Beating heart myocardial revascularization on extracorporeal circulation in patients with end-stage coronary artery disease

Cardiovascular Surgery, Vol. 9, No. 6, pp. 608–614, 2001  2001 Published by Elsevier Science Ltd on behalf of The International Society for Cardiovascular Surgery 0967-2109/01 $20.00

PII: S0967-2109(01)00092-8

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Beating heart myocardial revascularization on extracorporeal circulation in patients with endstage coronary artery disease Edvin Prifti*†, Massimo Bonacchi*, Giacomo Frati‡, Gabriele Giunti¶, Piero Proietti‡, Marzia Leacche¶, Massimo Massetti§, Gerard Babatasi§ and Guido Sani* *Divisione di Cardiochirurgia, Policlinico di Careggi, Firenze, Italy, †I.R.C.C.S NEUROMED, Via Atinense N.18, 86077 Isernia, Pozzilli, Italy, ‡Istituto di Chirurgia Toracica, Cardiovascolare e Tecnologie Biomediche, Universita` degli Studi di Siena, Siena, Italy, §Department of Cardiothoracic Surgery, Caen, France and ¶Divisione di Cardiochirurgia, Ospedale Maggiore della Carita Novara, Italy Objectives: To evaluate in a cohort of ESCAD patients (pts) the effects of on-pump/beatingheart versus conventional CABG in terms of early and mid-term survival and morbidity and LV function improvement. Methods: Between January 1993 and December 2000, 78 (Group I) ESCAD pts underwent on-pump/beating-heart surgery. Mean age in Group I was 66.2±6 (58–79), NYHA and CCS class were 3.2±0.6 and 3.3±0.4 respectively, Myocardial viability index 0.69±0.1 (%), LVEF (%) 24.8±4, LVEDP (mmHg) 28.1±5.8 and LVEDD(mm) 69.5±6. Group II consisted in 78 ESCAD patients undergoing conventional CABG selected in a randomized fashion from an age, sex, and LVEF corrected group of patients. Mean age in Group II was 65.7±5 (57–78), NYHA 3.1±0.7, CCS 3.4±0.8, LVEF(%) 25±5, LVEDP(mmHg) 27.9±4.4 and LVEDD(mm) 69.2±7.2. Results: Postoperatively, 5(7.7%) patients died in Group I versus 7(11.5%) patients in Group II (P>0.1). CPB time resulted to be in Group II patients (P = 0.001) and the mean distal anastomoses per patient was similar between groups (P = Ns). Perioperative AMI (P = 0.039), LCOS (P = 0.002), necessity for ultrafiltration (P = 0.018) and bleeding>1000 ml (P = 0.029) were significantly higher in Group II. None of the Group I patients underwent surgical revision for bleeding versus 8(10.3%) patients in Group II (P = 0.011). At 6 months after surgery, the LV function improved significantly in Group I patients, demonstrated by an increased LVEF = 27.2±4(%)(P = 0.001), lower LVEDP = 26.4±3(mmHg)(P = 0.029) and LVEDD = 67±4 (mm) (P = 0.004) instead of a lower LVEDD = 66.8±6(mm)(P = 0.032) versus the preoperative data in Group II. The actuarial survival at 1, 3 and 5 yr were 90, 82 and 71% in Group I and 89, 83 and 74% in Group II (P = Ns).

Correspondence to: Massimo Bonacchi, MD, Divisione di Cardiochirurgia, Policlinico Careggi, Viale Morgagni, 85, 50134-Careggi, Firenze, Italy. Fax: +39 0573 985427; e-mail: [email protected]

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Conclusion: In ESCAD patients who may poorly tolerate cardioplegic arrest, onpump/beating-heart CABG may be an acceptable alternative associated with lower postoperative mortality and morbidity. Such a technique offers a better myocardial and renal protection associated with lower postoperative complications due to intraoperative hypoperfusion.  2001 Published by Elsevier Science Ltd on behalf of The International Society for Cardiovascular Surgery Keywords: end-stage coronary artery disease, on-pump/beating-heart, coronary artery bypass grafting

