Low Flow Alarms Research Articles

Serial Assessment of Magnetically Levitated Centrifugal-Flow LVAD Pump Position and Inflow Angle on Chest Radiograph and Effects on Adverse Events

We analyzed the position of a fully magnetically levitated centrifugal-flow left ventricular assist device (LVAD) on serial radiographs to assess positional change and possible correlation with adverse events. We retrospectively analyzed 59 LVAD recipients who had serial chest radiographs at 1 month, 6 months, and 12 months after implantation between November 2014 and June 2018. We measured pump angle, pump-spine distance, and pump-diaphragm depth (figure) and investigated their relationship to a composite outcome of heart failure readmission, low flow alarms, or inflow/outflow occlusion requiring surgical repositioning through recurrent event survival modeling. There were 26 patients who experienced the composite outcome; in these patients, the median 1 month pump angle was 66.2 degrees (IQR 54.5-78.0) as compared to 59.0 degrees (IQR 47.0-65.0) in the 33 patients who did not have adverse events (p = 0.04). Pump depth and pump-spine distance at 1 month were not associated with the composite outcome. Between 1 month and 6 months, the absolute pump-spine distance changed by 10.00 mm (p<0.01) and the absolute pump-diaphragm depth changed by 18.80 mm (p<0.01). These parameters did not change significantly between 6-12 months post-implantation. Pump angle did not change significantly over any time period. Change in pump depth between 1-6 months (HR = 1.019; 95%CI = 1.000-1.039; p = 0.05) and between 6-12 months (HR = 1.020; 95%CI = 1.000-1.040; p = 0.05) were weakly associated with the composite outcome. Larger pump angles are associated with the composite outcome of heart failure readmission, low flow alarm, or inflow/outflow obstruction. At 6 months, the absolute values of pump-spine distance change and pump-diaphragm depth change are significant. Movement in pump depth is weakly associated with the composite outcome.

Diagnosis and Treatment Strategies of Outflow Graft Obstruction in the Fully Magnetically Levitated Continuous-Flow Centrifugal Left Ventricular Assist Device - A Multicenter Case Series

Reports of pump thrombosis are less common for the HeartMate 3 than for other commercially available LVAD. However, blood flow obstructions of the inflow and especially of the outflow graft are likely to occur also with this device. A correct diagnosis is crucial for optimal treatment to ultimately avoid bail-out by (urgent) heart transplantation or unwarranted pump exchange. We present six cases of outflow graft obstruction (OGO) other than twist of the outflow graft under oral anticoagulation. We present detection principles and discuss treatment strategies. 1: 64 y/o, female, valvular heart disease, 21 months after implantation, presentation with multiple low-flow alarms. 50% OGO in CT scan. External cannula compression proximal of the LVAD outflow conduit in percutaneous angiography (PA). Re-thoracotomy, opening of the bend relief made of a reinforced PTFE graft, removement of hyaline thrombus, pump flow returned to normal. 2: 70 y/o, female, dilated CMP, recurrent low-flow alarms, high PI values. Consistently low flow in ramp study. Treatment of severe OGO in PA with two stents. Pump flow returned to normal. 3: 55 y/o, male. Presentation of acute angina pectoris, dyspnea. 75% OGO in CT scan. PA and implantation of two stents. Relief from clinical symptoms. 4: 37 y/o male, dilated CMP. Routinely admission for evaluation for heart transplantation (HTx). LVAD log files normal. Significant OGO in CT scan. PA confirmed OGO, but no relevant gradient pressure across the outflow graft, decision to "watchful waiting approach" and listing for HTx. 5: 67 y/o, male, dilated CMP. Presentation in a reduced general condition and slightly reduced pump flow. 70% OGO in CT scan. Pump flow increased to normal after intervention. 6: 56 y/o, female, ischemic CMP. Presentation with acute persistent low-flow alarms. 50% OGO in CT scan. Multiple hypodense areas in the infra- and supratentorial region as consequence of an embolic induced ischemic stroke. Despite emergency treatment the patient died on the same day. OGO in LVAD is a rare complication whose clinical presentation may be subtle. Three patients were successfully managed with stents, one underwent surgical revision, one patient died despite emergency treatment and the last patient without symptoms was listed for HTx.

