Non–Blood-Contacting Biventricular Support: Direct Mechanical Ventricular Actuation
1999; Elsevier BV; Volume: 4; Issue: 4 Linguagem: Inglês
10.1016/s1522-2942(07)70128-9
ISSN1532-8627
AutoresJames E. Lowe, G. Chad Hughes, Shankha S Biswas,
Tópico(s)Cardiac Structural Anomalies and Repair
ResumoThe concept of mechanically compressing the ventricles of a failing heart into a systolic configuration followed by passive or mechanically assisted diastole is not new. A variety of bellows, wrap-around devices, and cups have been proposed to augment forward cardiac flow after cardiac arrest. For example, 27 patents have been issued in the United States alone for a variety of such devices beginning as early as 1936. Although seemingly simple and elegant, no one has yet to sufficiently study and refine this concept to produce an accepted, commercially available means to support the failing circulation. In fact, the overwhelming majority of patents issued were for totally unassembled and untested devices. Direct mechanical ventricular actuation (DMVA), as de-eloped to date in our laboratory, is the only non–blood-contacting means to achieve rapid, biventricular circulatory support.1Lowe JE, St Louie JS, Hendrickson SC, et al: The Duke clinical experience with non-blood contacting biventricular cardiac support. The 3rd Congress of the International Society for Rotary Blood Pumps. Abstr 72, 1995Google Scholar, 2Anstadt MP Perez-Tamayo R Davies MG et al.Experimental aortocoro-nary saphenous vein graft after mechanical cardiac massage.ASAIO J. 1996; 42: 295-300Crossref PubMed Scopus (2) Google Scholar, 3Perez-Tamayo RA Anstadt MP Cothran L et al.Prolonged total circulatory support using direct mechanical ventricular actuation.ASAIO J. 1995; 41: M512-M517Crossref PubMed Scopus (13) Google Scholar, 4Anstadt MP Lowe JE Assisted circulation.in: Sabiston Jr, DC Surgery of the Chest. ed 6. Saunders, Philadelphia, PA1995: 1995-2016Google Scholar, 5Anstadt MP Perez-Tamayo R Walthall HP et al.Myocardial tolerance to mechanical actuation is affected by biomaterial characteristics.ASAIO J. 1994; 40: M329-M334Crossref PubMed Scopus (7) Google Scholar, 6Anstadt MP Tedder M Hedge SA et al.Pulsatile versus nonpulsatile reperfusion improves cerebral blood flow after cardiac arrest.Ann Thorac Surg. 1993; 56: 453-461Abstract Full Text PDF PubMed Scopus (36) Google Scholar, 7Anstadt MP Tedder M Hedge SA et al.Intraoperative timing may provide criteria for use of post-cardiotomy ventricular assist devices.ASAIO J. 1992; 38: 147-150Crossref Scopus (4) Google Scholar, 8Anstadt MP Tedder M Van der Heide RS et al.Cardiac pathology following resuscitative circulatory support: Direct mechanical ventricular actuation versus cardiopulmonary bypass.ASAIO J. 1992; 38: 75-81PubMed Google Scholar, 9Lowe JE Anstadt MP Van Trigt P et al.First successful bridge to cardiac transplantation using direct mechanical ventricular actuation.Ann Thorac Surg. 1991; 52: 1237-1245Abstract Full Text PDF PubMed Scopus (32) Google Scholar, 10Anstadt MP Taber JE Hendry PJ et al.Myocardial tolerance to ischemia following resuscitation: Direct mechanical ventricular actuation versus cardiopulmonary bypass.ASAIO Trans. 1991; 37: M518-M519PubMed Google Scholar, 11Anstadt MP Stonnington MJ Tedder M et al.Pulsatile reperfusion following cardiac arrest improves neurologic outcome.Ann Thorac Surg. 1991; 214: 478-490Google Scholar, 12Anstadt MP Anstadt GL Lowe JE Direct mechanical ventricular actuation: A review.Resuscitation. 1991; 21: 7-23Abstract Full Text PDF PubMed Scopus (38) Google Scholar, 13Anstadt MP Hendry PJ Plunkett MD et al.Mechanical myocardial actuation during ventricular fibrillation improved tolerance to ischemia compared to cardiopulmonary bypass.Circulation. 1990; 82: 284-290PubMed Google Scholar, 14Anstadt MP Hendry PJ Plunkett MD et al.Mechanical cardiac actuation achieves hemodynamics similar to cardiopulmonary bypass.Surgery. 1990; 108: 442-451PubMed Google Scholar, 15Anstadt MP Hendry PJ Plunkett MD et al.Comparison of direct mechanical ventricular actuation and cardiopulmonary bypass.ASAIO Trans. 