Abstract & Commentary
Synopsis: The risk of new AF or HF in subjects older than 65 with echocardiographic evidence of abnormal relaxation increased linearly with the degree of LA enlargement.
Source: Tsang TS, et al. Am J Cardiol. 2004;93:54-58.
Although echo doppler mitral inflow velocity evidence of "abnormal relaxation" is frequent in otherwise healthy older adults, recent observations suggest that mild diastolic function abnormalities may be associated with an increased mortality risk. Thus, Tsang and colleagues from the Mayo Clinic in Rochester, Minn, identified a cohort of local patients older than 65 with abnormal left ventricular (LV) relaxation from their echocardiographic database for follow-up chart review. Abnormal LV relaxation was defined as a mitral inflow velocity E/A wave ratio of < 0.75 or an E deceleration time of > 240 msec. Patients were excluded if they were not in sinus rhythm or had a history of heart failure, valvular heart disease, or stroke. Of the 717 subjects selected, 569 had abnormal relaxation and 148 controls had normal LV relaxation. The primary end point was a combination of first documented atrial fibrillation (AF) or heart failure (HF). Of the 569 subjects with abnormal relaxation, 105 (18%) developed the primary end point over a mean follow-up period of 4 years. Multivariate analysis showed that age, history of myocardial infarction, diabetes, ECG LV hypertrophy, and enlarged left atrial (LA) volume index were independent predictors of achieving the primary end point. A stepwise increase in age-adjusted risk was related to tertiles of LA size (< 27 mL/m2; 27-37, and > 37). The risk of achieving the primary end point was not different between the controls and those with abnormal relaxation and an LA volume of < 27 mL/m2. Tsang et al concluded that the risk of new AF or HF in subjects older than 65 with echocardiographic evidence of abnormal relaxation increased linearly with the degree of LA enlargement.
Comment by Michael H. Crawford, MD
Mild abnormalities in echo Doppler measures of diastolic function are so common in individuals older than 65 years and especially in those older than 75 that some echocardiographers do not ever comment on these findings because of a perceived lack of specificity for predicting future cardiac events. This study confirms some of these concerns in that more than half of their referral population had abnormal relaxation, and it was not particularly specific for predicting AF and HF. The presence of obvious clinical risk factors for these cardiac end points augmented the predictive value, but these variables are predictive of events in their own right. The most important finding was that LA size in the upper 2 tertiles really helped separate those with abnormal relaxation at higher risk of AF and HF from those at a risk equivalent to the normal diastolic function controls. Presumably as the LV stiffens, LA emptying is impaired, prolonging E velocity deceleration and augmenting A velocity. At this stage, the risk of events is not increased, but as the LA enlarges, the risk of cardiac events increases to beyond that of those with normal LV relaxation.
Thus, accurate measurements of LA volume indexed for body size need to be part of almost every echo examination. In my experience, too many labs are still relying on M-mode measures of LA dimension, which are known to be inaccurate in estimating LA volume.
Dr. Crawford, Professor of Medicine, Associate Chief of Cardiology for Clinical Programs University of California San Francisco, is Editor of Clinical Cardiology Alert.