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Biomedical subjects

D David

Publications and source records attributed to D David.

At least 181 records · Page 10Linked to original sources
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↗
PubMed1981

Laboratory evaluation of repellent properties against birds of the synthetic pyrethroid decamethrin.

Both technical grade and commercially formulated decamethrin administered in feed has a generally repellent action upon quail, with strong individual variations. The excipient used in the commercial preparation has a similar effect on its own, probably due to its odor. Repellency diminishes after repeated exposure and even becomes reversed in the case of the purified pyrethroid, which attracts intoxicated quail.

Animal Feed↗
PubMed1980

Echocardiographic detection of coronary artery disease. Detection of effects of ischemia on regional myocardial wall motion and visualization of left main coronary artery disease.

M mode and cross-sectional echocardiographic studies at rest have been used to detect regional left ventricular wall motion abnormalities as a sign of hemodynamically significant coronary artery disease. These techniques have proved to be fairly specific but not highly sensitive. Detection of new regional wall motion abnormalities with cross-sectional echocardiography during exercise appeared practical in 80 percent of patients in preliminary studies; the finding of such abnormalities is highly specific for the presence of coronary artery disease and, with this approach, the sensitivity of echocardiography is improved. Thus, patients with anatomically severe coronary artery disease on angiography may not manifest an echocardiographic abnormality in regional wall motion even during exercise. The direct noninvasive detection of the left main coronary artery in up to 90 percent of patients studied with cross-sectional echocardiography using the short axis or apical approach, or both, has been well defined. A high sensitivity and specificity of detecting anatomically severe left main coronary artery disease using the criteria of both luminal impingement and the presence of high intensity echoes have been confirmed. Further advances in imaging techniques may allow for better definition of the coronary arterial tree.

Coronary Disease↗
PubMed1980

Echocardiographic features of atrioventricular and ventriculoatrial conduction.

The potential application of diagnostic ultrasound to understanding of the hemodynamic effects of various rhythm and conduction disturbances has not been fully explored. To investigate the change in cardiac function associated with various atrioventricular (A-V) sequencing intervals during cardiac pacing, simultaneous M mode and two dimensional echocardigraphic and hemodynamic studies were performed in 23 dogs. One to one A-V and ventriculoatrial (V-A) sequential pacing at cycle lengths of 400 and 300 ms revealed a stepwise reduction in left ventricular pressure and cardiac output as the A-V interval was changed from +100 to -100 ms. These reductions in cardiac hemodynamics were associated with decreases in left ventricular and increases in left atrial dimensions determined with echocardiography. Mitral valve excursion and the duration of valve opening remained constant over the entire range of A-V intervals. There was angiographic evidence of retrograde blood flow from the left atrium into the pulmonary venous system at an A-V interval of -50 and -100 ms, but no evidence of mitral regurgitation. Thus, correlative echocardiographic and hemodynamic studies can suggest multiple pathophysiologic mechanisms contributing to the decrements in cardiac function observed during tachyarrhythmias with intact A-V conduction as well as those occurring consequent to A-V nodal Wenckebach cycles.

Animals↗
PubMed1980

Permanent overdrive pacing for the suppression of recurrent ventricular tachycardia in a newborn with long QT syndrome.

A newborn with long QT interval and repetitive ventricular tachycardia of the "torsade de pointes" type was seen at the age of one day. The arrhythmia was resistant to lidocaine, propranolol and atropine, but was controlled by isoproterenol infusion. A transvenous pacemaker, inserted at three days of age, suppressed the ventricular tachycardia at stimulation rates above 100/minute. At 19 days of age a permanent pacemaker at pulse rate of 119 beats/minute was implanted. At one year of age the infant was thriving and was completely free of ventricular arrhythmia.

Cardiac Pacing, Artificial↗
PubMed1980

The beneficial effect of the beta blocker timolol in stable agina pectoris.

Timolol is a new beta blocker with cardioselective properties. A single blind controlled study was performed to assess the efficacy of timolol maleate in doses of 10 to 30 mg per day in 20 patients affected by stable angina pectoris. The patients received a placebo for a baseline period of 2 weeks, followed by 12 weeks of timolol. The number of anginal attacks dropped from 14.9 attacks per week in the baseline period to a minimum of 4.6 attacks per week in the sixth week of treatment (P less than 0.01). The number of tablets of nitroglycerin taken per week was reduced from 6.5 during the baseline period to 2.3 in the sixth week of treatment. Resting heart rate decreased from a baseline mean value of 72 beats per minute to 51.7 and 53.7 per minute at weeks 6 and 12 respectively (P less than 0.01). Blood pressure both at rest and during exercise was significantly reduced. The mean work index measured during bicycle ergometry was 127 units before treatment; it increased by 29.4 units and 36.1 units during week 6 and week 12 respectively (P less than 0.05). There was a marked symptomatic improvement in 50% of the patients. Mild fatigue was a common side effect but it disappeared following reduction of dose. We concluded that timolol maleate significantly reduces the number of anginal attacks and increases the work capacity of patients affected by stable angina pectoris

Adrenergic beta-Antagonists↗
PubMed1980

Residual DDT in two successive generations of quail and their eggs.

Gas chromatographic analysis of residual DDT levels following external treatment of parent eggs shows contamination to be present not only in first generation quails but also in second generation eggs laid at the beginning of the laying period and in chicks and adults hatched from them. However, the amount of pesticide detected in second generation eggs laid lately and in all third generation eggs was not significantly higher than that found in control samples.

Animals↗
PubMed1980

Overdrive pacing in quinidine syncope and other long QT-interval syndromes.

