Back to CARDIOLOGYThis is the second article of a series about current perspectives in Heart Failure ( HF ) treatment. Here we are going to review some outstanding new information about surgical treatment of HF, something that has currently revolutionized the approach to HF and that has received tremendous attention in the media. We will be talking about surgery for reversible causes of HF ( eg. coronary heart disease, valvular heart disease, ... ), cardiomioplasty and the highly controversial and recent partial ventriculectomy. In the next part of the series, heart transplantation will be discussed in detail.
Congestive heart failure continues to be in 1996 one of the leading causes of death and disability, despite the advances in pharmacological therapy ( specially with ACE inhibitors ) and understanding of its pathophysiology aquired in recent years ( for details see the first article of this series ). So, surgical procedures have been tried in an effort to increase survival and also the quality of life of HF patients, as well as to prevent irreversible ventricular dysfunction.
The first thing that the cardiologist caring for a patient with HF has to exclude is the reversibility of the ventricular dysfunction, so that a treatable etiology can be found and appropriate managment avoid irreversible failure. Coronary artery disease is currently the leading cause of HF in the western world, accounting for about 50% of heart transplantations performed wordwide. Unfortunantely, with the increasing size of waiting lists and lenghtening of waiting times, the mortality while waiting may considerably reduce the overall survival for patients assigned to this treatment mode. So, it is imperative that we recognize patients with " ischemic cardiomyopathy ", as we can by means of surgical revascularization, improve ventricular function, survival and quality of life.
It has become apparent that impaired left ventricular dysfunction in patients with coronary artery disease is not always an irreversible process, as it can improve markedly and even normalize in subsets of patients after successful revascularization. This is because between the extremes of the normal viable myocardium and scarred myocardium exist regions of viable but dysfunctional myocardium, either ' stunned ' or ' hibernating ' . Stunned myocardium displays decreased function despite restoration of normal blood flow following an interval of ischemia ( ie, flow-contraction mismatch ), the most common scenario for this phenomenon occuring after reperfusion following acute myocardial infarction. Hibernating myocardium harbors viable tissue that has been down-regulated by chronic ischemia so that myocardial energy demands do not outstrip energy supply. This represents an attempt by myocytes to balance oxygen supply and demand, thus preventing myocardial necrosis and ischemic symptoms at rest. Hence, these regions have perfusion that is sufficient to maintain myocardial viability, but insufficient for normal myocardial function ( ie, flow-contraction match ). This kind of dysfunction is the most important to find in HF patients, as they can be revascularized. Recovery of normal myocyte contractile fuction in areas of hibernating myocardium can take several days, weeks or even months to occur after blood flow is restored. The exact molecular mechanisms underlying hibernation have yet to be elucidated, but may include impaired calcium handling by the sarcoplasmic reticulum and reduced sensitivity of myofibrils to calcium.
Myocardial dysfunction in Ischemic Cardiomyophathy depends on a complex interplay among regions of normal, scarred, stunned and hibernating myocardium. Distinguishing the relative contributions of each in individual cases can be challenging, but today it can be accurately done by imaging technics, such as positron emission tomography ( the gold standard, but not widely available), thallium imaging and dobutamine echocardiography. After confirming the presence of viable myocardium, we should proceed with cardiac catheterization to assess target vessel suitability for CABG. It should be stressed that this stategy is not without risks, as surgery in these patients with moderate-to-severe myocardial dysfunction has higher mortality rates than in good conditions, with some authors considering them prohibitive, thus prompting referral for cardiac transplantation.
Other potential surgically reversible causes of HF that shold be pursued include valvular heart disease ( as long as irreversible ventricular dysfunction has not take place, when valvular surgery no longer is beneficial and the only solution is heart transplantation ) and congenital defects (ventricular septal defect, atrial septal defect, ..., as long as irreversible pulmonary hypertension has not take place, when only heart-lung transplantation is an acceptable solution ). The detailed discussion of these diseases is beyond the scope of this article, and should be covered in the near future in the Cardiology section of Medstudents.
