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CTSNet classification: 23.1, 25

My coworkers and I appreciate Puelher and colleagues' comments, and we are pleased that they agree with the conclusions of our study.¹ During recent years, there has been increasing interest in the use of miniaturized extracorporeal circulation (MECC), with good outcomes reported. Off-pump coronary artery bypass grafting (CABG) has had a dramatic increase during recent years because of several advantages relative to standard CABG with extracorporeal circulation (ECC) in terms of reduced in-hospital mortality and morbidity, reduced myocardial damage, and better protection of renal and pulmonary function. Many surgeons recognize some limitations of off-pump CABG, however, such as incomplete myocardial revascularization², ³ repeated revascularization,⁴ and higher hospital costs.⁵

We think that a primary objective during routine clinical activity is improvement of the technique of ECC and the biocompatibility of the tubing circuit to minimize systemic, cardiac inflammatory, and neurologic damage. ECC has improved through the years, and the constant improvements in results during the last 50 years are also due to the different ECC techniques that were developed during this long period. At many institutions, off-pump CABG represents about 20% to 30% of cardiac surgical procedures. The remainder of the operations are performed with ECC. We, therefore, believe that further improvement of ECC could improve overall results. In fact, according to our results¹ and the results of Puelher and colleagues, with the MECC is possible to perform a complete myocardial revascularization with the same systemic, cardiac, and clinic results observed with off-pump CABG. Moreover, we think that this system could be safely extended to other, more complex cardiac operations, such as the Bentall operation, aortic valve replacement, ascending aortic replacement, and mitral valve surgery.

Recently, we used the MECC in the cases of 2 patients with a large thrombus of the inferior vena cava as a complication of a left renal tumor. Urologists referred the patients to us, and they preferred to perform the operation during a period of circulatory arrest. We decide to use the MECC for both patients, with the aim of reducing the bleeding. Both cooling and rewarming phases were done with the MECC. Some minutes before the start of arrest (body temperature 20°C), the activated clotting time (ACT) was increased to 480 seconds, and the blood was drained from a different cardiotomy added to the circuit. We observed that blood loss and hemostasis were easy to manage in both patients with 2 large surgical incisions, in the chest and abdomen. Both patients were discharged alive.

Maintaining the ACT around 200 to 300 seconds during the MECC procedure is one of the keys of the system. We have usually used the same ACT target reported by Puehler and colleagues, which is similar to the ACT of our patients operated on off-pump and is statistically lower than that our patients operated on with ECC. Moreover, in an ongoing prospective randomized trial, we found that patients operated on with standard ECC had more postoperative bleeding and need for more red blood cell transfusions than did those in MECC and off-pump CABG groups.

The concept of a miniaturized system means less biologic and metabolic invasiveness, or in other words, as Puehler and colleagues intend, less hemodilution, better renal and pulmonary preservation, less coagulative disorder, and less inflammatory response. Last but not least, in an era in which coronary surgery on high-risk patients is increasing and many surgeons are afraid to use standard ECC, complete myocardial revascularization with the MECC could be a valid option to achieve good clinical outcome.

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References 

1. Formica F, Broccolo F, Martino A, Sciucchetti J, Giordano V, Avalli L, et al. Myocardial revascularization with miniaturized extracorporeal circulation versus off pump: Evaluation of systemic and myocardial inflammatory response in a prospective randomized study. J Thorac Cardiovasc Surg. 2009;137:1206–1212
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2. Puehler T, Haneya A, Philipp A, Wiebe K, Keyser A, Rupprecht L, et al. Minimal extracorporeal circulation: an alternative for on-pump and off-pump coronary revascularization. Ann Thorac Surg. 2009;87:766–772
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3. Mizutani S, Matsuura A, Miyahara K, Eda T, Kawamura A, Yoshioka T, et al. On-pump beating-heart coronary artery bypass: a propensity matched analysis. Ann Thorac Surg. 2007;83:1368–1373
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4. Williams ML, Muhlbaier LH, Schroder JN, Hata JA, Peterson ED, Smith PK, et al. Risk-adjusted short- and long-term outcomes for on-pump versus off-pump coronary artery bypass surgery. Circulation. 2005;112:I366–I370
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5. Chu D, Bakaeen FG, Dao TK, Lemaire SA, Coselli JS, Huh J. On-pump versus off-pump coronary artery bypass grafting in a cohort of 63,000 patients. Ann Thorac Surg. 2009;87:1820–1826
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