Eur J Cardiothorac Surg 1998;14:54-58
© 1998 Elsevier Science NL
Ventricular remodelling and revascularization in severe left ventricular dysfunction1
V.L. Pathi,
T.M. Pillay,
K. Lall,
R. Williams,
W. Martin,
S.K. Naik
Department of Cardiac Surgery, Royal Infirmary, Alexandra Parade, Glasgow, Scotland, UK
Received 27 October 1997;
received in revised form 30 March 1998;
accepted 7 April 1998.
Corresponding author. Tel.: +44 141 2114300; fax: +44 141 5520987.
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Abstract
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Objective: To evaluate the role of surgical revascularization in the presence of severe, global impairment of left ventricular function without discrete aneurysm formation or mitral regurgitation. The high mortality and morbidity associated with this group, together with the limited benefits tend to prompt referral for cardiac transplantation. Methods: Fifty-three patients initially referred for transplantation, in addition to coronary revascularization, underwent mitral annuloplasty (group A=23), free wall remodelling by endoaneurysmorrhaphy (group B=17) or mitral annuloplasty and free wall reconstruction (group C=13). The mean ages were 59, 56 and 57 years for groups A, B and C, respectively. Detailed assessment of pre- and post-operative physical and psychological status were carried out. Results: Follow-up was for a mean period of 22–26 months. All patients reported substantial improvement in quality of life, both physical and psychological parameters and in NYHA functional class status. Objective evidence of improvement in ejection fraction was seen in all three groups but especially in group A. There were five early deaths, four were due to inadequate revascularization due to the poor quality of target vessels. There were three late deaths and one patient that required transplantation. Conclusion: We conclude that patients with severe left ventricular dysfunction can be candidates for surgical revascularization and optimization of ventricular geometry with acceptable mortality. The importance of achieving complete revascularization is emphasized in this series.
Key Words: Poor ventricular function • Mitral valve repair • Ventriculoplasty
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Introduction
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Ischaemic heart disease is the commonest cause of death in the western world today. Apart from the mortality, considerable morbidity is also associated with this condition. Patients suffering multiple myocardial infarcts develop ischaemic cardiomyopathy, with severe limitation of their quality of life. Despite adequate medical therapy, this condition has a dismal prognosis
[1].
Recent interest in this condition has centred on the quantitation of the proportion of reversible ischaemia as opposed to irreversibly damaged myocardium. Thus methods aimed at detecting hibernating myocardium which may revert to normal function following revascularization have aided patient selection for bypass surgery
[2]. There remain a large group of patients however, with grossly dilated, poorly contracting ventricles unsuitable for surgical treatment due to the associated prohibitive mortality. Although cardiac transplantation is the optimal treatment for these patients, the multi-organ dysfunction associated with a prolonged low output state limits its use in this population. Due to the scarcity of donor organs many patients accepted onto active transplant waiting lists die before a suitable organ becomes available
[3].
Compared to medical management, revascularization and repair of acute mechanical complications such as mitral regurgitation and free wall aneurysms have been associated with improved survival and symptomatic status
[4]
[5]
[6]. However, in patients with chronic ischaemic cardiomyopathy, despite successful isolated coronary artery bypass grafting, a large proportion continue to deteriorate
[7]
[8]. As a consequence long-term results of this form of surgery have been disappointing and physicians remain reluctant to refer such patients for surgery.
The role of mitral valve repair in the absence of gross regurgitation has been questioned due to its action as a release valve, reducing afterload and wall stress. However the consequences of this form of off-loading are severe pulmonary vascular congestion and right heart failure. Thus it is our contention that in these globally dilated ventricles, apart from continued ischaemia, the loss of the coordination of the free wall and mitral annulus greatly impedes efficient contractile function.
We present our evolution of thought over the past 5 years in the surgical management of patients with ischaemic heart disease and globally dilated ventricles. This subgroup of patients all had ejection fractions below 20% without discrete aneurysm formation or gross mitral regurgitation. Surgical techniques and medium term assessment of these patients are discussed.
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Methods
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Over the 3-year period 1993–1996, of the patients referred for cardiac transplant assessment, 58% were accepted on to the active list, 13% died during assessment and 29% were rejected. Patients in the latter group with end stage ischaemic heart disease with left ventricular ejection fractions below 20% as estimated by radio-nuclide scanning form the subject of this report. They are divided into three groups according to the echocardiographic assessment of the degree of dilatation of the ventricular free wall and or mitral annulus. This, together with operative inspection of the heart determined the extent of the procedures carried out. All patients had complete revascularization performed when possible using one internal mammary artery and venous grafts. In addition, group A (n=23) underwent mitral annuloplasty, group B (n=13) underwent free wall reconstruction and group C (n=17) underwent both procedures.
