Treatment of Severe Functional Mitral Regurgitation: Is Cardiac
Surgery Always Indicated?

Severe symptomatic functional mitral regurgitation (MR), or ischemic MR, is traditionally an indication for cardiac surgery, as recommended by the current practice guidelines.¹ It is hoped that coronary bypass surgery, combined with either mitral annuloplasty or mitral valve replacement, will improve the patient’s overall cardiac function and symptoms. Debate has surrounded the question whether patients with severe ischemic MR could do just as well with bypass surgery alone without mitral valve repair.

With the superior patency rates of drug-eluting stents (DES), multivessel coronary interventions and left main coronary interventions have become common in our clinical practice. The following case illustrates the percutaneous management of multivessel coronary artery disease (CAD) associated with severe functional MR.

Case Report. A 77-year-old male, who was a long-term smoker, presented with acute dyspnea while at sleep. Two years ago prior, the patient underwent percutaneous coronary treatment of his right coronary artery (RCA) and the obtuse marginal branch with bare-metal stents. Physical examination revealed a blood pressure of 140/80 mmHg, bilateral crackles and a mitral regurgitation murmur. His arterial oxygen saturation was 88% on room air. Electrocardiography showed paroxysmal atrial fibrillation and left bundle branch block. There was mild elevation of the serum troponin level at 1.1 mg/dL.

Cardiac catheterization revealed severe left main coronary artery (LMCA) stenosis as well as severe and diffuse in-stent restenosis of the distal RCA (Figure 1). Left ventriculographyrevealed an ejection fraction of 45%, with severe inferior hypokinesis, mild anterior hypokinesis and severe MR. The patient’s left ventricular end-diastolic pressure was 20 mmHg. The echocardiogram also revealed severe MR on color Doppler (Figure 2A).

The patient was initially considered for coronary bypass surgery and mitral valve repair. However, his pulmonary function test showed that his forced expiratory ventilation was only 25% of the predicted value, and as a result, he was not deemed a good surgical candidate.

Over the next several days, the patient was dependent on intravenous furosemide in order to maintain a > 90% arterial oxygen saturation. He was also treated with an angiotensinconverting enzyme inhibitor and a beta-blocker.

Percutaneous coronary intervention was considered the next best option. An intra-aortic balloon pump was inserted prophylactically. Initially, a 6 Fr Judkins right guide catheter was used for the RCA angioplasty. A Taxus^® 2.5 x 24 mm stent (Boston Scientific Inc., Natick, Massachusetts), a Taxus 2.75 x 28 mm stent, and a Taxus 3.0 x 28 mm stent, were placed sequentially from the distal to the proximal RCA, producing a good angiographic result (Figure 3A).

Next, a 7 Fr XB 3.0 side-holed guide catheter was used to engage the LMCA. A balanced, middle-weight coronary guidewire was placed in the LAD and the obtuse marginal branch. After balloon predilatation of the ostial LAD and the LMCA, a Taxus 2.75 x 12 mm and a Taxus 2.5 x 18 mm stent were implanted in the proximal circumflex artery, and within the restenosed obtuse marginal stent. A Taxus 3.0 x 16 mm stent and a Taxus 4.0 x 12 mm stent were deployed tandemly to cover the proximal LAD and the distal LMCA. To extend the stent coverage to the origin of the LMCA, another Taxus 4.0 x 12 mm stent was implanted in a tandem fashion at 20 atm pressure at the ostial LMCA. The coronary guidewire in the circumflex artery was retrieved and recrossed through the stent strut into the circumflex artery, and kissing-balloon dilatation was performed at the LMCA bifurcation. The final angiographic result is depicted on Figure 3B.

The patient tolerated the procedure well and the intra-aortic balloon pump was removed at the end of the procedure. His clinical condition improved and he was discharged 2 days after the revascularization procedure. Dual antiplatelet therapy was provided indefinitely.

The severity of MR was graded trivial on the echocardiogram performed 2 weeks after discharge (Figure 2B). A left bundle branch block prevailed on the electrocardiogram.

A surveillance coronary angiogram 5 months later showed continued patency of the LMCA, the LAD, the circumflex artery and the RCA. The patient’s left ventricular systolic function was improved and his mitral regurgitation was graded at 1+.

Discussion. Severe functional MR associated with obstructive CAD is associated with poor prognosis, and is an indication for cardiac surgery, as laid out in the current practice guidelines.^1,2 Conventionally, mitral annuloplasty or mitral valve replacement is carried out during coronary bypass surgery. However, the benefits of mitral valve surgery have not been established in a randomized, controlled trial. To date, there are no published data in the surgical literature showing a survival benefit with mitral valve surgery for ischemic MR.

Coronary revascularization alone may provide similar clinical benefit, as compared with those patients having concomitant mitral valve surgery, particularly in elderly patients or those with atrial fibrillation.^3–6 Persistent functional MR is not uncommon, even after mitral annuloplasty, and it mayimply worse prognosis.⁷ Displacement of the papillary muscle is considered a predictor for failure of mitral annuloplasty.⁸ In the absence of myocardial scar, it is not unreasonable to expect that revascularization alone could improve left ventricular function and reduce the severity of MR. Indeed, in selected patients such as those in the index case, PCI with the use of DES may be adequate to provide durable outcomes and improve functional MR.

