HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Quoc-Bao Do Raymond Cartier Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Do, Q.-B. Articles by Cartier, R. Search for Related Content PubMed PubMed Citation Articles by Do, Q.-B. Articles by Cartier, R. Related Collections Coronary disease

Eur J Cardiothorac Surg 2002;21:385-390
© 2002 Elsevier Science NL

Hemodynamic changes during off-pump CABG surgery

^a Department of Surgery, Montreal Heart Institute, Montreal, Quebec, Canada
^b Department of Anesthesia, Montreal Heart Institute, Montreal, Quebec, Canada

Received 26 September 2001; received in revised form 6 December 2001; accepted 21 December 2001.

* Corresponding author. Research Center, Montreal Heart Institute, 5000 Belanger Street East, Montreal, Quebec, H1T 1C8, Canada. Tel.: +1-514-376-3330, ext. 3715; fax: +1-514-376-4766
e-mail: rc2910{at}aol.com

	Abstract

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion References

 
Objectives: The purpose of this study was to assess the patients' hemodynamics during off-pump coronary artery bypass graft (OPCABG) surgery. Methods: Continuous monitoring of the mean systemic arterial pressure (SAP), mean pulmonary arterial pressure (PAP), mixed venous oxygen saturation (SvO₂) and cardiac output index (COI) was done on 55 patients undergoing complete OPCAB revascularization. Hemodynamic changes were recorded at the completion of the anastomosis before releasing coronary snaring and stabilization and compared to baseline. Results: The mean age of the patients was 66.4±9.2 years, and on average 3.3±0.8 grafts per patient were performed. The average SAP drop after manipulations was -8.3±16.9 mmHg for the left anterior descending artery (LAD), -13.5±19.6 mmHg for the diagonal artery (DG), -14.6±13 mmHg for the optuse marginal artery (OM), and -14.2±13.5 mmHg for the right coronary artery. This was significant for all territories (P<0.01). The PAP significantly increased in all territories except OM (LAD: 3.7±6.3 mmHg, DG: 4.3±8.6 mmHg, OM: 1.1±7.2 mmHg, posterior descending artery: 2.7±5.6 mmHg; P<0.05). Variations in COI were significant in all territories (P<0.01) but more significantly in LAD and DG territories (-15±3% and -13±9%, respectively). The SvO₂ variations were <10% for all territories and reached only borderline significance (P=0.05) in all territories except OM. All these hemodynamic changes were well tolerated by all patients. Conclusions: Manipulation of the beating heart during OPCABG surgery brings significant fluctuations in the patients' hemodynamics. Mean PAP increase and COI drop were more significant during manipulation of the anterior territories suggesting a more severe diastolic restrictive disease during anterior wall manipulation.

Key Words: Off-pump coronary artery bypass surgery • Hemodynamics • Stabilizer • Ischemia

	1. Introduction

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion References

 
In the past few years, a rapid expansion of the available options for myocardial revascularization has occurred both in the interventional cardiology and in the cardiac surgery field. In coronary artery bypass surgery (CABG), the emphasis was to minimize the morbidity related to the cardiopulmonary bypass (CPB) pump with new techniques such as minimally invasive CABG (MICABG) [1,2] and off-pump CABG (OPCABG) on the beating heart [3–5].

Nevertheless, full exposure for multiple coronary revascularizations, including the lateral circumflex and posterior branches, was only possible with the use of stabilization systems that physiologically restrict regional wall motion either by suction or mechanical compression [4,6]. Both methods provide good stabilization for coronary anastomosis [4–7], but require significant mobilization of the myocardium and the occlusion of the coronary artery and therefore a short period of warm ischemia, especially if an endoluminal shunt is not used during the graft anastomosis. Such manipulations on a beating heart depressed cardiac contractility and caused some hemodynamic deterioration [8–11].

