Three key features of cardiac muscles are:

1. Cardiac muscles are involuntary muscles that contract rhythmically and continuously without fatigue, enabling the heart to pump blood efficiently throughout life.
2. The cells of cardiac muscle are cylindrical, branched, and typically have one central nucleus; they are connected by specialized structures called intercalated discs that facilitate synchronized contraction.
3. Cardiac muscle cells have a striated appearance due to organized contractile proteins and contain abundant mitochondria to meet high energy demands for sustained contraction.

These features make cardiac muscle uniquely suited for its role in the heart, allowing strong, coordinated, and rhythmic contractions necessary for maintaining blood circulation.