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1 Hemodynamic Changes With Right Lateral Decubitus Body ing in the Tilted Porcine Heart Paul F. Gründeman, MD, PhD, Cornelius Borst, MD, PhD, Cees W. J. Verlaan, Stefan Damen, MD, and Sabine Mertens, MD Heart Lung Center Utrecht, University Medical Center, Utrecht, The Netherlands Background. In beating-heart coronary surgical rocedures, exosure of osterior vessels through sternotomy causes cardiac function to deteriorate. We hyothesized that turning the subject to the right lateral decubitus osition before cardiac retraction imroves exosure of osterior vessels and reserves cardiac um function on dislacement. Methods. Eight 80-kg oen-chest igs were instrumented with catheter-ti manometers. After a stewise 60-degree turn to the right lateral decubitus osition of the body, the heart was retracted anteriorly to 90 degrees with a suction stabilizer. Results. Right lateral body ositioning caused an aroximately 45-degree right deviation of the aex, thereby exosing the left atrial groove. Stroke volume, mean arterial ressure, right atrial ressure, and right ventricular end-diastolic ressure increased to 106% 5% (mean standard error of the mean, 0.31), 106% 3% ( 0.01), 129% 8% ( 0.001), and 171% 14% ( 0.002), resectively, comared with control values. In contrast, left atrial ressure decreased to 73% 6% ( 0.007), whereas left ventricular reload remained unchanged (110% 8%, 0.26). Additional anterior dislacement to 90 degrees fully exosed the osterior vessels, and stroke volume decreased to 90% 3% ( 0.01) and mean arterial ressure to 93% 5% ( 0.07) at the exense of further increased right ventricular reload (256% 28%, < 0.001). Conclusions. By lacing the subject in the right lateral decubitus osition, exosure through sternotomy of osterior vessels in the beating orcine heart was facilitated while mean arterial ressure was maintained. (Ann Thorac Surg 2001;72:1991 6) 2001 by The Society of Thoracic Surgeons In beating-heart coronary artery byass grafting, access to the circumflex branches through sternotomy is feasible with the aid of fabric slings [1], dee ericardial retracting stitches [2], a mechanical tissue stabilizer [3, 4], or a combination of techniques. Recently, the feasibility of cardiac ositioning with an aical suction device was reorted [5]. Full ventral dislacement of the beating heart, however, decreases stroke volume (SV) and mean arterial ressure (MAP) considerably in the ig [3, 6, 7] and in atients [8] owing to right heart deformation and imaired diastolic filling [7]. Using the Trendelenburg osition [3, 4, 6 8], increasing reload by some other means [8, 9,], or administering inotroic suort [8] will, in art, mitigate hemodynamic deterioration during exosure of osterior vessels. Another major roblem in coronary surgical rocedures on the osterior side is the lack of sace as well as the unfavorable angle of view and tangential surgical aroach. The objectives of this study were (1) to investigate imrovement in exosure of the osterior wall of the Acceted for ublication July 16, Address rerint requests to Dr Gründeman, Exerimental Cardiology Laboratory, Heart Lung Institute, Utrecht University Medical Center (Room G02.523), PO Box 85500, 3508 GA Utrecht, The Netherlands; ex.cardio@hli.azu.nl. beating orcine heart through sternotomy by right lateral decubitus body osition (RLD) (to 60 degrees, RLD osition) before full retraction and (2) to monitor the accomanying cardiovascular changes. Material and Methods Eight Dutch Landrace igs (range, 75 to 85 kg) were used. All animals received humane care in comliance with the Guide for the Care and Use of Laboratory Animals (NIH ublication 85-23, revised 1985). The study rotocol was aroved by the Animal Exerimentation Committee of the Utrecht University. Anesthesia and Instrumentation The igs were remedicated and anesthetized, and underwent median sternotomy to exose the heart for insertion of catheter-ti manometers, indeendent of body osition, (Millar Instruments, Houston, TX) as reviously described [3]. Before various maneuvers, acing at a fixed rate of 80 beats/min was started after the administration of roranolol (range, 15 to 25 mg) [3]. An ultrasound transit time flow robe (size 20 or 24 mm, Transonic Inc, Ithaca, NY) was laced around the aorta for continuous measurement of the cardiac outut (CO). Stroke volume was calculated by dividing CO by the 2001 by The Society of Thoracic Surgeons /01/$20.00 Published by Elsevier Science Inc PII S (01)

