British societies guideline on the management of emergencies in implantable left ventricular assist device recipients in transplant centres

We recommend placing an immediate cardiac arrest call if any LVAD recipient is found unresponsive and/or not breathing normally. Cardiac arrest calls can also be placed for any deteriorating LVAD recipient and/or where a staff member is concerned and if there are delays in contacting specialist help. In some advanced heart failure centres, activation of an “LVAD cardiac arrest call” will lead to the 24/7 on-call specialist VAD nurse being contacted who can provide prompt expert guidance. In UK hospitals cardiac arrest team activation is through a standardised phone number “2222”, which we were therefore incorporated into this national algorithm.

We debated the timing of CPR extensively during the process of design and testing of the algorithm. There are surgical concerns around a risk of anastomotic rupture during chest compressions as the LVAD outflow graft lies in close proximity to the sternum. However, the limited evidence available suggests this risk may have been overestimated particularly in the late post-operative phase [6‐8]. The dominant issue is the fact that contemporary rotary LVADs have a non-occlusive (valve-less) blood path. Thus, when the LVAD stops working, retrograde blood flow can occur from the aorta via the non-functional LVAD, into the left ventricle. The retrograde LVAD flow not only compromises systemic (and hence cerebral) perfusion, particularly if residual left ventricular function is very poor but also limits the efficacy of CPR. However, despite these limitations, in the face of persistent LVAD failure, CPR would be expected to augment systemic perfusion, albeit to a limited extent. Thus, we recommend a delay of a maximum of 2 min whilst attempting to restore LVAD function (which is the most effective resuscitative tool available) prior to the initiation of CPR.

If a single responder is present, the priority after calling for help should be to diagnose and promptly treat LVAD dysfunction, if possible. This is equivalent to early CPR in standard life support. This change in focus from resuscitating the patient to restarting the machine addresses the importance of a functioning pump as the best chance of restoring adequate circulation in device dysfunction. The second responder, who normally will arrive promptly in the hospital setting, should focus on the standard ‘Airway’ then ‘Breathing’ approach to patient assessment and attach electrocardiographic monitoring as part of the ‘Circulation’ step.

The first action of the initial responder, after calling for help, is to review the information displayed on the LVAD controller screen to guide subsequent actions. LVADs have a range of visual hazard advisories which are displayed on the controller and are accompanied by various audible alarms. These allow the patient/staff to distinguish between low, medium and high priority alarms [18, 19]. We have specified alarms according to the screen text display that could potentially be associated with a resuscitation episode to guide lifesaving interventions.

This can be a normal operational state of the Heartmate III LVAD so the initial step is to depress any button on the controller to activate the screen. If the screen of either the Heartmate III or HVAD continues to be blank after a button is depressed, the LVAD is either (a) completely depleted of power and must be connected to a functional power source, or (b) controller has failed and must be replaced.

This can be indicative of the presence of a thrombus within the pump which impinges between the rotating impeller and the pump housing and will require confirmation by blood tests (plasma haemoglobin and lactate dehydrogenase), LVAD log file analysis, and echocardiography. Based on these findings, a clinical management plan can subsequently be devised. If the pump thrombosis episode is associated with inadequate circulation, immediate temporary mechanical circulatory support e.g. veno arterial ECMO (VA-ECMO) or salvage thrombolytic therapy may be considered.

The percutaneous LVAD driveline may have become disconnected and will need to be reconnected to the controller. Alternatively, the driveline may have a modular component (Heartmate III) that has become disconnected. Consequently, exposure of the entire driveline is mandatory to allow observation of such a disconnection. A third possibility is driveline fracture from mechanical fatigue or damage, which, if detected, should be managed by gentle manipulation to try and restore electrical continuity. If this manoeuvre is successful, the driveline should be immobilised temporarily with adhesive tape until specialist engineering support can be provided. If the driveline is completely severed, there is no simple remedial intervention to restore electrical continuity.

This requires replacement of a rechargeable battery with a charged battery or connection of the controller to mains power.

For the HVAD and Heartmate II and III, blood flow rate is not directly measured but is estimated from LVAD electrical power consumption and blood viscosity using either the haematocrit or packed cell volume as a surrogate. For a given impeller rotation rate, the blood flow generated by the LVAD is inversely proportional to the pressure difference across the LVAD, i.e. aortic minus left ventricular pressure. Thus, paradoxically, relative hypotension is desirable in LVAD recipients because it is associated with the preservation of adequate LVAD blood flow which not only assures adequate perfusion but minimises the risk of thrombogenesis in the LVAD. This is best achieved through maintenance of mean arterial blood pressure (MAP) in the 60–80 mmHg range. A low LVAD blood flow alarm is likely to be caused by inadequate LVAD filling, the most common cause being hypovolaemia [20] which is frequently attributable to dehydration or more rarely, bleeding (e.g. gastrointestinal). The primary intervention in response to suspected hypovolaemia should be a passive leg raise, which, if effective, can be followed by cautious intravenous fluid administration (e.g. 4 ml/kg) targeting a MAP above 60 mmHg [21]. Haemorrhage management requires an individualised balanced approach with due consideration of the severity of bleeding and risk of pump thrombosis [22]. In severe bleeding or that occurring in sensitive compartments, such as the brain, reversal of anticoagulation is almost always indicated. In the case of haemorrhagic cardiac arrest a standardised major haemorrhage protocol with balanced transfusion and reversal of coagulation with specific agents or blood products is necessary.

