One of the cardinal rules of radiation oncology has been “avoid hitting the heart.”
In cancer treatments, for instance, high-dose radiation is used to target tumors while always taking great care to spare surrounding healthy tissue – particularly in the heart region.
But a novel therapy that uses focused stereotactic radiation to assist in cardiac ablation is proving to be an exception to that rule. By targeting scar tissue that causes rapid, abnormal heartbeats (ventricular tachycardia), this noninvasive radiation treatment has provided relief for high-risk heart patients – many of whom have run out of other options.
UT Southwestern is the only center in North Texas currently offering cardiac radioablation, and it took two years of collaboration between a cross-section of our specialists – from cardiac electrophysiologists and radiation oncologists to medical physicists, radiologists, and heart imaging experts – to begin delivering this novel therapy to our patients.
So far, results have been excellent and the procedure, which requires significant prep and planning time, takes only about 20 minutes. Patients are able to go home the same day. But it’s important to note that this new therapy isn’t going to replace standard cardiac ablation. Rather, it is a viable and exciting alternative for some of our most vulnerable patients.
Fixing problems in the heart’s electrical system
Cardiac arrhythmias, or heart rhythm disorders, range from harmless palpitations to life-threatening conditions.
Dr. Richard Wu and Dr. James Daniels are cardiac electrophysiologists at UTSW who specialize in treating cardiac arrhythmias. Over the last few years, they have worked closely with physicians at Washington University in St. Louis, where cardiac radioablation was developed specifically to treat one of the most serious arrhythmias, ventricular tachycardia.
Also referred to as V-tach or VT, ventricular tachycardia is a faster than normal heart rate caused by abnormal electrical signals in the lower chambers (ventricles) of the heart. It is often seen in patients who’ve had a prior heart attack or congestive heart failure, because scar tissue forms on a section of their heart muscle.
In some patients, the scarring may include entrapped, damaged muscle fibers that can still conduct electricity, albeit more slowly than normal. This abnormal electrical signaling can lead to significantly increased heart rates. Left untreated, VT can lead to worsening heart failure and even sudden cardiac death.
Most patients who have been diagnosed with VT will get a device implanted in their chest called an implantable cardioverter-defibrillator, or ICD, which can detect a dangerously rapid heartbeat and deliver a “shock” to return the heart’s rhythm to normal. Defibrillators can be monitored by cardiologists remotely and during clinic visits to check on the progression or regression of the abnormal rhythms.
Standard cardiac ablation
Whereas some arrhythmias can be controlled with medications or a defibrillator, cardiac ablation may be recommended to treat persistent cases of ventricular tachycardia.
A minimally invasive procedure, cardiac ablation is done with a catheter (a thin, flexible tube) to access the heart and apply heat or extreme cold to destroy the abnormal areas of the heart and disrupt the abnormal electrical signals traveling through the heart. The procedure, which typically takes four to six hours and may require monitoring in the intensive care unit afterward, allows the heart’s electrical system to function normally again.
Cardiac ablation is successful for most patients, but there is a 20 to 50 percent recurrence rate of VT. And for some patients, particularly those who are very ill, elderly, or suffering from other medical problems, catheter ablation may be too risky.
For those high-risk patients, noninvasive cardiac radioablation is a breakthrough alternative.
Combining cardiac ablation with radiation
Until just recently, applying a potent dose of radiation to a healthy heart would have be unthinkable, according to Dr. Robert Timmerman, M.D., Vice-Chair of Radiation Oncology at UTSW. But thanks to advances in stereotactic treatment technologies and cardiac imaging, we are now able to target scar tissue on the heart that is causing dangerous arrhythmias.
The work of two physicists in our Department of Radiation Oncology, Dr. Xuejun Gu and Dr. Weiguo Lu, has been essential to making this possible at UTSW. They developed image fusion software that allows our cardiologists and radiation oncologists to locate and ablate the scar tissue with extreme precision.
Using the most advanced technologies, such as the TrueBeam linear accelerator, we have been able to deliver cardiac radioablation to several patients so far and it has dramatically reduced the frequency of their VT episodes.
In broader studies on the use of noninvasive cardiac radioablation, the burden of arrhythmia seems to decrease quickly within the first few weeks. Clinical trials at Washington University involving 19 patients showed the treatment led to a 94 percent reduction in VT in the first six months, and that effect persisted for 78 percent of trial participants for more than two years.
Because this is an emerging therapy, we will continue to monitor our patients closely and refine our radiation doses and techniques. We plan to participate in national multicenter studies on cardiac radioablation as well.
In the meantime, we are excited about the promising possibilities that cardiac radioablation can offer to some of our patients who need it most. To talk to a specialist about cardiac radioablation, call 214-645-8300 or request an appointment online.
