LVAD Basics

In depth

The one-page summary above is what the PDF prints. These sections go further.

Continuous-flow physiology: why the pulse pressure narrows

A durable LVAD drains the LV apex and returns blood to the ascending aorta, in parallel with the native heart. The rotor runs at one fixed speed, so flow depends on the head pressure across the pump (aortic minus LV pressure): when the native LV contracts, head pressure falls and pump flow rises; in diastole flow falls. That swing is the pulsatility index (PI).

Unloading through the whole cycle lowers LV end-diastolic, wedge and left atrial pressures. Output is pump flow plus whatever the LV still ejects through the aortic valve, which in a well-unloaded ventricle opens intermittently or not at all. Diastolic pressure is held up by continuous flow and systolic pressure is barely augmented, so pulse pressure narrows to roughly 10 to 20 mm Hg: the pulse is weak or absent, oscillometric cuffs and oximeters fail, and the Doppler opening pressure stands in for MAP.

The pump is preload dependent, moving only what reaches the LV, so bleeding, RV failure, tamponade or an arrhythmia that stalls the RV all cut flow, and an emptied ventricle collapses onto the cannula (suction). It is afterload sensitive: at a fixed speed a higher MAP means less flow, and centrifugal pumps have flatter pressure-flow curves than the axial HeartMate II, so hypertension costs them more.

The pump family: HeartMate 3, HeartMate II and HVAD

HeartMate 3 (Abbott) is a centrifugal pump with a fully magnetically levitated rotor, wide flow gaps, textured titanium surfaces and an artificial pulse that Abbott describes as a drop of about 2,000 rpm for 0.15 second, then a rise of 2,000 rpm above set speed for 0.2 second, every 2 seconds, to wash the pump. It sits inside the pericardium, and the modular driveline can be replaced at its connector.

HeartMate II, an axial pump on mechanical bearings, carried the field from 2008 to 2017 and produced its worst device problem: pump thrombosis at three months rose from 2.2% to 8.4% between 2011 and 2013 (Starling, NEJM 2014). HVAD was withdrawn in June 2021 over failures to restart and a higher stroke rate, leaving several thousand patients on a pump no longer sold. Both still use aspirin and have different controllers and alarms.

Selection, implant and the early postoperative course

Candidates have stage D failure despite guideline therapy: NYHA IIIb to IV, LVEF 25% or less, and inotrope dependence or a peak VO₂ below about 14 mL/kg/min. INTERMACS profiles grade acuity from 1 (critical shock) to 7; most implants are profiles 2 and 3. Destination therapy is roughly 80% of US implants in STS INTERMACS reports since the 2018 allocation change.

• RV function decides the outcome. Warning signs: CVP above 15 mm Hg or a CVP to wedge ratio above 0.63, PAPi below about 1.85, RV stroke work index below 300 to 400 mm Hg·mL/m², TAPSE under 14 mm, severe tricuspid regurgitation, rising bilirubin.
• Contraindications: irreversible RV failure without a biventricular plan, irreversible end-organ disease, active infection, inability to take warfarin, and a situation that cannot support the device.

The inflow cannula is cored into the apex aimed at the mitral valve, the outflow graft sewn to the ascending aorta and the driveline tunneled to the upper abdomen. The team ramps the speed under transesophageal echo until the septum is midline and the aortic valve opens intermittently; that speed is the baseline you trend against.

The first week is about the right ventricle. Unloading pulls the septum leftward and removes its help to RV contraction while pump flow raises venous return to an RV still facing high pulmonary pressures; it dilates, the LV under-fills, and flow and PI fall with a high CVP. INTERMACS counts right heart failure as needing an RVAD, prolonged inhaled vasodilator or inotropes beyond 14 days, about a quarter of trial patients. Keep CVP in the low teens, add milrinone or dobutamine, use inhaled nitric oxide or epoprostenol, avoid high speed, and move to a temporary RVAD before end organs fail.

Reading the controller and measuring the blood pressure

The screen shows speed, flow, power and PI; only speed and power are measured. Flow is calculated from power and speed with a hematocrit correction and PI from the flow waveform, so whatever distorts power distorts both. No adult normal range is published; the ACTION guide lists flow 3 to 6 L/min, power 3 to 6 W and PI 3 to 5, and each program records the patient's own baseline.

PI is the swing between peak and trough flow against mean flow, averaged over about 15 seconds. A sudden drop against its running average triggers a PI event: speed falls to the team-set low-speed limit so the ventricle can refill, then ramps back without an alarm; each event is logged. A suction event is the clinical version: flow and PI fall, PVCs or VT appear as the cannula irritates the septum, and echo shows a small LV pulled toward the cannula. Restore preload and treat the cause; the team may lower speed, and nobody raises it.

