As discussed in Chapter 63, the surgical treatment of primary valvular heart disease that leads to LV dysfunction or heart failure is now widely accepted. However, patients who have valvular dysfunction secondary to, or in association with, a primary cardiomyopathy pose a much more difficult management problem. The following discussion focuses on the impact and outcome of valve repair or replacement for patients with a dilated cardiomyopathy and secondary mitral regurgitation (MR).¹⁵ However, much of the same controversy relates to the decision to repair or replace the regurgitant mitral valve in the patient with an ischemic cardiomyopathy and a low LVEF who is undergoing CABG.

MR is commonly observed in patients with heart failure and is associated with a poor prognosis. Progressive LV remodeling, characterized by increasing LV dilation with change to a more spherical shape, can result in functional MR secondary to annular dilation, papillary muscle displacement, and chordal tethering. The functional MR leads to an increased preload, increased wall tension, and increased LV workload, all of which contribute in a positive feedback loop to progressive heart failure. The presence of MR itself is an independent risk factor for poor outcome, in both nonischemic and ischemic forms of the disorder. Even uncorrected mild MR, as well as moderate to severe MR associated with ischemic cardiomyopathy, is associated with reduced long-term survival. In addition, MR is a progressive disorder in which the regurgitation-related LV volume overload promotes further LV remodeling, leading to worsening of the problem.

Mitral valve repair or replacement to restore valve competency is a well-established procedure when symptoms of heart failure are present and the primary disease is of the valve leaflets (see Chapter 63). More specifically, however, interest has focused on functional or secondary mitral insufficiency, in which the valve leaflets are anatomically normal but do not fully coapt because of annular dilation and restricted leaflet motion secondary to increased ventricular size and sphericity. Such remodeling of the ventricle often is associated with an LVEF of 40% or less and heart failure symptoms of NYHA class III or class IV. Surgery in this situation is controversial, because the MR is the consequence and not the cause of LV dysfunction, and the prognosis is therefore more specifically related to the underlying cardiomyopathic process.

Although it is clear that the advent of secondary mitral insufficiency is associated with a worse prognosis, it is unclear whether the worse outcomes stem from the MR itself or whether MR is simply a marker for worsening heart failure and the correction of MR will improve symptoms or survival. Specifically, can surgery be done in patients with advanced heart failure and LV dysfunction with an acceptable operative mortality? Does the available evidence show that the elimination of MR results in LV reverse remodeling or improved survival? Conventional teaching has been that surgical correction of MR in patients with advanced heart failure patients with poor LV function is associated with prohibitive operative mortality. This view was challenged by Bolling in the mid-1990s, ushering in the era of both mitral valve repair and other surgical procedures for the failing heart.¹⁶ The traditional hypothesis held that the mitral valve functions as a “pop-off” mechanism for the failing ventricle and that surgical correction results in prohibitive mortality. The Bolling hypothesis is that there is an “annular solution for a ventricular problem . . . such that reconstruction of the mitral valve annulus’ geometric abnormality by an undersized ring restores valvular competency, alleviates excessive ventricular workload, improves ventricular geometry and improves ventricular function.”¹⁷ Miller and his Stanford colleagues reported that in an ischemic sheep model of MR, reduction of the annulus by a small ring reduces a radius of curvature of the left ventricle at the base equatorial and apical levels.¹⁸ This finding supports the concept that a small ring can restore a more elliptical ventricular shape. It is now recognized that the surgical mortality for mitral valve replacement observed in the past probably was the result of the loss of the subvalvular apparatus and not secondary to the loss of the pop-off valve as previously thought, underscoring the paramount importance of maintaining annular and subvalvular continuity during mitral valve surgery. Bolling was the first to show an acceptable operative mortality (5%) in a series of 140 NYHA class III and class IV patients with an LVEF of less than 25% and nonischemic cardiomyopathy. He demonstrated improvement in LVEF and a decrease in end-diastolic volumes during 3 to 5 years, as well as improvement in functional class.