Introduction The effects of coronary artery bypass grafting (CABG) on left ventricular function, in patients with end-stage coronary artery disease (ESCAD), remains a subject of active investigation. ESCAD patients with extensive areas of hibernating myocardium can be expected to derive the greatest benefits from CABG in terms of left ventricular (LV) function improvement [1]. Different randomized trials demonstrated an important survival benefit in patients with severe LV dysfunction (LVEF 具30%) undergoing CABG [2–7]. The invasiveness of CABG is determined by: (1) the site and type of operation, for which, MINICABG has been subject of investigation at our institutions, with emphasis usually to put on the switch from conventional median sternotomy to minithoracotomy [8], (2) myocardial ischemia, during the aortic cross-clamping period and the inflammatory response to cardiopulmonary bypass (CPB). An option is to use CPB, but to eliminate the ischemic component by avoiding the aortic crossclamping and keeping the heart beating throughout the operation. Small series have been reported in the literature demonstrating the role of this technique in relation to postoperative myocardial adaptation to stress [9] but there is no data on the postoperative outcome in ESCAD patients undergoing such a technique versus conventional surgery. The aims of this study were to evaluate in a cohort of ESCAD patients the effects of on-pump/beating-heart versus conventional surgery in terms of early and mid-term survival and morbidity and the improvement of LV function.

Patients and methods From January 1993 to December 2000, 78 (Group I) coronary artery disease patients with low LVEF (range, 17–30%) underwent on-pump/beating-heart CABG. Seventy-eight ESCAD patients (Group II) undergoing conventional CABG were selected from our general patients’ database in a randomized fashion from an age, sex and LVEF corrected group of patients operated during the same period. Patients with LV aneurysm, post-infarctual ventricular septal CARDIOVASCULAR SURGERY

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defect, severe mitral valve regurgitation, combined surgical procedures were not included in the study. LVEF was documented preoperatively by echocardiography and radionuclide Tc99 ventriculography examinations. The most important criteria for CABG were myocardial reversible ischemia documented by myocardial tomographic rest distribution Tl201 scintigraphy, hybernating myocardium diagnosed by echo stress dobutamine [10] and bypassable vessels. The viability score per patient was calculated for each resting Tl201 scintigram, then were summed and divided by 30 to yield a myocardial viability index (MVI) [11]. Patient population The mean age in Group I was 66.2±6 (58–79 yr). There were 50 men and 28 women, NYHA class 3.2±0.6 and MVI of 0.69±0.1. The transthoracic echocardiography revealed: LVEF (%) 24.8±0.4, LVEDP (mmHg) 28.1±5.8 and LVEDD (mm) 69.5±6. The mean age in Group II was 65.7±5 (57– 78 yr). There were 48 men and 30 females, NYHA class 3.1±0.7 and MVI of 0.68±0.08. The transthoracic echocardiography revealed: LVEF (%) 25±5, LVEDP (mmHg) 27.9±4.4 and LVEDD (mm) 69.2±7.2 (Table 1). Anaesthesia It consisted in propofol (3 mg/kg/h) combined with remifentanyl (0.5 to 1 g/kg/min). Neuromuscular blockade was achieved by 0.1–0.15 mg/kg pancuronium bromide or vecuronium. In Group I, metaraminol or phentolamine were used to maintain the systemic pressure between 50 and 60 mmHg and if necessary, esmolol hydrochloride (11 mg/kg) was used to slow the heart rate. Surgical technique CPB was instituted using ascending aortic cannulation and a two-stage venous cannulation in the right atrium. In both groups, heparin was given at a dose of 300 IU/kg to achieve a target ACT of 典450 s. A standard circuit was used, including a bard tubing set, which included a 40-m filter, a roller pump 609

Beating heart myocardial revascularization: E. Prifti et al. Table 1

Preoperative data of ESCAD patients undergoing CABG

Variables

Group I (n = 78)

Group II (n = 78)

