Cardiac & Resuscitation, Industry News, Industry News, Operations, Patient Care

The High-Tech Heart: LVAD emergencies in pre-transplant patients

You and your partner are just finishing up shift change with the off-going shift when you’re dispatched to a local golf course for a person down. En route, you’re informed that an elderly patient has collapsed on the golf course and appears not to be moving. On arrival, you find the patient lying on his side with his wife kneeling beside him. As you interview the man, he tells you he passed out while preparing to tee off on the eighth hole.

The patient appears pale and diaphoretic but reports that he’s feeling better. The wife tells you her husband is a heart failure patient and is being treated with a special device that helps his heart pump stronger.

Background

On Dec. 2, 1982, the world’s first artificial heart was implanted into Barney Clark, a retired dentist. During a surgery that lasted more than seven hours, Dr. William DeVries implanted the device developed by Dr. Robert Jarvik of the„University of„Utah. Made of Dacron polyester, plastic and aluminum, the device was called the Jarvik-7.

The Jarvik-7 had an internal power system that regulated the pump through a system of compressed air hoses connected to the chambers of the heart. Its power system drove the pumps, which moved blood through the patient’s body.„Clark survived for 112 days before succumbing to multiple organ failure.1

In 1991, the FDA placed a moratorium on the use of the Jarvik device, citing high incidence of thromboembolic events, severe infections and low survival rates. Since then, the development of an implantable left ventricular assist device (LVAD) has been in evolution by several different manufacturers.2 In 1994, the FDA approved the first such device as a ˙bridgeÓ to cardiac transplantation.3

In the decades following the first FDA-approved LVAD, technological advances have produced lightweight wearable systems for patients awaiting cardiac transplantation. Patients can now be discharged from the hospital while waiting to undergo cardiac transplantation, which reduces medical expenses and improves the patient’s quality of life. Research on patients who have been discharged from the hospital with an LVAD has shown an increase in survival rates following cardiac transplantation due to the hemodynamic and clinical benefits of mechanical assistance and their ability to convert high-risk, terminally ill patients into stable, reconditioned heart transplant recipients.4,5

Medical Indications

Cardiovascular disease remains the leading cause of death in the„U.S., accounting for 40% of deaths annually. Advances in the control and treatment of the disease and improved treatment modalities for acute myocardial infarctions (MIs) have reduced mortality, but the death rate from congestive heart failure (CHF) is increasing.6

Affecting five million people in the„U.S., CHF is the leading cause of hospitalization and costs the health-care system a reported 38 billion dollars each year.7

The pathophysiology of CHF is progressive, beginning with a decrease in ventricular function, which leads to a decrease in cardiac output, causing hypotension, pulmonary congestion and inadequate tissue perfusion. As the disease progresses, compensatory mechanisms cause vasoconstriction, which increases the workload of the heart and leads to enlargement of the heart and further decompensation.

CHF is described in four stages:

>„Stage A: high risk with no symptoms;

>„Stage B: structural heart disease without symptoms;

>„Stage C: structural disease with previous or current symptoms; and

>„Stage D: refractory symptoms requiring special intervention.

Mechanical support devices, such as LVADs, are intended for use on patients who are in stage D heart failure.6 Patients with Stage D heart failure exhibit symptoms of cardiac insufficiently at rest and would be unable to carry out physical activity without discomfort. These patients are also considered to have a life expectancy of less than two years.

Treatment strategies for heart failure include lifestyle modifications, medication regimens, treatment of co-morbidities (such as hypertension), cardiac rhythm management and coronary artery bypass grafting. Patients in Stage D are left with few treatment options, including continuous infusions of inotropes, transplantation, hospice or LVAD placement.6

According to the FDA, approximately 4,000 people in the„U.S. await heart transplants each year, but during a typical year only about 2,200 donor hearts are made available.8 Because the demand for donor hearts is greater than the supply, such alternative therapy as the LVAD is significant. LVADs are now being seen as a safe, cost-effective measure to bridge a patient to cardiac transplantation.2

Device Specs

Ventricular assist devices consist of an implanted blood pump, external system controller and external power supply components (see Figure 1, p. 60). The blood pump and its mechanism can vary depending on which device the patient has implanted; however, all pumps can mimic a natural heart’s cardiac output of nearly 10 L of blood flow per minute and up to 120 beats per minute.

Microprocessors located in the system controller initiate motor actuation, monitors system performance and serve as the primary interface for the entire system. The system controller has two modes of operation, either auto or fixed rate. When the device is set to the fixed-rate mode, the pump will eject at a pre-set number of beats per minute, independent of pump volume status. This mode is usually used in the operating room and on some patients at night.

