Search PubMed⌕ Search

Biomedical subjects

D David

Publications and source records attributed to D David.

At least 163 records · Page 9Linked to original sources
PubMed1983

Superiority of oral verapamil therapy to digoxin in treatment of chronic atrial fibrillation.

The efficacy and safety of oral verapamil, 240 mg, with or without digoxin were studied in 52 patients with chronic atrial fibrillation at rest, and during mild and maximal exercise. Twenty-four patients were studied during the following therapeutic modalities: no therapy; digoxin, 0.25 mg and 0.5 mg daily; digoxin, 0.25 mg and verapamil; and verapamil alone. Heart rate at rest and during all levels of exercise was decreased significantly (p less than 0.005), either by combining digoxin with verapamil or by verapamil therapy alone. In contrast, the excessive heart rate response to exercise was not prevented by digoxin even with good serum concentrations. The improved control of heart rate with verapamil was associated with a significantly improved exercise capacity. Verapamil is an important and safe modality of treatment, with or without digoxin, in the long-term control of heart rate in chronic atrial fibrillation. It is superior to digoxin in controlling the ventricular rate and in improving exercise capacity.

Administration, Oral↗
PubMed1983

Effect of variations in room temperature on measured values of blood gas quality-control materials.

We compared four commercial quality-control materials equilibrated in sealed ampoules at 21 or 26 degrees C in three models of blood gas machines and found po2 differences of about 13.3 Pa (10 mmHg) for an aqueous mixture with hemoglobin; about 6.7 Pa (5 mmHg) for two aqueous buffers without hemoglobin, and none for a fluorocarbon-containing emulsion. Differences for pco2 and pH were small but statistically significant. Variability within machines for pco2, po2, and pH was small but differences among machines were large, especially for po2. These results emphasize that aqueous solutions and hemoglobin-containing mixtures used for proficiency testing and quality control should be equilibrated at the temperature recommended by the manufacturer, opened, and sampled promptly.

Blood Gas Analysis↗
PubMed1982

Role of early cycle ventricular extrasystoles in initiation of ventricular tachycardia and fibrillation: evaluation of the R on T phenomenon during acute ischemia in a canine model.

Eighteen open chest dogs anesthetized with pentobarbital sodium were studied to determine the role of early cycle premature ventricular beats in the initiation of ventricular tachycardia and fibrillation during the initial 30 minutes of acute myocardial ischemia. The coupling interval and prematurity index (R-R'/R-R) of every premature beta after a sinus beat were determined during both the "immediate" (2 to 12 minutes) and "delayed" (13 to 30 minutes) phases of ventricular arrhythmias that follow acute coronary ligation. During the immediate phase, characterized by marked fractionation of local electrograms and delayed intramyocardial conduction, early cycle beats were infrequent (8 percent of extrasystoles) and initiated only 3 (4 percent) of 75 episodes of ventricular tachycardia and fibrillation. However, during the delayed phase, characterized by less fractionation and more uniform conduction, early cycle beats were both more frequent (24 percent of extrasystoles, p less than 0.001) and more successful (20 [34 percent] of 59 episodes, p less than 0.001) in initiating ventricular tachycardia and fibrillation. Thus, the underlying electrophysiologic derangements appeared to be of primary importance in determining both the frequency and relative malignancy of early cycle beats during acute myocardial ischemia.

Acute Disease↗
PubMed1982

Q-T prolongation and polymorphous ("torsade de pointes") ventricular arrhythmias associated with organophosphorus insecticide poisoning.

It is not generally appreciated in the Western world that organophosphorus poisoning may be associated with a serious and often fatal cardiac complication: Q-T interval prolongation with malignant ventricular arrhythmias of the "torsade de pointes" type. This insidious complication may lead to delayed, sudden death after the patients appears to be well on the way to recovery from the other, more dramatic respiratory and neurologic symptoms. In this study 15 patients with organophosphorus poisoning are described. Q-T prolongation was observed in 14 and malignant tachyarrhythmias in 6. In view of the dismal prognosis of these patients, ventricular pacing, previously used with success in other conditions associated with this syndrome, was tried in four patients and successfully shortened the Q-T interval and eliminated the arrhythmias. Isoproterenol did the same in a fifth patient. Awareness of this lethal, but preventable complication of organophosphorus poisoning is called for. Careful electrocardiographic monitoring is necessary until the Q-T interval returns to normal. Electrical pacing appears to be the treatment of choice for the tachyarrhythmias.

