Although most percutaneous interventional procedures involve the coronary arteries, major developments in non-coronary transcatheter cardiac procedures have occurred in the past 20 years. In adults the commonest procedures are balloon mitral valvuloplasty, ethanol septal ablation, and septal defect closure. These problems were once treatable only by surgery, but selected patients may now be offered less invasive alternatives. Carrying out such transcatheter procedures requires supplementary training to that for coronary intervention. Acquired mitral stenosis is a consequence of rheumatic fever and is commonest in developing countries. Commissural fusion, thickening, and calcification of the mitral valve leaflets typically occur, as well as thickening and shortening of the chordae tendinae. The mitral valve stenosis leads to left atrial enlargement, which predisposes patients to atrial fibrillation and the formation of left atrial thrombus. Stenotic mitral valve showing distorted, fused, and calcified valve leaflets. (AMVL=anterior mitral valve leaflet, PMVL=posterior mitral valve leaflet, LC=lateral commissure, MC=medial commissure) In the 1980s percutaneous balloon valvuloplasty techniques were developed that could open the fused mitral commissures in a similar fashion to surgical commissurotomy. The resulting fall in pressure gradient and increase in mitral valve area led to symptomatic improvement. Today, this procedure is most often performed with the hourglass shaped Inoue balloon. This is introduced into the right atrium from the femoral vein, passed across the atrial septum by way of a septal puncture, and then positioned across the stenosed mitral valve before inflation. ### Patient selectionIn general, patients with moderate or severe mitral stenosis (valve area < 1.5 cm2) with symptomatic disease despite optimal medical treatment can be considered for this procedure. Further patient selection relies heavily on transthoracic and transoesophageal echocardiographic findings, which provide structural information about the mitral valve and subvalvar apparatus. Top: Diagram of the Inoue balloon catheter positioned across a stenosed mitral valve. Bottom: Fluoroscopic image …