Recommendations for the Use of Mechanical Circulatory Support: Ambulatory and Community Patient Care: A Scientific Statement From the American Heart Association

Controller Display Parameters

On the device controller, a display reports parameters that can be considered device “vital signs.” These include the speed (revolutions per minute), power (Watts), and flow (liters per minute; Figure 2A and 2B and Table 3).

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Figure 2.

A and B, Display monitors.

A, HeartWare Controller. Reproduced with permission from HeartWare. B, HeartMate II controller. HeartMate II, HeartMate 3, and St. Jude Medical are trademarks of St. Jude Medical Inc or its related companies. Reproduced with permission of St. Jude Medical. Copyright © 2017. All rights reserved.

The device is adjusted by the implanting center to optimize LV unloading and to provide the best combined cardiac output (CO). The CO is contributed by both the MCS device and native heart flow. The speed remains fixed unless manually reprogrammed by the MCS center. The power required is measured and recorded. Typically, higher revolutions-per-minute speeds correlate with higher power. The flow is calculated with device-specific algorithms. The HeartMate II device displays an additional pulsatility index parameter, which reflects the change in device flow over the cardiac cycle.

Returning to Normalcy

Many signs and symptoms of heart failure (eg, shortness of breath, paroxysmal nocturnal dyspnea, and fluid weight gain) abate fairly soon after surgery. Other symptoms may resolve over a longer period of time (eg, fatigue, poor energy level, and decreased strength).⁵ Thus, early mobilization and rehabilitation are important to a successful recovery. Aggressive physical and occupational therapy should begin as soon as possible after MCS surgery, and cardiac rehabilitation should continue beyond hospital discharge.⁶

A patient’s return to a normal life after discharge includes incorporation of MCS self-care (eg, changing power sources) into his or her daily routines. Family caregiver support is an important component of self-care. Family caregivers who are also trained to assist with troubleshooting alarms typically change driveline exit dressings and address potential equipment malfunctions.

After discharge, patients with MCS adjust to performing activities of daily living (eg, bathing, dressing, sleeping, home management, and work) and engaging in leisure activities. Most patients identify bathing as a key component of normalcy. Submersion in a bathtub and swimming are prohibited with these electrically powered devices; however, the manufacturers have developed accessories that allow patients to shower once the driveline site has healed adequately. Sleeping requires planning so that equipment is set up in the bedroom and allows nighttime trips to the bathroom. Patients adapt to sleeping with the controller and finding comfortable positions for sleep, given the presence of the pump and drive line. In addition, resumption of work, more strenuous activities (including leisure activities), and sexual intimacy may be challenging.^5,7

Driving is also an important activity for many patients who undergo device implantation because it promotes independence, reduces caregiver burden, and facilitates social interaction. Patients cite the ability to drive as a major contributor to improved quality of life.⁸ Eligibility for driving should be determined by the individual center, taking into consideration the patient’s recovery from debility and local laws. Factors to be considered are the potential impact of the sudden deployment of a supplemental restraint system (airbag) against a passenger or driver with an implanted device⁹ and the presence of an implantable cardiac defibrillator (ICD). Furthermore, the potential for sudden pump malfunction, change in level of consciousness, and driver distraction by alarms may pose a risk to the patient who is driving, passengers in the vehicle, and others on the road.

Anticoagulation

Anticoagulation with warfarin is required for all continuous-flow devices; however, the level of anticoagulation may vary by center, practice, and device type.^10,11 Antiplatelet therapy with aspirin and often a second antiplatelet agent is necessary because of the threat of stasis, thrombosis, shear-induced platelet dysfunction, and hemolysis. Upregulation of platelet function is described with MCS and may contribute to long-term risk of thromboembolic events.^12,13 In the case of subtherapeutic international normalized ratio, the necessity of bridging is patient specific and should be guided by the implanting center.

