Abstract
BACKGROUND:
Echocardiographic evaluation of the heart and its function, especially left ventricular systolic function, has great clinical importance. Systolic function can be measured using several methods, such as the amplitude of motion of the left atrioventricular plane (mitral annulus motion [MAM]) toward the apex during systole. Similarly, right ventricular systolic function can be measured using the motion of the right atrioventricular plane (tricuspid annulus motion [TAM]) toward the apex during systole.
OBJECTIVES:
Because the mitral and tricuspid annuli are situated close to each other in the fibrous skeleton between both ventricles and atria, one might think that a decrease in the amplitude of MAM would be followed by a decrease in the amplitude of TAM. The present study was developed to determinine if this anatomical intimacy causes a good correlation between the amplitudes of TAM and MAM.
METHODS:
Nineteen healthy subjects and 103 consecutive patients were included in the study and examined using echocardiography. The amplitudes of TAM and MAM were measured and the correlation between the amplitudes was calculated.
RESULTS:
In the 103 consecutive patients, a significant but relatively weak positive correlation was found between TAM and MAM amplitudes (Pearson’s correlation coefficient [r]=0.58; P<0.001). In the 19 healthy subjects, no significant correlation was found.
CONCLUSIONS:
Despite the anatomical intimacy of the annuli, the correlation between the amplitudes of TAM and MAM in consecutive patients was rather weak, and there was no correlation in healthy subjects. These findings could be due to anatomical and physiological differences between the right and left ventricles.
Keywords: Echocardiography, Heart, Left ventricle, Myocardium, Right ventricle
The heart and its function, especially left ventricular (LV) systolic function, are of great clinical interest, particularly in patients who have had a myocardial infarction or who suffer from dyspnea. Heart function can be assessed using a variety of methods including echocardiography, LV contrast angiography, nuclear angiography and magnetic resonance imaging. Because there is no radiation and the equipment is easy to use at bedside, echocardiography has become the preferred clinical method.
During echocardiographic examination, various standardized acoustic windows or projections are used to obtain different image planes of the heart (1). This is accomplished through the echocardiographic transducer (where the crystals sending and receiving the ultrasound beams are located), which is held in varying positions on the chest of the patient.
LV systolic function
LV systolic function can be assesed by several different indexes. The most common index used is LV ejection fraction (LVEF), which is the absolute difference between LV end-diastolic and end-systolic volume over LV end-diastolic volume. LVEF is often expressed as a percentage, with an LVEF greater than 50% considered normal. LVEF can be calculated using Simpson’s biplane method (1), which divides the LV cavity at the end of diastole or systole into several discs, whose volumes are then calculated using integrals. Practically, when using echocardiography and Simpson’s biplane method, the transducer is held to the chest to obtain an apical view of the heart. It is then possible to trace the LV endocardial border during the end of diastole and systole from both an apical four- and two-chamber view (Figure 1). The echocardiograph then automatically calculates the LVEF.
Figure 1).
Schematic of the echocardiographic apical four-chamber (a) and two-chamber view (b) at the end of diastole (left ventricle [LV] and right ventricle [RV] are indicated but the atria are not included). During systole, the atrioventricular (AV)-plane moves toward the apex (dotted arrows). The motion of the left AV-plane (mitral annulus motion [MAM]) is shown using motion (M)-mode at the lateral (L) site. There is a similar motion registered with M-mode at the three other sites used to measure the average amplitude of MAM: the septal (S), posterior (P) and anterior (A) sites. The M-mode recording of the motion of the right AV-plane at the RV lateral (RVL) site (tricuspid annulus motion [TAM]) is also shown, as well as the localization for measuring right ventricular size (RV inflow tract 3 [RVIT3]). The endocardial border (EB) of the LV in apical four-and two-chamber views is traced using Simpson’s biplane method to measure the LV volume at the end of diastole and the end of systole. T Transducer
Alternatively, LV systolic function can be expressed by measuring the amplitude of LV systolic shortening in the long-axis direction (2–9). This can be accomplished using the apical four-and two-chamber view measuring the amplitude of motion of the left atrioventricular plane (mitral annulus motion [MAM]) toward the apex during systole. This amplitude is usually measured using motion (M)-mode, ie, using one-dimensional images of the heart. One of the hallmarks of M-mode echocardiography is high temporal resolution. In M-mode, image distance or depth is along the vertical axis and time is on the horizontal axis (1). Four different sites of the mitral annulus are used when measuring the amplitude of MAM: the septal and lateral sites (obtained from the apical four-chamber view), and the posterior and anterior sites (obtained from the apical two-chamber view) (Figure 1). The average value of these amplitudes is used as the amplitude of MAM.