In a preliminary study performed on a small number of candidates [11], we have shown that the displacement and stabilization of the beating heart, using a mechanical stabilizer, induced a transient decrease in the systemic arterial pressure (SAP), and an increase of the pulmonary artery pressure (PAP). However, the effects on the cardiac output and mixed venous O₂ saturation (SvO₂) were not appraised.

The objectives of the study were to monitor hemodynamic changes in a cohort of patients presenting significant triple-vessel disease that were revascularized on a beating heart.

	2. Methods

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion References

 
Fifty-five patients undergoing CABG for multiple vessel disease, including the circumflex marginal (OM) territory, were randomly selected at the Montreal Heart Institute, between May 1998 and May 1999, to undergo OPCABG surgery. Informed consent was obtained from all patients. Patients with hemodynamic deterioration at anesthetic induction were excluded from the procedure. All patients had a complete revascularization with the technique described below. Patients' characteristics are listed in Table 1.

2.1. Operative details
Anesthetic techniques were left to the discretion of the attending anesthesiologist although there were guidelines followed by all of them. The patients' medications were prescribed until the night before the operation except for antiplatelet drugs. No beta-blocker was systematically given during the intervention, and patients' intravenous solutions were adjusted with lactated Ringer to maintain a central venous pressure above 10 mmHg. During the intervention, boluses of vasopressor (ephedrine or phenylephrine) were given when necessary to keep the systolic pressure 100 mmHg. The vasopressors were generally administered right after the myocardium positioning and stabilization once the surgeon's manipulations were completed if needed. When a severe hypotension was observed (SAP drop below 70 mmHg) the manipulations were immediately interrupted and the heart was replaced in the normal position. Once the patient's hemodynamics returned to the physiological value the stabilization was again attempted by modifying the stabilizer position and the heart mobilization in order to minimize hemodynamic disturbances. Nitroglycerin infusion was initiated whenever signs of ischemia were detected on continuous EKG monitoring (ST segment depression of 1 mm). The perfusion was generally maintained until the completion of the surgery.

The heart was exposed through a median sternotomy and suspended in a pericardial cradle as previously described [6]. Myocardial stabilizations were done using a compression type stabilization system (CorVasc, CoroNéo Inc., Montreal, QC, Canada) to reduce translational cardiac motion in the coronary territory with gentle compression on the beating heart. The coronary blood flow was interrupted using circling silastic bands (‘retractotape’, Canadian Cardiovascular, Quest, Allen, TX) proximally and distally to the arteriotomy site. Coronary anastomosis was performed under direct visualization.

For surgical access to the OM and posterior branches, the apex of the heart was displaced towards the head of the patient. The table was set in the Trendelenburg position and rotated sideways to the right of the patient (20–30°). Four pericardial stay sutures were inserted around the base of the heart [6]. Tension was applied to these traction sutures in order to bring out the apex, which should be pointing up (90°) out of the wound, free for further manipulations. Left anterior descending (LAD) and diagonal coronaries exposure used the same settings except one traction suture was usually satisfactory, and the side rotation was not necessary. Stabilization of the posterior descending artery (PDA) was obtained by setting the table in the Trendelenburg position, and by exteriorization of the apex. This was generally achieved by placing one or two pericardial stay sutures on the left side of the heart. Coronary immobilization was then achieved using a pull type stabilizer [6].

The left internal thoracic artery was used to bypass the LAD in all patients, while the saphenous vein, the right internal thoracic artery or the left radial artery were used to bypass the other territories. Proximal anastomosis to the ascending aorta was completed within a single aortic partial side-bite clamping time period. Arterial graft blood flow was always verified intraoperatively using continuous-wave Doppler ultrasonography (Smartdop, Hadeco). Unsatisfactory grafts, which display inadequate diastolization (<1 kHz), were immediately refashioned and reassessed before removing the surgical set-up. To decrease the risk of intraoperative conversions to CPB a very strict revascularization strategy was followed throughout the study. This consisted of bypassing first the vessel with the most severe stenosis. Generally this vessel is better collateralized and can stand a short period of ischemia without hemodynamic instability. We also favored the revascularization of the PDA instead of the right coronary artery in non-critical (<90%, >50%) stenosis. In our experience, AV node ischemia with temporary block was more frequently encountered in these circumstances. All proximal aortic anastomotics were always done in a single side-bite clamping time period to minimize aortic trauma.

