The researchers looked at 2137 cases of out-of-hospital cardiac arrest in Wroclaw, Poland, to understand what factors affect the chance of someone's heart starting to beat again. They found that when bystanders start CPR, it can improve the person's chances. Having a specific kind of abnormal heart rhythm called ventricular fibrillation or tachycardia was also linked to a higher chance of getting a pulse back compared to other types of heart rhythm issues. If the cardiac arrest happened in a public place, the chances of getting a pulse back were higher too. Even though age, gender, and the type of medical team responding didn't affect the success of reviving the heart, the study showed that more people need to be trained in CPR to help save lives.