed, the precociousness of appropriate treatment seems to be the essential element of the prognosis.

[Primary ulcerations of the small intestine]

The authors report a recent case of primary ulceration of the small intestine revealed by spontaneous perforation. This is a rare condition with a non specific semiology which only exceptionally permits diagnosis before complications occur. The latter are dominated by perforation, gastrointestinal hemorrhage and a sub-acute obstructive syndrome. The lesion, generally single, is found on the anti-mesenteric border of the jejunum or terminal ileum on a short only slightly inflammed segment and pathological examination does not reveal any specific process. Treatment is surgical. It confirms the diagnosis and enables a segmentary resection or simple suture to be carried out. The condition does not recur. A complete etiological investigation is required to exclude other causes of small intestinal ulceration before its "spontaneous" nature may be inferred. Infectious and vascular theories are most often proposed among the pathophysiological hypotheses. Far from being exclusive, these theories may interact and enable a coherent multi-factorial mechanism to be proposed as to the origin of the ulceration (regardless of its initial cause). Spontaneous ulcers are therefore included in a wider nosological classification ranging from stress ulcer to necrosing enteritis.

[Multiple sclerosis disclosed by spinal anesthesia]

A case is reported of an acute onset of previously undiagnosed multiple sclerosis, revealed by an oculomotor paralysis following spinal anaesthesia performed for minor orthopaedic surgery. The need for a complete preoperative physical examination is underlined by this case, looking for latent neuromuscular disorders before undertaking such techniques, and for a thorough neurological work-up should such a complication arise. The harmlessness of regional anaesthesia in multiple sclerosis patients is controversial; without entering into such a debate, the direct relationship between spinal anaesthesia and acute exacerbation of the disease in our patient seemed more than likely.

Transformation of precrisis human cells by the simian virus 40 cytoplasmic-localization mutant pSVCT3 is accompanied by nuclear T antigen

pSVCT3 is a cytoplasmic-localization mutant of simian virus 40 (SV40) isolated from the SV40 adenovirus 7 hybrid virus (PARA) and cloned into plasmid PBR. The large T antigen of pSVCT3 accumulates in the cytoplasm of infected monkey cells instead of being transported to the nucleus. The sole change in CT3 large T antigen is amino acid residue 128 (Lys----Asn). Transformation of precrisis rodent cells by pSVCT3 is negligible, whereas the frequency of transformation of established rodent cell lines by pSVCT3 is comparable to that of wild-type SV40. According to the model, in which transformation of precrisis cells involves the combined oncogenic action of both nuclear and cytoplasmic gene products, we predicted that pSVCT3 would localize in the cytoplasm of human cells and would therefore at most only partially and rarely transform precrisis human cells. We have found that pSVCT3 is able to transform precrisis human cells at high frequency. Furthermore, pSVCT3-transformed human precrisis cells relocalized T antigen to their nuclei. The relocalization of large T antigen was not dependent on cell growth. Wild-type and pSVCT3-transformed human cell lines both have about five copies of integrated SV40 DNA. SV40 virus-specific proteins, including the 100,000-molecular-weight super large T antigen, were expressed in pSVCT3-transformed human cells. Our results suggest that molecules in precrisis human cells, but not cells of other species, are able to complement the cytoplasmic-localization defect of the CT3 mutant large T antigen.

[Polyradiculoneuritis and pregnancy. Apropos of 1 case]

The authors report a case of severe Guillain-Barre syndrome that appeared during the eighteenth week of a second gestation which evolved to full term without complication. The particularity of this observation was that the follow-up of the foetus was made possible for the first time by echography which showed normal active foetal movements even during maximum maternal paralysis. From of review of thirty three cases recorded in the literature, it seems clear that the interrelationship between the neurological disorder and pregnancy is nil or minimal beside an increased risk of prematurity childbirth can proceed normally and cesarean section is not indicated. Plasmapheresis proposed as an early treatment is discussed in the case of pregnant women. Today pregnancy is no longer a particular contraindication of such management.