Percutaneous Transluminal Mitral Valvuloplasty
Percutaneous transluminal mitral valvuloplasty (PTMV) changed the approach of cardiothoracic surgeons to mitral stenosis. The technique was developed by Inoue in 1984 but has since been refined. Anatomically, PTMV is of greatest use in patients with the pliability of the mitral valve, clear of substantial calcification or fibrosis.40,41. Suitability of this technique for mitral stenosis can be determined through the application of Abascal’s echocardiographic scoring system. Also known as the Wilkins score, it is essential in its application as it can predict mitral regurgitation following an intervention. The criteria evaluate four key aspects to valvular morphology outlined in Table 2. With respect to the Wilkins criteria, a higher score specifies a more progressed disease and a reduced chance of success with this technique. Surgical mitral valve replacement is recommended for patients in those in which PTMV is not anatomically optimal.42 The surgical basis is via balloon valvuloplasty, this balloon is applied crossing the mitral valve thereby improving leaflet excursion and orifice diameter. The operation is critical in the treatment of rheumatic heart disease as it fractures the rheumatic fusion that has developed. It is also a reliable therapy management option for pregnant women.43
The 1984 paper by Inoue and colleagues was revolutionary as the technique developed allowed mitral commissurotomy without thoracotomy. Post-operative complications following thoracotomy, in patients who are already cardiopulmonary compromised, create a very vulnerable situation for the patient. The initial study consisted of six patients, five of which were successfully managed with this new technique. The procedure was unable to be performed in the remaining patient due to technical difficulties. Interestingly, the Wilkins score was only implemented in 1990, 6 years following this study.44
The balloon is introduced through the saphenous vein and will ascend into the mitral orifice. Across the mitral orifice, the balloon is partially inflated, when fully expanded the balloon will separate the fused commissures via expansile propulsion. Surgically, the balloon is buoyed via a nylon micromesh and changes shape in three stages, depending on the degree of inflation. The micromesh is essential for the shape adaptation that the balloon experiences.44Despite medical advances, the basic premise of this technique has remained the same. As of 2016 Adhikari and colleagues described a similar approach.45 In selected patients, PTMV is now the treatment of choice and is associated with less than a 1% mortality. With any operation, the risk of embolism is always appreciable. However, pre-operative application of transesophageal echocardiography aids in the identification of left atrial thrombi and therefore has limited risk of embolic stroke to 1.1% - 5.4%.46
Furthermore, a review conducted by Satya and colleagues highlighted how PTMV resulted in an estimated doubling of the mitral valve area coupled with a 50% decrease in the transmitral gradient. Long term follow-up highlighted continued functional enhancement with survival rates >80% at 10 years post-operation.47
A randomized controlled trial completed by Reyes and colleagues compared open mitral commissurotomy to PTMV. The study focused upon sixty patients with severe mitral stenosis, none of which were lost to follow up. Even though long-term results were similar and both techniques maintained a desired mitral valve area three years post-intervention, more desirable results were achieved through PTMV (2.4 ±0.6 cm2, vs. 1.8 ±0.4 cm2). Restenosis rates were similar in both groups and less than 40% had cardiovascular symptoms three years post-operation. The trial emphasized the potential complications with PTMV, but also noted superior hemodynamic results and faster recovery due to the eradication of the need for a thoracotomy. This led to a suggestion that those who are anatomically favorable should undergo PTMV rather than open commissurotomy.48