Hypertension and Hypotension

Titration of medical therapy to maintain a mean arterial blood pressure in the normal range is imperative to optimize forward flow and to prevent adverse events.^6,8,14 Hypertension after ventricular assist device (VAD) implantation is common, and an increase in diastolic pressure with a continuous-flow device may exacerbate or lead to hypertension.¹⁵ Increased afterload decreases pump flow and increases the risk of neurological events and end-organ damage.^6,8,14 Neurohormone-modifying agents such as angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, β-blockers, and mineralocorticoid receptor antagonists are used to decrease afterload, to improve pump function, and to potentially contribute to ventricular recovery. Diuretics are frequently prescribed to manage symptoms of right ventricular (RV) failure and fluid retention. Hydralazine/nitrates and phosphodiesterase type 5 inhibitors such as sildenafil and tadalafil may also be used for RV failure and pulmonary hypertension.¹⁶

Renal Failure

Renal insufficiency is common in end-stage heart failure. After MCS implantation, 67% of patients have been reported to experience improved renal function.¹⁷ Hemodialysis is complicated yet occasionally possible with special consideration of hemodynamics, anticoagulation, and volume assessment. Continuous veno-venous hemodialysis and inpatient intermittent hemodialysis are relatively common in the early postoperative recovery period. Similar outcomes in bridge-to-transplantation patients with a left VAD requiring hemodialysis and those not needing renal replacement therapy have been reported.¹⁸ The availability of outpatient hemodialysis centers with the capacity of offering outpatient therapy is essential for the patient with MCS to achieve hospital discharge after surgery, and renal failure requiring dialysis is often an impediment to hospital discharge. Successful peritoneal dialysis is reported but at this time is not routine practice.¹⁹

Diabetes Mellitus

Close serum glucose control is essential to reduce postoperative infection and progressive diabetes mellitus-related end-organ dysfunction. Insulin requirements may change significantly when the patient develops increased functional capacity, appetite, and nutrient absorption. Poor glucose control influences a patient’s transplantation candidacy.²⁰

Psychosocial, Behavioral, and Cognitive Problems

Patients may be evaluated for MCS implantation as an outpatient or while hospitalized. Evaluation includes a rigorous clinical and psychosocial/behavioral assessment. Patients also learn more about their diagnosis and prognosis, MCS risks (eg, adverse events) and benefits (eg, lengthening life and improving quality of life), and reasonable alternatives and their associated risks and benefits. Patients, in turn, share their preferences for care, goals in life, and what they hope to gain from MCS therapy with their families and clinicians. The intention of informed consent is to document shared decision making.

Debilitating psychiatric morbidity may be a contraindication to MCS. Patients with psychosocial, behavioral, cognitive, or other mental disorders who undergo MCS implantation may require referral for psychiatric medication management, counseling, or cognitive behavioral therapy.²¹

Whether patients with MCS have psychosocial or behavioral comorbidities, they experience psychosocial challenges related to MCS self-care and returning home.⁷ Modifications to activities of daily living are required. Patients and caregivers can experience significant stress.^22,23 Early after implantation, patients are often grateful for the device, but they may experience anxiety related to learning and implementing self-care and adapting to lifestyle changes after discharge.⁵ Over time, patients and caregivers gain confidence in their ability to perform MCS self-care and to incorporate lifestyle modifications into daily living.⁵ However, frustration and depression may occur, related to discomfort with carrying equipment, body image issues, loss of independence, and symptoms (eg, ongoing right-sided heart failure or new MCS-related symptoms). Caregivers may also feel burdened by the time and effort needed to assist patients with MCS with device-related care on a daily basis. A multidisciplinary plan involving medical and psychosocial care, including psychopharmacology and counseling, may contribute to positive outcomes for both patients and caregivers.

Cardiac-related cognitive dysfunction often resolves after MCS, which may significantly improve the quality of life for the patient and family. In elderly destination therapy patients, dementia can become an issue, and follow-up cognitive assessment and treatment may be needed.²⁴ If post-MCS cognitive dysfunction increases, patients may be at risk for dementia-related adverse events and poor outcomes, and caregivers may incur significant personal and financial burden (eg, placement of the elderly patient with MCS in a memory care unit).²⁵

RV Failure

During the investigation of decompensated MCS, RV failure must be in the differential because it remains the Achilles heel of LV mechanical support. The relationships of LV and RV geometry and LV-to-RV transit are important concepts in the MCS physiological system. RV failure may follow a variety of physiological conditions.

