Ann Thorac Surg 1996;61:1231-1235
© 1996 The Society of Thoracic Surgeons
Original Article: Cardiovascular
Efficacy and Safety of a Percutaneous Right Ventricular Assist System
Mitsuhiro Yano, MD,
Toshio Onitsuka, MDPhD,
Koichiro Shibata, MDPhD,
Yasunori Koga, MDPhD
Second Department of Surgery, Miyazaki Medical College, Miyazaki, Japan
Accepted for publication December 29, 1995.
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Abstract
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Background. Mechanical right ventricular assistance is necessary in the management of profound right ventricular failure resistant to medical therapy. Conventional right ventricular assistance requires a thoracotomy. We developed a technique for assisting the failing right ventricle without thoracotomy.
Methods. We implanted the percutaneous right ventricular assist system in animals to test its feasibility and safety. A feasibility study was performed in a right ventricular failure model using 12 open chest dogs, and we examined the effects of the system hemodynamically. Next, the system was implanted into 6 goats and driven for 2 to 8 days.
Results. Institution of the percutaneous right ventricular assist system revealed overall hemodynamic improvement on right ventricular failure in dogs. In the goat experiment, no animal died from cannula-related complications. No damage to the intracardiac structures and no pulmonary edema were seen. Plasma free hemoglobin concentration did not exceed 10 mg/dL.
Conclusions. The percutaneous right ventricular assist system is safe and effective in the management of right ventricular failure.
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Introduction
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Mechanical right ventricular assistance combined with left-sided heart support is sometimes necessary after major cardiac operation or cardiac infarction. In addition, right ventricular failure following left ventricular assist device (LVAD) implantation bridging to heart transplantation occasionally requires mechanical right ventricular assistance. Thoracotomy is essential for conventional right ventricular assistance, for whichAu: OK? percutaneously insertable LVADs have been developed [1–4]. A safe, effective, and easily implanted right ventricular assist device, if available, would be of great benefit to this group of patients.
We developed a technique of right ventricular assistance that can be introduced percutaneously and investigated its technical feasibility and efficacy in a dog model. Next, we implanted the percutaneous right ventricular assist system (PRVAS) in 6 adult goats with normal hearts.
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Material and Methods
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Feasibility Study With Open Chest Dogs
Experiments were performed in 12 adult mongrel dogs weighing 11.0 to 20.5 kg. Each of the dogs was anesthetized with intravenous thiopental (10 mg/kg) after intramuscular premedication with ketamine (10 mg/kg) and atropine (0.02 mg/kg). They were intubated and ventilated with 5 cm H2O positive end-expiratory pressure using a volume-cycled ventilator (Newport Ventilator model E100; Newport Medical Instruments, Inc, Newport Beach, CA). Anesthesia was maintained by continuous thiopental drip (10 mg • kg-1 • h-1).
The heart was exposed through a median sternotomy and an LVAD was inserted between the left ventricle and the ascending aorta. The outflow cannula of the LVAD (inner diameter, 8 mm; length, 200 mm) was anastomosed to the ascending aorta and the inflow cannula (inner diameter, 13 mm; length, 210 mm) was inserted into the left ventricular chamber through the apex of the left ventricle after heparinization (1 mg/kg). A pulsatile pump controlled by a drive unit (Corart102, Aisin, JapanAu: city in Japan) was used for LVAD. The LVAD output was measured by an ultrasonic blood flow probe (T201, Transonic Systems. Ithaca, NY).
The PRVAS outflow cannula having an inner diameter of 3 mm and a length of 900 mm was then inserted through the femoral vein. The entire outflow cannulaAu: OK? and the Swan-Ganz catheter were inserted into the femoral vein, then the cannula was introduced into the pulmonary artery by a Swan-Ganz catheter floating out into the pulmonary artery while monitoring the pressure waveform (Fig 1
). An 18F USCIAu: manufacturer? cannula, used as the inflow cannula for the PRVAS, was inserted through the right jugular vein into the right atrium. A Sarns centrifugal pump (centrifugal pump 7850, Sarns, Ann Arbor, MI) was used for output. Right ventricular assistance flow was measured by an electromagnetic blood flow probe (MVF1200, Nihon Koden, JapanAu: city in Japan).
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Fig 1. . Technique for outflow cannula insertion into the pulmonary artery. A Swan-Ganz catheter is inserted through the outflow cannula. The catheter and the cannula are flow directed into the pulmonary artery.
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Aortic pressure was measured by a catheter-tipped micromanometer (MPC500, Miller, Houston, TX) inserted through the right femoral artery into the aortic arch. Other microtip pressure transducers (TCP2RN136F30, Tokai Rika Denki, JapanAu: city in Japan) were inserted directly to measure continuously the left ventricular, right ventricular, and pulmonary arterial pressures. Right and left atrial pressures were also measured continuously using fluid-filled catheters connected to pressure transducers (P23ID, Gould, Oxnard, CA). All data were monitored and recorded on a polygraph (EP1102S, NEC Sanei, JapanAu: city in Japan) and a recorder (Omnicorder 8M15, NEC Sanei, Japan).
