Mitral Stenosis and Percutaneous Mitral Valvuloplasty (Part 2)

Several studies have determined the safety and efficacy of percutaneous mitral valvuloplasty (PMV) during pregnancy, the larger series being those recently described by Esteves,¹²² Nercolini et al.,¹¹⁸ and Ben Farhat et al.¹²⁰ Retrospectively comparing PMV and open mitral commissurotomy (OMC) in pregnant women with mitral stenosis (MS), Souza et al. demonstrated similar rates of maternal clinical improvement, but significantly lower rates of fetal complications in the PMV group.¹²¹ Data concerning the late follow-up of patients submitted to PMV while pregnant showed that the immediate benefits of the procedure were maintained for the mother, and the babies developed normally, without any intervention-related clinical abnormality.^120,122,123 Potential adverse effects of irradiation on the fetus may be attenuated by wrapping the mother’s abdomen with a lead barrier during valvuloplasty, and by carrying out the procedure at the adequate gestational age. The best period is the fourth month of pregnancy, when organogenesis is already complete, the fetus’s thyroid is still not active (avoiding the risk of hypothyroidism due to the iodine contrast medium), and the uterus, still small, is more distant from the mother’s chest than in the following months.¹¹⁹9.2. Patients in atrial fibrillation. Atrial fibrillation (AF) is the most common complication — perhaps a sequel — of MS, occurring at a rate of approximately 40%.⁹ In Olesen’s¹²⁴ study on the natural history of MS, survival of patients with MS and sinus rhythm or AF after 11 years was 46% and 25%, respectively, and after 18 years, 29% and 0%. In patients with MS, AF is the major risk factor for systemic embolism. Data from the pre-anticoagulant era show embolism figures of up to 31.5% for patients with MS and AF, compared to 8% rates for those in sinus rhythm.¹²⁵ Leon et al. compared the outcomes of 355 patients in AF and 379 patients in sinus rhythm submitted to PMV. For the patients in AF, the intervention resulted in smaller final MVAs, and event-free survival after 60 months was only 32%, compared to 60% in patients in sinus rhythm. However, AF per se was not identified as an independent predictor of immediate success or late outcome, but only a marker of clinical and morphological characteristics associated with worse results after PMV, such as older age, more frequent previous commissurotomy, and higher echo scores.¹²⁶ AF, therefore, should not be taken as a stronger determinant for choosing how to treat patients with MS. 9.3. Patients with pulmonary hypertension. At the stage PMV is indicated, about half of the MS patients will have discreetly or moderately increased pulmonary pressure, 25% of the patients will have no pulmonary hypertension (PH), and the other 25% will have severe PH, with systolic pressure of the pulmonary artery > 50 mmHg.¹²⁷ PH level is an indicator of global hemodynamic involvement related to right ventricle failure and increased mortality. With severe PH, the mean survival rate of MS patients is 1,8,128 Therefore, the American College of Cardiology and the American Heart Association consensus for managing cardiac valve disease indicates (class IIa) PMV for patients who have MS, favorable valve anatomy and systolic pressure of the pulmonary artery > 50 mmHg at rest or > 60 mmHg with exercise, even if those patients are asymptomatic.⁸ It has been shown that PH does not affect success rates, complications, immediate outcomes, or late evolution of patients treated by PMV,^55,129 meaning that this group of patients particularly benefit from percutaneous dilation as compared to surgery. In addition to the immediate decrease in pulmonary pressure after mitral dilation, in the late follow-up an additional drop in those pressure levels can be observed secondary to the progressive improvement of pulmonary vascular resistance.^129,1319.4. Thrombus in the LA. The relationship between echocardiographic detection of spontaneous contrast in the LA, thrombus in the LA, and systemic embolism is well-established.^132,133 Therefore, a thrombus in an interatrial septum, an obstructive thrombus on the valve, or a floating thrombus in the LA, regardless of its location, are absolute contraindications for transseptal puncture and percutaneous mitral dilation.^3,14 If the patient’s clinical and hemodynamic conditions allow it, oral anticoagulation for variable periods of time (6 months on average) has shown to be an efficient therapy to dissolve thrombi located in the LA, especially if they are small thrombi, and if the spontaneous contrast is not significantly intense.^134,135 After anticoagulation, if a transesophageal echocardiography shows that the thrombus has disappeared, those patients may be safely submitted to PMV.^3,22 Some small series of patients have shown that PMV may be performed by the Inoue technique, which involves less manipulation of the LA, in patients with thrombi in the left atrial appendage, with a low incidence of thromboembolism.^136,137 The small number of patients treated, however, precludes one to assume the potential risk of embolism, especially in elective candidates for mitral valve dilation.¹⁴9.5. Patients with restenosis after surgical commissurotomy or after PMV. The valves of patients who have restenosis after PMV or surgical commissurotomy are more deformed, calcified and fibrotic. In a second surgery, the morbidity and mortality rates are higher than in the original surgery, and most of the patients have a mitral valve replacement instead of a commissurotomy.