2.2. Intraoperative measurements
Baseline hemodynamic measurements were made before surgical manipulations and hemodynamic parameter variations were appraised just before completion of the anastomosis after coronary artery stabilization and the maximal ischemic period. The delta changes recorded represent the maximal variation recorded during each manipulation. A resting period was generally allowed between each graft in order to resume normal heart positioning and stabilize the patient's hemodynamics. Vasopressors were generally decreased or stopped to avoid rebound hypertension. This resting period usually lasted only a few minutes.

2.3. Statistical analysis
All normally distributed data were expressed as the mean±SD. Hemodynamic variations for each parameter were compared to baseline measures using repeated measures ANOVA. Baseline parameters before manipulation and delta changes before and after manipulation between each territory were compared with one-way ANOVA. A P value of <0.05 was considered statistically significant.

	3. Results

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion References

 
The mean age of the study population was 66.4±9.2 years (range 42–85 years), consisting of 40 men and 15 women. Surgical indications were chronic angina in 37 patients (67%), unstable angina in 16 patients (29%), and ongoing myocardial infarction in two patients (4%). Four patients had severe left ventricular (LV) dysfunction with a LV ejection fraction under 25%. An average of 3.3±0.8 grafts/patient were performed, which included 58 grafts to the LAD, 26 to the diagonal artery (DG), 46 to the OM and 40 grafts to the PDA territories. Complete revascularization was achieved in all patients; no intraoperative conversion to CPB was necessary. Grafts distribution, regional coronary ischemic time and the need for -agonist drugs according to the four main areas of the myocardium are presented in Table 2.

Hemodynamic variations in absolute value following stabilization for different territories are summarized in Table 3. These numbers resulted from surgical mobilization, stabilization setting, and potential ischemia secondary to coronary artery snaring. Most of the variations occurred during stabilization with modest further change thereafter. For comparison purposes, variations in percentage for every parameter and each territory are displayed in Table 4.

	4. Discussion

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion References

 
Although CABG was initially attempted on the beating heart [12], the advent of the CPB pump in the late 60s, the advances in myocardial protection, development of cardiac anesthesia, and numerous improvements in CPB circuits and oxygenators have kept OPCAB procedures underused for the last three decades. Recently, a renewed interest in this procedure has developed as surgeons tried to obviate deleterious effects of CPB mainly mediated by a systemic inflammatory response generated by the interaction of blood elements with the foreign surfaces of the CPB system. With the recent advent of mechanical stabilizers in the past few years, the learning curve of OPCAB surgery was made easier to most cardiac surgeons since it allowed them to perform the surgery with techniques similar to standard procedures under CPB.

