International Journal of Cardiology, 31 (1991) 223-234 0 1991 Elsevier Science Publishers B.V. 0167-5273/91/$03.50 ADONIS 016752739100127W
Value and limitations of transesophageal echocardiographic monitoring during percutaneous balloon mitral valvotomy Angelo Ramondo ‘, Fabio Chirillo I, Maurizio Dan 2, Giambattista Isabella ‘, Raffaele Bonato ‘, Carlo Rampazzo I, Renato Razzolini ‘, Lorella Andriolo ‘, Alessandro Mazzucco 3 and Raffaello Chioin ’ ’ Curdrac Catheterisation Unit, Depariment of Cardiology; Institutes of3 Anaesthesiologv and -’ Curdrovusculur Surgqv. University of Padova. Padova, Ituh (Received
18 June 1990; revision
Ramondo A, Chirillo F, Dan M, Isabella G, Bonato R, Rampazzo C, Razzolini R, Andriolo A, Chioin R. Value and limitations of transesophageal echocardiographic monitoring during balloon mitral valvotomy. Int J Cardiol 1991;31:223-234.
L, Mazzucco percutaneous
To determine the utility of transesophageal echocardiographic monitoring during percutaneous balloon mitral valvotomy, we analyzed data from 40 consecutive patients who had been randomly assigned to undergo balloon mitral valvotomy under transesophageal echocardiographic guidance or without echo. All procedures were carried out under general anaesthesia. The completion rate (100% vs 73’S), the procedure time (108 f 28 min vs 65 f 18 min), the X-ray exposure time (62 f 13 vs 33 f 12 min), resulted significantly (P < 0.001) more favorable in the echo-monitored patients. Moreover, a lower rate of major complications (cardiac tamponade, large residual atria1 shunting, and severe mitral regurgitation) was noted in the echo-monitored patients. The achieved final area of the mitral valve did not differ significantly between the two groups. From an evaluation of results as a whole, %% of the echo-monitored procedures were successful, whereas only 40% of the procedures conducted without echocardiographic control achieved a satisfactory final result in absence of major complications. We conclude that transesophageal echocardiography is a safe, effective, and valuable tool to monitor each step of balloon mitral valvotomy in order to shorten the time of the procedure, and to improve the results of this complex interventional catheterization technique. Key words: Transesophageal Color-Doppler flow imaging
Correspondence to: A. Ramondo. MD. Servizio di Emodinamica-Policlinico Universitario, Via N. Giustiniani 2, 35128 Padova, Italy. Work supported by: Associazione per lo Studio dell’ Emodinamica e della Cardiologia. Padova, Italy.
Introduction As an alternative to replacement of the mitral valve, transvenous mitral commissurotomy by bal-
loon catheter was first introduced in 1984 by Inoue et al. [l]. Then, in 1985, balloon valvotomy was first applied to young adult patients with rheumatic mitral stenosis . The excellent shortand mid-term results in terms of reduction of gradient and increase in the area of the mitral valve, along with the absence of major complications, encouraged a more extensive application of this technique [3,4], such that it is now regarded as an effective alternative to close- and open-heart surgery [5,6]. The procedure is, nonetheless more complex and time-consuming than other interventional catheterisation techniques such as aortic valvotomy or coronary angioplasty. It requires a transseptal catheterization, the enlargement of the opening in the atria1 septum in order to facilitate the passage of the larger valvotomy balloon, the precise positioning of this latter balloon across the mitral orifice, one or more inflations, and the final detection of complications and evaluation of results. Transesophageal echocardiography, providing as it does excellent visualization of both atriums and of the mitral valvar apparatus and the left ventricle represents a valuable imaging technique to monitor each step of mitral valvotomy. This might then permit shortening the time of the procedure and improve its result. To test this hypothesis we have performed transesophageal echocardiography during 25 procedures, and we have compared them with 15 valvotomies performed without transesophageal echocardiographic monitoring. TABLE
Patient population The study group consisted of 40 consecutive patients who underwent percutaneous balloon mitral valvotomy at the catheterization laboratory of Padova University between January 1989 and March 1990. Patients were randomised to undergo balloon mitral valvotomy under trasesophageal echocardiographic monitoring, or to undergo the procedure without echo. The two groups were matched with respect to age, sex, type of technique, hemodynamics, echo-score  and experience of the operator (Table 1). All patients had previously undergone cardiac catheterization and transthoracic echo that had documented severe mitral stenosis with absent or mild mitral regurgitation. All patients gave their informed consent to percutaneous mitral valvotomy. There were 10 males and 30 females (mean age 56 + 15 years; range 27-78 years). Four patients were in sinus rhythm, and 36 patients in atria1 fibrillation. Before valvotomy, 9 patients were in New York Heart Association functional class IV, 22 in class III, and 9 in class II. Three patients had previously undergone surgical mitral commissurotomy, and had subsequently developed severe restenosis. Percutaneous
balloon mitral valvotomy
After induction of general anaesthesia, right and left heart catheterisation was performed by
Clinical and hemodynamic findings in 25 patients who underwent percutaneous balloon mitral valvotomy under echocardiographic monitoring and in 15 patients in whom the procedure was performed without echomonitoring.
