A 66-year-old man comes to the office due to heart palpitations for the last 2 weeks. His medical history is significant for coronary artery disease, hypertension, and type 2 diabetes mellitus. Physical examination and ECG demonstrate an irregularly irregular rhythm. Which of the following anatomic sites is the most likely origin of this patient's arrhythmia?

Question

A 66-year-old man comes to the office due to heart palpitations for the last 2 weeks.  His medical history is significant for coronary artery disease, hypertension, and type 2 diabetes mellitus.  Physical examination and ECG demonstrate an irregularly irregular rhythm.  Which of the following anatomic sites is the most likely origin of this patient's arrhythmia?

Quizplus · Accepted Answer

This patient has atrial fibrillation (AF), one of the most common cardiac arrhythmias. The typical electrocardiogram (ECG) presentation of AF includes absent P waves replaced by tiny chaotic fibrillatory waves, irregularly irregular R-R intervals, and narrow QRS complexes. The pulmonary veins (PVs) are the most frequent location of the ectopic foci that cause AF. Cardiac tissue (myocardial sleeves) extends into the PVs and normally functions like a sphincter to reduce reflux of blood into the PVs during atrial systole. This tissue has different electrical properties than the surrounding atrial myocytes and is prone to ectopic electrical foci and/or aberrant conduction, which can initiate AF. fibrillatory waves Origination of AF in the PVs is therapeutically useful in patients who cannot achieve rate and/or rhythm control with standard medical therapy. In these patients, the myocardial tissue surrounding the PVs can be disrupted by catheter-based radiofrequency ablation, thereby electrically disconnecting the PVs from the left atrium. (Choice A) Patients with an accessory atrioventricular bypass tract, as seen in the Wolff-Parkinson-White (WPW) pre-excitation syndrome, may develop a reentrant loop conduction pattern and atrioventricular reentrant tachycardia (AVRT). Slurred upsloping R waves (delta waves) are characteristic of WPW syndrome. delta waves (Choice B) Atrioventricular nodal reentry tachycardia results from a reentrant circuit formed by 2 separate conducting pathways (one fast and the other slow) within the AV node. It is characterized by sudden onset and termination, rapid (140-250/min) regular rhythm, narrow QRS complexes, and absence of definite P waves. Atrioventricular nodal reentry tachycardia (Choice D) Sinus tachycardia is characterized by a sinoatrial (SA) node discharge rate of 100-180/min, regular R-R intervals, and normal P waves and QRS complexes. It is due to increased sympathetic and/or decreased vagal tone in response to physiologic (eg, exercise) or pathologic conditions (eg, fever, hypovolemia, thyrotoxicosis). Sinus tachycardia (Choice E) The most common cause of atrial flutter is a reentrant circuit around the tricuspid annulus, with slowing of the impulse through a region known as the cavotricuspid isthmus. Rapid "sawtooth" flutter waves are the characteristic ECG feature of atrial flutter. flutter waves Educational objective: Atrial fibrillation is most commonly caused by ectopic foci within the pulmonary veins. Atrial flutter commonly involves a reentrant circuit around the tricuspid annulus. Atrioventricular nodal reentry tachycardia results from a reentrant circuit formed by 2 separate conducting pathways within the AV node. References: The role of pulmonary veins in atrial fibrillation: a complex yet simple story. (http://www.ncbi.nlm.nih.gov/pubmed/19628005) Atrial fibrillation: a developmental point of view. (http://www.ncbi.nlm.nih.gov/pubmed/19726237)

A 66-Year-Old Man Comes to the Office Due to Heart