Inflow or Outflow Obstruction Requiring Surgical Corrections Late after HeartMate 3 Left Ventricular Assist Device Insertion

Inflow or outflow obstruction is a rare, but critical complication after HeartMate 3 (HM3) LVAD implantation. We report our single center experience of outflow or inflow obstruction requiring surgical intervention after HM3 implant. We retrospectively reviewed 166 patients who underwent primary HM3 implantation at Columbia University Irving Medical Center between November, 2014 and July, 2019. Seven cases (4.2%) of inflow or outflow obstruction were identified (Table 1). Median age was 59 years (IQR 44-71), and all but one were men. There were 3 cases of inflow occlusion, 2 outflow graft twists, 1 outflow graft compression by thrombus, and 1 bend relief disconnect. The duration from device implantation to reintervention was 162-804 days. All patients underwent HM 3 implantation via median sternotomy and the pump was placed either in the intrapericardial (n=6) or intrathoracic (n=1) space. Of note, both patients who developed outflow graft twist, had the initial implant prior to introduction of the outflow graft clip. Presence of low flow alarm was the most common presenting sign. CT angiogram identified a problem in 6 out of 7 cases. Surgical approach used for correction is presented in Table 1. Clinical symptoms and/or alarms resolved after surgery in all cases and all patients remain alive on support with median follow-up of 528 days (IQR 49-834). HM3 inflow or outflow obstruction is a rare but significant complication of device therapy. CT angiogram is a useful diagnostic modality that should be considered in all patients with persistent low flow alarms. Prompt diagnosis and surgical correction results in good outcomes.

LEFT VENTRICULAR ASSIST DEVICE OUTFLOW TRACK TWIST MASQUERADING AS RV FAILURE

Precise diagnosis and troubleshooting of LVAD complications require thorough and careful evaluation of imaging, lab testing and LVAD parameters. A 60 yo man with NICM and HM3 implant presented with dizziness and low flow alarms. ECG showed VT at 160 bpm. Labs showed AKI, normal plasma free

ARRHYTHMIA CAUSING LOW FLOW ALARM IN LEFT VENTRICULAR ASSIST DEVICE PATIENT: WHAT IS THE BEST OPTION?

ARRHYTHMIA CAUSING LOW FLOW ALARM IN LEFT VENTRICULAR ASSIST DEVICE PATIENT: WHAT IS THE BEST OPTION?

AN UNEXPECTED CAUSE FOR ALARM

A 73 year-old male who underwent HeartMate II LVAD implantation 5 years ago for ischemic cardiomyopathy called clinic due to multiple low-flow alarms. The alarms started one week prior to admission, did not resolve with controller change, and became so frequent that his neighbor called the police.

A "Blinking" Left Ventricular Assist Device

A 61-year-old male with history of coronary artery disease and end stage ischemic cardiomyopathy underwent a successful implantation of a HeartMate 3 device with an uneventful recovery. However, after 6 months, he complained of increased fatigue, intermittent dizziness, and weakness after minor exertion. The pulsatility index was increased to 8, but the left ventricular assist device (LVAD) was otherwise functioning properly. No major changes in either medications or laboratory results were noted. The patient started getting low flow alarms seven months after the procedure and the dizziness increased. On the controller, a continuously changing (“blinking”) speed was noted (Supplemental Video 1). There was a palpable peripheral pulse and a measurable systolic and diastolic systemic pressure of 105/70 mmHg. There were no signs of hemolysis. The patient was admitted for observation, and a transesophageal echocardiogram was obtained (Supplemental Video 2). The main findings included: 1. Partially recovered left ventricle with ejection fraction 40-45% 2. Small left ventricular cavity with the inflow cannula touching the septum on every other beat 3. Hypokinetic and moderately enlarged right ventricle. After decreasing the speed of the LVAD to from 5200 revolutions per minute to 4800 and giving oral and intravenous fluids, the situation improved. Unfortunately, the symptoms did not completely resolve, and the patient remains admitted to await a cardiac transplantation. This case demonstrates an unusual pattern of a “blinking” LVAD speed due to left ventricular recovery with a small cavity and frequent suctions.

