Early outcomes of cardiac reoperations: seven years of experience

Kardiyak tekrar ameliyatlarında erken dönem sonuçları: Yedi yıllık deneyimimiz

Hayrettin Tekümit, Ali Rıza Cenal, Cenk Tataroğlu, Kemal Uzun, Esat Akıncı

Department of Cardiovascular Surgery, Özel Avrupa Şafak Hospital, İstanbul

Abstract

Background: The aim of this study was to present and discuss the early outcomes of our cardiac reoperation cases.

Methods: Between February 2001 and September 2008, 8645 patients underwent cardiac operations in our clinic. Medical records of 127 (1.46%) of them (76 females 51 males; mean age 51.2±13.6 years; range 11 to 75 years), who underwent cardiac reoperation, were retrospectively analyzed. The main reasons for redo cardiac surgery were progression of valvular diseases after repairs (n=43), occlusion of left internal thoracic artery or saphenous vein grafts (n=35). Preoperative clinical characteristics, perioperative data and early postoperative outcomes of the cases were presented.

Results: The interval between the first and redo cardiac operation was 7.5±8.0 (1-35) years. Four cases were operated under emergency conditions. Types of the reoperations were as follows: 35 isolated coronary artery bypass grafting surgery (27.5%), 70 isolated valve surgery (55.1%), 10 combined valvular plus coronary artery bypass grafting surgery and 12 other types of cardiac reoperation. In-hospital mortality rate was 5.5% (7 cases).

Conclusion: Reoperation itself is no longer a risk factor for poor outcome and we believe that cardiac reoperations may be done effectively and with acceptable risks when specific multidisciplinary approaches are adopted.

Abstract

Although recently the prevalence of redo coronary artery bypass grafting (CABG) reached a plateau,[1] the reoperation rate for CABG is still approximately 3% at five years, over 11% at 10 years, and 17% at 12 years after the initial operation. Other reports give the reoperation rates between 3% and 8.65%.[2] On the other hand, the number of patients undergoing reoperation for valvular heart disease is increasing and it will continue to increase as the general population ages.[3]

Cardiac surgery requiring a re-sternotomy (the socalled “redo” surgery) is technically difficult and carries a higher operative risk than the initial intervention. The particular problems are well recognized and include a difficulty to access the heart (due to adhesions, fibrosis or calcification around the operative site) making the dissection and suture placement difficult, which in turn results in prolonged durations of operation and increased postoperative mortality and morbidity rates.[4] Thus, cardiac reoperations are specific procedures requiring additional experience both in terms of operative decision making and surgery.

The aim of this study was to present our experience on cardiac reoperations and their early outcomes.

Methods

Study population
Between February 2001 and September 2008, 8645 patients had cardiac operations in our cardiovascular surgery clinic. A total of 127 (1.46%) patients (76 females, 51 males; mean age 51.2±13.6 years; range 11 to 75 years), who underwent cardiac reoperations were included in the present study. Hospital records of these redo patients were retrospectively analyzed. Demographical and clinical characteristics of these patients are shown in Table 1. The mean time between the initial operation and the reoperation was 7.5±8.0 years (range 1-35 years). The main reasons for redo cardiac surgery were the progression of valvular diseases after repairment (n=43), prior left internal thoracic artery or saphenous vein graft occlusion (n=35), prosthetic valve dysfunction (n=18), new onset coronary and native valve disease (n=12), presence of paravalvular leakage on implanted mechanical prosthetic valves (n=7), and other cases of failure and/or complications that developed after the first cardiac surgery (n=12). Procedures performed at the first cardiac operation are shown in Table 2.

Table 1: Demographical and preoperative clinical characteristics of redo patients (n=127)

Table 2: Procedures performed during the first operation (n= 127)

Surgical technique
In all cases, initially the right common femoral artery and the right common femoral vein were prepared to provide a route for a possible emergency cardiopulmonary bypass. Before sawing the sternum, the epigastric fascia was opened and the inferior heart was dissected away from the chest wall. The sternal wires were cut anteriorly and bent back, but they were not removed in order to protect the underlying structures. An oscillating saw is used to divide the sternum. Once the posterior table of the sternum was divided with the saw, the wires were removed and a sharp dissection was done with scissors to separate each side of the sternum from the underlying structures. The dissection plane was close to the sternum and developed along the diaphragmatic surface, then up around the right atrium towards the aorta. Dissection on the aorta was performed slowly and diligently to avoid penetration and extension beneath the adventitia. Dissection of the left heart was completed on cardiopulmonary bypass (CPB). The heart was not dissected more than necessary to perform the planned operation safely. The patent left internal thoracic artery (LITA) was isolated and controlled either before or after the initiation of CPB. The cardiopulmonary bypass was initiated and mild systemic hypothermia (30-32 °C) was achieved. Antegrade blood cardioplegia in induction and continuous retrograde blood cardioplegia in maintenance were used for myocardial protection.

