The use of intra-aortic balloon counterpulsation (IABC) to reduce left ventricular afterload and myocardial oxygen consumption is clearly indicated in patients with refractory myocardial ischemia or acute myocardial infarction complicated by cardiogenic shock.1–4 However, the ability of IABC to increase diastolic antegrade coronary blood flow through critically stenosed coronary arteries is not well substantiated.1,2,5–8 Therefore, the role of “prophylactic” IABC in hemodynamically stable patients with severe coronary artery disease undergoing surgical revascularization remains controversial.3,9–14 The purpose of this study was to evaluate the effect on mortality of prophylactic, pre-operative IABC in stable patients with severe left main coronary disease undergoing coronary artery bypass graft surgery (CABG). METHODS Data from all patients undergoing CABG or IABC at the Hahnemann University Hospital are prospectively collected in dedicated databases. We performed a post-hoc analysis on all patients entered into these databases from 1993 to 1999, who had undergone CABG for left main coronary artery stenosis >= 50%, without any pre-operative hemodynamic compromise or ongoing ischemia. The Institutional Review Board at Hahnemann University Hospital approved this protocol. Patients with congestive heart failure, cardiogenic shock, ongoing angina, previous CABG, and those requiring valve replacement were excluded. A total of 457 patients were identified retrospectively and divided into two groups. Group 1 comprised 287 patients whose primary cardiologists/cardiac surgeons chose not to deploy IABC. Group 2 comprised 170 patients who received prophylactic, pre-operative IABC. Pre-operative IABC was deployed before transfer to the operating room, usually the day before CABG. The clinical outcomes assessed were peri-operative 30-day mortality, cardiopulmonary bypass time, and post-operative length of stay. Intra-operative transesophageal echocardiography was performed in 7 patients with IABC, using a Hewlett-Packard HP Sonos 1,500 system with a 3.7–5.0 MHz transesophageal transducer. The pulsed Doppler sample volume was positioned within the lumen of the distal left main beyond the stenosis or in the left circumflex artery.15–19 Measurements of the peak diastolic flow velocity and velocity-time integral of augmented and non-augmented beats were obtained during 1:3 assist ratio. Subsequent to the analysis of the Hahnemann patient cohort, we compared the no IABC Group 1 Hahnemann patients to a larger group of 342 patients with left main disease and bypass surgery (having similar demographic characteristics) derived from the Benchmark IABC Registry.20 The Registry is an ongoing, large-scale, prospective registry established in January 1997 to track the use of IABC with more than 10,000 patients entered from over 100 hospitals. Definitions. Peripheral vascular disease was identified in the databases if the patient experienced claudication, had a revascularization procedure, or aortic aneurysm surgery. Previous myocardial infarction was identified by a history of hospital admission with an “abnormal” enzyme pattern, or an abnormal electrocardiogram with pathological Q-waves. Statistical analysis. Demographic data are expressed as means ± standard deviation (SD). Comparisons between Hahnemann Group 1 no IABC vs. Hahnemann Group 2 IABC, and Hahnemann Group 1 vs. Benchmark IABC Registry patients were performed using the difference of sample proportions. In addition, the Chi-square test, with Yates correction (when necessary), was applied. A probability value (p) of Present study. The goals of the present study were to assess the clinical outcome and changes in coronary flow in normotensive, clinically stable patients with ejection fractions above 20% in whom IABC was deployed as a prophylactic device prior to coronary bypass surgery. We focused on patients with left main disease because of the recent shift in clinical practice in many hospitals to deploy