Prolongation of QT interval is associated with repetitive paroxysm of a particular ventricular tachycardia. It is a typical complication of quinidine therapy but may occur in various other conditions. We used endocardial pacing in nine patients with prolongation of the QT interval who suffered from bouts of ventricular tachycardia and fibrillation. In six patients, the syndrome was due to quinidine and in three, to prenylamine. Acceleration of heart rate resulted in immediate suppression of all arrhythmias. Pacing was continued until the condition producing the QT prolongation disappeared. In one case, a permanent pacemaker was implanted, as the QT prolongation was congenital and permanent. The absolute QT interval was shortened by overdrive pacing from a mean value of 0.65 s to 0.50 s. The corrected QT interval remained prolonged (about 0.56 s). Thus, the arrhythmia was associated with the duration of the actual QT interval, and overdrive pacing was able to suppress it without shortening the corrected QT interval.

Adult↗
PubMed1979

Inefficacy of digitalis in the control of heart rate in patients with chronic atrial fibrillation: beneficial effect of an added beta adrenergic blocking agent.

The role of digoxin and the new beta adrenergic blocking agent, timolol, in controlling heart rate at rest and during exercise was investigated in 28 patients with chronic atrial fibrillation. Digoxin failed to prevent excessively rapid heart rates during mild to moderate exercise. Increasing digoxin blood levels from a mean of 0.6 to 1.8 ng/ml had no effect on heart rate either at rest or during exercise. The addition of timolol, 20 to 30 mg/day, resulted in a satisfactory and significant attenuation of the rapid heart rates both at rest and during exercise. Heart rates at rest were 91 and 98 beats/min in the patients with low and high digoxin dosage and rose to 135 and 139 beats/min, respectively, during exercise. Timolol reduced the heart rate to 67 at rest and to 92 beats/min during exercise. The effect of beta adrenergic blockade at rest was less pronounced in patients whose initial heart rates were below 90 beats/min. Digoxin alone may not suffice to control excessive heart rate in patients with chronic atrial fibrillation. The additional beta adrenergic blockade actually normalizes the heart rate response in these patients.

Adrenergic beta-Antagonists↗
PubMed1979

The importance of the genetic picture and globin synthesis in determining the clinical and haematological features of thalassaemia intermedia.

Twelve carriers of thalassaemia intermedia were studied. Their clinical and haematological picture was distinctly different from that in both heterozygotes and homozygotes for beta thalassaemia. Several genetic patterns were found responsible for thalassaemia intermedia: beta/delta beta thalassaemia, alpha 2 beta/beta thalassaemia-heterocellular HPFH. In a few subjects the genetic picture indicated that the patients were homozygous for beta thalassaemia, in spite of the mildness of the clinical situation. The lack of genetic uniformity was refelcted in very wide Hb A2 (2.5--8.7%) and Hb F (7.5--96.9%) ranges, as opposed to the noticeable degree of biochemical uniformity indicated by the very similar imbalance of globin chain synthesis: 0.33-0.54 for the non-alpha/alpha chain ratio in the peripheral blood. The mean for this parameter (0.43 +/- 0.05) was significantly different (P less than 0.001) from that observed in heterozygous carriers (0.60 +/- 0.10) and homozygous carriers (0.11 +/- 0.05) for beta thalassaemia. The marrow blood displayed a comparable pattern. It is therefore suggested that the severity of thalassaemia is attributable to the degree of chain synthesis imbalance.

Adolescent↗
PubMed1979

The beneficial effects of verapamil in chronic atrial fibrillation.

Digitalis preparations frequently fail to control heart rate in many patients who have chronic atrial fibrillation, particularly during physical exertion. The effects of orally administered verapamil, 160 to 240 mg/day, on the heart rate at rest and during mild exercise were studied in 23 digitalized patients with chronic atrial fibrillation of various causes. Verapamil substantially reduced the excessive heart rate response to exercise in well-digitalized patients who had chronic atrial fibrillation.

Aged↗
PubMed1978

Transtelephone adjustment of antiarrhythmic therapy in ambulatory patients.

The electrocardiograms of 80 ambulatory patients receiving antiarrhythmic therapy were supervised with the help of a transtelephone monitoring system. The patients used a pocket-size modulator and reported several times daily to the receiving center integrated into the intensive cardiac care unit. The surveillance lasted for 5-28 days during which various drugs in varying dosages were administered to suppress or prevent dysrhythmias. In 94% of the patients, a satisfactory therapeutic achievement was obtained. The transtelephone system provides easy diagnosis, immediate pattern recognition, direct and frequent contact with the ambulatory patient and long periods of follow-up. During this time, the proper antiarrhythmic agent can successfully be defined, its effective dose can safely be determined and unnecessary hospitalization can thus be prevented.

Adult↗
PubMed1978

Immune reactions associated with practolol therapy.

A review of adverse reactions following practolol therapy is presented. The appearance of antinuclear antibodies seems to herald the clinical manifestations. Antinuclear antibodies were found in 30% of patients treated with practolol for prolonged periods. It is suggested that patients who develop an immune reaction following practolol metabolize the drug differently than those who do not.

Antibodies, Antinuclear↗
PubMed1977

[Detection of DDT in quail eggs: quantitative analysis].

Significant residues of DDT have been found in the albumin and vitellus of Quail eggs, after external treatment of the shell with an aqueous suspension of commercial DDT. The rate of pesticide crossing varies according to the shell porosity and thickness. Residues of DDT have also been found in the control eggs and in the Quail industrial food.

Age Factors↗