Fig. 4.1
The Inoue balloon. Kanji Inoue, a Japanese Cardiac Surgeon, developed the idea that a degenerated mitral valve could be inflated using a balloon made of strong and pliant natural rubber in 1982. The mechanism and effectiveness of his balloon technique is the same as the abandoned surgical technique of closed mitral commissurotomy
Case Study
A 63 year old lady was referred for consideration of PBMV. She had been fit and well until 2003 when she developed sudden extreme dyspnoea due to the onset of atrial fibrillation (AF) and rapid ventricular response. A diagnosis of mitral stenosis was made on transthoracic echocardiography (TTE) and she responded well to medical therapy, comprising an effective combination of heart rate control, anticoagulation and diuretics. However, over recent years she became progressively more limited by exertional breathlessness, and was in New York Heart Association (NYHA) Class III by the time of referral. Past medical history included diabetes mellitus and the patient could not recall having childhood rheumatic fever. Clinical examination revealed a systolic murmur and loud, rumbling apical diastolic murmur. First heart sound and the pulmonary component of the second heart sound were normal. Jugular venous pressure was not elevated and there was no ankle oedema. Chest was clear. 12-lead electrocardiography showed rate-controlled AF with frequent ventricular ectopy and bigeminy.
Coronary angiography demonstrated no coronary artery disease with a right dominant system and good LV function. No mitral regurgitation was noted at angiography or subsequent TTE evaluation. Pulmonary artery systolic pressure was 55 mmHg with a mean of 28 mmHg. In-patient TOE assessment was organized prior to PBMV (Videos 4.1, 4.2, and 4.3). Due to the finding of left atrial appendage thrombus, the planned procedure was deferred for 6 months until the clot resolved after increased anti-thrombotic medication. At peri-procedural TOE several months later, severe mitral stenosis was confirmed (Figs. 4.2a–d; Video 4.4). PBMV was then successfully performed (Videos 4.5, 4.6, 4.7, 4.8, and 4.9).
Fig. 4.2
Echocardiographic assessment mitral stenosis severity. (a) Continuous wave Doppler through the stenosed valve confirming a high instantaneous peak velocity, corresponding to a peak gradient of 22 mmHg. (b) Mitral valve area measured by pressure half time of 0.98 cm2. (c) Velocity time integral analysis showed a mean gradient of approximately 12 mmHg. (d) Three-dimensional planimetry demonstrated a mitral valve area of 1.1 cm2
With careful pre-procedural patient selection, PBMV is associated with excellent success rates and low rate of complications. The most serious adverse event is the occurrence of acute severe mitral regurgitation, usually resulting from a tear in one of the valve leaflets or the subvalvular apparatus. This complication can lead to pulmonary oedema and hemodynamic compromise, necessitating urgent surgical MVR. Other serious complications during PBMV usually relate to the transseptal puncture. The ideal site for puncture is at the region of the fossa ovalis. Occasionally, the sharp needle can inadvertently traumatize other cardiac structures leading to cardiac tamponade or serious blood loss.
PBMV does not provide permanent relief from mitral stenosis. Regular follow-up is mandatory to detect re-stenosis in this patient cohort. Up to 70–75 % of individuals can remain free of re-stenosis 10 years following the procedure, but this number falls to about 40 % 15 years post valvuloplasty.
Percutaneous Mitral Valve Repair in Mitral Regurgitation
Mitral regurgitation can be caused by degenerative valve disease (mitral valve prolapse in 20–50 % of cases), or heart muscle disease (13–30 %), rheumatic heart disease (3–20 %), endocarditis (10–12 %) or, rarely, congenital heart disease. These causes may be grouped into three main descriptive categories:
- 1.
Functional regurgitation (both ischaemic and non-ischaemic)
- 2.
Degenerative regurgitation (mitral valve prolapse)
- 3.
Other causes (including post-rheumatic, post-endocardits, congenital).
In patients with functional mitral regurgitation, whether associated with ischaemic or non-ischemic heart disease (i.e. dilated cardiomyopathy), the valve leaflets are intrinsically normal but leaflet mobility is restricted due to displacement of the papillary muscles, in turn due to LV dilatation and/or dilatation of the valve annulus. In contrast, degenerative mitral valve disease is characterised by myxomatous degeneration of the valve leaflets and changes in the sub-valvular apparatus including stretching and/or rupture of the chordae tendineae.
Patients with severe symptomatic mitral regurgitation have a poor prognosis with an annual mortality rate of 5 % per year without surgical intervention. Mitral valve surgery (repair or replacement) is the second commonest valve operation performed in the developed world according to figures reported to the Society for Thoracic Surgeon (STS) Database in 2002. Patients with severe mitral regurgitation with evidence of LV dysfunction or dilatation are currently recommended for surgery whether they are symptomatic or not. If considered too high risk for surgery, a percutaneous option to mitral valve repair is sometimes possible. The most established system of repair is an edge-to-edge reconstruction while the heart is beating – the MitraClip® system (Abbott Vascular, CA, USA; Fig. 4.3a–c).
Fig. 4.3
Edge-to-edge reconstruction technique. (a) Surgical repair. The edge-to-edge repair has been used as a surgical technique in open chest arrested heart surgery for the treatment of mitral regurgitation since the early 1990s, and is known as the “Alfieri Technique” after its progenitor. A portion of the anterior leaflet is sutured to the corresponding portion of the posterior leaflet creating a point of permanent coaptation (“approximation”) of the two leaflets. When the edge-to-edge suture is placed in the middle of the valve, the valve will have a functional double orifice during diastole, hence the alternate name of the “Double Orifice Repair”. The valve can still open on both sides of the suture, allowing adequate diastolic blood flow through the valve. The suture assures that the two leaflets come together properly, as required, during systole. Tissue approximation is increasingly maintained over time by the healing response that takes place between the sutured leaflets, gradually reducing the need for the mechanical support provided by the stitches. The Alfieri surgical repair has been successfully used with mid-term follow-up to treat all of the primary (degenerative) aetiologies of mitral regurgitation. The new valve geometry resulting from edge-to-edge repair will have a smaller effective diastolic orifice size than prior to the procedure, just as is expected after valve repair with adjunctive annuloplasty or after valve replacement. A normal mitral valve has an effective diastolic orifice area of around 6.0 cm2. The edge-to-edge repair technique typically reduces the effective diastolic orifice area by 40–50 %, without associated significant valvular diastolic pressure gradient or stenosis over time. In the majority of edge-to-edge procedures, most surgeons insert an annuloplasty ring at the time of index surgery even if the mitral valve annulus is not significantly dilated in order to reduce the likelihood of re-operation. (b and c) MitraClip® system. (b) An atrial view of the deployed device grasping both leaflets of the mitral valve. As is evident, this percutaneous system is based on the surgical Alfieri procedure. The aim is to create a competent double orifice valve by suturing the free edges of the middle part of the anterior mitral valve leaflet (A2) to the corresponding part of the posterior valve leaflet (P2). (c) The device comprises a cobalt-chromium alloy covered with polypropylene fabric which promotes tissue in-growth. A single size clip has been used to treat patients with functional, mixed and degenerative mitral regurgitation. A dual-arm structure with grippers above the arms assists leaflet capture and approximation on the beating heart
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