Rotor thrombus adds friction, so power climbs over hours to days or spikes, and because flow is calculated from power the display shows a falsely high flow in an underperfused patient. Hemolysis gives it away: plasma free hemoglobin above about 40 mg/dL, rising LDH, low haptoglobin, tea-colored urine. Aortic insufficiency also raises power and displayed flow, because the regurgitant volume really passes through the pump, but without hemolysis and with a large LV and a jet on echo. Outflow graft obstruction goes the other way: low flow with low or flat power.

Blood pressure is a Doppler skill: manual cuff, Doppler over the brachial or radial artery, inflate until the signal disappears, deflate slowly, and the pressure at which it returns is the opening pressure, which approximates MAP when the pulse pressure is narrow and sits nearer systolic when a pulse is palpable. ISHLT 2023 targets a MAP of 75 to 90 mm Hg (Class IIa) and treats sustained values above 90 with oral antihypertensives, because hypertension cuts flow and predicted stroke in the HVAD trials; Abbott and the ICCAC EMS guide give slightly different ranges.

Alarms, power and the backup controller

HeartMate 3 alarms are two-tiered: red hazard alarms with a continuous tone mean the pump has stopped or is about to; yellow advisories with an intermittent beep need attention within minutes. The silence button quiets a hazard briefly and an advisory for hours, and fixes nothing.

The pump needs one live source at all times: pull one battery, replace it, confirm the controller shows power, then change the other; the Mobile Power Unit is the same, one lead at a time. Pulling both stops the pump instantly. A charged pair of 14-volt batteries lasts about 10 to 17 hours.

1. Controller change (for a failed controller or when the VAD center directs): sit or lie the patient down, because the pump stops briefly.
2. Connect the backup controller to power first; it alarms until a pump is attached.
3. Unlock the driveline from the failed controller, seat and lock it in the backup; the pump restarts.
4. Confirm the hum, the speed and the patient, unplug the old controller, and tell the coordinator how long the pump was stopped.

Complications: bleeding, stroke, infection, RV failure

Bleeding is the most frequent adverse event: in MOMENTUM 3 about 44% of HeartMate 3 patients bled by two years and a quarter bled from the gut. Shear inside the pump unfolds large von Willebrand multimers so ADAMTS13 cleaves them, an acquired von Willebrand syndrome present in nearly every continuous-flow patient, and low pulsatility promotes angiodysplasia in the stomach, duodenum and small bowel.

Hold warfarin (and aspirin in HeartMate II or HVAD patients), reverse only for life-threatening bleeding with a high INR, and scope early. For recurrent bleeding ISHLT 2023 lists a lower INR target, octreotide and thalidomide as options with thin evidence.

Driveline infection reaches about one patient in four by two years with no difference between pumps. It starts where movement tugs the velour against skin, and the organisms are skin and water flora: Staphylococcus aureus, coagulase-negative staphylococci, Pseudomonas and enteric gram-negatives. Prevention is mechanical: a stabilizer so the line never moves at the skin, sterile dressing changes per protocol, chlorhexidine, showers only with the kit once the tract matures, no submersion ever. Spreading redness, pus, tract tenderness or fever means cultures, imaging and prompt antibiotics; deep infection means months of therapy, debridement and a higher transplant priority.

Arrhythmias, arrest and transport

Ventricular arrhythmias occur in a third to a half of patients in the first year. Because the LV is drained mechanically, sustained VT or even VF can be tolerated for a time; what fails is the RV, so preload, flow and PI fall and suction follows over minutes to hours. Replace potassium and magnesium, give volume if the LV is small, start amiodarone or lidocaine, and cardiovert or defibrillate normally with pads clear of the pump and the controller connected. ISHLT 2023 allows no more than 30 minutes of VT or VF.

In an arrest the second rescuer looks before touching: hum over the left chest, the screen, any red alarm, both power leads, the driveline seat. Pump off with power intact is a controller or driveline problem; a running pump with no perfusion is upstream (hypovolemia, RV failure, tamponade, PE, tension pneumothorax, hypoxia) or downstream (sepsis, anaphylaxis, overdose, intracranial bleed). Epinephrine, amiodarone and shocks are given as usual.

• Record speed, flow, power, PI and alarms with the time before moving; measure MAP by Doppler, not an automated cuff.
• Secure the driveline with the stabilizer and route it away from straps; place pads and leads clear of the pump; keep the patient on batteries with the backup controller in reach.
• Go to the implanting center when possible and call its coordinator from the scene and before any procedure. No MRI; CT and ultrasound are fine.