Proximal outflow graft extrinsic compression of the Heartmate 3 centrifugal flow left ventricular assist device resulting in pump dysfunction

We herein report an unusual life-threatening complication with the Hearmate 3 centrifugal ventricular assist device: proximal outflow graft extrinsic compression due to external thrombus leading to pump dysfunction and urgent heart transplantation. Low flow alarms without other abnormalities lead to the diagnosis of outflow occlusion. There was no evidence for a twist of the outflow graft, and no evidence for outflow thrombosis. The location of the outflow occlusion was particularly difficult to diagnose due to metallic artifacts around the pump. This report underscores that this complication should be screened in case of persistent low-flow alarms with the Heartmate 3 centrifugal pump.

TAVR Thrombosis in Patient Supported with Durable Left Ventricular Assist Device

Introduction Aortic incompetence (AI) is very common complication after continuous flow left ventricular assist device (LVAD) implantation, and can result in increased symptoms for LVAD patients. Recent advances in Transcatheter Aortic Valve Replacement (TAVR) technology has resulted in this becoming a potential therapeutic avenue for LVAD patients with AI. We report a case of TAVR implantation in a patient supported with a LVAD complicated by thrombosis. Case Report A 61-year-old female presented with STEMI. She was treated with primary PCI, but had progressive cardiogenic shock and was placed on VA-ECMO. Due to high PRA, she was unable to be listed for primary transplantation and underwent implantation of a Heartware LVAD (Medtronic) as bridge to decision. Her post-operative course was complicated by recurrent GI bleeding. Over the following 12 months, she was noted to have worsening AI on routine echocardiography, with worsening symptoms that persisted despite hemodynamic and echocardiographic-guided LVAD optimization. After heart team review, her anatomy was deemed appropriate for TAVR and she underwent implant of a 26mm Evolut Pro (Medtronic). The procedure was complicated by post-implant complete heart block on POD #4 requiring pacemaker implantation. She was discharged from the hospital, however over the next 3 months had recurrent episodes of low flow alarms that continued despite LVAD speed and medication optimization. A transthoracic echocardiogram did not reveal any abnormalities, although it was unable to visualize the TAVR leaflets. A multiphase 4D CT Angiogram was performed to rule out LVAD outflow graft obstruction, which revealed extensive hypoattenuating leaflet thickening involving all 3 leaflets of the TAVR with absent leaflet motion consistent with thrombosis of the prosthetic valve leaflets (See Figure). She was started on intravenous anticoagulation (unfractionated heparin), but this had to be ceased due to hemodynamically significant GI bleeding requiring multiple transfusions. LVAD speed was also attempted to be increased to minimize risk of aortic valve opening, but this was unable to be continued due to recurrent low flow LVAD alarms. Repeat imaging 3 months later showed continual thrombosis, and she has remained stable while awaiting transplantation. Summary We describe a novel complication of TAVR in LVAD patients. This case highlights the major diagnostic and management dilemmas that should be considered as this management strategy becomes more widespread in this patient population.

Initial experience with telemonitoring in left ventricular assist device patients.

Left ventricular assist devices (LVAD) are increasingly used in patients with end stage heart failure. The HeartAssist 5 and aVAD LVADs offer telemetric monitoring capabilities. Here we report our initial single centre experience with the largest telemonitoring cohort of LVAD patients. Eleven patients (9 males) received a telemonitoring-capable LVAD and were included in our telemonitoring cohort. Waveforms and alarm data were obtained from the telemonitoring system and hospital records were reviewed for clinical data. Mean age at LVAD implantation was 59±5.1 years (mean ± standard deviation). Seven patients had non-ischemic cardiomyopathy and 4 patients had ischemic cardiomyopathy. Median LVEF at implant was 16% (IQR, 15-20%). The total follow-up time was 2,438 patient-days. A total of 6,216 alarm messages were generated in 11 patients. Most common were low flow alarms due to hypovolemia, followed by low flow alarms because of suspected pump thrombosis. One patient died during follow-up, one received a cardiac transplant and one had the LVAD explanted because of pump thrombosis. Pump thrombosis was suspected in 5 patients with 8 episodes of sudden flow decreases and laboratory signs of haemolysis. Real-time telemonitoring of LVAD pump flow, motor speed and power consumption is a promising tool in the follow-up of LVAD recipients. Trending pump flow over hours or days can assist in the early detection of complications, especially flow reductions due to hypovolemia and LVAD thrombosis. Further studies are warranted to delineate the impact of remote monitoring on patients' prognosis.