Methods

Results

Except for four emergency reoperations, all reoperations were performed under elective conditions. Duration of the cross-clamp ranged between 14 minutes and 193 minutes (mean 76.9±35.4 min.). Durations of intensive care unit (ICU) stay and duration of hospitalization ranged between 0 to 48 days and 2 to 46 days, respectively. Prolonged intubation rates and prolonged ICU stay were 20.2% and 19.4%, respectively. Data regarding the operations are presented in Table 3.

Table 3: Operative and early postoperative data for reoperations (n= 127)

The distribution of the types of the reoperations was as follows: 35 cases had isolated CABG (27.5%), 70 cases had isolated valve surgery (55.1%), 10 cases had combined valvular plus coronary surgery and 12 cases had other types of cardiac reoperation. All cases undergoing CABG had full revascularization and 44 out of 45 of them required re-revascularization of the left anterior descending artery (LAD). The mean number of distal anastomoses per patient was 1.97±1.1 (range 1-4). Off- pump redo CABG surgery was performed on 22 of the patients. The most common isolated or combined valvular intervention was mitral valve replacement (n=60), followed by aortic valve replacement (n=23), tricuspid valve reconstruction (n=11), paravalvular leak repair (n=7), tricuspid valve replacement (n=2), aortic valve repair (n=1), open mitral commissurotomy (n=1) and mitral ring annuloplasty (n=1). Surgical procedures performed in redo cardiac surgery processes are shown in Table 3.

A total of seven patients died within 30 days after operation (5.5%): two following isolated CABG reoperations, two combined coronary plus valvular reoperations and three following isolated valvular reoperations. A total of 114 patients (89.7%) were event-free during the operation and in the early postoperative period. Three patients developed major hemorrhages during the re-sternotomy procedure, but all survived. Postoperatively, one patient required permanent pacemaker implantation (at day 23) and two patients developed non-microbial sternal dehiscence (at day 15 and 24, respectively).

Table 4: Procedures performed during the redo operation (n=127)

Results

Discussion

Cardiac reoperations represent one of the main challenges of cardiac surgery. Although recently the prevalence of redo CABGs reached a plateau,[1] the reoperation rate for CABG is approximately 3% at five years, over 11% at 10 years, and 17% at 12 years after the initial operation. Other reports give reoperation rates between 3% and 8.65%.[2] On the other hand, the number of patients undergoing reoperation for valvular heart disease is increasing and will continue to increase as the general population ages.[3]

Since February 2001, a total of 8645 open heart surgery operations were done in our clinic, among which 127 (1.46%) were reoperations. In our study, 70 cases were operated for an isolated valvular disease (55.1%). The numbers of patients operated for isolated coronary disease and combined valvular plus coronary disease were 35 (27.5%) and 10 (7.8%), respectively. This high number of valvular reoperations may be attributed to the relatively higher incidence of the rheumatic valvular heart disease in our population.

The main factor making cardiac operations different and unique is the need for a sternotomy. Cardiac surgery requiring a re-sternotomy (the so-called “redo” surgery) is technically difficult and carries a higher operative risk than the initial operation.[4] The pericardium is usually not closed after a heart surgery, and injuries to the grafts, the right atrium and ventricle, pulmonary artery, aorta and the innominate vein may occur.[5] Patients with valvular heart disease may be particularly prone to these complications, because atrial dilatation can result in significant cardiomegaly, atrial thinning and adherence of the heart to the posterior sternum. The incidence of hemorrhage following a re-sternotomy is between 2% and 6%.[6-8]

Ellman et al.[9] reported the results of 612 re-sternotomy cases in which 56 (9.1%) had an injury during the re-sternotomy and the initial dissection. Injury to grafts was the most common (46.4%) event, with mammary arteries comprising 21% and the vein grafts comprising 25% of the total. The right ventricle was the second most commonly injured structure (21.4%). Injuries occurring during the reoperation have caused mortality rates as high as 37%, and the mortality rates of those with an injury to a patent internal thoracic artery (ITA) was between 9% and 50%.[10]

In three (2.3%) of our cases, hemorrhage occurred following the re-sternotomy: in one case, the hemorrhage originated from the right ventricle; in another, from the ascending aorta; and in the last case, from an accidentally injured LITA graft. None of our cases died due to this re-sternotomy bleeding, which may be attributed to the precautious preparation of right (rarely left) common femoral artery and common femoral vein at the beginning of the operation, so that an emergency cardiopulmonary bypass could be started without delay.

