Abstract
A major advance in the treatment of valvular heart diseases has been emergence of non-operative percutaneous valve interventions. Balloon dilatation referred to as balloon valvotomy or valvuloplasty has become a preferred treatment for patients having mitral, pulmonary or tricuspid stenosis with excellent early and long term results. For aortic stenosis, balloon valvotomy provides an excellent palliation and either avoids or delays valve replacement.
A new era has begun in treatment of valvular heart disease with the introduction of percutaneous devices. Transcatheter implantation of pulmonary valve has already been successful in large number of patients with pulmonary regurgitation. The feasibility of percutaneous aortic valve replacement in surgically inoperable patients with aortic stenosis is a great advance. A large number of trials are on with use of mitral valve devices for percutaneous mitral valve repair in patients with mitral incompetence. The future of percutaneous valvular interventions is going to be exciting.

Valvular heart disease (VHD) continues to be a common clinical problem in developed and developing countries. The aetiology of VHD differs between developed and developing world. Rheumatic valvular heart disease (RHD) continues to be a significant cause of morbidity and mortality in developing countries, whereas degenerative, congenital and other forms of VHD are seen all over the world. Open or closed heart surgery involving dilatation, repair or replacement of the valves is an established procedure for treatment of VHD over the last 4 to 5 decades.

Percutaneous treatment of valvular disorders started in 1980’s and the first procedure involved dilatation of a stenotic valve (referred to as balloon valvuloplasty, balloon valvotomy or balloon commissurotomy). These techniques quickly became popular as they proved safe, avoided surgery (thoracotomy), major anaesthesia, blood transfusion, and were associated with early discharge from the hospital. The percutaneous procedures evolved rapidly with expansion of their indications. For the purpose of this article, the percutaneous valvular interventions will be considered under two headings :

1) Balloon dilatation of stenotic valves (Balloon valvotomy, valvuloplasty).
2) Percutaneous valve repair, valve replacement.

1. Balloon Dilatation of Stenotic Valves
   These interventions are very commonly performed in India.6-9 Balloon valvotomy (BV) is utilized for relief of valvular stenosis resulting from rheumatic, congenital or other aetiologies. Stenosis of mitral valve is the commonest valvular stenosis seen in our country and is invariably of rheumatic aetiology. Aortic valve stenosis is also common and can occur secondary to congenital, rheumatic or degenerative aetiology. Pulmonary valve stenosis is always congenital in nature and is commonly seen in clinical practice. Tricuspid valve stenosis is uncommon and is always of rheumatic aetiology. Combined stenosis of mitral and tricuspid valves, mitral and aortic valves and also triple valve (mitral, tricuspid, aortic) stenosis is occasionally seen in rheumatic heart disease.

Mitral Valve Stenosis (MVS)
MVS is invariably of rheumatic aetiology. Balloon mitral valvotomy (BMV) as an alternative to surgery was first performed in 1982 by Dr Kanji Inoue1 in Japan. During the last 25 years, several techniques; transvenous antegrade (single or double balloon) or retrograde transarterial have emerged.6-11 In the initial years, the single or double balloon techniques utilizing Mansfield balloon were popular.6,7 Inoue balloon became widely available in early 1990’s and soon became the preferred technique. It continues to be the most widely utilized technique all over the world due to its safety and technical simplicity. Cribier et al12 introduced metallic commissurotomy, which uses a device similar to the Tubbs dilator used during closed surgical commissurotomy. Its efficacy is similar to that of balloon commissurotomy, but the risk of haemopericardium seems higher. In addition, as compared to the Inoue technique, this technique is more demanding for the operator. The potential advantage of metallic commissurotomy is that the dilator is reusable, which reduces the cost of the procedure.

