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Ann Thorac Surg 2000;70:1083-1085
© 2000 The Society of Thoracic Surgeons

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Supplement: cardiothoracic techniques & technologies

Right heart circulatory support facilitates coronary artery bypass without cardiopulmonary bypass

^a Cardiopulmonary Research Science and Technology Institute, Dallas, Texas, USA
^b Escola Paulista de Medicina, Sao Paulo, Brazil
^c Instituto Do Coracao, Sao Paulo, Brazil
^d University Hospital Grosshadern, Munich, Germany
^e St. Joseph Hospital, Atlanta, Georgia, USA
^f McGill University, Montreal, Quebec, Canada

Address reprint requests to Dr Mathison, MCVI Research & Outcomes, 8900 N Kendall Dr, Miami, FL 33176
e-mail: mnmathison{at}aol.com

Presented at the Sixth Annual Cardiothoracic Techniques and Technologies Meeting 2000, Ft Lauderdale, FL, Jan 27–29, 2000.

	Abstract

Top Abstract Introduction Material and methods Results Comment References

 
Background. Revascularization of the posterior wall often causes hemodynamic instability in beating heart coronary artery bypass (CAB). Our previous clinical studies have shown that tilting the heart primarily alters right-heart hemodynamics. The purpose of this study was to evaluate right-heart support in clinical cases.

Methods. Seventeen patients underwent beating heart CAB with right-heart support. The right-heart support system (A-Med Systems, West Sacramento, CA) consisted of a coaxial cannula placed through the right atrium and the tip of the cannula positioned in main pulmonary artery. Blood was removed from the right atrium and returned to the main pulmonary artery.

Results. Elective beating heart CAB was accomplished successfully in 17 patients with right-heart support. Anastomoses performed were left anterior descending coronary artery (11), diagonal (3), circumflex (5), obtuse marginal artery (11), and right coronary artery (10). Right-heart support between 1 and 3 L/min improved hemodynamics especially in the circumflex position. No device-related patient incidents occurred, nor were there incidents of infection or air embolism. All 17 patients were discharged to their homes.

Conclusions. The right-heart support system was safe without complications. Exposure of the posterior wall was possible in all cases without hemodynamic compromise.

	Introduction

Top Abstract Introduction Material and methods Results Comment References

 
Beating heart coronary artery bypass grafting (CABG) is increasingly being performed worldwide, and in our hospital 64.8% of CABG cases were performed without cardiopulmonary bypass during 1999 (compared with 23% in 1998).

The beating heart approach has several advantages. Among them are the absence of proteolytic and inflammatory system activation, no immune system depression, and no consumption of clotting factors and platelets, all of which occur during standard cardiopulmonary bypass.

However, with this method, there is at times acute depression of systemic pressure when a better view for the anastomosis is sought. This decrease in systemic pressure occurs especially when the heart is displaced to gain access to the obtuse marginal artery (OM) and posterior descending artery. Although the decrease is usually temporary, it can adversely effect brain circulation and renal function. Yet efforts to avoid the drop in pressure result in an inadequate posterior view, and thus a superior surgical technique is required.

Previously we investigated the cause of hemodynamic changes during the displacement of the heart and found that even left anterior descending coronary artery (LAD) positioning causes elevation in right atrial pressure (RAP) and right ventricular end-diastolic pressure (RVEDP). Moreover, during OM positioning, RAP, RVEDP, left atrial pressure (LAP), and left ventricular end-diastolic pressure are all elevated, with RAP and RVEDP being greater than LAP and left ventricular end-diastolic pressure. From those results and from transesophageal echocardiography, we concluded that the main cause of hemodynamic instability during beating heart CABG is the disturbance of diastolic filling due to direct ventricular compression. Furthermore, when the left ventricle is compressed for LAD or OM, the right ventricle is compressed as well, and even more so because its wall is thinner and is pressed against the pericardial cradle.

From these conclusions, we suspected that a right-heart support could yield more stable hemodynamics. Gründerman and colleagues [1] reported that, in animal trials, exposure of circumflex branches caused right ventricular deformation and that right-heart bypass normalized stroke volume and mean arterial pressure (MAP) by increasing left ventricular preload; but, in contrast, left-heart bypass failed to restore systemic circulation.

The purpose of this study was to evaluate the feasibility of right-heart support when used in patients undergoing beating heart CABG.

	Material and methods

Top Abstract Introduction Material and methods Results Comment References

 
Seventeen patients underwent beating heart CABG with right-heart support. The operations were performed by 5 surgeons at four clinical centers (E.B., Escola Paulista de Medicina, Sao Paulo, Brazil; A.J. and F.J., Instituto Do Coracao, Sao Paulo, Brazil; Leonardo Lima, MD, PhD, Sta Lucia Hospital, Achieta Hospital, Brasilia, Brazil; and H.R., University Hospital Grosshadern, Munich, Germany). The patients were candidates for beating heart CABG, in which one of the target vessels was on the posterior or distal right side of the heart (OM, circumflex, distal RCA, or posterior descending artery). However, patients who had electric instability or a hypertrophic left ventricle were excluded. Patient demographic data are shown in Table 1. Four patients had preoperatively unstable angina. Informed consent was obtained if it was required by a national or institutional review committee.

