A Simple Test for Interatrial Communication

Atrial septal defect -is one of the commoner congenital heart lesions. Wood (1956) found it in 18% of 900 cases of congenital heart disease that he studied. A large proportion of patients with this defect remain symptom-free for many years, but the average age of those seen by Wood was 23 years, and 84.5% were under 40, which suggests that these individuals tend to die young. Therefore it is not surprising that methods for surgical closure of the defect have now been developed, and, although the operative risks are being reduced, the physician is faced with the problem of weighing the prognosis of the natural course of the disease against the hazards of surgical correction at the present time. However, the risks and inconveniences to the patient suspected of having an atrial septal defect often begin long before surgery is even contemplated; for clinical diagnosis from physical signs, electrocardiography, and chest x-ray examination are not absolutely reliable, and more or less elaborate and potentially hazardous investigations involving cardiac catheterization and angiocardiography are required before an accurate anatomical diagnosis can be made. These procedures are justified in patients with symptoms, but it would be a great convenience if a simple test were available that enabled the clinician to arrive at a firm diagnosis in the symptomless patient with atrial septal defect. The present paper describes such a test, which depends upon being able to alter the pressures within each atrium separately. This produces changes in pressure differential between the two chambers, which consequently. result in alterations of blood flow across any defect that may exist in the septum. As a result, alterations occur in oxygen saturation of the blood leaving the left atrium, and these can be detected by an oxymeter placed on the patient's ear. Methods Thirty-two patients have been studied. An oxymeter earpiece (Wood, 1950) was placed on the right ear and connected to a chopper amplifier similar to that described by Stott (1953), enabling percentage arterial oxygen saturation to be recorded continuously. The intrathoracic pressure was measured Oa a water-filled catheter placed in the cesophagus, connected to a Hansen capacitance manometer (Dornhorst and Leathart, 1952X, while the brachial artery