Retrograde cardioplegia could provide better myocardial. Evaluation of 7,000 Patients With Two Different Routes of Cardioplegia

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1 Evaluation of 7,000 Patients With Two Different Routes of Cardiolegia Kit V. Arom, MD, PhD, Robert W. Emery, MD, Rebecca J. Petersen, RN, and Joseh W. Bero, MS Minneaolis Heart Institute, Minneaolis, Minnesota Background. This study examined the efficacy and safety of retrograde cardiolegia in comarison with an antegrade/retrograde aroach. Methods. Between January 1, 1991, and December 31, 1995, 7,032 coronary artery byass rocedures, alone or in combination with valve relacement/reair, were erformed using either retrograde cardiolegia (R) or an antegrade/retrograde (AR) aroach. There were 4,224 atients in the R grou and 2,808 in the AR grou. These included elective, urgent, emergent/salvage, first oerative, and redo cases. Results. All reoerative, intraoerative, and ostoerative variables listed in The Society of Thoracic Surgeons National Cardiac Surgery Database were used to comare the two grous using univariate analysis. The um time was longer in the AR grou, with fewer grafts er atient. The R grou had higher redicted risk (3.2% versus 3.0%; 0.04), more ostoerative atrial fibrillation (34% versus 31%; 0.006), and longer ostoerative length of stay (8.8 versus 8.0 days; < 0.001). Using The Society of Thoracic Surgeons National Cardiac Surgery Database redicted risk grou model, a subgrou of 221 coronary artery byass grafting atients in the retrograde (s-r) and 132 coronary artery byass grafting atients in the antegrade/retrograde (s-ar) grou fell into a greater incidence of redicted mortality grou (> 10%). The s-r subgrou had more atients in New York Heart Association functional class IV. Univariate analysis revealed higher ostoerative atrial fibrillation (51% versus 41%; 0.05) and longer ostoerative length of stay (12.8 versus 10.8 days; 0.03) in the s-r subgrou versus the s-ar subgrou. Conclusions. The results aear to favor neither aroach. Preoeratively, both retrograde grous (R and s-r) had higher reoerative redicted risk, but oerative mortality or comlications were not significantly increased when comared with the AR and s-ar grous. Retrograde cardiolegia alone was shown to be effective in the R and s-r grous, but atrial fibrillation develoed in more atients, which could have contributed to longer length of stay in these grous. Antegrade/retrograde cardiolegia offers good immediate outcome but the delivery method can be cumbersome and confusing during the adjustments of flow clams for antegrade/ retrograde delivery and may contribute to rolonged um times. From this retrosective, nonrandomized review, it aears that retrograde cardiolegia alone rovides as good myocardial rotection and safety as an antegrade/retrograde aroach in either the low-risk or high-risk atient. (Ann Thorac Surg 1997;63: ) 1997 by The Society of Thoracic Surgeons Retrograde cardiolegia could rovide better myocardial rotection desite the resence of coronary lesions [1 3]. The clinical use of retrograde cardiolegia still raises some concerns, including otentially inadequate reservation of the right ventricle and delay in arresting the heart with slow retrograde erfusion. The combined antegrade-retrograde aroach may have some advantages over retrograde cardiolegia alone [4]. Therefore, at resent, most surgeons are in favor of the combined aroach [5, 6]. However, the antegrade/ retrograde technique has some disadvantages. It requires another set of tubing in the oerative field and other equiment for the erfusionist to be able to switch back and forth from one mode of erfusion to the other. Using this technique could be cumbersome, confusing, and Presented at the Forty-third Annual Meeting of the Southern Thoracic Surgical Association, Cancun, Mexico, Nov 7 9, Address rerint requests to Dr Arom, 920 E 28th St, Minneaolis, MN more time-consuming while the aorta is cross-clamed and may not be cost-effective. Our revious study has shown that the retrograde cardiolegia alone is simle and effective for rotection of the myocardium [7]. There were concerns regarding the small samle size of this study and whether retrograde cardiolegia alone can be used in routine cases, including high-risk atients and all clinical situations such as emergent, urgent, elective, and reoerative cases. Material and Methods Between January 1, 1991, and December 31, 1995, 7,032 coronary artery byass rocedures, either alone or combined with valve relacement or valve reair rocedures using cardioulmonary byass and cardiolegia, were reviewed. These atients received either retrograde cardiolegia alone (R) or combined antegrade and retrograde (AR) cardiolegia for myocardial rotection as er discretion of the surgeon. It is understood that in a 1997 by The Society of Thoracic Surgeons /97/$17.00 Published by Elsevier Science Inc PII S (97)