Sex (M/F) Age(mean) Hypertension Diabetes Hypercholesterolemia Creatinine level >1.6 mg/dl History of peptic ulcer Cerebrovascular disease Peripheric vascular disease Arrhythmias NYHA class Canadian cardiovascular class >1 episode of myocardial infarction Preoperative PTCA Preoperative IABP Preoperative ischemia Stable angina Unstable angina Silent ischemia Triple vessel disease Left main trunk stenosis >50% Left ventricular ejection fraction (%) Left ventricular end-diastolic pressure (mmHg) Left ventricular end-diastolic diameter (mm) Myocardial viability index

50/28 66.2±6 44 (56.4%) 26 (33.3%) 12 (15.4%) 36 (46%) 10 (12.8%) 20 (25.7%) 11 (14%) 15 (19.2%) 3.2±0.6 3.3±0.4 44 (56.4%) 42 (54%) 12 (15.4%)

48/30 65.7±5 40 (51.3%) 30 (38.5%) 15 (19.2%) 40 (51.3%) 12 (15.4%) 21 (27%) 12 (15.4%) 12 (15.4%) 3.1±0.7 3.4±0.8 41 (52.5%) 40 (51.3%) 15 (19.2%)

0.87 0.57 0.63 0.62 0.67 0.63 0.82 1.0 1.0 0.67 0.34 0.33 0.75 0.87 0.67

17 (21.8%) 47 (60%) 14 (18%) 71 (91%) 23 (29.5%) 24.8±4 28.1±5.8

15 (19.2%) 52 (66.7%) 11 (14%) 75 (96%) 20 (25.6%) 25±5 27.9±4.4

0.84 0.51 0.66 0.33 0.72 0.68 0.81

69.5±6

69.2±7

0.78

0.69±0.1

0.68±0.08

0.5

and a hollow fibre membrane oxygenator. The extracorporeal circuit was primed with 1000 ml of Hartmann’s solution, 500 ml of gelofusine, 0.5 g/kg of mannitol, 7 ml of 10% calcium gluconate, and 60 mg of heparin. Nonpulsatile flow was employed. Intermittent antegrade and retrograde cold blood cardioplegia and moderate hypothermia were applied in all Group II patients. The proximal anastomoses were performed during the same aortic cross clamping in Group II patients. Complete data concerning the extent of revascularization are summarized in Table 2. On-pump/beating-heart CABG procedure (Group I) The core temperature was allowed to drift, usually to 34°C. The target vessel was occluded proximally and distally using a 4-0 polytetrafluoroethylene suture passed twice beneath the artery and mattressed on a small piece of silicone tubing to prevent direct contact between the suture and the anterior coronary artery wall. The first saphenous vein graft was anastomosed distally to the target coronary vessel and then to the aorta with the aid of a side-biting clamp after careful digital palpation of the aorta and with the pump off. When a second venous conduit had to be placed, its proximal end was sutured first to the aorta during the same period of partial occlusion, both to avoid repeated applications of the side-biting clamp and to allow immediate myocardial 610

P

Table 2 Operative data Variables

Group I

Group II

P

Cardiopulmonary bypass time (min) Aortic cross-clamping time (min) Number of distal anastomoses Left anterior descending artery Diagonal branches Circumflex artery Right coronary artery Sequential anastomosis/double graft Left internal mammary artery Postoperative surgical procedures Surgical revision Surgical revision for haemorrhage Cholecystectomy Intestinal resection

84±13

107±18

0.001

84±23 3.3±0.9 78 18 78 71 13

3.32±0.7 78 12 78 75 16

0.88 1.0 0.31 1.0 0.33 0.68

71

66

0.33

1 0

4 8

0.36 0.011

1 0

3 3

0.6 0.24

revascularization on completion of the corresponding distal anastomosis. Left internal mammary artery to the left anterior descending artery anastomosis was constructed last when the saphenous vein grafts were already functional. In 14 (18%) patients, after the performance of the anastomoses to the left anterior decsending and right coronary arteries without CPB (off-pump), the CPB was instituted and in CARDIOVASCULAR SURGERY