2 Table 1. Hemodynamic Changes With Cardiac Dislacement in Right Body Variable Suine Base (hase 1) RLD 3 min (hase 2) RLD Dis 3 min (hase 3) RLD Dis Trend 3 min (hase 4) RLD Dis Trend 15 min (hase 5) RLD 3 min (hase 6) RLD 15 min (hase 7) Suine End 3 min (hase 8) Stroke volume (ml) Mean arterial ressure (mm Hg) Mean ulmonary artery ressure (mm Hg) Mean right atrial ressure (mm Hg) Mean left atrial ressure (mm Hg) Right ventricular enddiastolic ressure (mm Hg) Left ventricular enddiastolic ressure (mm Hg) Mean flow LAD (ml/min) Mean flow Cx (ml/min) Mean flow RCA (ml/min) Pulmonary vascular resistance (dynes s cm 5 ) Systemic vascular resistance (dynes s cm 5 ) 1, , , , , , , , Cx circumflex artery; Dis dislacement; LAD left anterior descending coronary artery; RCA right coronary artery; RLD right lateral decubitus osition; Trend Trendelenberg osition GRÜNDEMAN ET AL Ann Thorac Surg TILTED HEART IN RIGHT BODY POSITION 2001;72:1991 6

3 Ann Thorac Surg GRÜNDEMAN ET AL 2001;72: TILTED HEART IN RIGHT BODY POSITION 1993 heart rate. Flow robes (Transonic) were laced around the most roximal art of the main coronary vessels [3]. The animal was laced on a modified oerating table that allowed a quick transition from suine horizontal body osition to 60 degrees RLD osition. For stewise cardiac retraction in RLD osition, the retractor-mounted Octous2 Tissue Stabilizer (Medtronic Inc, Minneaolis, MN) was used. A ersonal comuter-based data acquisition system stored hemodynamic variables as described reviously [3]. Exerimental Protocol Baseline cardiovascular values were recorded after stabilization in the suine horizontal osition after at least 15 minutes of acing (hase 1, suine anatomic osition). Subsequently, values were taken 3 (hases 2 through 4, 6, and 8) and 15 minutes (hases 5 and 7) after stabilization after each intervention. In hase 2, the body osition was stewise changed to the 60-degree RLD osition. In hase 3 (dislacement), the beating heart was ventrally dislaced with the Octous2 until 90 degrees from anatomic osition relative to the sine was achieved. Without the aid of other suortive tools, circumflex branches on the backside of the heart became better exosed to surgical rocedures than in revious studies without RLD [3, 6, 7]. Subsequently, after stabilization of hemodynamics, the oerating table was tilted 10 degrees in the head-down osition (Trendelenburg osition) without changing the osition of the heart relative to the body (hases 4 and 5). After returning from Trendelenburg, the heart was released from the Octous2 while the body osition continued to be in RLD (hase 6 and 7). Subsequently, the body was laced back in the suine osition by turning the table horizontally (hase 8). After stabilization of hemodynamic variables, the entire rotocol was reeated once. Statistical Analysis First, the dulicate data from each animal were averaged and mean values were further used for analysis. Data in Table 1 are resented as mean standard deviation (absolute values). Hemodynamic variables in the Results and in Figure 1 are deicted as mean standard error of the mean of the ercentage of rotocol control values (body in suine osition; heart in anatomic osition). Statistical analysis was erformed using multivariate analysis of variance to assess the influence of changing the body osition from suine into RLD osition and 4 Fig 1. Comarison of hemodynamics between 60 degrees right lateral body osition (RLD, oen bars) and suine body osition (closed bars) with vertical dislacement of the beating orcine heart. Mean ercentage of suine baseline values (BASE) standard error of the mean. Oen bars (this study) dislacement (DIS) in right decubitus osition. Comared with baseline: * 0.05, ** 0.01, # Closed bars dislacement in suine osition from [3, 7] (ooled data, n 14) comared with dislacement in lateral decubitus osition. % 0.05, %% 0.01, $ (Trend Trendelenburg maneuver.)

