Nm Wheeldon

Left atrial size and function: assessment using echocardiographic automatic boundary detection.

OBJECTIVE--To evaluate the waveforms of left atrial area changes obtained by automated boundary detection with newly developed acoustic quantification technology. DESIGN--All subjects had measurements of left atrial areas taken in the apical four chamber, parasternal long axis, and parasternal short axis views using both conventional echocardiographic methods and automatic boundary detection on two occasions separated by at least a week. On the second visit measurements were also repeated in healthy volunteers after acute intravenous volume loading with 1 litre of saline over 2-5 minutes. SETTING--A university medical school echocardiographic laboratory. SUBJECTS--12 healthy male volunteers and 8 patients with cardiac disease (5 with congestive heart failure, 1 with mitral stenosis, and 2 with hypertensive left ventricular hypertrophy, and dilated left atria). RESULTS--There was close correlation between conventionally derived left atrial areas and those obtained by automatic boundary detection, particularly in the apical four chamber view (r = 0.98). Both inter and intra observer variabilities (coefficient of variation) for left atrial areas measured by automatic boundary detection were good (4.7-14.2% and 8.1-18.6% respectively). The reproducibility (coefficient of variation) for derived indices of left atrial function, however, was much poorer (10.4-104.8% and 12.5-88% respectively). After acute volume loading significant increases in left atrial area were observed at all stages in the cardiac cycle. CONCLUSIONS--These data demonstrate that although the reproducibility of left atrial functional indices is poor, instantaneous left atrial cavity measurements with automatic boundary detection are reproducible. This suggests that automatic boundary detection may assist in serial non-invasive measurement of left atrial size to assess disease states and treatments.

Systolic and diastolic effects of beta-adrenergic stimulation in normal humans

Abstract We conclude that stimulation of β-adrenergic receptors with low-dose isoprenaline exerts greater effects on myocardial relaxation than contraction. This suggests that diastolic function is exquisitely sensitive to acute changes in sympathetic tone, a finding that may have relevance in the pathogenesis and treatment of disease states associated with impaired ventricular filling.