At the Montreal Heart Institute, compression stabilizers were adopted since 1996. Although many modifications were added to the system, the heart verticalization technique, which is a key point to expose the posterior and lateral wall for complete revascularization, was developed early on in our experience [6]. In the current series no intraluminal shunts were used because they were not commercially available at the time of the study. Since then we have used them on a selective basis. In cases of significant but not critical stenosis a temporary occlusion of 2 min is used to detect any premature ischemia. If EKG ischemic changes occur, an endoluminal shunt is inserted for the entire duration of the graft anastomosis. Unlike CPB cases, where arterial pressure and cardiac output are supervised by the perfusionist, hemodynamics during OPCABG relied on the pump function of the heart itself which is altered by surgical manipulations. Experimentally, Grundeman et al. [8,9] and Jansen et al. [14] have reported a 32% drop in the cardiac output following the heart vertical displacement using a suction stabilization system. They also recorded a drop in coronary blood flow and in LV stroke volume up to 44%, which could be compensated by the Trendelenburg maneuver. Contrary to this technique, the verticalization method we adopted does not rely on the dislocation of the heart by the stabilizer. The fan-shaped distribution of pericardial stay sutures implanted well below the phrenic nerve line allows reorientation of the apex without manual mobilization of the heart, thus minimizing distortion of the ventricle's geometry. In the current series, OM revascularization was associated with a 15% drop in SAP and lesser changes in COI (-9%) and SvO₂ (-7%) and did not require a more frequent usage of -agonist. Likewise, heart stabilization and compression on other territories carried comparable drops in SAP and COI. This is not in accord with Watters' report where he recorded the most extensive changes during circumflex branches exposure [13]. In the 29 consecutive patients that were studied, a significant increase in PAP was observed along with a marked drop in COI of about 25%. We also observed a rise in PAP although the variations recorded did not reach statistical significance even though 40 patients were evaluated for the OM territory. This could be partly explained by the stabilization technique used. In the ‘Bristol technique’ the authors reported the use of a half-folded swab snared to the posterior pericardium halfway between the inferior vena cava and the left inferior pulmonary vein. The two limbs of the swab are then applied to the heart to help stabilize the target coronary artery vessel. In our experience, more constraint is applied on the LV geometry during this maneuver and the COI can be impeded consecutively. The pericardial traction stitches, when deeply inserted, allow heart verticalization without operator manipulation, which could help optimize hemodynamics since no further LV dislocation is needed. Nevertheless, in the current study, PAP elevation during manipulations became significant mostly during stabilization of the LAD and DX arteries without the heart being vertically displaced. On this point our results meet the clinical observations recently published by the group from Utrecht [10]. Interestingly, Nierich et al. showed in a study conducted on 150 patients that the stroke volume was mainly affected during DX revascularization. However, these hemodynamic changes were corrected by the application of the head-down positioning. According to our current observation, the cause for this disturbance is thought to originate from the direct compression on the LV outflow tract especially during DG manipulation where the stabilizer is applied proximally directly over it, thus creating a functional obstruction. To obviate this problem we now reduce the stabilization pressure to minimal, when diagonal grafting is part of the revascularization. One could make the point that a compression-type stabilization system is more susceptible than a suction-type system to contribute to this LV outflow tract obstruction although this remains to be shown. However, this was not reflected by Nierich's experience, in which a suction stabilization system was used. In our experience, the increase in PAP associated with a drop of SAP and COI observed during anterior wall manipulation suggests a temporary state of restrictive diastolic dysfunction of the LV wall. This seemed related to the stabilization itself rather than the local ischemia.

In the current series, TOE was performed on six patients with normal LV function. Although this small number of patients allows only qualitative assessment there were a few interesting observations that deserve a mention. In this small subset of patients cardiac wall motion and mitral valve function did not seem significantly affected even when the heart was displaced at 90° for OM exposure. These results agreed with the findings of Grundeman et al. [15] using beating porcine hearts, which reported mostly a right ventricular diastolic dysfunction. Others have similarly reported right ventricular dysfunction during OPCAB surgery even proposing right heart assistance [16,17]. Although we did not directly study right heart dysfunction, we agree that extensive mobilization and LV compression are more likely to produce diastolic ventricular restriction on the right ventricle. The issue of routinely using a right heart assists though is more controversial and remains to be defined.

In conclusion, our results confirm that complete OPCAB revascularization can be achieved with acceptable hemodynamics. Vertical displacement of the beating heart with pericardial stay sutures and stabilization using a compressive device was safe and reproducible. Cardiac mobilization did not appear to cause mitral valve dysfunction although diastolic expansion of the LV appeared compromised by the compression of the stabilizer. Applying a minimal compression force on the heart to obtain good exposure, especially when dealing with the anterior wall arteries, may prevent such problems.