IABC in such patients.14,21 We observed strong trends toward a mortality advantage in patients with IABC. In the internal Hahnemann comparison, peripheral vascular disease was the principle determinant of survival. Nevertheless, patients with or without PVD experienced lower mortality rates if they received IABC. A large number of our peri-operative deaths, however, were the due to CVA. We did not systematically image the ascending aorta and arch or the carotid arteries. A recent analysis by Allie et al.24 in 20 patients with left ventricular ejection fractions less than 30%, significant left main obstruction, and severe internal carotid disease, who were treated with prophylactic IABC prior to sequential carotid and coronary surgery, demonstrated no deaths or strokes. IABC has also been shown to augment cerebral flow.25 To broaden the perspective beyond a single-center experience, we compared the Hahnemann no IABC group to patients from the Benchmark IABC Registry with similar coronary anatomy and clinical indications proceeding to CABG with prophylactic IABC. Again, IABC appeared beneficial, but the benefit was confined to the larger patients with a body mass index above 26.4 kg/m2. Balloon counterpulsation augments proximal coronary blood flow in non-obstructed arteries, especially in those patients with a systolic pressure less than 90 mmHg.2,7 The effect on distal coronary flow beyond obstructive stenoses, as assessed by the super-selective intracoronary flow velocity 0.018´´ Doppler guidewire (Flowire, Rancho Cordova, California), however, has been felt to be minimal.8 Our subset of 7 stable normotensive patients consistently demonstrated a significant augmentation in coronary blood flow beyond their severe left main stenoses. Study limitations. The present study was a post-hoc analysis of prospectively gathered data, and not a randomized study. The decision regarding deployment of IABC was left up to the cardiologist/cardiac surgeon team. CONCLUSION In patients who are stable, normotensive, and have reasonable or normal ventricular function, we observed a trend favoring survival with IABC. Using transesophageal echo-Doppler analysis of coronary blood flow, the present study also demonstrated that IABC augmented distal coronary flow beyond severe left main stenoses even in normotensive patients. While unadjusted mortality rates appear lower with prophylactic IABC, confounding variables such as PVD mandate a larger, prospective, randomized clinical trial in order to clarify the role of IABC in hemodynamically stable patients with left main disease.26 Acknowledgment. The Datascope Corporation, Cardiac Assist Division provided financial support for the statistical analysis.
1. Mueller H, Ayres SM, Connklin EJ, et al. The effects of intra-aortic counterpulsation on cardiac performance and metabolism in shock associated with acute myocardial infarction. J Clin Invest 1971;50:1885‚Äì1900. 2. Bregman D, Parodi EM, Edie RN, et al. Intraoperative unidirectional intra-aortic balloon pumping in the management of left ventricular power failure. J Thorac Cardiovasc Surg 1975;79:1010‚Äì1023. 3. Bolooki H, Williams W, Thurer RJ. Clinical and hemodynamic criteria for use of the intra-aortic balloon pump in patients requiring cardiac surgery. J Thorac Cardiovasc Surg 1976;72:756‚Äì768. 4. Anderson RD, Ohman EM, Holmes DR Jr., et al., for the GUSTO-I investigators. Use of intraaortic balloon counterpulsation in patients presenting with cardiogenic shock: Observations from the GUSTO-I Study. J Am Coll Cardiol 1997;30:708‚Äì715. 5. Gill CG, Wechsler AS, Newman GE, Oldham HN Jr. Augmentation and redistribution of myocardial blood flow during acute ischemia by intraaortic balloon pumping. Ann Thorac Surg 1973;16:445‚Äì453. 6. MacDonald RG, Hill JA, Feldman RL. Failure of intraaortic balloon counterpulsation to augment distal coronary perfusion pressure during percutaneous transluminal coronary angioplasty. Am J Cardiol 1987;59:359‚Äì361. 