ABSTRACT :
BACKGROUND : Ventricular septal rupture(VSR) is rare but one of the most serious and life threatening complication of acute myocardial infarction. Incidence of post infarction VSR is 0.2-0.34% .The aim of the study was to evaluate the Anesthetic management and early and long term outcome and prognostic factors of surgical repair of post infarction VSR by infarct exclusion technique.

METHODS : A total of 14 consecutive patients(mean age, 60) underwent surgical repair of VSR in our department in MMHRC from year 2006 to 2013. A retrospective analysis of clinical and operative data , predictors of early mortality and long term survival was performed. Post MI Ventricular septal defect was closed with Single pericardial patch (7 patients), Dacron patch (2 patients) and Double pericardial patch (5 patients) respectively.

RESULTS : The hospital mortality was 42% (6 patients). The most common cause of in- hospital mortality was persistent low cardiac output. One year mortality was 12% (1 patient). Among those discharged, there were 3 patients in this cohort study who survived beyond 5 years. Seven patients presented with cardiogenic shock and five out of these cohort died, four out of these five patients were operated within 4 days of myocardial infarction. Four patients had residual shunt post VSR repair. One patient needed Re-do VSR repair for significant residual shunt who succumbed later.

CONCLUSION : The repair of post infarction VSR by infarct exclusion with double pericardial patch technique is safe and feasible .This technique seems to offer sufficient favourable early and long term results. Preoperative cardiogenic shock carries a poor prognosis for this patients group. Early intervention, preoperative intra aortic balloon pump support may improve the surgical results.

INTRODUCTION :

Ventricular septal rupture (VSR) is a rare but feared complication of after acute myocardial infarction (MI).The incidence is low, approximately 0.2-0.34% of all patient with MI develop post infarction VSR .Mortality after surgical repair of VSR varies between 19-50% whereas mortality with medical treatment is extremely high, over 90% observed in first 3 weeks after VSR occurring due to complication such as heart failure , cardiogenic shock ,or both[1]. Hence, patient should be considered for urgent or emergent surgical repair, although the ideal time to operate on patient with VSR is after the replacement of necrotic muscle by fibrous tissue.

PATIENTS AND METHODS :

From year 2006 to 2013 , a total 14 consecutive patient underwent post infarction VSR repair in Cardio Thoracic Surgery Department in MMHRC .Data collection was performed retrospectively and focussed on intra operative, postoperative data, use of intra aortic balloon pump (IABP), and perioperative complications. Data also were obtained for 30 day mortality, in hospital mortality and long term outcome.
Preoperatively , Echocardiography and angiography were performed in all patients . The mean left ventricular ejection fraction (LVEF) was 35.84% .Eight patients (57%) were operated on within 4 days after the septal rupture. and another 6 patients (43%) were operated on between 4 and 12 days after the septal rupture. The operation was performed emergently in mean 3.1 (range 3-12) days after admission to our department. The mean interval from infarct to operation was 5.5 days. There were 10 men (71%) and 4 women (29%), mean age was 60 years ( range 45-70). All patients had antero-apical VSR and infarct related artery was Left anterior descending (LAD) in all patients.

