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J Am Coll Cardiol, 2008; 51:515-516, doi:10.1016/j.jacc.2007.10.019 © 2008 by the American College of Cardiology Foundation |
* Division of Cardiology, Columbia University College of Physicians and Surgeons, St. Luke’s-Roosevelt Hospital Center, 1111 Amsterdam Avenue, New York, New York 10025 (Email: fchaudhr{at}chpnet.org).
Although American Society of Echocardiography recommends using LA volume for use in clinical trials, LA dimension is still the most commonly used measure in large multicenter clinical trials.
In the Cardiovascular Health Study of 5,888 men and women, LA dimension was a significant predictor of future heart failure after controlling for baseline risk factors (3). Similarly, in the Framingham Heart Study (4) and the SPAF (Stroke Prevention in Atrial Fibrillation) trial (5), LA dimension was related to strokes and death in the former and to thromboembolic events (e.g., strokes and transient ischemic attacks) in the latter. Even in the more recent trials like the LIFE (Losartan Intervention for Endpoint reduction in hypertension) trial, LA diameter/height predicted risk of cardiovascular events independent of other clinical risk factors in hypertensive patients with left ventricular hypertrophy (6). In our study we have shown that there was strong interobserver (interclass correlation [ICC] = 0.977) and intraobserver (ICC = 0.980) correlations for the measurement of LA dimension (7).
We have discussed the relative value of using LA size as a marker of diastolic function on the basis of prior studies—it reflects the chronicity and magnitude of the increased left ventricular filling pressure (8) and is thus a marker of the severity and duration of diastolic dysfunction (9). It has been suggested (10) that Doppler indexes of diastolic function reflect filling pressures at 1 point in time and hence LA size might be a better marker, because it represents the chronicity of diastolic function. Given this data from previous studies, we did not correct for Doppler indexes of diastolic dysfunction in the multivariate analysis.
With regard to the accuracy of visually estimated left ventricular ejection fraction, prior studies have shown strong correlation of visually estimated left ventricular ejection fraction with radionuclide angiography (11).
Finally, although we do agree that "enlarged left atrial dimension in the setting of a normal stress echocardiogram is of unclear significance, and would not, on its own, merit further invasive workup," it should be emphasized that, in the setting of a normal stress echocardiography study, patients with enlarged left atrium have 3.4 times the event rate of a normal LA size (0.5%/year vs. 1.7%/year). This might not merit further invasive workup. However, it does merit aggressive medical management of risk factors, because an event rate of 1.7%/year cannot be considered as benign as the same event rate in a mildly abnormal stress echocardiography study (wall motion score index 1.1 to 1.7) (12). Thus, we disagree with Dr. Farzaneh-Far and colleagues that LA size should not be incorporated into risk stratification. In echocardiography as in other imaging techniques, evaluating multiple parameters defines diagnostic and prognostic data more accurately. As stated in our article, "further studies using LA volumes are needed to elucidate the role of diastolic dysfunction in patients undergoing stress echocardiography and to further evolve the concept of diastolic stress echocardiography."
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