Evaluating the lifetime risk of atrial fibrillation

Data from the Framingham study provide yet more valuable prognostic information, this time related to the most common cardiac arrhythmia, atrial fibrillation. Dr. Lloyd-Jones estimates that the lifetime risk for developing atrial fibrillation is 1 in 4 for men and women aged 40 years and older. Furthermore, lifetime risks are high (1 in 6) even in the absence of cardiac substrate abnormalities such as antecedent heart failure or myocardial infarction.

Atrial fibrillation is one of the major health issues as the population ages, and this study now indicates that the risk can start at age 40, much younger than age 65, as previously thought. The major complication of atrial fibrillation is stroke with its devastating complications. Unfortunately, atrial fibrillation, like hypertension, is often unnoticed because the patient may be completely asymptomatic. In fact, atrial fibrillation often only comes to medical attention when a patient has another illness in which sympathetic stimulation (eg, as a result of infection, bleeding, ischemia) accelerates the ventricular response and the patient then feels palpitations.

In the Framingham study, atrial fibrillation was documented by review of history, physical examination, electrocardiogram (ECG), and laboratory tests evaluated every 2 to 4 years. Atrial fibrillation was diagnosed if paroxysmal or persistent atrial fibrillation or atrial flutter was diagnosed by the reviewing cardiologist.

It may be useful to define terms. Par­oxysmal indicates that the arrhythmia occurs and reverts spontaneously. Persistent indicates that intervention (pharmacologic or electrical cardioversion) is necessary to restore sinus rhythm. Permanent indicates that neither pharmacologic nor electrical cardioversion will restore sinus rhythm. Paroxysmal atrial fibrillation may last seconds to days and may be difficult to document unless the rhythm is documented fortuitously or if the patient is symptomatic.

In fact, the major limitation of this study is the way atrial fibrillation was documented. It is likely that the incidence documented was underestimated.

Holter monitors provide full disclosure for the 24 to 72 hours they are on the patient. Event recorders record the rhythm when activated. Insertable loop recorders record brady- or tachyarrhythmias, depending on the programming.

The advanced telemetry now available in pacemakers (PMs) and internal cardioverter defibrillators (ICDs) can document and store atrial and ventricular arrhythmias with a precision not previously envisioned. This technology represents a new gold standard. When patients have an electrode in both the atrium and ventricle, high rate rhythms and the relationship between each chamber can be documented.

When the PM or ICD is interrogated, episodes of atrial fibrillation can be reviewed, noting the rate, date, and duration of occurrence. Every physician who performs this analysis can be amazed by the demonstration of previously unrecognized atrial fibrillation in an otherwise asymptomatic patient. This new data may require further decision-making, specifically regarding the need for anticoagulation. Data cannot be ignored and intervention may prevent stroke.

Dr. Lloyd-Jones has provided im­portant new statistical information about the incidence of atrial fibrillation and its public health burden. The recommendations of the American Heart Association to screen for atrial fibrillation at patient visits should be followed. Taking the pulse and listening to the regularity of the heartbeat are integral parts of the physical examination. Irregularity should be documented by an ECG or rhythm strip. Furthermore, the stored telemetry of a PM or ICD should be interrogated in those patients with these implanted devices. When these easy steps are followed, some of the consequences of atrial fibrillation may be prevented.