Arrhythmia is a heart condition that causes electrical impulses in the heart to occur erratically. This condition can lead to sudden death. In order save the lives of people who are at risk for life-threatening arrhythmia, doctors typically implant a small defibrillator. This device can sense the onset of arrhythmia and jolt the heart back to normal rhythm. However, the defibrillator has its own health risks. There is a lot of debate circulating around the methods doctors use to decide which patients truly need this invasive and costly implant.
This debate has been going on for some time, but an interdisciplinary John Hopkins University team is working toward an answer. The team has developed a 3D virtual heart assessment tool that is not invasive. This tool will help doctors determine whether a patient faces the high risk of life-threatening arrhythmia, and therefore whether a patient needs the defibrillator implant. According to a proof-of-concept study published in the online journal Nature Communications, this new digital approach yielded more accurate predictions than the method currently used, which is an imprecise blood pumping measurement.
For his study, Natalia Trayanova, the university’s inaugural Murray B. Sachs Professor of Biomedical Engineering, joined forces with cardiologist and co-author Katherine C. Wu. Wu is an associate professor in the Johns Hopkins School of Medicine, and her research has focused on magnetic resonance imaging approaches to improving the prediction of cardiovascular risk.
The team was able to form predictions for this study using the distinctive MRI records of patients who had survived a heart attack, but as a result now have damaged cardiac tissue that predisposes the heart to life-threatening arrhythmias. The study was blinded, meaning that the team members were unaware of how closely their forecast matched the events that happened to the patients in real life until after the study. Data was taken from 41 patients who had survived heart attacks and had ejection fractions of less than 35 percent.
The ejection fraction is a measure of the amount of blood being pumped out of the heart, and physicians typically recommend implantable defibrillators for all patients with ejection fractions of less than 35 percent. All 41 patients received the implants, but research has shown that the ejection fraction score is a flawed measurement. It does not accurately predict which patients are at high risk for a sudden cardiac death.
The Johns Hopkins team used pre-implant MRI scans to create patient-specific digital replicas of their hearts. With the help of computer-modeling techniques, each replica was brought to life with representations of the communication among cells and the electrical processes in the cardiac cells. In some cases, the heart developed an arrhythmia, and in other cases, it did not. This non-invasive way to gauge the risk of sudden cardiac death has been dubbed VARP, which stands for virtual-heart arrhythmia risk predictor.
The VARP results were later compared to the post-implantation records of the defibrillator recipients in order to see how well the technology predicted life-threatening arrhythmias that were detected and halted by the implanted defibrillators. Patients who tested positive for arrhythmia risk using VARP were four times more likely to develop arrhythmia than those who tested negative. VARP also predicted the arrhythmia occurrence in patients four-to-five times better than the ejection fraction and other predictors that are currently used, both invasive and non-invasive.
Implantable defibrillators come with risks including device malfunctions, infections, and, in rare cases, heart or blood vessel damage. These risks can be eliminated by avoiding implantation of the device in patients for whom it is not truly needed.
This is a big step in helping patients with heart arrhythmia live long and healthy lives. Cardiologists often get a lot of data about patients, but ultimately don’t use much of it for individualized care. With the groundbreaking technology that allows doctors to create a personalized virtual 3D heart, cardiologists can test an individual patient’s heart virtually without doing invasive procedures.