The rhythmic beating of the heart requires coordinated electrical activity that causes the heart to contract and relax. The electrical activity is controlled by proteins in the membranes of heart cells that form ion channels. Failure of channels to work properly is associated with abnormal heart rhythm, heart attack and sudden death. Long QT Syndrome (LQTS) is a condition that affects 1:2000 people and often results from inherited mutations in one of the heart channels. However, determining whether a mutation will cause the individual serious heart problems is still a major challenge. By using cutting edge technology, like induced pluripotent stem cells and CRISPR, we can recreate patient mutations in cells in the lab and turn them into beating heart cells. Specific techniques can be used to look at individual heart cells, as well as heart cells in a layer that beat together. The properties of the cells can be measured so that the effects of the mutations can be understood, and so that newer specific drugs can be tested to see if they are effective against different mutation types. The results from this research will help inform clinicians on how to better help patients with LQTS and potentially identify new, better treatments.