(Circulation. 1999;99:793-799.)
© 1999 American Heart Association, Inc.
Clinical Investigation and Reports |
From Charles Nicolle Hospital, Departments of Cardiology (A.C., H.E., R.K., G.D., C.T., S.J., G.P., B.L.) and Biostatistics (J.B.), University of Rouen, France; Apollo Hospital, Hyderabad, India (P.C.R.); G.B. Pant Hospital, New Delhi, India (R.A.); National Heart Institute (A.I.) and Al-Azhar University, Cairo, Egypt (M.E.-S.); and the Institute of Cardiology, Ahmedabad, India (S.D.).
Correspondence to Alain Cribier, MD, Department of Cardiology, Hôpital Charles Nicolle, 1 rue de Germont, 76000 Rouen, France. E-mail alain.cribier{at}chu-rouen.fr
| Abstract |
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Methods and ResultsThe device consists of a detachable metallic cylinder with 2 articulated bars screwed onto the distal end of a disposable catheter whose proximal end is connected to an activating pliers. By the transseptal route, the device is advanced across the valve over a traction guidewire. Squeezing the pliers opens the bars up to a maximum extent of 40 mm. The clinical experience consisted of 153 patients with a broad spectrum of mitral valve deformities. The procedure was successful in 92% of cases and resulted in a significant increase in mitral valve area, from 0.95±0.2 to 2.16±0.4 cm2. No increase in mitral regurgitation was noted in 80% of cases. Bilateral splitting of the commissures was observed in 87%. Complications were 2 cases of severe mitral regurgitation (1 requiring surgery), 1 pericardial tamponade, and 1 transient cerebrovascular embolic event. In this series, the maximum number of consecutive patients treated with the same device was 35.
ConclusionsThe results obtained with this new device are encouraging and at least comparable to those of current balloon techniques. Multiple uses after sterilization should markedly decrease the procedural cost, a major advantage in countries with limited resources and high incidence of mitral stenosis.
Key Words: mitral valve valvuloplasty catheters
| Introduction |
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We developed a percutaneous valvulotomy device featuring a metallic valvotome4 instead of a balloon for opening the mitral valve, whose principle is basically similar to the metallic device (Tubbs dilator) used by surgeons for closed-chest mitral commissurotomy. The main advantage of this device would be the possibility of its being reused several times without any loss of performance after proper resterilization, and thus a decreased procedural cost. Other potential interests might be the improved efficacy and tolerance of the technique resulting from the mechanical properties of the device, which are aimed at acting principally on the mitral commissures.
The objective of the study was to evaluate the safety and the immediate results of this new technique.
| Methods |
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The series included 153 patients with pure mitral stenosis and
a broad spectrum of valvular deformity considered suitable for
percutaneous valve dilation. The selection of patients
for PMMC instead of BMV was related only to the presence in the
hospital of 1 of the 3 lead authors of this article. The demographic
data are shown in Table 1
.
Contraindications to the procedure were no commissural fusion, mitral
regurgitation of Sellers grade >2, recent
embolic event, and left atrial thrombus on
transesophageal echocardiography,
which was systematically performed within 2 weeks before the
procedure.
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The procedure for using this new device was approved by the ethical committee of each institution concerned and was performed with the patient's informed consent.
Description of the Device
The device (Medicorp Inc) consists of a metallic dilator screwed
onto the distal end of a disposable catheter. The entire system is made
of 4 components, as follows.
The metallic dilator, made of stainless steel, when closed, is a cylinder 5 cm long and 5 mm wide, with a slightly tapered tip. The distal half of the dilator consists of 2 hemicylindrical bars 20 mm in length that can be opened out in parallel up to a maximum extent of 40 mm by a lever-arm system. The opening of these 2 bars leads to the separation of the commissures. Furthermore, the dilator contains an internal tube that allows the passage of a traction wire and also the recording of the distal pressures. The metallic head is screwed onto the distal end of the catheter and is detachable.
