**8. Hemodynamic evaluations of a valve equipped Biomechanic Heart Model supporting a failing myocardium in goats**

As shown previously in goats, valve-less Biomechanical Hearts (BMHs) of a clinically relevant size could be trained effectively in the systemic circulation under support of clenbuterol. Pumping capacity was more than 1 L/min but due to a high pendulum volume no significant flow contribution for the circulation was gained. Thus, the following investigations were performed to evaluate the efficacy of valve-equipped BMHs in comparison to valve-less BMHs. To mimic the clinical situation, this test was performed in failing hearts [12].

Heart failure was induced in adult Boer goats (n=5) by a repeated intra-coronary embolization. A valve-bearing and balloon-equipped pumping chamber was integrated into the descending aorta simulating standardized circulatory BMH support. Circulatory flow was evaluated by a flow meter around the pulmonary artery. Myocardial function was evaluated by a conductance catheter placed in the left heart ventricle (Figure 16).

**Figure 14.** Stroke volume determination with a conductance catheter, placed within the pumping chamber of the BMH (left, top). Pressure-volume-loop of a BMH on postoperative day 132 with a stroke volume of 34.8 ml and an output of 1400ml per minute (right, top). ECG with stimulation bursts, a pressure trace from a peripheral artery where

**Figure 13.** Scheme of an experimental setting in a big animal model in an aorto-aortic configuration. The thoracic aorta is ligated between the two anastomoses. Two muscular stimulation electrodes activate the LDM and an epicar‐

the BMH is in a 1:2 mode and synchronized with the heart (bottom).

dial sensing electrode enables the syncronization with the heart cycle.

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**Figure 16.** BMH model is made of a stiff polyurethane chamber with an integrated pumping balloon. The dividing and re-uniting vascular prostheses were connected end –to-end with the divided descending aorta. In this setting two of the four prosthetic limbs carried heart valves. Thus, by clamping, no, one or two valves could be integrated into the circulation. The influence of different valve configurations on circulation could be evaluated in supporting a failing heart. Ultrasonic flow probes were placed around the pulmonary artery, aortic arch and the descending aorta. Within the left heart ventricle a conductance catheter was placed, and via a catheter within the left coronary artery an embo‐ lization could be induced and a flow wire could be introduced [12].

Skeletal Muscle Ventricles (SMVs) and Biomechanical Hearts (BMHs) with a Self Endothelializing Titanized… http://dx.doi.org/10.5772/55993 355

**Figure 17.** Results of the BMH model described in Fig. 16, without, with a distal and with two valves: mean aortic pres‐ sure( PAo, grey column), mean pulmonary flow (QPA, black column), mean flow velocity within the left coronary artery (VC, white column) [12].

**Figure 16.** BMH model is made of a stiff polyurethane chamber with an integrated pumping balloon. The dividing and re-uniting vascular prostheses were connected end –to-end with the divided descending aorta. In this setting two of the four prosthetic limbs carried heart valves. Thus, by clamping, no, one or two valves could be integrated into the circulation. The influence of different valve configurations on circulation could be evaluated in supporting a failing heart. Ultrasonic flow probes were placed around the pulmonary artery, aortic arch and the descending aorta. Within the left heart ventricle a conductance catheter was placed, and via a catheter within the left coronary artery an embo‐

lization could be induced and a flow wire could be introduced [12].

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Valve-less BMHs offered an additional pulmonary flow of 113± 37 ml/min resp. 5.4±1.8%, those with one distal valve offered 304±126 ml/min resp. 14.5±6%. BMHs equipped with two valves increased the pulmonary blood flow by 1235± 526 ml/min resp. 58±25 % (p<0.05), the mean aortic pressure in this setting raised to 19±9 mmHg (p<0.05) and the coronary flow velocity to 59±18 mm/sec (p<0.05). Corresponding reduction of left ventricle's end-diastolic pressure ranged from 31 to 17 mmHg (p<0.05), while the myocardial dp/dt increased by 470±192 mmHg/ s resp. 145±48 % (p<0.05).

**Figure 18.** PV- loops from a conductance catheter placed in the left heart ventriclea cavum, without (A) and with an activated (B) double-valved BMH-model as shown in Figure16. It works ECG-triggered in a 1:2 mode with a balloon inflation of 60ml helium gas. The area within a loop represents the left heart ventricles stroke work. During activation of the BMH-model the stroke work of the failing heart ventricle is increased (B) and the end-diastolic pressure (LVEDP) drops from 28 to 14 mmHg [12].

The use of two valves in BMHs is essential for a relevant circulatory support. Unloading and contractility of the left heart ventricle were thus improved significantly. Two-valves-BMHs driven by a sufficient skeletal muscle ventricle may contribute to the therapy of a failing myocardium.

**Figure 19.** Reduction of the left ventricular end-diastolic pressure (LVEDP, black columns) evaluated as demonstrated in Figure 16 and 18 and an increase of the left ventricular contractility activation of the pumping balloon from the BMH-model in Figure 16, without, with a distal and with a proximal and a distal valve.