No. of patients Female/male Age (yrs) NYHA class III-IV MMG (mmHg) MVA (cm2) PVR (dynes . set . cm Echo-score Lock technique Inoue technique
MMG = mean mitral gradient; resistance; TEE = transesophageal
‘25 19/6 58 + 15 20 (80%) 18*8 0.8 + 0.3 581 i 94 8.7 + 2.1 12 (48%) 13 (52%)
15 11/4 54* 17 11(73%) 16 + 10 0.7 * 0.3 556 f 110 9.1 k 1.8 8 (53%) 7 (47%)
ns ns ns ns ns ns
MVA = mitral valve area; NYHA echocardiography; Yrs = years.
PVR = pulmonary
means of a percutaneous technique via the left femoral vessels. After prevalvotomy measurements were made, transseptal catheterization was accomplished from the right femoral vein with a 8F Mullins transseptal sheath and dilatator, and Brockenbrough needle. Single balloon valvotomy was performed in two patients as described by Lock et al. ; double balloon valvotomy was performed in another 18 patients using a modification  of the technique originally described by Al Zaibag et al. . In the remaining 20 patients the Inoue technique [l] was used. After valvotomy, all haemodynamic measurements were repeated. Cardiac output was measured either with the thermodilution or Fick method. The Gorlin equation  was used for calculation of mitral valve area. A diagnostic oxygen run was performed to assess the left-to-right shunt at atria1 level. Cine left ventriculography in the 30 right anterior oblique projection was performed to detect mitral regurgitation and to assess left ventricular function after valvotomy. Cine left atriography in the 30 left anterior oblique projection was performed to detect angiographic evidence of interatrial shunting. After the procedure, all patients were admitted to the Intensive Care Unit where they stayed for a mean 12 hour period. Transesophageal
All examinations were performed using a 5MHz phased array transducer with incorporated color coded Doppler (64 elements, maximal sector angle 90, Hewlett Packard model 21362A) mounted at the tip of a modified gastroscope (distal tip diameter 11 mm). The endoscope was first advanced into the esophagus approximately 25 to 30 cm from the incisors. At this distance, the transducer was placed posterior to the left atrium [lo]. Gains were set high in order to detect left atria1 spontaneous echo contrast, defined as dynamic clouds of echoes curling up slowly in a circular or spiral shape within the atrial cavity [ll]. After setting the gains lower, by tilting the tip superiorly and by slightly withdrawing the transducer, serial scans of the left atria1 appendage were obtained in order to detect left atrial thrombi
. With further advancement of the endoscope into the esophagus (approximately 30 cm from the incisors), four-chamber scans of the heart were obtained. This view was used to visualize the mitral valve apparatus, the presence and grade of mitral incompetence, and the interatrial septum. In order to achieve a quantitative assessment of mitral valve area, transgastric short-axis scans of the left ventricle at the level of the mitral orifice were performed. Whenever the image was sufficiently clear, the anatomic area of the mitral valve was measured by direct planimetry in the standard manner [13,14]. The first, and the most delicate, step of mitral valvotomy is transseptal catheterization. To minimize the risk that the needle and catheter will pierce a structure adjacent to the atrial septum, the puncture should be made as near as possible to the oval fossa. A comprehensive assessment of the rim of the fossa and its floor was achieved by combining the four-chamber and basal