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an intracorporeal (abdominal) left ventricular assist device PDF

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AN INTRACORPOREAL (ABDOMINAL) LEFT VENTRICULAR ASSIST DEVICE [ALVAD], XXX: CLINICAL READINESS AND INITIAL TRIALS IN MAN John C. Norman, M.D. ABSTRACT The purpose of this report is to present documenting evidence of the clinical readiness of an abdominal left ventricular assist device (ALVAD) according to NHLI criteria,t and the initiation of clinical trials of this device in otherwise irretrievable adult post-cardiotomy patients at the Texas Heart Institute of St. Luke's Episcopal and Texas Children's Hospitals. The ALVAD system has been developed, modified, and improved under NHLI auspices over the last eight years,:t with annual reviews. Over 20,000 hours of in-vivo testing in the calf have been accomplished in our laboratories. The current clinical trials underwent two federal reviews (May 22, 1973 and October 17, 1974) and were the topic of an Ad Hoc Workshop at NBU on October 28, 1973VU More recently, a consecutive series of 26 bovine ALVAD implantations were undertaken; acute and chronic hemodynamic effectiveness with maintenance or augmentation of the systemic circulation during profound ventricular unloading without undue blood trauma, intra- or extra-prosthetic thrombosis, or sepsis was demonstrated; no biomaterials problems were encountered. In-vivo reliability and durability, histologic and pathologic results were detailed, summarized, and submitted to NHLI. Patient acceptability surveys and geometric and volumetric human con- figuration studies were analyzed. Categorizations of the patients at risk in our institutions and the needs for such a device were documented. The periods of intended use (two weeks-one month), weaning procedures, and the possibility of pump dependence have been discussed. The legal, moral, ethical and informed consent issues were addressed. Clinical protocols (anesthesia, surgical, cardiologic, hematologic, engineering, computerized data-acquisition, follow-up) and cost analyses were developed. The device has now been used in four terminal patients since December, 1975; all sub- sequently succumbed, but their circulations were temporarily supported during total left ventricular unloading for periods up to eight hours. Con- tinued systematic, controlled clinical investigations of this nature are war- ranted. A comprehensive listing of pertinent references is included. tNIH Guide for Grants and Contracts, U.S. Dept. HEW 3:11, August 7, 1974. ttIn conjunction with Thermo Electron R & D Center, Waltham, Mass. tttThe Left Ventricular Assist Device: Assistance to the Failing Circulation, DHEW Publication No (NIH) 75-626. U. S. Govt. Printing Office. From the Cardiovascular Surgical Research Laboratories and Section of Surgery, the Texas Heart Institute of St. Luke's Episcopal and Texas Children's Hospitals, Texas Medical Center, Houston, Texas. Supported in part by U.S.P.H.S. Contract NOI-HL-73-2946, The John & Mary Markle Foundation, The Kelsey &LearyFoundation, The SidW. Richardson Foundation and TheMary A.FraleyFund. Address for reprints: John C. Norman, M.D., Cardiovascular Surgical Research Laboratories, the Texas Heart Institute, P.O. Box 20269, Houston, Texas 77025. Cardiovascular Diseases, Bulletin oftheTexas HeartInstitute,Vol. 3, Number 3, 1976 249 ADDENDUM: Since this report was submitted, this intracorporeal partial artificial heart (ALVAD) was utilized in a fifth patient, a 44-year-old female. Her pre-operative diagnosis was coronary artery occlusive disease involving three vessels, and she underwent a double reversed saphenous vein aorto-coronary bypass procedure to the right and left anterior de- scending coronary arteries with endarterectomy of the latter. Following the procedure, the patient could not be weaned from cardiopulmonary by- pass, and exhibited no ventricular ejection with intermittent asystole, elec- tromechanical dissociation and episodes of persistent ventricular fibrilla- tion. Because of her terminal condition, the ALVAD was implanted and ventricular function returned over the next six days during total left ven- tricular unloading. On the fifth to sixth postoperative days, the patient was weaned from ALVAD support to intra-aortic balloon pumping (IABP). The ALVAD was removed on the sixth postoperative day without incident. Oliguria progressing to anuria beginning on the first post-ALVAD im- plant day required multiple