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Quinidine-like immunoreactivity (Abbott TDx Quinidine fluorescence polarization immunoassay) was measured in control, sham-operated, abdominal aorta stenotic and hyperthyroid (thyroxine feeding 0.1 mg/rat/day rats. The mean quinidine levels (mumol quinidine/1 serum) were 0.07, 0.14, 0.13 and 0.25, respectively. The elevation in experimental hyperthyroidism was statistically (analysis of variance, Duncan's test) significant. The possibility of the existence of an endogenous antiarrhythmic, immunologically cross-reacting in quinidine immunoassay, is discussed.

In chronic heart failure, dysregulation of sympathetic nerve system activity and of release of several neurohormones is present. Increased plasma levels of circulating hormones together with other factors have a negative influence on myocardial beta adrenergic receptors and induce cardiac hypertrophy with myocardial fibrosis. ACE inhibitors possess an ability to reverse these phenomena. An endogenous factor with an ACE inhibitory ability was isolated from the bovine left ventricular myocardium.

A statistically highly significant correlation exists between the values of left ventricular end-diastolic pressure and the dimensions of the terminal segment of the P wave in the electrocardiographic V 1 lead. Values lower than -0.03 mmsec were found only in patients with pathologically elevated left ventricular end-diastolic pressure. In a group of 94 patients with acute transmural myocardial infarction, pathologically low values were found in 43% of the patients on the first day of the disease; on the fifth day of disease the frequency of pathological values of PTF---V 1 sank statistically significantly. A gradual decrease in the values of PTF---V 1 is a sign of bad prognosis in patients with acute myocardial infarction. Changes in the terminal segment of the P wave, at preserved sinus rhythm, can be read off any electrocardiographic curve. Their evaluation offers valuable information about changes in left ventricular end-diastolic pressure, when facilities for catheterization of the patient are not available. This possibility constitutes the main practical value of the method described.

In 108 patients on maintenance digoxin therapy the serum digoxin levels were determined by means of homogeneous enzymoimmunoanalysis and compared with those estimated by means of a commonly accepted nomogram and with those estimated by means of the equation derived from multiple regression analysis of variables. By using stepwise discriminant analysis and a jacknifed classification matrix, based on serum digoxin and potassium levels, 96% and 90% of the classification of patients with and without clinical signs of digoxin intoxication, respectively, was correct. Based on serum creatinine and potassium levels and the daily digoxin dose/kg only 83% and 78% of the classification, respectively, was correct. The direct determination of serum digoxin level provides, in real time, information of higher reliability than does the estimate of the serum digoxin level. It is of basic importance in patients with dysrhythmias, in persons with an implanted pacemaker and in persons in whom the estimated levels of serum digoxin are around 2.6 nmol/l.

Echocardiographic, electrocardiographic and roentgenologic examinations were performed in 50 patients with progressive polyarthritis without clinical signs of pericardial affection. At the same time, laboratory signs of the activity of the disease were evaluated. Using one-dimensional echocardiography, pericardial effusion was detected in 27 patients (54%). Neither valvular involvement nor specific changes in the myocardium were found. In the serum of patients with pericardial effusion the presence of the rheumatoid factor was statistically significantly more frequent than in patients without effusion. Patients with steroid therapy of the primary disease and a statistically significantly lower incidence of effusions than patients who were subjected to other forms of treatment. Echocardiography again proved to be the only sensitive non-invasive method capable of detecting small and medium-sized effusions.