Gore-Tex Mesh as Cause for Distal Outflow Graft Obstruction in Ventricular Assist Device Patients

Purpose Re-do sternotomy following left ventricular assist device (LVAD) implant can occur due to cardiac transplantation or device complication. A polytetrafluoroethylene membrane (Gore-Tex) has been used to cover portions of the outflow graft to reduce adhesions. We describe 3 cases of late-presenting extrinsic compression of the distal outflow graft from a Gore-Tex membrane in both HVAD and HMII devices. Methods We conducted a retrospective analysis of all LVAD implants which included a Gore-Tex membrane at our institution between 1/2012-6/2018. We defined cases of extrinsic outflow graft obstruction (OGO) by clinical presentation, CT imaging, and intraoperative findings. Results During the study period, 158 LVADs with tubular Gore-Tex outflow graft coverage were implanted (93 HVAD, 59 HM2, 4 HM3). Three cases of extrinsic OGO (1 HVAD, 2 HM2) were identified, for a cumulative incidence of 1.9% (1.44 per 100 patient years). The average time to clinical presentation was 1157 ± 155 days. Each case presented with persistent low-flow alarms detected via remote monitoring in the absence of power spikes or clinical symptoms. Markers of hemolysis (LDH, plasma free hemoglobin) were normal, INR was therapeutic, and echocardiograms did not indicate volume depletion or right ventricular failure. In each case, CT imaging demonstrated critical narrowing of the distal outflow graft (N=2) or aortic anastomosis (N=1) (Fig A). Each patient underwent surgical exploration; upon incision of the overlying Gore-Tex membrane, a proteinaceous material was drained resulting in immediate improvement in flows and avoidance of pump exchange (Fig B). Conclusion We highlight 3 cases of a previously undescribed mechanism of OGO by extrinsic compression, resulting from accumulation of proteinaceous material underneath the Gore-Tex membrane. Each presented with gradual onset of low flows without additional symptoms, suggesting that a high level of clinical suspicion is necessary to ensure appropriate management.

LOW FLOW ALARM IN A PATIENT WITH LEFT VENTRICULAR ASSIST DEVICE: WHAT WENT WRONG?

Pump thrombosis is a relatively common complication of Left Ventricular Assist Device (LVAD), but complete inflow cannula obstruction due to thrombosis is rare. A 56-year-old male presented after a sudden onset of low flow LVAD alarms and dyspnea. His respiratory rate was 28, his mean blood

Intravascular Ultrasound-Guided Percutaneous Stenting for Treatment of LVAD Outflow Graft Obstruction

Introduction Left ventricular assist device (LVAD) outflow graft obstruction is a well-known and significant complication. The typical management involves treatment of presumed thrombosis of the graft with intensified anticoagulation or surgery. More recently, endovascular stenting has been reported as a possible treatment option. We describe the management of a LVAD outflow cannula obstruction with never reported intravascular ultrasound (IVUS)-guided covered endovascular stenting. Case report A 68 year-old female with non-ischemic cardiomyopathy status-post LVAD implantation in March 2016 presented with persistent symptomatic low flow alarms and clinical signs of heart failure. Symptoms seemed to worsen when she laid on her right side. She was compliant with her anticoagulation and lactate dehydrogenase level was found to be near her baseline. A CT scan with IV contrast revealed intraluminal obstruction of the LVAD outflow graft secondary to a kinked portion of the outflow cannula near the bend relief with a possible thrombotic component. The severe angulation of the cannula likely developed due to the patient's gradual weight gain of 28kg in the 24 months since LVAD implantation. Given the patient's risk profile, a percutaneous endovascular stenting approach was taken. IVUS was used to visualize the obstruction and kinking of the graft. A balloon-expandable covered stent was deployed at the stenotic site while the LVAD was briefly stopped to avoid stent/balloon migration. A covered stent was used to minimize the risk of thrombus migration/extrusion. IVUS was used again after post-dilation of the stent to confirm placement with no thrombus extrusion. Several hours later the patient had recurrent low-flow alarms. A repeat CT scan revealed that the kink had migrated and been transmitted within the outflow cannula towards the LVAD. The patient returned to the angiography suite where 2 balloon expandable stents were deployed more proximally within the outflow cannula and in an overlapping fashion with the original covered stent. Non-covered stents were used for the second procedure as there was no suspected thrombotic component. IVUS showed no significant residual kinking post-stenting. This was confirmed with a repeat CT scan. The patient recovered without any hemodynamic or neurologic sequelae. Conclusion Percutaneous endovascular stenting is an emerging option for treatment of outflow tract obstruction in LVAD patients that are not candidates for surgery. IVUS can be a valuable tool during intervention to confirm proper stent position, thrombus isolation, and outflow cannula geometry.