hemodialyses. Renal failure continued to be a problem and was the ultimate cause of the patient's death 12 days after implantation and seven days after weaning from ALVAD to IABP on the 12th postoperative day. The details of this first hemodynamically successful use of this intracorporeal left ventricular assist device have been reported to the Artificial Heart Program Office.t,tt,ttt INTRODUCTION The Cardiovascular Surgical Research Laboratories of the Texas Heart Institute of St. Luke's Episcopal and Texas Children's Hospitals in Houston were conceived, designed, and built in 1970-71 with NHLI collaboration for the specific purposes of testing and evaluating left ventricular assist devices in the calf, with an ultimate goal of bringing these devices to orderly and systematic clinical trials in man. Over the last eight years, a goal-oriented approach involving planning, problem identification and solving has evolved during a continued close collaboration with our engineering colleagues. Our first proposal for ALVAD clinical trials (NO TE 2374-200), in re- sponse to RFP NHLI MADP-72 (Clinical Evaluation of Temporary Left Ventricular Assist Pumping) was submitted to NHLI on April 13, 1972. The trials were not subsequently approved. A second proposal for clinical trials was submitted on May 2, 1973 (NO TE 2436-200) and reviewed on May 22, 1973. Again, clinical trials were not approved. However, in recog- nition of their importance and imminence, a Workshop on Left Ventricular Assist Pumping was scheduled and convened at NHLI on October 28, 1973. The interested reader is referred to the Report on the Left Ventricular Assist Device (Assistance to the Failing Circulation), DHEW Publication No. (NIH) 75-626, prepared by NHLI staffers, Ruth J. Hegyeli, M.D., and tTHI Clinical ALVAD Report to NHLI (#5), July 12, 1976. ttNorman, JC: The Clinical Applications of Left Ventricular Assist Devices (ALVAD) Contract NumberNOI-HV-5-3006, Report Number NO1-HV-5-3006-1, July4, 1976 (pp. 1-239.) tftNorman, JC: Hemodynamic Effects of ALVAD Pumping in Man, Topical Report to NHLB1 (Contract Number N01-HV-5-3006-2, July28, 1976 (pp. 1-36). 250 Michael R. Machesko, B.A., January 11, 1974, wherein much of our data is summarized. Our progress over the intervening year was again reviewed at NHLI on October 17, 1974; again on May 15, 1975, and clinical investigations began in our institutions in November of 1975. The first clinical trial was under- taken on December 23, 1975. BACKGROUND The concept of circulatory assistance is not new. The need for such temporary support for weeks to months has been recognized for more than a decade, and still exists. The most common form of acute, iatro- genic, potentially reversible circulatory failure in man is that following cardiopulmonary bypass. If reliable means were available to support tem- porarily the circulation of such patients, the current low mortality asso- ciated with open heart surgery would be further decreased and, perhaps, the indications for high-risk patients broadened. For example, following otherwise uncomplicated procedures, it is common for patients to require reinstitution of cardiopulmonary bypass for brief periods to allow the biologic left ventricle to resume its pumping function to support the peri- pheral and central circulations. There is a correlation between the duration of the necessary period of re-support with the degree of acute left ven- tricular decompensation encountered. The limitations of prolonged bypass are hemolysis, protein denaturation, the appearance of hemorrhagic dia- theses, and sepsis along vascular-access perfusion lines. Cardiopulmonary bypass is a controlled form of shock and applicable for only short periods of time. The techniques proposed for circulatory assistance have included aortic bypass pumping (vide supra), intra-aortic balloon pumping, counter-pulsa- tion with an ectopic ventricle, external regional counterpulsation, synchro- nous airway pulsation, veno-venous oxygenation, veno-arterial oxygena- tion, mechanical synchronous sternal compression, and left atrial to sys- temic arterial pumping byvarious means for short periods of time. All have been utilized in man with varying degrees of success. In comparison, our abdominal left ventricular assist device is a true intracorporeal blood pump. Unlike the intra-aortic balloon pump, which augments existing circulation, the ALVAD is capable of generating flows up to ten liters per minute, independent of an intact EKG signal, and can be conceived of as an implantable partial artificial heart or life-support system. Such concepts and principles must be submitted to peer review in the current climate of the increasing involvement of medicine, tech- nology, industry, and government with society. Clearly, clinical use df this device involves not only the aforementioned sectors, but also impinges on moral, legal, and ethical interests.