Cancer survivors are more likely to die from heart disease than cancer, and therefore patients must be closely monitored for heart problems during and after cancer treatment. Such surveillance can be done continuously with new implantable cardiac monitoring devices.
The need for cardiac monitoring is evidenced by estimates of heart failure in cancer patients during chemotherapy; such estimates range from 3% to 50% depending on the drugs used. And the risk of heart disease remains long after the treatment is finished. “When caring for cancer survivors, it’s important to recognize their vulnerability to atrial fibrillation and heart failure caused by previous chemotherapy and to be vigilant for these heart problems,” said Jean-Bernard Durand, M.D., an associate professor in the Department of Cardiology at The University of Texas MD Anderson Cancer Center.
Treatment-related heart problems
Chemotherapy and radiation therapy can increase the risk of cardiovascular problems such as severe hypertension, cardiomyopathy, ischemia, atrial fibrillation, and congestive heart failure. Chronic cardiotoxicity can occur within weeks of treatment or up to 20 years after treatment.
The cardiac side effects of systemic drugs vary. Cytotoxic chemotherapeutic drugs such as doxorubicin (and other anthracyclines) cumulatively weaken the heart muscle. Biologic therapies such as trastuzumab also can weaken the heart muscle during treatment, but trastuzumab-related cardiomyopathy is often reversible with medical therapy. Taxanes and other chemotherapeutic drugs cause abnormal heart rhythms during treatment in some patients. And angiogenesis inhibitors can cause blood pressure spikes and increase the risk of blood clots and heart failure.
Radiation therapy can trigger long-term cardiac effects if the heart is incidentally exposed to radiation. These long-term effects include coronary artery disease, damage to the heart valves, damage to the heart’s electrical system, heart muscle stiffening, and inflammation.
Implantable cardiac monitors such as the CardioMEMS system and the Reveal LINQ system can provide diagnostic information that can help physicians monitor patients constantly and remotely to detect cardiac events before they become serious.
The Reveal LINQ system, used to detect abnormal heart rhythms and to monitor unexplained fainting, is implanted just under the skin in the chest in an outpatient procedure that takes less than 5 minutes. Patients also receive a bedside machine that collects the heart data and sends the data to a central database and directly to the smartphone of the implanting physician. If patients notice a cardiac event symptom, they can press a button on the bedside machine to send a report to the database instantly. Physicians can program the device by setting parameters for how often data are downloaded and what ranges of abnormal heart rhythms warrant notification of the physician and patient by database monitors.
Dr. Durand uses the Reveal LINQ system to monitor patients around the world. When a patient in Dubai experienced palpitations, Dr. Durand was able to call him to discuss his symptoms. The patient took a beta blocker and thus avoided a trip to the emergency department. “Patients are monitored and cared for 24/7; even halfway around the world, my patients can feel comfortable knowing that their hearts are constantly being monitored and that I’m always there for them, at any time,” Dr. Durand said.
This system also allows physicians to help patients associate what they feel with the data that document cardiac events. Dr. Durand said, “Patients are often surprised to receive a call from the database service when their heart rates are abnormal. Implantable cardiac monitors help patients understand that they don’t necessarily perceive heart rate spikes.”
The Reveal LINQ device can collect data for up to 3 years, but Dr. Durand said that most patients’ heart conditions can be diagnosed with 60 days of monitoring after cancer treatment. However, Dr. Durand said, “Most patients like keeping the device until the battery runs out because it’s like a safety net.”
Unlike the Reveal LINQ device, the CardioMEMS system does not use batteries and can monitor arterial pressure and heart rate throughout a patient’s lifetime. The CardioMEMS device, about the size of a paperclip, is permanently implanted in the pulmonary artery during a right heart catheterization procedure. The device monitors pressure in the pulmonary artery and transmits data wirelessly to an external electronic system, and then the data are transmitted directly to the physician. “I can monitor patients on my cell phone,” Dr. Durand said. “Once I noticed a 10% increase in arterial pressure in a patient. I called him and advised him to take a water pill; we caught the problem quickly enough to avoid a trip to the emergency room.”
Implanted cardiac monitoring devices have several advantages over traditional external monitoring devices. Implanted devices continuously record data for years, whereas external devices are used for short-term data collection (1–30 days). With implanted devices, patients are not encumbered by recording pads or wires. Finally, implanted devices allow physicians to analyze data from before, during, and after cardiac events and to track patterns over time.
Dr. Durand and his team currently are conducting two studies involving implantable cardiac monitoring devices in cancer patients. In a retrospective study, Dr. Durand and his colleagues are investigating how many patients who qualify for implantable cardiac monitoring devices have been approached by physicians about this possibility.
In a clinical trial that will soon begin enrolling patients, Dr. Durand and his colleagues will investigate whether Reveal LINQ devices can help cancer patients with atrial fibrillation continue chemotherapy; if the devices detect an early potential heart problem and the problem is addressed, patients may be able to continue life-saving treatments instead of temporarily halting chemotherapy, which is the current standard practice.
Dr. Durand said that cancer patients and survivors with unexplained episodes of passing out, palpitations, or frequent visits to the hospital with symptoms of heart failure may qualify for implantable cardiac monitoring devices as part of the diagnosis and treatment of their heart conditions. Dr. Durand said, “These devices can help patients continue chemotherapy and can help cancer survivors avoid trips to the emergency room, which is important because hospital visits make patients more vulnerable to developing blood clots, pneumonia, or drug-resistant bacterial infections.”
Two implantable cardiac devices—Reveal LINQ (top), which detects abnormal heart rhythms, and CardioMEMS, which monitors heart rate and arterial pressure—enable physicians to monitor patients remotely in real time. Image courtesy of Dr. Jean-Bernard Durand.
MD Anderson is the only cancer center in the world with a fully integrated cardiac device program for cancer patients. In addition to Dr. Durand, the team consists of Kaveh Karimzad, M.D., an associate professor in the Department of Cardiology, who is one of the only oncoelectrophysiologists in the world; Marc Rozner, M.D., Ph.D., a professor in the Departments of Anesthesiology and Perioperative Medicine and Cardiology, who studies the use of imaging modalities and radiation therapy for cancer patients with implanted cardiac monitors; and Darla Labasse, R.N., a cardiac device specialist in the Cardiopulmonary Center.
For more information, contact Dr. Jean-Bernard Durand at 713-792-6239.
OncoLog, March 2016, Volume 61, Issue 3