The catheter has a diameter of 13F (4.3 mm) and a length of 170 cm. Its proximal end has a connector for recording distal pressures, and it also allows connection of the activating pliers. Its distal end allows fastening of the dilator.
The metallic guidewire is made of stainless steel, with a length of 270 cm and a diameter of 0.035 in. A metallic bead 2 mm in diameter is soldered at the junction of the stiff core and the 10-cm-long floppy distal end. The guidewire is first positioned in the left ventricle; the commissurotome can then be advanced over it until the dilator crosses the mitral valve. Then, the guidewire becomes a traction system that allows the dilator to be opened. For that, the metallic bead is positioned in contact with the distal end of the dilator, and the guidewire is solidly locked into the commissurotome with a threaded fastener located on the activating pliers. Squeezing the arms of the pliers causes a backward traction of the guidewire and the metallic bead that is transmitted to the distal end of the dilator, thus forcing the distal bars to spread apart.
The activating pliers are attached to the proximal end of the catheter shaft. A manual pressure exerted on the arms of the pliers allows the dilator to open according to the mechanism described above, and the release of pressure closes the dilator. The activating pliers comprise several elements: (1) a caliper that allows the degree of opening of the bars to be altered from outside with the help of a cursor. The programmable degrees of opening are 30, 35, 37, and 40 mm; (2) a safety lock that prevents the complete closure of the dilator after the release of pressure exerted on the pliers (it holds the dilator open at 20 mm). To obtain a complete closure of the dilator after withdrawal from the mitral valve, this lock must be activated manually. This security system was designed to avoid any accidental extraction of valvular tissue; and (3) a threaded fastener, which is designed to block the metallic guidewire into the commissurotome at the time of opening.
After dilatation, the metallic dilator can be unscrewed from the catheter and can be sterilized by autoclave for reuse. The activating pliers and the guidewire can also be resterilized. Only the catheter is meant for single use.
Technique of PMMC
The technique, which is performed under local
anesthesia and mild sedation, requires a transseptal
antegrade approach. The entry site is the right femoral vein, which has
to be punctured
2 cm below the inguinal ligament to avoid hindrance
of the dilator.
A 8F Mullins catheter is used for the transseptal puncture. It is
recommended that the septal puncture be made
2 cm below the usual
site used in the Inoue technique to facilitate the trackability of the
device across the valve. Subsequently, after septal puncture, an
initial dose of heparin 2000 IU IV is administered (an additional dose
of heparin 50 IU/kg will be administered after dilation of the atrial
septum and confirmation of the absence of pericardial effusion. Both
needle and dilator are removed, leaving the Mullins sheath in the left
atrium. The left atrial pressure and the left
atrioventricular gradient are then measured. Through
the Mullins sheath, a left atrial angiogram can be performed by hand in
the 30° right anterior oblique projection: the mitral valve is
then clearly visible on the screen, and a diastolic frame
of this angiogram is frozen on a second monitor to help position the
dilator head at the time of dilation. Keeping the same projection,
a floating balloon catheter (Critikon, USCI) is advanced through the
sheath and used to cross the mitral valve. The distal end of the
balloon catheter is positioned at the apex of the left ventricle, and
the sheath is advanced over it, beyond the mitral valve orifice. The
balloon catheter is then removed, and the guidewire of the device is
advanced through the sheath in the left ventricle, the metallic bead
being positioned at midventricle, ie, clearly beyond the mitral valve
(Figure 1A
). The Mullins sheath is then
removed, and a 14F polyethylene dilator is advanced over the wire to
enlarge the atrial septum puncture site. The same maneuver is then
completed by additional dilation with an 18F dilator, which is also
used to enlarge the femoral vein puncture site. As an alternative
technique, a balloon catheter (8 mm in diameter) can be used for
enlarging the septum and the femoral puncture site. The commissurotome
is then advanced over the wire, and its distal end is placed across the
mitral valve (Figure 1B
). At that time, the guidewire is pulled
back until the bead is firmly held against the tip of the valvulotome
and then securely fastened by screwing the threaded fastener of the
pliers. The dilation can then be performed by squeezing the arms of
activating pliers (Figure 1C
). The desired degree of bar opening
is obtained by use of the caliper. At least 2 openings of the dilating
bars are performed. After dilation, the device is pulled back into the
left atrium, with the guidewire in place in the left ventricle. The
transvalvular gradient is assessed, the left atrial pressure
being measured with the pressure line of the device. Whenever
available, 2-dimensional (2D) echocardiography is
performed to assess the quality of commissural splitting and to obtain
a preliminary assessment of the mitral valve area. If necessary, an
additional opening at a larger size can be made. After valvotomy, a
left ventricular angiogram is performed to assess the
degree of any subsequent mitral regurgitation.
