Got rhythm? When heart rates go wrong
Atrial fibrillation is the most common arrhythmia to affect our health; recognize and treat the symptoms
Tom is my friend and occasional patient. He is 64 years old, works six out of seven days, smoked a pack of cigarettes a day for the past 50 years and drinks alcohol regularly in his off time. He has fair control of his hypertension but his last stress test was suspicious for coronary artery disease.
A few weeks ago Tom got up in the middle of the night and “didn’t feel right.” He felt lightheaded for a bit and thought his chest felt “funny.”
Never one to get overexcited about things, he sat there for a while, had a smoke, but when things didn’t get better, he woke his wife and asked her to drive him to the hospital.
She sat up and turned on the light. After her eyes adjusted and she was able to see him clearly, she informed Tom she would call him an ambulance and let them drive him to the hospital.
On EMS arrival the patient was awake, oriented and appeared anxious. He denied chest pain, lightheadedness or dizziness. His skin was pale and moist.
His pulse was rapid and irregular, with a blood pressure hard to obtain, but his radial pulse was palpable. The O2 sat was 94 percent, the lungs were clear, heart sounds were irregular and extremity edema was absent.
On the EMT’s "sick, not sick" scale, he was sick but stable at the moment.
Their assessment was “symptomatic rapid, irregular heart rate, probable atrial fibrillation.” The patient was transported with no change in symptoms or vital signs.
A rhythm is a repeating pattern, and for the healthy heart that means a regularly repeating electrical action that normally produces a regularly repeating heart contraction and pulse. The terms arrhythmia and dysrhythmia are used to identify any alteration in the heart’s normal electrical rhythm.
Atrial fibrillation (AF or Afib) is the most common arrhythmia to affect our health and it comes in three basic patterns as described on the AHA website:
- Paroxysmal fibrillation is when the heart returns to a normal rhythm on its own. People who have this type of AF may have episodes only a few times a year or their symptoms may occur every day. These symptoms are very unpredictable and often can turn into a permanent form of atrial fibrillation.
- Persistent AF is defined as an irregular rhythm that lasts for longer than 48 hours. This type of AF will not return to normal sinus rhythm on its own and will require some form of treatment.
- Permanent AF occurs when the condition lasts indefinitely and can no longer be controlled with medication.
The EMTs were correct as Tom did have atrial fibrillation, and why not; he had many of the high-risk factors: age over 60, smoker, drinker, hypertension and heart disease. However AF can develop at a younger age and/or due to other health problems such as hyperthyroidism, a condition of excess energy regulating hormones.
The EMTs were able to suspect Afib simply by taking a pulse and listening to the heart sounds. If cardiac monitoring was available, they could have confirmed their clinical impression with the typical image of an irregular R-to-R interval and no identifiable P waves.
If there are waves between the R-to-R intervals in AF, sometimes referred to as F waves, they will have an irregular shape and pattern unlike a normal P wave. Afib can be difficult to identify on a rhythm strip and physical exam if the rate is so fast that the R-to-R interval and pulse are too close together to determine an irregular rhythm.
The AF patient’s clinical presentation will depend on the patient’s heart rate, heart function and underlying health problems, and may range from no symptoms to no pulse.
You’ve heard it before: cardiac output equals heart rate times stroke volume. Cardiac output determines our circulating perfusion pressure and is measured by taking a blood pressure.
In AF, this process is attacked on two fronts. Normally the atria delivers 80 percent of its cargo to the ventricles simply by opening the valves that separate them, and then delivers the remainder when the atria contract.
If the atria are fibrillating they can’t deliver that 20 percent, and for some patients this loss of stroke volume causes a low blood pressure. Secondly, AF may cause the ventricles to contract too fast to fill adequately, which also may decrease stroke volume and blood pressure.
Field treatment is supportive unless the AF causes a rapid ventricular response that produces serious signs or symptoms such as hypotension, chest pain, or syncope, which may require cardioversion if available.
Some EMS systems may also use rate-controlling medication such as calcium channel blockers or beta blockers, or a rhythm-controlling medication like amiodarone. Patients with a history of Afib may already be on one or more of these medications.
Most patients with AF will be on drugs that block the formation of blood clots in those quivering atria to prevent stroke. It may be an anticoagulant like warfarin (Coumadin) or one of the newer ones: dabigatran (Pradaxa), rivaroxaban (Xarelto) or apixaban.
Or they may be on platelet inhibitors like aspirin and/or clopidogrel (Plavix). Be aware of the potential bleeding complications from these medications.
AF unresponsive to drug therapy may require procedures to burn out (ablate) those areas inside the heart that are generating the erratic electricity. Severe cases may necessitate the total destruction of the AV node to prevent any atrial impulses from reaching the ventricles, thus leaving the patient totally dependent on an implanted pacemaker.
Tom survived and is taking a beta blocker and warfarin and, as expected, was told to quit smoking and drinking. He was concerned they might also tell him to decrease his coffee intake at 12 to 14 cups per day.
Luckily, a recent analysis of several studies shows no causal relationship between caffeine and AF; in fact caffeine may actually help prevent AF4. Good thing for those of us who spend part of our working hours while most folks are asleep — that is unless they happen to be one of our patients like Tom.
1. What are the Symptoms of Atrial Fibrillation (AFib or AF)? Available at http://www.heart.org/HEARTORG/Conditions/Arrhythmia/AboutArrhythmia/What-are-the-Symptoms-of-Atrial-Fibrillation-AFib-or-AF_UCM_423777_Article.jsp# Accessed December 1, 2013
2. Management of Patients With Atrial Fibrillation (Compilation of 2006 ACCF/AHA/ESC and 2011 ACCF/AHA/HRS Recommendations): A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines Circulation. 2013;127:1916-1926. Available at http://circ.ahajournals.org/content/127/18/1916.full.pdf+html Accessed December 15, 2013
3. Gonsalves WI, Pruthi RK, Patnaik MM. The New Oral Anticoagulants in Clinical Practice
Mayo Clin Proc. 2013;88(5):495-511. Available at http://download.journals.elsevierhealth.com/pdfs/journals/0025-6196/PIIS002561961300222X.pdf Accessed January 2, 2014
4. Cheng M, Hu Z, Lu X, Huang J, Gu D. Caffeine intake and atrial fibrillation incidence: Dose response Meta-analysis of prospective cohort studies. Available at http://www.onlinecjc.ca/article/S0828-282X(13)01761-3/abstract Accessed December 27, 2013
- Patient Assessment