LVAD Part I: Introduction

Left ventricular assist devices (LVADs) have moved from being a bridge to a heart transplant to destination therapy for patients with severe heart failure. Although their use in the general public has increased, they still provide a challenge to the emergency medicine (EM) physician. This series aims to cover the basics of how the EM physician approaches the care of these patients.

Some important numbers to consider:

• 5.7 million patients in the USA have heart failure, half of which will die within 5 years [1]
• LVAD use is expanding with over 22,000 being placed to date.
• With a presentation rate to the hospital of three per patient LVAD year [2,3]

Anatomy of an LVAD

There are several different manufacturers of LVAD devices and although each may have slight variations, modern LVADs function similarly enough that basic principles apply to all of them. Notably, all LVADs that can be expected to be encountered in practice currently are continuous flow. LVADs function by pulling blood from a weak left ventricle and propelling it to the (usually ascending) aorta through a pump placed between the left ventricle and aorta. There are older devices that function with the pulsatile flow but it is unlikely that any current patients have them. Of note, the newest LVAD in the US market is the HeartMate III, which has a continuous flow that increases changes speed every few seconds to provide both continuous flow and a small amount of pulse-like physiology.

The pump and circulation connections are all internal. The newer versions of LVADs work by using magnet rotors to propel the blood forward. For this reason, MRI is absolutely contraindicated in LVAD patients. A driveline connects the outside battery packs to the internal pump. Some LVAD pumps are below the diaphragm. That location may increase the risk of abdominal bacteria causing infection in and around the device. Each LVAD has a control unit that displays warnings and gives diagnostic information if an error has occurred [4].

Physical Examination

The most important physiologic change in the LVAD population is the lack of a reliable pulse, which leads to unreliable traditional blood pressure readings and pulse oximetry [3].

Physical Exam Key Points:

• Establish a baseline physical exam using pallor, capillary refill, urine output, and mental status. Watching for changes over time [3].
• The doppler mean arterial pressure (MAP) is the standard blood pressure measurement in LVAD patients. Use the standard blood pressure cuff but instead of using a stethoscope, use doppler to assess the pressure at which flow returns.
• In the absence of a Doppler device, a very rough estimate can be obtained with a stethoscope, recording the pressure at which the first (and likely only) Korotkoff sound is heard, which is considered the MAP [4].
  • There is some data to support a MAP of 70 being appropriate in LVAD patients, with some patients having lower MAP readings and maintaining adequate perfusion status.
  • A MAP goal of 60-90 is a reasonable generalization.
• Auscultation should sound like a steady high-pitched motor without clunking sounds [3].
• Invasive blood pressure monitoring with an arterial catheter is a potential option in unstable patients, but note that this will likely require ultrasound guidance with pulseless LVAD patients.
• ECG will likely have an abnormal morphology secondary to the patient’s underlying cardiac disease.
• Dysrhythmias such as ventricular tachycardia (VT) and ventricular fibrillation (VF) are still easily recognizable, accurate, and are problematic [5].

Stay tuned for upcoming posts in the LVAD series. Next up: your diagnostic workup.

For an on-the-spot clinical reference, use ALiEM’s paucis verbis card for LVAD complications.

References

1. Heart Failure Factsheet. Division for Heart Disease and Stroke Prevention. https:// www.cdc.gov/DHDSP/data_statistics/fact_sheets/fs_heart_failure.htm. Published June 16, 2016. Accessed June 11, 2018.
2. Kroekel PA, George L, Eltoukhy N. How to Manage the Patient in the Emergency Department With a Left Ventricular Assist Device. Journal of Emergency Nursing. 2013;39(5):447-453. PMID: 22595685
3. Vierecke J, Schweiger M, Feldman D, et al. Emergency procedures for patients with a continuous flow left ventricular assist device. Emergency Medicine Journal. 2016;34(12): 831-841. PMID: 27852651
4. Pistono M, Corrà U, Gnemmi M, Imparato A, Temporelli PL, Tarro Genta F, et al. How to face emergencies in heart failure patients with ventricular assist device. Int J Cardiol. 2013 Oct 15;168(6):5143–8. PMID: 23992932
5. Sen A, Larson JS, Kashani KB, Libricz SL, Patel BM, Guru PK, et al. Mechanical circulatory assist devices: a primer for critical care and emergency physicians. Crit Care. 2016 Jun 25;20(1):153. PMID: 27342573

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