To more accurately imitate a natural heart, the auto-rate mode is more often used. The auto-rate mode will signal the pump to eject when the chamber is approximately 97% full of blood. It’s in this mode that the LVAD is responsive to physiologic demand; it can either speed up or slow down according to pre-load to the LVAD. Practitioners will most likely find the majority of patients set to this mode.

The final component of the system is the power supply system. Power enters through the system controller either from a pair of wearable batteries or from a dedicated power supply that can be plugged into a wall outlet.9

The LVAD is implanted in the abdomen and is attached parallel to the cardiovascular system. Blood is channeled into the assist device by way of an inflow conduit attached at the tip of the heart’s left ventricle. Once blood empties into the pump, the system controller triggers the pump to eject the blood through an outflow graft attached to the aorta. The outflow graft bypasses the left ventricle and channels blood directly into the aorta. Valves located on either side of the device ensure blood can flow only in one direction.

When the LVAD is functioning in the auto-rate mode, the device is designed to respond to changing flow demands of the body. If a patient’s activity level increases, the device will increase cardiac output to meet metabolic demands. At rest, when flow demand lessens, flow through the device will also decrease.9

Prehospital Care

Technology now allows patients discharged from the hospital after LVAD placement to live within the community while they await a donor heart. This strategy has shown to improve post-transplant survival and increase the quality of life for the patient living with Stage D heart failure.3 Given that these patients are living independently, prehospital providers can be the first to encounter these patients in times of crisis and are challenged to provide appropriate care.

Emergencies can arise for several reasons, including problems with the LVAD system itself or further deterioration of the patient’s underlying disease process. Because the LVAD has taken over the function of the left ventricle, any disruption of flow from the device will decrease peripheral blood flow, creating a shock-like syndrome, which predisposes the patient to serious consequences.

Fortunately, education is an extremely large focus for the patient and family before and after an LVAD placement.10 Often, hospitals will coordinate educational efforts with an assigned social worker and the ˙ventricular assist team,Ó which is typically composed of advanced practice nurses and or nurse practitioners. Education begins prior to surgery and intensifies after the LVAD has been placed, up to the time of discharge.

Many educational topics are covered with the patient and their families, including operation of the LVAD and performing daily system checks, power supply connections and options, care of the surgical site and how to change dressings, important nutritional and exercise guidelines, medication regimens and, most important, emergency operation and power failure procedures to activate the device in times of loss of power or battery function.10

Power failures:„ The LVAD system can be supplied power from specially designed batteries or an AC power base unit. While relaxing or sleeping, the patient often uses the power base unit, which can double as a battery charger. Some LVAD devices come with hand pumps, which are designed to supply power in case of a power outage. The hand pump is intended to pneumatically operate the LVAD by shuttling air in and out of the system, thus continuing to pump blood through the system.

Patients are instructed to always have a hand pump available in case of emergencies.11 Hand pumping is covered in depth with the patient and their families prior to hospital discharged. Patients and their families should be well prepared for these types of emergencies, and„EMS providers may simply need to provide some assistance or reassurance until hand pumping can be established. However, you may need to perform hand pumping during transport to the facility.

A patient experiencing a power failure with their LVAD will present with signs and symptoms of hypovolemia, right-sided heart failure, pulmonary hypertension and possibly arrhythmias from decreased blood flow to the myocardium. Treatment should focus on supplying power to the LVAD by either helping the patient or family member switch batteries or connecting to an alternative means of AC power. The final option is to initiate hand pumping if the particular device can accommodate it.

Malfunctions:„ Mechanical malfunctions of an LVAD are always a possibility. Patients who experience these conditions may notice more frequent alarms emitting from the system controller, an increase or decrease in flow rates, unusual noises (such as grinding or screeching), and new or unusual sensations as the system continues to operate.

If a mechanical malfunction is suspected, first assess the patient and determine if the LVAD is functioning properly. If the LVAD is functioning and the patient is stable, continue treatment using your standard medical protocols and transport to a local emergency department.11

If the patient has experienced an LVAD failure and is unstable, continue with your medical protocols and consider transport directly to the implant center. Use of hand pumping in a mechanical malfunction may be considered; however, depending on the device and malfunction, hand pumping may not be effective, and treatment may need to focus on the patient’s presenting complaint or condition.

CPR & other treatment:„ Due to the location of the LVAD and its proximity to the heart, there may be risks associated with performing chest compressions. CPR may damage the LVAD itself or dislodge tubing, resulting in massive hemorrhage. The use of hand pumping in place of CPR is possible and may be indicated in some situations. Decisions on whether or not to use CPR should be left to medical control.11

Further treatment considerations focus on physiologic changes related to their underlying disease process, such as dysrhythmias, electrical therapy (defibrillation/cardioversion), ACLS or trauma care. The use of electrical therapy depends on the make/brand of the LVAD. Keep in mind that the patient and family will be well versed in emergency procedures and know how to manipulate the LVAD system in case of an emergency.

