The word "cardiograph" can be broken down into two root words: "cardio," which comes from the Greek word "kardia," meaning "heart," and "graph," which comes from the Greek word "grapho," meaning "to write" or "to record."
Based on this analysis, in the sentence "The cardiograph can print its results on paper," the best meaning for "cardiograph" is "heart monitor."
So the answer is: heart monitor.