Domingo Liotta, MD

Dean for the Faculty of Medicine

University of Moron Surgeon in chief of Adult Cardiac Surgery

for Dupuytren Institute and Quilmes Clinic-Private Hospital

Buenos Aires, Argentina

Each year approximately 60.000 to 70.000 people with advanced heart failure can benefit from some form of either anatomical or functional cardiac replacement but only 2.000-2.500 donor hearts are available in the United States.

The HeartMate Left Ventricular Assist System (Thermo Cardiosystems Inc,; Woburn, Mass) has 2 systems: a) the implantable pneumatic LVAS(IP-LVAS) powered and controlled by an external pneumatic drive console and , b) the Vented Electronic LVAS (VE-LVAS) that contains an electric motor within the pump blood housing which receives power and control signals from an external microprocessor and power source via a vented drive line, big enough tube, to allow air circulation and to expel heat.

The worldwide experience with HeartMate systems as of July l998 has been in 1.587 patients at l22 centers. Nine hundred seventy-one patients (70%) received the IP-LVAS and 4l6(30%) received the VE-LVAS. Most transplanted patients (64% with IP-LVAS; 58% with VE-LVAS) recovered from the device implantation and underwent physical rehabilitation (1).

The Second Generation of implantable pneumatic LVAS (Liotta-LVAS;L-LVAS) is in its last stage for clinical implantation .It consists of a titanium housing which contains a seamless blood chamber of segmented polyurethane with double pneumatic pushing plates(figures 1,2) . The weight of the L-LVAS is 170 grams and it can be easily implanted in a pre-peritoneal position below the left hemidiaphragm.

Porcine xenograft valves within the inflow and outflow conduits ensure unidirectional blood flow through the pump .The valves maintain the entire anatomy of the porcine aortic root (figures 3 and 4) and the sinuses of Valsalva whose smooth and uniform anatomy avoids the dangerously tortous angular formation during the valvular opening phase between the nadirs of the biological tissue and the foreign material as it can be seen in most available commercial valves. (2)

L-LVAS: The driving line has a 6 mm inner diameter and it accomplishes multipurpose functions. It contains within its wall, both a spiral MP 35 N alloy type wire (Fort Wayne Metals, Fort Wayne, IN USA.) connected to the epimyocardial lead for electrocardiogram (ECG) sensing and an MP 35 N short spiral wire as mass to be used for an external pacemaker when necessary. The 2 mm. crescent shaped air vent area is built within its walls.

The pneumatic pump system; ECG synchronization mechanism; Emergency Pacemaker Usage and the Air Vent; all of them incorporated into the wall of one single ID 6 mm tube; this makes a unique transcutaneous connection possible.

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L- LVAS has been designed to work in a synchronous mode with the R wave ECG signal from the patient that is in counterpulsation. When the patient's heart frecuency is either below 40 or above 85 bpm or too arrythmic, the unit takes a fixed synchronous mode of 60 bpm automatically. This makes the blood pump synchronized with the ECG a unique system.

The issue on the unnecessary external driver, the wearable unit, is the stronghold of the Electric System advocates. No doubt there is a clear difference during the outdoor ambulatory hours as the patient must only carry an external battery pack and its control; otherwise, patients with pneumatic systems must carry a portable unit. It is light and easy to carry being its performance smooth and noiseless.

. The L-LVAS has 2 units: the indoor and the outdoor units. The indoor unit is a heavy duty unit with a battery autonomy of at least 24 hs. (The patient will stay home for 16 or 20 hs). The patient can easily decouple the outdoor unit from the indoor unit by himself any time he wants to go out. This improves his quality of life greatly.

Being the pneumatic system an external unit it can be permanently observed and eventually replaced in the patient by a more advanced unit in accordance to the constant developments in this field of research.

Long-term LVAS therapy may enable recovery of the damaged heart. Mueller et al reported 5 patients continued to be in class functional I, 51 to 794 days after LVAS explantation ( 3). The LVAS therapy unloads the left ventricle, relieves right-side cardiac congestion ,enhances hepatic arterial perfusion, reduces the elevated level of circulating catecholamine and atrial natriuretic factor; all signs that characterize chronic heart failure. As a result ,the heart is remodeled, and ventricular dilation and myocytolysis are reduced(4).

The device which treats the human heart more gently will prove the most successful one in the long run. No doubt the LV bypass from left atrium (LA) to descending thoracic aorta (DTA) connection treats the heart more gently. The pump flow index (pump flow/ body surface area)is 2.5-3 L (min.m2) ,with the pump frequency of 60 beats/min., and the ejection systolic time of 230 ms. Extracorporeal circulation is unnecessary to be implanted and the DTA anastomosis gives some protection to brain embolism. The LA-DTA bypass will work more efficiently with a dilated LA.

Nevertheless, the blood pump connection LV-Ascending aorta can also been chosen with excellent results.