Indications
BMV is indicated in symptomatic patients who present with dyspnoea, heart failure, pulmonary oedema or pulmonary arterial hypertension. Even in asymptomatic patients with valve area 1 cm2 or below, the procedure is indicated to avoid complications. Echocardiographic and Doppler assessment assists in case selection by providing information about valve area, morphology, clot in left atrium (LA), and any mitral regurgitation. Transoesophageal echo-cardiography is indicated in patients with atrial fibrillation, history of stroke or other systemic emboli to detect any thrombus in the LA. The indications of BMV have expanded a great deal. The most ideal indication for BMV is a symptomatic patient with ideal valve morphology (thin, mobile, pliable non-calcified commissures). Several echocardiographic scoring systems are available to categorize the valve morphology. A echo score of < 8 usually predicts an excellent outcome following BMV. The procedure can also be performed successfully in restenosed valves following closed, open surgical commissurotomy13 or restenosis following BMV and an operation can be avoided. BMV is preferred in pregnant patients, in sick patients, shock, those with heart failure and severe pulmonary arterial hypertension. BMV is also indicated in selected patients with clot in LA appendage.¹⁴

BMV is performed in cardiac catheterization laboratory under fluoroscopic guidance and is usually performed under local anaesthesia. The procedure is safe and highly effective technique in palliating symptoms of MVS in children, adolescents, adults and elderly patients. Transseptal catheterisation is performed as the initial step and left atrial entry is secured. Dilatation of mitral valve is performed using an appropriate size balloon.

BMV Using Inoue Balloon Technique. Fig. 1 : Depicts balloon mitral valvotomy using Inoue balloon (A to D). A. Inoue balloon catheter has passed across the mitral valve into the left ventricle (LV). The distal portion of the balloon is inflated. B. The initially inflated balloon is pulled back gently against the mitral valve. C. Further inflation of the balloon results in waist, an hour glass configuration. D. Disappearance of waist indicates commisural separation and excellent result.

The steps of BMV are shown in Fig. 1. Haemodynamics is performed before and after the balloon dilatation. Balloon valvotomy causes commissural splitting and usually increase valve area from basal value of 1 to 2 cm2. BMV provides excellent clinical and haemodynamic benefits which are sustained on short and long term follow-up. Echocardiography is performed a day after the procedure to confirm the results and is also utilized during follow up of the patients. Echocardiography (transthoracic or transoesophageal or intracardiac) can be utilized during balloon dilatation procedure and can be particularly helpful in patients where transseptal puncture is likely to be difficult. The echo guidance can also be useful in pregnant patients where it can minimize the need of fluoroscopy.

Contraindication and Complications
The absolute contraindication for BMV are clot in LA, interatrial septum or associated significant mitral regurgitation. The complications of BMV relate either to transseptal catheterisation or to valvotomy technique. In the current era of expertise, the incidence of complications like cardiac tamponade, mitral regurgitation requiring valve replacement and embolism is very low.

BMV is technique of choice for majority of patients with mitral stenosis as it compares favourably with open or closed surgical valvotomy in short and long term (almost 20 years) results. If BMV is initially successful, the survival rates are good, the need of subsequent surgery is infrequent, and functional improvement occurs in the majority of the cases. The incidence of restenosis, as assessed by sequential echocardiography has been reported to be 5 – 20% after a follow-up of 1 to 5 years.

Aortic Valve Stenosis (AVS)
Aetiology of AVS can be congenital, rheumatic or degenerative calcific. Indication for intervention (surgery or balloon dilatation) in AVS is symptoms like angina, syncope, dyspnoea or heart failure. Asymptomatic patients with severe AVS (transaortic gradient > 70 mm of Hg) also need intervention. Aortic valve replacement is an established procedure of choice for majority of patients with AVS. Aortic balloon valvotomy (ABV) serves as a bridge to surgery and is indicated when valve replacement is risky or needs to be delayed. Patients with congenital AVS present in infancy, childhood or late in life. Bicuspid aortic valve is the usual deformity. ABV is indicated for relief of symptoms and to delay aortic valve replacement surgery.5 The relative contraindication are unicommisural valve and congenital AVS which is a part of hypoplastic left heart syndrome. ABV is performed through the retrograde route using femoral artery. Balloon size recommended for aortic valve dilatation is 90 to 100% of the aortic annulus. The use of larger sized balloons as compared to the aortic annulus results in high incidence of aortic regurgitation. Apart from the retrograde femoral arterial route, aortic valve has been dilated antegradely via femoral vein and through the carotid artery approach especially in the neonates and young infants. The complications are rare (< 1%). However, the incidence is higher in the neonates with critical AVS. The major complications include aortic regurgitation, thromboembolism, ventricular arrhythmias and rarely death. Aortic regurgitation is usually well tolerated and does not require emergency intervention. Both the short and the long term results are extremely gratifying. The success rate is about 97-98% with a restenosis rate of less than 2-3%. Redilation of aortic valve if required in infants and children can be done safely.

