Eur J Cardiothorac Surg 2006;29:S266-S271
© 2006 Elsevier Science NL
End-stage cardiomyopathy and secondary mitral insufficiency surgical alternative with prosthesis implant and left ventricular restoration
Enio Buffolo
*
,
João Nelson R. Branco,
Roberto Catani, the RESTORE Group
Cardiovascular Surgery Department, Federal University of São Paulo, Paulista School of Medicine, Brazil
Received 2 February 2006;
received in revised form 23 February 2006;
accepted 1 March 2006.
* Corresponding author. Address: Rua Borges Lagoa, 1080 – 7°A, Cep. 04038-031, São Paulo, SP, Brazil. Tel.: +55 11 5574 6611; fax: +55 11 5574 6786. (Email: enio.buffolo{at}terra.com.br).
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Abstract
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Background: Secondary mitral insufficiency is a strong risk factor for death in end-stage cardiomyopathy. The possible correction of mitral regurgitation has now been accepted as an alternative to cardiac transplantation in a special subset of patients. We propose a new surgical approach that consists of implantation of a mitral prosthesis that is smaller than the annulus, and preservation and traction of the papillary muscles to reduce sphericity of the left ventricle. Methods: Between December 1995 and September 2005, 116 patients with dilated cardiomyopathy underwent this procedure, with the following etiologic factors: ischemic (68), idiopathic (43), Chagas disease (3), viral (1), and postpartum (1). The patients were analyzed according to clinical criteria, echocardiographic findings, and morphology of left ventricle. Results: All patients were in an end-stage phase, requiring >2 hospital admissions over the past 3 months, despite receiving full medication. Furthermore, seven were in intensive care unit receiving intravenous drugs or intra-aortic balloon counterpulsation, and one was in cardiogenic shock. Hospital mortality was 16.3% (19/116), yet midterm follow-up showed a relatively flat late survival curve, with evidence of improved clinical status, better echocardiographic parameters, and reduction in ventricular sphericity. Conclusions: The high early mortality rate related to other clinical conditions at the time of surgery. However, the resultant flat survival after this early interval offers a promising long-term therapeutic alternative for the treatment of patients in refractory heart failure with cardiomyopathy that is associated with moderate or severe secondary mitral regurgitation.
Key Words: Heart failure • End-stage cardiomyopathy • Mitral insufficiency • Left ventricular restoration
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1. Introduction
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Heart failure has a high incidence and prevalence. North American data reports the diagnosis of 400,000 new cases of heart failure annually. In spite of adequate drug management, the 5-year survival rate for these patients is only 50%. Furthermore, only 40% of patients in class functional IV (NYHA) have a 1-year survival rate. Heart transplantation is now considered the gold standard treatment for patients with congestive heart failure that is refractory to medical treatment. However, due to the small number of donors, indications for this procedure are limited. Furthermore, transplantation is not available in patients of elderly age, in the presence of associated disease, or with inadequate socio-economic environment [1–3].
Other surgical procedures have been suggested to benefit a large number of patients and these include cardiomyoplasty [4,5], partial left ventriculectomy (PLV) [6,7], mitral valve correction [8–10], biventricular pacing [11], and myocardial revascularization itself [12]. However, no consistently effective surgical alternative is available in this cohort of patients, who suffer a poor short-term outcome due to high mortality rates, from advanced dilated cardiomyopathy.
Mitral insufficiency has a dual impact on this population, since it causes severe hemodynamic changes in end-stage dilated cardiomyopathy, and is simultaneously associated with a shorter survival [13–15]. Mitral insufficiency is a secondary phenomenon, as the valve itself is not diseased. Its significance is emphasized by the acceptance of correction of mitral regurgitation with a method that reduces annular dimension as an alternative to cardiac transplantation in a special subset of patients [16]. This technical approach has special impact because routine mitral valve exposure involves a conventional procedure that is well recognized by the cardiac surgeon.
Mitral regurgitation appears late in advanced dilated cardiomyopathy, and is due to the interaction of the following factors: segmental alterations in contractility, papillary muscle dysfunction, dilatation of the mitral valve annulus, and particularly, geometric alteration of the ventricular cavity, which changes from an elliptical to a spherical shape [15,17]. The sphericity index quantifies this geometric form alteration by comparing the transverse ventricular (short) and long axis; an ellipse has a 0.5 ratio (the length is twice the width) and a sphere is 1.0 due to similar transverse and longitudinal dimensions.
