Prolonged Atrial Fibrillation Research Articles

Effects of acetyl strophanthidin on duration of atrial fibrillation in the neurally-intact and blockaded dog.

Although the inotropic and dromotropic effects of cardiac glycosides in atrial fibrillation (AF) are well recognized, their action on AF itself is not clear. Accordingly, to determine whether cardiac glycosides prolong AF, the duration of electrically induced AF, atrioventricular conduction, and left ventricular function were assessed for 30 minutes before and for 30 minutes following intravenous administration of acetyl strophanthidin (AS), 20 micrograms/kg, in neurally intact, beta-blocked, and beta-blocked and vagotomized dogs. In the intact dog, AS, 20 micrograms/kg, increased peak dp/dt by 132 +/- 35 mmHg.sec-1, p less than 0.05, and slowed ventricular response by 16 +/- 7 min-1, p less than 0.05, but had a variable effect on AF duration. While the increased left ventricular peak dp/dt persisted for 15 minutes after AS, an increased duration of AF was evident only at 20 minutes, when the effects of AS on left ventricular (LV) inotropy were no longer apparent. Moreover, the subset of dogs that did not demonstrate prolongation of average duration of AF after AS had a greater increment of peak dp/dt than those that showed prolongation, 237 +/- 52 versus 53 +/- 31 mmHg.sec-1, p less than 0.05. An additional 20 micrograms/kg, which produced ventricular extrasystoles, prolonged AF duration when compared to both control and 30-minute measurements. Acetyl strophanthidin, 20 micrograms/kg, had a variable effect on duration of AF with beta-blockade but prolonged duration by 114 +/- 34%, p less than 0.05, with both vagotomy and beta-blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous Conversion of Long-standing Atrial Fibrillation

Spontaneous conversion to sinus rhythm after prolonged atrial fibrillation is uncommon, with only 11 recorded cases to our knowledge in the English language literature. We report four cases of spontaneous conversion to an organized atrial rhythm (either sinus rhythm or atrial tachycardia with block) after nine to 16 years of established atrial fibrillation. One case was due to a toxic reaction to digitalis. In the other three cases there was no apparent reason. M-mode and two-dimensional echocardiography in three patients showed an akinetic and noncontractile left atrium in each case. This lends support to an earlier hypothesis that complete fibrosis of the left atrium may be responsible for the conversion from atrial fibrillation.

Detection of Cardiac-Specific Creatine Kinase Isoenzyme in Sera with Normal or Slightly Increased Total Creatine Kinase Activity

We describe a spectrophotometric kinetic assay for detecting creatine kinase MB isoenzyme activity in the 1 to 10 U/liter range. The MB isoenzyme was isolated [Clin. Chem. 20, 36 (1974)] and assayed (Rosalki method) with an Abbott ABA-100. Good reproducibility was demonstrated for MB isoenzyme activities near 1 U/liter (CV = 2.6%). Sera with normal or slightly increased total creatine kinase activity were evaluated. Sera of 14 patients with acute myocardial infarction contained, per liter, 84 to 236 U of total creatine kinase activity and 4.6 to 28.0 U of isoenzyme MB activity; corresponding ranges for sera from healthy lab technicians and patients with noncardiac disease were 36 to 277 and 0 to 2.6 U. MB isoenzyme activity for infarction patients rose and fell sharply within three days after the infarction. Atypical time-course patterns, MB isoenzyme activity remaining abnormally great for five days, were observed in serum from patients with prolonged atrial fibrillation and congestive heart failure or cardiomyopathy; the BB isoenzyme (1 to 5 U/liter) was also detected in sera of such patients but was absent in sera from infarcation patients. Quantification of column-isolated MB by the assay described is rapid, easy, specific, and extremely sensitive for measuring MB in the 1 to 10 U/liter range.

Thyroid function in supraventricular tachycardias: turnover of intravenously infused I 131-labeled thyroxine and the red blood cell uptake of I 131-labeled 1-triiodothyronine.

ABSTRACT Thyroid function was studied in 28 euthyroid patients with paroxysmal or recent prolonged atrial fibrillation and in 11 patients with paroxysmal atrial tachycardia. The serum protein-bound iodine level, basal metabolic rate, and thyroidal I131 uptake were within normal limits. In 11 of these cases, the fate of intravenously administered I131-thyroxine was studied. The half-time of disappearance of plasma radioactivity following infusion of Il31-labe1ed thyroxine ranged from 4.1 to 6.8 days and averaged 5.74 days—significantly faster than the turnover in previous studies of euthyroid human subjects. The thyroxine distribution space ranged from 8.0 to 16.4 liters (average, 12.2 liters), in contrast to a range of 7 to 12 liters (average, 9.9 liters) in the control group. The daily degradation rate of thyroxine varied from 52 to 126 micrograms per day (average, 83.6) in the group under study but was only 36 to 61 micrograms in the control group. The two-hour in vitro red blood cell uptake of I131-tri...