short-axis views. The transseptal needle was first leant against the right aspect of the atria1 septum. Once the operator had made sure by echo imaging of the proper position of the needle, the septum was punctured (Fig. 1). The dilatation of the atria1 septal opening was accomplished by means of the Mullins balloon. It often leant against the aortic leaflet of the mitral valve, hindering its closure (Fig. 2) and thus producing a transient moderate mitral regurgitation. The balloon was subsequently withdrawn across the atria1 septum, where it was inflated. The third step of mitral valvotomy is positioning the balloon across the mitral valvar orifice. Because of the proximity of the esophageal probe to the mitral apparatus, echocardiography could easily demonstrate whether the balloon had been placed in an inadequate (Fig. 3A) or proper (Fig. 3B) position. At the end of the procedure, after assessing the final area of the mitral valve, the residual atria1 shunt was visualised by color-Doppler interrogation of the atria1 septum, and the residual septal tear was measured, as previously described . Transesophageal color-Doppler interrogation of the mitral regurgitant flow was obtained with only a wire across the mitral valve, either before and after the procedure. In most cases, the left atrium could not be entirely visualized; so that the method
1. Modified four-chamber scan. The transseptal needle (arrow) has been placed in the left atrium after puncturing septum just above the oval fossa. (la = left atrium; Iv = left ventricle; ra = tight atrium; rv = right ventricle.)
the ratio of the maximal area of the jet to that of the left atrium [16,17] could not be used. In order to evaluate the variation of mitral insufficiency, therefore, we have used a modification of the above method, comparing the ratio between the maximum area of the jet and the largest visible area of the left atrium (using the same left atria1 scan) before and after valvotomy. using
Statistical methods All continuous values are expressed as mean k standard deviation. A P value < 0.05 was considered significant. Results Patients not undergoing echocardiographic
Among the 15 patients in whom mitral valvotomy was attempted without echo-monitoring, in 4 the procedure could not be completed due to
complications of transseptal catheterization. Two patients with hugely enlarged right atriums had cardiac tamponade that was successfully treated in the catheterization laboratory. One patient had severe hypotension and bradycardia treated by intravenous atropine. The latter drug provoked sinus tachycardia which, hindering left atria1 emptying, caused pulmonary edema. An elderly patient with marked kyphoscoliosis had recurrent episodes of severe hypotension along with elevation of the ST segments in the lateral and inferior leads, whenever the guidewire entered the left atrium. These episodes were considered the consequence of spastic occlusions of the dominant circumflex artery, mechanically induced by the guidewire leaning against the atria1 wall. The procedure was interrupted and the patient recovered in few minutes. All these four patients had repeat and successful valvotomy under transesophageal echocardiographic monitoring. They have not been included in the echo-group so as to avoid crossover and selection bias. The mean procedure time
view. The Mullins catheter Fig. 2. Four-chamber producing moderate mitral regurgitation.
leans against the aortic leaflet of the mitral (la = left atrium; Iv = left ventricle; ventricle.)
