Does heart failure cause sleepiness?

Yes, it can: Heart failure can certainly cause profound fatigue and weakness, and even increased sleepiness. This is usually as a result of limited forward blood flow out of the heart, for instance to skeletal muscles (limits activity tolerance), the brain and so on. It's also very common for people with heart failure to develop sleep apnea, making their sleep quality suffer and leading to daytime sleepiness.

It can due to : Decreased energy level and fatigue.