Tips and Pitfalls -- Mitral Valve Crossing

I. MITRAL VALVE CROSSING

Crossing Methods

Please refer to the four crossing methods in the "Valve Crossing" section under PTMC Procedures.

Stylet Reshaping (Figure 8)

Figure 8
Stylet Reshaping

Click to View Larger Image

       The J-tipped stylet with its original curve will, in most instances, steer the balloon toward and across the mitral orifice. However, when it is difficult to direct the balloon toward the mitral orifice by aligning the catheter with the orifice-apex axis (when the direct method is used), the stylet should be reshaped according to the positional relationship between the septal puncture site and the valve orifice. For example, in patients with a giant left atrium where the puncture site is often made more caudally and laterally in relation to the mitral orifice, the distal segment of the stylet can be shaped into a larger smooth curve (Figure 8) to facilitate passage of the balloon across the mitral valve. Conversely, in those with a relatively small left atrium, when the puncture site is made suboptimally, either too medially or anteriorly (in relation to the mitral valve), the stylet can be reshaped into a tighter loop (or the alternate loop method is employed).

II. BALLOON INFLATION PROCEDURES

Assure Free Balloon Movement in Left Ventricle

       One of the most dreaded complications of PTMC is the development of severe mitral regurgitation requiring surgery. Once the mitral valve has been crossed, the free movements of the partially inflated distal balloon in the left ventricle should be ascertained to prevent the disastrous consequences, i.e. rupture of chordae, papillary muscles or leaflets, stemming from its subsequent full inflation between the chordae. This is done by simultaneously pushing the catheter and pulling the stylet in opposite directions ("accordion" maneuver) to ensure that the partially inflated distal balloon slides freely along the orifice-apex axis.

Avoid Straying Among Chordal Structures

       After crossing the mitral valve, the catheter balloon may point more vertically and deviate away from the orifice-apex axis. This suggests that the catheter has strayed among the chordae. To correct this situation, the distal balloon is inflated larger to prevent the balloon from being inadvertently retracted into the atrium, and the catheter is carefully pulled back to assume a more horizontal orientation. After satisfactory alignment of the catheter with the orifice-apex axis, the catheter is advanced toward the apex, and the previously described accordion maneuver is performed before initiating the inflation procedure. Similarly, a twist in the balloon during the inflation process may also indicate that the catheter has tethered among the chordae. In this case, the inflation should be promptly aborted and the balloon repositioned.

Subvalvular Status Reassessment

       Before PTMC, mitral valvular status is determined by pre-procedural transthoracic echocardiography and fluoroscopy (for the presence of valvular calcification), and an appropriate balloon catheter is then chosen accordingly (see BALLOON CATHETER SELECTION, above). Extensive subvalvular disease has been found by various investigators to be a predictor for significant mitral regurgitation [1-5]. Because echocardiography (either transthoracic or transesophageal) often underestimates the severity of subvalvular disease [2, 3, 6, 7], severe mitral regurgitation may be created during PTMC despite the presence of an apparently favorable valve morphology. Therefore, during the actual balloon dilatations, vigilance is required to identify the presence of previously undetected severe subvalvular disease. We and others [1, 2, 8] have found other more reliable signs of significant subvalvular involvement. Even in patients in whom no severe subvalvular disease is demonstrated by pre-procedural echocardiography, when any of these signs are observed, the balloon dilatation protocol is altered accordingly as described below (see Balloon Sizing).

   Severe subvalvular disease undetected by echocardiography

       The following signs suggest or indicate the presence of severe subvalvular disease:

Difficulty in performing the accordion maneuver. This occurs because of resistance at the subvalvular level. If this difficulty is not appreciated, subsequent full inflation will be within the left ventricle as the balloon is not anchored at the mitral valve. Hence, it is the subvalvular apparatus and not the mitral valve that is dilated. Although severe mitral regurgitation may result from such an accidental subvalvular dilatation [2], the inflation is usually harmless. However, it should be promptly recognized and the balloon quickly deflated. The size of the distal balloon is then reduced during subsequent attempts at anchoring the balloon at the mitral valve.