resulted 108 + 28 min, and the X-ray exposure was 62 f 13 min (Table 2). Most time was spent on transseptal catheterization. In four patients with large left atriums and small left ventricles, positioning the balloon across the mitral valvar orifice was very problematic. In three cases, the Inoue balloon had to be changed to a trefoil balloon because of its failure to cross the mitral valve. In five patients, it was uncertain whether an effective dilatation had been achieved after several inflations (there was no “washing” of the balloon, no stable fluoroscopic position of the balloons anterior to the atrioventricular groove, and no change in balloon mobility after inflation). The balloons were retracted into the left atrium and the wedge and left ventricular pressures were recorded with only a guidewire across the mitral valve. In three of these patients a significant residual atria1 shunt (Qp/Qs > 1.4) was calculated. In
valve hindering its closure and I.hus ra = right atrium; rv = right
6 patients, mitral valvotomy resulted in a significant increase in the area of the mitral valve in absence of major complications (Table 2). Two procedures were complicated by severe mitral regurgitation that required emergency replacement of the valve. Echo-monitored
All transesophageal echocardiograms were performed without complications. Left atrial spontaneous echo contrast was evident in 21 patients before dilatation. During inflation it became more evident in all patients in whom it was still present, and it appeared in 4 patients in whom it had not previously been visible. After dilatation, it persisted in 18 patients who had undergone successful valvotomy. Only in one case did we detect left atria1 thrombus not previously detected by trans-
view. The valvotomy balloon is inflated in an inadequate position, leaning against the mural leaflet of the Fig. 3. Four-chamber mitr al valve (A). After deflation, the balloon has been advanced into the left ventricle and properly inflated across the mitral v,alve echocontrast is evident. (LA = left atrium; LV = left ventricle; RA = right atri urn; 09. In both panels, massive left atria1 spontaneous RV = right ventricle.)
Fig. 4. Five-chamber scan. The dilating balloon is kept at a sufficient distance from the free wall of the left atrium where a massive thrombus is evident (black arrows). (Ao = aorta; LA = left atrium; LV = left ventricle: RA = right atrium: RV = right ventricle.)
thoracic echocardiography. This generally represents a contraindication to balloon mitral valvotomy. Nevertheless, the procedure was continued in order to provide clinical benefit to the patient, who was in bad general condition and had been previously not considered suitable for valvar reTABLE
Results of percutaneous balloon mitral valvotomy in 25 patients in whom the procedure was performed under transesophageal echocardiographic monitoring and in 15 patients who underwent the procedure without echo-monitoring
No. of patients Completed procedures Procedure time (min) Fluoroscopy time (min) Final MVA (cm*) AS (Qp/Qs ’ 1.4) Severe MR
25 25 (100%) 65518 33 f 12 2.2+0.5 0 1
15 11(73%) 108 + 28 62&13 2.1+0.3 3 2
c 0.001 < 0.001 < 0.001 NS
AS = atria1 shunt; MR = mitral regurgitation; MVA = mitral valve area; TEE = transesophageal echocardiography.
placement due to severe chronic obstructive lung disease. Guides and catheters were manipulated very gently and carefully under continuous echocardiographic monitoring (Fig. 4). The procedure was successful and there was no systemic embolisation, as demonstrated by an accurate physical examination and a brain computed tomography. An optimal visualization of the region of the oval fossa was achieved in all patients, and it greatly facilitated the delivery of the transseptal catheter and needle, especially in patients with enlarged right atriums. Technically satisfactory images of the orifice of the mitral valve suitable for planimetry could not be obtained either before or after the procedure in 16 patients (64%). Positioning the balloon across the valvar orifice was difficult in 10 patients with large left atriums and small left ventricles. In these patients, the balloon often leant asymetrically against one leaflet of the valve and could not be advanced farther into the left ventricle (Fig. 3A). In all these patients, the balloon was partly inflated in the left atrium and
Fig. 5. Four-chamber
view. A large tear with sheared edges is evident in the atria1 septum after withdrawing equipment. (LA = left atrium; LV = left ventricle; RA = tight atrium: RV = right ventricle.)
subsequently gently advanced into the left ventricle under echo monitoring. As soon as the balloon entered the orifice of the valve symetrically, it was further inflated until it produced complete occlusion (Fig. 3B). There was no failure to cross the orifice of the mitral valve, and the use of echocardiography greatly reduced the time devoted to this maneuvre. The total time of the procedure was 65 + 18 min, and the time of exposure to X-rays was 33 f 12 min. Of the procedures, 24 were successful and produced significant hemodynamic improvement (Table 2). Transesophageal echocardiography detected an increase in mitral regurgitation by one grade in 5 patients and by two grades in one patient. Angiography provided the same results in all but one patient who had mild mitral insufficiency, previously evaluated as moderate by color-Doppler. Oximetric and angiographic evaluations detected trivial atria1 shunting in all cases. Transesophageal echocardiography detected small interatrial turbulent jets in all cases. The tear of the atria1 septum was smaller than 0.2 cm in 24 cases. In one case there, was a 0.4 cm
large tear in the atria1 septum was no evidence of shunting.