What are the predictors for regression of severe functional MR with coronary revascularization? In a consecutive series of 92 patients with 3–4+ MR undergoing isolated coronary bypass surgery,⁹ myocardial viability, complete revascularization, perioperative use of beta-blockers and angiotensin-converting enzyme inhibitors were factors correlating with MR regression after surgical revasuclarization. These factors were associated with a reduction of left ventricular systolic and diastolic dimensions. Transient reduction of MR severity during preoperative dobutamine stress echocardiography had been suggested to predict reversibility of moderate functional MR without mitral valve surgery during bypass.¹⁰ Mitral annular diameter, tethering area and displacement of the posterior papillary muscle were associated with persistent MR after annuloplasty in some studies.^8,11,12

Currently, a variety of innovative percutaneous mitral annuloplasty devices are in the stages of early development or in pivotal trials.^13,14 Patients who have complete coronary revascularization and yet continue to experience significant functional MR may be considered for percutaneous mitral annuloplasty in clinical practice in the future. As a result, we can envisage that patients with ischemic heart disease and heart failure due to associated moderate-to-severe functional MR can be managed by percutaneous coronary revascularization if complete revascularization is feasible, and percutaneous mitral annuloplasty can be considered at a later stage if severe MR is still present. Furthermore, if left bundle branch block is present, cardiac resynchronization therapy may also be considered if heart failure symptoms persist.

References

1. Bonow RO, Carabello BA, Chatterjee K, et al. ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (writing Committee to Revise the 1998 guidelines for the management of patients with valvular heart disease) developed in collaboration with the Society of Cardiovascular Anesthesiologists endorsed by the Society for Cardiovascular Angiography and Interventions and the Society of Thoracic Surgeons. J Am Coll Cardiol 2006;48:e1–e148.

2. Perez de Isla L, Zamorano J, Quezada M, et al. Prognostic significance of functional mitral regurgitation after a first non-ST-segment elevation acute coronary syndrome. Eur Heart J 2006;27:2655–2660.

3. Diodato MD, Moon MR, Pasque MK, et al. Repair of ischemic mitral regurgitation does not increase mortality or improve long-term survival in patients undergoing coronary artery revascularization: A propensity analysis. Ann Thorac Surg 2004;78:794–799; discussion, p. 799.

4. Trichon BH, Glower DD, Shaw LK, et al. Survival after coronary revascularization, with and without mitral valve surgery, in patients with ischemic mitral regurgitation. Circulation 2003;108(Suppl 1):II103–II110.

5. Kang DH, Kim MJ, Kang SJ, et al. Mitral valv e repair versus revascularization alone in the trea tment of ischemic mitral regurgit ation. Circulation 2006;114:I499–I503.

6. Kim YH, Czer LS, Soukiasian HJ, et al. Ischemic mitral regurgitation: Revascularization alone versus revascularization and mitral valve repair. Ann Thorac Surg 2005;79:1895–1901.

7. McGee EC, Gillinov AM, Blackstone EH, et al. Recurrent mitral regurgitation after annuloplasty for functional ischemic mitral regurgitation. J Thorac Cardiovasc Surg 2004;128:916–924.

8. Matsunaga A, Tahta SA, Duran CM. Failure of reduction annuloplasty for funct ional i schemic mit r a l r e gur git a t ion. J Heart Valve Dis 2004;13:390–397.

9. Campwala SZ, Bansal RC, Wang N, et al. Factors affecting regression ofmitral regurgitation following isolated coronary artery bypass surgery. Eur J Cardiothorac Surg 2005;28:783–787.

10. Roshanali F, Mandegar MH, Yousefnia MA, et al. Low-dose dobutamine stress echocardiography to predict reversibility of mitral regurgitation with CABG. Echocardiography 2006;23:31–37.

11. Kongsaerepong V, Shiota M, Gillinov AM, et al. Echocardiographic predictors of successful versus unsuccessful mitral valve repair in ischemic mitral regurgitation. Am J Cardiol 2006;98:504–508.

12. Kuwahara E, Otsuji Y, Iguro Y, et al. Mechanism of recurrent/persistent ischemic/functional mitral regurgitation in the chronic phase after surgical annuloplasty: Importance of augmented posterior leaflet tethering. Circulation 2006;114:I529–I534.

13. Mishra YK, Mittal S, Jaguri P, Trehan N. Coapsys mitral annuloplasty for chronic functional ischemic mitral regurgitation: 1-year results. Ann Thorac Surg 2006;81:42–46.

14. Webb JG, Harnek J, Munt BI, et al. Percutaneous transvenous mitral annuloplasty: Initial human experience with device implantation in the coronary sinus. Circulation 2006;113:851–855.