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Biomedical subjects

R Gerard

Publications and source records attributed to R Gerard.

At least 37 records · Page 2Linked to original sources
PubMed1988

Asymptomatic form of left pulmonary artery sling.

Eight patients with left pulmonary artery sling, which were asymptomatic at the time of the last consultation, are described: 2 adults and 1 child with no history of symptoms, 3 children with mild forms of airways obstruction and 2 patients with typical severe symptoms of airways obstruction in infancy. The mean follow-up of these 8 patients was 10 years (range 4 to 23), and in 1986, all were in good health and free of respiratory symptoms. The long-term prognosis is usually good.

Airway Obstruction↗
PubMed1987

Tissue plasminogen activator: from molecular biology to myocardial infarction.

The recent development of recombinant tissue plasminogen activator as a therapeutic agent during acute myocardial infarction is one of the most lucid examples of the potential impact of recombinant DNA technology in clinical medicine. This remarkable achievement would not have been possible without several key discoveries in molecular biology and clinical cardiology and exemplifies the synergistic relationship between basic and clinical research. This article chronicles this journey from molecular biology to myocardial infarction.

Fibrinolysis↗
PubMed1986

Functional analysis of the role of the A + T-rich region and upstream flanking sequences in simian virus 40 DNA replication.

One boundary of the minimal origin of replication of simian virus 40 DNA lies within the A + T-rich region. Deletion of only a few bases into the adenine-thymine (AT) stretch results in a DNA template which is defective for replication both in vivo and in vitro (B. Stillman, R. D. Gerard, R. A. Guggenheimer, and Y. Gluzman, EMBO J. 4:2933-2939, 1985). In the present study, such deletion mutations have been reconstructed into a simian virus 40 genome containing an intact early promoter-enhancer region. The resulting mutants synthesized wild-type levels of T antigen, but were defective for replication and would not form plaques on CV-1 monkey cells. Replication-competent phenotypic revertants were selected after transfection of large quantities of the replication-defective viral DNAs into CV-1 cells. DNA sequence analysis showed that most of these revertants contained insertions or point mutations which partially regenerate the length of the AT stretch. These genotypic alterations were shown to be responsible for the revertant phenotype by replication analysis in vivo of subcloned revertant origin fragments. In general, our results emphasize the importance of the AT region to simian virus 40 origin function. However, one revertant retained the altered AT region but deleted six nucleotides upstream. Experiments using this mutant indicate that the 21-base-pair repeats identified as part of the early transcriptional promoter may compensate for defects in simian virus 40 DNA replication in vivo caused by mutations in the A + T-rich region when positioned at an appropriate distance from the core origin.

Adenine↗
PubMed1985

Alternate ventriculo-atrial Wenckebach conduction during ventricular tachycardia.

Although pacing-induced ventriculo-atrial (VA) Wenckebach conduction has been previously described, the occurrence of this phenomenon during ventricular tachycardia has received little attention. The latter is defined as 2:1 VA block in which the conducted beats show progressive lengthening of VA conduction until the sequence is terminated by two or three blocked ventricular beats. This phenomenon was observed in a 16-year-old boy who underwent electrophysiologic study for ventricular tachycardia as a late complication of surgical correction of tetralogy of Fallot. During pacing-induced ventricular tachycardia with a morphology similar to that of the spontaneous tachycardia, 8:4 alternating VA block was observed. This sequence suggested that the AV node was the site of block, the 2:1 block being located at the upper level, and the VA Wenckebach block at the lower level. Alternate VA Wenckebach conduction appears as a possible cause of variation in atrial depolarization intervals during ventricular tachycardias with short cycle lengths.

Adolescent↗
PubMed1984

Bepridil for recurrent sustained ventricular tachycardias: assessment using electrophysiologic testing.

Bepridil was found to possess electrophysiologic properties common to class I and IV antiarrhythmic agents. Intravenous and oral bepridil were evaluated using serial electrophysiologic studies in a selected group of 9 patients with recurrent sustained ventricular tachycardia (VT) unresponsive to usual therapy, including amiodarone therapy in 15 patients. Intravenous bepridil treatment terminated sustained, well tolerated, pacing-induced VT in 3 of 6 patients and prevented the initiation of VT in 2 of these and in a patient in whom the drug failed to restore sinus rhythm. Oral bepridil was administered at a loading dose of 800 mg on day 1, and 500 to 600 mg the following days, and programmed electrical stimulation was repeated 2 to 6 days after initial study. Oral bepridil therapy prevented VT initiation in 6 patients (66%). The tachycardia cycle length was prolonged (30 to 105 ms) in 2 patients in whom VT remained inducible. In 1 patient the tachycardia cycle length significantly shortened after bepridil and prompt cardioversion was required. Five of the 6 patients with successful results underwent long-term oral treatment with bepridil. VT recurred in 1 patient during the hospitalization period and an adverse effect (paralytic ileus) in another patient required drug discontinuation. Three patients remain symptom-free over a follow-up of 4 to 13 months. These data suggest that bepridil may be useful in patients with recurrent, sustained VT.

