Left atrial enlargement is a term commonly used to describe the process of left atrial dilating in patients with congenital heart disease (CHD). CHDs are genetic conditions and left atrial enlargement is one of the more common symptoms. It is the consequence of the congenital pumping dysfunction of the atria that leads to left atrial enlargement of the heart (which is medically termed as atrial flutter) and is thus a life-threatening condition. Left atrial flutter may result from congenital or genetic causes and can potentially lead to the development of heart disease (ischemia/myocardial infarction).
The term left atrial enlargement (also known as mitral regurgitation) was first described by Max von Hagge in 1872 after a patient with cardiomyopathy presented with symptoms consistent with atrial flutter. The average age of this patient was 17 years. He was found to have a left atrial curve with an enlarged right atrium with an irregular, decorated rhythm. He was classified as having progressive heart disease and was duly sent for surgical treatment. The surgical treatment failed to prolong life and the patient died of asphyxiation following a period of cardiac arrest.
It was not until recent years that the relevance of this relatively new term became apparent. It was found that a high percentage of patients with normal physiological acidity but who were classed as having hypertension had a normal or increased mitral valve function. The positive predictive value of this finding was that it pointed to the potential usefulness of left atrial enlargement in the treatment of patients with normal hypertension, provided that it could be applied in an early stage of the disease and before irreversible damage had occurred. The normal function of the mitral valve was therefore shown to have some predictive value in the prediction of hypertensive heart failure.
It has also recently been found that left atrial enlargement (lae) is associated with increased arterial pressure. As a consequence of this finding it has been postulated that left atrial enlargement may act as a mechanism by which arterial pressure can cause damage to the mitral valve. This damage would trigger the inactivity of this muscle, together with reduced cardiac output. As a consequence of this reduced cardiac output, a fall in blood pressure would occur and this would in turn lead to a decrease in heart tissue mass. The beneficial effect of reducing hypertension through the application of left atrial enlargement (law) has therefore been investigated.
Studies using fibrin gel have now shown conclusively that left atrial enlargement (law) can help to prevent the progression of coronary artery disease in patients with mild hypertension. Cardiologists have used echocardiography in conjunction with computerized tomography (CT) and magnetic resonance imaging to determine the extent of left atrial enlargement in patients with mild hypertension. The findings from these studies have shown that the intensity of left atrial enlargement is dependent on both the degree of systemic hypertension and the location of the largest vessel within the heart. The results from these studies have shown that patients with mild hypertension who were prescribed medication for controlling high blood pressure had a much smaller diameter than normal and this was associated with an increased risk of cardiac failure.
Surprisingly, research has also shown that patients with mild hypertension, but which are at increased risk of cardio-respiratory illness (CVR), will have an increase in the ratio of oxygenated blood to deoxygenated blood. This increased blood volume, coupled with an increase in cardiac output, will lead to an increase in the heart rate and heart failure. Although the exact mechanisms responsible for this phenomenon are not yet known, it appears that the mechanism is independent of the amount of left atrial enlargement, as coronary blood flow increases in individuals who have increased left atrial enlargement. This was further substantiated by research that showed an increased risk of sudden death in individuals with increased left atrial enlargement.
The most common consequence of left atrial enlargement is ventricular fibrillation or heart attack. Abnormalities in ventricular function may cause the heart muscle to become weak and is known as ventricular tachycardia. Such abnormal heart rhythms are commonly associated with the side-effects of certain medications that may be taken to control high blood pressure. Patients with ventricular fibrillation should be monitored carefully and patients whose heart rhythm is thought to be the main cause of the ventricular tachycardia should undergo a heart bypass procedure.
While there is a relationship between left atrial enlargement and cardiac health, patients should be aware of other potentially relevant risk factors. Smoking has been shown to reduce the effect of left atrial enlargement in some patients. Excessive alcohol consumption also appears to have some damaging effects on the heart and may lead to an increased risk of sudden cardiac death. It is therefore important for patients suffering from left atrial enlargement to abstain from alcohol consumption.