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 usedwith 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 Ψ 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 (1Ψ 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 (2Ψ or more) was significantly lower in the LPZ BMC (18%) vs. HPZ BMC (32.2%) (P F 0.05). Moderate to severe MR (3Ψ/4Ψ) was also less in LPZ BMC (2.8%) vs. HPZ BMC (8.2%) (P F 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 F 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.