In the latter stages of the series pre-operative intra-aortic balloon pumping and intravenous parenteral nutrition were utilised
[9]
[10]. Operations were carried out under hypothermic cardiopulmonary bypass at 28°C. Aortic and two-stage atrio-caval venous cannulation with left ventricular venting through the right superior pulmonary vein were used in all cases. Myocardial protection was by antegrade and retrograde warm blood cardioplegic induction and reperfusion with intermittent cold crystalloid maintenance (St. Thomas' solution). Complete revascularization was carried out where possible first, followed by the mitral and free wall reconstructions. The internal mammary artery was harvested where haemodynamic stability allowed and long saphenous veins used for the rest of the grafts. Mitral annuloplasty was performed using Carpentier–Edwards rigid rings and in general sizes below 32 mm were used. Free wall reconstruction was performed using Dacron endoaneurysmorrhaphy techniques as described by Dor and colleagues
[11].
Pre- and post-operative assessment of the physical and psychological status of all patients was carried out by means of health profile questionnaires
[12]
[13]. A point was awarded for each symptom of greater than moderate intensity and the totals for each patient compared individually and as groups (Table 1). Patients were assessed before, 1 week and 6 monthly post-operatively. Hospital deaths are those occurring within 30 days of surgery or before hospital discharge.
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Statistical analysis
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Data are presented as mean±1 standard deviation. Paired Student's t-test was used for comparisons between pre- and post-operative scores in patients.
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Results
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Fifty-three patients were operated upon between 1993 and 1996. The pre-operative clinical status and demographic data are shown in Table 2.
There were five hospital deaths in the entire group, three being in group C (Table 3). Two patients during the early part of the study suffered cardiac arrests on induction of anaesthesia. One was impossible to separate from cardiopulmonary bypass, while the other died on day 3 post-operatively due to low output syndrome. Following the use of preoperative intra-aortic balloon pumping this complication did not recur. One patient in group A and one in group C suffered peri-operative myocardial infarctions as a result of poor quality distal vessels. One patient in group B died on day 1 from intractable arrhythmia after being weaned off the ventilator. Permission for autopsy was not granted. Two patients in group A died of progressive cardiac failure 9 and 12 months post-operatively and one patient in group C died suddenly at 15 months. The exact cause of death was not determined.
All surviving patients who were in NYHA functional class III-IV preoperatively showed marked improvement post-operatively as illustrated in Table 4. From groups A, B and C, respectively, 86.9%, 82.4% and 61.5% of patients showed downgrading of their NYHA functional classes.
Table 5 clearly illustrates that there was a significant increase in ejection fraction when compared with pre-operative values in all three groups. This was still significant in group C when only the survivors were included pre-operatively. None of the survivors showed a deterioration in exercise tolerance. The mean group scores for the health profiles are shown in Table 6.
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Discussion
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The high mortality among patients awaiting cardiac transplantation has led to reassessment of conventional operative techniques to palliate this subgroup. Our early experience has revealed that this can be achieved with acceptable mortality. The adoption of a holistic approach to this high risk group has included pre-operative stabilization with intravenous feeding and IABP support
[9]
[10]. This has eliminated the anaesthetic room cardiac arrests seen in the early part of the study which led to two of the deaths. Post-operatively all patients are recommenced on ACE inhibitors and anti-arrhythmic medication. Warfarin is used for the first 3 months following which aspirin is commenced.
The importance of revascularization in preventing early mortality has also been stressed during this period. The inability to adequately graft poor quality distal vessels led to a further two of the deaths and may be the major contraindication to this form of surgery. However the inability to predict the suitability for grafting by angiographic study was made abundantly clear in many of these patients. The occurrence of arrhythmias led to the death of two patients, though acute graft closure as a precipitating event cannot be excluded. Although electrophysiological study was not carried out the contrast with preoperative incidence is remarkable. This may be due to the reduction of wall stress and oxygen consumption leading to an attenuated arrhythmogenic substrate
[14]. However, all patients on pre-operative anti-arrhythmic medication had these continued long-term.