* It should be emphasized that, over the last four years, these implications have been given careful consideration. The National Heart, Blood Vessel, Lung and Blood Act of 1972 reaffirms the responsibility for research and *The Totally Implantable Artificial Heart. Report of Artificial Heart Assessment Panel. DHEW publication 74191, June, 1973. 251 development in this area; there is to be both research into, and establish- ment of programs dealing with devices and instrumentation. The details can be found in Sections 413 (A), items 3 and 4. Legislation is not specified. DESCRIPTION OF THE, ABDOMINAL LEFT VENTRICULAR ASSIST DEVICE SYSTEM The abdominal left ventricular assist device system includes the follow- ing major subsystems: (1) the left ventricular assist device, (2) the clinical drive console, and (3) the pneumatic pump monitor. Abdominal Left Ventricular Assist Device The abdominal left ventricular assist device (ALVAD) (Figure 1) is a single-chambered implantable blood pump actuated by an external pneu- matic drive console. The pumping chamber is symmetric about a central axis. It weighs 470 gm, measures 17 cm in length, and has a maximum diameter of 6.3 cm with a displacement of 300 ml. It consists of a polyure- thane bladder which collapses in three segments or lobes when pneumatic pressure is applied to the space between the bladder and the titanium housing. Unidirectional flow is imparted by caged silicone rubber disc valves at the inflow and outflow orifices. The design stroke volume of the ALVAD is 100 ml; flow rates in excess of 10 liters per minute have been measured in-vivo. Polyester fibers (0.001" in diameter and 0.010" in length) coat all blood-contacting surfaces except the valve discs and inflow and outflow grafts.* These fibers provide a matrix on which a bio-derived blood-compatible surface develops, i.e. a neointima on a substrate of fibrin and erythrocytes. A unique characteristic of the ALVAD is its anatomic placement (Figure 2). The pump is designed for abdominal placement to facilitate implanta- tion without pulmonary compromise and to permit subsequent removal without thoracotomy. Blood is received from the apex of the left ventricle Pneumatic drivetube Blad , ~~~Housingi Qewingring c \ 4 o h eguidepin Inflotub Fleiblereinforced conduit Valve disc Inlet threadedOulthr d attachment Valvedisc Outlet threaded attachment : THI Aortic graft Fig. 1. The abdoniinal left ventricular assist device: cutaway illustration. *Meadox Medicals low porosity, 6 Raritan Road, Oakland, N.J., 07436 252 !' through a semi-flexi- b1 transdiaphragma- e N,~:xt) tic inlet tube and ejected into the infra- renal abdominal aorta *t,^itlll 'v \ via a tightly woven lowporosity polyester chronic experiments in dogs and calves have N ~~~~~~~~~~~~~indictahtaedt: (1) the lN¢->; 8 ^; .>-- =' | ALVAD is hemody- namically effective 01;jC 0\~ X and mechanically re- liable, (2) the configura- '.\\ition is practical, and (3) Fj!\lXN,\ I\'ano untoward perturbation of cardiac function is dem- l onstrable when inf ow tubes have been left in situ over exdatyesn)d.ed periods (up to 289 Another major prerequi- Ii' _ ,,.j site for clinical application | oflthe ALVAD was the de- _,I,,,,,*,,rSv@ termination of its volume- tric and geometric suitabil- i s< ,\lt\ ity relative to the anatomic variations and constraints inman. Human fitting stud- ies included trial ALVAD fittings in 20 patients un- /tt.'-zdergoing resections of ab- dominal aortic aneurysms and post-mortem ALVAD implantations in 15 cadav- Fig. 2. Anatomic placement of the ALVAD (expanded). ers. No anatomic limitations were encountered in the trial fittings or cadaver implantations. Variations in left ventricular apex orientation were accommodated by adjustment of the flexible inlet tube. Variations in distance from the pump outlet to the abdominal aorta were accommodated by tailoring of the polyester outflow graft. In no instance was post-mortem ALVAD implantation precluded by geometric or volu- metric constraints. Clinical Drive Console For actuation and control of the ALVAD, it is necessary to have vari- able settings of pump