Evaluation of Suspected Cardiac Arrhythmia

Excerpt

The different clinical presentations of cardiac arrhythmias reflect either reduced blood pressure or cardiac output, or both, as a direct result of the rhythm abnormality. Unlike most chronic diseases, hypertension, for example, rhythm disorders frequently behave intermittently, in an all-or-none fashion, chronic persistent or permanent atrial fibrillation being the major exception.

The impact of an arrhythmia is usually only evident during the arrhythmia. Symptoms of arrhythmia could be most pronounced at the onset or the termination of an intermittent arrhythmia. While an underlying chronic disease may be continuously present, any arrhythmia caused by it usually emerges entirely randomly and unpredictably.

Although symptoms and their severity vary considerably, the consequence of a rhythm disturbance tends to be rather binary: nuisance or death. For patient safety, our strategy should focus initially on the latter. Fortunately, the majority of arrhythmias fall within the nuisance category. Atrial fibrillation remains the exception: it can be present continuously, and significant consequences lie between nuisance and death, such as stroke and heart failure.

The approach outlined here is a suggested one. The very first encounter with an arrhythmia patient could be someone handing you a rhythm strip wherein no clinical information is available. We should keep three goals in mind while approaching a patient with suspected arrhythmia. Once completed, we can initiate a treatment strategy.

1. Establish probable cause that an arrhythmia exists

2. Determine whether there may be a risk of dying

3. Document the arrhythmia

Establishing probable cause refers to the likelihood that an arrhythmia exists and is based mainly on symptoms. A risk assessment is undertaken if there is a reasonable concern that death may be an outcome because of a personal history of structural heart disease, a family history of sudden death, or, in the case of primary arrhythmia syndromes, unique ECG abnormalities. An asymptomatic arrhythmia should not preclude the need for a risk assessment.

Making the diagnosis means documenting the arrhythmia and, in particular, linking it to the patient's symptoms via some form of ambulatory monitoring. Alternatively, one can pursue an electrophysiology study (EPS) to elicit or provoke a sustained arrhythmia if it doesn't occur spontaneously and is felt to place the patient at risk. The EPS may be the only means to discover abnormalities in the conduction system, such as a prolonged HV interval, that would never be obvious from an ECG tracing. Such findings are usually associated with bradyarrhythmias.