Consideration should be given to the fact that the adhesions become less inflammatory and less vascularized over time: therefore, the longer the interval between the operations is, the better the results are. Reoperation following a period between three weeks and six months after the last operation is the most difficult choice.[10] In our study, the mean time from the first operation to the reoperation was 7.5±8.0 years (range 1-35 years).

The redo coronary bypass surgery is known to be a high-risk surgery. Early mortality of redo CABG ranges between 1.8% and 16.7%. The ten-year survival and angina-free survival rates after redo-CABG have been reported as 66.5% and 30%, respectively.[1] In the present study, the overall mortality rate was 5.5% (7 patients). Of these, two underwent isolated redo CABGs, two underwent redo combined valvular plus coronary operations, and three underwent isolated redo valvular surgeries.

The cause of perioperative death was cardiovascular in 85% of cases in the most recent cohort of patients undergoing reoperation. Furthermore, in the reoperation series, in-hospital mortality was associated with new perioperative myocardial infarction in 67% of the cases.[11] On the other hand, the early mortality rate of the patients undergoing off-pump surgery was lower than the rate of those undergoing conventional reoperations (3.3% vs. 5.5%).[12]

In our study, there were no postoperative myocardial infarctions among isolated CABG reoperation cases which may be attributed to the following factors: (i) 22 out of the 35 isolated CABG operations were done on the beating heart (62.8%); (ii) number of distal anastomoses per patient was low (1.97±1.1); (iii) the LITA anastomosis was injured during cardiac exploration in only one case; and (iv) continuous retrograde blood cardioplegia was routinely used in all redo CABG cases operated under CPB.

In patients with coronary reoperations, hospital mortality is reported to be influenced by the presence of a peripheral vascular disease, myocardial infarction between the initial operation and the redo operation, occluded ITA grafts, operative status (emergency vs. elective), CPB time longer than 120 min., antegrade delivery of cardioplegia, development of perioperative myocardial infarction,[13] diabetes mellitus and chronic obstructive pulmonary disease,[14] as well as low ejection fraction, age, female gender, a history of arrhythmia,[10] mammary artery grafting at the initial operation,[15] and renal insufficiency.[16]

In case of valvular reoperations, significant predictors of mortality were the time since the initial operation, age, indication, concomitant coronary artery bypass grafting and the replacement with a mechanical valve rather than a tissue valve.[17] Impaired functional capacity, low ejection fraction, emergent or urgent presentation, impaired renal function and involvement of the tricuspid valve were also reported as predictors of mortality after redo valve surgery.[18] Overall mortality for those patients undergoing the first heart valve reoperation was approximately 8.6%.[17]

The majority of deaths in the recent study series are due to cardiac causes, especially myocardial failure, which reflects the severely compromised hemodynamic conditions of the patients undergoing heart valve reoperations.[18]

Most of our cases consisted of valvular reoperations (70 cases, 55.1%). Our mortality rate following isolated valvular operations was observed as 4.2% (3 cases). One of these cases has had a mitral valve replacement (MVR) performed at the initial cardiac operation and was reoperated for mechanical valve dysfunction associated with a cardiogenic shock. In the second case, a dysfunction of both the aortic and mitral biological prosthetic valves was present. In the third case, the mechanical aortic and mitral prosthetic valves were again replaced by mechanical valves. The high number of valvular reoperation cases in our study can be explained by the following factors: (i) the prevalance of rheumatismal heart diseases is still high in our population and (ii) the initial intervention of most valvular reoperation cases was repair rather than replacement (68.5%).

Emergency redo surgeries may be required in patients with conditions such as endocarditis, unstable angina pectoris and acute aortic dissection. The mortality rate of those series is 43%, with half of the deaths occurring during the operation. The most important cause of morbidity in survivors is stroke (9%). The above-mentioned conditions may be associated with a mortality rate that may approach 100% without surgical intervention.[9] In our study, we had four cases of emergency reoperations (3.1%): two of them was in cardiogenic shock due to mechanical mitral valve dysfunction, one of them had an acute Stanford type A aortic dissection eight months after the CABG, and acute mitral insufficiency due to chordae rupture was present in the last patient who had undergone a four-vessel CABG two years ago. None of these patients died. These cases were directly transported from echocardiography or catheterization laboratory to the operating theatre. All cases had been intubated before being admitted to the operating room.

The prevalence of the coronary artery disease is gradually increasing and the rheumatismal valve disease will continue to be a health problem for the next few decades in the developing countries. In addition to this, the initial cardiac operations have begun to be performed at an earlier age, and the life expectancy is increasing due to this. All of these factors will contribute to a higher frequency of redo operations in the future. However, the reoperation itself is no longer a risk factor for a poor outcome[19] and we believe that cardiac reoperations may be done effectively and with acceptable risks when specific multidisciplinary approaches are adopted.

Discussion