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Data Collection and Analysis
Before the procedure, M-mode and 2D
echocardiography were performed to confirm the
severity of mitral stenosis and the valve morphology. The
Wilkins echocardiographic scoring system in 16
grades5 was used to assess the severity of mitral valve
thickness, leaflet mobility, valvular calcification, and
subvalvular disease, each being graded from 1 to 4. The mitral
valve area was determined by 2D echocardiography
with planimetry in the short-axis view and by continuous-wave
Doppler using the pressure half-time method. However, the
planimetry was the reference method used for assessment of the
results.6 The cardiac output could not be measured in the
majority of centers, and thus, the valve area was not assessed by
Gorlin's formula.
Immediately before and after PMMC, the left and right heart pressures and the mean transmitral pressure gradient were measured, and a left ventricular angiogram in the 30° right anterior oblique view was performed using the same amount and delivery rate of contrast to assess the left ventricular function and the presence and severity of any mitral regurgitation. A coronary arteriography was performed before PMMC in all patients with documented ischemia, and also in men >40 and women >50 years of age. Transatrial shunting was assessed after the procedure with transthoracic color flow Doppler and transesophageal color flow Doppler in a subset of 28 patients. The final echocardiographic results were recorded at day 1 after valvotomy. The procedural success was defined as a mitral valve area >1.5 cm2 on the echocardiographic imaging performed 1 day after PMMC, in absence of Sellers grade >2 mitral regurgitation.
Statistical Analysis
Continuous variables are expressed as mean±SD. Variation in
continuous variables from baseline to day 1 after completion of
PMMC was assessed with the paired Student's t test or, when
the sample size was small, with the Wilcoxon signed rank test.
The following baseline variables were assessed as to their
predictive role on post-PMMC mitral valve area and absolute variation
in mitral valve area (difference between area after and before PMMC):
the patient's age, NYHA functional class, left and right
hemodynamic variables, quantitative
echocardiographic variables,
echocardiographic score, mitral valve area, mean
transmitral gradient, degree of associated mitral
regurgitation, and history of previous mitral
commissurotomy. In addition, the extent of bar opening during
commissurotomy was assessed. In univariate
analyses, the following 2-sided statistical tests were used:
for continuous variables, the Pearson correlation coefficient was
estimated and tested to 0; for binary variables, the Mann-Whitney
nonparametric test was used; for categorical variables
with >2 levels, the Kruskal-Wallis nonparametric test was
used. The variables that appeared to be significantly associated
with the outcome (mitral valve area after PMMC and variation in mitral
valve area) at the 0.10 significance level were further assessed by
stepwise multiple linear regression with a threshold corresponding to a
0.05 significance level.
| Results |
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The maximal extent of bar opening was 40 mm in 114 patients (77%), 37 mm in 24 (16%), and 35 mm in 10 (7%). The mean number of openings was 3.4±1.6.