Adolescent↗
PubMed1982

Influence of technical and commercial decamethrin, a new synthetic pyrethroid, on the gonadic germ population in Quail embryos.

Contamination of Quail eggs with the synthetic pyrethroid decamethrin significantly reduced the gonadic germ population in 5 day-old embryos. Technical grade and commercially formulated pesticides were used, the commercial excipient and its main hydrocarbon constituent (xylene) were also tested. Eggs were treated either directly by intravitelline injection (1.25 mg, 0.80 mg or 0.30 mg of active substance by egg) or spraying of the shell (with a 2% aqueous suspension of pesticide) or indirectly through repeated ingestion by the parental birds of feed contaminated with 100 ppm of pyrethroid. Reduction in germ potential was primarily due to the excipient used in the formulation of the commercial product. The xylene, main constituent of the matrix, was responsible of this reductive effect. These chemicals (excipient and xylene) were also chiefly responsible for the high embryo mortality rate observed after injection. Both excipient alone and formulated decamethrin were distinctly less embryolethal when sprayed onto eggs or added to feed.

Animal Feed↗
PubMed1982

[Action of decamethrin, of its commercial solution, of the excipient and of xylene on the quail biotic potential. Effect on the embryonic genital system].

The following products were tested: 1) the purified new synthetic pyrethroid decamethrin; 2) its commercial solution; 3) the excipient of the commercial solution; and 4) the main constituent of the excipient xylene. Eggs were treated either directly by spraying of the shell with 2% and 0.05% aqueous suspensions of commercial decamethrin, excipient and xylene; or indirectly by repeated ingestion by the parental quails of fed contaminated with the four chemicals. All these constituents significantly acted upon the quail biotic potential; they reduced the hatching rate and the embryonic viability and, on the contrary, increased the fecundation rate and the weight of eggs, chickens and adults. Moreover, they reversed the sex-ratio, what brought about the male birds to have the advantage in number. At last, they acted more specifically on the embryonic genital development. The comparative study of effects of both the pesticide and its excipient showed that the later, and more exactly the xylene, was the main responsible factor.

Animals↗
PubMed1981

[Ultrastructure and cytochemistry of primordial germ cells involved in migration in dichlorvos-treated quail embryos].

In dichlorvos-treated quail embryos, the ultrastructural cytochemistry of gonads reveals perturbations in the glycoconjugate distribution. The modifications observed concern the surface and matricial glycoconjugates of tissues involved in the primordial germ cells (PGC) migration. In treated embryos, these cytochemical alterations could explain a delayed migration of PGC to germinal anlage and their disturbed settling into gonads.

Animals↗
PubMed1981

Atrial alternans: experimental echocardiographic and hemodynamic demonstration during programmed pacing.

Simultaneous hemodynamic and echocardiographic recordings were used to demonstrate mechanical atrial alternans during programmed atrioventricular (A-V) pacing in five open chest dogs. Each animal was studied in two stages, first with the A-V conduction system intact (phase I) and later after the experimental induction of complete A-V block (phase II). Atrial alternans was demonstrated during rapid atrial stimulation at cycle lengths ranging from 250 to 120 ms. During phase I, rapid atrial pacing resulted in complex combinations of variable A-V conduction disturbances with superimposed atrial and ventricular alternans. During phase II, atrial alternans could be observed during a programmed prolonged pause in ventricular activity. It is anticipated that this method will facilitate recognition of atrial alternans in various clinical situations and shed further light on its possible hemodynamic significance.

Animals↗
PubMed1981

Exercise cross-sectional echocardiographic diagnosis of coronary artery disease.

