MONTREAL, February 13, 2025 – How are pediatric cancer treatments related to the development of cardiac arrythmias? A new study provides relevant data on the long term and often undiagnosed chemotherapy complications of acute lymphoblastic leukemia (ALL) treatments, the most common type of pediatric cancers. To mark the International Childhood Cancer Day (ICCD) and Heart Month, here are highlights of the results of this collaborative study.

“Silent” Heart Complications

Although advances in medicine have led to a significant increase in the survival rate for ALL in children over the years – close to 85 percent –, a large number of young cancer survivors develop health problems following chemotherapy treatments, including cardiovascular complications such as acquired long QT syndrome (aLQTS), a type of heart arrhythmia caused by problems with the heart’s electrical system. While this syndrome doesn’t appear in the heart structure, the person may nonetheless experience fast and uneven heartbeats caused by exercise or stress. It may sometimes cause sudden fainting and seizures, and increases the risk of developing potentially deadly events such as cardiac arrest.

For the purposes of this study, approximately 200 childhood ALL survivors were asked to undergo a treadmill stress test. The results indicated that 70 percent of the participants who had an abnormal QT during the test presented no anomalies at rest. In other words, a significant number of the test participants were unaware that they were at risk of developing a heart condition. Moreover, the study showed that 10 percent of these participants were considered having a long QT, a severe form of the syndrome.

“Chemotherapy leads to change in cardiac muscle cells”, said Dr. Cecilia Gonzalez Corcia, expert cardiologist on the study and clinical researcher at CHU Sainte-justine. “These changes may not always be visible at rest, but can nonetheless cause anomalies when the heart muscles are under pressure, such as during an intense physical exercise.”  

This study is the first to identify and characterize childhood ALL survivors with possible aLQTS using maximal exercise testing. “Our results show the importance of including exercise testing in cardiological follow ups of pediatric cancer survivors, in particular a standardised cardiopulmonary exercise test to be completed in addition to electrocardiography and electroencephalography tests”, explains Audrey Harvey, first author of the study and doctoral student at Centre de recherche Azrieli du CHU Sainte-Justine. The study also emphasizes the need for long term medical follow-ups, especially for cancer survivors who received higher doses of chemotherapy or who underwent such treatment over a long period of time, or even for those who wish to practice a sport after their remission. Although such tests are not part of current official recommendations, the study wishes to contribute to expert consensus-building efforts on the matter in order to better prevent the onset of heart problems, improve diagnosis and thus support better health and quality of life for young cancer survivors.