Inoue Balloon Mitral Valvuloplasty in Double-Orifice Mitral Stenosis

Double-orifice mitral valve (DOMV) is a rare congenital anomaly characterized by the presence of 2 mitral orifices, each possessing an independent chordal attachment to a papillary muscle.1,2 DOMV may occur as an isolated anomaly or, more often, in association with other congenital anomalies like endocardial cushion defect, bicuspid aortic valve and coarctation of the aorta.1,3 Based on an echocardiographic study, Trowitzsch et al.4 classified DOMV into 3 types: complete bridge, incomplete bridge and hole. The complete bridge type is characterized by the presence of a fibrous tissue visible from the leaflet edge through the valve ring. In the incomplete form, however, the fibrous connection occurs only at the leaflet edge. In the hole type, the secondary orifice with its subvalvular apparatus occurs in the lateral commissure and is visible only at the mid-leaflet level. We recently encountered an incomplete bridge stenotic DOMV. Inoue-balloon mitral valvuloplasty (BMV) was successfully used to split the fibrous connection between the leaflets.5 We now present 6 additional patients with stenotic, incomplete bridge DOMV, who also successfully underwent BMV, with emphasis on the technical aspects of the procedure. Case Reports. BMV was performed in 7 symptomatic patients with stenotic DOMV, including the previously reported patient.5 The patients included 2 Chinese (Cases #2 and #5), one Jordanian (Case #4) and 4 Koreans. Their brief clinical data are shown in Table 1. Two patients (Cases #3 and #8) had cerebral embolic events at 6 weeks and 8 months before BMV, respectively. In each patient, cardiac auscultation showed an accentuated first heart sound, opening snap and diastolic rumbling murmur. Transthoracic 2-dimensional echocardiography (Figure 1) revealed a double-orifice mitral valve at the leaflet level in each patient. Both orifice sizes were equal or nearly equal in 3 patients (Cases #1, #4 and #5) and unequal in the other 4 patients, with the anterolateral orifice being much smaller than its counterpart. None of the valves had fusion of the commissures or significant subvalvular diseases. Color Doppler examination showed 2 separate mitral diastolic flows in all but 1 patient (Case #3), in whom no flow was demonstrated though the smaller anterolateral orifice. None of the patients had left atrial thrombus by transesophageal echocardiography. After informed written consent, one-stage BMV was performed using the Inoue-balloon technique performed by one of the authors (JSH). Transseptal catheterization and left atrial placement of the balloon catheter were performed in the usual manner.6–8 Balloon crossing of the posteromedial orifice was readily accomplished using either the vertical approach9 or the direct method (Case #2).8 Crossing of the anterolateral orifice proved difficult in the first 2 patients because the orifice was located more cranially, making it impossible to align the distal balloon catheter with the orifice/apex (ventricular) axis. Successful crossing was achieved only with the catheter sliding technique.8 In both cases, after a single ineffective dilation of the anterolateral orifice at 8 mm and 14 mm balloon diameter, respectively, no further attempts were made to cross the orifice with the balloon catheters. In the other 5 patients, crossing of the anterolateral orifice was not successful. In all patients, the posteromedial orifices were dilated using the stepwise dilation technique.6,8 Following each dilation procedure and after confirming no significant mitral regurgitation or leaflet tears by echocardiography, the balloon size was increased by 1 mm. Balloon catheter selection and balloon sizing data are shown in Table 1. In the first 3 patients, the smallest PTMC-24 balloon catheters were used. Subsequently, balloon catheter selection was based on the balloon reference size derived from the height-based formula described previously.8 Balloon catheters, which matched the balloon reference size, were used. The procedure was terminated when the waist of the inflated balloon suddenly disappeared, and echocardiography confirmed separation of the mitral valve septation, resulting in a single enlarged orifice (Figure 1). At the end of the procedure, the mean left atrial pressure, transmitral pressure gradient and mean pulmonary artery pressure decreased in all patients (Table 1). Repeat left ventriculography showed no mitral regurgitation in 6 patients. In the other patient (Case #2), the 1+ regurgitation remained unchanged. All patients remained asymptomatic at the latest follow-up visits 9–30 months after BMV. Follow-up echocardiography showed no mitral valve restenosis as defined by 50% reduction in the mitral valve area (Table 2). Discussion. The isolated form of DOMV is more frequently observed in the bridge type,1,2 and is usually associated with no significant hemodynamic abnormality. However, over the past 30 months we have encountered 7 moderately symptomatic, middle-aged patients with stenotic DOMV of incomplete bridge type. Their clinical presentations and physical findings were indistinguishable from those in rheumatic mitral stenosis. However, vigilance acquired from the experience in the first case contributed to expeditious echocardiographic identification of the incomplete bridge DOMV in the subsequent patients. We have demonstrated that Inoue BMV can be safely and successfully applied to split the fibrous septation, resulting in a single enlarged mitral orifice. Based on our experience in this study, several important technical tips and guidelines have evolved. First, transseptal catheterization and left atrial placement of the balloon catheter can be performed in the usual manner.6–8 Second, balloon crossing of the posteromedial orifice is simple and stepwise dilations of the latter orifice alone are sufficient to split the fibrous bridge between the two leaflets. The original strategy was to dilate each orifice in turn. However, dilation attempts of the anterolateral orifice were either abandoned (Cases #1 and #2) or not made (Cases #3–7) because the anterolateral orifice was located more cranially, making it impossible to align the distal balloon catheter with the orifice/apex (ventricular) axis. Therefore, balloon crossings of the orifice were exceedingly difficult in the first 2 cases and failed in the other cases. Third, balloon catheter selection can be based on the height-derived reference size8 as in ordinary cases of mitral stenosis. And last, stepwise dilations can be initiated at a balloon diameter of 4 mm less than the reference size. Instead of 9–18 inflations using 1 or 2 catheters in the first 3 cases, adaptation of the above guidelines facilitated BMV procedures with 3–6 balloon dilations using a single balloon catheter in the last 4 cases. In summary, in symptomatic patients with stenotic DOMV of incomplete bridge type, Inoue BMV with stepwise dilations applied only to the posteromedial orifice appears to be a safe and effective therapeutic modality.

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