This patient has new onset atrial fibrillation; in atrial fibrillation the most likely site of origin for ectopic foci is the pulmonary veins.
Atrial fibrillation, the most common chronic arrhythmia, is a supraventicular arrhythmia that causes an irregularly irregular rhythm. Some risk factors include COPD, pulmonary embolism, chest surgery, myocardial ischemia, cardiomyopathy, pericarditis, hypertension, atrial septal defects, mitral or aortic valve abnormalities, atrial myxoma, hyperthyroidism, alcohol, and sepsis. Presentation can be asymptomatic, but common symptoms include dyspnea, palpitations, chest pain, or syncope. Hemodynamically stable patients should be rate-controlled with beta-blockers, diltiazem, or digoxin (in order of preference). If the patient has been in atrial fibrillation for less that 48 hours, cardioversion can be attempted without anticoagulation. If the arrhythmia had occurred for more than 48 hours or the duration is not known, anticoagulation should be achieved before cardioversion, unless left atrial thrombus has been ruled out by transeosophageal echocardiogram (TEE).
In a review of the diagnosis and management of atrial fibrillation, Gutierrez and Blanchard remind physicians that rate control is preferable to rhythm control, and rhythm control should only be used when rate control has failed. Although guidelines state a goal rate of 80bpm, recent data has shown that goal heart rates of less than 110 are non-inferior.
In chronic, uncontrolled atrial fibrillation, a single inciting ectopic focus can be the source. In a descriptive study of discrete radio-frequency ablation for the treatment of atrial fibrillation, Jai et al. found that this approach was curative in 9 out of 9 patients with a single inciting focus after 4±4 radiofrequency pulses.
Figure A shows an EKG of a patient in atrial fibrillation.
Answers 1 and 2: Although left and right atrium ectopic foci can cause atrial fibrillation, ectopic foci in the pulmonary veins are the most common. Of note, the tricuspid annulus is the most common site for atrial flutter.
Answers 4 and 5: Atrial fibrillation is a supraventricular tachycardia and by definition cannot originate in the ventricle.
Gutierrez C1, Blanchard DG. Atrial fibrillation: diagnosis and treatment. Am Fam Physician. 2011 Jan 1;83(1):61-8.
PMID:21888129 (Link to Abstract)
Jaïs P1, Haïssaguerre M, Shah DC, Chouairi S, Gencel L, Hocini M, Clémenty J. A focal source of atrial fibrillation treated by discrete radiofrequency ablation. Circulation. 1997 Feb 4;95(3):572-6.
PMID:9024141 (Link to Abstract)