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on-pump/beating-heart, the anastomosis to obtuse marginal artery was performed. Postoperative data Perioperative myocardial infarction, low cardiac output incidence, inotropes’ use (excluding Dopamine ⱕ6 γ/kg/min), intensive care unit stay, complications and early death were determined (Table 3). All survived patients underwent postoperative echocardiography examination within 6 months after the surgical procedure. Follow-up The mean follow-up time was 42 months (range 3– 96 months). Survival status was determined by contacting all patients or next by telephone. Definitions Hospital mortality was defined as death for any reason occurring within 30 days after operation. Perioperative myocardial infarction was defined as the appearance of new Q-waves or significant loss of Rwave forces peak creatine phosphokinase MB fractions greater than 10% of total CK. Low cardiac output syndrome was defined as a cardiac index ⬍2.0 l/min/m2, requiring pharmacological support and/or IABP insertion. Postoperative renal dysfunction was defined as an increment of creatinine level ⱖ1 mg/dl compared to the preoperative value. Neurological complications were defined as any transient or permanent neurological deficit that developed following surgery. Gastrointestinal complications included confirmed diagnosis of upper and lower gastrointestinal haemorrhage, intestinal ischemia, acute cholecystis and pancreatitis.

Table 3

Postoperative survival and morbidity

Variables

Group I (n = 78)

Group II (n = 78)

P

Perioperative myocardial infarction CPK–MB% Low cardiac output IABP insertion Pulmonary complications Neurological complications Postoperative renal dysfunction Postoperative ultrafiltration Infectious complications Surgical revision for bleeding Postoperative bleeding >1000 ml Gastrointestinal complications Multi organ failure Death

1 (1.3%)

8 (1.3%)

0.039

7.8±3 15 (19.2%) 14 (18%) 3 (4%) 3 (4%) 28 (36%) 7 (9%) 3 (4%) 0 7 (9%)

9.6±4.2 30 (38.5%) 22 (28%) 5 (6.4%) 3 (4%) 45 (58%) 19 (24%) 5 (6.4%) 8 (10.3%) 18 (23%)

0.002 0.013 0.83 0.72 1.0 0.01 0.018 0.72 0.011 0.029

2 (2.5%) 0 6 (7.7%)

5 (6.4%) 2 (2.5%) 9 (11.5%)

0.44 0.48 0.59

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Statistical analysis Group statistics were expressed as mean±SD. Mann–Whitney test was used for continuous variables. Fisher exact test was used for the nonparametric variables. Wilcoxon’s signed rank test was used for comparing the variables within the same group (as appropriate). Survival was calculated using the Kaplan–Meier method. Significance between data was considered achieved when P⬍0.05.

Results The preoperative data analysis (Table 1) between Group I and II demonstrated similar comorbid features and left ventricular function between groups. The mean overall number of distal anastomosis was 3.3±0.9 versus 3.32±0.7 in Group I and II respectively (P = Ns). The CPB time was significantly lower in Group I patients, 84±13 versus 107±18 min in Group II patients (P = 0.001). The incidence of surgical revision for bleeding was significantly higher in Group II patients (P = 0.011). There was no difference in the number of bypassed vessels, type of arterial conduits and sites of surgical anastomosis between groups (Table 2). The postoperative survival and complications between Group I and II were analysed (Table 3). The hospital mortality in Group I was 6 (7.7%) patients versus 9 (11.5%) patients in Group II (P = Ns). Ten patients (four of Group I) died of progressive cardiac failure unresponsive to inotropic and/or IABP support, two died of multi organ failure, two (one of Group I) of sepsis, and one (Group I) deaths due to cerebral ischemia. The incidence of perioperative myocardial infarction (P = 0.039), creatine phosphokinase MB fraction (%) (P = 0.002), postoperative low cardiac output (P = 0.013), postoperative bleeding >1000 ml (P = 0.029) were significantly lower in Group I versus Group II. The increment of postoperative creatinine level ⱖ1 mg/dl compared to the preoperative value resulted to be higher in Group II patients (P = 0.01). From them 7 (9%) patients in Group I and 19 (24%) patients in Group II necessitated postoperative ultrafiltration (P = 0.018). The echocardiographic examination within 6 months after CABG revealed a significant improvement of left ventricular function in Group I which was demonstrated by a significantly higher LVEF (%) 27.2±4 (P = 0.001), and lower LVEDP (mmHg) 26.4±3 (P = 0.029) and LVEDD (mm) 67±4 (P = 0.004) compared with preoperative data. In Group II only LVEDD (mm) 66.8±6 improved significantly (P = 0.032) (Table 4). The mean follow-up time of the 141 survivors was 42±7 months. The actuarial survival at 1, 3 and 5 yr including all deaths in Group I was 90, 82 and 71% versus 89, 83 and 73% in Group II (P = Ns) (Figure 611