Right ventricular systolic function
In the same way that LV systolic long-axis shortening is used in the assessment of LV systolic function, right ventricular (RV) systolic function can be assessed using tricuspid annulus motion (TAM), ie, the systolic shortening of the RV in the long-axis direction (10–12). TAM is usually measured using an apical four-chamber view at the lateral site of the RV atrio-ventricular plane (the tricuspid annulus), and is determined by the amplitude of motion between diastole and systole (usually using M-mode images) (Figure 1).
OBJECTIVES
The mitral and tricuspid annuli are located anatomically close together, and are connected through the central fibrous body and fibrous trigones (13) (parts of the fibrous skeleton at the base of the heart between both ventricles and atria). It has been shown that the amplitude of TAM is greater than MAM in healthy individuals (14). However, it is unknown what happens to the amplitude of TAM when there is a decrease in the amplitudes of MAM and the LV systolic function. One might think that a decrease in the amplitude of MAM would be accompanied by a decrease in the amplitude of TAM, and that the correlation between MAM and TAM would be strong. In the present study, we sought to evaluate this correlation and determine its strength not only in patients, but also in healthy individuals.
In addition, we examined the correlation between TAM and the LVEF values obtained using Simpson’s biplane method which, in addition to reflecting the systolic shortening of the LV in the long-axis direction, also reflects LV systolic shortening in the short-axis direction. We hypothesized that the correlation between TAM and the LVEF would be weaker than the correlation between TAM and MAM because both annuli are part of the fibrous skeleton between the ventricles and atria.
PATIENTS AND METHODS
Patients
To study the correlation between the amplitudes of MAM and TAM in subjects with different LV systolic function, 103 consecutive patients (46 women and 57 men) were included in the study. Because previous studies have shown a decreased MAM amplitude in patients with atrial fibrillation (15,16), and in patients with a LV wall thickness greater than 14 mm (17), these patients were excluded from the present study. In addition, patients with left and/or right bundle branch block, pacemaker treatment or a history of cardiac surgery were also excluded because the relationship of MAM to LV systolic function has not been sufficiently investigated in those cases. Informed consent was obtained from all subjects. Patient characteristics and measurements are shown in Table 1.
TABLE 1.
Basic characteristics, measurements and calculated variables in 103 consecutive patients
| Variable | Mean ± SD |
|---|---|
| Age (years) | 52.7±16.8 |
| Body surface area (m2)* | 1.87±0.2 |
| Left ventricular ejection fraction by Simpson’s biplane method (%) | 59±14 |
| Mitral annulus motion (mm) | 12.4±3.0 |
| Tricuspid annulus motion (mm) | 21.9±4.5 |
| RV size (RV inflow tract 3) (mm) | 31.2±4.6 |
Body surface area = (weight [kg] 0.425 × height [cm] 0.725)×0.007184 (see reference 25). RV Right ventricular
Healthy subjects
To study the correlation between the amplitudes of MAM and TAM in subjects with normal LVEF values, MAM and TAM (subjects with no decrease in LVEF values and no decrease in the amplitudes of MAM and TAM), 19 healthy subjects (nine women and 10 men) with a mean age of 28.8 years were examined. Informed consent was obtained from each subject. Subject characteristics and measurements are shown in Table 2.
TABLE 2.
Basic characteristics, measurements and calculated variables in 19 healthy subjects
| Variable | Mean ± SD |
|---|---|
| Age | 28.8±7.9 |
| Body surface area (m2)* | 1.85±0.2 |
| Left ventricular ejection fraction by Simpson’s biplane method (%) | 64±4 |
| Mitral annulus motion (mm) | 15.8±2.0 |
| Tricuspid annulus motion (mm) | 23.8±3.5 |
Body surface area = (weight [kg] 0.425 × height [cm] 0.725)×0.007184 (see reference 25)
Echocardiographic examination
Acuson Sequoia echocardiographs (Acuson Co, USA) were used for echocardiographic examinations. Both patients and healthy subjects were studied in the lateral recumbent position. Echocardiographic techniques and calculations of different cardiac dimensions were performed in accordance with recommendations from the American Society of Echocardiography Committee (18–20). The amplitude of TAM was measured from the RV atrio-ventricular plane at the lateral site in the apical four-chamber view (1) from the M-mode recordings (Figures 1 and 2). The size of the RV was measured in the apical four-chamber view, one-third of the distance from the base of the RV (RV inflow tract 3) (1) (Figure 1). M-mode measurements of MAM were performed using the four sites described by Höglund et al (21) (Figure 1).