First, elevated preload from volume overload or blood resuscitation, for example, increases wall stress and can lead to RV dilation and functional tricuspid regurgitation. Second, high device speeds can lead to high CO, which may cause increased venous return to the failing RV. Third, an underfilled LV may allow shifting or suction of the interventricular septum. In this case, the loss of septal contribution to RV contractility can lead to RV failure. Finally, increased RV afterload attributable to pulmonary hypertension and elevated transpulmonary gradient is a common cause of RV failure.^25a

Progressive RV failure is associated with tricuspid regurgitation, hepatic congestion, and peripheral edema. Transthoracic echocardiography may demonstrate RV dilation, hypocontractility, and septal shifting toward the LV. Inotropes to support RV function, pulmonary vasodilators to decrease transpulmonary gradient, or diuresis can be used in the short term to help the impaired and failing RV. If increased LV filling pressures are suspected (findings of hypertension or pulmonary edema), afterload reduction may improve RV function by augmenting forward flow. Phosphodiesterase type 5 inhibitors can be used in this setting to reduce pulmonary hypertension and to support the RV.²⁶ In general, consultation with an MCS center is crucial in the assessment and treatment of RV failure in the patient with MCS.

Aortic Insufficiency

Aortic insufficiency is known to complicate ≈25% of patients with nonpulsatile MCS.^27,28 The understanding of aortic insufficiency after MCS is evolving; however, continuous closure of the aortic valve is thought to be a central factor. Careful attention to outflow cannula orientation to prevent direct flow toward the aortic valve can minimize stress on the valve. For patients requiring long duration of support, aortic insufficiency may become a serious morbidity. Management of hypertension and intravascular volume optimization is important. If aortic insufficiency persists when these factors are controlled, further evaluation by the MCS center is necessary.

Bleeding

With continuous-flow devices, bleeding complications appear to be associated with additional factors beyond the level of anticoagulation.^29–31 Factors contributing to bleeding include platelet dysfunction,³² acquired von Willebrand syndrome,³³ and gastrointestinal bleeding related to arteriovenous malformations.³⁰ Events most commonly seen are gastrointestinal bleeds and epistaxis.

Anemia

Anemia, regardless of the cause, is associated with significant morbidity and mortality in patients with MCS.³⁴ Transfusion of red blood cells can be detrimental for the bridge-to-transplantation patient, increasing anti-HLA antibodies and complicating eventual donor matching. Transfusion should be targeted to symptomatic patients only. Iron replacement can be done safely when indicated. Caution is suggested with the use of erythropoietin-stimulating agents because of their potential to promote thrombosis.

Hemolysis

A baseline level of hemolysis occurs in patients with MCS and may be monitored by periodic laboratory studies (eg, urinalysis, plasma free hemoglobin, haptoglobin, and lactate dehydrogenase analysis).³⁵ Baseline and serial measurements are helpful after changes in clinical status when obstruction or thrombosis is considered. Elevation of lactate dehydrogenase above the patient’s baseline or 2.5 times the upper level of normal requires evaluation at an MCS center.³⁶

Pump Thrombosis

Thrombosis is a relatively frequent adverse event,³⁷ with a reported incidence of 5.5% to 12.2% in patients with MCS.^38–40 Thrombosis is associated with significant morbidity because device exchange is typically necessary. INTERMACS data indicate that 2-year survival after pump exchange or no history of thrombus is 56% and 69%, respectively.³⁹ Factors that may contribute to thrombus formation are subtherapeutic anticoagulation, low pump speed, and elevated blood pressure.⁴⁰ Elevation of lactate dehydrogenase can occur up to 3 months before clinically significant pump thrombosis. It is helpful to obtain a lactate dehydrogenase level during the evaluation of patient with MCS.³⁸ When thrombus is suspected, management should always be coordinated with the MCS center.