2 1620 AROM ET AL Ann Thorac Surg TWO CARDIOPLEGIA ROUTES 1997;63: Table 1. Clinical Profile and Preoerative Variables of the Grous Risk Variable AR R Female (%) Mean age (y) Mean EF a Diabetes (%) Morbid obesity (%) Renal failure (%) History of CVA (%) a COPD (%) History of MI (%) MI within 6 hours (%) MI within 24 hours (%) MI within 21 days (%) History of CHF (%) Preo Afib (%) Nitrates IV a NYHA class IV (%) Redo (%) a Preo IABP (%) Emergent status (%) Predicted risk (%) a,b b Predicted risk on coronary artery byass grafting only oulation. Afib atrial fibrillation; AR antegrade/retrograde cardiolegia; CHF congestive heart failure; COPD chronic obstructive ulmonary disease; CVA cerebrovascular accident; ER ejection fraction; IABP intraaortic balloon um; IV intravenously; MI myocardial infarction; NYHA New York Heart Association; Preo reoerative; R retrograde cardiolegia. retrosective study such as this, bias may be introduced unintentionally, such as surgeon-secific bias and atient referral bias. There were 4,224 atients in the R grou and 2,808 in the AR grou. The clinical rofile, reoerative, intraoerative, and ostoerative variables for grous R and AR, as suggested in The Society of Thoracic Surgeons (STS) National Cardiac Surgery Database (NCSD) are listed in Tables 1 through 3. To identify high-risk atients (coronary artery byass grafting only), we used an STS NCSD oerative redicted risk grou to obtain the subgrou of 221 atients (s-r grou) from the R grou and 132 atients (s-ar Table 2. Intraoerative Variables of the Grous Risk Variable AR R Intrao IABP (%) Pum time (min) a No. grafts/atient a Total IV fluid (ml) a EBL (ml) a AR antegrade/retrograde cardiolegia; EBL estimated blood loss; IABP intraaortic balloon um; Intrao intraoerative; IV intravenous; R retrograde cardiolegia. Table 3. Postoerative Variables of the Grous Risk Variable AR R Peak CK-MB (U/L) Cardiac index (L min 1 m 2 ) a ICU 24 hours (%) a Reo/bleeding (%) Perio MI (%) Stroke ermanent (%) Stroke transient (%) Prolonged ventilation (%) Pneumonia (%) Renal failure (%) Permanent acemaker (%) Posto Afib (%) a Death (%) LOS (oeration to discharge, days) a LOS (admit to discharge, days) a Afib atrial fibrillation; AR antegrade/retrograde cardiolegia; CK-MB MB isoenzyme of creatine kinase; ICU intensive care unit; LOS length of stay; MI myocardial infarction; Perio erioerative; Posto ostoerative; R retrograde cardiolegia. grou) from the AR grou whose redicted mortality risk was equal to or greater than 10%. The reoerative, intraoerative, and ostoerative variables of these two grous are listed in Tables 4 through 6. Before the oeration, 79% of the atients had a ulmonary artery catheter inserted, and all had radial artery lines for arterial ressure monitoring. After general anesthesia and sternotomy, ascending aortic and atrial cannulas were used to establish cardioulmonary byass. The details of cardioulmonary byass have been described elsewhere [7]. Initially, cold crystalloid cardiolegia was used and delivered as soon as the aortic cross-clam was alied. Moderate systemic hyothermia (28 to 30 C) and toical hyothermia with cold saline solution were used in atients between 1991 and In the AR aroach, an initial antegrade bolus of 500 to 700 ml of cardiolegic solution was used followed by an intermittent retrograde dose of 200 ml every 20 minutes during aortic crossclaming. The same aroach was carried out in grou R excet a larger bolus of 800 to 1,000 ml was given directly into the coronary sinus during a 2- to 3-minute eriod while coronary sinus ressure was maintained at less than 60 mm Hg. No additional doses of cardiolegia were given through the vein grafts after comletion of the distal anastomoses in either grou. The details of transatrial coronary sinus cardiolegia delivery have been described elsewhere [6]. In 1994, teid heart surgery and blood cardiolegia were introduced in our ractice; toical hyothermia is used rarely, core temerature is allowed to drift to 32 to 34 C without cooling, and body temerature is increased to at least 35 C before searation from the cardioulmonary byass.

