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Pressure zone used and the occurrence of mitral regurgitation in Inoue balloon mitral commissurotomy.

Mitral regurgitation (MR) is a known complication of Inoue balloon mitral commissurotomy (BMC) and has been variously ascribed to the presence of severe subvalvular pathology (SVP), preexisting MR, calcification, or oversizing. The pressure zone used--with the low pressure zone (LPZ) the lower half of the spectrum of sizes available out of a single balloon, and the high pressure zone (HPZ) the upper two levels, i.e., within 2 mm of its maximum size--could have a bearing on the occurrence of MR, but has not been studied before. We analysed 251 consecutive patients (mean age 28.6 + 9.7 years), undergoing BMC from October 1993 onwards, with pliable, non-calcific, splittable (bilateral dark zones present) valves with not more than trivial MR (1 + in grades of 1-4). Balloon sizing was done with standard formula using height with stepwise dilatation starting 2 mm below the reference size. Thirty-two patients additionally had severe SVP. Patients were divided into two groups, HPZ-BMC and LPZ-BMC, depending upon the final balloon size needed for a successful result. Incidence of MR (2+ or more) was significantly lower in the LPZ BMC (18%) vs. HPZ BMC (32.2%) (P < 0.05). Moderate to severe MR (3+/4+) was also less in LPZ BMC (2.8%) vs. HPZ BMC (8.2%) (P < 0.05). Amongst patients with severe SVP, 3/15 (20%) developed MR in the LPZ-BMC group (all mild only) as against 8/17 (42%) (P < 0.05) in the HPZ-BMC group with half of them having moderate to severe MR. In 54 patients where the reference size had to be exceeded, no patient (0/8) developed MR as long as the higher size was in the LPZ of the particular balloon used as compared to 17/46 (36.9%) who developed MR when the size used fell in the HPZ. We conclude that the pressure zone used has a strong bearing on the occurrence of MR in Inoue BMC and that a low-pressure strategy could avoid MR.