The importance of simultaneous correction of mitral incompetence during partial left ventriculectomy is emphasized by our review of the significant functional improvement that follows coordinating these procedures, and similar observations were made by others [18]. Recognition of this potential benefit, coupled with understanding that mitral valve exposure involves a routine approach that is well recognized by all cardiac surgeons, led us to propose a new surgical approach. The components include implantation of a mitral prosthesis that is smaller than the annulus, combined with a method that restores the elliptical normal architecture of left ventricle from inside its cavity.
This goal is reached by shortening the longitudinal axis by bringing the stretched papillary muscles toward the annulus, a technique that reduces the sphericity of the left ventricle and creates an elliptical ventricular shape. This report will summarize our experience in 116 consecutive patients with end-stage cardiomyopathy and secondary mitral insufficiency treated by a novel method of mitral valve implantation.
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2. Materials and methods
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One hundred and sixteen patients with dilated cardiomyopathy with moderate or severe secondary mitral regurgitation underwent a new surgical procedure between December 1995 and September 2005. This cohort comprised 65 males (55%) with ages varying from 25 to 82 years (62 ± 12). Twenty-three patients (19.5%) were more than 70 years of age. Etiological factors include ischemia in 68 patients (59%) idiopathic in 43 (37%), Chagas disease in 3, viral in 1, and gestational in 1 patient.
Eighty-three percent (83%) of patients were in functional class IV and 17% in class III despite adequate medication, and each patient required >2 hospital admissions for advanced heart failure symptoms. Eleven of them were in the intensive care unit receiving inotropes or intra-aortic balloon counterpulsation, two required dialysis, and one was in cardiogenic shock. Twenty-one patients had undergone prior operations including myocardial revascularization, LV aneurysmectomy partial ventriculectomy, or resynchronization as either isolated or combined procedures.
Inclusion criteria were end-stage cardiac insufficiency, more than two admissions in the last 3 months and moderate/severe mitral insufficiency diagnosed by transesophageal echocardiography. Exclusion criteria included: organic mitral pathology, associated aortic valve disease, left ventricular aneurysm, or myocardial revascularization with hibernating myocardium. All operative procedures were carried out following IRB approval.
A standard surgical approach was followed including median sternotomy, cannulation of the aorta and both vena cava, and mitral valve exposure via either left longitudinal or transeptal exposure if left atrial size was small. Prosthesis implantation preserved valvular leaflets as well as the subvalvular apparatus. The anterior leaflet was sectioned in the middle as in the technique described by Miki et al. [19], and Teflon felt pledgets with sutures are placed along the free border of the leaflet cusp and then directed toward each commissure to exert traction on the tops of the papillary muscles as shown in Fig. 1
. In very large LV chambers, a pledgeted mattress suture is passed across the tip of the papillary muscle, and then inserted through the edge of incised anterior leaflet, and then into the annulus as demonstrated in (See Appendix A).
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Fig. 1. (a) Exposure of mitral valve and lines anterior leaflet incision. (b) Suture placement into the valve leaflets edges, with connection to commissures with pledgeted sutures.
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This traction maneuver shortens the longitudinal axis of the left ventricle by an amount that is equivalent to the distance between the free border of the cusp and its insertion in the atrio ventricular annulus. When this suture is secured, traction is made the base of the papillary muscles, so that the ovoid shape of the left ventricle becomes restored following suture coaptation to the annulus. The geometric effects of this intervention are shown in (See Appendix A), whereby as more elliptical chamber is rebuilt from the spherical shape that exists in dilated cardiomyopathy.
The overall surgical objective to this global spatial relationship also includes shrinking the upper ventricular circumference. Consequently, the base of the heart was thereby narrowed by implanting a small prosthesis that was usually two sizes smaller than the annulus. Biological prostheses were employed in 111/116 patients. Five mechanical valves were used. Annular sizes ranging from 25 to 33 mm including 25 (2), 27 (48), 29 (3), 31 (20), and 33 (3). Additionally, 65% (44/68) of ischemic patients underwent associated procedures including revascularization (19), exclusion fibrotic areas (20), or both (3), and resynchronization (2).
Postoperative hospital discharge follow-up examination evaluated functional classification, pharmacological management, serial echocardiographic evaluation, and morbidity and mortality. The mean follow-up period was 38 ± 16 months. Twelve patients underwent pre- and postoperative nuclear magnetic resonance (NMR) examination to evaluate the left ventricular sphericity index, obtained by comparison of the ratio of the transverse: longitudinal axis to generate a width/length relationship.
