A left ventricular assist device (LVAD) is a mechanical pump that physicians can implant in patients with heart failure, to help the ailing heart move blood from its lower chamber to the rest of the body and vital organs. The LVAD doesn’t replace the heart, but it can buy time until the patient receives a heart transplant, or as is becoming more common, it serves as a permanent “destination therapy” that helps the damaged heart heal.
The LVAD is still relatively new, approved for use within the last decade. The device is essentially a propeller that spins inside a housing to push blood through the body. When a person gets an LVAD, they no longer have a heartbeat; instead, it’s replaced by a continuous flow of blood. This changes the basic physiology of the body, and doctors are just beginning to understand its long-term affects on the body.
The pressure created inside blood vessels from the continuous pressure of the pump produces what’s called “shear stress.” This creates a risk for bleeding, because the shear stress can strip away proteins that are needed to help close and heal openings in the blood vessels. On the other hand, the plastic and metal materials of the pump itself can introduce a risk of clotting as well.
These risks complicate the decision to implant an LVAD for any patient, but for those with preexisting hematological abnormalities, or blood conditions that already put them at risk for clotting or bleeding, the decision is even more complicated. And Nir Uriel, MD, Director of the Heart Failure, Transplant and Mechanical Circulatory Support program at the University of Chicago Medicine, says patients who have some other condition in addition to heart failure, or comorbidity, are really the norm.
“There’s a reason why they had a heart attack, because they already had a hematological problem that causes clotting, for example,” he said. “Unfortunately we are really behind in catching up with the technology. We’re still learning the new physiology created by this technology, so that’s the first step to understanding the interaction with comorbidities.”
In a paper recently published in the Journal of Heart and Lung Transplantation, Uriel and his colleagues from Columbia University Medical Center in New York reviewed data on 286 patients who received and LVAD over 5 years at Columbia, and found 12 who also had serious hematological abnormalities. These patients were at a much higher risk for bleeding, blood clots, stroke and early mortality than those without prior hematological conditions, leading the researchers to question the use of LVADs in such cases.
“We should ask ourselves, ‘Is this the right therapy for these patients?’” said Uriel. “We don’t want to treat our patients to death, we want to offer them the best treatment that will give them the best quality of life.”
Unfortunately for patients with severe heart failure in need of the LVAD, it’s often their last hope. If they don’t get a pump, doctors can treat them with IV medications, but ultimately it becomes palliative care before death. Uriel said it’s a catch-22 decision: implant a device that could extend their life, but introduce the chances of serious complications that lead to very poor quality of life in that added time. His hope is that technological advances will mitigate some of the risk for these patients by decreasing the pressure and shear stress generated by the pumps, leading to a range of choices for patients depending on their comorbidity risk.
“I truly believe that in order for technology to thrive in the right patients, you need to understand that not all patients are equal,” he said. “Some of them have one disease, some of them have others, and we need to match the right patient to the right technology.”