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Sixty cases of atrial fibrillation from the USAF flying population are reported. Follow-up information in 59 subjects averaged 41.2 months. Only three cases of persistent atrial fibrillation were detected and two of these had normal sinus rhythm prior to the onset of atrial fibrillation. There were 21 cases of recurrent paroxysmal atrial fibrillation and 36 cases of isolated acute atrial fibrillation associated with a variety of precipitating factors. Thyrotoxicosis was notable by its absence in any of these cases of atrial fibrillation. Symptomatology either related to the primary disorder precipitating atrial fibrillation or secondary to the arrhythmia itself was frequently observed. The hemodynamic effects of atrial fibrillation on cardiac output, and cerebral artery spasm with diminished cerebral blood flow are important aeromedical considerations.

1. 1. This sensitive new in vitro technic for measuring “clearing activities” in plasma revealed highly significant differences between the fasting plasma samples from 15 patients with prior myocardial infarction (5.5 with standard error ±0.5 units) and those from 14 controls (9.2 ± 0.9 units). By t-test analysis p = 2. 2. This new technic was used to study the clearing activities of serial plasma samples from both patients and controls during cream-induced lipemia. Each subject remained remarkably stable. The 15 patients averaged 5.1 ± 0.46 units and the 14 controls averaged 9.6 ± 1.0 units. 3. 3. A consistent and significant rise in measured clearing activities followed intravenously given heparin (50 mg.) in every subject during an identical feeding of cream. The 15 patients' plasma reached 13.9 ± 1.7 units at two hours and the 14 controls' plasma reached 21.2 ±2.5 units at one hour. 4. 4. Evidence was presented that neither the clearing activities nor any associated inhibitor(s) were selectively bound to the surface of the fat. 5. 5. Simultaneous optical density and oral triolein-I131 absorption curves supported the findings of other workers.

Two cases of coronary artery heart disease are presented in which the Master two-step exercise test provoked short bursts of paroxysmal tachycardia. In one patient, nodal tachycardia was present; in the other, the tachycardia was either ventricular or nodal with aberrant conduction. Difficulties in assessing the probable etiology of paroxysmal tachycardia after exercise, which appears as an isolated finding in the coronary age group, are discussed.