The Friedman test (multiple comparison tests) was used to compare distributions of pre- and postoperative results. The alpha error was established as p
0.01, and the Kaplan–Meier method was used to generate actuarial survival curves.
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3. Results
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Hospital mortality (30th day) was 16.3% (19/116), and the primary causes of death were low cardiac output (7), multiple organ failure (4), cerebrovascular accident (2), broncopneumonia (3), refractory arrythmias (1), sudden death (1), and mesenteric thrombosis (1).
Ninety-seven patients were discharged from hospital and had a follow-up varying from 1 to 118 months (mean 38 ± 16). The actuarial survival curve, including hospital mortality, is shown in Fig. 2
. The predominant mortality decline occurred in the immediate perioperative interval (first 2 months), as a relatively flat late trajectory was observed following hospital discharge indicating a relatively stable late course of the survivors.
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Fig. 2. Actuarial survival curve of all patients, showing the initial drop due to hospital mortality, followed by a relatively flat and stable curve.
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Substantial reduction in morbidity was also observed, since the postoperative functional class improved significantly. Whereas preoperative evaluation showed that 83% were in functional class IV and 17% in III, late postoperative evaluation demonstrated that 77% were in functional class II, 15% in III, and 8 in IV. Within this class IV group, two patients have undergone heart transplantation, and two others are on the transplant waiting list.
Functional evaluation was also made by transthoracic echocardiographic measurements, as ejection fraction, stroke volume and left ventricular volumes were measured preoperatively, before hospital discharge, and 6 months postoperatively, as displayed in Fig. 3a, b, and c. The early modest increase in ejection fraction persisted, stroke volume rose due to elimination of regurgitant fraction, and left ventricular volume modestly decreased.
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Fig. 3. (a) Pre- and postoperative functional class status. Note (1) 83% in class III preoperatively, (2) 77% in class II at 6-month postoperative follow-up. (b) Ejection fraction values in immediate preoperative (EFo), before hospital discharge (EF1) and at 6 months (EF2). Note progressive improvement. (c) Stroke volume by echocardiogram, confirming progressive improvement (1) before hospital discharge and (2) at last evaluation (>6 months).
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These functional changes were associated with a striking alteration in ventricular shape, as observed in Fig. 4
that compares pre- and postoperative echocardiographic analyses in the same patient. Quantification of how restoration affected ventricular sphericity was done in 11 consecutive patients; Fig. 5
shows how nuclear magnetic resonance analysis showed how restoration of ventricular shape during mitral implantation decreased sphericity index to thereby allow development of a more elliptical contour.
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Fig. 4. Echocardiogram taken before and after implantation of bioprosthesis and papillary muscle implantation. Note the change in shape from spherical chamber (left) to elliptical configuration (right) postoperatively.
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Fig. 5. Magnetic resonance values for pre- and postoperative sphericity index (relationship between transverse and longitudinal axis) in 11 patients. Note that postoperative indices become more elliptical, as the sphericity index reduces, indicating less sphericity (0.5 = ellipse, 1.0 = sphere).
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4. Discussion
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The connections of the papillary muscles to the mitral valve in the normal heart insures the natural elliptical shape, by anchoring the V-shaped chamber through their connections between the chords and the ventricular wall. Conversely, detachment of these connections during mitral valve replacement changes ventricular geometric shape towards a spherical configuration. The importance of maintaining this normal connection is clear, since techniques of valve replacement in nonfailing hearts are governed by routinely maintaining leaflet, chord, and papillary muscle connections to avoid iatrogenic disruption of ventricular geometric architecture.
Tethering of the valvular apparatus exists during dilation, with disruption of the coaptation capacity of the valve leaflets as a central anatomic feature the stretched ventricle that accompanies dilated cardiomyopathy [16]. Similar impairment of normal papillary muscle function feature exists whether the underlying disease is remote muscle stretch after a myocardial infarction or intrinsic myocyte damage from idiopathic or inflammatory cardiomyopathy. Both factors were present in the patient population reported, and this novel surgical approach of ventricular restoration via the papillary muscles was instituted because of (a) recognition of the importance of rebuilding this geometric configuration when dealing with valve implantation in dilated failing hearts, and (b) our prior knowledge of the functional benefits that result after adding correction of mitral incompetence during PLV in the treatment of nonischemic cardiomyopathy.
