DeVELoPMENT of Muscular Bloodpumps,

Performed in A One-Step Operation

N. W. Guldner¹, P. Klapproth¹M. Großherr², H.-H. Sievers¹

Klinik für Herzchirurgie¹, Klinik für Anästhesiologie²Medizinische Universität zu Lübeck,

D-23538 Lübeck Germany

summary

Up to now skeletal muscle ventricles(SMVs) have required a 2-step procedure i.e. the construction, followed by a vascular delay and electrical conditioning and the integration into circulation by a second operation. As shown previously clenbuterol increased power of electrical conditioned SMVs wrapped around a mock system (1,2) as shown in Fig.1

Fig. 1: Top: A SMV around an intrathoracic elastic training device. A muscular contraction induces a pressure increase within the cavity of the elastic device. Bottom: Original pressure curves during a dynamic training from a SMV of group I without b-2-stimulation (A) and group II supported by Clenbuterol (B). Clenbuterol supported SMVs of group II maintained pressure (function) at a high level over time. Stimulation pattern is shown with an increasing number of pulses per burst..

They pumped successfully from construction to several months against a pressure of

60-70mmHg ( 3 ).

Thus a muscular blood pump was performed in a one-step procedure and trained within the circulation under support of clenbuterol. It showed to be hemodynamically relevant and is expected to become clinic practicable for the treatment of end-stage heart failure.

State of the Art

The prevalence of heart failure is increasing in industrial countries and evolving a major problem of health care in the next decades. To meet this challenge intensified research on the disease and especially its treatment alternatives is mandatory since the standard therapeutical option of heart transplantation is limited. Muscle powered cardiac assistance might become a real alternative to heart transplantation.

Desirable properties of skeletal muscle for cardiac assistance include fatigue resistance and powerful mechanical performance. Current clinical application of non fatigable muscle was limited due to the profound power loss after electrical conditioning. In long-term investigations, skeletal muscle ventricles (SMVs) were performed around an elastic intrathoracic training device ( 1-4 ). SMVs were treated over several month by a threefold approach in order to achieve non fatigable and powerful muscle pumps by a combination of electrical conditioning ( 4 ), dynamic training against systemic load, and pharmacological support with clenbuterol. SMVs treated in that way became powerful, as demonstrated elsewhere ( 3 ).

These SMVs were expected to become effective as muscular blood pumps performed in a one-step operation and trained within circulation. This autologous muscular blood pump with a stabilizing inlay, performed in a one-step operation and trained within the circulation, is defined as a Biomechanical Heart (BMH).

Material and Methods

The operative procedure was performed under general anaesthesia in adult 5 Boer goats of a mean weight of 79±6.6 kg. Left latissimus dorsi muscle was dissected free and Myoelectrodes were placed wavelike around the branches of nervus thoracodorsalis. The threshold of the muscle was determined by electrical stimulation. From a double layered muscular tube of latissimus dorsi muscle, a skeletal muscle ventricle was placed around a silicone-polyurethane inlay and inserted into the thorax after partial resection of the 3^rd and 4^th rib. Through an inferior thoracotomy, the vascular prostheses from the ventricular inlay of the BMH were anastomosed with the descending aorta end-to-side (Fig.2)

2).

Fig. 2: Topography of a biomechanical heart in aorta-descendens

position in a goat. The aorta is ligated between the two anastomoses

The aorta was ligated totally between the two anastomoses. A myocardial sensing electrode was placed and connected with a myostimulator to trigger muscle contractions in the sense of counterpulsation. Pump function of the BMH after several weeks of a dynamic training was demonstrated by arterial blood pressure, ventriculography and by means of a conductance catheter resulting in pressure-volume loops (5) (Fig. 3).

Results

Intra-operatively, mean stroke volume of BMHs was 53.8±22.4ml. One month post-operatively in peripherial arterial pressure, mean-diastolic(P_MD) and minimal diastolic pressure(P_min) of BMH supported heart cycles differed significantly from non supported ones as described elsewhere. One BMH, catheterized 132 days postoperatively, shifted 34.8ml per beat and 1.4L/min using a LDM of 330g (Fig.3).

Fig. 3: Volumetry within a BMH by the conductance catheter method (top). ECG with stimulation bursts and pressure trace from a peripherial artery with BMH contractions in 1:2 mode (bottom):

CONCLUSION

Under support of clenbuterol, Biomechanical Hearts of a clinical relevant size can be trained effectively in systemic circulation after a one-step-operation and offer the prospect of a sufficient volume shift and probably unloading of the left ventricle.

REFERENCES

1. Guldner NW, Eichstaedt HC, Klapproth P, Tilmans MHJ, Thuaudet S, Umbrain V, Ruck K, Wyffels E, Bruyland M, Sigmund M, Messmer BJ, Bardos P. Dynamic training of skeletal muscle ventricles. A method to increase muscular power for cardiac assistance . Circulation 89 (3):1032-1040 (1994)

2. Klapproth P, Guldner NW, Sievers HH. Stroke volume validation and energy evaluation for the dynamic training of skeletal muscle ventricles. Int J Artif Organs 20:313-321 (1997)

3. Guldner NW, Klapproth P, Großherr M., Rumpel E, Noel R, Sievers HH. Clenbuterol supported Dynamic Training of Skeletal Muscle Ventricles Against Systemic Load- A Key for Powerful Circulatory Assist ? Circulation 101:2213-2219 (2000)

4. Guldner NW, Klapproth P, Fischer T, Rumpel E, Büchner I, Keller R, Klempien R, Krischer H, Thuaudet S, Noel R, Kuppe H, Sievers HH . Functionally adapted stimulation patterns for a dynamic training of skeletal muscle ventricles in adult goats . BAM;8(1):67-72 (1997)

5. Guldner NW, Klapproth P, Großherr M., BRÜGGE A; SHEIKHZADEH A; TÖLG R; Rumpel E, Noel R, Sievers HH Biomechanical Hearts, Muscular Blood Pumps, Performed in a 1-Step Operation, and Trained Under Support of Clenbuterol

Circulation 104 (2001)

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Priv. Doz. Dr. med. Norbert W. Guldner, Klinik für Herzchirurgie,

Medizinische Universität zu Lübeck, Ratzeburger Allee 160,

D-23538 Lübeck, Germany.

Tel.: 0049-451-500-2108 Fax: 0049-451-500-6035

e-mail: guldner@medinf.mu-luebeck.de