Left Atrial Size in Competitive Athletes
Abstract & Commentary
By Michael H. Crawford, MD Dr. Crawford is Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco and Editor of Clinical Cardiology Alert. Dr. Crawford is on the speaker's bureau for Pfizer.
Synopsis: Left atrial remodeling in competitive athletes may be regarded as a physiologic adaptation to exercise conditioning, largely without adverse clinical consequences.
Source: Pelliccia A, et al. Prevalence and Clinical Significance of Left Atrial Remodeling in Competitive Athletes. J Am Coll Cardiol. 2005;46:690-696.
Athletes are known to have enlarged cardiac chambers, but the relationship of athletic left atrial (LA) enlargement to atrial tachyarrhythmias is unclear. Thus, Pelliccia and colleagues studied 1777 highly trained athletes without known cardiac disease. Mean age was 24 years, and 71% were men. LA size was measured by 2-dimensionally guided M-mode echocardiography from the parasternal long axis view. An absolute diameter of 40 mm or more was used to define an enlarged LA, regardless of body size or sex. ECG evidence of LA enlargement was a P wave duration of 120 ms in lead I or II or an inverted P wave in V1 of at least 1 mm by 40 ms. Athletes with symptoms suggestive of arrhythmias had Holter monitoring, exercise ECG tests and, in some cases, electrophysiologic studies. Athletes with LA enlargement were allowed to con- tinue in their sport, but were followed for up to 10 years (mean 7).
Results: LA dimension (D) ranged from 22 to 50 mm (mean 35), and was greater in men (mean 37) than in women (mean 32, P < .001). In 20% of athletes, LAD was > 40 mm. Left ventricular diameters were 55 mm or more in 44%, and LV mass/body surface area was increased in 9%. Of the 1777 athletes, < 1% had symptomatic, ECG-documented atrial tachyarrhythmias; paroxysmal atrial fibrillation in 0.3 and other supraventricular tachycardias in 0.5%. No athlete had an embolic event. Of the 347 athletes with LA enlargement, 95% were men and they had larger hearts by all size measures. Only 9 of 347 with LA enlargement had LA abnormality on ECG. There was no relation between LA size and supraventricular arrhythmias. Pelliccia and colleagues concluded that in highly trained athletes, LA enlargement by echo is common (20%), but supraventricular arrhythmias are uncommon (< 1%) and unrelated to atrial size. Thus, LA enlargement is a physiologic adaptation to exercise training.
The concern over what is physiologic enlargement vs pathologic cardiac chamber enlargement in athletes continues, as evidenced by the impetus for this study, namely that LA enlargement as opposed to LV enlargement is detrimental in athletes. Part of the concern is that LA enlargement is less common, 20% in this study vs 44% with LV cavity enlargement. However, this large study clearly shows that LA enlargement is benign and is relat- ed to LV enlargement. Stepwise regression analysis showed that 50% of the observed LA enlargement could be explained by LV enlargement. Although not discussed in the paper, my guess is that most of the other 50% are factitious LA enlargement. In this large screening study, they used the simple, reproducible (93% concordance between readers in this study) M-mode echo dimension measurement, which has been used in many epidemiologic studies. However, we know that it is more accurate to use 2-dimensional echo LA area measurements from the apical 4-chamber view, which have been normalized to body surface area. Had this been done, my guess is that most of the other half of the increased LAD measures, not associated with increased LV size, would have been normal. For clinical purposes, they suggest using the cut-offs of 45 mm in women and 50 mm in men to distinguish physiologic from pathologic LA enlargement. I would add that a more accurate measure of LA size should also be done if this is an issue.