Beating heart myocardial revascularization: E. Prifti et al. Table 4

Improvement of left ventricular function within 6 months after CABG in survivors of both groupsa

Variables

Preoperative (Group I)

Postoperative (Group I)

LVEF LVEDP LVEDD

24.8±0.4 28.1±5.8 69.5±6

27.2±4 26.4±3 67±4

P

0.001 0.029 0.004

Preoperative (Group II)

Postoperative (Group II)

25±5 27.9±4.4 69.2±7

26.6±7 27±7 66.8±6

P

0.125 0.367 0.032

a

CABG — coronary artery bypass; LVEF — left ventricular ejection fraction; LVEDP — left ventricular end-diastolic pressure; LVEDD — left ventricular end-diastolic diameter

1). At mean 26±7 months after the CABG procedure, 7 (9%) patients in Group I and 8 (10.3%) in Group II underwent reoperation (P = Ns). The procedures of reoperations were: cardiac transplantation in seven patients, mitral valve replacement or repair in concomitance to CABG in three patients, CABG in four patients and replacement of the ascending aorta in one patient.

Discussion The goals of myocardial revascularization are to preserve the remaining myocardial function, improving symptoms in the majority of patients, even in the absence of a significant improvement in objective measurements of cardiac output such as LVEF [2– 7]. One of the main problems in ESCAD patients undergoing CABG is the myocardial protection. Despite the new myocardial protection techniques, postoperative adverse events related to intraoperative ischemia have not been completely eliminated. Even continuous warm blood cardioplegia, which keep the heart in an aerobic environment, does not completely prevent postoperative stunning [12], possibly because the myocardial edema intrinsic to the dias-

Figure 1 Overall acturial survival in Group I and II

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tolic state of the arrested heart can cause cardiac dysfunction [13]. It has been demonstrated that keeping the heart beating, even with reduced contractility, is associated with less myocardial edema and better function [13]. The detrimental effects of aortic cross-clamping are inconsequential in the vast majority of patients undergoing cardiac surgery but may easiely precipitate hemodynamic failure in ESCAD patients. Theoretically, the ideal solution to this problem is myocardial revascularization without extracorporeal circulation, the so called off-pump CABG. Different series of patients undergoing off-pump surgery demonstrated satisfactory clinical outcomes [14–17]. Limited revascularization in off-pump provides longterm results comparable to full revascularization with CPB, but at the cost of a threefold increase in reinterventions [18]. The on-pump/beating-heart surgery offers an optimal exposure of coronary arteries, and has a preventive role (transitional step) as in the case when cardiac arrest or severe hemodynamic alterations occur during operation, CPB and cardioplegic arrest can be perfomed easier versus off-pump surgery. We performed a similar number of distal anastomoses in both groups. In some cases, on-pump/beating-heart technique can be used for revascularizing only the posterior vessels in patients whose more accessible coronary arteries are grafted concomitantly without CPB. We applied this combined technique in 11 patients undergoing on-pump/beating-heart CABG with excellent results reducing the CPB time. Postoperatively we found significantly less bleeding (具1000 ml) and surgical revision for bleeding in patients undergoing on-pump/beating-heart surgery and this was attributed to longer CPB time in patients undergoing conventional CABG. Low LVEF is one of the most important factors for increased morbidity and mortality after CABG [19]. The on-pump/beating-heart CABG might constitute an alternative surgical approach, in highest risk ESCAD patients, an interesting trade-off, as suggested by the results reported by Sweeney and Frazier [20] with the use of biventricular assist devices during surgical procedure in a similar patient population. Other reports demonstrated a lower CARDIOVASCULAR SURGERY