Daily nursing care, documentation and life after the pump

• Neuro: level of consciousness, pupils, speech and motor symmetry hourly in the ICU, each shift on the floor; any change is a stroke until imaged.
• Cardiovascular: controller readings at least every four hours and with any change, against the documented baseline; MAP by arterial line or Doppler; CVP, rhythm, pump hum, skin and capillary refill, edema, daily weight.
• Respiratory, renal, hematology: oximetry is a hint, ABG when in doubt; hourly urine output early, and tea-colored urine means hemolysis; INR daily until stable, CBC, LDH and plasma free hemoglobin at baseline and with any change in power or flow.
• Driveline and equipment: exit site inspected at each dressing change for erythema, drainage, warmth and tract tenderness, dressing dated, stabilizer on; both leads connected, spare batteries and backup controller at the bedside, alarm log reviewed, set speed matching the order.
• Documentation: the four readings, PI events, alarms with action taken, MAP method, exit-site description, anticoagulant and INR.

Three paths follow. Transplant: under the 2018 US allocation a stable LVAD patient sits at status 4, can take 30 days at status 3, and rises to status 2 for device infection, malfunction, thrombosis, intractable arrhythmia or RV failure. Destination therapy: median survival with HeartMate 3 exceeds five years in trial follow-up. Recovery: a few percent, mostly young nonischemic or myocarditis patients, wean; the speed is turned down under echo, and typical explant criteria are an LVEF above 40 to 45%, LVEDD under about 55 mm, wedge under 15 mm Hg and cardiac index above 2.4 at minimal support.

Evidence and controversies

ENDURANCE Supplemental (2018) added a blood pressure protocol with a MAP target of 85 or less to the HVAD trial, cut HVAD strokes, and is the main evidence behind today's MAP targets.

MOMENTUM 3 (Mehra, NEJM 2017 to 2019) randomized 1,028 bridge and destination patients to HeartMate 3 or HeartMate II. At two years survival free of disabling stroke or pump reoperation was 76.9% versus 64.8%, driven by thrombosis (1.4% versus 13.9%), reoperation (2.3% versus 11.3%) and stroke (9.9% versus 19.4%); GI bleeding fell (24.5% versus 30.9%) but stayed common, and two-year survival was similar (about 79% versus 77%). Five-year follow-up (JAMA 2022) separated the curves: 58.4% versus 43.7%. ARIES-HM3 (Mehra, JAMA 2023) randomized 628 HeartMate 3 patients on warfarin to aspirin or placebo; placebo did at least as well on the hemocompatibility composite (about 74% versus 68% event-free) with roughly a third less bleeding, and the FDA label changed in August 2024.

ISHLT 2023 (Saeed, JHLT) is the reference guideline: MAP 75 to 90, warfarin to an INR of 2.0 to 3.0 (it still lists aspirin, predating ARIES), speed for intermittent valve opening, compressions when perfusion is inadequate, and a 30-minute limit on VT or VF.

Unsettled: whether aspirin-free therapy extends to HeartMate II and HVAD; whether the postoperative heparin bridge helps or only bleeds; the exact MAP ceiling; and how to prevent de novo aortic insufficiency.

Exam pearls

• No pulse is not arrest. Assess perfusion: Doppler MAP over 50, PETCO₂ over 20 via an endotracheal tube, warm skin, normal capillary refill; impaired perfusion gets compressions (AHA 2025).
• Low flow with low PI after bleeding or in RV failure is a preload problem: volume or blood, never more speed.
• Rising power with high LDH, plasma free hemoglobin and dark urine is pump thrombosis, and the calculated flow reads falsely high; rising power without hemolysis and a dilated LV is aortic insufficiency.
• MAP is the Doppler opening pressure with a manual cuff; ISHLT 2023 targets 75 to 90 mm Hg. Hypertension lowers pump flow and raises stroke risk.
• RV failure after implant: high CVP, low flow, low PI. Inotropes, inhaled nitric oxide or epoprostenol, avoid high speed, RVAD if refractory.
• HeartMate 3 anticoagulation is warfarin to an INR of 2.0 to 3.0 without routine aspirin since August 2024 (ARIES-HM3); HeartMate II and HVAD patients still take aspirin.
• Defibrillate normally with pads clear of the pump and the controller connected; ISHLT 2023 allows no more than 30 minutes of VT or VF.
• MOMENTUM 3 at two years: survival free of disabling stroke or pump reoperation 76.9% with HeartMate 3 versus 64.8% with HeartMate II.