all the valvoplasty
(Fig. 5) but there
Discussion Echocardiography has been increasingly used as a technique of choice for imaging when monitoring interventional procedures. In many instances, it has provided very helpful adjunctive information to fluoroscopy in performing coronary angioplasty [l&19], aortic and mitral valvotomy . Most studies, however, have been performed using transthoracic echocardiography. This technique has two main drawbacks: firstly, it does not always obtain satisfactory images, particularly when patients are recumbent on the catheterization bed and especially if they have difficult windows due to obesity, obstructive lung disease, and other factors. Secondly, the sonographer, standing very close to the chest of the patient. is exposed significanting to X-rays. Moreover, he or she may contaminate the sterile instruments while manipulating the probe. Transesophageal echo-
cardiography does not present such limitations, since the 1.3 m-long esophageal probe provides highly-defined images in all patients, and allows the interposition of a radioproof shield between the source of X-rays and the operator. Drawbacks monitoring
The main drawback of transesophageal echocardiography is the need for general anesthesia, since the probe is poorly tolerated by patients who are awake while undergoing interventional procedures. General anesthesia has dramatically improved the tolerance to the procedure. It involves, nonetheless, an unpredictable but not negligible risk to the patient. In addition, it requires extra time in the catheterization laboratory, and necessitates monitoring in the Intensive Care Unit after the procedure. In our experience, these drawbacks proved more potential than real. The induction of anesthesia was carried out after introducing arterial and venous catheters. While the anesthetist was monitoring the patient for anesthesia, the catheter operator was preparing the valvotomy apparatus. The loss of time in the catheterization laboratory, therefore, was very short. Furthermore, we did not make too much of the extracharge of Intensive Care Unit monitoring, because in our institution all patients after any uncomplicated interventional procedure stay a mean 12 hour period in the Intensive Care Unit. So far, we have had no problems with general anesthesia. Our study does not permit, however, the establishment of whether the risk of general anesthesia is warranted by better results of mitral valvotomy using transesophageal echocardiography. Another potential drawback of transesophageal echocardiographic monitoring is the X-ray exposure to echo-operators. Over the period of study, monthly dosimetric determination on echo-operators who had also performed diagnostic catheterizations did not significantly differ from those of previous months when mitral valvotomy had not been performed. The distance between the sonographer and the patient and the interposition of a radioproof shield seem to warrant sufficient radioprotection. More precise determinations are needed,
nonetheless, to obtain an exact assessment of the exposure to X-rays of both echo- and catheter-operators. Finally, cross-sectional transesophageal echocardiography using a single plane provides only cross-sectional views of the heart. Many expectations are addressed to biplane transesophageal probes, which may offer the opportunity of a localization in three dimensions of a wire, needle or catheter that is viewed at present only in two dimensions. Advantages monitoring
Transesophageal echocardiography can visualize each step of balloon mitral valvomtomy, since it provides clear imaging of all the structures of the heart where the most critical steps of the procedure take place. Transesophageal echocardiography has been of great value in performing transseptal catheterisation, especially in patients with spinal deformities or hugely enlarged right atriums. In these patients, transseptal puncture is more problematic, since localization of the oval fossa is more difficult and time consuming . For localization, a pigtail catheter is usually placed in the ascending aorta just above the leaflet of the aortic valve and biplane (anteroposterior and lateral) fluoroscopic monitoring is used . This greatly increases the exposure to X-rays of both patients and operators, and still does not provide, in all