Percutaneous Transvenous Mitral Commissurotomy Using Metallic Commissurotome: Long-Term Follow-Up Results

Percutaneous transmitral commissurotomy (PTMC) has been established as an effective treatment for mitral stenosis (MS) and is now the procedure of choice.^1–6 Of the procedures available to treat mitral stenosis, percutaneous valvotomy using the Inoue balloon is well established and carried out worldwide. The miniaturized metallic commissurotome devised by Cribier et al. is reported to be a reliable and effective alternative to balloon mitral commissurotomy.^7–11 The ease of resterilization and unchanged physical properties after multiple uses have made this device a promising alternative to balloon valvotomy, especially in developing countries that are forced, despite the inherent dangers, to reuse balloon catheters. There are several reports of PTMC procedures using metallic commissurotomy describing the acute and short-term results.^7–18 However, reports of long-term efficacy of this technique are very few with small numbers of patients.¹⁹ Here we report the long-term follow-up results of mitral valvotomy using the metallic commissurotome. Materials and Methods Study population. A total of 248 (65 males) patients, with severe mitral stenosis who underwent PTMC using the metallic commissurotome at our institution formed the study population. Methods. Prior to the procedure, all patients underwent a detailed clinical and echocardiographic evaluation (2-D echocardiography, Doppler and color flow imaging) to assess the severity of mitral stenosis, valve morphology and mitral regurgitation (MR). The Wilkins echocardiographic scoring system20 in 16 grades 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 2-D echocardiography with planimetry in the parasternal short-axis view, and by continuous wave Doppler using the “pressure half-time” method. Multiplane transesophageal echocardiography (TEE) was used in all adults to rule out left atrial (LA) clot and to assess MR. Patients 21 The procedure was performed under local anesthesia, with the entry site being the right femoral vein in all patients. All procedures were performed with standby closed and open heart surgery capabilities. All patients were administered prophylactic antibiotics. Septal puncture was done via the Brockenbrough technique, and all patients were heparinized after septal dilatation. A lower septal puncture was preferred for this PMMC procedure. Left ventricular (LV) angiography in the 30° right anterior oblique view was performed prior to the procedure in all patients suspected of having more than mild MR. Mitral regurgitation was graded 1 through 4, as already described.22 Patients who had more than mild MR were excluded. Immediately before and after PTMC, the left and right heart pressures and the mean transmitral pressure gradients (TMG) were measured. The result of the procedure and the amount of MR were assessed by echocardiography in the catheterization laboratory itself. Procedural success was defined as an increase in mitral valve area of at least 50% from the basal, or a final valve area of > 1.5 cm² in the absence of moderate-to-severe mitral regurgitation. Transatrial shunting was assessed after the procedure with oximetry run, and on follow-up with color flow imaging. Mitral restenosis was defined as a loss of > 50% initial gain in valve area with reappearance of symptoms.⁵PTMC using metallic commissurotome (PMMC). Percutaneous metallic mitral commissurotomy was performed as previously reported.^7,9,11 The metallic commissurotome (Medicorp, Inc., France) consists of a distal metallic head (5 cm long x 5 mm in diameter) comprised of two 15 mm long hemicylindrical bars. It is fixed at the tip of a 12 Fr disposable catheter and connected by an internal cable to a proximal hand-operated device that can open the arms gradually to a maximum of 40 mm. The metallic head is detachable and can be resterilized and reused multiple times. After septal puncture, a Mullins sheath was introduced into the LV with the help of a 7 Fr balloon floatation catheter (Arrow International, Inc., Reading, Pennsylvania) across the mitral valve. A beaded stainless steel wire, 270 cm in length and 0.035 inch in size (with a metallic bead 2 mm in diameter soldered at the junction of the stiff core and the 10 cm distal floppy end), was positioned in the LV through the Mullins sheath. The commissurotome is tracked over the bead wire across the atrial septum and the mitral valve. The extent of the initial bar opening was selected based on the patient’s body surface area. Patients had the initial bar opening set at 33, 35 or 37 mm depending on their body surface area and, if necessary, the bar was increased gradually to a maximum