Biventricular failure was induced by normothermic global cardiac ischemia that was accomplished by cross-clamping the ascending aorta, combined with electrically induced ventricular fibrillation for 30 minutes. Systemic circulation during cardiac ischemia was maintained with both ventricular assist systems. After 30 minutes of ischemia, the clamp was removed, the heart was defibrillated electrically, and the hemodynamic effects of the PRVAS were measured. The effects of the PRVAS were evaluated by measuring the hemodynamic variables described above with and without PRVAS use in the same dogs, continuously assisted by the LVAD. Right ventricular stroke work index (RVSWI) and pulmonary vascular resistance index (PVRI) were calculated by the following equations: RVSWI = (CO - PRVAS flow)(RVSP - RVEDP)/HR/BW; PVRI = (mPAP - LAP)BW/CO, where CO is cardiac output; RVSP, right ventricular systolic pressure; RVEDP, right ventricular end-diastolic pressure; HR, heart rate; BW, body weight; mPAP, mean pulmonary arterial pressure; and LAP, left atrial pressure.
All values are expressed as mean ± standard deviation. Statistical analysis was performed with the Student's t test for paired variables.
PRVAS Implantation in Awake Goats
Six female goats weighing 35.0 to 45.0 kg were intubated and anesthetized with halothane after premedication by ketamine (10 mg/kg) and atropine (0.01 mg/kg) intramuscularly. A thoracotomy was performed through the right fourth intercostal space. An ultrasonic flowmeter was placed on the ascending aorta and the internal mammary artery and vein were cannulated for pressure monitoring.
Percutaneous right ventricular assistance was instituted through the bilateral jugular vein by way of a puncture according to Seldinger's method. Fluoroscopy was used for the PRVAS insertion. The outflow cannula (Fig 2) of the PRVAS used for clinical use was made in cooperation with Togo Medikit Co, Ltd (Miyazaki, Japan). It was constructed of a polyamide resin, and had a very simple structure with an inner diameter of 4 mm, an outer diameter of 5.5 mm, and a length of 900 mm and two side holes near the tip. Assisted right ventricular flow was measured by an ultrasonic flowmeter. Cardiac failure was not induced. The chest was closed and the goats were allowed to wake up.
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Fig 2. . The outflow cannula of the percutaneous right ventricular assist system. The outflow cannula of the percutaneous right ventricular assist system is constructed of a polyamide resin. It is a thin-walled, flexible cannula, flared at its end where it connects to the pump. It has an inner diameter of 4 mm, an outer diameter of 5.5 mm, and a length of 900 mm. Near the tip of the cannula there are two side holes with diameters of 3 mm. (ID = inner diameter; OD = outer diameter.)
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Assisted right ventricular flow was restricted to approximately 50% of aortic blood flow. Heparin sodium was infused continuously to keep the activated clotting time at 150 to 200 seconds in experiments 1, 2, 3, and 4. In experiments 5 and 6, the activated clotting time was maintained at approximately 400 seconds. Hemolysis was quantified by measuring plasma free hemoglobin concentration. Goats were sacrificed after termination of the experiments. Two goats were sacrificed after 1 week. Four other goats were sacrificed after the termination of PRVAS use due to other causes. The hearts and lungs were removed and examined pathologically.
All the animals received humane care at the Experimental Animal Center of Miyazaki Medical College.
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Results
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Hemodynamic Effects of the PRVAS
All the data before and after cardiac ischemia and improvement of hemodynamic parameters after institution of PRVAS use are shown in Table 1. The cardiac ischemia protocol caused significant myocardial dysfunction, therefore an adequate cardiac output was not achieved even with LVAD. Right ventricular output was decreased and right ventricular preload was increased. Cardiac index significantly decreased from 78.7 ± 26.6 mL • min-1 •kg-1 to 53.3 ± 31.8 mL • min-1 • kg-1 (p < 0.001). Right ventricular end-diastolic pressure increased from 4.9 ± 3.5 mm Hg to 8.2 ± 4.5 mm Hg (p < 0.001).
Soon after the initiation of PRVAS use, the hemodynamic parameters improved. Right ventricular output was increased while the right ventricle was unloaded. The cardiac index increased significantly to 77.8 ± 31.7 mL • min-1 • kg-1 (p < 0.01). The RVEDP decreased to 5.9 ± 4.5 mm Hg (p < 0.01).
