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Ann Thorac Surg 1997;64:1380
© 1997 The Society of Thoracic Surgeons
DR DUKE E. CAMERON (Baltimore, MD): Could you tell us a little more about the device itself?
DR SHUM-TIM: This device is made in Germany, where they have already used it in both adult and pediatric populations.
It is constructed of polyurethane to increase its biocompatibility. It has been extensively studied with respect to the design both in vivo and in vitro to optimize its flow characteristics, biocompatibility, and durability.
It is a user-friendly device as far as our experience in the laboratory. We have not used it clinically yet, but I do not think there is any pulsatile device available for the pediatric population in the United States.
DR CAMERON: But what is the range in stroke volume?
DR SHUM-TIM: They have different sizes that are 10, 25, 60, and 80 mL available in the left ventricular side. With respect to the RVAD, there's a 10% reduction for each corresponding volume.
DR EDWARD A. PASCOE (Winnipeg, Manitoba, Canada): The pulsatile nature of the support is intriguing in view of the suggested potential for brain protection with pulsatile flow in clinical open heart surgery. In this experimental model, do you have any data to suggest whether this assist device would have been any more or less supportive had it been a centrifugal pump with nonpulsatile flow?
DR SHUM-TIM: Well, clearly this study was not aimed to address this issue. It's a very controversial issue with respect to pulsatile versus nonpulsatile support.
Clinical reports have shown that nonpulsatile VADs have been effective and resulted in very good outcome. There are some subtle physiologic benefits demonstrated by experimental studies, however, using pulsatile support. This is especially true when prolonged support is used. As a matter of fact, we are trying to establish a long-term model using this system as an LVAD support to try to resolve some of these issues.
DR CAMERON: Can the device be gated to the electrocardiogram so that it could counter-pulse?
DR SHUM-TIM: Yes. That is right. Each of these consoles can run two devices simultaneously and independently. They could be run either synchronously or asynchronously with the electrocardiogram.
DR CAMERON: One of the concerns I have with the model is that it induces severe tricuspid regurgitation, which prevents distention of the ventricle, which is usually one of the compounding problems of ventricular support.
DR SHUM-TIM: Here, we were aiming to create a fatal right ventricular failure model. We have achieved this by surgically inducing severe tricuspid regurgitation and, effectively, a common chamber between the right ventricle and right atrium. Our results have shown that the right atrial, and therefore, the right ventricular pressure were actually very well decompressed by the current device. This demonstrated its ability to potentially prevent ventricular distention in the absence of aortic regurgitation. But again, it is not a real clinical situation. In most of the clinical situations, you do not have a wide-open tricuspid regurgitation like that. Your point is, however, very well taken.
DR AKIF ÜNDAR (San Antonio, TX): I just want to make a couple of comments about pulsatile flow. Although controversy still exists, pulsatile flow has many advantages over nonpulsatile perfusion. This has been clearly proven in humans and animals by several investigators. Doctor John Murkin has clearly shown that the use of pulsatile perfusion was related to significantly fewer complications and deaths compared with nonpulsatile perfusion in 316 patients. In contrast, there have been several articles in the literature showing no difference between both types of perfusion. However, the investigators who are proponents of nonpulsatile have never shown that the use of nonpulsatile perfusion has any benefits over pulsatile flow. They have only noted that they could not find any differences between pulsatile and nonpulsatile flow.
What is pulsatile flow? Showing a pulse pressure more than 20 mm Hg is not enough. Investigators should agree on common criteria for pulsatile flow, and then comparisons using these criteria will make more sense for different institutions' results. We believe that pulsatile flow must be physiologic. In addition to the pulse pressure, ejection time, stroke volume, and dp/dt should be mentioned in the publications. Unfortunately, most of the pulsatile pumps currently available do not produce physiologic waveforms.
Related Article
Ann. Thorac. Surg. 1997 64: 1374-1380.
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