Neurological Events

Stroke is a relatively frequent adverse event of MCS. Among all devices, an incidence of 11% is observed at 1 year and of 17% at 2 years.³ Risk factors for stroke in patients on left VAD support remain poorly defined. Because hypertension is a known major risk factor for ischemic and hemorrhagic stroke, postimplantation hypertension should be avoided (Table 4).

Arrhythmia and Heart Rhythm Management

Infection

Infection remains one of the most common causes of morbidity and mortality during VAD support. Currently, the incidence of device infection is roughly 30% at 3 years.³ The percutaneous lead exit site through the skin poses risk for infection; trauma is the leading cause because a break in the healing seal formed at the driveline exit site provides a portal for infection. Patients and their families are trained in the immobilization of the percutaneous lead, meticulous exit-site care, and the prevention of pulling or dropping the external device components to minimize device infections.^8,50 Abdominal binders, additional gauze and tape, stoma-adhesive transparent dressings,⁸ and other securing devices are essential to reduce traction and infection of the driveline exit site. Exit-site dressing protocol and frequency vary from center to center.

Initial Assessment

Despite fixed revolutions per minute, the nature of the blood flow may be pulsatile or nonpulsatile, depending on the contractile reserve of the heart. Individual patients have a variable contribution to CO from the native heart and the device. This may change as a natural response to dynamic physiological conditions such as heart rate, circulatory volume, or vasodilation. If the device provides the majority of the CO, the aortic valve may open intermittently or not at all. No aortic valve opening is seen with severe LV dysfunction or high pump speed. In this circumstance, the arterial pulse pressure will be low, and the patient may not have a palpable pulse. Alternatively, with substantial native heart function or lower pump speeds, LV ejection will occur through the aortic valve. In this scenario, regular aortic valve opening and higher arterial pulse pressures are seen.

A unique approach is necessary when a clinical assessment is performed. Because patients may not have a palpable pulse, standard assessment of vital signs such as blood pressure, heart rate, and pulse oximetry may be unreliable. Initially, an attempt should be made to measure the blood pressure with an automated sphygmomanometer. This will be possible ≈50% of the time⁵¹ because Korotkoff sounds may not be detectable because of low pulse pressure. Manual assessment with a Doppler ultrasound sphygmomanometer may be necessary to determine the pressure at which brachial artery blood flow resumes. Using Doppler requires special expertise and produces a single measurement that may represent the systolic blood pressure or mean arterial pressure (in situations when the pulse pressure is low). Current guidelines recommend maintenance of a mean systemic BP of <80 mm Hg (Class IIb, Level of Evidence C).⁵² For more acutely ill patients, telemetry and invasive hemodynamic monitoring with an arterial line or pulmonary artery catheter may be necessary.¹¹ Patients with MCS who have any acute illness will respond physiologically to maintain adequate perfusion, similar to patients not on MCS. A knowledgeable clinician in consultation with the implanting center can safely stabilize patients.

Confirm Power

Power is delivered through 2 power sources (batteries or alternating-current power source) at all times via the controller to a percutaneous lead that exits the abdominal wall. Damage to this percutaneous lead can compromise the power supply, and this situation can be rectified only by a percutaneous lead repair or pump exchange, which requires transfer to a MCS center. When only one of the power cables is disconnected from the controller, the pump will function properly, but an alarm will sound to request a second power source. If both power supplies are disconnected at the same time, the pump will stop until at least one power source is restored. If there is concern for power failure, all connections should be checked and the power confirmed. If battery power is low, either the batteries should be replaced or the configuration should be changed to alternating-current power. When the power source is confirmed but there is no pump function (by auscultation or persistent red heart alarm), the controller should be exchanged for the backup controller. Should a controller exchange be required, the caregiver or the patient if conscious may be able to perform this exchange because they have received training. A website has field guides that provide useful information for troubleshooting problems with currently available devices.⁴

