- Email: [email protected]
Potential Applications for Transesophageal Echocardiography in Hypertrophic Cardiomyopathies
Potential Applications for Transesophageal Echocardiography in Hypertrophic Cardiomyopathies Petr Widimsky, MD: Folkert J. Ten Cate, MD, Wim Vletter, MSC, and Lex van Herwerden, MD, Rotterdam, The Netherlands
The purpose of the present study was to evaluate the potential advantages of transesophageal echocardiography (TEE) in comparison with transthoracic echocardiography (TIE) in selected patients with hypertrophic cardiomyopathy. Ten patients with previously established or suspected diagnosis of hypertrophic cardiomyopathy were examined by TEE to solve specific clinical questions. TEE was well tolerated by all patients; no arrhythmias were seen during the procedure. The comparison ofTTE and TEE showed the following: Advantages ofTTE-better assessment of the left ventricle, myocardial thickness measurements available in all regions and sufficient for the diagnosis of hypertrophic cardiomyopathy in nine out of 10 patients; advantages of TEE-precise assessment of mitral valve morphology and regurgitant jets, detailed evaluation of systolic anterior motion, and subaortic membrane (not seen by TTE) recognized in one patient. Clinically, in three patients TEE influenced the management (mitral leaflet perforation, subaortic membrane, and residual mitral regurgitation after valvuloplasty). Thus TEE enables more precise diagnosis in some patients with hypertrophic cardiomyopathy and has the potential to influence their surgical management. However, for medical treatment of hypertrophic cardiomyopathy, TIE is sufficient. (JAM Soc EcHOCARDIOGR 1992;5:163-7.)
Transesophageal echocardiography (TEE) has be come a highly accurate diagnostic method in certain situations: diagnosis of thoracic aorta diseases and evaluation of prosthetic valves and infectious endo carditis. 1 The method is especially useful to evaluate the morphology and, in conjunction with color Doppler, to evaluate the functional properties of the mitral valve apparatus. In addition, left ventricular outflow tract morphology might be studied in high detail. Therefore, we decided to use TEE in selected patients with hypertrophic cardiomyopathy, because current knowledge of the usefulness of TEE in this condition is scarce. 2 •3
From the Thoraxcenter, Department of Cardiology and Cardio vascular Surgery, Erasmus University. 'Research fellow of the European Society of Cardiology. Reprint requests: F. J. Ten Cate, MD, Academic Hospital Dijk zigt, Thoraxcenter Ba 350, Dr. Molewaterplein 40, 3015 GD Rotterdam, The Netherlands. 27/1133809
METHODS
Ten patients with hypertrophic cardiomyopathy were examined by TEE. All of them had been seen at our institution on an outpatient basis for several months or years before the transesophageal study. The reason for transesophageal examination was based on clinical change in the patient's condition, or it was done after surgery to reveal more details (see below). Nine patients were men, one was a woman. The mean age of the group was 47 years (range 33 to 61 years). The clinical data are sum marized in Table l. Transthoracic echocardiographic (TIE) examina tion always preceded the transesophageal study. Both examinations were performed with commercially available equipment (Toshiba SSH 160, Toshiba, Tokyo, Japan, or Hewlett-Packard Sonos 1000, Hewlett Packard, Andover, Massachusetts) with 5.0 MHz transesophageal probes in routinely used cross sections.4·6 For the transesophageal study, the pa tients received preoperative medication of 5 mg in travenous midazolam. They were then placed in the
163
Journal of the American Society of Echocardiography
164 Widimsky et al.
Perforation of anterior mitral leaflet (arrows) in patient No. 2. TEE four-chamber view with angulation to left ventricular outflow tract (L VOT). LA, Left atrium; LV, left ventricle.