Figure 2).
Echocardiographic motion-mode recording in an apical four-chamber view at the lateral site of the right ventricle in a 37-year-old man. The amplitude (T) of tricuspid annulus motion is shown
Simpson’s biplane method was used to calculate the LVEF. All patients and healthy subjects were in sinus rhythm, and the cardiac measurements were calculated as the average of three beats.
Statistics
Pearson’s correlation coefficient was used for analyses of linear correlation between variables. The two-tailed Student’s t test was used to determine whether correlations were statistically significant. Data were analyzed using SPSS (Base 12.0.1) statistical software (SPSS, USA). P<0.05 was considered significant.
RESULTS
Patients
A significant positive correlation was found between the amplitudes of TAM and MAM (r=0.58; P<0.001) (Figure 3). There was also a significant positive correlation between the amplitude of TAM and the LVEF values obtained using Simpson’s biplane method (r=0.44; P<0.001) (Figure 4).
Figure 3).
Correlation between mitral annulus motion (MAM) and tricuspid annulus motion (TAM) in 103 consecutive patients. SEE Standard error of the estimate
Figure 4).
Correlation between left ventricular ejection fraction (LVEF) and tricuspid annulus motion (TAM) in 103 consecutive patients. SEE Standard error of the estimate
Healthy subjects
No significant correlations were found between the amplitudes of TAM and MAM or between TAM and the LVEF values (Figures 5 and 6).
Figure 5).
Correlation between mitral annulus motion (MAM) and tricuspid annulus motion (TAM) in 19 healthy subjects. SEE Standard error of the estimate
Figure 6).
Correlation between left ventricular ejection fraction (LVEF) and tricuspid annulus motion (TAM) in 19 healthy subjects. SEE Standard error of the estimate
DISCUSSION
TAM and MAM
The mitral and tricuspid annului are located anatomically close to each other, and are connected through the central fibrous body and fibrous trigones (13). Based on their close proximity, one might presume there should be a high correlation between the amplitudes of TAM and MAM. However, as shown in the present study, the correlation is relatively weak in patients and there is no significant correlation in healthy subjects. One may wonder why the correlation between TAM and MAM amplitudes in patients is not higher, and why there is no correlation in healthy subjects. There are several possible reasons to explain these findings and why the systolic shortening of the RV in the long-axis direction may be preserved or less affected than expected when LV systolic function is impaired.
Although there are common spiralling muscle bundles encircling the ventricles (22), there are also differences between the fibre architecture of the LV and RV; the RV wall is simpler than the LV wall, with fewer muscle layers. For instance, the middle part of the LV wall has both subepicardial and subendocardial longitudinal fibres, while the RV wall has only subendocardial longitudinal fibres (13). This difference in fibre architecture might be one factor that contributes to the amplitude of TAM being greater than the amplitude of MAM in healthy individuals (14).
Of note, damage to the LV subendocardial longitudinal fibres (eg, by subendocardial infarction) would most likely not affect the RV subendocardial longitudinal fibres, which means preserved systolic shortening of the RV in the long-axis direction despite a probable decrease in LV systolic function.
Another possible reason for preserved or nearly preserved RV systolic function in the long-axis direction (in the presence of a myocardial infarction affecting the LV) could be that the RV and its free wall are mainly supplied by the right coronary artery (22), while LV muscle mass is mainly supplied by the left coronary artery and its branches. Even with a total or partial occlusion of the right coronary artery, RV systolic function may not be as affected because myocardial O2 consumption has been shown to be lower in the RV than in the LV, and the collateral blood flow to the RV myocardium may provide additional protection (22).
The sarcomeres of the RV have been found to reach the same length as the sarcomeres of the LV at lower pressures (22), meaning that even if LV systolic function and the cardiac output are decreased, the RV may maintain its function because the sarcomeres of the RV will sustain the strength of contraction.
Another possible reason for preserved or nearly preserved RV systolic long-axis function (when LV systolic function declines) could be that the RV is pumping blood at the same rate and volume as the thick-walled LV against the pulmonary circulation, which has lower mean pressure gradients and pulmonary vascular resistance than does systemic circulation. However, according to the backward failure theory in severe LV dysfunction (23), it is likely that the RV will also become more affected and overt signs of RV systolic dysfunction may appear. However, there may be other reasons to explain why the systolic shortening of the RV in the long-axis direction can be preserved or nearly preserved with a decrease in LV systolic function.