A more comprehensive analysis of correction of MR in advanced heart failure patients with nonischemic LV dysfunction comes from Acker and colleagues in the Acorn trial.¹⁹ This trial evaluated the safety and efficacy of mitral valve surgery with and without the CorCap cardiac support device. The Acorn clinical trial, although not randomized to study the efficacy of mitral valve repair, did prospectively assess the safety and efficacy of mitral valve surgery in patients with advanced heart failure in multiple trial centers. Of 193 subjects entered, 73% were in class III. Most of the patients had idiopathic or valvular disease; only 6% had ischemic cardiomyopathy. The mean duration of heart failure approached 5 years; 97% of patients were taking angiotensin-converting enzyme inhibitors, and 80% were taking beta blockers. The mean LVEF was 23.9%, peak was 14 mL/kg/min, and LV end-diastolic dimension was nearly 70 mm. The operative mortality rate was only 1.6%—especially noteworthy because it represents the outcomes for nearly 30 different centers. Twelve-month cumulative survival was 86.5%; at 2 years, the cumulative survival was 85.2%. A majority of patients underwent a complete, small annuloplasty repair. Mitral valve insufficiency was reduced from 2.7 at baseline to 0.6 at 18 months, accompanied by evidence of reverse remodeling. A significant decrease in LV end-diastolic volume, LVESV, and LV mass was observed out to 5 years.²⁰ Finally, the baseline NYHA class of 2.8 was reduced significantly to 2.2 at 2 years. In summary, for patients with primarily nonischemic advanced heart failure and severe LV dysfunction, mitral valve surgery has been shown to be safe, with a low operative mortality rate, and associated with significant reversal of LV remodeling compared with baseline as well as improvement in NYHA functional class.

LV reverse remodeling also has been demonstrated in several studies as a result of mitral valve repair either alone or in combination with coronary artery revascularization for patients with ischemic disease. Braun and colleagues showed that the combination of mitral valve repair and CABG resulted in a significant decrease in LV end-diastolic volume up to 4 years after surgery.²¹ Fattouch and associates demonstrated, in a randomized study of CABG versus CABG and mitral valve repair, that the addition of mitral valve repair improves postoperative NYHA functional class and ventricular remodeling, decreases pulmonary arterial pressure, and leads to a decrease in hospitalization for heart failure.²² These same studies also showed low operative mortality rates for combined mitral valve surgery and coronary artery bypass procedures in patients with significant LV dysfunction and advanced heart failure symptoms.

In the STICH trial, the decision to treat the mitral valve during CABG was left to the surgeon.²³ Of 1212 patients who were randomly assigned, 435 (36%) had minimal MR, 554 (46%) had mild MR, 181 (15%) had moderate MR, and 39 (3%) had severe MR. In the medical arm, 70 deaths (32%) occurred in patients with minimal MR, 114 (44%) in those with mild MR, and 58 (50%) in those with moderate to severe MR. In patients with moderate to severe MR, there were 29 deaths (53%) among 55 patients randomly assigned to CABG who did not receive mitral surgery (HR versus medical therapy, 1.20 [95% CI, 0.77 to 1.87]) and 21 deaths (43%) among 49 patients who received mitral surgery (HR versus medical therapy, 0.62 [95% CI, 0.35 to 1.08). After adjustment for baseline prognostic variables, the hazard ratio for CABG with mitral surgery versus CABG alone was 0.41 95% CI, 0.22 to 0.77; P <.006), (Fig. 28-4). Although this was not a randomized trial between mitral valve surgery and CABG versus CABG alone, this retrospective analysis suggests a possible benefit to the concomitant surgical procedures.

In another study, 21 centers randomly assigned 75 patients to a CABG plus reduction mitral annuloplasty as a stratum in the control arm of the RESTOR-MV (Randomized Evaluation of a Surgical Treatment for Off-pump Repair of the Mitral Valve) trial, with a mean follow-up period of 24.6 months.²⁴ Entry criteria included need for revascularization, presence of severe or symptomatic moderate functional ischemic MR, an LVEF of 25% or greater, an LV end-diastolic dimension of 7.0 cm or less, and more than 30 days since acute myocardial infarction. The 30-day mortality was 4.1% (3/73, [two patients were not randomly assigned]). Average degree of MR was reduced from 2.6 ± 0.8 preoperatively to 0.3 ± 0.6 at 2 years. The rate for freedom from death or valve reoperation was 78% ± 5% at 2 years. Significant improvement in LVEF and NYHA class, with reduction of LV end-diastolic dimension, was observed. Cox regression analyses suggested that increasing age and renal disease were associated with decreased survival.

Mitral valve repair can be accomplished with an investigational procedure involving percutaneous implantation of a clip that grasps and approximates the edges of the mitral leaflets at the origin of the regurgitant jet.²⁵ Whether such less invasive procedures will change the management approach to patients with poor LV function and significant MR remains to be explored. A summary of recent guideline statements about surgery for MR in patients with heart failure is presented in Table 28-2.

Multiple studies suggest that the recurrent rates of MR after repair are approximately 30% to 40%. These studies generally fail to address ring selection and amount of downsizing as an important consideration for durable results in the ischemic MR population. Early failure with recurrent MR in patients with ischemic heart failure after CABG and annuloplasty ring probably was due to the use of a flexible band or ring. These results stand in sharp contrast with little recurrent MR seen up to 4 years later when a rigid ring has been downsized by two to four sizes. Spoor and colleagues found that the MR recurrence rate was 9.5% with a flexible ring versus 2.5% with a nonflexible ring in patients with a preoperative LVEF of less than 30% and no primary mitral disease.²⁶

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