Evaluation of the MVAD pump: stability under high dose x-ray and proton radiation

Ventricular assist devices (VAD) continue to be miniaturized to decrease surgical trauma, allow for alternative implant techniques, and to provide support to a broader patient population. The MVAD pump (HeartWare Inc., Miami Lakes, FL) is the newest in this trend with a smaller displacement compared to current generation VADs. Two MVAD pumps (n = 2) were evaluated for operation stability during irradiation of high dose x-ray and proton therapeutic beams used for cancer treatment. An x-ray beam having energy of 18 MV was generated from a linear accelerator and delivered to the pump at a rate of 6 Gy min(-1) to a maximum dose of 75 Gy. A Proton beam having energy of 208 MeV was generated from a cyclotron. The energy was adjusted by an energy degrader down to 175 MeV, which is equivalent to a depth of 16 cm in water, then modulated longitudinally along the beam-line by 10 cm generating the spread-out-Bragg-peak. The beam was delivered at a rate of 4 Gy min(-1) to a dose of 70 Gy. Pump parameter data including power consumption, estimated flow rate, and impeller speed were recorded and analyzed for changes in pump operation between baseline, irradiation, and post-irradiation. Modeling of x-ray radiation attenuation and scattering were additionally quantified through a treatment planning computer and compared to radiation measurements. Pump operation was consistent for all tests with no fluctuations during radiation. X-ray attenuation was measured to be 27%, corresponding to a three-fold reduction over the previously evaluated HVAD pump (84%). The smaller MVAD pump can withstand therapeutic radiation levels from x-ray and proton particle accelerators and is less of an obstacle for physicians who care for patients requiring both mechanical circulatory support and radiation therapy regimens.