Serial submaximal treadmill tests are often used to evaluate the efficacy of therapy in patients with atrial fibrillation. Since the response to serial tests can be influenced by a ‘learning phenomenon’, we performed maximal exercise tests on 9 patients (mean age 63 ± 4 years) with chronic atrial fibrillation. Points of analysis for the initial and follow-up treadmill exercise tests were 3 mph/0% grade, the gas exchange anaerobic threshold, and maximal exertion. Significant (p < 0.05) reductions in ventilation (l/min) and oxygen uptake (ml/kg/min) were observed on follow-up at a standard submaximal work load of 3.0 mph/0% grade and at the gas exchange anaerobic threshold. There was no significant alteration in these variables at maximal exertion. A reduction in heart rate was observed throughout exercise during the follow-up test with the most marked reduction (21 beats/min) occurring at 3.0 mph/0% grade. There were no differences in respiratory exchange ratio or systolic blood pressure at any point. The reduction in submaximal heart rate and gas exchange variables without a significant change in these variables at maximal exertion is consistent with a learning effect. Therefore, studies comparing consecutive submaximal exercise test responses in patients with atrial fibrillation can be misleading.
A 64-year-old man was evaluated for progressively worsening edema of the legs. He had jugular venous distention, an enlarged liver, pitting edema, no history of tuberculosis, and a negative skin test for tuberculosis. An electrocardiogram showed low-voltage and ectopic atrial tachycardia (Panel A). Catheterization of the right side of the heart showed diastolic equalization of the right atrial (RA) pressure, right ventricular (RV) pressure, pulmonary-artery (PA) pressure, and pulmonary-capillary wedge pressure (PCWP), indicated by the red line in Panel B. A chest film showed a thickened pericardium (arrows in Panel C). Computed tomographic scans of the heart showed a dilated superior vena cava (SVC), a normal aortic arch (AA) and descending aorta (DA) (Panel D), and a thickened pericardium (arrows in Panel E). There was also an increase in right atrial pressure on inspiration (Kussmaul's sign) (Panel F). Simultaneous catheterization of the right and left sides of the heart (Panel G) showed diastolic equalization of the left ventricular (LV) and right ventricular (RV) pressures. Constrictive pericarditis was diagnosed, and marked pericardial thickening (P) (arrows in Panel H) was evident during pericardial stripping. Histologic analysis of the thickened pericardium showed a dense collagenous matrix, but no cause was identified. The patient's edema decreased markedly after pericardial stripping.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.