Advances in the Management of Valvular Heart Diseases

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Citation
Asia-Pacific Cardiology 2008;2(1):62-3
DOI
https://doi.org/10.15420/apc.2008:2:1:62

Valvular heart disease is a paradigm of the changing aetiology of human disease. We have witnessed dramatic changes in the incidence of rheumatic heart disease in the industrialised world. The frequency of valve disease is still high due to the rise in new diseases such as degenerative valve disease. In developing countries the prevalence has increased due to rheumatic burden, degenerative lesions and ‘emerging valve disease’. The three main modern sources of the disease are AIDS, drug-related effects from drugs such as appetite suppressants and new types of idiopathic disease such as ‘antiphospholipid syndrome’.1

Surgical interventions for valvular heart disease are increasing due to increases in average life expectancy, changing demographics and increased accessibility to and affordability of sophisticated healthcare for the populations of developing countries.

The era of valvular therapy was ushered in on the afternoon of 10 June 1948 when Dr Charles Philamore Bailey2 performed the first closed mitral commissurotomy at the Episcopal Hospital in Philadelphia, US. The fact that Dr Bailey transported his patient from Philadelphia to Chicago, Illinois on the 10th post-operative day (as an exhibit for the scientific session of the American College of Chest Physicians) illustrates the competitive environment rampant at that time. The first open heart surgical procedure, mitral valve repair, was performed by Dr Forest Dewey Dodrill on 3 July 1952 at the Harper Hospital in Detroit, Michigan.3 Fifty-six years later, valvular therapy has seen dramatic and rapid advances, with seminal contributions from many experts from all parts of the world.

The introduction of mechanical prostheses and bioprosthesis gave tremendous impetus to replacement therapies. Scores of new valves were introduced to the market, although the US Food and Drug Administration (FDA) approved only a few of these. Research institutes from developing countries introduced indigenous valves (Chitra Valve, India; Biomed, Mexico; and Braile Biomedica, Brazil). These valves provided acceptable economically viable long-term solutions. There were also landmark innovations in surgical techniques, notably the ‘Ross I’ (pulmonary autograft) 4 and ‘Ross II’ by Sir Donald Ross. Reparative valve work was soon found to be superior to conventional replacements, the ‘torchbearer’ of such work being Dr Alain Carpentier (the ‘French Correction’).5

Simultaneously, rapid strides in percutaneous therapy were applied to the treatment of valvular lesions. ‘Balloon’ mitral therapy and pulmonary and aortic valvotomy are examples of such treatments. Dr Randall Chitwood of North Carolina, US, explains advances in robotic cardiac surgery in reference 6.

Percutaneous repair of mitral incompetence,7 minimally invasive mitral valve interventions8 and percutaneous/transapical replacement of the aortic valve in surgically unfit elderly patients are interesting developments attracting unprecedented enthusiasm worldwide.9,10 Percutaneous replacement of the pulmonary valve is now routinely practised by Dr Bonhoeffer’s team at the Children’s Hospital in Boston.11 This article reviews the recent advances made in valvular therapy.

Mitral Valve Disease

After the first successful mitral commissurotomy in 1948, Lillehei et al. reported the first open mitral commissurotomy in 1956 followed, in the same year, by a successful mitral valve repair via annuloplasty. It was Dr Alain Carpentier, however, who in 1971 revolutionised mitral valve repair. Harken et al. first used a mechanical heart valve, but it was Dr Starr’s results that truly ‘changed the scene’. Ross and Barratt- Boyes reported the first use of homografts in 1962 and Carpentier first used a xenograft in 1965.

Currently, for uncomplicated isolated mitral valve stenosis, balloon valvotomy is the preferred modality. In developing countries, however, closed mitral commissurotomy is still widely practised and has yielded gratifying results. Several patients, operated on as long as 20 years ago, have undergone successful replacement, and a minimally invasive valvotomy via a mini-left thoracotomy with the ‘Tubbs’ dilator guided across the stenotic mitral valve by intra-operative transoesophageal echocardiography has been devised. The advantage of this procedure is that the patient can be discharged the day following surgery with a significant cost reduction and superior results compared with balloon valvotomy.

