Validation of two-dimensional methods for left atrial volume measurement: a comparison of echocardiography with cardiac computed tomography.

BACKGROUND: Left atrial volume (LAVol) is an important predictor of cardiovascular outcomes. Different formulas are applied to calculate LAVol using two-dimensional transthoracic echocardiography (2DTTE) with variable reference values. The objective of the study was to evaluate the accuracy of methods to calculate LAVol by 2DTTE or cardiac computed tomography (CT). METHODS AND RESULTS: Overall 177 consecutive patients who underwent both a 2DTTE and retrospective electrocardiogram (ECG)-gated coronary CT angiography (CTA) within 15 days were included for this study. LA volume measurements were calculated by 2DTTE and 2DCT using the biplane area-length, biplane Simpson's, prolate-ellipsoid-1 and prolate-ellipsoid-2 methods. These results were compared with those measured by CT using a volumetric method. There was very good correlation between the CT and echocardiographic measures for LAVol, but significant underestimation of the echocardiographic methods when compared to the reference standard (33.5%, 39.1%, 48.1%, and 53.2% for the biplane area-length, biplane Simpson's, prolate-ellipsoid-1, and prolate-ellipsoid-2 methods, respectively). The biplane area-length method using 2DTTE had the closest volume estimation of all echocardiographic methods to the reference standard (67.6 ± 25.5 mL vs. 106 ± 35.5 mL, r = 0.712). Similarly, the biplane area-length method using CT most accurately predicted LAVol (103.3 ± 36.0 mL, r = 0.965). CONCLUSIONS: Compared to CT, 2DTTE provides reasonable assessment of LAVol, although all measurement methods underestimate LAVol. For both 2DTTE and CT, the biplane area-length method appears to provide the most accurate 2D estimate of LAVol.

Determining patient prognosis using computed tomography coronary angiography.

In addition to demonstrating luminal narrowings, cardiac computed tomography angiography (CTA) has the ability to detect nonstenotic plaque, vessel wall calcification and can assess left ventricular function. CTA prognostic studies have considered these components individually and in combination to produce novel risk factor scores to help predict clinical outcomes. In this article, we will consider the utility of CTA to predict clinical risk by considering the evidence for luminal stenosis, plaque scores, plaque descriptors and models combining these elements. We will also discuss some of the emerging applications of CTA that will likely provide future prognostic data in coronary artery disease patients. Although initially described as an anatomical investigation to determine the presence of coronary disease, CTA is being explored as a tool for functional imaging and may soon provide a noninvasive technique of anatomical and functional assessment previously only possible by invasive methods.

Changes in the activity of a CpG neuron after the reinforcement of an operantly conditioned behavior in Lymnaea.

We have previously shown that the aerial respiratory behavior of the mollusk Lymnaea stagnalis can be operantly conditioned, and the central pattern generating (CPG) neurons underlying this behavior have been identified. As neural correlates of operant conditioning remain poorly defined in both vertebrates and invertebrates, we have used the Lymnaea respiratory CPG to investigate neuronal changes associated with the change in behavior after conditioning. After operant conditioning of the intact animals, semi-intact preparations were dissected, so that changes in the respiratory behavior (pneumostome openings) and underlying activity of the identified CPG neuron, right pedal dorsal 1 (RPeD1), could be monitored simultaneously. RPeD1 was studied because it initiates the rhythmic activity of the CPG and receives chemo-sensory input from the pneumostome area. Pneumostome openings and RPeD1 activity were monitored both before and after a reinforcing training stimulus applied to the open pneumostome of operantly conditioned and yoked control preparations. After presentation of the reinforcing stimulus, there was a significant reduction in both breathing behavior and RPeD1 activity in operant preparations but not in yoked and naïve controls. Furthermore these changes were only significant in the subgroup of operantly conditioned animals described as good learners and not in poor learners. These data strongly suggest that changes in RPeD1 activity may underlie the behavioral changes associated with the reinforcement of operant conditioning of the respiratory behavior.