Cross-sectional echocardiographic examination of the interatrial septum

The interatrial septum has not been readily appreciated by M-mode echocardiography. Cross-sectional echocardiography has the capability of recording the shape and location of the interatrial septum. Real-time cross-sectional echograms using a mechanically oscillating transducer were obtained on 100 consecutive patients. Echocardiographic examination of the left atrium and aorta was obtained in a plane perpendicular to the long axis of the atria. In 15 normal patients and 17 patients with atrial septal defects (ASD) and 51 patients with other forms of heart disease, the interatrial septum was recorded as a linear echo from the aorta to the posterior wall of the left atrium. In six patients who had ostium primum ASDs, the echoes from the interatrial septum disappeared near its expected junction with the interventricular septum. Drop out of echoes in the mid portion of the septum was noted in those patients who had ostium secundum atrial septal defects but this could not be differentiated from normal. These preliminary data indicate that examination of the interatrial septum is feasible and may be specific in those few patients examined so far with ostium primum atrial septal defect. The ability to locate and record the shape of the interatrial septum could have many investigate and clinical uses.

Analog computer assisted beat-by-beat measurement of stroke volume and related variables in man

A technique for the beat-by-beat measurement of stroke volume is described. Aortic blood velocity signals are obtained from a catheter-mounted electromagnetic velocity transducer and analysed by a purpose-built analog computer. The stroke volume is computed by integration of each period of systolic forward flow using the velocity signal as its sole input. Automatic compensation of flowmeter drift is incorporated and inappropriate triggering of integration by diastolic artefact is prevented by applying both amplitude and duration criteria for the recognition of systolic forward flow. Early diastolic reverse flow is excluded from integration. The cardiac output, mean aortic flow per beat, and interbeat interval are also computed from the velocity signal. With aortic pressure as an additional input signal the mean arterial pressure per beat and systemic vascular resistance can be computed. The computer outputs are calibrated by a manual method. Preliminary studies comparing values for the cardiac output measured by this system and the direct Fick technique have indicated an excellent correlation between the two methods.