Determination of Left Atrial Appendage Morphology
K.A. Rudolfstiftung
Neurologisches Krankenhaus Rosenhügel Wien, Österreich
To the Editor:
Veinot et al1 reviewed 500 heart specimens from autopsies during a 22-year period. They described the anatomy of the left atrial appendage (LAA) by determining orifice diameter, width, length, and number of lobes. They found orifice size, width, and length to be age and sex related. In men and women aged >20 years, mean orifice diameters of 1.16 and 1.07 cm, length of 2.59 and 2.53 cm, and width of 1.83 and 1.66 cm were found, respectively, as well as 1 to 4 lobes.
In a study on 220 LAA casts obtained shortly after death,2 we determined LAA morphology by describing the course and ramifications of the principal axis and by measuring minimal and maximal orifice diameters, length (bottom to top), width (at right angles), and volume. The course of the principal axis was straight (7%), slightly bent and slightly spiral (23%), slightly bent and extremely spiral (5%), extremely bent and slightly spiral (24%), or extremely bent and extremely spiral (42%). Fifty-six percent of the casts had >5 branches (orifice area >10 mm2), and 47% had >40 twigs (orifice area 1 to 10 mm2). The mean minimal and maximal orifice diameters were 15 and 21 mm, respectively. Mean length was 30 mm, width was 31 mm, and volume was 5220 mm3. The casts of 35 cases with normal cardiac findings were not different from those that showed pathological cardiac findings at autopsy.
Differences between the results of the study by Veinot et al and our results can be explained as follows:
1. The specimens used in the 2 studies were of different age and type of conservation. It is possible that the years of conservation led to a shrinkage and change of the elastic properties of the LAA tissue, whereas casting possibly led to dilation of the LAA. This assumption is supported by the shorter LAA length in the study by Veinot et al compared with our study. Furthermore, the number of LAA outpouchings is lower in their study compared with our study.
2. Veinot et al measured the LAA tissue, whereas we measured synthetic resin casts.
3. The orifice diameters were measured differently.
4. Veinot et al measured width as the widest external width, whereas we measured at right angles, perpendicular to the bottom-to-top axis.
5. The definition of lobes in the study by Veinot et al differed from our definition of branches and twigs.
We conclude that postmortem casts may reflect the intravitam morphology of the LAA more closely than specimens conserved for years. We demonstrate that the anatomy and morphology of the LAA is more complex, bizarre, and variable than previously thought. This should be considered when images of the LAA are being interpreted, in particular when thrombi are being diagnosed.
References
1.
Veinot JP, Harrity PJ, Gentile F, Khandheria BK,
Bailey KR, Eickholt JT, Seward JB, Tajik AJ, Edwards WD.
Anatomy of the normal left atrial appendage: a quantitative
study of age-related changes in 500 autopsy hearts: implications for
echocardiographic examination. Circulation. 1997;96:3112–3115.
2. Ernst G, Stöllberger C, Abzieher F, Veit-Dirscherl W, Bonner E, Bibus B, Schneider B, Slany J. Morphology of the left atrial appendage. Anat Rec. 1995;242:553–561.[Medline] [Order article via Infotrieve]
Response
Division of Cardiovascular Diseases and Internal Medicine
Division of Anatomic Pathology
Mayo Clinic and Mayo Foundation Rochester, Minn
We have read with interest the comments made by Dr Ernst and colleagues on our article on left atrial appendage (LAA).1
The differences between our results and those of Ernst et al2 have been explained in their letter. We do not agree with the comments that postmortem casts reflect the intravitam morphology of the LAA more closely than specimens conserved for years. Both techniques have their own limitations. It is surprising to note no differences in normal specimens versus those with cardiac pathology, particularly if those with cardiac pathology had mitral valve disease.
The predominant issues that are important from the standpoint of clinicians who perform transesophageal echocardiography are not necessarily the length and the orifice diameter but the presence of lobes and pectinate muscles, given that they can be sources of error in the interpretation of the study.
Ernst et al and our group make similar points that the morphology and anatomy of the LAA are complex and variable and that these facts need to be considered when images are interpreted.
We have documented cases in which thrombi have been present in 1 lobe but not in the other lobes of the LAA. Therefore, interrogation of the LAA needs to be made in multiple imaging planes, and the preferred technology of choice is either a multiplane or at the very least a biplane transesophageal transducer.
References
1. Veinot JP, Harrity PJ, Gentile F, Khandheria BK, Bailey KR, Eickholt JT, Seward JB, Tajik AJ, Edwards WD. Anatomy of the normal left atrial appendage: a quantitative study of age-related changes in 500 autopsy hearts: implications for echocardiographic examination. Circulation. 1997;96:3112–3115.
2. Ernst G, Stöllberger C, Abzieher F, Veit-Dirscherl W, Bonner E, Bibus B, Schneider B, Slany J. Morphology of the left atrial appendage. Anat Rec. 1995;242:553–561.
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