Despite the above-mentioned reasons as to why the RV can maintain its systolic long-axis function when LV systolic long-axis function is impaired, one can still wonder why the amplitudes of TAM and MAM differ and why there is no significant correlation between them in healthy subjects. Although both annuli are part of the same fibrous skeleton between the ventricles and atria, the annuli are not rigid fibrous rings, but thin, pliable structures attached to the two major collagen structures in the middle of the heart, the left and right trigones. These structures are in continuity with the mitral and tricuspid valves, the membranous septum and the posterior wall of the aortic root. The shape and area of the mitral annulus have been shown to change during the cardiac cycle, being more circular in late diastole and more elliptical in systole, the same changes could occur with tricuspid annulus (14).
TAM and LVEF
In patients, the correlation between TAM and LVEF values was weaker than between TAM and MAM, which may indicate that the anatomical intimacy between the annuli has some impact on correlation because LVEF values obtained using Simpson’s biplane method not only reflect the systolic shortening of the LV in the long-axis direction but also in the short-axis direction. However, the lack of a significant correlation between TAM and LVEF values in healthy subjects did not support this.
CONCLUSIONS
Despite the anatomical intimacy between the mitral and tricuspid annuli (both being situated in the fibrous skeleton between both ventricles and atria), there was a relatively weak correlation between the amplitudes of TAM and MAM in patients who had a decrease in TAM and/or MAM, and there was no correlation at all in healthy individuals. This means that an individual with a relatively low MAM amplitude can still have a high TAM amplitude and vice versa, which may be due to the anatomical and physiological differences between the RV and LV.
Limitations of the study
Although standardized projections have been previously used to obtain similar image planes of the heart both in patients and healthy subjects (1), the sites from which measurements were made may differ within and between individuals. Image plane variation, which may have had a small effect on the present study, may also arise due to translation (movement of the heart as a whole in the chest), rotation (circular motion around the long axis of the LV) and torsion (unequal rotational motion at the apex versus the base of the LV) of the heart during the heart cycle (24). However, an earlier study on subjects without LV hypertrophy (excluded in the present study) (17) and a study on TAM (14) showed strong intra- and interobserver reproducibility when measuring MAM and TAM by M-mode, respectively.
The mean age of the patients was higher than the healthy subjects, which may have had some, but probably small, influence on the results.
REFERENCES
- 1.Feigenbaum H. Echocardiography. 5th edn. Philadelphia: Lea & Febiger; 1994. pp. 1–695. [Google Scholar]
- 2.Alam M, Höglund C, Thorstrand C, Philip A. Atrioventricular plane displacement in severe congestive heart failure following dilated cardiomyopathy or myocardial infarction. J Intern Med. 1990;228:569–75. doi: 10.1111/j.1365-2796.1990.tb00281.x. [DOI] [PubMed] [Google Scholar]
- 3.Alam M. The atrioventricular plane displacement as a means of evaluating left ventricular systolic function in acute myocardial infarction. Clin Cardiol. 1991;14:588–94. doi: 10.1002/clc.4960140711. [DOI] [PubMed] [Google Scholar]
- 4.Alam M, Höglund C, Thorstrand C, Hellekant C. Haemodynamic significance of the atrioventricular plane displacement in patients with coronary artery disease. Eur Heart J. 1992;13:194–200. doi: 10.1093/oxfordjournals.eurheartj.a060146. [DOI] [PubMed] [Google Scholar]
- 5.Alam M, Höglund C, Thorstrand C. Longitudinal systolic shortening of the left ventricle: An echocardiographic study in subjects with and without preserved global function. Clin Physiol. 1992;12:443–52. doi: 10.1111/j.1475-097x.1992.tb00348.x. [DOI] [PubMed] [Google Scholar]
- 6.Cevik Y, Degertekin M, Basaran Y, Turan F, Pektas O. A new echocardiographic formula to calculate ejection fraction by using systolic excursion of mitral annulus. Angiology. 1995;46:157–63. doi: 10.1177/000331979504600210. [DOI] [PubMed] [Google Scholar]
