Dizziness, shortness of breath, mental confusion, or loss of consciousness may occur with atrial fibrillation if the ventricular response is too rapid or too slow. Bradyarrhythmias are slow heart rates defined as having a rate less than sixty beats per minute. Athletes and other aerobically fit individuals may commonly have heart rates in the 40-60 beats per minute range and experience no symptoms whatsoever. They are noteworthy in that, should further damage occur to the heart's conduction system, impulses meant to generate a heartbeat might not be conducted, with a dangerously slow heart rate resulting. The placement of a permanent pacemaker may be required, especially in the setting of a high-grade AV block, which produces a symptomatic bradyarrhythmia.
Examples are vasovagal syncope and carotid sinus syncope.
Vasovagal syncope is the most common cause of a common faint, which may be precipitated by prolonged standing, anxiety, hot environments, receiving an injection, etc. Neurally mediated syndromes become a significant problem if they become frequent, occur without warning, and result in near or total loss of consciousness. A history of more than six PVCs per minute present on a resting EKG, or if the PVCs are causing symptoms. The airman should receive a complete cardiovascular evaluation, a 24-hour Holter monitor test, and maximal Bruce Protocol stress test. If no cardiac disease is found, medical certification may be granted.