cases, a precise localization of the oral fossa. In our experience, transesophageal echocardiography has optimized transseptal catheterization in all cases and significantly reduced the times of exposure to X-rays and the overall time devoted to this highly delicate maneuvre. Transesophageal monitoring allowed the accomplishment of one procedure considered at high risk because of left atria1 thrombosis. In spite of the fact that this procedure did not involve significant complications, we would caution against the routine use of mitral valvotomy for the management of mitral stenosis in the presence of left atria1 thrombus. Under these circumstances, mitral valvotomy should be performed only if patients have no surgical alternative. Atria1 septal thrombosis, or pedunculated thrombus, should be regarded as an
absolute contraindication to mitral valvotomy because they involve an enormous thromboembolic risk. In contrast, our case has demonstrated that the potential contact of catheters with thrombus in the lateral wall of the left atrium and appendage can be avoided when mitral valvotomy is properly performed under echocardiographic monitoring. Spontaneous left atria1 echocontrast has been said to be an indicator for increased thromboembolic risk in patients with disease of the mitral valve . The enhancement of echocontrast observed during inflations may be due to the transient slow state of the blood  determined by balloon occlusion of the mitral orifice. The cause of persisting left atria1 echocontrast after successful valvotomy, however, is not clear. Serial postvalvotomy transesophageal echocardiograms and clinical checks are needed to clarify the nature and the clinical implications of this phenomenon. Transesophageal echocardiography has been very effective in providing, either directly or indirectly, on-line assessment of both result and complications. As additional inflations may improve the area of the valve but involve an adjunctive risk of disruption, the assessment of the gradient and regurgitation across the valve after each inflation is of critical importance in decisionmaking during the procedure. Unfortunately, such evaluations cannot be made with all the dilation equipment across the mitral orifice. Under these circumstances, hemodynamic assessment either by catheterization or by echocardiography is unreliable because of fictitious mitral gradients and regurgitant jets. Pulling the balloons back into the left atrium is also an uncertain maneuvre, because one cannot see at fluoroscopy the left atrial aspect of the septum and, therefore, cannot avoid pulling balloons back into the atria1 septum. The assessment of the post-valvotomy gradient and regurgitation with only a wire across the mitral valve and the balloon placed safely back into the left atrium (by transesophageal imaging), was always achieved without complications, since there was neither return of the balloons into the right atrium nor large residual atrial shunting. These complications were more frequent in the patients who were not monitored echocardiographically. When comparing the results of the two groups (Table 2) transesopha-
geal echocardiography seems to have failed the ambitious goal to improve the results of mitral valvotomy, since the final area of the mitral valve does not significantly differ between the two groups. By an overall assessment, in contrast, it can be noted that 24 of the 25 (96%) procedures conducted under echo control were successful, whereas only 6 of the 15 (40%) not monitored achieved a satisfactory result in absence of major complications. In conclusion, therefore, transesophageal echocardiography represents a safe, effective and valuable tool with which to monitor each step of balloon mitral valvotomy. This tool seems more valuable in centers performing a small number of procedures, from which a higher rate of complications has been reported , or when performing balloon valvotomy in patients who are more likely to have complicated  or failed valvotomy because of anatomic alterations. If the application of general anesthesia to all patients undergoing balloon mitral valvotomy is considered too risky, transesophageal echocardiographic monitoring may be reserved for these patients, so as to improve the overall success rate of this interventional catheterisation technique.