When no reversible cause for HF is found, there are two surgical technics that offer hope to help the failing dilated heart in keeping with its pump fuction, as pharmacological therapy has limited long term benefits and mechanical devices for ventricular assistance are only used as a bridge to keep the patient alive until he can undergo heart transplantation. The first one is the so called Cardiomyoplasty, in which a pediculated skeletal muscle ( latissimus dorsi ) is placed around the heart and stimulated in synchrony with it, aiming at helping or partially substituting myocardial contractility. It is necessary that the muscle used can be trasnposed to the mediastinum while preserving its vascular supply, that being a reason for using mainly the latissimus dorsi muscle in this operation. This procedure was first done clinically by Carpentier & Chachques in 1985.
The basis for this surgery is that skeletal muscle is capable of generating a higher energy in an isolated contraction than cardiac muscle. Also, contractions of high amplitude and with a duration similar to that of cardiac fibers can be obtained with eletrical stimuli at about 30 Hz of frequency. The acute utilization of skeletal muscle for ventricular assistance is limited, though, by muscular fatigue. Even though, after 6-8 weeks of prolongued stimulation, there is an adaptation process that makes the skeletal muscle resist its new function of repetitive sequence centractions as if it was a cardiac muscle. This is achieved by a combination of two factors : a decrease of energetic demand and an increased ability to generate energy by aerobic metabolism. The bioenergetics of muscular contractions turns into a more favorable one after modifications of calcium kinetics and of myosin contraction, which tranforms itself from type II ( rapid action ) to type I ( slow action ).
Cardiomyoplasty has been indicated for patients with idiophatic dilated cardiomyophathy or with cardiomyophathies secondary to coronary artery disease or Chagas's disease, aiming at increasing cardiac contractility. It has also been described in association with large ventricular aneurysm or left ventricular tumor ressections, in which it is necessary to use extracorporeal circulation. While still considered an experimental procedure, it is indicated for patients with a high one-year mortality ( class III or IV NYHA, ejection fraction < 25%, cardiac index < 2.5, pulmonary capillar pressure > 18 ), similar to that for cardiac trasplantation. Despite being indicated for patients with severe ventricular dysfunction, as it requires an adaptation period of about 2-3 months and it only assists myocardial function, it depends on existence of a residual myocardial contractile function, being contraindicated in patients dependent on intravenous inotropic agents and at high risk of needing ventricular assistance devices after surgery. So, NYHA class IV patiens should be managed pharmacologically aiming at turning them into class III. Other contraindications for the procedure include a high grade of cardiomegaly ( as it precludes the wrapping of the heart with the skeletal muscle ), high grade mitral insufficiency, cardiac arrhytmias refractory to clinical managment, severely compromised pulmonary function and degenerative muscular diseases.
Two weeks after surgery, eletrical stimulation of the graft is started. This interval between surgery and initiation of stimulation permits recuperation of adequate perfusion of the latissimus dorsi, which is interfered by interruption of the distal anastomoses between branches of the thoracodorsal artery with the peripherical circulation from intercostal and lumbar vessels. Also, this interval allows better coaptation between the muscle and the heart, turning the muscular contractions more effective in pump assistance. After that, a detailed protocol for electrical conditioning of the skeletal muscle is initiated with isolated pulses synchronized at every two heart beats. The electrical pulses are gradually increased every two weeks, and after two months the ideal frequency of 30 Hz is achieved. Chronically, the muscular contraction can be synchronized with every hert beat or every two beats. The adequate synchronization between muscular contraction and ventricular systole is an important factor for the success of the procedure, and is guided echocardiographically, with the muscular pacemaker being programed to sense and stimulate at the same time as mitral valve closure or aortic valve opening.