of 40 mm. Follow-up evaluation. Follow-up evaluations were completed at 1 month, 6 months and then yearly. The follow-up evaluation at 1 month included clinical examination only. At 6 months and at yearly follow-up visits, patients underwent a detailed clinical and echocardiographic evaluation. Patients who never came for regular follow-up and those who did not participate in the follow-up in the preceding 1 year after the procedure were contacted by letter and asked to report for review. Those who could not come for follow-up were asked to consult the local cardiologist and forward our institution the echocardiographic and clinical report so that the data could be used for analysis. Statistical analysis. Continuous variables are expressed as mean ± SD and compared using the independent sample t-test, with 95% confidence interval. Categorical variables are compared with the Fisher’s exact test. A p-value Follow-up evaluation. The mean follow-up period was 3.34 ± 0.66 years (40 ± 8 months). Six patients were lost to follow-up. Seven patients had a follow up of only 6 months. All other patients participated in follow up of more than 1 year. The time period of follow-up and the number of patients evaluated are as follows: 6 months (n = 7), 1 year (n = 12), 2 years (n = 27), 3 years (n = 47), 4 years (n = 102), 5 years (n = 14), 6 years (n = 11). Of the 224 patients who underwent a successful procedure and were still under follow up, 7 developed mitral restenosis. The mean pressure gradient across the mitral valve assessed by echocardiography was 6.1 ± 3.2 mmHg (p 2 (p p > 0.05). Discussion Rheumatic mitral valve disease is still a problem in developing countries. Open mitral valvotomy (OMV), BMV and closed mitral valvotomy (CMV) are the procedures available to treat severe symptomatic mitral stenosis. These procedures were compared in randomized trials^23,24 that showed BMV and OMV to be superior to CMV. However, the authors concluded that the favorable results, lower cost, and elimination of drawbacks of thoracotomy and cardiopulmonary bypass indicate that BMV should be the treatment of choice for patients with tight, pliable rheumatic MS.²³ Recently, Cribier et al. developed a percutaneous valvulotomy device featuring a metallic valvulotome which functions similar to the metallic device (Tubbs dilator) used by surgeons for closed chest mitral commissurotomy.⁹ This device works mainly by stretching and subsequent separation of the commissures. Once the device is opened across the mitral valve, the catheter shaft rotates by itself in such a way that the bars are directed to the commissures, leading to improved tolerance and efficacy.⁹ The main advantage of this device is that it can be reused several times without any loss of performance after proper resterilization, thus decreasing procedural costs^9,11 — a particularly important issue in developing countries where resources are scarce. Our center has been using the Inoue balloon technique for mitral valvotomy since 1994, and we have performed more than 1,800 valvotomies using the device thus far. We began using the metallic commissurotome in 1998. The success rate of PMMC valvotomy in this series was 92.7%. Cribier et al. reported a success rate of 92% by PMMC in a series of 153 patients.⁹ The same group has reported a success rate of 93% in a larger series of 500 patients.⁸ Bhat et al.¹¹ published a randomized study comparing PMMC and IBMC, and found similar success rates (90.18% versus 91.8%; p = NS). Guerios et al.¹⁹ also published a randomized study of 50 patients and found that the success rates were similar (100% versus 91.3%).¹⁹ The success rate of the double balloon technique and Inoue balloon technique, as reported by Arora et al.⁶ in a series of 600 patients, was approximately 93.6%, which is similar to the reported success of the PMMC technique. PMMC led to a significant increase in mitral valve area from 0.85 ± 0.14 cm² to 1.95 ± 0.33 cm², an increase of 130% over the baseline. Bhat et al.,¹¹ in a randomized comparison, found that the acute result with PMMC was similar or marginally better than IBMC (postprocedure valve area of 1.69 cm² with IBMC compared to 1.86 cm2 with PMMC). Similarly, Guerios et al.19 found the acute results of PMMC to be better (2.17 ± 0.13 versus 2.00 ± 0.36 cm²; p = 0.04). In a nonrandomized comparison of PMMC (n = 127) versus IBMC (n = 350), Mittal et al.12 found that the PMMC group had a higher gain in valve area than the IBMC group (126% versus 111.4%; p = 0.05 ). Also, in another nonrandomized study by Bahl et al.