Asian Cardiovasc Thorac Ann 2002;10:155-158
© 2002 Asia Publishing EXchange Pte Ltd
Right Heart Assist During Beating Bypass for Severe Left Ventricular Dysfunction
Goro Matsumiya, MD,
Shigeaki Ohtake, MD,
Koji Kagisaki, MD,
Toshiki Takahashi, MD,
Yoshiki Sawa, MD,
Hikaru Matsuda, MD
|
Division of Cardiovascular Surgery Department of Surgery Osaka University Graduate School of Medicine Osaka, Japan
|
|
|
Goro Matsumiya, MD Tel: 81 6 6879 3154 Fax: 81 6 6879 3159 email: matsumg{at}surg1.med.osaka-u.ac.jp
|
 |
ABSTRACT
|
|---|
Three patients with triple-vessel disease and severe left ventricular dysfunction underwent successful revascularization on a beating heart, using a right ventricular assist system. Heparin-coated circuits with a centrifugal pump provided 2.5 to 3.5 L•min-1 of flow to maintain good hemodynamics and enable easy access to the posterior vessels during vertical displacement of the heart.
|
INTRODUCTION
|
|---|
Patients with severe left ventricular (LV) dysfunction have significantly increased risks of perioperative mortality and morbidity when undergoing conventional coronary artery bypass grafting (CABG).1 Although the indications for off-pump coronary artery bypass (OPCAB) have widened, it is generally precluded by severe dys-function or enlargement of the left ventricle, because of the risk of circulatory instability and difficulty in reaching the posterior vessels.2 Recent studies demonstrated that compression of the right ventricle plays a major role in hypotension and low cardiac output during OPCAB.3,4 Right heart assist has been shown in animal studies to be an effective modality for reversing the circulatory changes induced by displacement of the heart.3
|
CASE REPORTS
|
|---|
Three patients with severe LV dysfunction and dilatation underwent beating heart CABG with the support of a right ventricular assist system (RVAS). Details of each case are summarized in Table 1
. All 3 patients had severe triple-vessel disease and heart failure. None was dependent on inotropics or circulatory support. Left ventriculograms demonstrated severe LV dilatation and poor systolic function with LV ejection fractions of less than 35%. Surgery was performed through a median sternotomy. After all grafts were harvested, 1.5 mg•kg-1 of heparin was administered. Activated clotting time was maintained above 250 seconds. To facilitate exposure of the circumflex area, the right pleural space was opened widely, and deep pericardial retraction sutures were placed as described previously.2 The RVAS was constructed with heparincoated circuits and a centrifugal pump (Terumo, Inc., Tokyo, Japan). A soft reservoir was included in the system to enable quick and easy priming outside the operative field (Figure 1). No additional heparin was given before initiating RVAS support. In all patients, continuous infusion of dopamine (3 to 5 µg•kg-1•min-1) was started before undertaking anastomosis. After anastomosis to the left anterior descending artery, heparin-coated cannulas were introduced into the right atrial appendage for drainage and into the main pulmonary trunk for return. The reservoir was cut off on the operating table, and the RVAS system was connected to the cannulas. The heart was displaced vertically to approach the posterior or inferior vessels. After observation of the circulatory indices for a few minutes, right ventricular support was initiated and the flow was gradually increased while monitoring pulmonary artery pressure. On completion of distal anastomoses in the circumflex and right coronary artery areas, RVAS support was terminated. Coronary anastomoses were performed using the Octopus 2 stabilization system (Medtronic Inc., Minneapolis, MN, USA). Hemodynamic changes during the operation are summarized in Figure 2. No significant changes in the circulatory indices were observed during left anterior descending artery anasto-mosis. There was a significant decrease of systemic blood pressure and cardiac output in all cases during tilting of the heart before initiating RVAS support; these indices were well maintained during RVAS support. Central venous pressure was elevated during tilting, and decreased promptly with RVAS support. None of the patients had a significant elevation of pulmonary artery pressure. Their postoperative courses were uneventful, and they were extubated within 4 hours. The maximum levels of plasma creatine kinase-MB were between 3 and 15 U•L-1 (normal < 6.4 U•L-1). Postoperative cardiac catheterization was performed at a mean of 16 days after the operation. Coronary angiograms demonstrated patency of all grafts, and left ventriculograms showed improved LV volume and contractility.