4 1994 GRÜNDEMAN ET AL Ann Thorac Surg TILTED HEART IN RIGHT BODY POSITION 2001;72: Fig 2. Directional changes of the orcine heart aical osition (arrow, craniad-to-caudal; to anel) inthe frontal lane relative to the midline with right table tilt by 60 degrees (middle anel) and with additional anterior retraction to 90 degrees with the Octous2 tissue stabilizer (lower anel). subsequently ventral cardiac dislacement. A aired Student s t test was used to assess the modifying effect of Trendelenburg comared with control values (suine osition, hase 1). A two-way nonarametric statistical test (Wilcoxon signed rank test) or unaired two-way Student s t test was used to comare the influence on hemodynamics after cardiac retraction in RLD osition (resent study) with ooled data from two revious studies [3, 6] in which cardiac retraction was erformed in the suine osition (n 14). Cardiac retraction itself in the latter studies was erformed in exactly the same manner as in the current study. Results All animals survived the entire rocedure without the need to defibrillate or administer inotroic drugs. The results are summarized in Table 1 and Figure 1. The aced heart remained beating at a regular rate of 80 beats/min throughout the exeriment. Although some

5 Ann Thorac Surg GRÜNDEMAN ET AL 2001;72: TILTED HEART IN RIGHT BODY POSITION 1995 individual animals showed minor changes in systemic and ulmonary vascular resistance, mean values were not significantly different throughout the maneuvers. Turning Body to Right Lateral Decubitus The effects of turning the body to the RLD osition (hase 2) are shown in Figure 2, middle anel. The osition of the aex of the heart relative to the midline shifted to the right by aroximately 45 degrees (arrow in middle anel of Fig 2). To some extent, the aex moved out of the ericardial cradle anteriorly. A sace between the left sternal border and the left lateral side of the heart was created, thereby exosing the craniad art of the atrioventricular groove including the circumflex artery and the left atrial aendage. Visually, the contour of the outflow tract of the right ventricle was accentuated. Stroke volume and MAP increased to 106% 5% and 106% 3% ( 0.31 and 0.01, resectively). Right atrial ressure and right ventricular end-diastolic ressure increased to 129% 8% ( 0.001) and 171% 14% ( 0.002), resectively. In contrast, left atrial ressure decreased to 73% 6% ( 0.007), whereas left ventricular end-diastolic ressure increased to 110% 8% ( 0.26). Coronary flows remained unchanged. Cardiac Retraction in Right Lateral Decubitus Body The effects of cardiac retraction in the RLD body osition (hase 3) are shown in Figure 2, lower anel. Additional dislacement of the heart by the suction device resulted in further deflection of the aex to the right from aroximately 45 degrees to 90 degrees relative to the midline (arrow in Fig 2, lower anel) and, relative to the sine, a full anterior dislacement to 90 degrees. The osterior asect of the heart became fully exosed. Stroke volume and MAP decreased to 90% 3% ( 0.008) and 93% 5% ( 0.15), resectively, at the exense of (further) increased reloads. Circumflex arterial flow decreased to 88% 4% ( 0.05). Statistical comarison of hemodynamic data after cardiac retraction in RLD osition with those in suine body osition [3, 7] revealed that, in suine osition, SV and MAP decreased more (by 37% 5% and 37% 5%, and 0.002, resectively) and ventricular reload ressures increased less (right ventricular end-diastolic ressure rose to 171% 12% versus 256% 20% and left ventricular end-diastolic ressure rose to 112% 9% versus 142% 8%, and 0.04, resectively). Tilting Whole-Body Head-Down 10 Degrees (Trendelenburg) in Right Lateral Decubitus Body The effects of tilting whole-body head-down 10 degrees (Trendelenburg) in RLD body osition (hases 4 and 5) are given in Table 1. Stroke volume and MAP (over)normalized at the exense of further increased ventricular reloads (right ventricular end-diastolic ressure increased to 298% 36% [ 0.001] and left ventricular end-diastolic ressure increased to 157% 4% [ 0.001]). At 15 minutes of Trendelenburg osition (hase 5), no further changes in circulatory status had occurred. Return of Oerating Table to Right Lateral Decubitus and Release From Retractor The effects of returning the oerating table to the RLD osition and releasing the heart from the retractor (hases 6 and 7) are shown in Table 1. Stroke volume and MAP were normalized. Return to Suine Body The effects of returning to suine body osition (hase 8) are given in Table 1. Stroke volume and MAP decreased to 82% 8% ( 0.06) and 72% 6% ( 0.008), resectively. Comment The rincial findings of the study were, first, in 60 degrees RLD body osition, artial exosure of circumflex branches was created while SV and MAP had increased. Second, additional retraction of the beating heart to a full 90 degrees of anterior dislacement achieved full exosure without causing a major decrease in SV and MAP. Turning Body to Right Lateral Decubitus The osition of the aex of the heart relative to the sine shifted to a right lateral and a ventral osition, both by aroximately 45 degrees owing to the directional change in gravitational force (Fig 2, middle anel). Without major changes in MAP, amle sace was created between the left sternal border and the left lateral side of the heart. Already art of the atrioventricular groove including the circumflex artery and the left atrial aendage was visible and exosed. The maneuver caused no ventricular arrhythmias. Visually, the contour of the outflow tract of the right