The patient and family will also be educated on which kind of therapy the patient can or cannot receive, so emergency care providers should always keep the patient and their caregivers together during treatment and transport.

Transport:„ Use of aeromedical transport may be considered, depending on the length of transport and the patient’s condition. Every attempt should be made to contact the patient’s doctor or emergency contact person to identify the nearest implant or transplant center. Patients should then be transported to that identified center by the most appropriate means of transportation. All modes of transportation are acceptable; aviation electronics will not interfere with the LVAD (or vice versa). Having the patient’s companion nearby will also help in identifying the closest treatment facility and modes of transportation.11

Summary

Returning our attention back to the case scenario in the introduction, your assessment revealed that the patient had some type of power interruption of his LVAD and, as a result, had a syncopal episode due to decreased cardiac output. The patient and his wife informed you of the nearest LVAD center and requested he be transported there immediately.

Cardiovascular mechanical support devices are a relatively new science, with the first LVAD being introduced less than 15 years ago. In September 2006, the Abiomed Corp.,„Danvers,„Mass., obtained FDA approval (under humanitarian device exemption) for the AbioCor, the first completely self-contained replacement heart. Abiomed continues to develop an implantable replacement heart with the goal of creating an artificial heart that has a five-year reliability.

As technology and research continues to advance in creating an artificial heart, we as prehospital providers must also continue to learn how to care for these patients in the ever-changing landscape of medical technology.12 Further considerations for caring for LVAD patients focus on continuing education and awareness of local ventricular assist programs in your area. Continuing education can occur by contacting your local ventricular assist program or hospital and requesting additional training and or literature.

In addition, when LVAD patients are discharged home, they’re often instructed to notify their local„EMS agency in writing; take the opportunity to meet the patient and their family to learn more about the equipment and how to prepare for an emergency whenever your agency is notified of such a patient in your service area.10

Additionally, the Thoratec Corp. (manufacturer of the Heartmate LVAD) presents a sample LVAD assessment protocol adapted from an algorithm used by„LDS„Hospital in„Salt Lake City (see Figure 2, p. 61). The algorithm approaches emergencies in a simplified manner, starting with whether the LVAD is functioning and proceeding with treatment and transport considerations.11

References

  1. ˙Inventor of the Week Archive: Artificial Heart.ÓLemelson-Mit Program.„http://web.mit.edu/invent/iow/jarvik.html.
  2. Goldstein DJ, Oz MC, Rose EA. ˙Implantable left ventricular assist devicesÓ.„New England Journal of Medicine 1998;339:1522-1533.
  3. Rose EA, Gelijns AC, Moskowitz AJ. ˙Long-term mechanical left ventricular assistance for end-stage heart failureÓ.„New England Journal of Medicine 2001;345:1435-1443.
  4. Jessup M. ˙Mechanical cardiac support devices: Dreams and devilish detailsÓ.„New England Journal of Medicine 2001;345:1490-1492.
  5. Renlund GD. ˙Building a bridge to heart transplantationÓ.„New England Journal of Medicine 2004;351:849-851.
  6. Jessup M, Brozena S. ˙Medical progress: Heart failureÓ.„New England Journal of Medicine 2003;348:2007-2018.
  7. Copeland JG, Smith RG,„Arabia FA. ˙Cardiac replacement with a total artificial heart as a bridge to transplantationÓ.„New England Journal of Medicine 2004;351:859-867.
  8. Michelle Meadows. ˙Artificial heart helps people awaiting transplants.ÓUnited States Food and Drug Administration.„www.fda.gov/fdac/features/2005/105_heart.html.
  9. Thoratec Corp. ˙Heartmate XVELVAS Operating ManualÓ.„www.thoratec.com/medical-professionals/heartmate_lvas.htm.
  10. Sorbellini D, Williams J, George T. ˙Portable ventricular assist devices: Pumping up failing heartsÓ. Nursing 2005;35:321-324.
  11. Thoratec Corp. ˙Heartmate XVELVAS Patient HandbookÓ.„www.thoratec.com/medical-professionals/heartmate_lvas.htm.
  12. Abiomed Corporation. ˙Products: Heart replacementÓ.„www.abiomed.com/products/heart_replacement.cfm.
Wayne A. Riddle, RN, CFRN, PHRN, has been involved in EMS for more than 10 years, as both a flight nurse with PennSTAR flight, Hospital of the„University of„Pennsylvania,„Philadelphia, and as a firefighter/PHRN with the Berwyn Fire Company,„Berwyn,„Pa.