	References

Top Abstract 1. Introduction 2. Methods 3. Results 4. Discussion References

 

1. Calafiore A.M., Giammarco G., Teodori G., Bosco G., D'Annunzio E., Barsotti A., Maddestra N., Paloscia L., Vitolla G., Sciarra A., Fino C., Contini M. Left anterior descending coronary artery grafting via left anterior small thoracotomy without cardiopulmonary bypass. Ann Thorac Surg 1996;61:1658-1663.[Abstract/Free Full Text]
2. Robinson M.C., Gross D.R., Zeman W., Stedje-Larsen E. Minimally invasive coronary artery bypass grafting: a new method using anterior mediastinotomy. J Card Surg 1995;10:529-536.[Medline]
3. Buffolo E., de Andrade C.S., Branco J.N.R., Teles C.A., Aguiar L.F., Gomes W.J. Coronary bypass grafting without cardiopulmonary bypass. Ann Thorac Surg 1996;61:63-66.[Abstract/Free Full Text]
4. Jansen E.W., Grundeman P.F., Borst C., Eefting F., Diephuis J., Nierich A., Lahpor J.R., Bredee J.J. Less-invasive off-pump CABG using a suction device for immobilization: the "Octopus" method. Eur J Cardiothorac Surg 1997;12:406-412.[Abstract]
5. Borst C., Jansen E.W., Tulleken C.A., Grundeman P.F., Mansvelt Beck H.J., van Dongen J.W., Hodde K.C., Bredee J.J. Coronary artery bypass grafting without cardiopulmonary bypass and without interruption of native coronary flow using a novel anastomosis site restraining device "Octopus". J Am Coll Cardiol 1996;27:1356-1364.[Abstract]
6. Cartier R., Blain R. Off-pump revascularization of the circumflex artery: technical aspect and short-term results. Ann Thorac Surg 1999;68:94-99.[Abstract/Free Full Text]
7. Cartier R. Systematic off-pump coronary artery revascularization: experience of 275 cases. Ann Thorac Surg 1999;68:1494-1497.[Abstract/Free Full Text]
8. Grundeman P.F., Borst C., van Herwaarden J.A., Mansveltbeck H.J., Jansen E.W.L. Hemodynamic changes during displacement of the beating heart by the Utrecht Octopus method. Ann Thorac Surg 1997;63:S88-S92.
9. Grundeman P.F., Borst C., van Herwaarden J.A., Verlaan C.W.J., Jansen E.W.L. Vertical displacement of the beating heart by the Octopus tissue stabilizer: influence on coronary flow. Ann Thorac Surg 1998;65:1348-1352.[Abstract/Free Full Text]
10. Nierich A.P., Diephuis J., Jansen E.W.L., Borst C., Knape J.T.A. Heart displacement during off-pump CABG: how well is it tolerated?. Ann Thorac Surg 2000;70:446-472.
11. Do Q.B., Cartier R. Hemodynamic changes during beating-heart CABG surgery (in French). Ann Chir 1999;53:706-711.[Medline]
12. Schiller N.B., Shah P.M., Crawford M., DeMaria A., Devereux R., Feigenbaum H., Gutgesell H., Reichek N., Sahn D., Schnittger I. Recommendations for quantitation of the left ventricle by two-dimensional echocardiography. American Society of Echocardiography Committee on Standards, Subcommittee on Quantitation of Two-Dimensional Echocardiograms. J Am Soc Echocardiogr 1989;2:358-367.[Medline]
13. Watters M.P.R., Ascione R., Ryder I.G., Ciulli F., Pitsis A.A., Angelini G.D. Haemodynamic changes during beating heart coronary surgery with the "Bristol Technique". Eur J Cardiothorac Surg 2001;19:33-40.
14. Jansen E.W.L., Grundeman P.F., Borst C., Beck H.J.M., Heijmen R.H. Experimental off-pump grafting of a circumflex branch via sternotomy using a suction device. Ann Thorac Surg 1997;63:S93-S96.
15. Grundeman P.F., Borst C., Verlaan C.W.J., Meijburg H., Moues C.M., Jansen E.W.L. Exposure of circumflex branches in the tilted, beating porcine heart: echocardiographic evidence of right ventricular deformation and the effect of right or left heart bypass. J Thorac Cardiovasc Surg 1999;118:316-323.[Abstract/Free Full Text]
16. Porat E., Sharony R., Ivry S., Ozaki S., Meyns B.P., Flameng W.J., Uretzky G. Hemodynamic changes and right heart support during vertical displacement of the beating heart. Ann Thorac Surg 2000;69:1188-1191.[Abstract/Free Full Text]
17. Mathison M., Edgerton J.R., Horswell J.L., Akin J.J., Mack M.J. Analysis of hemodynamic changes during beating heart surgical procedures. Ann Thorac Surg 2000;70:1355-1360.[Abstract/Free Full Text]