¹⁴ (28 PMMC and 128 IBMC cases), an increase in valve area of 0.8 to 2.3 cm² was observed in the former, compared with 0.7 to 1.9 cm² in the latter group. However, statistical significance in this study was not reported. This report shows that PTMC with a metallic commissurotome is effective in the treatment of rheumatic mitral stenosis, and the acute results are comparable or even marginally better when compared to the standard IBMC technique. The very low incidence of complications is worth noting; the complication rates are similar to IBMC. Mortality was only 0.41% in this series. The mortality rate reported with IBMC is less than 1%.²⁵ Cardiac tamponade occurred in 2 patients (0.8%) (both due to a LV tear). IBMC is reported to have a 0.2–4.1% incidence of cardiac tamponade.²⁶ Thromboembolic episodes and stroke are reported to occur in 0–3.1% of patients undergoing IBMC.25 In our group of patients, 1 experienced a TIA (incidence of 0.4%). Mitral regurgitation following PTMC is a dreaded complication. It is said to decrease with the “step-wise inflation technique” as opposed to the “single inflation technique”. In our patients, we employed the “step-wise inflation technique”. We had an incidence of 1.6% of severe mitral regurgitation and a 3.6% incidence of moderate-to-severe MR. The incidence of severe MR following IBMC is reported to vary from 1–5.2%.²⁴ The incidence of MR in this series is very comparable to the data on IBMC. It is argued that since the size of the septal dilator used in PMMC is 18 Fr instead of the 14 Fr size used in IBMC, PMMC will lead to a larger septal defect and thus more chance of persistent left-to-right shunts. But in our group, only 3% of the patients had a persistent left-to-right shunt immediately after the procedure, and only 2 had a persistent minor shunt at follow-up. The incidence of right-to-left shunting reported with the Inoue balloon technique varies from 5–20% in one report³ and 3–16% in another.²⁵ Reports on follow-up data on this technique are few.^11,19 On follow-up of 3.34 ± 0.66 years in this series, mitral valve area decreased to 1.67 ± 0.37 cm², a decrease of 16% from the immediate postprocedure value. Bhat et al.¹¹ and Guerios et al.¹⁹ have reported late loss of valve area with PMMC compared to IBMC. It is argued that the reason for this phenomenon of “late loss” of valve area could be due to stretching of the valve by the metallic commissurotome.^11,19 Only 7 patients (3.2%) developed mitral restenosis in our group. Two series^6,26 report that patients who underwent IBMC were followed up for a period similar to that of our study. Mitral restenosis developed in 1.7% of patients in the series reported by Arora et al.⁶ at a mean follow-up of 37 ± 8 months. However, Hernandez, et al.²⁶ reported that the incidence of restenosis was 10% in a series of 561 patients. These patients were followed up for a mean period of 39 ± 23 months. In that series, the patients were older on average than were our patients (53 ± 13 years versus 32.3 ± 7.9 years), which may explain the higher restenosis rate. Three of the 23 patients who underwent PMMC developed restenosis in the series reported by Guerios et al., but the restenosis rate was comparable to IBMC (2 of 27 patients).¹⁹ On multivariate analysis of a study involving more than 1,000 patients who were followed up after PTMC, the predictors of poor functional results were old age, unfavorable valve anatomy, high NYHA class, atrial fibrillation, low valve area after PTMC, a high gradient after PTMC and grade 2 mitral regurgitation after PTMC.²⁷ Calcific mitral stenosis was found to have a higher rate of restenosis.²⁸ Though there was a significant decrease in valve area on follow-up, there was no significant symptomatic deterioration in the majority of patients in the study group. Wang et al.²⁹ followed up patients who underwent successful BMV for more than 3 years and found that they had a loss of valve area of 0.06–0.08 cm² per year. They noted the absence of symptomatic deterioration, even though there was loss in valve area. Palacios, et al.,³⁰ who reported long-term follow-up results following Inoue balloon mitral valvotomy, found that though adverse events (death, mitral valve surgery, and redo PTMC) were low within the first 5 years of follow up, a progressive number of events occurred beyond this period. Thus, our patients need close follow up to monitor the likely development of adverse events on further follow up. Conclusions PMMC is successful in providing relief from severe mitral stenosis for gain in valve area and reduction in TMG. This technique has similar procedural success and complication rates when compared to the standard technique of IBMC. Long-term follow-up data at 40 months show that the restenosis rate is only 3.2%, and symptomatic improvement is maintained in the vast majority of patients.

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