It is, and it has even been done. One large limitation is that it's not a great idea to have batteries inside the body. An LVAD is intrinsically liquid-cooled; batteries are not. Ruggedly encapsulating a battery means it is fairly well-insulated and can get warm. Batteries also fail pretty unpredictably- they're fundamentally dozens of square feet of very thin film, and it's very difficult to ensure that every battery is perfect. But again, it has been done.

Implanting a couple medium-size batteries and the circuitry+magnet for wireless charging is pretty robust to failure, but consider actually making that decision for yourself. You're already accepting huge restrictions, so is the wire that much of an extra burden?

Realistically, if the LVAD loses power, you're dead. It's not like suffocating; without bloodflow (even blood without oxygen!) your brain will die in about two minutes. Chest compressions probably won't even help. You got the LVAD because your heart couldn't pump, and chest compressions will not force blood through the LVAD. Even if this happens in the emergency room your odds are not good. Cutting open a chest to hand-crank a human is not easy. Pulling an ECMO machine and inserting the massive catheters is not easy. You might die while the machine is still rolling towards you.