chamber pressurization (0-400 mmHg), vacuum- assisted pumping chamber filling (0-200 mmHg), pulse duration (0-600 msec), and synchronized counterpulsation delay following QRS detection (100-1000 msec). To satisfy these requirements, an external clinical drive 253 console has been designed and tested which provides: (1) pneumatic drive and control, (2) electronic logic, and (3) failsafe mechanisms desirable for clinical use. There are two modes of operation: (1) EKG-triggered syn- chronous counterpulsation, and (2) variable fixed-rate asynchronous pump- ing. There are two pneumatic subsystems. The primary subsystem will operate in either mode; a secondary subsystem provides drive pressure at adjustable fixed rates, should the primary system fail for any reason. Both pneumatic subsystems allow adjustments of pump pressurization and pump ejection (systolic) time, with augmentation by vacuum-assisted filling available in the primary pumping module. Four failsafe functions are pro- vided for: (1) EKG interruption, (2) primary subsystem mechanical or electrical failure, (3) loss of external pneumatic power, and (4) loss of AC line power. The internal pneumatic and electrical power supplies permit fully portable operation of the console for periods of 50 minutes. A four- month console life test has been conducted in our laboratories without the occurrence of any failure which would cause discontinuation of pumping. Pneumatic Pump Monitor The pneumatic pump monitor (PPM) has been developed for control and quantitation of ALVAD function. This device consists of a pneumatic iso- lation piston and cylinder in the pump drive line, piston displacement transducer, drive line pressure transducer, and an analog computer with digital display and analog outputs. By adjustment of the isolation piston displacement, the pump stroke volume can be regulated to any percentage (20 to 90) of full capacity, thereby continuously avoiding pump bladder over-collapse with any possible denudation of developing neointima. The piston displacement and drive line pressure transducer signals are utilized to compute pump stroke volume according to the formula: SV=ApX-V1 ( PT ) Patm+PT where SV=stroke volume; Ap=piston area; X=piston displacement; V1=initial air volume within the isolation cylinder, drive line and pump housing; PT=drive line pressure, and Patm=atmospheric pressure. The computed stroke volume is multiplied by the pumping rate to yield pump minute flow. Digital data available from the PPM include: (1) pump stroke volume (0-95 ml), (2) ALVAD beat rate (5-140 bpm), and (3) pump min- ute flow (0-13.3 L/min). In addition, drive line pressures (-200 to +400 mmHg), rate of pump filling and ejection (0-1000 ml/sec), and duration of pump filling and ejection (0-600 msec) are available as analog signals. Monitoring of these parameters allows maximum control, adjustment and fine tuning of ALVAD assistance. PATIENT SELECTION Informed consent* is to be obtained from all high-risk adult patients. Such patients, who cannot be weaned from cardiopulmonary bypass fol- lowing conventional resuscitative measures, including intra-aortic balloon pumping, have constituted the first category of patients to be considered for ALVAD implantation. A second category of patients are those who are not thought to be at high *See Appendix I, page 287. 254 risk preoperatively, but who cannot be weaned from cardiopulmonary bypass with pharmacologic and IABP support as above. Informed consent is obtained from their nearest relatives. A third category of patients as possible candidates are those who have undergone open heart procedures, have been weaned from cardiopul- monary bypass, but are unresponsive to increasing concentrations of vas- opressors during intra-aortic balloon pumping in the recovery rooms. In- formed consent is obtained from their relatives. In the first two categories, maximum efforts are exerted to re-establish ventricular function and to obtain adequate cardiac output using pharmacologic agents combined with partial cardiopulmonary bypass support and intra-aortic balloon pumping for a minimum of 30-60 minutes.