Double-balloon mitral CBV*® can significantly increase mitral valve areas without introducing very large, 25-mm diameter balloons. The two balloon catheters can be introduced using one or two transseptal atrial punctures. Long guide wires can be placed in the left ventricle or out into the descending aorta. The two balloons are positioned across the mitral valve and inflated simultaneously. One advantage of using the double-balloon technique is that the larger balloons can be chosen to match each patients mitral valve annulus size to open the mitral commissures without overdilating the mitral valve annulus. The technical difficulties encountered with current doubleballoon techniques may be partially overcome by improving guidewire stiffness and reducing the overall balloon catheter profile. The technique of mitral CBV is continuing to evolve rapidly. Advances in balloon technology and laboratory techniques should improve the ease and speed of performing the procedure.
Mechanism by which CBV Increases Mitral Valve Areas
As observed during the first intraoperative mitral CBV, the principal mechanism by which CBV increases mitral valve area is by splitting fused commissures. Detailed echocardiographic studies in a series of patients undergoing mitral CBV have shown that after mitral CBV by the double-balloon technique, the transverse diameter of the mitral valve is increased, as are the angles of opening of both the anterior and posterior commissures. Subvalvular chordal fusion and retraction and valve thickening and calcification are not usually altered by CBV. itat on
Early Results of Mitral CBV
The hemodynamic results of mitral CBV are summarized in Table 1. Inoue et al demonstrated reductions in left atrial pressures (from 20 to 9 mm Hg) in six patients. Other studies using single mitral balloon techniques showed that the average mitral valve areas can increase from 0.7 or 0.9 cm2 up to 1.3 to 1.6 cm after CBV Results of some double-balloon procedures are included in these reports, which limits the review and comparison of the results achieved by different techniques.
Table 1—Immediate Hemodynamic Results of Mitral Catheter Balloon Valvuloplasty
|Author||Ref.||No. of Patients||MeanAge,yr||Before CBV||Immediately After CBV|
|Inoue et al||1||6||42||—||20||16||—||—||9||6||—|
|Lock et al||4||8||15||3.8t||32||21||.7||4.9||27||10||1.3|
|R. McKay et al||5||18*||49||4.3||23||15||0.9||5.1||18||9||1.6|
|Palacios et al||6||35*||49||3.9||27||18||.8||4.6||14||7||1.7|
|Babic et al||7||3||44||7.1||21||17||—||—||14||8||—|
|Zaibag et al||8||9||25||2.6f||—||15||.7||3.0||—||5||2.0|
|CR McKay et al||9||24||41||4.3||28||16||1.0||5.0||16||6||2.2|