ventricle was enlarged, which corresonded to the increased right ventricular enddiastolic ressure. Some right ventricular dysfunction was aarently induced because the increase in reload roduced only a marginal augmentation of SV. The imaired right ventricular uming function is attributed to insufficient diastolic exansion owing to mechanical deformation of the thin-walled right ventricle by its lateral-to-ventral osition, ie, half out of the thorax. The decreased left atrial ressure is attributed to a decrease in hydrostatic ressure. Left ventricular end-diastolic ressure, however, remained unchanged. By turning the body to the RLD osition, diverging changes in hydrostatic ressure were induced in each of the four heart chambers. Cardiac Retraction in Right Lateral Decubitus Body Comared with our revious studies [3, 6, 7] without RLD osition, retraction of the heart by the suction device to 90 degrees ventral osition resulted in better exosure of the backside of the heart with only a 10% decrease in SV and MAP. However, right ventricular reload was mark-

6 1996 GRÜNDEMAN ET AL Ann Thorac Surg TILTED HEART IN RIGHT BODY POSITION 2001;72: edly enhanced at the same time. The change of osition of the aex of the heart from RLD body osition to 90 degrees in the right lateral-to-ventral direction was well tolerated because the heart was only additionally dislaced 45 degrees instead of the full 90 degrees retraction in suine body osition relative to the sine. Tilting Whole-Body Head-Down 10 Degrees (Trendelenburg) in Right Lateral Decubitus Body A moderate Trendelenburg osition roduced an increase in arterial ressure comared with baseline values (hase 1) at the exense of very high right ventricular reload ressure. With 60 degrees right table tilt, the Trendelenburg osition was unnecessarily erformed (to correct for diminished diastolic function in the dislaced heart) and, maintained for 15 minutes, was robably harmful because of volume overload. After return to the suine body and anatomic heart ositions, MAP was decreased and did not return within 3 minutes to baseline values (Table 1). Limitations The ig s chest cavity conformation is carinate comared with the barrel-shaed human chest wall. Desite these anatomic differences, inferences made from revious animal studies [3, 6, 7] were largely alicable to humans [4, 8 11]. Cardiac retraction was erformed in the normal healthy ig heart with its aex slightly ointing rightward. It remains to be determined whether, in atients, rotation to, say, 30 to 45 degrees right oblique decubitus osition may also roduce enhanced exosure as observed in this study, as well as favorable hemodynamic effects on full cardiac retraction. Also, the assisting erson located oosite to the surgeon may have difficulties in viewing the circumflex territory shielded by the left sternal border. Patients with imaired left ventricular function may not tolerate 90 degrees vertical dislacement of the beating heart. Conclusions Exosure of osterior vessels through sternotomy was facilitated by lacing the ig in the RLD osition. At the exense of enhanced right ventricular reload, CO and MAP decreased by only 10% on 90 degrees anterior dislacement of the beating orcine heart. The otential benefit of the RLD osition for off-um coronary surgical rocedures of osterior branches remains to be demonstrated in atients. The authors acknowledge the contribution of Michel A. Verlaan (biotechnician) and Hans P. van der Brugge (data acquisition). For assistance in statistical analysis, we thank Joo A. J. Faber, McS, PhD, and colleagues of the Center of Biostatistics, University of Utrecht. References 1. Kazama S, Ishihara A. Fabric heart retractor for coronary artery byass oerations. Ann Thorac Surg 1993;55: Slittgerber FH, Friedrich I, Falk B, Kroncke G, Talbert JG. Exosing the circumflex artery: the heartfli technique. Ann Thorac Surg 1996;61: Gründeman PF, Borst C, van Herwaarden JA, Verlaan CWJ, Jansen EWL. Vertical dislacement of the beating heart by the Octous stabilizer: influence on coronary flow. Ann Thorac Surg 1998;65: Jansen WL, Borst C, Lahor JR, et al. Coronary artery byass grafting using the Octous method: results in the first hundred atients. J Thorac Cardiovasc Surg 1998;116: Dullem KC, Resano FG. Xose. A new device that rovides reroducible and easy access for multivessel beating heart byass grafting. Heart Surg Forum 2000;3: Gründeman PF, Borst C, van Herwaarden JA, Mansvelt Beck HJ, Jansen EWL. Hemodynamic changes during dislacement of the beating heart by the Utrecht Octous method. Ann Thorac Surg 1997;63:S Gründeman PF, Borst C, Verlaan CWJ, Meijburg H, Mouës CM, Jansen EWL. Exosure of circumflex branches in the tilted beating orcine heart: echocardiograhic evidence of right ventricular deformation and the effect of right or left heart byass. J Thorac Cardiovasc Surg 1999;118: Nierich AP, Diehuis J, Jansen EWL, et al. Embracing the heart: erioerative management of atients undergoing off-um coronary artery byass grafting using the Octous tissue stabilizer. J Cardiothorac Vasc Anesth 1999;13: Hart JC, Sooner T, Edgerton J, Milsteen SA. Off-um multivessel coronary artery byass utilizing the Octous Tissue Stabilization system: initial exerience in 374 atients from three searate centers. Heart Surg Forum 1999;1: Hart JC, Sooner TH, Pym J, et al. A review of 1,582 consecutive Octous off-um coronary byass atients. Ann Thorac Surg 2000;70: Sooner TH, Dyrud PE, Monson BK, Dixon GE, Robinson LD. Coronary artery byass on the beating heart with the Octous: a North American exerience. Ann Thorac Surg 1998;66: