Atrial Fibrillation and the CMV Driver
By Mitchel Schwindt, M.D.
A 55 y.o. Male presents to the medical examiner for his Commercial Motor Vehicle (CMV) driver certification exam. His normal job description includes long haul driving across the country and occasional heavy lifting.
During the history portion of the exam he reports occasionally feeling some palpitations, especially after a poor night of sleep. He denies any chest pain or shortness of breath. In fact, he is feeling some palpitations at present, but denies any other symptoms or concerns. He takes no medications and has no history of any prior cardiac problems or stroke.
He does not smoke, drinks 3 cups of coffee a day and occasionally alcohol but none in the last 48 hours. His BP is 132/82 and his pulse is 110 and seems irregular on palpation of his radial pulse.
How do you proceed?
Atrial fibrillation (AF) is the most common cardiac arrhythmia and risk factors for developing AF include hypertension, coronary heart disease (CHD), Rheumatic heart disease, and advanced age. In the U.S., hypertension and coronary heart disease are the two most common underlying disorders in patients with AF. The Framingham study showed that patients with atrial fibrillation may be at increased risk for mortality (1.5-1.9X). Age is a risk factor for the development of AF. Data from the ATRIA study pointed out that the prevalence of AF was 0.1% in patients younger than 55, but increased to 9% for those over 80 years of age. Men are more often affected with AF than women.
CMV drivers are more at risk of obesity due to the sedentary nature of commercial driving and those with body mass index (BMI) greater than 30 are more likely to develop AF. In a study of 40,628 patients with hyperthyroidism 8.3 % had atrial fibrillation or flutter.
Patients may complain of palpitations, heart racing, dizziness, and shortness of breath or weakness. However, many patients will not report any symptoms or have symptoms that they do not related to the cardiovascular system.
History and physical examination
Perform a history and PE as per any patient presenting for CMV driver evaluation.
Focus the history on:
- Onset, frequency, duration and severity of symptoms
- Type of symptoms experienced such as palpitations, weakness, dizziness, etc.
- Presence of any severe symptoms such as chest pain, syncope or shortness of breath at rest
- Precipitation causes such as excessive caffeine, ETOH consumption, lack of sleep
- Presence of any other diseases that may confound or exacerbate atrial fibrillation (diabetes, thyroid disease, hypertension, COPD, ETOH abuse)
It is well documented in the medical literature that excessive ETOH consumption, including binge drinking, can precipitate an episode of atrial fibrillation. Up to 60% of binge drinkers with a structurally normal heart experience AF. Undiagnosed hyperthyroidism can also present as new onset AF. Caffeine due to its stimulant effects can also cause palpitations but there is no current evidence that caffeine provokes the onset of atrial fibrillation.
The physical exam will be completed in the same manner for all CMV driver exams. Document the pulse and blood pressure. Heart tones, presence or absence of murmurs, palpate peripheral pulses and listen to the lungs. The goal of the CV exam is to detect any abnormalities that may be attributable to the presence of atrial fibrillation, i.e.: rales on lung exam suggest congestive heart failure.
Whenever an abnormal pulse or heart rate is identified, an electrocardiogram (EKG) needs to be performed to evaluate further. Clinicians are at times surprised at what seemed like palpitations or premature ventricular contractions on auscultation actually turned out to be atrial fibrillation.
Classic EKG findings include an irregularly irregular RR interval and no distinct P waves. Also look for any signs of a more serious problem such as prolonged QT interval, ST or T wave changes suggesting ischemia or short PR intervals (pre-excitation). An examiner who is less familiar with the subtleties of EKG interpretation can consult a cardiologist for further interpretation.
The American College of Cardiology/American Heart Association classify AF into the following categories:
- First detected or diagnosed AF
- Paroxysmal AF
- Persistent AF
- Long-standing persistent AF
- Permanent AF
For informational purposes, paroxysmal AF is defined by 2 or more episodes that resolve spontaneously in 7 days or less. Paroxysmal AF often resolves in less than 24 hours. Persistent AF fails to self-resolve within 7 days and often requires drug or electrical therapy (cardioversion) to correct. Long-standing persistent AF has lasted for one year or more. The last category, permanent AF, defines a group of patients where efforts to control the rhythm are abandoned. These patients are managed with drug therapy aimed at controlling their heart rate.
Most often the patient’s primary care physician or cardiologist will order any necessary additional testing. Keep in mind that the purpose of the CMV driver exam is for certification and not to prescribe or manage specific disease processes.
Baseline lab tests include a complete blood count (CBC), basic metabolic panel (BMP) and thyroid stimulating hormone (TSH). These tests are useful to evaluate for underlying or contributing problems that may have an impact on atrial fibrillation.
A transthoracic echocardiogram (TTE) is used to evaluate the size of the various heart chambers, to detect valvular heart disease, and assess ejection fraction (EF).
A Holter monitor is a small monitoring device that provides information about a patient’s heart rate and rhythm over time. It can be useful in determining if the chosen therapy is providing effective control of the patient’s heart rate.
The primary care provider or cardiologist may order stress testing if concerns arise regarding the possible presence of ischemic heart disease. There are a variety of testing modalities available such as treadmill exercise testing, non-exercise imaging tests such as a dobutamine cardiolyte, CT scan utilization to detect coronary artery calcification and heart catheterization (invasive procedure).
You complete the history and exam. The only abnormality you note is mild obesity and an irregular mildly increased pulse. You order an EKG that shows Atrial Fibrillation with a ventricular rate varying from 95-135. Now what? What category of Atrial fibrillation does he fall into? What is he at risk for?
Read on to part II of Atrial Fibrillation and the CMV driver on 2/23/13.