Vignette 1:
Compiled by Giuditta Angelini, M.D.

A 70 year old man presents for urgent femoral exploration secondary to a cold leg. He has a history of diastolic dysfunction and paroxysmal arrhythmia. No known lung, liver, renal or carotid disease. Preoperatively, blood pressure is 150/90, pulse 70. During the case, he develops an irregularly irregular rhythm with a narrow QRS at a rate of 190 and a blood pressure of 70/30.
Click the "A" button to see the answer for each question.

•  What is his arrhythmia?
•  What should you do?
•  What is his arrhythmia if his QRS is wide?
•  What should you do then?

Change the case so that his blood pressure is 110/60. QRS is narrow.

•  What should you do?
•  What if his QRS is wide?

Change the case so that his blood pressure is 110/60, QRS is narrow, but he has an ejection fraction of 20%.

•  What should you do?
•  What if his QRS is wide?

Change the case to 30 year old with no known heart disease except a delta wave on preoperative EKG. Pulse 190 and blood pressure is 100/60.

•  What should you do?

Discussion

Atrial fibrillation can be treated with drugs to terminate the arrhythmia directly or to control the rate and allow conversion to occur naturally. Digoxin, beta blockers, and calcium channel blockers are all active at the atrioventricular node and serve mostly to slow a rapid ventricular rate which can lessen symptoms and possible complications. Conversion occurs more as a secondary effect. Amiodarone, however, can actually terminate the arrhythmia. A number of other, less familiar drugs can be used to terminate the arrhythmia. Ibutilide is a drug which can be utilized to terminate atrial fibrillation, but it has a significant proarrhythmic effect which limits use. Sotalol is a beta blocker which has some membrane activity and can also can be used to terminate atrial fibrillation. Flecainide and propafenone are used as well, but should not be used in patients with coronary artery disease as they have been shown to increase mortality in these patients. Generally, cardioversion is the most likely of these treatment options to be available in the operating room if immediate conversion to sinus rhythm is indicated. Cardioversion is the first step in any unstable patient who is not in sinus rhythm.

Wide QRS should be considered to be ventricular tachycardia in most situations, especially if a patient has a known cardiac disease history. However, it can also be a manifestation of atrial fibrillation which produces a wide QRS because of aberrant conduction through the ventricles. If time and access allows, an electrocardiogram can be used to help distinguish the two. This is based on a set of rules known as Brugada’s criteria for which the reference is listed below.

Generally, electrolytes should be evaluated in addition to treatment for the arrhythmia–especially magnesium and potassium. Every effort to minimize hemodynamic instability should also be addressed–fluids, immediate treatment, etc.–as hypotension may eventually cause ischemia with the potential for more arrhythmias. Phenylephrine is the drug to use if a vasoconstrictive agent is required to increase blood pressure. Other agents, such as dopamine, may exacerbate the arrhythmia. However, patients with systolic dysfunction (low ejection fraction) may not tolerate additional afterload and prudent treatment may just be converting the arrhythmia. Beta blockers are beginning to be efficacious in patients with congestive heart failure from systolic dysfunction, but not during an acute decompensation. Even stable outpatients usually have at least a month where symptoms may worsen on beta blockers before the sympatholysis improves their function. Congestive heart failure secondary to diastolic dysfunction is usually secondary to thick myocardium. Medications, such as beta blockers and calcium channel blockers, which slow heart rate to allow more time for diastole and provide some negative inotropy for better relaxation are very efficacious in diastolic dysfunction.

While rare, knowledge of Wolff-Parkinson-White syndrome (WPW) is important. Most agents like digoxin, calcium channel blockers, beta blockers, and amiodarone have some amount of blocking effect at the AV node. In a patient with an accessory pathway connecting the atria and ventricles, these drugs can force even more conduction down the accessory pathway and cause the patient to become hemodynamically unstable. Procainamide would be the drug of choice in a patient having atrial fibrillation with WPW. Eventually, ablation of the accessory pathway is the most efficacious treatment.

Check out this web site for more information on arrhythmias and other topics in cardiology: www.cardio-info.com/lnkhrtso.htm

Here are some references for more information.

• Jung F, DiMarco JP. Treatment strategies for atrial fibrillation. American Journal of Medicine, 1998; 104(3):272-286.
• Narayan SM, Cain ME, Smith JM. Atrial fibrillation. Lancet, 1997; 350(9082):943-950.
• Ganz LI, Friedman PL. Supraventricular tachycardia. New England Journal of Medicine, 1995; 332(3):162-173.
• Ommen SR, Odell JA, Stanton MS. Atrial arrhythmias after cardiothoracic surgery. New England Journal of Medicine, 1997; 336(20):1429-1434.
• Murray KT. Ibutilide. Circulation, 1998; 97(5):493-497.
• Abraham WT. Beta-blockers: the new standard therapy for mild heart failure. Archives of Internal Medicine, 2000; 160(9):1237-1247.
• Brugada P, Brugada J, Andries E. A new approach to the differential diagnosis of a regular tachycardia with a wide QRS. Circulation, 1991; 83:1649-1659.