1989; 35: 464-467Crossref PubMed Google Scholar Dynamic cardiomyoplasty using blood-contacting latissimus dorsi muscle requires weeks of muscle preconditioning before transfer around the heart and provides only limited assistance in its present state of development and has largely been abandoned. Non–blood-contacting biventricular support using DMVA has the following advantages: 1.Rapid application through a small left anterior thorcotomy without requiring cardiopulmonary bypass.2.No bloodstream contact eliminates the need for anticoagulation.3.Can be used to provide circulatory support in the failing, fibrillating, and asystolic heart.4.The risks of hemorrhage and thromboembolism are reduced because bloodstream contact and the need for anticoagulation are eliminated.5.No blood contact and device application via a thoracotomy instead of a median sternotomy may reduce infectious complications.6.Reduced healthcare costs in patients requiring mechanical support for refractory heart failure.7.DMVA can be used to reverse end-organ failure secondary to refractory heart failure and identify patients who would benefit from implantation of temporary or totally implantable left ventricular arrest devices. DMVA can be rapidly applied to provide immediate hemodynamic stabilization. DMVA employs a contoured cup that attaches itself to the ventricular myocardium via a continuous vacuum at the apex of the cup. Once attached, positive and negative pneumatic forces operate on a diaphragm within the cup to “actuate” both ventricles into respective systolic and diastolic configurations (Fig I). Appropriate delivery of uniform positive and negative forces to the ventricles rapidly returns the failing, systolic, or fibrillating heart to its function as a blood pump. The apical vacuum source seals the actuating diaphragm to the myocardial surface, and, consequently, the device not only compresses the ventricles to create systole, but also enhances cardiac filling by decompressing the ventricles into a diastolic configuration.9Lowe JE Anstadt MP Van Trigt P et al.First successful bridge to cardiac transplantation using direct mechanical ventricular actuation.Ann Thorac Surg. 1991; 52: 1237-1245Abstract Full Text PDF PubMed Scopus (32) Google Scholar The massaging action of DMVA is controlled by a pneuatic drive unit that has both pulsed volume and sustained vacuum systems (Fig I). The vacuum system allows for device attachment and can be adjusted to the mini-al degree of suction (usually ∼40 to ∼70 mm Hg) needed to maintain a constant diaphragm-to-epicardium seal. The internal diameter in millimeters of each assist cup is identified by a numerical label. An appropriate cup size is one that approximates the greatest transverse diameter of the unassisted heart.9Lowe JE Anstadt MP Van Trigt P et al.First successful bridge to cardiac transplantation using direct mechanical ventricular actuation.Ann Thorac Surg. 1991; 52: 1237-1245Abstract Full Text PDF PubMed Scopus (32) Google Scholar Wrap-around Duramer(K & L Technologies, Durham, NC) support cups currently under development eliminate the lifting and shearing vectors present in old silastic cups (Fig II).16Kovacs S, Lowe JE: Personal communication, 1997Google Scholar Once the need for DMVA has been established, the assist cup can rapidly be positioned through a small left anterior, sixth intercostal space thoracotomy (see Surgical Technique). After the heart is adequately exposed, a general size is selected, and the device is positioned over the ventricular apex while set in a diastolic mode. The drive system's continuous vacuum source causes the device to aspirate itself onto the heart. Once attached, the drive system is switched into an actuating mode, which cycles positive and negative forces from the pulsed volume source, resulting in ventricular systole and diastole. DMVA application literally takes seconds after adequate exposure has been obtained.9Lowe JE Anstadt MP Van Trigt P et al.First successful bridge to cardiac transplantation using direct mechanical ventricular actuation.Ann Thorac Surg. 1991; 52: 1237-1245Abstract Full Text PDF PubMed Scopus (32) Google Scholar Operation of the current pump system is accomplished with a computer that has memory, timer, and input/output functions. The computer interfaces with an operator panel, which allows the setting of assist rate (or synchronization to an R-wave trigger pulse), systolic duration, systolic volume, and diastolic pressure and monitors the systolic pressure within the diaphragm driveline (Fig III).16Kovacs S, Lowe JE: Personal communication, 1997Google Scholar To date, we have used DMVA in five patients in cardiogenic shock. The etiologies of the cardiac failure were diverse and included idiopathic dilated cardiomyopathy (n = 2), massive myocardial infarction (n = 2), and viral myocarditis (n = 1). There were no device-related complications or deaths.1Lowe JE, St Louie JS, Hendrickson SC, et al: The Duke clinical experience with non-blood contacting biventricular cardiac support. The 3rd Congress of the International Society for Rotary Blood Pumps. Abstr 72, 1995Google Scholar The cardiac support cups were applied only in patients who were not candidates for blood-contacting ventricular assist devices. Duration of support ranged from 2 days to 3 months. Two patients are long-term survivors (one bridge-to-transplant and one recovery from viral myocarditis). Figure IV shows preparation for cardiopulmonary bypass before cardiac transplantation in a patient when the device was placed as a bridge. Figure V displays the systemic arterial and venous pressures before and during 45 hours of support in a DMVA recipient.Fig VSystemic arterial and venous pressures before and during 45 hours of support in a DMVA recipient. Use of an intra-aortic balloon pump and all inotropic agents was discontinued immediately after DMVA application. (Reprinted with permission from the Society of Thoracic Surgeons.9Lowe JE Anstadt MP Van Trigt P et al.First successful bridge to cardiac transplantation using direct mechanical ventricular actuation.Ann Thorac Surg. 1991; 52: 1237-1245Abstract Full Text PDF PubMed Scopus (32) Google Scholar)View Large Image Figure ViewerDownload (PPT) The pathology of the hearts in the three patients who died showed encasement in a fibrinous epicardial peel, which appeared to provide a physiological buffer or lubricant preventing significant myocardial trauma. After 7.5 days of support in the patient who recovered from viral myocarditis, there was no clinical evidence of myocardial trauma. Before discharge, echocardiography and a rest and exercise multiple uptake gated acquisition scan showed complete return of normal cardiac function.1Lowe JE, St Louie JS, Hendrickson SC, et al: The Duke clinical experience with non-blood contacting biventricular cardiac support. The 3rd Congress of the International Society for Rotary Blood Pumps. Abstr 72, 1995Google Scholar In 1964, the first series of DMVA experiments involving successful circulatory support were performed on a dog during 8 hours of ventricular fibrillation (VF). At the time, this was the longest period of total circulatory support resulting in long-term survival.17Anstadt GL Blakemore WS Baue AE A new instrument for prolonged mechanical massage.Circulation. 1965; 31 (abstr): 43Google Scholar Later in the mid-1960s, longer periods of total circulatory support were evaluated with a 50% survival reported in animals supported for 24 to 40 hours of VF.18Anstadt GL Britz WE Continued studies in prolonged circulatory support by direct mechanical ventricular assistance.ASAIO Trans. 1968; 14: 297-303Google Scholar Coogan, in the late 1960s, examined the possible traumatic effects of DMVA on the heart, with extensive histological evaluations performed on the organs of dogs surviving long term after support for 6 to 24 hours of VF. Studies were performed examining animals at 48 hours (acute effects) and 3.5 to 20 months (chronic effects) after weaning from DMVA and restoration of normal sinus rhythm.19Coogan PS Casey HW Skinner DB et al.Direct mechanical ventricular assistance. Acute and long-term effects in the dog.Arch Pathol. 1969; 87: 423-431PubMed Google Scholar At 48 hours, all hearts appeared histologically normal except for a variable degree of nontransmural ecchymosis on the endocardial surface of the right ventricle near the pulmonary outflow tract. The chronic hearts also showed normal histology except for a small (< 1 cm2Anstadt MP Perez-Tamayo R Davies MG et al.Experimental aortocoro-nary saphenous vein graft after mechanical cardiac massage.ASAIO J. 1996; 42: 295-300Crossref PubMed Scopus (2) Google Scholar) nontransmural scar in the same region of the right ventricle. The epicardial surfaces showed a third, nonconstrictive fibrinous layer.18Anstadt GL Britz WE Continued studies in prolonged circulatory support by direct mechanical ventricular assistance.ASAIO Trans. 1968; 14: 297-303Google Scholar The right ventricular pathology likely resulted from the overzealous application of pneumatic forces during early systolic actuation. These forces can be eliminated with proper adjustment of DMVA drive parameters, such as dampening of systolic pressure. Most investigators agree that the pathology seems minimal when one realizes how poorly the fibrillating heart tolerates other methods of circulatory support.3Perez-Tamayo RA Anstadt MP Cothran L et al.Prolonged total circulatory support using direct mechanical ventricular actuation.ASAIO J. 1995; 41: M512-M517Crossref PubMed Scopus (13) Google Scholar, 20Bell JW Beretta FF Prolong ventricular fibrillation: An experimental study in the closed chest animal utilizing a pump oxygenator.J Thorac Cardiovasc Surg. 1959; 38: 17-29PubMed Google Scholar, 21Najafi H Henson D Dye WS et al.Left ventricular hemorrhagic necrosis.Ann Thorac Surg. 1969; 7: 550-561Abstract Full Text PDF PubMed Scopus (95) Google Scholar, 22Ghidoni JJ Liotta D Thomas H Massive subendocardial damage accompanying prolonged ventricular fibrillation.Am J Pathol. 