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release of troponin Ic [9], a highly cardiac specific marker of tissue damage, and a threefold increase in the postoperative myocardial content of mRNA coding for HSP 70 [21–23], reflecting the preserved ability of the beating heart to display an appropriate adaptive response to surgical stress, whereas the arrested heart seems to have lost this capacity, as demonstrated by the fact that levels of HSP 70 mRNA at the end of cross-clamping were unchanged from baseline. The present report demonstrates that maintenance of the heart in a beating state caused less damage than aortic cross-clamping and was associated with better postoperative outcome. The operative mortality was lower in this pool of patients versus the conventional CABG, even not significant. The incidence of perioperative myocardial infarction and postoperative low cardiac output were significantly higher in patients undergoing conventional surgery. These data demonstrates that on-pump/beatingheart surgery offered a better myocardial protection compared to conventional CABG, confirming the effectiveness of the beating heart technique in ensuring adequate prevention against myocardial injury. Other authors [24–26] demonstrated that beating heart CABG offers a lower risk of systemic hypoperfusion during surgery and as a consequence a superior renal protection, demonstrated by a low incidence of postoperative renal complications. The cause of renal dysfunction after cardiac operation is multifactorial and usually is attributed to different factors, as the CPB, non-pulsatile flows, perioperative cardiovascular compromise, or toxic insults [24, 28–29]. Free plasma haemoglobin, elastase and endothelin, and free radicals including superoxide, hydrogen peroxide, and the hydroxyl radicals can be generated during CPB and can induce injury in the renal brush-border membrane [24]. The renal dysfunction was identified in both groups postoperatively, demonstrated by the increment of postoperative creatinine level ⱖ1 mg/dl versus the preoperative value, which resulted to be significantly higher in patients undergoing conventional CABG as well as the necessity of postoperative ultrafiltration. It seems that on-pump/beating-heart CABG causes significantly less renal dysfunction probably due to less systemic hypoperfusion, normothemia, and higher blood pressure. This was demonstrated even by the postoperative functional alteration of other parenchymas (all three patients identified postoperatively with multi organ failure syndrome underwent conventional CABG). The postoperative LVEF, LVEDP and LVEED improved significantly within 6 months after surgery in patients undergoing on-pump/beating-heart CABG instead of the improvement of the LVEDD only in patients undergoing conventional CABG (Table 4). Dreyfus et al. [7] reported significant CARDIOVASCULAR SURGERY

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LVEF improvement in selected patients with demonstrated viable myocardium. The discrepancy found in our study has a number of possible explanations: (1) Changes in LVEF may not reflect the postoperative improvement in coronary flow reserve in areas of viable myocardium with no resting ischemia; (2) The improvement of LVEF depends on factors including the presence and extent of stunned and hibernating myocardium, the surgeon’s ability to perform a complete revascularization of hibernating tissue, perioperative myocardial infarction, and the presence of paradoxical motion in the interventricular septum after CPB [27]. Indeed, the on-pump/beating-heart surgery offering a better myocardial protection, lower risk of perioperative myocardial infarction, which means: reduced risk of further loss of viable myocardium, lower intraoperative myocardial edema and stunned myocardium, increase the chances of early improvement of depressed LV function. We may conclude that in ESCAD patients, who may poorly tolerate the cardioplegic arrest and in situations where off-pump surgery may increase the operative risks, the on-pump/beating-heart surgery may be an acceptable alternative associated with lower postoperative mortality and morbidity.

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