Pump Stoppage

Cessation of pump function is rare with continuous-flow MCS devices because of improved mechanical reliability and long-term durability compared with earlier-generation pulsatile MCS.^1,2,53 Power failure is the most common cause of pump stoppage. Pump stoppage can result in stagnant blood flow and possible thrombus formation. Inadequate circulation may lead to altered mental status, cyanosis, and signs of heart failure. Restarting the pump after prolonged stoppage can result in stroke or other systemic thromboembolic complications. In the setting of pump failure, it is imperative that care be managed in collaboration with the MCS center. Patients who are comfortable, awake, oriented, and without evidence of heart failure are unlikely to have a severe device malfunction or pump stoppage. To confirm that the device is running, a stethoscope can be placed over the pump in the left upper abdomen, and a constant mechanical hum will be audible. Because under normal operation the patient may not have a peripheral pulse, sufficient arterial flow may need to be confirmed by clinical examination or Doppler. If the device alarm is not sounding, the problem is not likely to be device malfunction. Cardiogenic shock may be a consequence of pump stoppage and should be evaluated for and treated the same as shock in a patients not on MCS.

Transport

Patients with evidence of controller or pump malfunction require immediate evaluation at the nearest center with MCS experience; however, the unstable patient with MCS should be transported to the nearest hospital for stabilization. During transport, care must be taken to avoid excessive tension on the percutaneous lead, which can result in device malfunction or exit-site trauma. Furthermore, care should be used to avoid kinking or cutting the percutaneous lead if clothing needs to be removed. Peripheral equipment (backup batteries, backup controller, universal battery charger, and alternating-current power charger) should be transported with the patient.

Alarm Assessment

There are 2 levels of alarms: advisory and critical (Table 6). Critical alarms are constant, are associated with red warning lights, and can be silenced for only short periods. All critical alarms require immediate assessment and action because they indicate an impending loss of hemodynamic support.^54,55 The first response to a critical alarm is to identify adequate power supply and intact cable connections. If the alarm persists, exchange of the controller to the backup controller should be considered according to MCS center recommendations.

Advisory alarms are intermittent audible alarms that are associated with yellow warning lights.^54,55 They can be silenced for prolonged periods and indicate a minor problem with the patient or the device. Although they require immediate attention, advisory alarms can be addressed in a nonemergent fashion because events that trigger advisory alarms have little effect on hemodynamics and are unlikely to be associated with clinical deterioration. The asymptomatic patient who does not have a change in pump parameters can have device function evaluated at the next routine appointment if cleared by the MCS implanting center. Frequently, advisory alarms can be assessed by telephone without the need for transport to the implanting center or local hospital emergency department. The most common advisory alarm occurs with either a disconnected power cable or low battery life. An advisory alarm accompanied by clinical symptoms or changes in pump parameters should be treated as a critical alarm.

Approach to Advanced Cardiac Life Support

Because of the mechanical circulatory circuit, patients with MCS may remain hemodynamically stable even during malignant ventricular arrhythmias. Standard chest compressions as part of resuscitation efforts must be reserved as a last resort because they can lead to MCS cannula dislodgement or cardiac injury.

If the pump is running normally, the unconscious patient may have adequate circulation despite arrhythmia or pulselessness. Confirmation of circulation should be assessed by Doppler assessment of mean arterial pressure immediately. Standard cardiac life support procedures should be initiated with adaptations based on the presence of artificial circulation.^54,55 When indicated per advanced cardiac life support protocols, pacing, defibrillation, and pharmacological interventions, including fluid resuscitation, should be performed before external chest compressions. Positioning of defibrillation pads directly over the implanted pump should be avoided.⁹ Patients with continuous-flow MCS should not be disconnected from their power source before defibrillation. If perfusion is absent or inadequate, external chest compressions may be warranted.

Palliative Care and Hospice

Whether patients with advanced heart failure choose medical management or MCS implantation, referral to palliative care is an important “actionable” step at the time of informed consent. Referral to palliative care should be viewed as an adjunctive service, not as an alternative service, especially for patients considering destination therapy. Not to be confused with hospice or withdrawal of care, the focus of palliative care is to improve quality of life through the prevention and relief of suffering.⁵⁶ Involvement of palliative care services in the multidisciplinary team leads to increased patient satisfaction with the quality of care.⁵⁷ During the patient selection process, the palliative care team can mobilize important services such as symptom management and psychological or spiritual support.

