LVAD = Tight Sphincter
July 17, 2017
Of course, it would be great if you could read the full text of all the articles we cover. But I am seriously recommending this one to you. Many have written summaries on LVADs. Now the AHA weighs in and covers the most important stuff. You will benefit from this AHA review article guaranteed. LVADs scare the **** (expletive deleted) out of us, and we need to have a better understanding of how to troubleshoot when they’re not working right. Get free full text here. More mechanical circulatory support devices are being placed as a bridge to transplant or as a permanent fixture. As such, more of these people are showing up at our door. This document summarizes how these devices work and what to do when things go wrong or these patients arrest.
How LVADs Work
LVADs siphon blood out of the LV and use a continuous flow pump (in most) to push blood through a conduit into the aorta, just above the aortic valve, creating hemodynamically stable PEA – an odd physiological state. They usually have no pulse. Non-invasive BP is done with a Doppler device; as the BP cuff is deflated, the first sound of continuous flow in the vessel is the mean arterial pressure. BTW, don’t push down too hard with the Doppler.
What Goes Wrong
The most common problems are power disruption to the pump, usually dead batteries. Or the driveline, which powers and controls the pump has been damaged, crushed, or cut (watch those trauma shears!). Also, anything that impairs RV function will decrease flow into the LV, such as tamponade, tension pneumothorax, massive PE, increased pulmonary pressure, ischemia, VT/VF, or even profound dehydration. Clots may form in the pump and cause hemolysis, so all patients are anticoagulated. Also, Thomas (our peer-reviewer) said, “Unfortunately, these patients develop AVMs easily and therefore live on a hematologic tightrope made of a single thread of fibrin.” Great word picture!
Other problems include infection of the drive line in up to 30% of long-term patients. Also sepsis, GI bleeding, stroke, or intracranial bleed may cause syncope and no pulse, creating confusion about whether or not to initiate chest compressions if the patient remains altered. You can quickly assess BP as described above, check skin perfusion, and measure EtCO2 via ETT. As a matter of fact, EtCO2 <20 and other signs of poor perfusion with unconsciousness would be an indication to start chest compressions.
If any LVAD patient is unconscious with no signs of life, chest compressions should be initiated. It is critical to bring all the patient’s supplies, including extra batteries and the plug-in power supply, as most receiving hospitals are not VAD centers and do not have any back up equipment. Even if they are a VAD center, they may not have compatible equipment. Listen for the mechanical hum over the chest. If none, check all the connections and power supply. If no improvement, ask the trained family member to replace the system controller. If no LVAD function and the patient is unconscious with low EtCO2 and MAP <50, start standard ACLS.
In the ED
Memorize all of the above. But we can also use bedside echo to quickly assess the IVC to see if volume might help. See if the RV is working. Check for large pericardial effusion.
Total Artificial Heart
In a total artificial heart, the heart has been removed and replaced with a gadget. Note, this is NOT the same as a LVAD. These are pulsatile devices; in contrast to the LVAD, “no pulse” here is always bad. The ECG shows asystole because they are like the Tin Man – they don’t have a heart; chest compressions don’t work at all. Epinephrine will spike afterload and cause pulmonary edema. The only options if unconscious with poor perfusion are to unkink drivelines, check power supply, give 1 L of NS, and trained individuals can change the controller. ACLS drugs, vasopressors, and defibrillation all don’t work and are contraindicated. Elevated BP greater than 150 systolic readily causes pulmonary edema and should be treated with nitroglycerin, furosemide, and many patients use prn oral hydralazine.
LVADs and other mechanical circulatory support devices are increasingly used. We need to know the basics of how they work and how to troubleshoot them. This full text article is a must read.
Every major FOAM blog has something on LVADs. Here is the FOAM-a-paloosa:
- REBEL EM has an outstanding post.
- Mayo has a great review for the ED.
- EMCrit has an insanely good review and audio.
- emDocs has an awesome, comprehensive, yet brief post.
- Canadiem has a swell post to boot.
Cardiopulmonary Resuscitation in Adults and Children With Mechanical Circulatory Support: A Scientific Statement From the American Heart Association. Circulation. 2017 Jun 13;135(24):e1115-e1134. doi: 10.1161/CIR.0000000000000504. Epub 2017 May 22.
Peer reviewed by Thomas Davis.