- 7.Emilsson K, Alam M, Wandt B. The relation between mitral annulus motion and ejection fraction: A nonlinear function. J Am Soc Echocardiogr. 2000;13:896–901. doi: 10.1067/mje.2000.107253. [DOI] [PubMed] [Google Scholar]
- 8.Pai RG, Bodenheimer MM, Pai SM, Koss JH, Adamick RD. Usefulness of systolic excursion of the mitral annulus as an index of left ventricular systolic function. Am J Cardiol. 1991;67:222–4. doi: 10.1016/0002-9149(91)90453-r. [DOI] [PubMed] [Google Scholar]
- 9.Simonson J, Schiller NB. Descent of the base of the left ventricle: An echocardiographic index of left ventricular function. J Am Soc Echocardiogr. 1989;2:25–35. doi: 10.1016/s0894-7317(89)80026-4. [DOI] [PubMed] [Google Scholar]
- 10.Kaul S, Tei C, Hopkins JM, Shah PM. Assessment of right ventricular function using two-dimensional echocardiography. Am Heart J. 1984;107:526–31. doi: 10.1016/0002-8703(84)90095-4. [DOI] [PubMed] [Google Scholar]
- 11.Smith JL, Bolson EL, Wong SP, Hubka M, Sheehan FH. Three-dimensional assessment of two-dimensional technique for evaluation of right ventricular function by tricuspid annulus motion. Int J Cardiovasc Imaging. 2003;19:189–97. doi: 10.1023/a:1023655705807. [DOI] [PubMed] [Google Scholar]
- 12.Ueti OM, Camargo EE, Ueti Ade A, de Lima-Filho EC, Nogueira EA. Assessment of right ventricular function with Doppler echocardiographic indices derived from tricuspid annular motion: Comparison with radionuclide angiography. Heart. 2002;88:244–8. doi: 10.1136/heart.88.3.244. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Greenbaum RA, Ho SY, Gibson DG, Becker AE, Anderson RH. Left ventricular fibre architecture in man. Br Heart J. 1981;45:248–63. doi: 10.1136/hrt.45.3.248. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Hammarström E, Wranne B, Pinto FJ, Puryear J, Popp RL. Tricuspid annular motion. J Am Soc Echocardiogr. 1991;4:131–9. doi: 10.1016/s0894-7317(14)80524-5. [DOI] [PubMed] [Google Scholar]
- 15.Emilsson K, Wandt B. The relation between ejection fraction and mitral annulus motion before and after direct-current electrical cardioversion. Clin Physiol. 2000;20:218–24. doi: 10.1046/j.1365-2281.2000.00249.x. [DOI] [PubMed] [Google Scholar]
- 16.Emilsson K, Wandt B. The relation between mitral annulus motion and left ventricular ejection fraction in atrial fibrillation. Clin Physiol. 2000;20:44–9. doi: 10.1046/j.1365-2281.2000.00222.x. [DOI] [PubMed] [Google Scholar]
- 17.Wandt B, Bojö L, Tolagen K, Wranne B. Echocardiographic assessment of ejection fraction in left ventricular hypertrophy. Heart. 1999;82:192–8. doi: 10.1136/hrt.82.2.192. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Henry WL, Demaria A, Gramiak R, et al. Report of the American Society of Echocardiography Committee on Nomenclature and Standards in Two-dimensional Echocardiography. Circulation. 1980;62:212–7. doi: 10.1161/01.cir.62.2.212. [DOI] [PubMed] [Google Scholar]
- 19.Sahn DJ, DeMaria A, Kisslo J, Weyman A. Recommendations regarding quantitation in M-mode echocardiography: Results of a survey of echocardiographic measurements. Circulation. 1978;58:1072–83. doi: 10.1161/01.cir.58.6.1072. [DOI] [PubMed] [Google Scholar]
- 20.Schiller NB, Shah PM, Crawford M, et al. Recommendations for quantitation of the left ventricle by two-dimensional echocardiography. American Society of Echocardiography Committee on Standards, Subcommittee on Quantitation of Two-Dimensional Echocardiograms. J Am Soc Echocardiogr. 1989;2:358–67. doi: 10.1016/s0894-7317(89)80014-8. [DOI] [PubMed] [Google Scholar]
- 21.Höglund C, Alam M, Thorstrand C. Atrioventricular valve plane displacement in healthy persons. An echocardiographic study. Acta Med Scand. 1988;224:557–62. doi: 10.1111/j.0954-6820.1988.tb19626.x. [DOI] [PubMed] [Google Scholar]
- 22.Dell’Italia LJ. The right ventricle: Anatomy, physiology, and clinical importance. Curr Probl Cardiol. 1991;16:653–720. doi: 10.1016/0146-2806(91)90009-y. [DOI] [PubMed] [Google Scholar]
- 23.Braunwald E. Heart Disease: A Textbook of Cardiovascular Medicine. 6th edn. Philadelphia: WB Saunders Co; 2001. pp. 536–37. [Google Scholar]
- 24.Otto C. Textbook of Clinical Echocardiography. 2nd edn. Philadelphia: WB Saunders Co; 2000. pp. 1–443. [Google Scholar]
- 25.Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. 1916. Nutrition. 1989;5:303–13. [PubMed] [Google Scholar]