PRVAS Implantation in Goats
Outcomes of the experiments are presented in Table 2. It was easy to insert the PRVAS using fluoroscopy. No animals died of cannula-related complications. Centrifugal pumps came to a standstill because of thrombi in the pump heads in experiments 1 and 3. In experiment 2, the goat died of intrathoracic hemorrhage from the intercostal artery. In experiment 4, the pump was replaced without incident due to thrombi on the fourth postoperative day. In experiment 5, the cannula kinked on the fourth postoperative day because the pump and motor dropped off the back of the goat. In experiments 5 and 6, the activated clotting time was maintained at approximately 400 seconds to avoid thrombus formation. Large thrombi were not seen in the pump heads in these experiments.
Assisted right ventricular flow was maintained at approximately 50% of the aortic blood flow (Fig 3). The mean assisted flow was 1.36 ± 0.48 L/min and the mean aortic flow was 2.77 ± 0.60 L/min.
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Fig 3. . Changes in aortic blood flow and percutaneous right ventricular assist system (PRVAS) flow. The PRVAS flow was maintained at approximately 50% of ascending aortic blood flow. The ascending aortic blood flow averaged 2.77 ± 0.60 and the PRVAS flow averaged 1.36 ± 0.48 L/min. (SD = standard deviation.)
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Plasma free hemoglobin concentration was 6.8 ± 1.9 mg/dL before initiation of PRVAS use. During PRVAS use, the concentration increased gradually, but it decreased immediately after pump exchange as shown in experiment 4. In experiments 5 and 6, free hemoglobin concentration stayed less than 10 mg/dL (Fig 4).
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Fig 4. . Changes in plasma free hemoglobin concentration. Plasma free hemoglobin concentration could be kept less than 10 mg/dL as long as the thrombus in the pump was avoided. (PRVAS = percutaneous right ventricular assist system.)
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There was no macroscopic destruction of the pulmonary or tricuspid valves and the inner surface of the cardiac chambers after 1 week of PRVAS implantation (Fig 5). The valves had no ulcerations, perforations, or vegetations. Pathologic examination of the lungs revealed no pulmonary edema or intraalveolar hemorrhage (Fig 6).
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Fig 5. . Macroscopic finding of the heart in experiment 6. The inner surface of the heart was not affected by percutaneous right ventricular assist system implantation. The tricuspid and the pulmonary valves had no ulcerations, perforations, or vegetations.
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Fig 6. . Photomicrograph of the lung in experiment 6. Neither pulmonary edema nor intraalveolar hemorrhage were found in the lung. (Hematoxylin and eosin stain; x60 before 52% reduction.)
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Comment
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We describe a percutaneously introduced right ventricular assist system, which was tested in animals.
Hemodynamic data after right ventricular failure induction in dogs confirmed the increased right ventricular preload and decreased PAP, LAP, and CO. Right ventricular failure did not allow for adequate filling of LVAD and resulted in low cardiac output. The PRVAS unloaded the right ventricle as indicated by the finding that the RAP, RVEDP, and RVSWI were decreased. The PRVAS also increased the pulmonary blood flow, which in turn increased the systemic blood flow. The experiments in dogs revealed that use of the PRVAS was feasible to assist the right ventricle. Echocardiography or pulmonary arteriography, not done in this study, would provide evidence of right ventricular relaxation by the PRVAS. We would like to confirm that with more experiments.
Experiments with goats indicated that percutaneous right ventricular assistance could be carried out safely for 1 week. We anticipated complications associated with relatively long-term PRVAS use. These included pulmonary edema, mechanical damage to the cardiac wall or valves, and hemolysis. Pulmonary edema is potentially the most troublesome complication when conventional right ventricular assistance is done [5–7]. Thus, in conventional right ventricular assistance, pump flow is restricted [8]. Therefore, we restricted PRVAS flow to approximately 50% of aortic blood flow in this study. We recognized that assisted right ventricular flow would have to increase up to 80% or more of the cardiac output to maintain minimum pulmonary circulation in several cases. Decision of ideal ratio of assisted right ventricular flow to cardiac output is a difficult but important problem that requires more data.
We believed that thrombi in the centrifugal pumps were the most important cause of hemolysis that occurred in experiments 1, 2, 3, and 4. An elevation of the plasma free hemoglobin was avoided by preventing thrombus formation in the pump. In addition, an elevated free hemoglobin concentration was decreased by exchanging the pump that had become clogged with thrombus in experiment 4. To prevent hemolysis, it is necessary either to exchange the pump regularly or to keep the activated clotting time at a sufficiently high level.
Right ventricular failure sometimes becomes a critical issue after LVAD implantation [9–13]. Farrar and colleagues [9] reported on 213 patients who received LVADs at 12 different centers and found that 49 patients (23%) were candidates for biventricular support. Chow and Farrar [10] reported that the negative effects of the LVAD on the right ventricle were more pronounced in the failing heart than in the normal heart. Thus, it is apparent that there is a necessity to prepare for right ventricular assistance when an LVAD will be instituted. Right ventricular assistance without thoracotomy can be easily instituted by conventional method. A common indication for PRVAS use is for right ventricular failure after LVAD institution. It may also be used as a bridge to heart transplantation [14]. Implanting a PRVAS for treatment of solitary right ventricular failure without using an LVAD may be feasible but must be done carefully because of the need for continuous monitoring of cardiac output or left atrial pressure to avoid pulmonary edema.