7. Kern MJ, Aguirre F, Tatineni S, et al. Enhanced coronary blood flow velocity during intraaortic balloon counterpulsation in critically ill patients. J Am Coll Cardiol 1993;21:359‚Äì368. 8. Kern MJ, Aguirre F, Bach R, et al. Augmentation of coronary blood flow by intra-aortic balloon pumping in patients after coronary angioplasty. Circulation 1993;87:500‚Äì511. 9. Gunstensen J, Goldman BS, Scully HE, et al. Evolving indications for preoperative intraaortic balloon pump assistance. Ann Thorac Surg 1976;22:535‚Äì545. 10. Voudris V, Marco J, Morice M, et al. ‚ÄúHigh-risk‚Äù percutaneous transluminal coronary angioplasty with preventive intraaortic balloon counterpulsation. Cathet Cardiovasc Diagn 1990;19:160‚Äì164. 11. Ohman EM, George BS, White CJ, et al., for the Randomized IABP Study Group. Use of aortic counterpulsation to improve sustained coronary artery patency during acute myocardial infarction: Results of a randomized trial. Circulation 1994;90:792‚Äì799. 12. Dietl CA, Berkheimer MD, Woods EL, et al. Efficacy and cost-effectiveness of preoperative IABP in patient with ejection fraction of 0.25 or less. Ann Thorac Surg 1996;62:401‚Äì409. 13. Christenson JT, Badel P, Simonet F, Schmuziger M. Preoperative intraaortic balloon pump enhances cardiac performance and improves the outcome of redo CABG. Ann Thorac Surg 1997;64:1237‚Äì1244. 14. Holman WL, Li Q, Kiefe CI, et al. Prophylactic value of preincision intra-aortic balloon pump: Analysis of a statewide experience. J Thorac Cardiovasc Surg 2000;120:1112‚Äì1119. 15. Kyo S, Matsumura M, Takamoto S, Omoto R. Transesophageal color Doppler echocardiography during mechanical assist circulation. Trans Am Soc Artif Intern Organs 1989;35:722‚Äì725. 16. Katz ES, Tunick PA, Kronzon I. Observations of coronary flow augmentation and balloon function during intraaortic balloon counterpulsation using transesophageal echocardiography. Am J Cardiol 1992;69:1635‚Äì1639. 17. Hutchison SJ, Thaker KB, Chandraratna AN. Effects of intraaortic balloon counterpulsation on flow velocity in stenotic left main coronary arteries from transesophageal echocardiography. Am J Cardiol 1994;74:1063‚Äì1065. 18. Geppert A, Frey B, Gabriel H, et al. Effects of intraaortic balloon pumping on coronary and carotid flow during percutaneous cardiopulmonary support. Ann Thorac Surg 1996;61:1539‚Äì1541. 19. Zehetbruber M, Mundigler G, Christ G, et al. Relation of hemodynamic variables to augmentation of left anterior descending coronary flow by intraaortic balloon pulsation in coronary artery disease. Am J Cardiol 1997;80:951‚Äì955. 20. Ferguson JJ, Cohen M, Freedman R, et al. The Benchmark counterpulsation outcomes registry: Results in 5,335 patients. J Am Coll Cardiol 1999;33(Suppl A):203A. 21. Torchiana DF, Hirsch G, Buckley MJ, et al. Intraaortic balloon pumping for cardiac support: Trends in practice and outcome, 1968 to 1995. J Thorac Cardiovasc Surg 1997;113:758‚Äì769. 22. Stone GW, Marsalese D, Brodie BR, et al. A prospective, randomized evaluation of prophylactic intraaortic balloon counterpulsation in high risk patients with acute myocardial infarction treated with primary angioplasty. J Am Coll Cardiol 1997;29:1459‚Äì1467. 23. Gutfinger DE, Ott RA, Miller M, et al. Aggressive preoperative use of intraaortic balloon pump in elderly patients undergoing coronary artery bypass grafting. Ann Thorac Surg 1999;67:610‚Äì613. 24. Allie DE, Lirtzman M, Malid AP, et al. Rapid-staged strategy for concomitant critical carotid and left main coronary disease with left ventricular dysfunction: IABP use. Ann Thorac Surg 1998;66:1230‚Äì1235. 25. Nussbaum ES, Sebring LA, Ganz WF, Madison MT. Intra-aortic balloon counterpulsation augments cerebral blood flow in the patient with cerebral vasospasm: A Xenon-enhanced computed tomographic study. Neurosurgery 1998;42:206‚Äì214. 26. Holman WL, Li Q, Kiefe CI, et al. Prophylactic value of pre-incision intra-aortic balloon pump: Analysis of a statewide experience. J Thorac Cardiovasc Surg 2000;120:1112‚Äì1119.