5 Things Pharmacists Should Know About Patients with Left Ventricular Assist Devices

While heart transplantation is the mainstay surgical modality for patients with advanced heart failure, the number of heart transplants performed worldwide has remained steady at around 3000 per year since the early 2000s.¹

This shortage of organs is particularly problematic, given that heart failure continues to remain a leading cause of death in the United States, and the annual mortality rate for those with end-stage heart failure is around 50%.

In light of the significant disparity between the number of patients who need a heart transplant and the dearth of donor organs, left ventricular assist devices (LVADs) have emerged as a lifesaving treatment option for those with advanced heart failure. While early pumps were large and prone to mechanical failure, newer continuous flow devices like Thoratec’s HeartMate II LVAD and HeartWare’s HVAD Pump boast 1-year survival rates around 90%.²

Use of these devices both as bridges to transplantation and permanent therapy in those who are not eligible for a transplant has recently exploded. In fact, more than 15,000 US patients have been implanted with a continuous flow LVAD since 2008.²

As a result, pharmacists in all health care settings have likely encountered a patient with an LVAD, or will do so in the near future. Here are the top 5 things every pharmacist should know about caring for patients with LVADs.

1. All Patients with LVADs Should Be Taking Warfarin.

Similar to those with mechanical heart valves, all patients with LVADs will require anticoagulation with warfarin for the duration of their device support.

Although all of the commercially available pumps are made from titanium, which is the most biologically inert metal around, they can still form clots. Thrombosis within the pump motor could be catastrophic, as it may cause the device to fail and result in the return of overt heart failure symptoms or even cardiogenic shock. Clots within the pump may also embolize, and stroke is a major concern for patients on LVAD support.

While the optimal intensity of anticoagulation remains to be determined, most patients’ international normalized ratio (INR) goal should be 2.0 to 3.0. Because of the superimposed risk of bleeding that comes with LVAD support, however, some patients may have more narrow INR targets, such as 2.0 to 2.5.³

Maintaining such a narrow target is often very difficult, and pharmacists who care for these patients should be extra diligent in counseling them about the importance of adherence to drug therapy and dietary recommendations pertinent to warfarin-based anticoagulation.

Unfortunately, novel oral anticoagulants (NOACs) like dabigatran have not been studied in the LVAD population, so they cannot be used in these patients. Pharmacists should therefore question any NOAC prescriptions for LVAD recipients.

2. All Patients with LVADs Should Be on Antiplatelet Therapy.

In addition to warfarin-based anticoagulation, patients with LVADs should be on a daily aspirin regimen to protect against thrombosis. The dose varies based on the type of device; patients with HeartMate II generally take lower doses (eg, 81 mg daily), while HeartWare HVAD recipients require higher doses (eg, 325 mg daily).³

Patients with LVADs are also at a higher risk for bleeding while on device support, so some of them may not be taking aspirin because of a history of hemorrhagic complications. Pharmacists caring for these patients should always ensure proper compliance with aspirin regimens, especially since this medication can be purchased over the counter.

In some instances, patients may be taking 2 antiplatelet agents, the second of which is usually dipyridamole based on early HeartMate II trial data. However, agents like clopidogrel can be used in rare circumstances, such as in patients who develop thromboembolic complications despite adequate treatment with warfarin and aspirin.³

3. Measuring Blood Pressure Is Tricky in Patients with LVADs.

Because both of the commercially available LVADs operate using continuous flow, patients on device support will not have a palpable pulse. Indeed, most patients with LVADs no longer have a systolic or diastolic blood pressure.

As such, blood pressure must be measured in the physician’s office using a Doppler probe to determine the patient’s mean arterial blood pressure (MAP). The goal MAP for most patients is around 70 mmHg, and values above 90 mmHg should be avoided because hypertension in LVAD recipients is associated with a heightened risk for stroke.

In general, medications used for hypertension in regular heart failure patients can also be safely used in those under LVAD support. Pharmacists should therefore ensure that safe medications (eg, amlodipine) are used, while unsafe medications (eg, verapamil) are avoided.

4. Heart Failure Drug Therapy Should Still Be Used, If Possible.

Practicing pharmacists likely learned a long time ago that angiotensin-converting enzyme (ACE) inhibitors and beta-blockers should be prescribed to all patients with heart failure and a reduced ejection fraction. Whether this paradigm holds true for heart failure patients on LVAD support has not be formally studied, however.

For patients who are being bridged to heart transplant, the use of these medications to reduce morbidity and mortality is probably less important, as the duration of device support is likely going to be between 6 and 12 months, depending on the health system and the patient’s characteristics. For non-heart transplant candidates who will remain on device support for the rest of their lives, the value of these medications remains murky.

While no current data suggest that ACE inhibitors or beta-blockers will prolong life or prevent hospitalization in these patients, most medical experts would prefer to use these medications in long-term LVAD patients, unless a specific contraindication exists. Pharmacists involved in the care of LVAD recipients should therefore evaluate each patient’s candidacy for ACE inhibitor and beta-blocker therapy, as well as encourage the use of these agents when appropriate.

5. Patients with LVADs Are Prone to Infection.

Currently available LVADs run on battery power and are connected to the controller module through a percutaneous driveline. Unfortunately, this driveline presents a breakdown in the body’s natural defense, putting patients at constant risk for infection.

These infections typically remain localized to the area of the driveline and would therefore be characterized as complicated skin and soft tissue infection. On occasion, however, these infections can spread to the bloodstream, and even the device itself can become seeded similar to endocarditis. The epidemiology of these infections is broad and can include Gram-positive, Gram-negative, and fungal pathogens.⁴

Given the severe nature of these infections, alongside the fact that the LVAD is often their source, patients will often need to stay on antibiotics for the duration of device support. Pharmacists must therefore be careful when screening these patients for potential interactions between antibiotics and warfarin, as well as counsel them on complying with antimicrobial therapy in order to avoid treatment failure and the spread of infection.

Conclusion

Contemporary LVADs are a lifesaving treatment for patients with advanced heart failure, and the use of this technology is rapidly expanding. As key members of the health care team and experts in pharmacotherapy, pharmacists must be familiar with these devices and their associated complications.

Opportunities exist for pharmacists to assist with optimizing thromboprophylatic drug therapy regimens, using heart failure medications appropriately, and ensuring safe and effective antimicrobial treatment.

References

1. Yusen RD, et al. The Registry of the International Society for Heart and Lung Transplantation: Thirty-second official adult lung and heart-lung transplantation report--2015; focus theme: early graft failure. J Heart Lung Transplant. 2015;34:1264-1277.

2. Kirklin JK, et al. Seventh INTERMACS annual report: 15,000 patients and counting. J Heart Lung Transplant. 2015;34:1495-1504.

3. Jennings DL, et al. Assessing anticoagulation practice patterns in patients on durable mechanical circulatory support devices: an international survey. ASAIO J. 2016;62:28-32.

4. Gordon RJ, et al. Prospective, multicenter study of ventricular assist device infections. Circulation. 2013;12(127):691-702.