An alternative cause of a low LVAD flow alarm is right ventricular failure, to which further fluid administration could be detrimental. The recognition of right ventricular failure will require historical review of investigations such as echocardiography and right heart catheterisation data. In the immediate setting, echocardiography is likely to be the most rapid route to diagnostic assessment. If available, invasive monitoring such as significantly elevated central venous pressure or pulmonary artery catheter data can also support diagnosis of a volume overloaded state and the subsequent avoidance of intravenous fluid administration.

The low flow alarm can also be activated in response to an excessive LVAD afterload. If the peripheral or invasive MAP > 90 mHg and alternative causes of low flow above are assessed and excluded, antihypertensive medication should be administered such as intravenous hydralazine, sodium nitroprusside or glyceryl trinitrate.

A rarer cause of low flow is a restriction to blood flow within the LVAD blood path, e.g. thrombus or a partially occluded LVAD inflow/outflow. It is managed in a similar manner to pump thrombosis which impinges between the impeller and pump housing resulting in a refractory LVAD power increase. A low flow alarm may also occur because of torsion, compression or kinking of the LVAD outflow graft. This requires surgical correction.

Arrhythmias can also trigger low flow alarms, either through left ventricular preload reduction and/or left ventricular cavity obliteration (a suction event).

Although ventricular arrhythmias are associated with poor outcomes in LVAD recipients, they may be well-tolerated in the short term due to maintenance of perfusion by the LVAD [23]. This can result in a patient retaining cerebral responsiveness despite ventricular tachycardia (VT) or ventricular fibrillation (VF). In the presence of an adequate circulation, chemical cardioversion can be attempted in VT. Patients are also likely to have implantable cardioverter defibrillators which can be used to deliver anti-tachycardia pacing. If the VT rate falls below programmed detection boundaries, then the VT zone can be reprogrammed by the pacing team to deliver this therapy.

When electrical cardioversion or defibrillation is being considered, sedation must be implemented if patient shows signs of consciousness. Contemporary LVADs are not susceptible to damage from defibrillation or cardioversion. Antero-posterior pad positioning is preferred as the LVAD is connected to the left ventricular apex and is likely to lie in the antero-lateral pad vector although this is not invariably the case.

If there is inadequate circulation and the patient is unresponsive, then defibrillation should be implemented without delay with three stacked shocks, if required.

After LVAD troubleshooting has been attempted and VF/VT has been treated, the adequacy of circulation should be confirmed. LVAD recipients with a normal circulation will be responsive, not centrally cyanosed, have a normal capillary refill (< 3 s), MAP > 60 mmHg [21] and have a normal end tidal carbon dioxide (ETCO₂); which we have defined as being > 2 kPa in an intubated patient in accordance with other published CPR guidelines [13]. Ultimately, the LVAD should have a normal controller display without active audible and visual alarms, typically with a flow rate > 3 L/min in adults. LVAD hum should be audible on auscultation of the chest.

If there is adequate circulation, staff should undertake a standard ‘Airway, Breathing, Circulation, Disability, Exposure’ assessment. A persistent reduction in the level of consciousness and/or respiratory arrest in spite of an adequate circulation is strongly suggestive of an acute neurological event, e.g. stroke [21]. Patients in a low cardiac output state, with borderline adequacy of circulation should be considered for inotropic infusions to increase intrinsic cardiac output although excessive vasoconstriction should be avoided as an elevated systemic vascular resistance limits LVAD flow.

If the circulation remains inadequate, high-level specialist expertise is required. Although the parameters of adequacy of circulation can be assessed, clinical judgement is imperative in the LVAD recipient. We chose not to be prescriptive as even potentially reliable parameters, such as ETCO₂, may not be failsafe, for example, in the case of a loose-fitting facemask or laryngeal mask airway. If the patient is within 10 days of LVAD implantation, the Cardiac Advanced Life Support (CALS) algorithm should be followed [24] with chest reopening, if indicated.

In the absence of a Do Not Attempt Resuscitation (DNAR) order and following confirmation of inadequate circulation, CPR should be started either with a view to replacement mechanical circulatory support system or to maintain circulation during assessment and treatment of 4Hs (Hypoxia, Hypothermia, Hypovolaemia, Hyper/Hypokalaemia) and 4Ts (Thrombosis, Toxins, Thromboembolism Tension pneumothorax) according to ALS guidance such as thrombolysis for pump thrombosis [25].

Replacement devices include the Abiomed Inc. Impella (Danvers, USA), VA-ECMO or another implantable LVAD. Randomised evidence for emergency ECMO initiation in out-of-hospital cardiac arrest (non-LVAD related) is well established and ECMO flow should be initiated within 60 min of the onset of arrest [26, 27]. Temporary mechanical circulatory support presents technical challenges including retrograde flow through the dysfunctional LVAD which may require outflow graft occlusion device, e.g. an Abbott Inc Amplatzer (Chicago, USA).

Mechanical CPR devices are associated with a lack of reliable safety data in LVAD recipients [28]. Pragmatically they have a demonstrated role in prolonged cardiac arrest and during the institution of emergency ECMO. Mechanical CPR is unadvisable in certain high risk patient groups such as those with chest wall deformities and elderly women [29].

Echocardiography can be of utility in determining the cause of cardiac arrest, such as right ventricular failure, suction events, tamponade, or intracardiac thrombus. However, it is reliant on a competent sonographer being available at the time of the emergency and acoustic windows may be limited. Thrombus within the LVAD pump housing cannot be visualised by echocardiography and so this remains an adjunctive investigation in our algorithm rather than a treatment-determining criteria.

Importantly patients with LVADs who require CPR have a very poor outcomes [6] which raises ethical questions around whether management should focus allowing death with dignity rather than administering extreme interventions. These are considerations that should be discussed with patients when they are well enough to consider their wishes and should be written into advanced care and treatment escalation plans.