Left atrial enlargement

Left atrial enlargement (LAE) or left atrial dilation refers to enlargement of the left atrium (LA) of the heart, and is a form of cardiomegaly.

Causes

In the general population, obesity appears to be the most important risk factor for LAE.^[1] LAE has been found to be correlated to body size, independent of obesity, meaning that LAE is more common in people with a naturally large body size. ^[2] Also, a study found that LAE can occur as a consequence of atrial fibrillation (AF),^[3] although another study found that AF by itself does not cause LAE. The latter study also showed that the persistent type of AF was associated with LAE, but the number of years that a subject had AF was not.^[4]

Obstructive sleep apnea (OSA) may be a cause of LAE in some cases. When an OSA event occurs, there is an attempt to breathe with an obstructed airway and the pressure inside the chest is suddenly lowered. The negative intrathoracic pressure may cause the left atrium to expand and stretch its walls during each OSA event. Over time, the repetitive stretching of the left atrium may result in a persistent left atrial enlargement.^[5]

Clinical implications

Although other factors may contribute, left atrium size has been found to be a predictor of mortality due to both cardiovascular issues as well as all-cause mortality. Current research suggests that left atrium size as measured by an echo-cardiograph may have prognostic implications for preclinical cardiovascular disease. However, studies that have found LAE to be a predictor for mortality recognize the need for more standardized left atrium measurements than those found in an echo-cardiogram. ^[2]

Diagnosis

LAE is suggested by an electrocardiogram (ECG) that has a pronounced notch in the P wave.^[6] However, if there is atrial fibrillation, a P wave would not be present.^[7] In any case, LAE can be diagnosed and measured using an echocardiogram (ECHO).

Characterizing the size of the left atrium according to its volume is preferred over a single linear dimension since enlargement can be different for different directions. For example, because of the smaller distance in the thoracic cavity between the sternum and spine, compared to the other directions, there is less room for enlargement of the left atrium along the anteroposterior axis.^[8] By approximating the shape of the left atrium as an ellipsoid, its volume can be calculated from measurements of its dimensions along three perpendicular directions.^[3]

Indexing the left atrial volume to body surface area (volume/BSA) is recommended by the American Society of Echocardiography and the European Association of Echocardiography. The values for volume/BSA in the following table are the ones that are the best validated and are the same for both men and women.^[8]

Left Atrium Size[8]	Women				Men
	normal	enlarged			normal	enlarged
		mild	moderate	severe		mild	moderate	severe
Diameter  (mm)	27–38	39–42	43–46	≥47	30–40	41–46	47–52	≥52
Volume  (ml)	22–52	53–62	63–72	≥73	18–58	59–68	69–78	≥79
Volume/BSA  (ml/m²)	16–28	29–33	34–39	≥40	16–28	29–33	34–39	≥40
BSA, body surface area

References

1. Stritzke J, Markus MRP, Duderstadt S, Lieb W, Luchner A, Döring A, Keil U, Hense H and Schunkert H (2009-11-17). "The Aging Process of the Heart: Obesity Is the Main Risk Factor for Left Atrial Enlargement During Aging: The MONICA/KORA (Monitoring of Trends and Determinations in Cardiovascular Disease/Cooperative Research in the Region of Augsburg) Study". Journal of the American College of Cardiology 54 (21): 1982–9. doi:10.1016/j.jacc.2009.07.034. PMID 19909880. Retrieved 2009-12-02.
2. Patel DA, Lavie CJ, Milani RV, Shah S, Giliand Y. (Winter 2009). "Clinical Implications of Left Atrial Enlargement: A Review". The Ochsner Journal 9 (4): 191–196. PMC 3096293. PMID 21603443.
3. Sanfilippo AJ, Abascal VM, Sheehan M, Oertel LB, Harrigan P, Hughes RA and Weyman AE (1990). "Atrial enlargement as a consequence of atrial fibrillation A prospective echocardiographic study". Circulation 82 (3): 792–7. doi:10.1161/01.CIR.82.3.792. PMID 2144217. Retrieved 2009-12-02.
4. Osranek M, Bursi F, Bailey KR, Grossardt BR, Brown RD Jr, Kopecky SL, Tsang TS and Seward JB. (Dec 2005). "Left atrial volume predicts cardiovascular events in patients originally diagnosed with lone atrial fibrillation: three-decade follow-up". European Heart Journal 26 (23): 2556–61. doi:10.1093/eurheartj/ehi483. PMID 16141257. Retrieved 2009-12-27. See p. 2560 Left ventricular filling pressure, LAV, and AF.
5. Latina JM, Estes III NAM, Garlitski AC (2013). "The Relationship between Obstructive Sleep Apnea and Atrial Fibrillation: A Complex Interplay". Pulmonary Medicine 2013 (621736): 1–11. doi:10.1155/2013/621736. PMC 3600315. PMID 23533751. Retrieved 2014-08-11. See section 5.1.
6. Edhouse J, Thakur RK, Khalil JM (2002-05-25). "ABC of clinical electrocardiography. Conditions affecting the left side of the heart.". British Medical Journal 324 (7348): 1264–7. doi:10.1136/bmj.324.7348.1264. PMC 1123219. PMID 12028984. Retrieved 2010-06-18.
7. "Atrial Fibrillation (for Professionals)". American Heart Association, Inc. 2008-12-04. Archived from the original on 2009-03-28.
8. Lang RM, Bierig M, Devereux RB, Flachskampf FA, Foster E, Pellikka PA, Picard MH, Roman MJ, Seward J, Shanewise J, Solomon S, Spencer KT, St John Sutton M, Stewart W (March 2006). "Recommendations for chamber quantification". European Journal of Echocardiography 7 (2): 79–108. doi:10.1016/j.euje.2005.12.014. PMID 16458610. Retrieved 2012-08-26.