*t The decision to implant the ALVAD requires the agreement of the surgeon(s) and attending anesthesiologists and/or cardiologists that all acceptable and reasonable measures to restore cardiac function have been exhausted. This decision is -reflected in the patient's record. Similar decisions are reached in the recovery rooms or intensive care units to return deteriorating patients to the operating rooms for ALVAD implantation. INFORMED CONSENT When possible, informed consent is obtained from high-risk patients. In instances where informed consent cannot be obtained from the patient, it is obtained from the nearest relative. This consent form reflects serial legal consultations of Attorney Richard Bergner of the Texas Heart Institute Human Studies Committee, along with William J. Curran, Frances Lee Professor of Legal Medicine of the Harvard School of Public Health, and Attorney Henry C. Reinhard, Administrator of the Fort Worth Children's Hospital. It has been modified according to the recommendations of the NHLI Workshop on Left Ventricular Assist Pumping (DHEW Publication No. NIH 75-626, January 11, 1974) and those of the Human Studies Com- mittee of the Texas Heart Institute and the Research and Publications Committee of the St. Luke's Episcopal and Texas Children's Hospitals. The informed consent statement contains the basic elements outlined in The Institutional Guide to DHEW Policy on Protection of Human Subjects (DHEW Publication No. NIH 72-102, December, 1971). Conversations dur- ingthe explanation of the consent form are tape recorded and submitted to federal auspices. PATIENT MANAGEMENT The patient management protocol for ALVAD implantation addresses the following specific areas: (1) pump implantation in the operating room; (2) patient transport to the recovery room (ALVAD suite); (3) postoper- ative clinical management; (4) pumping modes; (5) patient weaning op- tions; (6) pump removal; and (7) pump dependence. *According to NHLI Criteria for Clinical Investigative Use of Left Ventricular Assist Devices, August 8, 1974, Section III, c. 3. tNorman JC and Bernhard WF: Criteria, protocols and reporting forms for initial left ventricular assist device clinical trials (special supplement). Cardiovascular Diseases, Bulletin of the Texas Heart Institute 2(4) :438, 1975 255 PUMP IMPLANTATION ALVAD implantation can be performed in any of our eight cardiovascular surgical suites (Figure 3). The basic techniques of anastomosis of the out- flow graft to the infrarenal abdominal aorta, left ventricular apical ex- cision and inflow tube insertion developed in calves are utilized in man. The primary steps of clinical implantation are: (1) Continuation or reinstitution of total cardiopulmonary bypass. (2) Reinsertion of a left ventricular sump via the right superior pul- monary vein-left atrial junction. (3) Extension of the median sternotomy into the abdomen, to and around the umbilicus (Figure 4). g~:~<~<'~~~~~~C~~~e~R\rdievsosle"r CVSA CV Oprating Room Central Supply 21:F10 CV S Pbatet 1~~~~~~. Cordlopulmosery PUMP / | i % ~2.~~i~n~s~r~u~mn~t~3T.able Bypass C\/ 3 J^4. ALVAD Console J C\V4 5 Defibrillotor l6. Potiont Monitor 1118) /7. Anesthesiologists Table 'yc< .. 3Chennel Rec-order 9. Bowie Electrocaut,ry Unit Stairsyt o CVSRL 30a762, .3a761 R:"tar 3 IcU ,.,a Ram ALVAD Suite lCUI StationCeta I Fig. 3. Floor plan of Texas Heart Institute Cardiovascular Surgical Facilities with representative details of equipment in each operating room and the location of the ALVAD suite. ICU's 1, 2, 3, and 4 have a total of 100 beds. 256 (4) Anastomosis of the outflow graft to the infrarenal abdominal aorta with care being taken to avoid the IABP pump cable, if present (Figure 5a-b). (5) Suturing of the Teflon felt sewing ring to the left ventricular apex (to theleft of the terminal radicals of the left anterior descending coronary artery) (Figure 5c). Fig. 4. ALVAD implantation: extension of median sternotomy into abdomen, to and around umbilicus. 257 (6) Fashioning of a small diaphragmatic incision. (7) Cross-clamping of the ascending aorta proximal to the aortic per- fusion cannula. (8) Circular excision of the left ventricular apex within the teflon felt sewing ring (Figure 5d). A~ ~ ~ C Fig. 5. (a & b) Anastomosis of the ALVAD outflow graft to the infrarenal aorta; (c) Teflon felt sewing ring sutured to left ventricular apex; (d) circular excision of left ventricular apex within Teflon felt sewingring. 258

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CLINICAL READINESS AND INITIAL TRIALS IN MAN. John C. clinical readiness of an abdominal left ventricular assist device (ALVAD) according to . tion with an ectopic ventricle, external regional counterpulsation, synchro-.
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Most books are stored in the elastic cloud where traffic is expensive. For this reason, we have a limit on daily download.