3 Ann Thorac Surg AROM ET AL 1997;63: TWO CARDIOPLEGIA ROUTES 1621 Table 4. Clinical Profile and Preoerative Variables of the Subgrous Risk Variable s-ar s-r Female (%) Mean age (y) Mean EF a Diabetes (%) Morbid obesity (%) Renal failure (%) History of CVA (%) COPD (%) History of MI (%) MI within 6 hours (%) MI within 24 hours (%) MI within 21 days (%) History of CHF (%) Preo Afib (%) Unstable angina (%) Nitrates IV (%) a NYHA class IV (%) a Redo (%) Preo IABP (%) Emergent status (%) Predicted risk (%) S subgrou; other abbreviations are as in Table 1. Fifty-one ercent of the atients in both grous had hemodynamic measurements obtained just before initiation of cardioulmonary byass and reeated aroximately 6 hours after return from the oerating room when hemodynamic instability was corrected. Arterial blood ressure, heart rate, central venous ressure, ulmonary artery ressure, and ulmonary caillary wedge ressures were recorded. Cardiac outut determinations were made with an American Edwards Laboratories Swan-Ganz catheter and comuter (Santa Ana, CA). The cardiac index, stroke volume, systemic vascular resistance, ulmonary vascular resistance, right ventricular stroke work index, and left ventricular stroke work index were derived. Postoerative hemodynamic measurements were obtained in only 37% of atients in grou AR and 33% of atients in grou R after reaching Table 5. Intraoerative Variables of the Subgrous Risk Variable s-ar s-r Intrao IABP (%) Pum time (min) a No. grafts/atient a Total IV fluid (ml) EBL (ml) S subgrou; other abbreviations are as in Table 2. Table 6. Postoerative Variables of the Subgrous Risk Variable s-ar s-r a fixed reload ulmonary wedge ressure of 15 mm Hg. An electrocardiogram and serum enzyme levels were obtained on arrival in the intensive care unit and on a daily basis for 3 days. Statistical Analysis System software (version 6.09 for Microsoft Windows NIT; SAS Institute, Carey, NC) was used for all analyses. All tests were erformed univariately to detect association between cardiolegia technique (antegrade/retrograde versus retrograde) and the reoerative, intraoerative, and ostoerative data. To determine univariate associations between cardiolegia technique and discrete atient characteristics, Pearson s 2 or Fischer s exact test were used when aroriate. For the continuous data, t tests were used to show associations between characteristics and cardiolegia technique. Results Peak CK-MB (U/L) Cardiac index (L min 1 m 2 ) ICU 24 hours (%) Reo/bleeding (%) Perio MI (%) Stroke ermanent (%) Stroke transient (%) Prolonged ventilation (%) Pneumonia (%) Renal failure (%) Permanent acemaker (%) Posto Afib (%) a Death (%) LOS (oeration to discharge, days) a LOS (admit to discharge, days) a S subgrou; other abbreviations are as in Table 3. Preoerative, intraoerative, and ostoerative risk variables and comlications listed in the STS NCSD were used to comare these two grous of atients using univariate analysis. The R grou had higher reoerative redicted risk (3.2% versus 3.0%; 0.04), but otherwise, these two grous of atients were similar with resect to age, associated medical roblems, angiograhic extent of coronary artery disease, and mean reoerative ejection fraction (see Table 1). The mean core temerature was 30 C in the AR grou and 31.5 C in the R grou. The um time was longer in the AR grou (126 versus 107 minutes; 0.001), with atients requiring fewer grafts/ atient (3.12 versus 3.24; ) (see Table 2). There was no statistical difference in the number of atients needing inotroic agents (50.9% versus 49.3%; 0.18) coming off cardioulmonary byass or in the need for ermanent acemaker imlantation (2.3% versus 1.9%; 0.3) before discharge. There were no differences in