References Inoue K, Owaki T, Nakamura T. Kitamura F, Miyamoto N. Clinical application of transvenous mitral commissurotomy by a new balloon catheter. J Thorac Cardiovasc Surg 1984;87:394-402. Lock JE, Khalilullah M, Shirivastava S, Bahl V, Keane JF. Percutaneous catheter commissurotomy in rheumatic mitral stenosis. N Engl J Med 1985;313:1515-1518. Vahanian A, Slama M, Cormier B, Michel PL, Savier CH, Acar J. Valvuloplastie mitrale percutanee chez l’adulte. Arch Ma1 Coeur 1986;13:1896-1902. Rediker DE, Block PC. Abascal VM, Palacios IF. Mitral balloon valvuloplasty for mitral restenosis after surgical commissurotomy. JACC 1988;11:252-256. Vahanian A, Michel PL, Cormier B et al. Results of percutaneous mitral commissurotomy in 200 patients. Am J Cardiol 1989;63:847-852. Palacios I, Block PC, Brandi S et al. Percutaneous balloon valvotomy for patients with severe mitral stenosis. Circulation 1987;75:778-784. Wilkins GT, Weyman AE. Abascal VM, Block PC, Palacios IF. Percutaneous mitral valvotomy: an analysis of echocardiographic variables related to outcome and the mechanism of dilatation. Br Heart J 1988;60:299-308. Zaibag M, Ribeiro PA, Kasab S, Fagih MR. Percutaneous
double balloon mitral valvotomy for rheumatic mitral valve stenosis. Lancet 1986;1:757-761. Gorlin R, Gorlin SG. Hydraulic formula for calculation of the area of the stenotic mitral valve, other cardiac valve, and central circulatory shunts. Am Heart J 1951;41:1-29. Seward JB, Khandheria BK, Oh JK et al. Transesophageal echocardiography: technique, anatomic correlations, implementations. and clinical applications. Mayo Clin Proc 1988;63:649-680.B Beppu S. Nimura Y. Sakakibara H. Smoke like echo in left atria1 cavity in mitral valve disease: its features and significance. J Am Cull Cardiol 1985:6:744-749. Aschenberg W. Schluter M. Kremer P, Schroeder E. Siglow V. Bleifeld W. Transesophageal two-dimensional echocardiography for the detection of left atrial appendage thrombus. J Am Co11 Cardiol 1986;7:163-166. Wann LS. Weymann AE. Feigenbaum H, Dillon JC, Johnston KW, Eggleton RC. Determination of mitral valve area by cross-sectional echocardiography. Ann Intern Med 1978:88:337-349. Henry WL. Griffith JM, Michaelis LL, Epstein S. Measurement of mitral orifice area in patients with mitral valve disease by real time, two dimensional echocardiography. Circulation 1975:51:827-831. Yoshida K, Yoshikawa J, Akasaka T et al. Assessment of left to right atria1 shunting after percutaneous mitral valvuloplasty by transesophageal color Doppler flow mapping. Circulation 1989;80:1521-1526. Switzer FD, Nanda NC. Color evaluation of valvular regurgitation. Echocardiography 1985;2:533-542. Mohr-Kahaly S. Erbel R, Zenker G et al. Semiquantitative grading of mitral regurgitation by color-coded Doppler echocardiography. Int J Cardiol 1989;23:223-230.
18 Griffin B, Crick JCP, Timmis AD, Sowton E. Evaluation of myocardial ischemia during percutaneous transluminal coronary angioplasty. Br Heart J 1986;55:512. 19 De Bruyne B. Lerch R. Meier B. Schlaepfer H. Gabathuler J. Rutishauser W. Doppler assessment of left ventricular diastolic filling during brief coronary occlusion. Am Heart J 1988:117:629-635. 20 Monaghan MJ, Chambers JB. Jackson G, Jewitt DE. The role of echo Doppler and color flow before. during and after mitral valvuloplasty (abstract). Eur Heart J 1988:9 (suppl 11);54. 21 Ross JR. Consideration regarding the techmque for transseptal left heart catheterization. Circulation 1966;34:391396. 22 Cheng TO. Useful landmark in transseptal left heart catheterization. Cathet Cardiovasc Diagn. 1988;14:71. 23 Daniel WG. Nellesen IJ, Schroeder E et al. Left atrial spontaneous echo contrast in mitral valve disease: an indicator for an increased thromboembolic risk. J Am Coil Cardiol 1988;11:1204-1211. 24 Sigel B, Coelho JCU. Spigos DG et al. Ultrasonography of blood during stasis. Invest Radio1 1981; 16:71~ 76. 25 Herrmann HC, Kleaveland P. Hill JA et al. The M-heart percutaneous balloon mitral valvuloplasty registry: initial results and early follow-up. J Am Coil Cardiol 1990;15:1221-1226, 26 Casale P. Block PC. O’Shea JP, Palacios IF. Atrial septal defect after percutaneous mitral balloon valvuloplasty: immediate results and follow-up. J Am Coil Cardiol 1990:15:1300-1304.