In a multicentric study done to evaluate its efficacy ( Medtronic study ), 304 patients were operated, 80% in NYHA class III and 20% in class IV, all with ejection fractions < 35%. It showed an improved in functional class in 83% of patients. 44% of those operated in class III went to class I, 39% to class II and only 15% stayed in class III. In the group operated in class IV, 3% returned to class I, 73% to class II, 15% to class III and 10 % had no improvement. Quality of life was significantly improved 6 moths after surgery. Hospital mortality was 14.8% for those operated in class III and 34.1% for those in class IV.
In a prospective trial done in the São Paulo Heart Institute ( Incor ), 36 patients ( most with dilated cardiomyopathy, 28 in class III and 8 in class IV ) were operated and compared with similar patients submited to pharmacological treatment. There was no hospital mortality, and survival at one year was 82.3%, 61.5% at two years and 38.8% at 3-5 years. Survival in operated patients was significantly superior to that observed in similar patients in pharmacological therapy ( 42% one year survival and 24% at two years ). Patients operated in class IV had a decreased survival when compared to those in class III, as in the Medtronic trial.
This last trial also examined the effects of cardiomyoplasty in hemodynamics. There was a significant increase in ejection fraction, of about 20-30%. Systolic left ventricular function have improved, as assessed by measures of chamber and pulmonary capillar pressures. This could be explained by the partial trasfer of myocardial work for the graft and by the decrease in wall tension and its subsequent decrease in myocardial oxygen consumption, partially correcting pathophysiological alterations responsible for the perpetuation of the progression of pump failure ( see first article of series ). Hemodynamic benefits persisted at 5 years of follow up, even though there was a tendency to a decrease of ejection fraction starting at two years after surgery, which attained pre-operative levels at 5 years.
In conclusion, cardiomyoplasty improve ventricular function and clinical signs of HF, having a possible effect of increasing long term survival. So it is an alternative to the treatment of severe HF in those patients with some preserved ventricular function and mild to moderate pulmonary hypertension. Meanwhile, new studies need to be done to compare it with clinical treatment until these patients have an indication for heart transplantation.
The last surgical approach that we are going to discuss is the recently described Partial Ventriculectomy - the Batista surgery - described by the brazilian Dr. Randas Batista in 1994. There was a tremendous attention form the media about this surgery and the reports by Dr. Batista are impressive, although not always reproduced by other groups.
The surgery inittialy consisted of a ressection of the lateral free wall of the left ventricle ( see figure 1 ) between the papillary muscles and preserving the mitral apparatus. Now it's done by a ressection that includes the pappilary muscles and the whole mitral apparatus, necessitating a mitral prothesis ( see figures 2 and 3 ). This last version in an enlargment of the original surgery. The rational basis for this ressection is that the normal heart has an ellipsoid morphology, with its longitudinal diameter much larger than the tranverse one. The contractile capacity of the ventricular chamber holds direct relation with the chamber's shortening fraction, which is inversely relatedl to the tranverse diameter. So, it is evident the harm caused by the increse in the tranverse diameter, as happend when the ventricle dilates, besides also increasing wall tension and oxygen consumption, as dictated by the Laplace law. Consequently, the ressection permits a better performance of the left ventricle, as it remodels the geometry of the left ventricle, turning its morphology again into an ellipsoid again.
In last September, Dr. Batista presented his results at the annual meeting of the Brazilian Society of Cardiology in Salvador, Brazil. He described 27 patients operated by the new technique ( involving the papillary muscles ) between Jan.95 and March 96 with idiophatic dilated cardiomyopathy in class IV and an ejection fraction of < 20%. He reported that the ejection fractions increased by 100-300%, not justifying the previous belief that the papillary muscles contribute importantly to contractile function in the dilated heart. 4 patients died and the main morbidity was blood dyscrasias. In the same meeting, he also presented the results of 236 patients operated by the original technique, all with dilated cardiomyopathy ( various etilogies ) and NHYA class IV transplant candidates, some already with contraindications for transplantation. Ejection fractions were between 8 and 23% and age varied from 8 months to 74 years old. The ejection fractions increased by 100-300%, with a mean time of permanence in the intensive care unit of 4.2 days and hospital discharge in about 9 days. The main morbidities were renal insufficiency and cardiac arrhytmias. There was a 5% intraoperative mortality, 15% in-hospital mortality and the survival ay 2 years was 62%, 52% of which in class I and 36% in class II. These are really outstanding results when compared with the 50-80% 1 year mortality this patients have when treated only phamacologically.
