When the heart goes out of rhythm – II
In the last column, we discussed the symptoms of Atrial Fibrillation (A Fib), the commonest rhythm disorder encountered in clinical practice. Diagnosis of A Fib can be done from a combination of patient’s medical history, clinical findings and a few simple laboratory tests. Keep in mind that many patients may be asymptomatic and A Fib is detected during routine physical examination. The typical clinical finding is an irregular pulse as well as heart rate, the latter being higher than the pulse count (pulse deficit). An electrocardiogram (EKG) can easily diagnose the condition.
Because A Fib may come and go and the EKG can be normal during initial presentation, the patient will be asked to wear a portable EKG recorder called Holter monitor for 24 hours. This will pick up any episodes of irregular rhythm during the monitoring period and hence useful to detect paroxysmal (intermittent) A Fib. Sometimes, patient’s symptoms or irregularity occur less frequently and hence a cardiac event monitor is used. This is a battery-powered portable device that can record your EKG when you develop any symptoms such as palpitations, dizziness, feeling of irregular heart rhythm, etc. You need to push a button to record a strip of EKG as needed and it will reveal a change in the rhythm if any. The recording can then be sent by phone to your doctor or to a receiving center for an instant diagnosis. Sometimes, you have to wear the event monitor for four weeks.
Other tests would include a simple chest X-ray to see if there is any enlargement of the heart or evidence of heart failure. An ultrasound of the heart (Echocardiogram) is beneficial to assess the size of the cardiac chambers, abnormalities in the valves, blood flow patterns and overall function of the heart. In addition, if a clot is suspected in any cardiac chambers (often seen in the left atrium in A Fib), a special test called Transesophageal Echocardiogram will be done by passing a probe through the throat to get better images of the heart. Your doctor may also order a stress test to evaluate the performance of the heart and to detect the presence of coronary artery disease.
What causes A Fib?
Although A Fib can occur without any specific cause, there are many conditions that can contribute to this arrhythmia. They include:
1. Coronary heart disease, a common problem in the older age group contributing to oxygen deprivation from ischemia of the cardiac muscle, including atrial wall.
2. Hypertension: Persistent significant hypertension can cause atrial dilatation and remodeling resulting in derangement of impulse conduction along the atrial wall.
3. Rheumatic heart disease especially Mitral Valve disease can contribute to A Fib but thankfully this is not common any more in the United States although common in other countries.
4. Pericarditis is an inflammation of the coverings of the heart and can occur after a viral infection. Other causes are bacterial and fungal infections as well as autoimmune diseases like lupus, rheumatoid arthritis, etc.
5. Hyperthyroidism, also known as overactive thyroid, will produce too much thyroid hormone that increases body metabolism, accelerates the heart rate and is a high risk for A Fib. When a patient presents with A Fib, one of the first tests we do is to measure the level of thyroid hormones in the blood.
6. Diabetes Mellitus can produce inflammation of the atria and is an independent risk factor for A Fib in addition to producing coronary artery disease. Studies have shown that women with Type 2 diabetes have almost twice the risk of developing A Fib than women without the chronic disease.
7. Obstructive Sleep Apnea (OSA) is a chronic disease that produces snoring, a common problem in middle aged and older as well as obese people. A Fib is only one of the complications of this disease. Sadly many individuals are unaware that they have OSA.
8. Cardiac stimulants. Caffeine present in coffee, tea, coca cola, energy drinks, etc., is the commonest culprit. Also, many over-the-counter cold and cough medicines that contain pseudoephedrine can stimulate the heart. Nicotine in tobacco products and recreational drugs like cocaine and amphetamines are notoriously strong stimulants.
9. Chronic Pulmonary Disease such as COPD, Emphysema and chronic bronchitis, often related to smoking, reduces the oxygen levels in the blood and contribute to A Fib.
10. Post-operative: Atrial Fibrillation complicates 25% to 40% of cardiac surgical procedures.
As you can see, there are many causes for A Fib and treatment will involve not only controlling the rhythm and rate of the heart but also correcting or modifying the many predisposing factors.
To be continued …