EFFECT OF BALLOON SIZE AND STEPWISE INFLATION TECHNIQUE ON THE ACUTE RESULTS OF INOUE MITRAL COMMISSUROTOMY

Currently percutaneous transvenous mitral commissurotomy (PTMC) is performed by most operators using stepwise inflation of the Inoue balloon beginning at a small diameter and increasing size by a sequence of inflations to nominal diameter. The effect of balloon size on procedure results using the Inoue balloon has not been evaluated. In 260 patients final balloon inflation was to nominal size in 42% of pts, larger than nominal size (overinflated) in 10%, and less than nominal size (underinflated) in 48% of pts. The average number of inflations was 3 (range 1-9). Pressure gradient and Doppler mitral regurgitation (MR) were assessed after each inflation. When MR increased, further inflations were not done. Patients in whom the balloon was overinflated underwent more balloon inflations than those in whom it was inflated to nominal size (5.0 +/- 2.1 vs. 2.9 +/- 1.4, p < 0.01). Those with balloon underinflation had fewer balloon inflations (2.4 +/- 1.2 vs. 2.9 +/- 1.4, p < 0.01). The post PTMC valve area in patients with overinflation was slightly less than those with nominal inflations (1.6 +/- 0.4 vs. 1.8 +/- 0.7), and with underinflation the valve area was no different compared to nominal inflation. Using a stepwise procedure, if mitral regurgitation was noted to increase after a balloon inflation, the procedure would be stopped even if less than an ideal result was achieved. Fewer inflations were done in patients in whom the balloon was inflated to less than nominal size because of the appearance of mitral regurgitation. No statistical differences in the incidence of increased mitral regurgitation greater-than-or-equal-to 2+ were noted when the balloon was overinflated (4%), inflated to nominal size (8%), or underinflated (8%). Since an ideal method for selecting balloon size has not been determined the ability to increase inflated balloon diameter by stepwise dilatation may maximize the gain in area and limit the increase in MR during PTMC.