4 1622 AROM ET AL Ann Thorac Surg TWO CARDIOPLEGIA ROUTES 1997;63: the incidence of ostoerative renal or ulmonary comlications, in the eak level of the myocardial secific isoenzyme of creatine kinase, or in the incidence of ostoerative myocardial infarction. There was a higher incidence of ostoerative atrial fibrillation (31% versus 34%; 0.006) and longer (8.02 versus 8.98 days; ) ostoerative length of stay (see Table 3). Otherwise, there were no significant differences in ostoerative comlications or death (3.2% versus 3.9%; 0.09). Studies using a ulmonary catheter to record and comute the hemodynamic variables showed that there was a difference in cardiac index (2.7 versus 2.6 L min 1 m 2 ; 0.007), but not in the left ventricular stroke work index ( versus g-m/m 2 ; 0.05) or right ventricular stroke work index (8.5 3 versus g-m/m 2 ; 0.05) at a fixed reload of 15 mm Hg (mean right atrial ressure, 11 3 mm Hg; mean ulmonary artery ressure, mm Hg; and mean aortic ressure, mm Hg). Using the STS NCSD redicted risk grou model, 132 atients in the s-ar subgrou and 221 atients in the s-r subgrou fell into the higher redicted mortality risk grou ( 10%). Univariate analysis between these two subgrous revealed the following differences: more atients in the s-r subgrou were in New York Heart Association functional class IV and receiving intravenous nitroglycerin u to the time of the oeration (30% versus 21%; 0.05). Patients in the s-r subgrou had lower mean ejection fraction (0.29 versus 0.36; 0.003) (see Table 4). Pum time was greater (136 versus 104 minutes; ) in the s-ar subgrou desite fewer grafts/ atient (3.13 versus 3.36; 0.04) (see Table 5). The ostoerative incidence of atrial fibrillation was higher in the s-r subgrou (51% versus 41%; 0.05) and ossibly contributed to a longer ostoerative length of stay (12.8 versus 10.8 days; 0.03) (see Table 6). Excet for these, there again was no significant difference in ostoerative comlications. The oerative mortality ( 30 days) was 11% for the s-ar subgrou and 13% for the s-r subgrou ( 0.4). Hemodynamic study in these two subgrous showed no difference in cardiac index (2.34 versus 2.23 L min 1 m 2 ; 0.4) and similar left and right ventricular stroke work indices. Comment The rincile of retrograde cardiolegia relies on the fact that the unobstructed coronary venous system can serve as a delivery conduit for the homogeneous distribution of cardiolegic solution. One of the advantages of this technique is that cardiolegic solution is distributed through a transmural network of veins directly to the cardiac microstructure, indeendent of flow-limiting lesions [8]. Because of concerns over the seed of cardiac arrest and the consistency of myocardial reservation during isolated retrograde cardiolegia, some investigators [4 6] have advocated combining the antegrade and retrograde aroach. Generally, retrograde administration takes a longer time to deliver a similar volume of cardiolegic solution because of lower flow rates and ressures used to revent myocardial edema and coronary sinus injury. Therefore, both initial cardiac arrest and subsequent myocardial rotection may require more time with retrograde than with antegrade delivery. Neither our results nor the work of other investigators [9, 10] suggest that the differential rate of myocardial reservation and cooling has any clinically detectable adverse effects on ostoerative outcome. Nevertheless, the delay in cardiac arrest may be circumvented by administering the first dose of cardiolegic solution through the aortic root [11]. One otential limitation of coronary sinus cardiolegia is inadequate right ventricular reservation. This concern has been raised on the basis of canine studies [12, 13] that suggest that retrograde delivery does not consistently cool the right ventricle. However, Partington and coworkers [11] found that retrograde erfusate may shunt directly to the right-sided heart chambers and that the thebesian-sinusoidal drainage of the cold retrograde effluent causes right ventricular hyothermia and sufficient right-sided myocardial rotection. Moreover, intracavitary cooling of the right ventricle can aid in right ventricular reservation [4, 10, 12]. Using radionuclide angiocardiograhy, Menasché and associates [14] have shown that right ventricular function is adequately reserved after coronary sinus cardiolegia during aortic valve relacement. Similar observations have been made by others [9, 10, 15] in atients undergoing coronary byass oerations. We and other investigators [7, 16] have examined the safety and effectiveness of retrograde cardiolegia in coronary artery byass grafting and have concluded that it rovides more even cooling of the myocardium, less need for ostoerative inotroic suort and temorary acing [7, 17, 18], better reservation of myocardial cellular structures [19], imroved left ventricular diastolic comliance after aortic valve relacement [10], and less deression of ventricular contractility [20]. Partington s grou [4, 11] evaluated retrograde cardiolegia in canine models and found it suerior to antegrade delivery in its maintenance of referential subendocardial flow to muscle in jeoardy of ischemia while roducing excellent left ventricular setal cooling. Noyez and colleagues [21] evaluated atients who underwent myocardial revascularization and found that when the left anterior descending artery was occluded, retrograde delivery was suerior to combined delivery. However, Noyez and colleagues were unable to demonstrate better reservation of left ventricular myocardial function when the left anterior descending artery occlusion was not considered indeendently. Most imortant, both grous of atients had an excellent clinical outcome without distinction. In animal models, studies [22, 23] comaring antegrade delivery of cardiolegic solution with retrograde delivery have demonstrated that, when the left anterior descending artery is occluded, there are imrovements in tissue acidosis, fewer wall motion abnormalities, less myocardial necrosis, and better myocardial cooling with retrograde delivery systems. A similar study design was used by Misare and colleagues [24], who evaluated warm

5 Ann Thorac Surg AROM ET AL 1997;63: TWO CARDIOPLEGIA ROUTES 1623 blood cardiolegia in swine and found imrovements in global and ischemic-zone systolic function with retrograde delivery systems. Although retrograde delivery of cardiolegic solution, used alone or in combination with antegrade delivery, has been demonstrated to be an effective and safe technique for myocardial reservation, its clinical imortance has not been well demonstrated. In the revious small study, the immediate clinical outcome did not aear to be affected by the route of cardiolegia administration used in atients undergoing first-time myocardial revascularization [7]. The resent study was not rosectively randomized and lacks sohisticated hemodynamic and statistical evaluations, but all atients were oerated on consecutively and included all oerative categories: elective, urgent, emergent/salvage, redo, and all risk grous. Patients were registered in the STS NCSDB and comlied with the set definitions, allowing us to comare two grous of atients using univariate analysis. Also, the available reoerative redicted risk grou model of the STS NCSDB enabled us to identify high risk (redicted oerative mortality 10% and higher) for atients undergoing only coronary artery byass grafting and use univariate analysis to identify the differences between these two higher risk grous. The observed lower ejection fraction in the s-r grou should not cause clinical differences in site of statistical significance. Also, some of the reoerative variables (history of cerebrovascular accident, redo status, intraaortic balloon, and nitroglycerin dris) may or may not lay a role in the clinical outcome. Thermodilution data suggest that both routes of cardiolegia resulted in nearly identical ostoerative left and right ventricular dynamic function, confirming that retrograde cardiolegia alone did not comromise right ventricular function as originally anticiated. When the high-risk grou of atients was analyzed, the s-r grou had more atients in New York Heart Association functional class IV, had a lower ejection fraction, and required nitroglycerin dris more frequently reoeratively. The um time was significantly longer in the AR grou in site of fewer number of grafts er atient. Postoerative creatine kinase-mb levels were higher in the s-r grou but without any greater incidence of erioerative myocardial infarction. The number of atients in whom atrial fibrillation develoed was also higher in grou R. The occurrence of atrial fibrillation after oeration is one of our major concerns, because it not only created an uncomfortable and annoying situation for the atients but also resulted in a otential increase in length of stay. Since 1993 after our clinical athway had been imlemented, -blockers have been used in most of the atients beginning on the evening of the oeration, resulting in some decline in the incidence of ostoerative atrial fibrillation. The causes of atrial