View larger version (136K):
[in this window]
[in a new window]
|
Figure 1. Temporary right ventricular assist system with a centrifugal pump. Inflow and outflow tubes are connected to a soft reservoir for priming; this is cut off on the operating table, and the tubes are connected to heparin-coated cannulas inserted into the right atrium and pulmonary artery.
|
|
View larger version (20K):
[in this window]
[in a new window]
|
Figure 2. Changes in circulatory indices at various time points during the operation. T1 = immediately after the sternotomy, T2 = during stabilization with dopamine, T3 = heart slightly elevated during left anterior descending artery anastomosis, T4 = heart in vertical position for anastomosis in the circumflex area before starting right ventricular assist system (RVAS) support, T5 = heart tilted vertically during RVAS support.
|
|
|
DISCUSSION
|
|---|
Surgical myocardial revascularization has been shown to improve the long-term prognosis of patients with coronary artery disease and severe LV dysfunction, at the expense of higher operative risks.1 As the global ischemia induced by cardioplegia leads to substantial damage to the dysfunctional myocardium, beating heart operations have theoretical advantages over conventional CABG. Recently, a lower incidence of perioperative myocardial infarction, cardiac enzyme release, and need for circulatory support have been demonstrated in OPCAB compared to con-ventional CABG.5 However, concerns about hemo-dynamic instability have precluded wide acceptance of OPCAB for patients with severe LV dysfunction.6
The cause of the hemodynamic changes during vertical displacement of the heart has been investigated both experimentally and clinically.3,4 Gründeman and colleagues3 demonstrated that right ventricular com-pression caused a decrease in volume and an elevation of end-diastolic pressure during tilting of pig hearts. More importantly, they showed that a RVAS normalized stroke volume and arterial pressure by increasing LV preload, although left heart bypass failed to restore systemic circulation.3 The clinical findings of Mathison and colleagues4 were mostly consistent with this experimental work, but they observed that not only the right ventricle but also the left ventricle had disturbed diastolic filling due to compression. Our experience demonstrated that a RVAS can reverse the decrease in systemic blood pressure and cardiac output in patients with severe LV dysfunction. Flow through the RVAS should be controlled according to LV function. We gradually increased the flow to obtain adequate cardiac output and systemic blood pressure without increasing pulmonary artery pressure. In these three cases, flow of 2.5 to 3.5 L•min-1 was sufficient. Optimal deployment of the RVAS is a matter for future investigations.
Beating heart CABG with conventional cardiopulmonary bypass (CPB) and LV venting is another useful option for patients with severe LV dysfunction.7 We consider that the RVAS has several potential advantages over CPB. Elimination of aortic cannulation may decrease the risk of a thromboembolic event that is the major factor in an adverse cerebral outcome after CABG. Brain damage can also be caused by nonpulsatile low pressure perfusion during CPB in patients with significant stenosis in the cerebral arteries. The RVAS maintains adequate cardiac output as well as pulsatile arterial pressure. Elimination of CPB has been shown to reduce the elevation of inflammatory cytokines and complement activation during CABG.8 However, there are currently no data regarding the difference in inflammatory reactions with conventional CPB and a RVAS. The elimination of an oxygenator by the RVAS technique reduces blood cell contact with artificial membranes and theoretically decreases the activation of the inflammatory response. Heparin-coating of all artificial surfaces in the RVAS may further prevent the inflammatory response and consumption of coagula-tion factors. The benefits of the RVAS over conventional CPB or a totally off-pump procedure should be further investigated clinically. A prospective randomized study is warranted to identify the most appropriate method of revascularization in patients with severe LV dysfunction.
|
REFERENCES
|
|---|
-
Mickleborough LL, Carson S, Tamariz M, Ivanov J. Results of revascularization in patients with severe left ventricular dysfunction. J Thorac Cardiovasc Surg
2000;119:550–7.[Abstract/Free Full Text]
-
Calafiore AM, Di Giammarco G, Teodori G, Mazzei V, Vitolla G. Recent advances in multivessel coronary grafting without cardiopulmonary bypass. Heart Surg Forum
1998;1:20–5.[Medline]
-
Gründeman PF, Borst C, Verlaan CWJ, Meijburg H, Mouës CM, Jansen EWL. Exposure of circumflex branches in the tilted, beating porcine heart: echocardiographic evidence of right ventricular deformation and the effect of right or left heart bypass. J Thorac Cardiovasc Surg
1999;118: 316–23.[Abstract/Free Full Text]
-
Mathison M, Edgerton JR, Horswell JL, Akin JJ, Mack MJ. Analysis of hemodynamic changes during beating heart surgical procedures. Ann Thorac Surg
2000;70: 1355–60.[Abstract/Free Full Text]
-
Ascione R, Lloyd CT, Gomes WJ, Caputo M, Bryan AJ, Angelini GD. Beating versus arrested heart revascularization: evaluation of myocardial function in a prospective randomized study. Eur J Cardio-thoracic Surg
1999;15:685–90.
-
Arom KV, Flavin TF, Emery RW, Kshettry VR, Petersen RJ, Janey PA. Is low ejection fraction safe for off-pump coronary bypass operation? Ann Thorac Surg
2000;70: 1021–5.[Abstract/Free Full Text]
-
Antunes PE, Ferrao de Oliveira J, Antunes MJ. Non-cardioplegic coronary surgery in patients with severe left ventricular dysfunction. Eur J Cardio-thorac Surg
1999; 16:331–6.[Abstract]
-
Wan S, Izzat MB, Lee TW, Wan IYP, Tang NLS, Yim APC. Avoiding cardiopulmonary bypass in multivessel CABG reduces cytokine response and myocardial injury. Ann Thorac Surg
1999;68:52–6.[Abstract/Free Full Text]
TOP
ABSTRACT
INTRODUCTION