Figure 1
Table 1
Clinical data of the patients (n = 10)
Mean age (years) NYHA class (no. of patients) Electrocardiographic rhythm (no. of patients) LVHon electrocardiographic Mean LVOT gradient (mm Hg) [no. of patients]
47 (range 33-61) 1(1), II(3), III(S), IV(1) Sinus (8), AF (2)
All 39 mm Hg (range 31 56)[8]; no gradient[2]
NYHA, New York Heart Association; LVH, left ventricular hypertrophy; AF, atrial fibrillation; L VOT, left ventricular outflow tract.
left lateral decubitus position and examined (after lidocaine spray was applied to the oropharynx). The transducer was then advanced farther to the esoph agus, then to the cardia of the stomach. A routine examination as described previously1 •4 •6 was per formed in all patients. In the last four patients a biplane TEE probe was used. 5 RESULTS
No complications were observed during or after the examinations. There were no arrhythmias or other problems related to the procedure. The TIE and TEE findings are summarized in Table 2. For illus tration, four cases are descriibed below.
Patient number 1 was seen for clinically stable hy pertrophic cardiomyopathy for 4 years. He was ad mitted to the hospital for sudden onset of failure of left side of the heart with rapid progression to pul monary edema and hypotension. The TIE showed the classic picture of hypertrophic obstructive car diomyopathy with moderate mitral insufficiency. TEE showed much greater degree of mitral insuffi ciency and revealed its cause, perforation of anterior mitral leaflet (Figure 1). The patient underwent mi tral valve replacement with a St. Jude prosthesis and septal myectomy. The postoperative course was un eventful and the patient is now in functional class II. On gross inspection no vegetations on the perforated anterior mitral leaflet were found. Patient number 2 was seen for 4 years with the diagnosis of hypertrophic obstructive cardiomyopa thy. Because of clinical deterioration, surgical treat ment was considered and TEE was performed to exclude the presence ofa left ventricular outflow tract membrane, which was suspected (but not estab lished) at the last TIE readings. TEE clearly showed a discrete membranous subaortic stenosis. What was considered during TIE to be a systolic anterior mo tion (SAM), was really shown by TEE to be a contact of the membrane with the anterior mitral leaflet. The motion of the mitral valve itself and of the chordae apparatus was normal. Successful membrane enucle ation was performed and the patient is in functional class I. His left ventricular hypertrophy is in re gresslon.
Volume 5 Number 2 March-Aprill992
TEE in hypertrophic cardiomyopathies
165
Patient number 3 was seen for a severe form of hypertrophic cardiomyopathy and demonstrated progressive symptoms (class III). His TIE was of poor image quality. It showed severe left ventricular hypertrophy and possible SAM but was unable to describe any further details. TEE was performed as a part of preoperative evaluation and revealed an atypical SAM beginning at end-diastole (Figure 2) and very prominent through systole, a midventricular obstruction with nearly cavity obliteration during systole, and redundant mitral valve leaflets. The pa tient underwent septal myectomy and after surgery was in functional class I. Patient number 4 had hypertrophic obstructive car diomyopathy with mitral insufficiency and mitral an ulus calcification. In September 1990 she was suc cessfully resuscitated for ventricular fibrillation. Pre operative TEE confirmed the diagnosis and revealed secondary chordae attached to the body of posterior mitral leaflet. These secondary chordae were visual ized only in TEE long-axis view (Figure 3). In March 1991 she underwent septal myectomy with mitral valvuloplasty. Preoperative TEE revealed significant residual mitral insufficiency after valvuloplasty, and this led to immediate mitral valve replacement with a St. Jude mitral prosthesis (St. Jude Medical, Inc., St. Paul, Minn.). The patient recovered unevent fully.
DISCUSSION The safety of TEE in patients with hypertrophic cardiomyopathy. Despite a certain fear of arrhyth mias or worsening of the obstruction during TEE (possible spontaneous V alsalva maneuvers during the procedure), all patients tolerated the procedure well. The preoperative evaluation of the mitral valve morphology. TEE provided more details in three patients. In one patient, it was the only method to reveal the perforation of anterior mitral leaflet. Infectious endocarditis was thought to be the cause for this perforation. However, clinical picture, lab oratory findings, and absence of vegetations during TEE and on macroscopic inspection of the valve led us to consider another possible cause: myxomatous degeneration of the leaflets and subsequent perfo ration at the site, where mechanical damage during SAM might occur. Unfortunately, the microscopic examination of the excised valve was not performed. TEE also provided us more information about pro lapse or redundancy and about regurgitant jets of mitral valve in other patients.
