The Effect of Atrial Fibrillation Hemodynamics on Regulation of Cerebral Blood Flow

This is a prospective study evaluating 10 subjects referred for elective direct current cardioversion (DCCV) of atrial fibrillation. Subjects will be seen at Parkland Health and Hospital System. After full consent is obtained and explanation of the research, each subject will undergo a series of entirely non-invasive tests including Transcranial Doppler ultrasound (TCD), manual cuff blood pressure (BP), beat to beat BP monitoring by a Portapress monitor, and respiratory tidal CO2. These measurements will be taken after laying the patient in a supine position for 10 minutes and subsequently after standing for 10 minutes. Measurements will also be taken after full body squat -stand repetition at 20 second intervals (0.05 Hz) x 5 minutes. Patients who are unable to squat may rise from a seated position on a chair. This protocol has been easy to follow even for debilitated patients with Alzheimers Disease in Dr. Zhang and Dr. Levine's laboratory. The subject will then undergo elective DCCV as planned for standard of care. The above measurements and with respective body positions will then be repeated 30 minutes later if the patient has been successfully converted to normal sinus rhythm by DCCV. The experimental testing will take approximately 1 ½ to 2 hours to complete.