cardiovascular disorders
Atrial Fibrillation
Diagnosis of Atrial Fibrillation
Electrocardiography (ECG) Echocardiography Thyroid function tests Diagnosis of atrial fibrillation is by ECG (see figure Atrial fibrillation ). Findings include Absence of P waves Presence of f (fibrillatory) waves between QRS complexes; f waves are irregular in timing, irregular in morphology; baseline undulations at rates>300/minute, usually best seen in lead V1 and not always apparent in all leads Irregularly irregular R-R intervals Other irregular rhythmsmay resemble atrial fibrillation on ECG but can be distinguished by the presence of discrete P or flutter waves, which can sometimes be made more visible with vagal maneuvers. Muscle tremor or electrical interference may resemble f waves, but the underlying rhythm is regular. Atrial fibrillation may also cause a phenomenon that mimics ventricular extrasystoles or ventricular tachycardia (Ashman phenomenon). This phenomenon typically occurs when a short R-R interval follows a long R-R interval; the longer interval lengthens the refractory period of the infra-Hisian conduction system, and the subsequent QRS complex(es) are conducted aberrantly, typically with right bundle branch morphology. Echocardiography and Echocardiography is done to assess structural heart defects (eg, left atrial enlargement, left ventricular wall motion abnormalities suggesting past or present ischemia, valvular disorders, cardiomyopathy) and to identify additional risk factors for stroke (eg, atrial blood stasis or thrombus, complex aortic plaque). Atrial thrombi are more likely in the atrial appendages, where they are best detected by transesophageal rather than transthoracic echocardiography. Atrial fibrillation with a wide QRS complex may indicate Atrial Fibrillation and Wolff-Parkinson-White Syndrome (WPW) ; in such cases, use of AV node-blocking medications may be fatal. 