However, the results obtained by other brazilian expert surgeons are not so encouraging, even though there's no dought that ventricular function does really improve expetacularly, with some class IV patients returning to class I. The group from Incor in São Paulo, for instance, presented in the same meeting results of 21 operations, with a total in-hospital mortality of 34%. From those who survived, 33% suffered from life threatening ventricular arrhytmias, all originating in the ventricular scar as shown electrophysiologically, with some patients requiring implanted defibrillators. So, they wondered why Dr. Batista does not report such a high incidence of arrhytmias, as he only gives his patients 100 mg of Amiodarone a day. So, the Incor group considers this surgery still experimental until its drawbacks cam be resolved, but everyone agrees that it has a tremendous potential to revolutionize the natural history of Heart Failure.
In conclusion, the recently described surgical approaches to HF are offering hope to a group of patients that would otherwise die if they were not lucky enough to have a heart transplantation, wich is not also a perfect procedure, as we are going to see in the next article of this series. Meanwhile, we are waiting for new developments in the surgical strategies that can overcome their morbidities and mortality, which are still very high. The Batista surgery undoubtely is a revolution of concepts and its potentials are enormous, as long as its complications can be minimized and its long term safety shown. We are entering an exciting new era of better results in HF treatment, after many disappointments when we used to believe that inotropics were the solution for pump failure.
1) Chachques JC, Mitz V, Hero M et al - Experimental Cardioplasty Using Latissimus Dorsi Muscle
Flap; J Cardiovasc Surg 1985, 26 : 457-62
2) Chachques JC, Grandjean PA, Schwrtz K et al - Effect of Latissimus Dorsi Dynamic
Cardiomyoplasty on Ventricular Function; Circulation 1988, 78 ( Suppl III ) : 203-216
3) Carpentier A, Chachques JC & Grandjean PA - Cardiomyoplasty. Mount Kisco, New York.
Futura Publishing Co 1991 : 280
4) Jatene AD, Moreira LFP, Stolf NAG et al - Left Ventricular Function Changes After
Cardiomyoplasty in Patients with Dilated Cardiomyophathy. J Thorac Cardiovasc Surg 1991; 102 :
132-139
5) Moreira LFP, Stolf NAG, Bocchi EA et al - Clinical and Left ventricular Function Outcomes Up
to Five Years After Dynamic Cardiomyoplasty. J Thorac Cardiovasc ( in publishing )
6) Batista RJV, Santos JLV, Cunha MA et al - Ventriculectomia Parcial : Um Novo Conceito no
Tratamento Cirúrgico de Cardiomiopatias em Fase Final. Resumos do 22º Congresso Nacional de
Cirurgia Cardíaca, Brasília 1995 : 150
7) Nery P, Bocchino L, Batista RJV et al - Evolução Clínica dos Pacientes Submetidos a
Ventriculectomia Parcial. Arq Bras Cardiol Vol 67 ( Suppl I ), 1996 : 47
8) Batista RJV, Verde J, Carvalho R et al - A Ressecção dos Músculos Papilares Como Forma de
Melhorar a Função Ventricular. Arq Bras Card Vol 67 ( Suppl I ), 1996 : 47
9) DeNofrio D, Loh E - Myocardial Viability in Patients with Coronary Artery Disease and Left
Ventricular Dysfunction : Transplantation or Revascularization. Current Opinion in Cardiology 1996,
11 : 394-402
10) Arie B, Laks H - The Role of Coronary Revascularization in the Managment of Heart Failure :
Identification of Candidates and Review of Results. Current Opinion in Cardiology, 1996, 11 :
276-290
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