In Node.js, the event loop is responsible for handling asynchronous I/O operations, and when it becomes blocked, it can severely degrade the performance of your application. This often happens when CPU-intensive operations, such as large calculations, file parsing, or complex loops, run synchronously, preventing the event loop from processing other tasks. To fix this, one solution is to offload heavy computations to Node.js Worker Threads, which allow CPU-bound tasks to run in parallel without blocking the main event loop. Alternatively, you can use techniques like `setImmediate()` or `process.nextTick()` to break long-running synchronous tasks into smaller chunks, allowing the event loop to continue processing I/O operations between each chunk. Another approach is to use native addons written in C++ for performance-critical operations. Understanding how to manage the event loop efficiently is critical for building performant Node.js applications.