To test the feasibility of detecting transient left ventricular regional wall motion abnormalities during exercise-induced myocardial ischemia, 55 patients undergoing diagnostic coronary arteriography were studied in a prospective blinded manner with wide angle cross-sectional echocardiography. The ultrasonic studies were obtained with the patients at rest and during exercise in the supine position using a bicycle ergometer. Cross-sectional echocardiographic studies during exercise were adequate for analysis in 43 (78 percent) of the 55 patients. Forty-one of the 43 manifested either a new regional wall motion abnormality during exercise (20 subjects) or wall motion that remained entirely normal during exercise (21 subjects); in two subjects an abnormal wall motion abnormality at rest did not change with exercise. Nineteen of the 20 patients with a new regional wall motion abnormality had significant coronary artery disease and 15 of these 19 had S-T segment depression during bicycle ergometry. The one patient with a normal coronary arteriogram had an early cardiomyopathy. Ten of the 21 subjects with normal wall motion at rest and during exercise had a normal coronary arteriogram, whereas 11 had evidence of important anatomic coronary artery disease and thus had a false negative echocardiographic findings. Six of these 11 patients had S-T segment depression during exercise. The usefulness of exercise echocardiography to predict coronary artery disease was not altered even when only 26 patients without previous myocardial infarction and with a normal cross-sectional echocardiogram at rest were considered. Thus, new regional wall motion abnormalities during exercise as identified with cross-sectional echocardiography represent a specific finding for the presence of coronary artery disease. However, normal regional wall motion during exercise does not exclude the presence of important anatomic coronary artery disease.

Adult↗
PubMed1981

The use of the balloon-tipped floating catheter in temporary transvenous cardiac pacing.

The effectiveness and safety of balloon-tipped, flow guided, electrodes for ventricular pacing as opposed to the fluoroscopy-guided semi-rigid bipolar electrodes have never been compared in a controlled study. A prospective study was therefore undertaken to compare both techniques in semi-elective and emergency procedures. Flow guided electrodes were inserted in 67 patients (group A) and semi-rigid electrodes in 44 patients (group B). The results of group A were judged to be superior to those of group B in four aspects: a) shorter time (6'45" vs. 13'30", p less than 0.0005); b) lower incidence of catheter displacement (13.4 vs. 32.0 percent, p less than 0.05); c) longer interval of time between implantation and catheter displacement (4.4 vs. 1.9 days, p less than 0.0005); d) lower incidence of serious ventricular arrhythmias during insertion (1.5 vs. 20.4 percent, p less than 0.005). Threshold at insertion was not significantly different (0.6 +/- 0.3 vs 0.7 +/- 0.2 milliampere). The superiority of flow-guided electrodes over fluoroscopy-guided electrodes persisted in the comparison of semielective insertions in groups A and B. We conclude that the flow-guided insertion technique is safer, more expeditious and more stable than the fluoroscopy-guided technique in semi-elective as well as in emergency insertions.

Adolescent↗
PubMed1981

Mid-systolic click and echocardiographic evidence of mitral valve prolapse during electrical pacing.

A mid-systolic click was present in a patient during three years of follow-up after implantation of a permanent transvenous pacemaker. Echocardiography revealed posterior motion of the anterior leaflet which resembled mitral valve prolapse. Both the click and echocardiographic evidence of prolapse disappeared simultaneously with resumption of sinus rhythm and during supraventricular tachyarrhythmias. Wtih spontaneous change in the position of the electrode three years after initial implantation, both the click and the posterior motion of the mitral valve disappeared. The association of mitral valve prolapse with electrical pacing is most unusual and appears to have a distinct pathophysiological mechanism.

Aged↗
PubMed1981

R-wave amplitude variations during acute experimental myocardial ischemia: an inadequate index for changes in intracardiac volume.

The role of intracardiac volume in controlling electrocardiographic R-wave amplitude changes during acute myocardial ischemia was studied in 24 open-chest dogs. The R-wave amplitude in surface ECG leads 2, V5 and Frank X, Y and Z leads were correlated with hemodynamic, echocardiographic and angiographic changes in a 5-minute circumflex coronary artery ligation and reperfusion model. After coronary ligation, left ventricular end-diastolic diameter and volume increased progressively above control, reached a peak and plateau at 120--130 seconds after ligation and did not return to control levels until more than 5 minutes after release of the occlusion. In contrast, the R-wave amplitude showed a biphasic response to acute ischemia, reaching a nadir (sigma R = 18.2% below control) at 30 seconds after coronary ligation and only subsequently increased to reach a peak (sigma R = 52% above control) at 150 seconds after ligation. In addition, R-wave amplitude returned immediately to control levels within 10 seconds after reperfusion. In six other dogs, both venae cavae were occluded for a 30-second period, beginning 180 seconds after coronary ligation. Although intracardiac volume decreased markedly, R-wave amplitudes increased even more. Thus, the demonstration of discordance between alterations in intracardiac volume and R-wave amplitude in these studies suggests that factors other than intracardiac volume determine R-wave amplitude changes in the course of acute myocardial ischemia.

Acute Disease↗