Figure 9
Balloon Compression Signs
(Severe Subvalvular Lesions)

Cath Cardiovas Diag 1996;37:188

Click to View Larger Image

Gross indentation of the inflated distal balloon (balloon compression sign) (Figure 9). This indicates severe subvalvular disease [1,8]. As soon as compression is observed on the distal balloon, the inflation procedure is aborted and the inflation strategy reassessed.
"Balloon impasse." In cases of tight mitral stenosis, valve crossing may be difficult even when the catheter, with its distal balloon partially inflated, is properly aligned with the long axis of the left ventricle. If this occurs, the balloon size is gradually reduced until it is accommodated by the mitral orifice. In rare and extreme instances, even when the balloon is not inflated, the catheter is checked (or entrapped) at the mitral valve. This finding, which we have termed "balloon impasse," reflects resistance caused by severe obstructive subvalvular lesions [8]. In the presence of this sign, PTMC performed with the usual catheter selection and balloon sizing is likely to tear the mitral leaflets and/or chordae and thus create severe mitral regurgitation. Our experience in a limited number of patients suggests that in addition to stepwise dilatations previously emphasized, the use of smaller balloon catheters may prevent severe regurgitation [8].
Cogwheel resistance. Rarely, while withdrawing the partially inflated balloon to anchor it at the mitral valve, cogwheel resistance may be encountered. This suggests the presence of subvalvular disease.

Controlled Stepwise Dilatations

       In order to avoid or minimize the complications of severe mitral regurgitation, the selection of an appropriate balloon catheter (discussed above) and the stepwise dilatation technique are mandatory. In addition, one should be familiar with the the pressure-volume relationship and inflation limit of the balloon catheters. (Refer to the "Controlled Stepwise Dilatations" section under PTMC Procedures for details.)

    "Balloon impasse"

       This sign indicates the presence of the most severe subvalvular disease and signifies a extremely high-risk for creation of severe mitral regurgitation [1, 8]. If balloon impasse is encountered, the initial catheter is exchanged for a smaller PTMC-18 or -20 catheter to predilate the valve and the subvalvular structures, regardless of the echocardiographic findings of the mitral valve [8]. We no longer force the usual-sized balloon through the valve to the left ventricle by slenderizing and stretching the deflated balloon segment, as previously recommended [9]; nor do we recommend advancing the balloon across the mitral valve over a guide wire preplaced in the left ventricle [10]. Both maneuvers may cause the catheter to stray among the chordae, and with larger-sized balloon catheters, it is difficult or impossible for the operator to execute the precautionary "accordion" maneuver to ensure that the catheter is not tethered among the chordae.

       However, if a smaller PTMC-18 or -20 catheter also fails to cross the mitral valve with the catheter uninflated, the balloon segment of this small balloon catheter is slenderized and stretched for crossing the mitral valve into the left ventricle. Before the balloon inflation procedure, it is mandatory to exercise the "accordion" maneuver with the distal balloon slightly inflated to ensure that the balloon catheter is free in the left ventricle. This maneuver would not have been possible with larger-sized catheters. The initial inflation is then performed with the balloon diameter at its nominal size. If further dilatations are required, the catheter is exchanged for one a size larger, and stepwise dilatations are done according to the sizing method in patients with severe subvalvular lesions, as discussed above.

   Exchange for Different-Sized Balloon Catheters

       Exchange of balloon catheters is carried out for two reasons. The first, as alluded to above, is to downsize the catheter because of the "impasse" posed by severe subvalvular distortions.

       The second reason occurs in the rare instance when there is a need to upsize the balloon catheter to one that is one size larger because of inadequate hemodynamic improvement. In such a situation, before exchanging for a larger catheter, it is vital that the initial catheter's final balloon diameter be remeasured and reverified after its complete removal from the patient, particularly when it has been inflated beyond its nominal size. This precautionary exercise is essential because, not uncommonly, despite pretesting, the balloon size is smaller than what it is supposed to be after in vivo usage. When this occurs, the original balloon catheter is retested to determine the actual volume of diluted contrast in the syringe necessary to achieve maximum balloon size (as mentioned above, the Inoue balloon tolerates about 1 mm in excess of its nominal size before rupturing), the original balloon catheter is reintroduced into the patient, and the dilatation process is repeated. However, if the balloon matches its predefined size, an exchange for a larger-sized catheter is made and dilatations with the larger balloon are performed. Failing to reverify maximum balloon size before inflating a much larger balloon creates the risk of severe mitral regurgitation.