This article has been cited by other articles:

				P. S. Halvorsen, A. Sokolov, M. Cvancarova, P. K. Hol, R. Lundblad, and T. I. Tonnessen Continuous cardiac output during off-pump coronary artery bypass surgery: pulse-contour analyses vs pulmonary artery thermodilution Br. J. Anaesth., October 1, 2007; 99(4): 484 - 492. [Abstract] [Full Text] [PDF]

				S. G. Raja and B. S. Rayen Levosimendan in Cardiac Surgery: Current Best Available Evidence Ann. Thorac. Surg., April 1, 2006; 81(4): 1536 - 1546. [Abstract] [Full Text] [PDF]

				E. A Black, S. Ghosh, K. Sin, T. Spyt, and R. Pillai Off-Pump Coronary Artery Bypass Surgery Asian Cardiovasc Thorac Ann, December 1, 2004; 12(4): 379 - 386. [Abstract] [Full Text] [PDF]

				Y.L. Kwak, Y.J. Oh, S.H. Kim, H.K. Shin, J.Y. Kim, and Y.W. Hong Efficacy of pre-emptive milrinone in off-pump coronary artery bypass surgery: comparison between patients with a low and normal pre-graft cardiac index Eur. J. Cardiothorac. Surg., October 1, 2004; 26(4): 687 - 693. [Abstract] [Full Text] [PDF]

				H. K. Shinn, Y. J. Oh, S. H. Kim, J. H. Lee, C. S. Lee, and Y. L. Kwak Evaluation of serial haemodynamic changes during coronary artery anastomoses in patients undergoing off-pump coronary artery bypass graft surgery: initial experiences using two deep pericardial stay sutures and octopus tissue stabilizer Eur. J. Cardiothorac. Surg., June 1, 2004; 25(6): 978 - 984. [Abstract] [Full Text] [PDF]

				P.-G. Chassot, P. van der Linden, M. Zaugg, X. M. Mueller, and D. R. Spahn Off-pump coronary artery bypass surgery: physiology and anaesthetic management{dagger} Br. J. Anaesth., March 1, 2004; 92(3): 400 - 413. [Abstract] [Full Text] [PDF]

				D. L. Ngaage Off-pump coronary artery bypass grafting: the myth, the logic and the science Eur. J. Cardiothorac. Surg., October 1, 2003; 24(4): 557 - 570. [Abstract] [Full Text] [PDF]

				T. Velissaris, A. Tang, M. Jonas, and S. Ohri Haemodynamic changes during off-pump surgery Eur. J. Cardiothorac. Surg., November 1, 2002; 22(5): 852 - 852. [Full Text] [PDF]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Quoc-Bao Do Raymond Cartier Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Do, Q.-B. Articles by Cartier, R. Search for Related Content PubMed PubMed Citation Articles by Do, Q.-B. Articles by Cartier, R. Related Collections Coronary disease