Atypical early SAM observed in patient No.3. Anterior mitral leaflet remains in contact with interventri cular septum from late diastole (upper panel) to early systole (middle and lower panels). TEE four-chamber view. More details in the text. LA., Left atrium; MV, mitral valve; LV, left ventricle; OT, outflow tract; R V, right ventricle.
Figure 2
Perioperative assessment. Intraoperative TEE can be useful for assessment of the surgical results of septal myectomy and mitral valvuloplasty. Patient number 4 is an example; TEE influenced the im mediate operative management, and thus clinical outcome. Misinterpretation of the subaortic mem brane as SAM during TTE. Patient number 2 was seen under the diagnosis of hypertrophic obstructive cardiomyopathy. During TIE, concentric left ven tricular hypertrophy and SAM were described re
Journal of the American Society of Echocardiography
166 Widimsky et al.
Figure 3 Secondary chordae from posterior wall (PW) to posterior mitral leaflet. PM, Pap illary muscle; LA, left atrium; LV, left ventricle; A W, anterior wall.
Table 2 Transthoracic and transesophageal echocardiographic data of the patients (n SAM Mitral valve MI by color Doppler Max. myocardial thickness LVOT diameter LV diameter diastolic Image quality LA diameter
=
10)
TIE
TEE
8 (1 false positive) 7 normal, 2 redundant, 1 prolapse 6 26mm 15 mm 4lmm Good in 7, poor in 3 51 mm
7, LVOT membrane l 4 normal, 3 redundant, 2 prolapsing, l perforation 10 27mm 16mm 33mm Excellent in 7, good in 3 73mm
PL, Posterior leaflet; IVS, interventricular septum; LV, left ventricle; SAM, systolic anterior motion; L VOT, left ventricular outflow tract; MI, mitral insufficiency; LA, left atrium.
peatedly. Only during the last TIE was the suspicion for subaortic membrane first expressed. TEE revealed a membrane in the left ventricular outflow tract and excluded the presence of SAM. In all our patients TEE enabled more detailed description of left ven tricular outflow tract and SAM with clear clinical consequences in patient number 2. Indirect evidence for excessive mitral appa ratus size. It was recently described in pathology specimens/ in an in vitro model, 8 and in a detailed echocardiographic analysis 9 that excessive mitral valve area, elongation or both might be partly re sponsible for SAM, at least in some patients. Our observation in patient number 3 (Figure 2) is sup porting this theory in vivo. In this patient the anterior
mitral leaflet remained in contact with the interven tricular septum from end-diastole to early systole, at peak systole it further moved towards the aortic valve, thus showing an atypical motion (continuous ante rior motion of the anterior mitral leaflet with a max imum at mid-systole). We suggest the theoretic ex planation for this observation might be the excessive size of mitral valve or chordae with respect to the left ventricular cavity size. In the other six patients with SAM, this pattern was not observed. Biplane TEE. The use of biplane TEE in four patients enabled more detailed evaluation of the left ventricle, its outflow tract, and mitral regurgitant jets. Visualization of secondary chordae 10 was better in the long-axis view (Figure 2).
Volume 5 Number 2 March-Aprill992
TEE in hypertrophic cardiomyopathies
Conclusions
The data from this small group of patients with hy pertrophic cardiomyopathy suggest that TEE pro vides more detailed information about left ventricular outflow tract (including detailed visualization of SAM) and about mitral valve morphology and re gurgitant jets. TEE should be performed in all pa tients with hypertrophic obstructive cardiomyopathy before surgery to assess detailed morphology of mi tral valve and left ventricular outflow tract. However, in patients treated medically, TIE is sufficient for the diagnosis and follow-up.
4.
5.
6. 7.
8.
