Setting: ED
CC: “I feel a fluttering in my chest.”
VS: R: 32 breaths/minute; BP: 118/88 mm Hg; P:128 beats/minute, irregularly irregular; T: 98.1°F
HPI: A 42-year-old gastroenterologist comes to the office with 1 single day of palpitations and fluttering in his chest. He has never had this before. He denies chest pain, light-headedness, or shortness of breath. He is very anxious. He drinks a large amount of vodka at night four to five times a week and frequently travels to present papers at international meetings.
PMHX: none
Medications: none
Each part of the physical examination on CCS takes the same amount of time, no matter the case.
PE:
Neurological: normal
Cardiovascular: no murmurs, rubs, or gallops
Abdomen: normal
Extremities: no edema
Initial Orders:
ECG
CHEM-7
Chest x-ray
Oximeter
CBC
As you move the clock forward 10 to 20 minutes, all the laboratory results come back as normal except for the ECG. The ECG shows AFib at a rate of 125 to 130 beats/minute. The QRS duration is normal (Figure 1-5).
Figure 1-5. Atrial fibrillation. (Reproduced with permission from Tintinalli JE, et al. Tintinalli’s Emergency Medicine, A Comprehensive Study Guide, 7th ed. New York: McGraw-Hill; 2011.)
When is immediate electrical cardioversion for AFib correct?
a. Palpitations not improved with medication
b. Severe anxiety
c. Pallor, sweating, and decreased capillary refill
d. BP 78/50 mm Hg and chest pain
Answer d. BP 78/50 mm Hg and chest pain
Electrical cardioversion is indicated for tachyarrhythmias when there is life-threatening hemodynamic instability, such as chest pain, CHF caused by the arrhythmia, decreased systolic BP, or hemodynamically related confusion.
Although uncomfortable, none of the other symptoms described here are severe enough to put the patient through the risk and discomfort of electrical cardioversion. Pallor, anxiety, sweating, and palpitations are all subjective, hard to measure, and not life-threatening.
Cardioversion works by causing the simultaneous depolarization of all the myocytes in the heart.
What is the most common cause of AFib?
a. Caffeine
b. Cocaine
c. Hypertension
d. Hyperthyroidism
e. Ischemia (coronary disease)
Answer c. Hypertension
AFib occurs most commonly as a result of structural abnormalities of the heart caused by hypertension, cardiomyopathy, or valvular heart disease.
Although it is commonly believed that caffeine causes AFib, this has not been shown to be true. Caffeine and cocaine can speed up rate-controlled atrial arrhythmia, but it is unlikely that caffeine alone can cause AFib in a normal heart.
Hyperthyroidism can cause AFib, but it is a far less common cause than hypertensive heart disease. It is rare for ischemia or coronary disease to present with AFib in the absence of other structural heart disease.
The patient is uncomfortable from palpitations but is hemodynamically stable. What treatment is first?
a. Quinidine
b. Heparin
c. Warfarin
d. Metoprolol
e. Depends on results of the echocardiogram
Answer d. Metoprolol
Rate control with either a beta-blocker, CCB, or digoxin is the first step in managing rapid AFib. Rate control is more important than trying medications such as quinidine, amiodarone, flecainide, or propafenone to chemically convert AFib into normal sinus rhythm. Anticoagulation is not needed for AFib present for <48 hours. The echocardiogram results may help tell who needs anticoagulation, but controlling the rapid ventricular response is not dependent on echocardiogram findings.
What is the mechanism of rate control in AFib or flutter (Figure 1-6)?
Figure 1-6. Atrial flutter. (Reproduced with permission from Conrad Fischer.)
a. Inhibition of “Funny” sodium channels in the sinoatrial (SA) node
b. Stimulation of outward potassium channels
c. Inhibition of conduction in the AV node
d. Blocking Purkinje fibers
Answer c. Inhibition of conduction in the AV node
Any beta-blocker will work to slow AV nodal conduction in atrial arrhythmias. Only the CCBs diltiazem or verapamil slow conduction to control rapid rate.
Alcohol intoxication causes atrial fibrillation.
After metoprolol or diltiazem, the patient’s heart rate reduces to 80 beats/minute. All symptoms resolve. Admittance to the ICU is not necessary and the patient is placed on a regular hospital ward. Heparin is not necessary. The echocardiogram shows a normal heart size and shape with no significant valvular disease and no thrombi. The AFib does not stop, but the rate remains controlled and there are no symptoms.
What is the best therapy?
a. Aspirin
b. Warfarin
c. Dabigatran
d. Rivaroxaban
Answer a. Aspirin
CHADS is an acronym for risk factors for stroke in AFib. If the CHADS score is 0 or 1, aspirin alone is sufficient. If the CHADS score is 2 or more, use warfarin, dabigatran, or rivaroxaban.
C = Congestive heart failure
H = Hypertension
A = Age > 75 years
D = Diabetes
S = Stroke or transient ischemic attack (TIA) (Either of these alone is worth 2 points and indicates automatic anticoagulation medication.)
This patient has a CHADS score of zero, and aspirin alone is sufficient.
Dabigatran is a direct thrombin inhibitor. No INR monitoring is needed.
Rivaroxaban is a factor Xa inhibitor. No INR monitoring is needed.