{"id":112,"date":"2013-07-15T03:56:36","date_gmt":"2013-07-15T03:56:36","guid":{"rendered":"https:\/\/edecmo.org\/?page_id=112"},"modified":"2014-05-08T11:39:31","modified_gmt":"2014-05-08T15:39:31","slug":"lvads","status":"publish","type":"page","link":"https:\/\/edecmo.org\/additional-technologies\/ventricular-assist-devices-vads\/lvads\/","title":{"rendered":"Overview of Left Ventricular Assist Devices (LVADs)"},"content":{"rendered":"
This page was authored by Chris Partyka. It was originally published on the amazing Blunt Dissection Blog and based on a fantastic review article by Dr. Partyka.<\/p>\n
These are intricate mechanical pumps utilised in the management of end-stage cardiac failure refractory to aggressive medical therapy, typically bridging a patient to cardiac transplantation.<\/p>\n
The first implantation of an LVAD occurred back in 1984, however their technology and success have markedly improved since then. The landmark REMATCH paper demonstrated significant survival increase [52% vs 25% at 1 year, p=0.002] with an improved quality of life. Currently over 90% of LVAD-supported patients will survive to 1 year post-implantation.<\/p>\n
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The assessment of a patient with a VAD begins like any other; a primary survey !! However, there are a few specifics we should mention.<\/p>\n
Due to diminished [& sometimes absent] peripheral pulses in the continuous-flow VADs, standard non-invasive blood pressure is difficult [perhaps impossible] to obtain.<\/p>\n
Blood pressure can be measured with (1) a manual\u00a0sphygmomanometer & (2) Doppler ultrasound over the radial or brachial artery. Cuff pressure is gradually reduced until a constant sound is heard \u2013 signifying the\u00a0mean arterial pressure<\/em>. Alternatively, in a critically ill patient just place an ultrasound-guided arterial line !<\/p>\n In this case the patients\u2019 mean arterial pressure was measured at 59 mmHg. He normally runs at 70-80mmHg.<\/p>\n Click on over to the LVAD Troubleshooting Page to find out<\/a><\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n Ventricular assist devices are implanted medical equipment to augment cardiac output. Left ventricular assist devices (LVADs) are the most common version you will encounter.<\/p>\n Currently, the best review article is (Crit Care Med 2014;42:158<\/a>)<\/p>\n and this article is great as well (Clinical Management of VADS<\/a>)<\/p>\n These devices augment the left ventricular flow for patients in severe congestive heart failure (CHF).\u00a0 The recent popular form of this is through an internal pump and an external power supply.\u00a0 These are connected through a driveline that exits the body through the right upper quadrant of the abdomen.<\/p>\n The indications for LVAD placement are patient with severe CHF limiting activities of daily living and often times requiring home inotropes to maintain perfusion.\u00a0 Strict indications for implantation exist in United States for medicare reimbursement.\u00a0 These include New York Heart Failure class 4 with ejection fraction less than 25%.<\/p>\n The LVAD has two cannulas.\u00a0 The inflow cannula is inserted into the left ventricle apex and draws blood into the pump.\u00a0 The pump has had various forms over the years.\u00a0 Initial LVAD models were pulsatile.\u00a0 While this concept succeeds in keeping with the body\u2019s natural flow and may consequently have some physiologic benefits, continuous non-pulsatile pumps have become standard.\u00a0 These types of pumps have the advantage of better durability as the pulsatile pumps required many moving parts.\u00a0 Each of these parts were susceptible to failure.\u00a0 Decreasing the number of moving parts has therefore become paramount with the most recent model claiming zero moving parts.<\/p>\n Beyond the pump lies the outflow cannula which connects the pump to the aorta.\u00a0 This allows blood to be drawn out of the left ventricle and pumped into the aorta without need for left ventricle induced flow.\u00a0 The outflow cannula is attached to aorta such that coronary flow is maintained along with the periphery.<\/p>\n Exiting the pump is the driveline.\u00a0 This exits the body in the right upper quadrant and attaches to the controller.\u00a0 The controller attaches to two batteries.\u00a0 All three of these components are held in a vest-like garment or belt that allows the patient to be mobile when desired.\u00a0 The controller contains the electronic circuitry required to maintain desired revolutions per minutes (rpm).\u00a0 It also records adverse events and decreased flow periods with the machine.\u00a0 It additionally has advanced functions to deal with specific LVAD problems like suction events and power shortages.<\/p>\n LVAD patients pose an interesting physiology not seen in other patients.\u00a0 The design of the machine allows the left ventricle to still function normally.\u00a0 This means some blood will exit the left ventricle (LV) through the aortic valve secondary to the native heart function.\u00a0 The level of LV function and the compliance of the aorta will determine the pulsatility of the patient.\u00a0 Due to low levels of LV function and the continuous nature of current generation pumps, most patients will not have a palpable pulse.\u00a0 Additionally, most standard automatic blood pressure machines will not be able to determine the correct blood pressure on these patients.\u00a0 A manual blood pressure will usually be successful at determining the mean arterial pressure (MAP) without a significant pulse pressure.<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" This page was authored by Chris Partyka. It was originally<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":443,"menu_order":0,"comment_status":"closed","ping_status":"open","template":"","meta":{"jetpack_post_was_ever_published":false,"footnotes":""},"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/P3JzC4-1O","_links":{"self":[{"href":"https:\/\/edecmo.org\/wp-json\/wp\/v2\/pages\/112"}],"collection":[{"href":"https:\/\/edecmo.org\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/edecmo.org\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/edecmo.org\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/edecmo.org\/wp-json\/wp\/v2\/comments?post=112"}],"version-history":[{"count":0,"href":"https:\/\/edecmo.org\/wp-json\/wp\/v2\/pages\/112\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/edecmo.org\/wp-json\/wp\/v2\/pages\/443"}],"wp:attachment":[{"href":"https:\/\/edecmo.org\/wp-json\/wp\/v2\/media?parent=112"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}<\/a>
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2) ASSESSING DEVICE FUNCTION.<\/strong><\/h3>\n
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3) A BEDSIDE ECHO CAN BE A VERY POWERFUL TOOL.<\/strong><\/h3>\n
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The GOLDEN RULE OF VADS<\/h2>\n
Call your nearest LVAD or Cardiac-transplant center as soon as possible for assistance in the care of these complex patients !!<\/em><\/h3>\n
So what can be causing his hypotension?<\/h3>\n
\nIndications<\/i><\/h4>\n
Device Functions<\/i><\/h4>\n
LVAD physiology<\/i><\/h4>\n
next see LVAD Problems and Troubleshooting<\/a><\/h3>\n