REFERENCES l. Gussenhoven EJ, Taarns MA, Roelandt J, et al. Oesophageal
echocardiography. lnt J Card Imaging 1987;2:231-9. 2. Stanley TE, Rankin JS. Idiopathic hypertrophic subaortic ste nosis and ischemic mitral regurgitation: the value of intra operative transesophageal echocardiography and Doppler color flow imaging in guiding operative therapy. Anesthe siology 1990;72:1083-5. 3. Mugge A, Daniel WG, Wolpers HG, Klapper JW, Lichtlen
9.
10.
167
PR. Improved visualization of discrete subvalvular aortic ste nosis by transesophageal color-coded Doppler echocardiog raphy. Am Heart J 1989;117:474-5. Seward JB, Khandheria BK, Oh JK, et al. Transesophageal echocardiogtaphy: technique, anatomic correlations, imple mentation, and clinical applications. Mayo Clin Proc 1988;63:649-80. Seward JB, Khandheria BK, Edwards WD, Oh JK, Freeman JK, TajikAJ. Biplanar transesophageal echocardiography: an atomic correlations, image orientation, and clinical applica tions. Mayo Clin Proc 1990;65:1193-213. Schiller NB, Maurer G, Ritter SB, et al. Transesophageal echocardiogtaphy. JAM Soc ECHOCARDIOGR 1989;2:354-7. Klues HG, Dollar AL, Roberts WC, Maron BJ. Diversity of mitral valve structure in patients with hypertrophic cardio myopathy: evidence for a primary mitral valve abnormality. Circulation 1990;82:III-293. Lefebvre X, Cagniot A, Yoganathan AP, Weyman AE, Levine RA. Reproduction of systolic anterior motion of the mitral valve in a pulsatile flow model. Circulation 1990;82:III-396. Mora E. Ten Cate FJ, Leonard JJ, Hugenholtz PG, Roelandt J. Genesis of systolic anterior motion of the mitral valve in hypertrophic cardiomyopathy: an anatomical or dynamic event? Eur Heart J 1987;8:1312-21. Chauvaud S, Carpentier A, Deloche A, et al. Chirurgie re constructrice de l'insiffisance mitrale acquise de !'enfant. Arch Mal Coeur 1980;73:1365-71.
The purpose of the present study was to evaluate the potential advantages of transesophageal echocardiography (TEE) in comparison with transthoracic echocardiography (TIE) in selected patients with hypertrophic cardiomyopathy. Ten patients with previously established or suspected diagnosis of hypertrophic cardiomyopathy were examined by TEE to solve specific clinical questions. TEE was well tolerated by all patients; no arrhythmias were seen during the procedure. The comparison ofTTE and TEE showed the following: Advantages ofTTE-better assessment of the left ventricle, myocardial thickness measurements available in all regions and sufficient for the diagnosis of hypertrophic cardiomyopathy in nine out of 10 patients; advantages of TEE-precise assessment of mitral valve morphology and regurgitant jets, detailed evaluation of systolic anterior motion, and subaortic membrane (not seen by TTE) recognized in one patient. Clinically, in three patients TEE influenced the management (mitral leaflet perforation, subaortic membrane, and residual mitral regurgitation after valvuloplasty). Thus TEE enables more precise diagnosis in some patients with hypertrophic cardiomyopathy and has the potential to influence their surgical management. However, for medical treatment of hypertrophic cardiomyopathy, TIE is sufficient. (JAM Soc EcHOCARDIOGR 1992;5:163-7.)