Because of the unique circumstances that occur at the end of life in patients with MCS, specific advance directives should be completed before device implantation, with emphasis on what the patient would desire in the case of serious complication.^58–60 Over the course of treatment after MCS, the palliative care team is valuable to support patients and caregivers, especially if a catastrophic complication occurs after implantation (eg, debilitating stroke or overwhelming infection).^61,62 After a serious adverse event or in the setting of profoundly impaired quality of life, the palliative care team can recommend hospice.

Withdrawal of Long-Term MCS

MCS is life-sustaining therapy, and elective withdrawal of support may be appropriate when quality of life is no longer improved and continued support would in effect prolong suffering.^62,63 In this scenario, withdrawal of life support, allowing patients to simply succumb to their underlying condition, is morally, legally, and ethically acceptable on the basis of a determination of benefits and burdens of the treatment.^58,62,64 Patients with MCS may request that the device be turned off, and physicians are obliged to respect a competent patient’s (or surrogate decision maker’s) request. A comprehensive end-of-life plan of care focused on the conditions that a patient would expect might lead to withdrawal of life-sustaining therapy should be defined before implantation⁶⁵ and should be revisited over the course of patient care.^60,62 The device can be deactivated in the hospital or at home, according to patient preference. Patient comfort is a high priority. Administration of anesthetics, analgesics, and anxiolytics at appropriate doses can relieve symptoms and reduce suffering. A successful approach is to include team members who are capable of deactivating the device and alarms and providing comfort care to the patient and psychological support to the family and care team.^62,66

Patient Evaluation

1. The primary MCS team should be contacted for any patient-related emergencies.

2. In non–life-threatening situations, care providers inexperienced with the management of MCS should defer device management to patients and their family caregivers until contact can be established with the MCS center or device company technical support.

3. Whenever possible, emergency medical service providers who will be transporting a patients on MCS should also transport the patient’s backup and peripheral equipment.

4. A Doppler probe and a manual cuff can be used to obtain blood pressure in a patient supported by continuous-flow MCS because the automated measurement of heart rate, pulse oximetry, and blood pressure may be unreliable in this setting.

5. Once pump function is established, assessment of the unstable patient on MCS should begin with a general evaluation of the patient for the inciting condition (eg, arrhythmia, hypovolemic or distributive shock, and acute blood loss).

6. Outpatients who present with MCS device stoppage should not have the device restarted without the guidance of the primary MCS center.

Pump Evaluation

1. Device parameters such as power, speed, flow, and pulsatility should be recorded throughout the patient’s course.

2. If battery power is low, either the batteries should be replaced or the configuration should be changed to wall power.

3. When power source is confirmed but there is a persistent device alarm, the controller should be exchanged for the backup controller.

4. If thrombus is suspected, assessment for hemolysis, including lactate dehydrogenase, is recommended.

Chronic Medical Management

1. The percutaneous lead should be secured to reduce traction and infection because driveline trauma is the primary cause of driveline infections.

2. A strict aseptic protocol should be followed when dressing is changed.

3. Patients should receive physical and occupational therapy while hospitalized and referral for cardiac rehabilitation at hospital discharge.

4. Treatment with evidence-based heart failure medical therapies could be beneficial in patients on MCS.

5. Evidence-based management of comorbid conditions (eg, hypertension, hyperlipidemia, and diabetes mellitus) is recommended.

Well-Being and End of Life

1. If psychiatric disability is present after MCS, referral to mental health providers for care, including medication management, counseling, or cognitive behavioral therapy, is recommended.

2. Palliative care involvement is indicated during MCS evaluation and for patients with MCS, especially when receiving destination therapy.

3. When the prognosis is poor for patients with MCS and their suffering and burden outweigh the benefits, deactivation of the MCS device should be discussed with the patient and family caregivers.