A long experienced cardiac surgeon will always ask himself what he would select in case of being compelled to implant any new device to a dear one. As a long term experienced cardiac surgeon myself, I would closely examine both the pneumatic and the electric alternative.

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"The principles of Assisted Circulation were born in Baylor University College of Medicine, Houston, Tx.; in 1961". (Michael E. DeBakey, discussion, University of Buenos Aires. May 1996). In fact, D. Liotta and co-workers started the laboratory work at Baylor University College of medicine in 1961 (5-6) and the clinical work in 1963 (7-8). The first device built and experimented by our group in the early days of mechanical circulation research, was an implantable blood pump with an electric motor incorporated to it, and the second one an Implantable Centrifugal Pump (9).

Today 's situation at the dawn of the 21st century is extremely positive.

Figure 1: The schema shows the LVAD in the LA-DTA connection.1, left atrium; 2,inlet connector sutured to LA;3, inlet pump connector; 4, inlet pump's connector with 25 mm porcine aortic valved conduit; 5, blood pump; 6,18 mm Dacron graft sutured to the DTA; 7, DTA; 8 buttony Teflon disc sutured to the external oblique muscle; 9, buttony Teflon disc implanted under the skin; and 10, pneumatic ambulatory external power.

Figure 2: The LVAD is shown in systolic and diastolic cross sections.1, pneumatic chambers; 2, blood chambers; and 3, double pneumatic pushing plates.

Figure 3: The photograph shows a 25 mm porcine bioprosthesis valved conduit. Connectors are not shown. The sinuses of Valsalva and the sinus ridge are partially visible.

Figure 4: The schema shows the LVAD special connector for the bioprosthesis with the aortic root mainained . 1, inflow connector (18mm ID); 2, shock absorber for the closing of the inlet bioprosthesis (in the lumen, Dacron velour for neoendocardium formation); 3, dacron fabric covering the aortic root; 4, aortic root of inlet valve; 5, 1.5 mm rim to secure the bioprosthesis connector at the pump's inlet and outlet; 6, bioprosthesis connector to the pump's inlet; 7, bioprosthesis connector to the pump's outlet; 8,shock absorber for the closing of the outlet bioprosthesis; 9, aortic root of outlet valve; 10, outflow connector (18 mm ID1).

Figure 5: The photograph shows the external driver (hospital unit) and a volunteer carrier of the knapsack (ambulatory). The in door unit is not shown.

1) Frazier O.H, Myers, T.J; Radovancevic B. The HartMate Left Ventricular Assist System. Overview in 12- Year experience

Tex. Heart Institutte J.1998;25:265-71

2) Liotta D. Assisted Circulation for End-Stage Chronic Heart Failure. Artificial Organs 1998; 22 (3):230-236,Blackwell Science Inc. International Society for Artificial Organs.

3) Muller J, Wallukat G, Weng Y G, Dandel M, Spielberger S,Semrau S,at al. Weaning from mechanical cardiac support in patients with idiopathic dilated cardyomiopathy. Circulation 1997; 96:542-9.

4) Westaby S,Jin XY, Katsumata T, Taggart DP, Coats AJ, Frazier O H.. Mechanical Support in dilated cardiomyopathy: signs of early left ventricular recovery. Ann Thorac Surg 1997;64: 1303-8.

5) Liotta D., Crawford E.S., Cooley D.A., DeBakey M.E.,Urquia M.,Feldman L.: Prolonged partial left ventricular bypass by means an intrathoracic pump implanted in the chest. Trans,Amer.Soc.Art. Int. Organs., 1962; 8:90.

6) Liotta D., Hall C. W., Henly W.S., Beall A.C., Cooley D.A., DeBakey M.: Prolonged Assisted Circulation during and after cardiac or aortic surgery. I Prolonged left ventricular bypass by means of an intrathoracic circulatory pump.II. Diastolic pulsation of the descending thoracic aorta. Trans. Amer. Soc.Art.Int.Organs, 1963; 9:182.

7) Liotta D., Hall C.W.,Henly W.S., Beall A.C., Cooley D.A., DeBakey M.: Prolonged Assisted Circulation after cardiac or aortic surgery. Prolonged partial left ventricular bypass by means of intracorporeal circulation. This paper was finalist in: The Young Investigators Award Contest of the American College of Cardiology. Denver, may 1962. Amer.J. of Cardiol., 1963; 12:399.

8) DeBakey M.E. Left Ventricular bypass pump for cardiac assistance. Clinical experience. Am J Cardiol 1971; 127:3.

9) Liotta D., Taliani T., Giffoniello A.H., Sarria Deheza F., Liotta S., Lizarraga R., Tolocka L., Pagano J., Biancciotti E.: Artificial Heart in the chest: Preliminary report. Trans. Amer. Soc. Int. Organs, 1961; 7:318