^8,138–140 Several authors have shown that a PMV may be successfully performed in those patients, except in those whose restenosis is due to rigid leaflets and not to commissural refusion.²² Immediate results are satisfactory, similar, or slightly worse than those in patients who have no restenosis.^141,142 The event-free survival, however, is shorter, especially for elderly patients, patients with comorbidities, higher echo scores, and smaller final mitral valve areas (MVAs) at re-dilation.^68,140,1439.6. Elderly patients. The increased number of elderly patients with symptomatic MS reflects a change in the natural history of the disease. Age is an important factor in determining immediate and late results after PMV, since those patients often have atrial fibrillation and, in general, are in a worse functional class, have more deformed valves and other concomitant diseases.^8,68 The procedure’s morbidity and mortality rates are low, but the immediate success rate is lower than that for younger patients. For this population, independent predictors of success include younger age, lower functional class, lower echocardiographic score, and higher final MVA.^69,144 Late symptomatic deterioration is also more frequent in this group of patients, with an estimated rate of event-free survival at functional class (FC) I or II of only 40 ± 8% after 5 years.¹⁴⁵ Therefore, for elderly patients, PMV should be seen as a useful but palliative procedure. 9.7. Calcified valves. Calcium deposits on the mitral valve are frequent and have a negative impact on PMV and surgery results. During surgery, valves affected by discreet calcification may be treated by commissurotomy alone, while valves that are more severely calcified are replaced by valve prosthesis. For PMV patients, valve calcification degree is an important predictor of immediate and late outcomes. Tuzcu et al. reviewed the relationship between finding calcium at fluoroscopy and late evolution after PMV, and found progressively worse success rates and survival and event-free survival curves as the severity of calcification increases. Among patients with +++ and ++++/IV calcification, only 40% and 20%, respectively, were alive after mitral valve replacement after 2 years, compared with 85% of patients who had no calcification.⁷¹ Iung et al. also studied a similar subgroup of patients, and found an immediate success rate of 76%. Late symptomatic deterioration, however, was very frequent, and only 36 ± 4% of the patients maintained good results after 8 years. For those patients, younger age, lower initial functional class, presence of sinus rhythm, and lower valve calcification degree were predictors of a better evolution in the long term.¹⁴⁶ The analysis of commissure calcification has also shown to be an important predictor of evolution and restenosis after PMV; the procedure may even have a good outcome in patients with high echo scores, as long as they don’t have significant calcification of valve commissures.^33,36 In calcified valves, less aggressive approaches, using smaller balloons and stepwise dilations, seems to be safer. Due to its specific mechanism of action of opening the commissures without exerting pressure on the leaflets, the metallic commissurotome may be a valuable alternative for treating patients with calcified mitral stenosis (MS).⁵⁶9.8. Stenotic biologic prosthesis in mitral position. The mechanism of stenosis on biological prosthesis is predominantly calcification and cusp fibrosis, not fusion of the commissures. During cardiac surgery, Lin et al. dilated the valve prosthesis in 5 patients whose valves were replaced a second time due to stenosis, and observed thereafter a lack of cusp coaptation, as well as tears on the free edges of the leaflets or along their insertion in the prosthesis ring, causing severe mitral regurgitation (MR).¹⁴⁷ In the literature, however, there are sporadic descriptions of successful PMV in such situations.^148–150 Nevertheless, the potential risk associated with this strategy indicates that it should be restricted to highly symptomatic patients with no conditions for valve replacement.¹⁴9.9. Patients with unfavorable characteristics for PMV. Several authors reported having performed emergency PMV, usually due to refractory cardiac failure, with a high success rate, low mortality, and good late evolution of the patients. Salvage PMV is thus feasible, with immediate and dramatic improvement after valve dilation. In those critical patients, event modest improvement in MVA results in significant clinical improvement.^151,152 Several authors specifically studied PMV in patients with unfavorable characteristics (older age, worse functional class, calcified valves, higher echo scores, or associated diseases^{4,34,69,71,153,154}), and have shown early success rates of approximately 60%, and event-free survival much lower than that of patients in more favorable conditions. The consensus seems to indicate surgery for patients with significant and/or bicommissural valve calcification, and PMV for patients at high surgical risk and pregnant women.¹⁵⁵ In the remaining cases, some authors favor surgery due to worse PMV results;³⁴ while others, considering the disadvantages of mitral valve replacement, prefer the percutaneous procedure as an initial approach in selected patients, restricting surgery for failed cases.⁷¹10. Comparative studies 10.1. PMV and surgery. Among the surgical approaches to treat MS, CMC is the most similar to PMV. However, although both are blind procedures, it has been shown that the MVA increase after closed mitral commissurotomy (CMC) is not uniform.