Transesophageal echocardiography (TEE) has be come a highly accurate diagnostic method in certain situations: diagnosis of thoracic aorta diseases and evaluation of prosthetic valves and infectious endo carditis. 1 The method is especially useful to evaluate the morphology and, in conjunction with color Doppler, to evaluate the functional properties of the mitral valve apparatus. In addition, left ventricular outflow tract morphology might be studied in high detail. Therefore, we decided to use TEE in selected patients with hypertrophic cardiomyopathy, because current knowledge of the usefulness of TEE in this condition is scarce. 2 •3
From the Thoraxcenter, Department of Cardiology and Cardio vascular Surgery, Erasmus University. 'Research fellow of the European Society of Cardiology. Reprint requests: F. J. Ten Cate, MD, Academic Hospital Dijk zigt, Thoraxcenter Ba 350, Dr. Molewaterplein 40, 3015 GD Rotterdam, The Netherlands. 27/1133809
METHODS
Ten patients with hypertrophic cardiomyopathy were examined by TEE. All of them had been seen at our institution on an outpatient basis for several months or years before the transesophageal study. The reason for transesophageal examination was based on clinical change in the patient's condition, or it was done after surgery to reveal more details (see below). Nine patients were men, one was a woman. The mean age of the group was 47 years (range 33 to 61 years). The clinical data are sum marized in Table l. Transthoracic echocardiographic (TIE) examina tion always preceded the transesophageal study. Both examinations were performed with commercially available equipment (Toshiba SSH 160, Toshiba, Tokyo, Japan, or Hewlett-Packard Sonos 1000, Hewlett Packard, Andover, Massachusetts) with 5.0 MHz transesophageal probes in routinely used cross sections.4·6 For the transesophageal study, the pa tients received preoperative medication of 5 mg in travenous midazolam. They were then placed in the
163
Journal of the American Society of Echocardiography
164 Widimsky et al.
Perforation of anterior mitral leaflet (arrows) in patient No. 2. TEE four-chamber view with angulation to left ventricular outflow tract (L VOT). LA, Left atrium; LV, left ventricle.
Figure 1
Table 1
Clinical data of the patients (n = 10)
Mean age (years) NYHA class (no. of patients) Electrocardiographic rhythm (no. of patients) LVHon electrocardiographic Mean LVOT gradient (mm Hg) [no. of patients]
47 (range 33-61) 1(1), II(3), III(S), IV(1) Sinus (8), AF (2)
All 39 mm Hg (range 31 56)[8]; no gradient[2]
NYHA, New York Heart Association; LVH, left ventricular hypertrophy; AF, atrial fibrillation; L VOT, left ventricular outflow tract.
left lateral decubitus position and examined (after lidocaine spray was applied to the oropharynx). The transducer was then advanced farther to the esoph agus, then to the cardia of the stomach. A routine examination as described previously1 •4 •6 was per formed in all patients. In the last four patients a biplane TEE probe was used. 5 RESULTS
No complications were observed during or after the examinations. There were no arrhythmias or other problems related to the procedure. The TIE and TEE findings are summarized in Table 2. For illus tration, four cases are descriibed below.
Patient number 1 was seen for clinically stable hy pertrophic cardiomyopathy for 4 years. He was ad mitted to the hospital for sudden onset of failure of left side of the heart with rapid progression to pul monary edema and hypotension. The TIE showed the classic picture of hypertrophic obstructive car diomyopathy with moderate mitral insufficiency. TEE showed much greater degree of mitral insuffi ciency and revealed its cause, perforation of anterior mitral leaflet (Figure 1). The patient underwent mi tral valve replacement with a St. Jude prosthesis and septal myectomy. The postoperative course was un eventful and the patient is now in functional class II. On gross inspection no vegetations on the perforated anterior mitral leaflet were found. Patient number 2 was seen for 4 years with the diagnosis of hypertrophic obstructive cardiomyopa thy. Because of clinical deterioration, surgical treat ment was considered and TEE was performed to exclude the presence ofa left ventricular outflow tract membrane, which was suspected (but not estab lished) at the last TIE readings. TEE clearly showed a discrete membranous subaortic stenosis. What was considered during TIE to be a systolic anterior mo tion (SAM), was really shown by TEE to be a contact of the membrane with the anterior mitral leaflet. The motion of the mitral valve itself and of the chordae apparatus was normal. Successful membrane enucle ation was performed and the patient is in functional class I. His left ventricular hypertrophy is in re gresslon.