References:

Hung JS, Chern MS, Wu JJ, Fu M, Yeh KH, Wu YC, Cherng WJ, Chua S, Lee CB: Short- and long-term results of catheter balloon percutaneous transvenous mitral commissurotomy. Am J Cardiol 1991;67: 854-862.
Hernandez R, Macaya C, Bañuelos C, Alfonso F, Goicolea J, Iñiguez A, Fernandez-Ortiz A, Castillo J, Aragoncillo P, Aguado MG, Zarco P: Predictors, mechanisms and outcome of severe mitral regurgitation complicating percutaneous mitral valvotomy with the Inoue balloon. Am J Cardiol 1992;70:1169-1174.
Feldman T, Carroll JD, Isner JM, Chisholm RJ, Holmes DR, Massumi A, Pichard AD, Herrmann HC, Stertzer SH, O'Neill WW, Dorros G, Sundram P, Bashore TM, Ramaswamy K, Jones LS, Inoue K: Effect of valve deformity on results and mitral regurgitation after Inoue balloon commissurotomy. Circulation 1992;85:180-187.
Vahanian A, Michel PL, Cormier B, Vitoux B, Michel X, Slama M, Sarano LE, Trabelsi S, Ismail MB, Acar J: Results of percutaneous mitral commissurotomy in 200 patients. Am J Cardiol 1989;63:847-852.
Sadee AS, Becker AE: In vitro balloon dilatation of mitral valve stenosis: the importance of subvalvar involvement as a cause of mitral valve insufficiency. Br Heart J 1991;65:277-279.
Rittoo D, Sutherland GR, Currie P, Starkey IR, Shaw TRD: The comparative value of transesophageal and transthoracic echocardiography before and after percutaneous mitral balloon valvotomy: A prospective study. Am Heart J 1993;125: 1094-1105.
Levin TN, Feldman T, Bednarz J, Carroll JD, Lang RM: Transesophageal echocardiographic evaluation of mitral valve morphology to predict outcome after balloon mitral valvotomy. Am J Cardiol 1994;73:707-710.
Lau KW, Hung JS: "Balloon impasse" - A marker for severe mitral subvalvular disease and a predictor of mitral regurgitation in Inoue-balloon percutaneous transvenous mitral commissurotomy. Cathet Cardiovasc Diagn 1995;35:310-319.
Inoue K, Hung JS: Percutaneous transvenous mitral commissurotomy (PTMC):The Far East experience. In Topol EJ (ed): "Textbook of Interventional Cardiology." Philadelphia: W.B. Saunders Co., 1990, pp 887-899.
Meier B: Modified Inoue technique for difficult mitral balloon commissurotomy. Cathet Cardiovasc Diagn 1992;26:316-318.

Balloon "Popping" to the Left Atrium

       When the mitral valve has already been enlarged by dilatations, the balloon may occasionally slip into the left atrium during subsequent inflations with larger balloon diameters. To prevent the latter from occurring, the stylet is advanced far into the balloon segment to stiffen the catheter, and before the catheter is retracted to anchor the balloon at the orifice, the distal balloon is inflated to a diameter slightly larger than the previous one. As soon as the balloon assumes an hourglass configuration, the catheter is advanced slightly to prevent it from jerking out into the left atrium, and full balloon expansion is then executed. With this extra dilatation, although the mitral gradient may be unchanged, further shortening of the A₂ - opening snap interval and enhanced splitting of the commissures, as assessed by echocardiography are often observed.

       The balloon "popping" signals enlargement of the mitral orifice with wide splitting of the commissures. It is usually encountered in patients with pliable, noncalcified valves and foretells excellent PTMC results. However, suboptimal hemodynamic results are occasionally observed despite the balloon "popping" sign, especially in the presence of atrial fibrillation. In these cases, although the mitral valve with split commissures can be forced to accommodate the fully inflated balloon, the effective mitral valve area is, in reality, limited by the thickened and stiff leaflets, and by ineffective atrial contractions in the beating heart.