fibrillation and the mechanism of its develoment after cardioulmonary byass are beyond the scoe of this discussion. In summary, good clinical results can be obtained in all atients who undergo routine coronary artery byass grafting with or without valve relacement/reair using either retrograde cardiolegia alone or an antegrade/ retrograde aroach combined, regardless of the clinical status or severity index. The results aear to favor neither aroach. In the retrograde grous, atients had higher redicted oerative mortality, and the s-r subgrou had more atients in New York Heart Association functional class IV. Both R and s-r atients went through the oeration without significant oerative mortality or comlications when comared with the antegrade grous. Retrograde cardiolegia alone has been shown to be effective for myocardial rotection, but ostoerative atrial fibrillation develoed in more atients in this grou, otentially leading to a longer length of hosital stay. The antegrade/retrograde aroach offers a good immediate outcome, but this method could be cumbersome and confusing during the adjustments of the flow clams for antegrade and retrograde delivery and could be the reason for rolonged um time. From this study, it aears that retrograde cardiolegia alone rovides as good myocardial rotection and safety as the antegrade/ retrograde aroach in either routine or high-risk atients. However, this study is unable to conclude that either aroach rovides suerior myocardial rotection and safety to another, and a rosective, randomized study is encouraged for more conclusive results. We thank Patricia Janey, RN, for her research efforts. It was her dedication and commitment that heled to make this roject a success. References 1. Menasché P, Kucharski K, Mundler O, et al. Adequate reservation of right ventricular function after coronary sinus cardiolegia: a clinical study. Circulation 1989;80 (Sul 5): Eichorn EJ, Diehl JT, Konstam MA, et al. Protective effects of retrograde comared with antegrade cardiolegia on right ventricular systolic and diastolic function during coronary byass surgery. Circulation 1989;79: Gundry SR, Wang N, Bannon D, et al. Retrograde continuous warm blood cardiolegia: maintenance of myocardial homeostasis in humans. Ann Thorac Surg 1993;55: Partington MT, Acar C, Buckberg GD, et al. Studies of retrograde cardiolegia. I. Caillary blood flow distribution to myocardium sulied by oen and occluded arteries. J Thorac Cardiovasc Surg 1989;97: Buckberg GD. Udate on current techniques of myocardial rotection. Ann Thorac Surg 1995;60: Bhayana JN, Kalmbach T, Booth FVMcL, Mentzer RM Jr, Schimert G. Combined antegrade/retrograde cardiolegia for myocardial rotection: a clinical trial. J Thorac Cardiovasc Surg 1989;98: Arom KV, Emery RW. Coronary sinus cardiolegia: clinical trial with only retrograde aroach. Ann Thorac Surg 1992; 53: Ludinghausen MV. Nomenclature and distribution attern of cardiac veins in man. In: Mohl W, Faxon D, Wolner E, eds. Clinics of CSI. New York: Sringer-Verlag, 1986: Guiraudon GM, Cambell CS, McLellan DG, et al. Retrograde coronary sinus versus aortic root erfusion with cold cardiolegia: randomized study of levels of cardiac enzymes in 40 atients. Circulation 1986;74(Sul 3):

6 1624 AROM ET AL Ann Thorac Surg TWO CARDIOPLEGIA ROUTES 1997;63: Fiore AC, Naunheim KS, McBride LR, et al. Aortic valve relacement. Aortic root versus coronary sinus erfusion with blood cardiolegic solution. J Thorac Cardiovasc Surg 1992;104: Partington MT, Acar C, Buckberg GD, et al. Studies of retrograde cardiolegia. II. Advantages of antegrade/ retrograde cardiolegia to otimize distribution in jeoardized myocardium. J Thorac Cardiovasc Surg 1989;97: Shiki K, Masuda M, Yonenaga K, et al. Myocardial distribution of retrograde flow through the coronary sinus of the excised normal canine heart. Ann Thorac Surg 1986;41: Masuda M, Yonenaga K, Shiki K, et al. Myocardial rotection in coronary occlusion by retrograde cardiolegic erfusion via the coronary sinus in dogs. J Thorac Cardiovasc Surg 1986;92: Menasché P, Subayi J-B, Piwnica A. Retrograde coronary sinus cardiolegia for aortic valve oerations: a clinical reort on 500 atients. Ann Thorac Surg 1990;49: Emery RW, Arom KV. Results with retrograde delivery of cardiolegia for myocardial