View larger version (167K): [in this window] [in a new window]   Fig 1. The coaxial cannula is positioned in the heart. It is inserted through the right atrium, and the tip of the cannula is positioned in main pulmonary artery.

View larger version (100K): [in this window] [in a new window]   Fig 2. The right heart support system. From the controller, counterclockwise: motor, pump with syringe, flow meter, and coaxial cannula.

	Results

Top Abstract Introduction Material and methods Results Comment References

 
A total of 40 anastomoses were performed, with an average of 2.4 coronary anastomoses per patient. Anastomoses were performed in the LAD (11), diagonal (3), circumflex (5), OM (11), and RCA (10). Of these, data collection was possible in every instance except three (one each for LAD, diagonal, and circumflex positionings).

The average pump time for the anastomosis was 33.4 minutes (range 19 to 50 minutes). The priming volume was less than 50 mL. We did not measure free plasma hemoglobin; however, there was no evidence of hemolysis.

Hemodynamics
Table 2 shows that the average of the flow and the average of the best MAP for each positioning. The circumflex positioning required the highest flow, and even then the MAP was less than those of the other positionings. On the other hand, the flow that yielded the best systemic pressure for LAD was less than 2 L/min. The pump support was most effective for RCA.

	Comment

Top Abstract Introduction Material and methods Results Comment References

 
From our previous studies, we hypothesized that the right-heart support would yield more stable hemodynamics during beating heart CABG, especially during the anastomosis in the posterior of the heart. This initial clinical study confirmed our previous experience. This right-heart support system enabled stable hemodynamics during extreme posterior exposure. We sometimes felt that stable hemodynamics would not be possible without this support.

This clinical evaluation suggests that right-heart support may be a safer way of performing beating heart CABG. However, because there were only 17 cases, more study is required to reach a definite conclusion. Although we think that right-heart support is the most logical way to achieve hemodynamic stability, there are other considerations. For example, both Trendelenburg positioning and volume loading, which we routinely use during beating heart CABG, frequently restore systemic pressure. Failing these measures, an inotropic agent can be given, although stabilization is somehow more problematic with the hyperdynamic effect of inotropic support. In these instances, we are not certain that right-heart support is really more beneficial than an effective inotropic agent or a vasodilating agent. However, in cases in which low pressure persists despite administering the agent, we believe right-heart support is effective.

Two reports of ventricular assist devices for beating heart CABG [2, 3] provide additional support for our view. In both studies a left ventricular assist device was used. Waldenberger and coworkers [2] reported that the pump flow was usually sufficient, except in cases in which attempts were made to reach the circumflex area. From this finding we inferred that the left ventricular assist is not useful for obtaining better hemodynamics during circumflex anastomoses. Lönn and coworkers [3] showed that the left ventricular assist was most effective for patients who have impaired left ventricular function or acute ongoing ischemia. These reports suggest that left ventricular assist is effective only in special cases such as left ventricular failure. Although they studied healthy animals, Gründeman and coworkers [1] reported that right-heart bypass was effective for normalizing hemodynamics during exposure of circumflex, and left-heart bypass failed to restore systemic circulation.

The centrifugal pump system was intuitive to set up, easy to use, and used low prime volume. The coaxial cannula could be inserted readily on the first attempt in all cases.

In this study, we observed that higher pump flow did not always yield optimum hemodynamics, especially for the LAD positioning. In most cases, the flow that gave optimal pressure was about 2 L/min. When flow increased above 2 L/min, we sometimes observed that the right atrium collapsed, and pulmonary arterial or left atrial pressure increased while systemic pressure decreased. There is a possibility of pulmonary edema if the patient has left ventricular failure and too much flow results from the right side. Even if the left ventricular function of the patient is nearly normal, we should be alert to this complication. This is because our previous study showed that the displacement of the heart also caused a disturbance in left ventricular diastolic filling, even though right ventricular filling was more severe. Therefore, it is important to study more cases to identify the critical factors that result in optimal flow.

We conclude that this right-heart support system in beating heart CABG is a safe and feasible method, and that its introduction may enable anastomosis in more remote posterior areas under greater hemodynamic stability.

	References

Top Abstract Introduction Material and methods Results Comment References

 

1. Gründeman P.F., Borst C., Verlaan C.W.J., Meijburg H., Mouës C.M., Janses E.W. Exposure of circumflex branches in the tilted, beating porcine heart. J Thorac Cardiovasc Surg 1999;118:316-323.[Abstract/Free Full Text]
2. Waldenberger F.R., Haisjackl M., Holinski S., Lengsfeld M., Konertz W. Centrifugal pumps as left ventricular assist for coronary revascularization on a beating heart. Artif Organs 1998;22:698-702.[Medline]
3. Lönn U., Peterzén B., Carnstam B., Casimir-Ahn H. Beating heart coronary surgery supported by an axial blood flow pump. Ann Thorac Surg 1999;67:99-104.[Abstract/Free Full Text]

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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): Enio Buffolo Fabio B. Jatene Hermann Reichenspurner Robert G. Matheny Hani Shennib Michael J. Mack Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mathison, M. Articles by Mack, M. J. Search for Related Content PubMed PubMed Citation Articles by Mathison, M. Articles by Mack, M. J.