Minimizing Atrial Septal Injury (Figure 10)

       Inherent in the antegrade PTMC approach is the creation of an atrial septal defect. Fortunately, most of these defects are small and of no clinical consequence and they tend to close spontaneously with time [1-5]. The Inoue balloon catheter, compared to the double-balloon system, has a relatively lower profile, does not require a 5 mm or 8 mm balloon to predilate the atrial septum, and has the unique ability to be stretched. These salutary features probably account for the lower incidence of atrial septal defect [6] following Inoue PTMC. Nevertheless, significant atrial shunts (defined as a pulmonary-to-systemic flow of > 1.3:1) ranging from 3-15% have been reported by some investigators [3, 7-10]. In our experience, a major negative determinant of the defect is the degree of resistance encountered during atrial septal puncture; this is probably related to the thickness of the punctured septum.

Figure 10
Minimizing Atrial Septal Injury

Click to View Larger Image

To minimize the occurrence of these defects and to avoid septal avulsion, a number of precautionary steps should be adopted. First, at the beginning of the valve inflation procedure, the catheter balloon free in the left ventricle (Figure 10, A) is gently pulled back (Figure 10, B) to the mitral valve position. After the balloon has attained its hourglass configuration and is securely anchored at the mitral valve (Figure 10, C), the distal segment of the catheter shaft (between the septal puncture site and the balloon) should be allowed to take on a gentle curve by releasing the tension exerted on the balloon catheter by a gentle push (Figure 10, D). Second, it is mandatory to adhere to the standard practice of balloon slenderization during balloon passage across the septum (on both entry into and withdrawal from the left atrium). Third, before removing the stretched balloon catheter from the left atrium to the right atrium, the guide wire should be withdrawn, leaving only its soft distal floppy segment exposed. This may avoid "slicing" the septum by the stiff portion of the wire during withdrawal of the catheter/wire assembly.

References:

Fawzy ME, Ribeiro PA, Dunn B, Galal O, Muthusamy R, Shaikh A, Mercer E, Duran CMG: Percutaneous mitral valvotomy with the Inoue balloon catheter in children and adults: Immediate results and early follow-up. Am Heart J 1992;123:462-465.
Ishikura F, Nagata S, Yasuda S, Yamashita N, Miyatake K: Residual atrial septal perforation after percutaneous transvenous mitral commissurotomy with Inoue balloon catheter. Am Heart J 1990;120:873-878.
Cequier A, Bonan R, Serra A, Dyrda I, Crépeau J, Dethy M, Waters D: Left-to-right atrial shunting after percutaneous mitral valvuloplasty. Incidence and long-term hemodynamic follow-up. Circulation 1990;81:1190-1197.
Casale PN, Stewart WJ, Whitlow PL: Percutaneous balloon valvotomy for patients with mitral stenosis: Initial and follow-up results. Am Heart J 1991;121:476-479.
Desideri A, Vanderperren O, Serra A, Barraud P, Petitclerc R, Lespérance J, Dyrda I, Crépeau J, Bonan R: Long-term (9 to 33 months) echocardiographic follow-up after successful percutaneous mitral commissurotomy. Am J Cardiol 1992;69:1602-1606.
Thomas MR, Monaghan MJ, Metcalfe JM, Jewitt DE: Residual atrial septal defects following balloon mitral valvuloplasty using different techniques. Eur Heart J 1992;13:496-502.
Lau KW, Hung JS, Ding ZP, Johan A: Controversies in balloon mitral valvuloplasty: The when (timing for intervention), what (choice of valve) and how (selection of technique). Cathet Cardiovasc Diagn 1995;35:91-100.
Hung JS, Chern MS, Wu JJ, Fu M, Yeh KH, Wu YC, Cherng WJ, Chua S, Lee CB: Short- and long-term results of catheter balloon percutaneous transvenous mitral commissurotomy. Am J Cardiol 1991;67:854-862.
Kasper W, Wollschläger H, Geibel A, Meinertz T, Just H: Percutaneous mitral balloon valvuloplasty - a comparative evaluation of two transatrial techniques. Am Heart J 1992; 124:1562-1566.
Hermann HC, Ramaswamy K, Isner JM, Feldman TE, Carroll JD, Pichard AD, Bashore TM, Dorros G, Massumi GA, Sundram P, Tobis JM, Feldman RC, Ramee S: Factors influencing immediate results, complications, and short-term follow-up status after Inoue balloon mitral valvotomy: A North American multicenter study. Am Heart J 1992;124:160-166.

* Coming Soon