Mitral valve repair is undoubtedly the procedure of choice whenever feasible. Surgeons should be aware of thomboembolic episodes (TEEs). With the variety of procedures devised for lesions, a careful valve analysis and combinations of various techniques, excellent results can be achieved. There is a wide choice of both rigid and flexible annuloplasty rings available (e.g. Duran, Sorin, Calvin-Galloway, Cosgrove and Gregori). Minimally invasive repair with remote cardiopulmonary bypass (CPB) and ‘heart port’ techniques are standardised and have largely replaced robotic repairs, which are expensive and time-consuming and provide no added advantages. A variety of innovative techniques and devices are being developed for the percutaneous management of mitral insufficiency. More than 30 devices are in development, from early stages to human pivotal trials.

Two devices for the management of degenerative myxomatous disease of the mitral valve replicate the ‘Alfieri edge-to-edge’ surgical repair. One of those devices, the evalve mitraclip, is currently in a pivotal trial. Other devices address functional mitral regurgitation via a variety of techniques for performing mitral valve annuloplasty. The majority of devices take advantage of the proximity of the coronary sinus to the posterior mitral annulus to deliver devices that re-model the mitral annulus. Two devices perform septal lateral cinching, decreasing the anterior posterior diameter of the mitral annulus and correcting leaflet malcoaptation. The replacement of diseased valves is experiencing a changing trend towards usage of more bioprostheses, with the advent of durable, third-generation bovine pericardial bioprostheses. Patients with a life expectancy of less than 10 years are offered porcine bioprosthesis. ‘Ross II’ (the pulmonary autograft replacement of the mitral valve) is another potential ideal valve substitute; however, it is currently used by only a few select treatment teams. Mitral homograft (Acar and Carpentier) initially offered a ray of hope; however, it did not stand the test of time and has now largely been abandoned as a treatment option. In our experience, all six implanted homografts developed calcification and valve deterioration within six months.

Aortic Valve Disease

In 1951 Bailey reported the first closed transventricular aortic commissurotmy for aortic stenosis. This produced severe aortic regurgitation and was abandoned in favour of valve replacement, which produced excellent results. Yacoub et al. pioneered aortic valve repair in the bicuspid valve and valve-sparing root replacement by Dr T David. There are currently a host of choices for mechanical valves (‘tilting disc’ claims to offer superior haemodynamic performance) and newer designs in bovine pericardial valves (St Jude Trifecta and Sorin Freedom Solo). Newer-generation ‘stentless’ bioprosthesis are now available and provide a larger effective orifice area. In suitable patients, the best procedure seems to be the Ross procedure, which consistently performs better than any other prosthetic replacement. Developments in minimally invasive techniques enable aortic valve replacement through a right upper thoracotomy and hemisternotomy. A percutaneous technique was pioneered by Cribier; however, the constraints of the required large assembly device obviated the introduction of a larger prosthesis, The most important current development is the ‘Nitinol stent-mounted xenograft’, which can be implanted transapically in an aortic position. This seems to be promising technique that avoids many of the adverse features of percutaneous procedures such as smaller valves, limb complications, cardiovascular accident and fast ventricular pacing.

Pulmonary Valve Disease

Balloon pulmonary valvotomy is a standard accepted modality of treatment for isolated pulmonary valvular stenosis. There are exciting developments in the percutaneous replacement of pulmonary valves (Melody Valve), which seems to be comparatively simple compared with percutaneous aortic valve replacement. Until this technique is widely available, surgeons must rely on the time-tested orthotopic pulmonary valve replacement with porcine or bovine pericardial bioprosthesis. We have significant experience of pulmonary valve replacement with gratifying results and negligible morbidity and mortality.

Tricuspid Valve Disease

Organic tricuspid disease is not uncommon in those developing countries with a high incidence of rheumatic heart disease. It is amenable to both valvotomy and bicuspidisation of the valve and ‘De Vegas’ repair. Various modifications of ‘De Vegas’ are still used in some centres. However, a ring annuloplasty appears to be a more cogent option. Tricuspid valve replacement in intravenous drug users, Ebstein’s disease and organic rheumatic tricuspid disease is generally performed with a porcine or bovine bioprosthesis.

References
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