The principals of salvaging the leaflet and chordal apparatus were described in 1988 by Miki et al. [19], whereby he made the same V-shaped incision into the anterior leaflet as done in this study. However, the described approach differs since Miki only attached the leaflets and chords to the annulus, whereas the described method in this report sometimes, in very dilated hearts, places a mattress suture through the tip of the papillary muscle in this process. The overall result of withdrawal of the papillary muscle toward the annulus is shown in , whereby a more conical chamber is created as this suture was secured.
The principles of this procedure include (a) the commonality of conventional surgical knowledge about how to routinely approach the mitral valve, so that no new exposure method must be learned, and (b) showing how modification of an established method mitral valve implantation can be expanded to employ the traction concept, as the tips of the stretched papillary muscle head are withdrawn into the annulus during valve implantation. This modification of papillary muscle architecture now allows these natural structures to exert a restoration effect on the underlying ventricle by making its shape more elliptical.
The echocardiographic, MRI, and clinical data support the importance of restoring a more normal shape to these failing dilated hearts. Functional support of the improved shape was provided by echo data of a more elliptical contour, improved ejection fraction, reduced end-systolic volume index, and, most importantly, rendering 77% of patients into a NYHA class II category, when their preoperative classification included 83% in NYHA class IV and 17% in class III. Pre- and postoperative MRI testing evaluated the sphericity index and quantified a return to the more elliptical shape, the desired geometric configuration from this novel procedure that coordinates ventricular rebuilding with mitral valve implantation.
Two aspects of this 116-patient experience become clear by evaluation of the survival curves. First, there was a 16% hospital mortality, and the predominance of deaths occurred within the initial 2–3 month interval. This finding implies that three factors must be considered, including urgent introduction of this procedure in very high-risk patients, failure to address and exclude the nonfunctional area in 48/68 ischemic patients, as well as addressing a more detailed investigation of the methods of myocardial protection in these very advanced patients. For example, a similar adverse influence of urgent procedures was reported by Suma and co-workers [18,20] when a ventricular approach was applied to patient with nonischemic cardiomyopathy. Furthermore, we considered absence of scar as a contra indication to exclude nonfunctional muscle in ischemic dilated cardiomyopathy. However, trabecular scar may be present [21].
The second prognostic factor relates to the relatively flat trajectory of the survival curve following the early loss of high-risk patients. This observation implies that restoration of shape may introduce a geometric configuration that allows a good long-term future, since the expected downward survival trajectory would be otherwise expected if such elliptical form change did not alter the natural course of the disease process.
Mitral valve implantation for secondary mitral regurgitation in dilated ischemic cardiomyopathy has been a procedure with limited effect in dilated ischemic cardiomyopathy. However, prior approaches only addressed the valve [22,23]. The new method in this report uses the retained papillary muscles as an anchor to rebuild shape during valve replacement, and thereby introduces a ventricular aspect to this commonplace procedure. The preliminary data implies that this novel look into a valve/ventricular procedure for end-stage cardiomyopathy may merit further consideration in the future.
Furthermore, this current application of the traction effect of the papillary muscles may be further expanded to simultaneously narrow the widening that sometimes exists between the bases of the papillary muscles in the dilated chamber. The method of narrowing this width was recently described by Buckberg et al. [24], as shown in Fig. 6
and our subsequent studies shall test adding this narrowing feature to the method of traction described in this manuscript.
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Fig. 6. Upper images show widening of distance between bases of papillary muscles during dilation between (a) normal shape and (b) spherical ventricular form. Lower image shows method of narrowing this widening by (c) pledgeted placing mattress sutures into the base of muscle, ventricular wall, and other base and (d) restoration of more normal geometry by suture line imbrication.
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5. Conclusion
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Mitral valve prosthesis implantation and left ventricular restoration via the papillary muscles in end-stage cardiomyopathy with significant mitral regurgitation may offer an alternative to heart transplantation.
These early and late findings demonstrate better quality of life, improvement in several echocardiographic parameters of function, and reduction in sphericity of the left ventricle. The hospital mortality rate is increased in these high-risk patients, but the relatively flat trajectory of the late survival curve implies that improved prognosis may be expected in this cohort of patients with end-stage heart disease.
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Appendix A
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Supplementary data
Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ejcts.2006.03.004.
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Acknowledgments
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This work was funded by the Deutsche Forschungsgemeinschaft, grant no. 1208/6.
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Abstract
1. Introduction