Rheumatic AVS invariably occurs in association with mitral stenosis.16 BV of aortic valve is performed using Mansfield single or double balloon technique and simultaneously BMV is performed. ABV is quite effective in rheumatic AVS as patients are young and morphological abnormality is commissural fusion. ABV reduces transaortic gradients effectively and helps in delaying valve replacement complications are a few and include increase in aortic regurgitation.

Degenerative aortic valve stenosis is the most common valvular heart disease seen in adults and elderly in the western world. Surgical valve replacement is treatment of choice to improve survival and ameliorate symptoms, however many patients are declined surgery because of advanced age and comorbidities. For this subgroup of patients, balloon aortic valvuloplasty (BAV) was proposed in 1985 by Cribier.2 Although met with initial enthusiasm, BAV was largely abandoned because of lack of long lasting results. ABV of aortic valve improves over all haemodynamics in short term and makes some patients better candidates for a valve replacement. In some patients, the balloon dilatation is needed repeatedly due to recurrent restenosis. A recent development for these patients has been application of brachytherapy after the dilatation of aortic valve and also for some cases the percutaneous aortic valve replacement.

Pulmonary valve stenosis (PVS)
PVS is invariably congenital. Balloon valvotomy is procedure of choice for treating all severity of isolated PVS in neonates, infants, children, adults and older patients. It was proposed by Semb3 in 1979 but was successfully performed and reported for the first time by Kan4 in 1982. The presence of symptoms like fatigue, dyspnoea or right sided heart failure are indications for pulmonary BV. In the absence of symptoms, transpulmonic gradient of more than 50 mm Hg or right ventricular (RV) pressure of > 50% of systemic pressure in the presence of normal RV contractility demand intervention on the pulmonary valve. In the neonates, high pulmonary vascular resistance and poor RV function can result in an underestimation of transpulmonic gradients. The relative contraindication is a dysplastic pulmonary valve. Vascular access is obtained via the femoral venous route. The balloon size recommended for the pulmonary valve dilatation is 100 to 120% of the annulus. Pulmonary BV effectively reduces RV systolic pressure and transpulmonary gradients in most patients. Complications are extremely rare (<1%) and are usually transient. Pulmonary regurgitation occurs in some patients but is mild and well tolerated. Both the short and the long term results are extremely gratifying. The success rate is about 97-98% with a restenosis rate of less than 2-3%. Surgery is practically not utilized for treatment of pulmonary valvular stenosis and balloon dilatation has become the preferred treatment.

Tricuspid valve stenosis (TVS)
Aetiology of TVS is mostly rheumatic and is associated with MVS. Balloon dilatation of TVS is safe, effective and can be done by Inoue or other techniques. Simultaneous BV of both mitral and tricuspid valves is feasible and produces excellent early and mid term follow-up results.^15,16

Multivalve stenosis
In rheumatic heart disease, stenosis of two (mitral + tricuspid, mitral + aortic) or three (mitral + tricuspid + aortic) valves is still seen in India. Successful dilatation of multivalve stenosis using double balloon and or Inoue technique has been reported with excellent early and mid term results. Our group15,16 combined balloon mitral valvotomy with dilatation of tricuspid valve in ten patients using the Mansfield double balloon technique in six and the Inoue balloon technique in four patients. Haemodynamic parameters revealed an increase in TVA from 1.11 ± 0.41 cm2 to 2.52 ± 0.69 cm2 (p < 0.005), fall in mean valve gradient from 11.80 ± 4.70 to 4.14 ± 3.40 mmHg along with increase in cardiac index from 2.47 ± 0.38 to 3.46 ± 0.42 L/m2 (p < 0.005). The ratio of effective balloon to annulus diameter measured on right ventricular angiography was 90 to 110% in nine patients in whom degree of tricuspid regurgitation (TR) remained unchanged. No patient was subjected to tricuspid valve repair or replacement. Continuous relief of stenosis has been reported upto three years of follow-up.

