INTRODUCTION

Currently, there are high incidences and prevalences of Congestive Heart Failure (CHF) with approximately 23 millions of people suffering from this disease and 2 millions of new cases diagnosed each year worldwide [1,2].

The gold standard for these patients is heart transplantation, but due to the low number of donors and the rigorous criteria of indication, a large number of these patients die whilst waiting for the definitive treatment [3-5].

The long-term result in this group of patients is not satisfactory due to high rates of mortality. Thus, in an attempt to benefit a greater number of patients, a series of alternative surgical procedures have been proposed including cardiomyopathy, partial left ventriculectomy, surgical correction of mitral valve regurgitation, biventricular heart pacing and myocardial revascularization either as an isolated procedure or associated to ventricular repair [6-11].

Mitral valve regurgitation in patients with dilated cardiomyopathy is linked to a reduction in short-term survival rates [12]. Mitral valve regurgitation is associated to the interaction of several factors: segmental changes in ventricular contractility, papillary muscle dysfunction, dilatation of the mitral valvar annulus and in particular, geometrical changes of the ventricular cavity with loss of its elliptical form [13].

By analyzing patients who had been submitted to partial left ventriculectomy and publications on the subject, a functional improvement was identified mainly in patients with surgical correction of mitral valve regurgitation. Based on these data a surgical technique was proposed that involves the surgical correction of mitral valve regurgitation with the implantation of a prosthesis smaller than the valvar annulus associated with internal remodeling of the left ventricular cavity by shortening the longitudinal axis.

The goal of this work is to analyze the impact of this surgical technique on patients with advanced dilated cardiomyopathy and secondary mitral valve regurgitation, by means of clinical and echocardiographic data.

METHOD

Between December 1995 and September 2005, 116 patients with advanced dilated cardiomyopathy and moderate to severe mitral valve regurgitation were submitted to the surgical procedure discussed in this work. The group constituted of 65 (55.10%) male patients and ages ranged from 25 to 82 years (mean of 62 ± 12 years); 23 (19.50%) patients were over 70 years old.

In regards to the etiology of the cardiomyopathy, in 68 cases (58.60%) it was ischemic, 43 (37.10%) idiopathic, three (2.58%) chagasic, one (0.86%) viral and one (0.86%) gestational.

All the patients had been hospitalized at least twice within the previous three months for congestion in spite of adequate medication. According to the classification of the New York Heart Association (NYHA) 83% were in functional class (FC) IV and 17% in FC III in the immediate preoperative period. Eleven patients were in the intensive care unit on circulatory support taking vasoactive drugs and using an intra-aortic balloon pump; two patients were in dialytic program and one was in cardiogenic chock. Moreover, 21 patients had previously been submitted to heart surgery for coronary artery bypass grafting (CABG), left ventricular aneurysmectomy, partial left ventriculectomy and/or ventricular resynchronization, either in isolation or associated. The mean follow-up time after surgery was from 38 ± 16 months.

Inclusion criteria were: advanced CHF (with two or more periods in hospital within the previous three months due to the congestion) and moderate or severe mitral valve regurgitation as diagnosed by transesophageal echocardiogram. The exclusion criteria were organic diseases of the mitral valve, associated aortic valvuloplasty and ischemic disease with indication for CABG (with confirmed myocardial viability) and/or ventricular repair.

The study protocol was approved by the Ethics and Research Commission of the Paulista School of Medicine and the patients agreed to participate in the study by signing an informed consent form.

Surgical technique

The surgery was initiated with hemodynamical monitoring including measurement of the mean arterial pressure, central venous pressure and urinary excretion, as well as respiratory monitoring by pulse oximetry.

The surgery followed the normal manner; medium sternotomy was performed with cannulation of the aorta and the superior and inferior vena cavae through the right atrium after systemic heparinization (4 mg/kg) under moderate hypothermia of 32ºC.

Hypothermic anterograde sanguineous cardioplegia (at approximately 18ºC) was utilized as myocardial protection with added potassium (15mEq/L) during induction. For subsequent doses, at 15-minute intervals, blood at 32ºC was added to the perfusate without the addition of any other substances.

The mitral valve was approached by means of longitudinal left or transseptal atriotomy depending on the diameter of left atrium. The anterior leaflet was sectioned in half, according to the technique described by Miki et al. [14], creating two halves whose angles were sutured to the commissures. The aim of this was to shorten the longitudinal axis of the heart using the traction of the papillary muscles and consequently to restore the elliptical form of the left ventricle.

After this a prosthesis, smaller than the mitral valvar annulus, was implanted with preservation of the posterior leaflet. Of the total prostheses utilized, 111 were biological and five were mechanical, with diameters as follows: 25 (two cases), 27 (48), 29 (43), 31 (20) and 33 (three).

For patients with an ischemic etiology, 64.70% (44/68) were submitted to associated procedures: CABG (19), exclusion of fibrotic areas (20) or both (three) and ventricular resynchronization (two).

At the end of the surgery, the patients in normothermia were transferred to the recovery unit where they were continuously monitored.

All the patients were accompanied during the hospital and out-patient evolution by the same member of the surgical team, with the protocol completed to compare pre- and postoperative data.

Statistical analysis

Statistical analysis consisted in a comparison of parameters studied in the three observational periods of observation, when data were collected for all patients. The observations were recorded in the following periods:

1.Before surgery - immediate preoperative observation;

2. Before hospital discharge - postoperative observation;

3. After hospital discharge - last assessment.

The parameters evaluated were:

 Left ventricular ejection fraction (LVEF);

 Left ventricular ejection volume (LVEV);

 Ratio between the long and short axes of the left ventricle.

Friedman's test was utilized to analyze the results by comparing pre- and postoperative values. Statistical significance was established at a p-value = 0.05. Analysis of survival was obtained using the Kaplan-Meier's curve.

RESULTS

The hospital mortality rate was 16.30% (19/116) with the main causes of death being low cardiac output syndrome (seven), multiple organ failure (four), strokes (two), bronchopneumonia (three), refractory arrhythmia (one), sudden death (one) and mesenteric thrombosis (one).

Of the 116 patients included in this study, 97 were discharged from hospital and were accompanied in the outpatient clinic for a follow-up period of from 1 to 118 months (mean of 38 ± 16 months).

After hospital discharge, the actuarial survival curve remained stable with an acceptable long-term mortality rate (Figure 1).



There was a significant improvement in the functional class, where in the preoperative period 83% of patients had been in FC IV and 17% in FC III (at the time of surgery), in the last postoperative assessment (performed in all patients that were discharged from hospital) 77% were in FC II and 15% in FC I. Eight per cent of patients remained in FC IV, among whom two are on the transplantation list and another two have already been submitted to this procedure (Figure 2).



The left ventricular ejection fraction and the ejection volume were analyzed by transesophageal echocardiogram, with data obtained in the postoperative period (before hospital discharge) and during assessments as out-patients. There was a modest but significant increase in the ejection fraction between both observation periods. Additionally, there was a significant increase in the ejection volume seen between the observation periods (Figures 3 and 4).


Fig. 3 - Ejection fraction in the preoperative period, before hospital discharge and six months after surgery


Fig. 4 - Ejection volume in the preoperative period, before hospital discharge and six months after the surgery