Recent interest in the operative management of end stage cardiomyopathy has been fueled by the successes of the reduction ventriculectomy of Batista
[15]
[16]
[17]
[18]. The majority of these procedures have been carried out for idiopathic dilated cardiomyopathy and little experience has been reported on the end stage ischaemic ventricle. Though laboratory models have been difficult to assess, the predominant effect of reduction ventriculoplasty is thought to be the reduction of ventricular wall shear stress and oxygen consumption as a consequence
[19]. This, acting through Laplace's law is thought to prevent the progressive dilatation seen at this stage of the natural history of this condition. The endoventricular patch plasty adopted by Dor and colleagues has proven to be extremely effective in the treatment of discrete ventricular aneurysms
[11]. Recent successful extension of this procedure to large akinetic scars is in agreement with our results in globally dilated ventricles
[4]. The advantages conferred by excision of myocardium in the ventriculectomy procedure may be due to reduced oxygen consumption by the ineffective myocardium. However, the ability of the ventricular septum to maintain adequate contractile performance following excision of a large segment of free wall may be greatly compromised in patients with previous infarctions.
With modern imaging techniques it is possible to predict the critical mass of hibernating myocardium which will allow revascularization alone to succeed
[2]. The pathophysiology of the globally dilated hearts in this report is no longer limited to ischaemia. Due to the dilatation of the cavity, left ventricular wall stress increases and despite successful revascularization ventricular contractile efficiency may remain compromised, explaining the continued deterioration in these patients
[7]. Similarly, even in the absence of gross mitral regurgitation, the annular dilatation may further reduce pumping efficiency due to intermittent mitral regurgitation. Though the ventriculoplasty procedures primarily remodel the free wall of the ventricle, the mitral valve has been replaced only if damaged during myocardial resection. It has therefore been impossible to gauge the contribution of associated procedures on the coronary arteries or valves to the clinical improvement in these reports
[20]. Our finding of significantly improved NYHA and well being profiles in all three groups would support evaluation of the two components of the ventricle as one unit. It may be that the two late deaths in group A were due to the failure to address the free wall dilatation at the time of operation. Indeed, the dramatic clinical improvement in patients in group C who had the worst ventricular function would attest to the adoption of a more aggressive `triple therapy' approach. With improved pre-operative management and changes in myocardial preservation recent results have been encouraging in this group.
The reluctance to adopt an aggressive approach towards the mitral apparatus in ischaemic cardiomyopathy has been based on the high mortality in previous reports
[21]. Emphasis has been placed on the additional mortality accrued by mitral valve repairs in ischaemic patients with mild to moderate regurgitation. This, together with documented improvement in mitral regurgitation by coronary revascularization alone, has led to a trend away from combined procedures unless severe regurgitation exists
[22]
[23]. Furthermore, studies in animals with normal hearts have stressed the deleterious effects of rigid prostheses in the normal flexible mitral annulus
[24]. The relevance of these findings in the grossly dilated over-flexible mitral annulus of the end stage ventricle with grossly distorted ventriculoannular geometry remains controversial
[25]
[26].
The concept of mitral annular and subvalvar integrity in the preservation of left ventricular function has been widely adopted by valve surgeons
[27]. The failure to differentiate ischaemic papillary muscle dysfunction, which would recover following revascularization, from annular dilatation has clouded the issue of intermittent mitral regurgitation in ischaemic patients. The pathological nature of annular dilatation in the absence of valvular regurgitation also remains speculative but may play a part in continued cardiac dysfunction following revascularization. In this context it was noted that the mitral annulus was much larger than the largest size available despite the absence of overt regurgitation, suggesting that intermittent regurgitation may occur during exercise or stress. The loss of sphincteric contraction of the annulus in these globally dilated hearts during systole may compromise the interaction with the free wall muscle
[28]. Under these circumstances the insertion of a rigid annuloplasty ring may paradoxically improve contractile function. Future studies in these patients using dynamic magnetic resonance imaging or stress echocardiography may clarify this.
Our concept was of complete revascularization, to address the ischaemia and ventricular reduction of both the free wall and the mitral annulus to improve contractile efficiency. The requirement for these supplementary procedures was determined by the degree, reversibility and site of hypokinesia on echocardiographic study. Furthermore, operative inspection of the ventricle allowed decision making regarding the need for free wall or mitral reconstruction. It can be anticipated that following this form of volume reduction surgery the pressure-volume relationships may shift to a more efficient part of the curve, however future studies utilizing impedance catheters would be required to clarify this.
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Footnotes
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Presented at the 11th Annual Meeting of the European Association for Cardio-thoracic Surgery, Copenhagen, Denmark, September 28 – October 1, 1997. 
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Abstract
Introduction