Administration, Oral↗
PubMed1982

Bidirectional tachycardia. Mechanism derived from intracardiac recordings and programmed electrical stimulation.

His bundle recordings and programmed electrical stimulation were performed in a 70-year-old woman with bidirectional tachycardia; the recordings demonstrated the infra-Hissian origin of the tachycardia. Occurrence of the His deflection slightly after the onset of ventricular depOlarization suggested that the origin of the tachycardia was located near the His bundle bifurcation. Recording of three atrial sites during tachycardia allowed the study of retrograde atrial activation. Two sets of fairly constant and alternating VA intervals were recorded. This fact is consistent with two ventricular circuits used alternatively. The tachycardia could also be interrupted with a single atrial or ventricular premature beat. It is postulated that the tachycardia is due to macroreentry involving the two fascicles of the left branch. This study suggests that reentry may be a possible mechanism in some cases of bidirectional tachycardia.

Aged↗
PubMed1979

Long-term results of permanent atrioventricular sequential demand pacing.

Pervenous atrioventricular sequential demand pacemakers (AVSDPs) were implanted in 18 patients using an atrial electrode positioned in the right atrial appendage and a ventricular electrode positioned at the apex of the right ventricle. The indications included 13 patients with the sick sinus syndrome (72%), five of whom had the tachycardia-bradycardia syndrome, three with paroxysmal supraventricular tachycardia, one with cardiomyopathy and one with carotid sinus syncope. The follow-up ranged from 6 to 38 months, with a mean of 19.4 months (a total of 350 pacing months). Seventeen patients (94%) are asymptomatic. One patient had persistent episodes of paroxysmal supraventricular tachycardia. In the remaining patients with tachyarrhythmia, pacing alone (three patients) or in combination with antiarrhythmic drugs (four patients) controlled the tachyarrhythmia. There was one displacement of the atrial electrode (5.5%). Extrusion of the pacer occurred in three patients. It is concluded from this experience that AV sequential pacing is an effective technique and may be useful in patients with sick sinus syndrome, in patients with tachyarrhythmia and/or patients with poor myocardial function. However, continued research is needed to prolong battery life and to reduce the size of the pacemaker.

Aged↗
PubMed1977

[Coronary insufficiency in the female: possible effect of menopause].

A population of 239 women suffering from chronic coronary disease was divided into two groups according to whether or not they had sustained a myocardial infarction. For the 226 post-menopausal women, the type of menopause (natural or artificial) and their age at its onset were determined, together with the age of onset of the infarction or angina, and possible correlations with other risk factors in atherosclerosis. Whilst the average age at the time of artificial menopause was markedly less than that of natural menopause, the age of onset of coronary complications was comparable regardless of the type of menopause, this applying to both groups. Contrary to a classically accepted opinion, early menopause would not appear to favourise the premature development of atherosclerotic coronary problems, and, in addition, would not appear to affect other coronary "risk factors".

Adult↗
PubMed1976

[Electrophysiologic study of fenoxedil chlorhydrate].

Electrophysiologic studies were carried out on 10 patients before and during therapy by Fenoxedil Chlorhydrate a new anti-arrhythmic drug, to determine the effects on cardiac conduction. Fenoxedil Chlorhydrate produces a constant alteration of intra-nodal conduction. Modification of sinus function are less evident. Auricular and ventricular refractory periods are increased in the majority of cases. These results give a better understanding of mecanism of this drug, and helps in its prescription in clinical practice.

Anti-Arrhythmia Agents↗
PubMed1975

[Propranolol and arterial hypertension: study with frequent daily checking of blood pressure and serum levels after 1 week of treatment].

In order to establish correlations between serum levels of Propranolol, blood pressure in hypertensive patients and cardiac rate, these parameters have been recorded at three different times in a day and after a week. This study points out that therapeutic response is variable. However the patients may be classified into 4 groups. This classification and the value of serum levels of propranolol are discussed.

Blood Pressure↗