¹⁵⁶ PMV can be better controlled by more adequate positioning of the balloon and because it can be repeated immediately in case of an unsatisfactory outcome.^74,157 OMC, in turn, by enabling direct view of the procedure and by acting on the subvalvular apparatus, would theoretically have better outcomes than PMV. Randomized studies comparing PMV with CMC and OMC were as follows. Patel et al.,¹⁵⁷ Turi et al.,¹⁵⁸ and Arora et al.¹⁵⁹ randomized MS patients for PMV or CMC. Patel et al. achieved higher immediate MVAs by performing PMV. Arora et al. showed similar outcomes in the immediate post-operative period and at 22 months, with restenosis rates of 5% and 4%, respectively. Patients randomized by Turi et al. were followed for 10 years after treatment. The authors showed similar immediate outcomes and late restenosis rates of 30% for the PMV group and 47% for the CMC group.^158,160 Bueno et al.¹⁶¹ and Cardoso et al.¹⁶² carried out randomized studies comparing PMV and OMC, and achieved similar outcomes with both techniques not only in the immediate post-operative period, but also after 22 months for the first study, and after 12 months for the second. Reyes et al., with similar randomization, also found identical initial MVA increases in both groups. After 3 years, however, the PMV group still had higher MVAs than the OMC group of patients (2.4 ± 0.6 cm2 and 1.8 ± 0.4 cm2, respectively).¹⁶³ Ben Farhat et al. randomized 90 patients to PMV, OMC or CMC. After 7 years, the MVA of the groups who had had PMV and OMC were similar (1.8 ± 0.4 cm2), but the mean MVA found in the CMC group was 1.3 ± 0.3 cm2, with a restenosis rate of 37% (compared to 6.6% in the first 2 groups), and a reintervention-free survival rate of only 50%, compared to 90% in the PMV group, and 93% in the OMC group.¹⁶⁴ Therefore, MS therapy changed after the introduction of PMV. Compared to surgery, and because of the similar effectiveness of both treatment forms, the advantages of PMV in terms of comfort, complications, cost, hospital stay, and recovery period, made this the procedure of choice for managing patients with severe symptomatic MS and favorable anatomy.^33,158,165 However, Palacios et al. emphasized that only 36% of PMVs carried out in patients with more deformed valves (echoscore ? 12) have a good immediate outcome, and only 10% of them remain event-free after 4 years.¹⁰⁴ Such patients must, therefore, be referred to surgery, showing that PMV and mitral valve surgery are not competitive — but rather complementary — techniques, each of them indicated in a particular stage of the disease.²²10.2. Different PMV techniques. Several studies — both randomized and nonrandomized — compared PMV using the Inoue Balloon (IB) and the double-balloon (DB) techniques.^166–170 The combined analysis of such data permits one to conclude that the DB provides a higher final MVA and higher absolute increase of the MVA than the IB, but it is a more difficult technique, with a higher complication rate.¹⁷¹ The late evolution of patients treated by both techniques is, however, similar, not only regarding exercise capacity and MVA, but also the incidence of restenosis and need for repeat intervention.^{70,93,168,170} Bahl et al., in a nonrandomized study, compared 1,000 PMVs performed with the Inoue technique, with 100 procedures performed by the retrograde approach, and showed similar outcome in terms of success, final MVA, and severe MR. Regarding complications, cardiac tamponade (2%) and ASD (2.5%) occurred exclusively with the Inoue technique, since the retrograde technique does not require transseptal puncture; however, more peripheral vascular complications (3% versus 0.5%) were recorded with the retrograde technique.¹⁷² Because it is a more recent technique, very few studies compare the metallic commissurotome (MC) with other PMV techniques. Zaki et al. randomized 80 patients to treatment either with IB or MC, and found no differences concerning final MVA, although with the MC, there has been a higher rate of bicommissural splitting and better outcomes in patients with higher echo scores.¹⁷³ In the VID (Valvulotome Inoue Double balloon) study, El Sayed et al. randomized 150 patients to a PMV with MC, IB or DB, including 50 patients in each group. The MVAs achieved were, respectively, 2.1 ± 0.5 cm2, 2.0 ± 0.2 cm2 and 1.9 ± 0.4 cm2, with a bicommissural opening rate of 60%, 20% and 52% (both p = 0.01).174 Regarding the late outcome of the patients treated, our group recently published a randomized study comparing the results of 27 patients who underwent PMV with the IB technique, and 23 in whom the intervention was performed with the MC. The patients randomized to the MC had greater immediate MVAs than those of the IB group (2.17 ± 0.13 versus 2.00 ± 0.36 cm2, p = 0.04), but this difference was no longer significant after 6 months (2.06 ± 0.27 versus 1.98 ± 0.38 cm2, p = 0.22), and after 3 years of follow-up (1.86 ± 0.32 versus 1.87 ± 0.34 cm2, p = 0.89). These results suggest that valve stretching is an important mechanism of valve dilation with the MC. The restenosis rates with both techniques were similarly low after 3 years (3 patients in the MC group versus 2 patients in the IB group; p = 0.65).¹⁷⁵ In all 3 studies, due to the possibility of re-sterilizing the device while maintaining its performance, the cost of the procedure using the MC was significantly lower than with other techniques.