Internal Versus External Compression of a Left Ventricular Assist Device Outflow Graft

Obstruction within the circuit of a left ventricular assist device (LVAD) is a challenging situation for clinicians to definitively diagnose and manage. Available diagnostic tools are limited in their ability to visualize large portions within the device and cannulas, often leading to uncertainty as to whether redo surgery is required or if there are feasible medical or percutaneous alternatives. Here, we report a case of LVAD outflow graft obstruction, which by computed tomographic angiography (CTA) appeared to be intramural thrombus, but by intravascular ultrasound (IVUS) was shown to be compression external to the graft. A 62-year-old female with a continuous flow LVAD (HeartMate II Abbott, IL) 5 years prior presented to the emergency department with frequent low-flow alarms and syncope. The patient’s post-LVAD course had been complicated by outflow graft infection 1 year after initial implantation, necessitating an outflow graft replacement. She had also experienced multiple bleeding events for which her warfarin therapeutic goal was lowered. In the preceding year, her LVAD flows had steadily declined from 4.5 to 5.0 L/min to 2.7 to 2.8 L/min with an increasing frequency of low-flow alarms not responsive to the intravenous fluid administration or changes in LVAD …

Outflow Graft Occlusion of the HeartMate 3 Left Ventricular Assist Device.

Continuous-flow ventricular assist devices have demonstrated clinical superiority compared with the first-generation pulsatile devices; however, complications continue to affect patients on left ventricular assist device (LVAD) support.1 The recently published MOMENTUM 3 trial (Multicenter Study of MagLev Technology in Patients Undergoing Mechanical Circulatory Support Therapy With HeartMate3) reported that the HeartMate 3 (HM3) was associated with better outcomes after 6 months when compared with the HM2. None of the patients randomized to the HM3 device had suspected or confirmed thrombosis.2 In this brief report, we describe 2 patients who developed extrinsic occlusion of the outflow graft after HM3 implantation. A 65-year-old man with ischemic cardiomyopathy underwent implantation of an HM3 LVAD as bridge to transplantation. Because of significant epistaxis, acetylsalicylic acid was reduced from 325 to 81 mg daily, whereas international normalized ratio was maintained between 2 and 3. One-year post-LVAD, the patient presented with congestive symptoms and deteriorating renal function. His LVAD had logged multiple low-flow alarms, as low as 1.9 L/min (previously 4–4.5 L/min; Figure [C]). Serum lactate dehydrogenase was 290 U/L (125–220 U/L) and international normalized ratio maintained within therapeutic range. A noncontrast computed tomographic scan of the chest showed no …

First series of left ventricular assist device exchanges to HeartMate 3.