2. Percutaneous Valve Repair and Valve Replacement
   We are now embarking on a new era in the treatment of valvular heart disease with the introduction of percutaneous and minimally invasive devices and techniques to address valve dysfunction without conventional surgical repair / replacement. Pathology of all 4 cardiac valves has now been treated in early stage clinical feasibility (pilot) trials. There are at least 30 percutaneous valve programmes currently being developed by 24 different companies. Two of the percutaneous aortic valve devices and 5 of the mitral valve devices are in various stages of clinical trials, ranging from feasibility to pivotal at the present time.


Percutaneous aortic valve replacement
A percutaneous heart valve (PHV) was developed to treat high surgical risk or inoperable patients with degenerative aortic stenosis by Dr. Alain Cribier. This PHV was successfully implanted for the first time on April 16th, 2002 in a patient with inoperable aortic stenosis and life threatening comorbidities. Since then, PHV has been implanted in a series of 36 patients.17 There is an antegrade approach through the vena cava, crossing the interatrial septum, the mitral valve and making a loop and then crossing the aortic valve with the stented valve from the left ventricle. Rapid pacing (220 beats / min) is used to reduce the flow across the valve during the balloon deployment of the stented valve. The recently reported results of PHV in inoperable patients with calcific AS demonstrates feasibility. Despite the successful implantation and amelioration of symptoms in the majority of patients in this initial series, the problem of perivalvular leak is the major limitation at present. The issue of device implantation via a retrograde or antegrade approach is also in question. Despite early limitations, this approach to treat AS has enormous potential, and we should look forward to further refinements in device composition, delivery, and subsequent improvement in results.

Percutaneous mitral valve repair
Mitral valve repair is preferred surgical approach for treatment of severe mitral regurgitation (MR). The valve repair is usually applied to MR resulting from mitral valve prolapse. A variety of surgical procedures for mitral valve repair are in use including annuloplasty, leaflet repair and chordal reconstruction. Recently, a percutaneous method based on the surgical principle of double-orifice repair has been developed. The trans-septal approach is used to deliver a clip device that can grasp the central mitral leaflet edges to create a double orifice. After extensive testing in animals showed persistence of a double orifice for more than six months, a U.S. Food and Drug Administration Investigational Device Exemption-approved phase I safety and feasibility trial (EVEREST : Endovascular Valve Edge-to-Edge Repair Study) was initiated. The short-term and six-month results of this trial in 27 patients with moderate-to–severe or severe MR were recently reported.18 Of 27 patients entered into the trial, 14 (52%) had the mitral clip device in place with 2+ or less mitral regurgitation at 6-month follow-up. Nine patients (33%) had undergone surgical correction. This device is now in a multicentre pivotal trial (EVEREST II) with 2 : 1 randomization against conventional mitral valve repair in 30 centres in the United States. This is an exciting field and it is too early to determine what will be the future role of these procedures.

Percutaneous pulmonary valve replacement
Pulmonary regurgitation occurring secondary to surgical or transcatheter intervention is usually benign and tolerated in short time. However, pulmonary regurgitation on long term can produce chronic right ventricular volume over-load, ventricular dilatation, impairment of systolic and diastolic dysfunction. In the long run, heart failure, sudden death and arrhythmias can result. Surgical pulmonary valve replacement can be performed with very low mortality. Dr. Philipp Bonhoeffer and Colleagues developed a new percutaneous technique for pulmonary valve implantation with a bovine jugular venous valve sutured inside a stent and implanted using a delivery system. Khambakone and Bonhoeffer19 has shown the feasibility, safety and efficacy of pulmonary valve implantation in humans. Their experience currently is of around 100 cases.

Percutaneous valve interventions are rapidly evolving. Effective palliation of valvar stenosis can be provided by non-operative dilatation in selected cases. Percutaneous replacement of pulmonary valve is the most exciting development for treatment of regurgitation lesions. Percutaneous mitral valve repair and aortic valve replacement are clinically feasible and a lot is expected in future.

References

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Consultant Cardiologist, Bombay Hospital, Mumbai - 400 020.