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Biomedical subjects

E Varnauskas

Publications and source records attributed to E Varnauskas.

At least 37 records · Page 2Linked to original sources
PubMed1982

Computerized exercise ECG in the diagnosis of critical coronary lesions.

Different ECG criteria are evaluated with respect to their ability to identify individuals with critical lesions of the coronary arteries in a population of patients with severe angina. Six chest leads and the the limb leads were recorded in 85 patients by computer during maximal, symptom-limited exercise ECG testing. Averaging of ECG complexes enhances the signal quality and makes it possible to use measurements of the limb leads recorded during exercise. 14 patients with abnormal Q waves in lead V2 were excluded from ST analysis. In the remaining 71 patients, more than 1/3 mm ST depression in lead I and/or more than 2.0 mm ST depression in any of the chest leads had a sensitivity of 85% and a specificity of 67% for lesions in the main stem and/or proximal LAD and/or three-vessel disease. The predictive value of a positive test was 83%. This and other criteria were evaluated for different disease groups and a different stages during the exercise test.

Adult↗
PubMed1979

Effect of mexiletine on monophasic action potentials recorded from the right ventricle in man.

The effect of mexiletine, a new antiarrhythmic agent, on ventricular refractoriness and monophasic action potentials recorded from the right ventricle was studied in nine subjects. The effective refractory period of the right ventricle was determined by the extra stimulus technique using a pacing electrode situated at the right ventricular apex. Following this determination the right ventricular apex was paced at a constant cycle length and premature stimuli were introduced starting at a coupling interval of 2 ms greater than the ventricular refractory period and then at progressively increasing coupling intervals of 5 ms increments. Simultaneous recordings of monophasic action potentials of both the regular paced beats and the induced premature beats were made using a specially designed suction electrode catheter. The monophasic action potential durations were measured at 50% and 90% repolarisation. All these control measurements were repeated after an intravenous dose of 2 mg.kg-1 body wt. of mexiletine. The results showed that mexiletine did not significantly change the effective ventricular refractory period nor did it alter the monophasic action potential duration of the regular paced beat. The drug did, however, significantly prolong the monophasic action potential duration of the early induced premature beats and it is possible that this property of the drug may be related to its antiarrhythmic activity.

Action Potentials↗
PubMed1977

The effect of mexiletine on the electrophysical properties of the intact human heart.

The effect of an intravenous dose of mexiletine, a new anti-arrhythmic agent, on the electrophysiological properties of the intact human heart was studied in ten subjects with no evidence of cardiovascular disease. Mexiletine produced no significant changes in the sinus node recovery time, the corrected sinus node recovery time or in the atrial, atrio-ventricular and ventricular effective refractory periods. In addition mexiletine had no significant effect on proximal atrioventricular conduction. The drug did, however, prolong atrio-ventricular conduction distal to the bundle of His in all ten subjects by an average of 6 msec. This change was statistically significant (P less than 0.01). The drug is recommended to be used with caution in patients with conduction disturbances.

Adult↗
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↗
PubMed1975

Effect of chronic beta-adrenergic receptor blockade in congestive cardiomyopathy.

Adrenergic beta-blocking agents were given to 7 patients with advanced congestive cardiomyopathy who had tachycardia at rest (98 plus or minus 13 beats/min). The patients were on beta-adrenergic receptor blockade for 2 to 12 months (average 5-4 months). One patient was given alprenolol 50 mg twice daily and the other patients were given practolol 50 to 400 mg twice daily. Virus infection had occurred in 6 of the patients before the onset of symptoms of cardiac disease. All patients were in a steady state or were progressively deteriorating at the start of beta-adrenergic receptor blockade. Conventional treatment with digitalis and diuretics was unaltered or reduced during treatment with beta-blocking agents. An improvement was seen in their clinical condition shortly after administration of the drugs. Continued treatment resulted in an increase in physical working capacity and a reduction of heart size. Noninvasive investigations including phonocardiogram, carotid pulse curve, apex cardiogram, and echocardiogram showed improved ventricular function in all cases. The present study indicates that adrenergic beta-blocking agents can improve heart function in at lease some patients with congestive cardiomyopathy. Furthermore, it is suggested that increased catecholamine activity may be an important factor for the development of this disease, as has been shown in animal experiments.

Adult↗
PubMed1975

Coronary arterial mapping in hypertrophic cardiomyopathy.

The diameters of the coronary arteries and their peripheral branches were measured on coronary angiograms obtained from 9 patients with hypertrophic obstructive cardiomyopathy (HOCM), 6 patients with hypertrophic non-obstructive cardiomyopathy, and 6 normal controls. There was a marked increase in the diameters of the main coronary arteries in the patients suffering from cardiomyopathy but no significant difference in the peripheral branches between the three groups. This discrepancy between the 'run-in' and 'run-off' components of coronary circulation could explain anginal symptoms during exercise in HOCM, but in the absence of direct coronary flow measurements this theory remains to be tested. HOCM was associated with the widest arteries whereas hypertrophic non-obstructive cardiomyopathy occupied an intermediate position between HOCM and the control group.

Cardiac Catheterization↗