The problem with economic sanctions is that they, ironically, work to solidify Putin's power hold.
The original reason for strong popular support behind Putin was that he oversaw a decade of steady economic growth. For many people in Russia, it was the time where they saw their lives change from borderline poverty to something reasonable. It can be argued that he is not the one to take credit, and that it's all due to high oil prices etc, but either way he got to reap the benefits. It's also what triggered the entire "imperial revival" mentality: people see that their country is more prosperous, therefore it is stronger, therefore it is time to remember the old squabbles.
Now, Russian economy was already in recession as it is, and likely one from which it will not require. The sanctions will undeniably accelerate it, but at the same time they give Putin and his clique the ultimate excuse with respect to anything bad that happens with the economy: "Americans did it". Thus, all the rage will be channeled overseas, instead of the people in charge. And if economy does collapse, what you have now is a country of 140 million, raging, armed to teeth, with a history of willing and able to pile up the bodies two to one (and even higher) to win. Oh, and with nukes.
I strongly suspect that, if the sanctions are ultimately successful, the immediate consequence will be the full-on ground invasion of Ukraine by Russia. Not the present proxy war with subtle aid here and there, but Russian tanks on the streets of Kiev, that kind of thing.
If the West really wants to help Ukraine, it needs to give it direct military assistance.