Coronary angiography showed triple vessel disease in 3 patients (22%), double-vessel disease in7 patients (50%), and single-vessel disease in 4 patients(28% [LAD was totally occluded in 12patients(85%) and Right coronary artery(RCA) (30%),left circumflex artery (LCX)(35%),left main coronary artery(LMCA)(7%),Obtused marginal artery( OM)(7%),Posterior descending artery (PDA)(7%),Ramus Intermedius(RI) (7%), and Diagonal branch (7%) were partially occluded].
At the time of admission, 7 patients (50%) were in cardiogenic shock with low cardiac output .Eleven patients ( 78%) had presented with chest pain, and five patients(35%) with pulmonary edema. An IABP was inserted in 12 patients (85%) before operation for mean interval of 56 hrs (range 24 - 144 hrs). Inotropes were started at mean interval of 30 hrs before the operation. Table 1 & 2 contains patients demographics and preoperative risk profile of 14 patients.
The operations were performed by a single surgeon .A repair by the endocardial patch technique with infarct exclusion as originally described by Dr Tirone E.David and associates was performed in all patients.
The basic steps were as follows: Incision through the infarcted portion of left ventricle to approach the inter ventricular septum ;Identification of the VSD and the margins of the infarcted muscle; Exclusion of infarct and VSD by single autologous pericardial patch (50%),double autologous pericardial patch (35%),Dacron patch(15%) was performed. which was sutured to the non infarcted endocardium of the inter ventricular septum and to the non infarcted ventricular wall; and finally, closure of the Left ventriculotomy incision by direct suture buttressed on teflon felt strips in all patients.
Myocardial revascularisation was performed in nine patients (64%) at the time of surgical repair of VSR. Saphenous vein was used for coronary artery bypass grafting in all patients. Single vein grafting (3 patients) and, double vein grafting (6 patients) was performed at the time of VSR repair. Five patients did not receive any graft because of severe diffusely diseased vessels.

Two patients required linear LV aneurysmorrhaphy for severely akinetic and dilated anterior wall segment. No other associated procedures were performed. The cold blood cardioplegia was given to seven patients (50%), the mean cardio pulmonary bypass time was 123 mins (range 79-172 mins), The mean Aortic cross clamp time 65.57 min .The other seven patients were operated on fibrillatory perfused heart

BMI : Body Mass Index
Renal dysfunction is defined as urine production less than 500 ml per day or creatine greater than 1.5 mg/dl

ASMI - anterio-septal myocardial infarction ; AWMI : anterior wall myocardial infarction; PTCA : percutaneous transluminal coronary angioplasty;
SVD - single vessel disease, DVD - double vessel disease, TVD - tripple vessel disease,
LAD- left anterior descending artery, LCX- left circumflex artery, RCA - right coronary artery,
PDA- posterior descending artery, LMCA - left main coronary artery, OM - obtused marginal artery, RI - ramus intermedius.
The follow-up period ranged between 8 months and 7 years (mean follow-up time, 3.5 years).

RESULTS : The in- hospital mortality was 42% (6 patients).Five patients among them died of severe low cardiac output .One patient had anterior free wall rupture with gross hemopericardium (500ml ) post op he developed severe low cardiac output and died. Another patient had significant residual shunt on fifth day after operation, underwent Re do closure of VSR (patch dehiscence) , died on 12th post op day because of renal failure and required peritoneal dialysis. One year mortality was 12%(1 patient) who had presented with congestive heart failure symptoms and echocardiography showed small residual shunt and was managed conservatively, after a month patient had acute AWMI and cardiac arrest and died.

The hospital mortality rate in patients who presented with cardiogenic shock and pulmonary edema was 71 % and 20%respectively; Renal failure occurred in 7 patients (50%) with need for continuous renal reperfusion therapy (CRRT) in 2 patients. The mean interval of inotropic support and post op ventilatory support was 30 hrs, 48 hrs respectively. Five patients (35%) needed prolonged inotropic support (need for inotropic agents longer than 3 days) because of low cardiac output, and Five patients required prolonged assisted ventilation .The mean blood loss during intra op and post op was 560ml & 500 ml respectively. Restoration of lost blood volume was achieved with infusion of mean volume of Packed Red cells, platelets and fresh frozen plasma 900ml, 288ml, 311ml respectively.

The mean intensive care unit stay for survivors was 7.7 days .The mean hospital stay for patients who needed inotropic support because of low cardiac output was 14.4 days, and for hemodynamically stable patients was 9.1 days .One patient had a neurogenic event (seizures) 5 days after the operation, was treated with antiepileptics
Four patients died who were operated within 4 days of occurrence of myocardial infarction .The post op mean left ventricular ejection fraction (LVEF) was 36.3 % (range 20 - 45).Patients in whom VSR repair done with Single autologous pericardial patch(7 patients), Dacron patch(2 patients),Double autologous pericardial patch(5 patients) had residual shunt 42%(3patients), 14% (1 patient) ,0% respectively .one patient with single pericardial patch needed Re-do VSR repair for significant residual shunt who succumbed to death later. The survival rate at 1 year in hospital survivors was 88%. Three patients survived beyond 5 years and on regular follow up (NYHA class I – II).