A successful result was obtained in 141 of the 153 patients enrolled
(92%) and in 141 out of the 148 patients (95%) in whom PMMC was
actually performed. The technique resulted in a significantly increased
valve area, as shown in Table 2
. At day
1, the mitral valve area had increased from 0.95±0.2 to 2.16±0.4
cm2 (P<0.001). Bilateral splitting of
the commissures was noted in 129 patients (87%). According to the
echocardiographic score, the mean post-PMMC mitral
valve areas were 2.21±0.3 and 2.11±0.35 cm2 in
patients with scores <8 (87 patients) and
8 (61 patients),
respectively, a nonsignificant difference. As shown in Figure 2
, the increases in valve areas were
comparable up to a score of 12.
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The mean duration of the procedure from the time the septal puncture was completed to the withdrawal of the catheters (which was recorded in the last 108 patients) was 31±14 minutes.
Complications
In addition to the above-mentioned case of hemopericardium
with tamponade (which resulted from the transseptal
catheterization), severe complications occurred in 3
patients in whom PMMC was actually performed. One patient developed a
massive (grade 4) mitral regurgitation and required
urgent mitral valve replacement, with uneventful outcome. The
regurgitation was related to a transverse tear of the
anterior valve leaflet. Another patient developed a severe (grade 3)
mitral regurgitation, with uneventful clinical course.
On echocardiographic follow-up at 2 months, the mitral
regurgitation was moderate and the patient was
asymptomatic. Another patient developed a transient episode
of aphasia with mild facial hemiparesis, with complete recovery within
hours after the procedure.
On transthoracic color flow Doppler, transseptal shunting was not detected or was trivial after the procedure. In the subgroup of 28 patients who also had transesophageal color flow Doppler, transseptal shunting was detected in 24 patients, trivial in 22 and small in 2.
Changes in mitral regurgitation are shown in Figure 3
. In addition to the 2 patients
mentioned above who developed a severe mitral
regurgitation (grades 3 and 4), mitral
regurgitation was increased by 2 grades in 2 patients
only and by 1 grade in 14; it decreased by 1 grade in 15 patients and
was unchanged in the remaining 115. In 3 patients treated during the
first half of this study and in whom a mitral
regurgitation with no hemodynamic
consequences (grade 1 in 1 patient and grade 2 in 2 patients) was
observed after PMMC, a small piece of tissue was found hooked to the
tip of the dilator after PMMC. In 1 case, the tissue corresponded to a
chorda. In the other 2 cases, histological examination
showed evidence of valvulitis, confirming the valvular
apparatus as the source of tissue. These events led us to
improve the device by developing a safety lock, which is described
above. Since then, no extraction of tissue has been observed.
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There were no other complications. The in-hospital follow-up was uneventful in all cases, and the patients were discharged an average of 2 days after the procedure.
Predictive Role of Baseline Variables on Changes in Mitral
Valve Area
From univariate analyses, post-PMMC valve area
was positively correlated with baseline mitral valve area
(P=0.002) and extent of bar opening (P=0.007) and
negatively with echocardiographic score
(P=0.0003). The absolute variation in mitral valve area was
positively correlated with systolic pulmonary pressure
(P=0.026) and mean transvalvular gradient
(P=0.032), negatively correlated with patient age
(P=0.02) and baseline valve area (P=0.0001), and
there was a nonsignificant trend for a negative correlation with extent
of bar opening (P=0.087). From stepwise multiple linear
regression, we found that baseline mitral valve area
(P=0.026) and extent of bar opening (P=0.046)
were the only 2 variables significantly and independently
associated with post-PMMC valve area or with absolute variation in
valve area (P<0.0001 and P=0.048,
respectively).