rotection during cardiac surgery. J Cardiovasc Surg 1993;34: Salerno TA, Houck JP, Barrozo CAM, et al. Retrograde continuous warm blood cardiolegia: a new concet in myocardial rotection. Ann Thorac Surg 1991;51: Diehl JT, Eichhorn EJ, Konstam MA, et al. Efficacy of retrograde coronary sinus cardiolegia in atients undergoing myocardial revascularization: a rosective randomized trial. Ann Thorac Surg 1988;45: Shaira N, Lemole GM, Sagna PM, et al. Antegrade and retrograde infusion of cardiolegia: assessment by thermovision. Ann Thorac Surg 1987;43: Schaer J, Walter P, Scheld H, et al. The effects of retrograde erfusion of cardiolegic solution in cardiac oerations. J Thorac Cardiovasc Surg 1985;90: Noyez L. Retrograde cardiolegia and aortic valve relacement [Letter]. J Thorac Cardiovasc Surg 1993;106: Noyez L, van Son JAM, van der Werf T, et al. Retrograde versus antegrade delivery of cardiolegic solution in myocardial revascularization. A clinical trial in atients with three-vessel coronary artery disease who underwent myocardial revascularization with extensive use of the internal mammary artery. J Thorac Cardiovasc Surg 1993;105: Haan C, Lazar HL, Bernard S, et al. Sueriority of retrograde cardiolegia after acute coronary occlusion. Ann Thorac Surg 1991;51: Gundry SR, Kirsh MM. A comarison of retrograde cardiolegia versus antegrade cardiolegia in the resence of coronary artery obstruction. Ann Thorac Surg 1984;38: Misare BD, Krukenkam IB, Lazer ZP, et al. Retrograde is suerior to antegrade continuous warm blood cardiolegia for acute cardiac ischemia. Circulation 1992;86(Sul 2): DISCUSSION DR LYNN H. HARRISON (New Orleans, LA): Doctor Arom, several years ago at this meeting you gave me a lesson on the difference between statistical significance and clinical significance. I wonder if that issue is aroriate in your aer. Although not quite statistically significant, there was a difference in the incidence of stroke between those two regimens favoring the antegrade-retrograde route. That might be exlained by a difference in core temeratures, and indeed there was a statistically significant difference in those core temeratures but robably not a clinically significant difference. What do you think about that incidence of stroke? Is that kismet or is that erhas something that should be looked at further? DR AROM: Doctor Harrison, I agree with you that there is a statistically significant difference between the core temerature for the entire grou (30.7 C versus 31.5 C; 0.01) and for the high-risk grou (29.8 C versus 30.9 C; 0.001). There were no significant differences in the incidence of ostoerative stroke among these two grous in site of more atients in the R and s-r grou suffering from stroke than the AR and s-ar grou. What does this mean? I am not sure. We know that there was a higher reoerative incidence of cerebrovascular accident in the retrograde alone grou. We also know that normothermic (37 C) cardioulmonary byass could lead to more ostoerative stroke than hyothermic heart oerations. But as you can see, there was only slightly more than 1 C difference between the R and the AR grou. DR CLINTON E. BAISDEN (Temle, TX): I enjoyed your aer very much. I had a question though. If it truly is statistically significant that atrial fibrillation develos in more atients and there is a longer length of stay in the retrograde grou, then is it really cheaer to use that method of cardiolegia delivery rather than the other? DR AROM: Doctor Baisden, the data definitely show that more atrial fibrillation develoed in the ostoerative eriod in both of the retrograde grous. Further evaluation of the data confirmed that rolonged hosital stay could increase costs. DR FREDERICK L. GROVER (Denver, CO): In your review of these data, was there any selection bias or any articular routine as to who got antegrade-retrograde versus retrograde cardiolegia only? For examle, did each of you in your grou have a certain routine, or were sicker atients identified who tended to receive one tye of cardiolegia delivery over the other? DR AROM: Doctor Grover, you are correct that some of us use retrograde cardiolegia alone and that others use a combined aroach as routine, but there was no selection at all in terms of the severity of comorbidity of the atients.