"About 85% of children with cancer survive, but the next question is how they can survive healthy in adult life," Tsuda said. "Even those children who are quite healthy in childhood can develop long-term cardiac-toxicity disorder, including stroke, decades after their cancer."

He said often the toxicity can cause very serious and irreversible cardiac issues for the patient later in life. These issues can present later as adults with fibrosis, thrombosis, arrhythmias and issues with cardiomyocyte contractility. Some of these issues can lead to heart failure.  

The issue is that pediatric cancer patients often recover quickly after treatment and seem just fine, and the toxicity issues do not reveal themselves until decades later. 

The study presented at AHA looked at using cardiopulmonary exercise stress testing to see if it can detect abnormalities in asymptomatic pediatric cancer patients. Poor exercise performance in the study was mainly attributed to limited stroke volume reserve, but the underlying pathophysiology is multifactorial. This included patients with high body mass index (BMI) not performing as well.

He said toxicity is often tested in cancer patients using echocardiograms. While this test is good at showing damage that already occurred, it is not predictive of future health. So, he said serial echo exams are needed to look for any changes in cardiac function over time. 

For this reason, Nemours created a cardio-oncology clinic to track pediatric cancer patients as they age. Tsuda said part of the reason for the clinic appointments is to remind patients of their responsibilities for life style choices, with the understanding that they are at higher risk for cardiac issues later in life. He said these regular patient encounters are important, because pediatric patients often want to move on with their life and not be reminded of being very sick as a child. But, he said it is important for these patients not to be lost to followup. 

"They want to forget about it, and this is another problem," Tsuda explained. "Sometimes they get to college age and they don't know what their disease was or what kind of treatment they received, such as if they received radiation or chemotherapy. And that is information they need to know. But, because of their reluctance to remember the bitter past, they tend not to remember these critical things."

While the underlying mechanisms that cause long-term cardio toxicity are not fully understood, Tsuda said recognizing cardiac issues, when they do develop, is important for earlier treatment to avert permanent damage to the heart if left untreated. This may include better nutrition, exercise and lifestyle changes.