| Discussion |
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Comparison With the Results of Balloon Techniques
These results are encouraging and at least comparable to those
reported with the use of balloon catheters. At day 1 after PMMC, the
mean valve area was 2.16±0.4 cm2 for the entire
series, a 127% increase from baseline. Several reports have confirmed
that the final valve area was a significant predictor of favorable
long-term outcome.7 8 9 10 11 The abundant literature concerning
the immediate results of BMV12 13 14 15 16 17 shows that the
postvalvotomy valve areas obtained are slightly less with the Inoue
technique (
2 cm2 in the majority of reports)
than with the double-balloon technique. In a meta-analysis of
the international experience in which the 2 techniques were
compared,15 the mitral valve area reached an average of
1.84 cm2 with the Inoue technique and 1.93
cm2 with the double-balloon technique. As shown
in Figure 2
, the valve area remained roughly constant up to a
score of 12, but the limited number of patients with a score >10
(n=11) has to be taken into account in this statement. The score was
not independently associated with post-PMMC valve area and absolute
increase in valve area. This observation is in agreement with a
previous report18 but in opposition to other studies in
which valve morphology appeared to be an important predictor of
immediate outcome.17 19 20
The very limited incidence of complications in this first series of patients is noteworthy. Only 1 patient had a stroke with minimal and transient clinical consequences. The incidence of embolic events after BMV is reported to be in the range of 1% to 4% despite the use of routine preoperative transesophageal echocardiography.21 In 1 case, a pericardial tamponade occurred after the transseptal puncture. Cardiac perforation with subsequent tamponade is a well-known life-threatening complication of BMV, with an incidence of 1% to 9% in the literature.16 22 23 24 It can result from inadvertent atrial perforation during the transseptal catheterization or from perforation of the left ventricle by guidewires in the double-balloon technique. Despite the necessity of placing a guidewire in the left ventricle with this new technique, the risk of ventricular perforation seems to be decreased by the high flexibility of the distal 10 cm of the wire, the stability of the dilator head during opening (due to the uninterrupted blood flow through the valve orifice), and the traction with subsequent backward movement of the wire associated with the opening process. However, the lower puncture site required for this technique might increase the potential risk of cardiac perforation in less experienced hands.
Of the 148 patients, only 2 (1.4%) developed severe mitral regurgitation after PMMC, and urgent surgery was necessary in 1. In these 2 cases, the complication was unpredictable. Strikingly, no increase or even a decrease in mitral regurgitation was noted in 119 patients (80%), a rather unusual feature after BMV. The incidence of severe mitral regurgitation after BMV in the literature varies between 1.4% and 7.5%16 22 25 26 27 28 29 30 and does not appear to be different with the single- or double-balloon technique.31
Finally, no significant transseptal shunting could be detected after PMMC by transthoracic or transesophageal color flow Doppler. However, oximetry was not used in the study because it was not usually performed in the majority of centers. With BMV, the incidence of residual transatrial shunting varies between 2.5% and 87%, depending on the modality of assessment.22 24 25 32 However, regardless of the technique used, most of the transatrial shunts closed spontaneously during follow-up.32 33
Ben Farhat et al34 reported recently in a randomized study that the results of closed surgical commissurotomy were less good than those of BMV and open commissurotomy, with a mean increase in valve area to only 1.6 cm2 versus 2.2 and 2.2 cm2, respectively. These results are in agreement with previous reports35 36 but disagree with other studies showing comparable results after BMV and closed surgical commissurotomy.2 3 Despite the resemblance of the instrument used in closed surgical commissurotomy and in PMMC, the 2 techniques differ by many aspects, such as the self-positioning of the dilator's bars in the commissures. Furthermore, with PMMC, the immediate evaluation of the hemodynamic and echocardiographic results after dilation offers the possibility of subsequent additional dilator opening to a larger size when needed.
Technical Considerations
The training requirement for such a procedure is in the range 8 to
10 cases for any investigator with a good experience of BMV, and less
for those with previous experience with the double-balloon
technique.
Crossing the Septum and the Mitral Orifice
Despite the length, caliber, and inescapable rigidity of the
metallic dilator, the device could easily reach the mitral valve in the
vast majority of cases. However, in 3 patients with a very thick
septum, additional dilatation of the septal puncture site with an 8-mm
balloon was necessary. During the opening phase, the dilator was
perfectly stable, and the hemodynamic tolerance was
good because of the noninterrupted blood flow.