1960; 56: 15-30Google Scholar, 23Maloney LV Cooper N Mulder DG et al.Depressed cardiac performance after mitral valve replacement: A problem of myocardial preservation during operation.Circulation 51:1975;. 1975; 52: 13-18Google Scholar, 24Smith KW Crofts J Rich GF et al.Histopathology in a myocardial failure model for biventricular bypass evaluation.Trans Am Soc Artif Intern Organs. 1982; 28: 105-109PubMed Google Scholar, 25Rich GF Smith KW Kwan-Gett CS et al.Hemodynamic and pathologic consequences of biventricular bypass using left atrial versus left ventricular withdrawal.Trans Am Soc Artif Intern Organs. 1985; 31: 84-89PubMed Google Scholar More recently, we were able to provide total circulatory support in a sheep for 7 days of VF. The heart was subsequently defibrillated into sinus rhythm. During the period of support, no creatine kinase/myocardial band fraction was greater than 1%, suggesting that prolonged application of DMVA during VF does not result in serious myocardial injury. Additionally, renal function was preserved during the period of support, as evidenced by normal urine output, blood urea nitrogen, and creatinine levels. Histologically, the heart showed a fibrinous pericarditis with bruising limited to the outer 1 mm of the epicardium and scattered foci of contraction band necrosis of varying severity. Scanning electron microscopy showed no evidence of cellular ingrowth into the silicone rubber diaphragm. Neurologically, the 7-day support animal was intact with no evidence of cerebral lesions on neuropathologi-cal examination.3Perez-Tamayo RA Anstadt MP Cothran L et al.Prolonged total circulatory support using direct mechanical ventricular actuation.ASAIO J. 1995; 41: M512-M517Crossref PubMed Scopus (13) Google Scholar The pneumatic driveline system for DMVA includes the following properties: 1.Systolic and diastolic actuation must be separately controllable events.2.Systolic compression should be determined by a set volume of air delivered to the cup during the duration of systole. The peak pressure of this cycle should be monitored, but optimal systolic actuation is not a pressure-controlled event. The volume of air delivered during systolic actuation is determined by support cup size, inner compressing membrane compliance, myocardial compliance, ventricular after-load, and the desired cardiac output to be achieved.3.The volume of air delivered during systolic actuation of the cup (regardless of systolic duration) is the same volume of air that must be evacuated from the cup during systolic actuation (independent of diastolic duration). The rate of evacuation of air during diastolic actuation determines the negative pressure exerted on the heart to maximize diastolic filling of the ventricles.4.Finally, the pump is capable of both synchronous and asynchronous operation. After acute hemodynamic stabilization, systolic (+ 120 to +130 mm Hg) and diastolic (–100 to –115 mm Hg) forces and flow rates can be adjusted to maximize hemodynamics. Cycle rates are generally set between 80/min (large hearts) to 120/min (smaller hearts). Adequate left ventricular emptying is generally achieved by systolic durations set to 44% of the DMVA cycle. This is important so as to minimize the potential for pulmonary edema, which may result from an abbreviated systolic force emptying the right, but not the left, ventricle. To further help avoid this complication, pulmonary artery wedge pressures should be monitored in all DMVA patients. A progressive elevation in wedge pressure during support indicates the need for increased systolic duration.9Lowe JE Anstadt MP Van Trigt P et al.First successful bridge to cardiac transplantation using direct mechanical ventricular actuation.Ann Thorac Surg. 1991; 52: 1237-1245Abstract Full Text PDF PubMed Scopus (32) Google Scholar The potential for other complications may be minimized through preparation. A leak in the actuating diaphragm is easily detected by fluctuations in driveline and vacuum attachment pressures. Although such an event requires device replacement, initial hemodynamic stabilization can be maintained by increasing driving pressures. The possibility of a pneumothorax is prevented by placement of a chest tube at the time of initial thoracotomy. The pneumatic drive unit is an unlikely source of mechanical failure but should be monitored closely as with any other device. For these reasons, an additional drive unit is available for emergency back-up at all times.9Lowe JE Anstadt MP Van Trigt P et al.First successful bridge to cardiac transplantation using direct mechanical ventricular actuation.Ann Thorac Surg. 1991; 52: 1237-1245Abstract Full Text PDF PubMed Scopus (32) Google Scholar
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