The following variables were tested for in-hospital mortality: Age older than 60 years, single or multiple-vessel disease, Cardiogenic shock, IABP support, Renal insufficiency, Pulmonary edema at the time of presentation, thrombolysis, interval of MI to surgery, concomitant coronary artery bypass graft. The influence of these variables on early mortality is illustrated in Table 4

CAD : coronary artery disease; SVD : single vessel disease ; MVD : multiple vessel disease;
CABG : coronary artery bypass graft; VSD : ventricular septal defect.

DISCUSSION :

After the first reported surgical repair of a post infarction VSD in 1957 by Cooley and colleagues, many surgeons attempted to develop new operative techniques to lower the high mortality rate that has been associated with this operative procedure.
In 1977, Daggett and coworkers reported lower perioperative mortality rates achieved by the use of prosthetic material to replace necrotic muscle and by a trans infarct incision regardless of infarct location. Since that time, other classic operative techniques, including infarctectomy and reconstruction of the ventricular septum and free wall of the heart with Dacron patches, have been performed,

David and colleague introduced [2,3] a new operative procedure in 1987, whereby both the left to right shunts can be eliminated, and the ventricular remodeling and aneurysm formation of the infarcted myocardium can be prevented. The prevention of additional damage of the already dysfunctional right ventricle and the restoration of the left ventricle geometry, by the above described method, may be the reason it leads to a lower operative mortality rate .
Because of impressive results of this technique, operative procedure has been applied in all 14 consecutive patients in our department who underwent repair of post infarction Ventricular Septal Rupture from year 2006 to 2013. In our series, mortality rate was 42% which is similar to mortality rates reported in previous studies.

Predictors of early mortality have been determined in our series. The influence of these variables on early mortality is illustrated in Table 3. As described by other groups, there is a high mortality rate for patients with preoperative cardiogenic shock, especially for those whose hemodynamic status is not improved by IABP support.
The basic goals of the less invasive IABP counterpulsation are to stabilize circulatory collapse, to increase coronary perfusion and myocardial oxygen supply, and to decrease left ventricular workload and myocardial oxygen demand. Counterpulsation has also been shown to be useful in achieving pulsatile cardiopulmonary bypass and in assisting high-risk patients through the operation. In our series, preoperative IABP support and absence of cardiogenic shock were associated with a significantly lower risk of hospital mortality.

we believe that patients with preoperative cardiogenic shock should be promptly treated with IABP,inotropic agents, and vasodilators before any diagnostic examination. Preoperative intra-aortic counter pulsation may increase cardiac output and improve coronary perfusion, and may lead to a decrease of the left to right shunt.
The incidence of residual VSD reported varies from as low as 4.7% to as high as 43% . Cox and colleagues described a residual VSD in 22.9% of the patients in their series; 60% of them have undergone reoperation because of clinically significant shunt. In our series, only 1 patient (7%) received a redo procedure because of clinically significant residual shunt. The low incidence of residual VSD in our series as well as in the series by David and associates may be explained by the application of the infarct exclusion technique with the suturing of the double pericardial patch to the healthy endocardial tissue surrounding the infarcted muscle of the ventricular septum and the ventricular wall.

Percutaneous closure of the smaller VSDs with catheter-based devices may now offer a different treatment option for critically ill patients who have a small post infarction ventricular septal rupture. However, the same raise concerns over the possibility of further increasing the size of the rupture and destroying the atrioventricular valves or the ventricles through the devices.

CONCLUSION : The repair of post infarction ventricular septal rupture by the infarct exclusion technique described by David and associates can be done safely .This technique seems to improve the results of surgery for patients who have posterior VSD and avoids the recurrence of the VSD after the first correction. From our data, it appears that preoperative cardiogenic shock carries a dismal prognosis. We support the strategy of preoperative IABP support as an important tool for the preoperative support of hemodynamically unstable patients with post infarction ventricular septal rupture.

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