Volume 5 Number 2 March-Aprill992
TEE in hypertrophic cardiomyopathies
165
Patient number 3 was seen for a severe form of hypertrophic cardiomyopathy and demonstrated progressive symptoms (class III). His TIE was of poor image quality. It showed severe left ventricular hypertrophy and possible SAM but was unable to describe any further details. TEE was performed as a part of preoperative evaluation and revealed an atypical SAM beginning at end-diastole (Figure 2) and very prominent through systole, a midventricular obstruction with nearly cavity obliteration during systole, and redundant mitral valve leaflets. The pa tient underwent septal myectomy and after surgery was in functional class I. Patient number 4 had hypertrophic obstructive car diomyopathy with mitral insufficiency and mitral an ulus calcification. In September 1990 she was suc cessfully resuscitated for ventricular fibrillation. Pre operative TEE confirmed the diagnosis and revealed secondary chordae attached to the body of posterior mitral leaflet. These secondary chordae were visual ized only in TEE long-axis view (Figure 3). In March 1991 she underwent septal myectomy with mitral valvuloplasty. Preoperative TEE revealed significant residual mitral insufficiency after valvuloplasty, and this led to immediate mitral valve replacement with a St. Jude mitral prosthesis (St. Jude Medical, Inc., St. Paul, Minn.). The patient recovered unevent fully.
DISCUSSION The safety of TEE in patients with hypertrophic cardiomyopathy. Despite a certain fear of arrhyth mias or worsening of the obstruction during TEE (possible spontaneous V alsalva maneuvers during the procedure), all patients tolerated the procedure well. The preoperative evaluation of the mitral valve morphology. TEE provided more details in three patients. In one patient, it was the only method to reveal the perforation of anterior mitral leaflet. Infectious endocarditis was thought to be the cause for this perforation. However, clinical picture, lab oratory findings, and absence of vegetations during TEE and on macroscopic inspection of the valve led us to consider another possible cause: myxomatous degeneration of the leaflets and subsequent perfo ration at the site, where mechanical damage during SAM might occur. Unfortunately, the microscopic examination of the excised valve was not performed. TEE also provided us more information about pro lapse or redundancy and about regurgitant jets of mitral valve in other patients.
Atypical early SAM observed in patient No.3. Anterior mitral leaflet remains in contact with interventri cular septum from late diastole (upper panel) to early systole (middle and lower panels). TEE four-chamber view. More details in the text. LA., Left atrium; MV, mitral valve; LV, left ventricle; OT, outflow tract; R V, right ventricle.
Figure 2
Perioperative assessment. Intraoperative TEE can be useful for assessment of the surgical results of septal myectomy and mitral valvuloplasty. Patient number 4 is an example; TEE influenced the im mediate operative management, and thus clinical outcome. Misinterpretation of the subaortic mem brane as SAM during TTE. Patient number 2 was seen under the diagnosis of hypertrophic obstructive cardiomyopathy. During TIE, concentric left ven tricular hypertrophy and SAM were described re
Journal of the American Society of Echocardiography
166 Widimsky et al.
Figure 3 Secondary chordae from posterior wall (PW) to posterior mitral leaflet. PM, Pap illary muscle; LA, left atrium; LV, left ventricle; A W, anterior wall.
Table 2 Transthoracic and transesophageal echocardiographic data of the patients (n SAM Mitral valve MI by color Doppler Max. myocardial thickness LVOT diameter LV diameter diastolic Image quality LA diameter
=
10)
TIE
TEE
8 (1 false positive) 7 normal, 2 redundant, 1 prolapse 6 26mm 15 mm 4lmm Good in 7, poor in 3 51 mm
7, LVOT membrane l 4 normal, 3 redundant, 2 prolapsing, l perforation 10 27mm 16mm 33mm Excellent in 7, good in 3 73mm
PL, Posterior leaflet; IVS, interventricular septum; LV, left ventricle; SAM, systolic anterior motion; L VOT, left ventricular outflow tract; MI, mitral insufficiency; LA, left atrium.