The expected advantages of our PRVAS method are (1) ease of insertion and removal, (2) lower risk of bleeding and mediastinitis, and (3) lack of mechanical interaction with other intrathoracic structures. Bleeding complications from the cannulation site and mediastinitis would be decreased with the PRVAS as compared with the conventional method. The relatively high level of activated clotting time may increase the incidence of bleeding complication, however, exchanging the centrifugal pump with short period use or applying a heparin-coated pump would decrease the activated clotting time level. Mechanical interaction with coronary artery bypass graft or LVAD cannulas may be decreased. This means that there will be no device-related difficulty to close the chest, as is sometimes associated with conventional right ventricular assistance.
We conclude that PRVAS use may be an effective strategy for the treatment of acute right ventricular failure. More experience, especially with higher assistance flow, is required to establish the safety of the PRVAS and that percutaneous right ventricular assist is possible without destroying intracardiac structures or causing pulmonary edema.
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Footnotes
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Address reprint requests to Dr Yano, Second Department of Surgery, Miyazaki Medical College, 5200 Kihara, Kiyotake-cho, Miyazaki-gun, Miyazaki, 889-16 Japan.
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References
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- Phillips SJ, Zeff RH, Kongtahworn C, et al. Percutaneous cardiopulmonary bypass: application and indication for use. Ann Thorac Surg 1989;47:121–3.[Abstract/Free Full Text]
- Kyo S, Motoyama T, Miyamoto N, Noda H, Dohi Y, Omoto R. Percutaneous introduction of left atrial cannula for left heart bypass: utility of biplane transesophageal echocardiographic guidance for transseptal puncture. Artif Organs 1992;16:386–91.[Medline]
- Sasaki E, Nakatani T, Taenaka Y, et al. Easy access for a left ventricular assist system without thoracotomy. Trans Am Soc Artif Intern Organs 1991;37:M280–1.
- Downing S, Llaneras M, Georgi D, Wood DC, Savage EB, Edmunds LH. Left ventricular assistance without thoracotomy: mediastinal and transseptal approaches to the left heart. Ann Thorac Surg 1992;53:132–8.[Abstract/Free Full Text]
- Connolly MW, Lim KH, Rose DM, et al. Efficacy of right ventricular unloading during right coronary artery occlusion in an experimental model. Surgery 1986;100:143–9.[Medline]
- Peters JL, McRea JC, Fukumasu H, Kolff WJ. Extracorporeal, biventricular bypass (BVB) of the natural heart. Trans Am Soc Artif Intern Organs 1977;23:506–10.[Medline]
- Toporoff B, Marini CP, Grubbs, Jr. PE, Berrizbeitia LD, et al. Pulmonary complications of a roller pump right ventricular assist device. J Surg Res 1988;45:21–7.[Medline]
- Dembitsky WP, Daily PO, Raney AA, Moores WY, Joyo CI. Temporary extracorporeal support of the right ventricle. J Thorac Cardiovasc Surg 1986;91:518–25.[Abstract]
- Farrar DJ, Compton PG, Hershon JJ, Fonger JD, Hill JD. Right heart interaction with the mechanically assisted left heart. World J Surg 1985;9:89–102.[Medline]
- Chow E, Farrar DJ. Right heart function during prosthetic left ventricular assistance in a porcine model of congestive heart failure. J Thorac Cardiovasc Surg 1992;104:569–78.[Abstract]
- Farrar DJ, Chow E, Compton PG, Foppiano L, Woodard J, Hill JD. Effects of acute right ventricular ischemia on ventricular interactions during prosthetic left ventricular support. J Thorac Cardiovasc Surg 1991;102:588–95.[Abstract]
- Sato N, Mohri H, Miura M, Watanabe T, Nitta S, Sato S. Right ventricular failure during clinical use of a left ventricular assist device. Trans Am Soc Artif Intern Organs 1989;35:550–2.
- Farrar DJ, Hill JD, Gray LA Jr, Galbraith TA, Chow E, Hershon JJ. Successful biventricular circulatory support as a bridge to cardiac transplantation during prolonged ventricular fibrillation and asystole. Circulation 1989;80(Suppl 3):147–51.
- Bolman RM III, Cox JL, Marshall WM, et al. Circulatory support with a centrifugal pump as a bridge to cardiac transplantation. Ann Thorac Surg 1989;47:108–12.[Abstract/Free Full Text]
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Abstract
Introduction