Positioning the Device Across the Mitral Valve
An optimal positioning of the dilator across the valve before
opening can be achieved by several means: (1) a satisfactory position
is generally obtained when the distal half of the dilator is located
slightly ahead of the aortic orifice, which is indicated by the
presence of a pigtail catheter placed against the aortic leaflets; (2)
when available, the left atrial angiogram obtained after transseptal
catheterization is helpful to locate the free edges of
the valve; (3) the transition between the left ventricular
and left atrial pressure curves gives an excellent indication of the
location of the border of the mitral valve; this can be observed during
the withdrawal of the Mullins sheath after the guidewire has been
positioned in the left ventricle or by recording these
pressures by use of the pressure lumen of the dilator; (4)
on-line transthoracic 2D
echocardiography is frequently used and is an
excellent way of optimizing the position of the device; and (5) the
resistance to the device opening is well perceived while the arms of
activating pliers are squeezed, and this confirms the accurate
positioning of the dilator.
Extent of Bar Opening
The extent of bar opening appeared to be a significant predictive
factor of the immediate PMMC results. The device sizing was not made
according to the measurement of the mitral annulus. In adult patients
with a body surface area >1.50 m2 and without
severe valvular calcifications, we usually open the device to
40 mm at first. In other patients, we start with 37 mm (or
35 mm in children), with a stepwise increase in opening according
to the results.
Mechanism of Action
Before this clinical study was begun, the ability of this device
to enlarge a stenosed mitral orifice was evaluated on 3 postmortem
specimens with severely fibrotic and calcified fused leaflets. The
device opened up to 40 mm was able to markedly enlarge the valve
orifice, primarily by separating the fused commissures without any
injury to the leaflets or the chordae. In clinical practice, this
device was shown to act mainly by direct stretching and subsequent
separation of the commissures as assessed by 2D
echocardiography, which could be performed on-line
during PMMC in
50% of cases.
Economic Aspects
An important potential advantage of the metallic dilator is
the expected decrease in procedural cost. Although the price of the
device (when made on a large-production basis) remains
undetermined at the present time, we believe that it should be
comparable to that of an Inoue balloon catheter. However, the
detachable metallic head allows multiple safe reuse after sterilization
by autoclave, as for any other metallic surgical tool. We have already
performed 35 consecutive procedures with a single device without any
deterioration of the dilator components. Thus, it is expected that the
final cost per patient will be markedly lower than that of the balloon
catheters in current use. This should be considered a major advantage,
particularly in countries with limited financial resources.
Future of the Procedure
This first clinical experience with the new technique is
promising. A multicenter prospective international registry is
currently ongoing that will definitely determine the benefits,
limitations, and cost-effectiveness of the procedure. A French
prospective study also started in January 1998 with the goal of
assessing the immediate as well as the long-term results of the
technique. Finally, a randomized study comparing this technique with
the current balloon techniques is scheduled to start in the course of
this year.
| Acknowledgments |
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| Footnotes |
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| Appendix 1 |
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India: Apollo Hospital, Hyderabad: P.C. Rath, MD. GB Pant Hospital, New Delhi: R. Arora, MD; G.S. Kalra, MD. Civil Hospital, Ahmedabad: S. Dani, MD. Jayadeva Institute of Cardiology, Bangalore: C.N. Manjunath, MD. Manipal Heart Foundation, Bangalore: S. Chandra, MD. Sri Ramachandra Hospital, Chennai: J.S.N. Murthy, MD. Railway Hospital, Chennai: S. Rajagopal, MD; K. Abraham, MD. Ruby Hall Hospital, Pune: Dr P.C. Grant. Military Hospital Cardiothoracic Center, Pune: M.S. Kumar, MD; S. Kashyap, MD.
Egypt: National Heart Institute, Cairo: A. Imam, MD; S. El-Togbi, MD. Al-Azhar University, Cairo: M. El-Sayed, MD.
Received May 15, 1998; revision received October 16, 1998; accepted October 26, 1998.
| References |
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