Left ventricular assist device (LVAD) exchange is becoming a standard surgical procedure. The exchange procedure is an opportunity to upgrade patients to a new generation pump that offers advanced reduction of adverse events or longer battery hours. We performed an analysis of 6 consecutive patients who underwent LVAD exchange to HeartMate 3 either from a HeartWare or HeartMate (HM) II device. Minimally invasive operations were performed through a lateral thoracotomy. Follow-up time was 6 months after LVAD exchange. We present 4 patients with the HM II and 2 patients with the HeartWare ventricular assist device (HVAD) who underwent LVAD exchange to HM III. The average age was 57.5 years. At the time of the LVAD exchange, all patients were classified as Interagency Registry for Mechanically Assisted Circulatory Support level 3. In 5 cases, LVAD infection led to LVAD exchange (83%, 5/6). The remaining patient underwent LVAD exchange due to pump thrombosis (16%, 1/6). The 6-month survival rate after LVAD exchange was 100% (6/6). None of the patients was postoperatively supported by extracorporeal membrane oxygenation. No patient experienced postoperative relevant bleeding. One patient suffered minor cerebral bleeding (16.6%, 1/6). At the 6-month follow-up examination, 1 patient reported a single syncope and several low-flow alarms (1/6). The remaining 5 patients showed no adverse events or technical malfunctions of the VAD (5/6). LVAD exchanges from HM II as well from HVAD to HM 3 are proven to be technically feasible. Due to the advantages and technical improvements of the new-generation pumps, this procedure is an excellent opportunity to give patients access to a superior generation of assist device.

Outflow Graft Obstruction Treated With Transcatheter Management: A Novel Therapy for a New Diagnosis

The duration of support in patients with HeartMate II implantation as a bridge to transplant or as destination therapy is rising. As clinical experience continues to grow, physiologic changes contributing to pump malfunction are becoming apparent. Once malfunction is noted with increased power spikes, rises in lactate dehydrogenase and low-flow alarms, thrombosis of the pump is at risk. We describe outflow graft compression and offer an expeditious and definitive management strategy. Our novel management stenting strategy for outflow graft compression will continue to evolve as experience is gained.

Percutaneous Angioplasty of Stenotic Outflow Graft Anastomosis of HeartMate II

A 55-year-old man with nonischemic dilated cardiomyopathy who had undergone HeartMate II (HM2) (Thoratec, Pleasanton, California) implantation for destination therapy was readmitted 1.5 years later because of low-flow alarms with dizziness. Transesophageal echocardiogram showed decreased velocity

Bridge to recovery in two cases of dilated cardiomyopathy after long-term mechanical circulatory support.

Ventricular assist devices (VADs) have become an established therapeutic option for patients with end-stage heart failure. Achieving the potential for recovery of native heart function using VADs is an established form of treatment in a selected group of patients with HF. We report two cases of VAD patients with different types of pump used for mechanical circulatory support, a continuous flow pump (Heart-Ware®) and a pulsatile pump (POLVAD MEV®), which allow regeneration of the native heart. Patients were qualified as INTERMACS level 3-4 for elective implantation of an LVAD. Implantations were performed without complications. The postoperative course was uncomplicated. In the HeartWare patient the follow-up was complicated by episodes of epistaxis and recurrent GIB as well as driveline infection. The follow-up of the POLVAD MEV patient was uneventful. Recurrent GIB forced us to withdraw aspirin and warfarin therapy and maintain only clopidogrel in the HeartWare patient.. In mid-February 2013 the patient was admitted due to dysfunction of the centrifugal pump with a continuous low-flow alarm and increase power consumption. Under close monitoring of the patient a decision was made to stop the pump immediately and evaluate cardiac function. The serial echocardiography studies showed significant improvement in LVEF up to 45% and no significant valvular pathology. In February 2013 LVAD explant was performed by left thoracotomy without complications. At six-month follow-up the patient was in a good clinical condition, in NYHA class I/II, and on pharmacological treatment.

Left ventricular assist device malposition interrogated by 4-D cine computed tomography

67-year-old female with left ventricular assist device (LVAD) presented with recurrent low-flow alarms. No clear etiology could be determined by history, or evaluation with radiograph and echocardiogram. Computed tomographic (CT) imaging with 3-D and 4-D assessment identified the abnormality as steep angulation of the inflow cannula and partial obstruction by the adjacent anterior wall, likely in part caused by recovered left ventricular function and reverse remodeling. Improved left ventricle size and function was correlated by semi-automated analysis of CT data, which also indicated mild right ventricle dilation and systolic dysfunction. LVAD explantation was performed, and has been well tolerated by the patient. Echocardiography remains the primary imaging modality to assess patients post LVAD placement, but in this instance CT provided valuable information to identify the abnormality and help direct patient management. CT assessment in patients with LVAD additionally provides valuable information prior to redo sternotomy for pump explantation, revision, or transplantation.