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Biomedical subjects

T B Conradson

Publications and source records attributed to T B Conradson.

29 records · Page 2Linked to original sources
PubMed1984

Improved cardiac performance during exercise following hydralazine treatment in chronic heart failure.

Nine male patients with stable chronic heart failure of different etiology and optimally treated with digoxine and diuretics were given hydralazine, 50 mg b.i.d., during three months. Hemodynamic parameters were evaluated during upright submaximal exercise. An increase in cardiac index due to an increased stroke volume was noted following the first dose of hydralazine. After three months' treatment, cardiac index was further increased. The arteriovenous oxygen difference was initially unchanged, but significantly decreased following long-term treatment. These findings may indicate different effects of hydralazine acutely and after long-term treatment. It is suggested that the initial increase in blood flow is directed mainly to regions other than the exercising muscles, while more blood is directed to the muscles after long-term treatment. A possible mechanism to explain this postulated difference is discussed.

Aged↗
PubMed1982

A comparison of the acute and long-term hemodynamic effects of ventricular inhibited and atrial synchronous ventricular inhibited pacing.

Sixteen patients treated with a noninvasively programmable pacemaker were examined after a prolonged period of ventricular inhibited (VVI) and atrial synchronous ventricular inhibited (VDD) pacing. Maximal working capacity was determined by bicycle ergometry. Atrial and ventricular rates, brachial artery cuff pressure and breathing rate were determined at rest and during exercise. There was a mean increase in working capacity of 24% with VDD compared with VVI pacing (p less than 0.001). Thirteen of the patients were catheterized. During VDD pacing, cardiac output was significantly higher, particularly during exercise (+/- 32%) due to the capability of heart rate increase and despite a substantial compensatory stroke volume increase during VVI pacing. Arteriovenous oxygen difference was much higher during VVI pacing, reaching 164 +/- 14 ml/l during the highest work load, while the corresponding level during VDD pacing was 140 +/- 14 ml/l (p less than 0.001). During exercise, arterial blood lactate was significantly higher during VVI than during VDD pacing. Heart size was significantly smaller, 568 +/- 98 vs 530 +/- 96 ml/m2 BSA (p less than 0.05), during VDD pacing a questionnaire was completed by the patients to evaluate subjective symptoms and pacemaker preference. This part of the study favored the VDD mode of pacing. The conclusion of this study is that VDD pacing is superior to VVI pacing.

Aged↗
PubMed1980

Prophylaxis of ventricular tachyarrhythmias with intravenous and oral tocainide in patients with and recovering from acute myocardial infarction.

In a double-blind placebo controlled study, tocainide, 750 mg i.v. during a 15-minute period directly followed by 800 mg orally and later 400 mg t.i.d., was administered to patients wiht acute myocardial infarction (AMI). Treatment was started as soon as possible following onset of symptoms; the follow-up period was 6 months. The patient groups consisted of 56 tocainide and 56 placebo patients. There was no significant effect on the incidence of ventricular fibrillation or symptomatic ventricular tachycardia. The mortality rates were similar and low in both groups. Tocainide suppressed ventricular arrhythmias, including ventricular tachycardia, both in the acute stage of AMI and during convalescence. Tocainide also suppressed exercies-induced ventricular arrhythmias. Side effects were in general mild or moderate.

Administration, Oral↗
PubMed1980

Tocainide kinetics after intravenous and oral administration in healthy subjects and in patients with acute myocardial infarction.

Tocainide is structurally related to lidocaine but may be used orally as well as intravenously. A therapeutic plasma concentration range of 25 to 45 mumole/l has been suggested. Tocainide kinetics were studied in 6 healthy subjects and 16 patients with acute myocardial infarction. There was good accordance in kinetics of healthy subjects and patients. After intravenous administration the mean t1/2 was about 14 hr, volume of distribution about 3.0 l/kg, and corrected renal clearance about 140 ml/min. An average of 35% of the dose was recovered unchanged in urine. After oral administration the absorption rate was rapid relative to the elimination rate, extent of bioavailability was complete, and the apparent volume of distribution was the same as that after intravenous injection. A dose regimen of 750 mg intravenously directly followed by 800 mg orally and subsequently 400 mg 3 times daily resulted in therapeutic plasma levels within 15 min. The plasma levels remained within the therapeutic range throughout a period of observation from 48 to 168 hr.

Administration, Oral↗
PubMed1976

The effect of intravenous digoxin on the occurrence of ventricular tachyarrhythmias in acute myocardial infarction in man.

Patients with acute myocardial infarction were allocated to two groups according to a double blind-system of radomization. The patients (n = 18) in one of the groups received digoxin intravenously as an injection of 0.01 mg. per kilogram of body weight during 10 minutes. The patients in the other group (n = 15) received saline and served as controls. A continuous ECG record was obtained from each patient during 1 hour preceding the administration of digoxin or saline and was continued for 3 hours following the injection. No antiarrhythmic treatment was given during the time of the study. Based on the continuous ECG, calculations were made of the relative incidence of patients with different types of ventricular tachyarrhythmias during the period of observation as well as the percentage of arrhythmia-containing 1 minute intervals observed during this period. There was no statistical difference between the incidence of ventricular tachyarrhythmias in the two groups in the 1 hour period preceding drug injection. The administration of digoxin and saline did not change the incidence of ventricular tachyarrhythmias and there was also no statistically significant difference between the two groups as regards the incidence of patients showing different types of ventricular tachyarrhythmias during the 3 hour period following drug administration, Considering the 1-minute intervals, those without any ventricular premature contractions were less in the digoxin group (92 per cent) than in the saline group (88 per cent; p less than 0.001). Serum levels of digoxin at the end of the observation period were well above what is considered the minimum therapeutic level and in three patients the level approached or reached the toxic range. In these three patients there was still no increased incidence of ventricular tachyarrhythmias. It is concluded that patients with acute myocardial infarction complicated by incipient left ventricular failure do not show an increased sensitivity to an ordinary dose of digoxin as measured by the occurrence of ventricular tachyarrhythmia.

Acute Disease↗
PubMed1976

Right atrial monophasic action potential and effective refractory periods in relation to physical training and maximal heart rate.

The monophasic action potential (MAP) and the effective refractory period (ERP) of the right atrium were determined in eight healthy volunteers before and after hard physical training. The duration and amplitude of the MAP increased in seven individuals after training. ERP showed no consistent changes. One possible explanation of the findings is an accumulation of intracellular potassium. The duration of the MAP was well correlated to maximal heart rate.

Action Potentials↗