peatedly. Only during the last TIE was the suspicion for subaortic membrane first expressed. TEE revealed a membrane in the left ventricular outflow tract and excluded the presence of SAM. In all our patients TEE enabled more detailed description of left ven tricular outflow tract and SAM with clear clinical consequences in patient number 2. Indirect evidence for excessive mitral appa ratus size. It was recently described in pathology specimens/ in an in vitro model, 8 and in a detailed echocardiographic analysis 9 that excessive mitral valve area, elongation or both might be partly re sponsible for SAM, at least in some patients. Our observation in patient number 3 (Figure 2) is sup porting this theory in vivo. In this patient the anterior
mitral leaflet remained in contact with the interven tricular septum from end-diastole to early systole, at peak systole it further moved towards the aortic valve, thus showing an atypical motion (continuous ante rior motion of the anterior mitral leaflet with a max imum at mid-systole). We suggest the theoretic ex planation for this observation might be the excessive size of mitral valve or chordae with respect to the left ventricular cavity size. In the other six patients with SAM, this pattern was not observed. Biplane TEE. The use of biplane TEE in four patients enabled more detailed evaluation of the left ventricle, its outflow tract, and mitral regurgitant jets. Visualization of secondary chordae 10 was better in the long-axis view (Figure 2).
Volume 5 Number 2 March-Aprill992
TEE in hypertrophic cardiomyopathies
Conclusions
The data from this small group of patients with hy pertrophic cardiomyopathy suggest that TEE pro vides more detailed information about left ventricular outflow tract (including detailed visualization of SAM) and about mitral valve morphology and re gurgitant jets. TEE should be performed in all pa tients with hypertrophic obstructive cardiomyopathy before surgery to assess detailed morphology of mi tral valve and left ventricular outflow tract. However, in patients treated medically, TIE is sufficient for the diagnosis and follow-up.
4.
5.
6. 7.
8.
REFERENCES l. Gussenhoven EJ, Taarns MA, Roelandt J, et al. Oesophageal
echocardiography. lnt J Card Imaging 1987;2:231-9. 2. Stanley TE, Rankin JS. Idiopathic hypertrophic subaortic ste nosis and ischemic mitral regurgitation: the value of intra operative transesophageal echocardiography and Doppler color flow imaging in guiding operative therapy. Anesthe siology 1990;72:1083-5. 3. Mugge A, Daniel WG, Wolpers HG, Klapper JW, Lichtlen
9.
10.
167
PR. Improved visualization of discrete subvalvular aortic ste nosis by transesophageal color-coded Doppler echocardiog raphy. Am Heart J 1989;117:474-5. Seward JB, Khandheria BK, Oh JK, et al. Transesophageal echocardiogtaphy: technique, anatomic correlations, imple mentation, and clinical applications. Mayo Clin Proc 1988;63:649-80. Seward JB, Khandheria BK, Edwards WD, Oh JK, Freeman JK, TajikAJ. Biplanar transesophageal echocardiography: an atomic correlations, image orientation, and clinical applica tions. Mayo Clin Proc 1990;65:1193-213. Schiller NB, Maurer G, Ritter SB, et al. Transesophageal echocardiogtaphy. JAM Soc ECHOCARDIOGR 1989;2:354-7. Klues HG, Dollar AL, Roberts WC, Maron BJ. Diversity of mitral valve structure in patients with hypertrophic cardio myopathy: evidence for a primary mitral valve abnormality. Circulation 1990;82:III-293. Lefebvre X, Cagniot A, Yoganathan AP, Weyman AE, Levine RA. Reproduction of systolic anterior motion of the mitral valve in a pulsatile flow model. Circulation 1990;82:III-396. Mora E. Ten Cate FJ, Leonard JJ, Hugenholtz PG, Roelandt J. Genesis of systolic anterior motion of the mitral valve in hypertrophic cardiomyopathy: an anatomical or dynamic event? Eur Heart J 1987;8:1312-21. Chauvaud S, Carpentier A, Deloche A, et al. Chirurgie re constructrice de l'insiffisance mitrale acquise de !'enfant. Arch Mal Coeur 1980;73:1365-71.