Surgical Technique Influences HeartMate II Left Ventricular Assist Device Thrombosis

doi:10.1016/j.athoracsur.2013.05.081

The Annals of Thoracic Surgery

Volume 96, Issue 4, October 2013, Pages 1259-1265

https://doi.org/10.1016/j.athoracsur.2013.05.081 Get rights and content

Background

Thrombosis of the HeartMate II (HM2 [Thoratec Corporation, Pleasanton, CA]) is a potentially devastating complication. While attention has been focused on anticoagulation strategies to prevent this complication, the impact of surgical technique has not been assessed.

Methods

Patients undergoing HM2 implantation at two institutions were reviewed. Pump thrombosis (PT) was defined as a clinical syndrome that included more than 30% elevation in pump power, more than 30% elevation in lactate dehydrogenase, and greater than 20% decrease in hemoglobin with the presence of thrombus in the HM2 stator or rotor, or both, at explant or autopsy. A blinded clinician reviewed dimensions and angles of the HM2 obtained from chest x-ray films. Patients demonstrating PT were compared with patients having normal function.

Results

Of the 49 patients reviewed, 11 (22.4%) displayed evidence of PT at a median of 42 days after HM2 implantation. Patient with PT had greater acute angulation of the HM2 inflow cannula immediately postoperatively (48.2 ± 6.8 versus 65.4 ± 9.2 degrees, p < 0.001) and after 30 days (50.1 ± 8.0 versus 65.1 ± 9.9 degrees, p < 0.001). Pump pocket depth was lower in the PT group immediately after HM2 implantation (107.0 ± 41.9 versus 144.3 ± 20.3 cm, p < 0.001) and after 30 days (86.0 ± 39.1 versus 113.1 ± 25.4 cm, p = 0.02). Patients with evidence of PT did not have a decrease in end-diastolic diameter (76 ± 9 versus 70 ± 15 mm, p = 0.24) whereas patients in the normal function group had effective remodeling of the left ventricle (70 ± 10 versus 56 ± 12 mm, p = 0.01).

Conclusions

Meticulous surgical technique, which necessitates creating an adequately sized pump pocket and appropriately directing the inflow cannula at the time of operation, may reduce the risk of PT.

Section snippets

Patients and Methods

After Institutional Review Board approval, adult patients undergoing HM2 implantation from August 2009 to May 2012 were retrospectively reviewed, spanning the period when the preclotted outflow graft was made commercially available. Laboratory data including lactate dehydrogenase, INR, and hemoglobin were collected prospectively.

We used anteroposterior chest roentgenogram (CXR) to assess for inflow cannula (IC) angulation and pump pocket (PP) depth because its clinically practical, measurements

Baseline Patient Characteristics

Seventy-three patients underwent HM2 implantation during the study period. Twenty-four were excluded from the analysis because either all four criteria for PT were not present, patients did not fulfill requirements for the use of CXRs, or validation of the radiographic set-up error and rotation by CT scans could not be performed. The remaining 49 patients made up the cohort in this analysis. Of the 24 excluded patients, 2 displayed evidence of PT.

These 49 patients underwent HM2 implantation by

Comment

Continuous flow LVADs are smaller, more durable, offer better survival, and have a favorable adverse event profile [13] when compared with pulsatile devices. However, PT continues to be a significant problem [14]. Pump thrombosis is likely influenced by many factors such as infection (local or remote), the need for noncardiac surgery, or when anticoagulation therapy needs to be held in the event of gastrointestinal bleeding, neurologic hemorrhage, or epistaxis [15]. Although anticoagulation

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The frequent occurrence of thromboembolic cerebral events continues to limit the widespread implementation of Ventricular Assist Devices (VAD) despite continued advancements in VAD design and anti-coagulation treatments. Recent studies point to the optimal positioning of the outflow graft (OG) as a potential mitigator of post implantation thromboembolism.
This study aims to examine the tailoring of the OG implantation orientation with the goal of minimizing the number of thrombi reaching the cerebral vessels by means of a formal shape optimization scheme incorporated into a multi-scale hemodynamics analysis.
A 3-D patient-specific computational fluid dynamics model is loosely coupled in a two-way manner to a 0-D lumped parameter model of the peripheral circulation. A Lagrangian particle-tracking scheme models and tracks thrombi as non-interacting solid spheres. The loose coupling between CFD and LPM is integrated into a geometric shape optimization scheme which aims to optimize an objective function that targets a drop in cerebral embolization, and an overall reduction in particle residence times.
The results elucidate the importance of OG anastomosis orientation and placement particularly in the case that studied particle release from the OG, as a fivefold decrease in cerebral embolization was observed between the optimal and non-optimal implantations. Another case considered particle release from the ventricle and aortic root walls, in which optimal implantation was achieved with a shallow insertion angle. Particle release from all three origins was investigated in the third case, demonstrating that the optimal configurations were generally characterized by VAD flow directed along the central lumen of the aortic arch. Because optimal configurations depended on the anatomic origin of the thrombus, it is important to determine, in clinical studies, the most likely sites of thrombus formation in VAD patients.
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This study reports a single-center experience with thrombolytics for left ventricular assist device (LVAD) pump thrombosis.
Adults undergoing continuous-flow LVAD implantation between 2004 and 2018 at a single center were reviewed and those with pump thrombosis were identified. Primary outcomes included 1-year survival and success rates of thrombolytic therapy. Secondary outcomes included posttreatment adverse events, freedom from major bleeding at 1 year, and freedom from stroke at 1-year follow-up.
A total of 341 patients underwent LVAD implantation and 10.8% (n = 37) developed pump thrombosis. Of those 37, 26 received initial thrombolytic therapy (70.2%), 5 underwent direct pump exchange (13.5%), and 6 received only intravenous heparin owing to presentation with acute stroke or severe multiorgan failure (16.2%). Successful treatment was achieved in 11.5% of patients receiving thrombolytics (n = 3). Early adverse events after thrombolytic therapy included major bleeding in 11.5% (n = 3) and new stroke in 7.7% (n = 2). Most patients undergoing thrombolytic therapy underwent subsequent device exchange (69.2%; n = 18). Overall survival in patients with pump thrombosis after treatment was 96.8% at 30 days, 78.9% at 90 days, and 63.1% at 1 year. Freedom from major bleeding and stroke at 1 year was 74.2% and 87.2%, respectively.
In this single-center experience of thrombolytics for pump thrombosis in LVAD patients, there was limited efficacy; most patients required subsequent pump exchange. Combined with the risk for major bleeding or stroke with thrombolysis, this underscores the importance of further refining patient selection for direct pump exchange in those presenting with pump thrombosis.
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HeartWare ventricular assist device (HVAD) cannula position is associated with hemodynamics and heart failure readmissions. However, its impact on hemocompatibility-related adverse events (HRAEs) remains uncertain.
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Novel Formula to Calculate Three-Dimensional Angle Between Inflow Cannula and Device Body of HeartMate II LVAD
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Citation Excerpt :
As a result, the 3D angles at our institution were wide with deep pump pockets, in general. In fact, our mean calculated 3D angle (from formula) was 74.4° ± 14.2° and mean 2D projected angle (from CXR) was 65.2° ± 11.3°, which is much wider compared with those of other investigators who reported the relationship between acute device angle and device thrombosis—for example, Taghavi and coworkers5 with 2D angle (60.5° at final follow-up). Another possible reason of no statistical differences in the angle between those with and without adverse events may have resulted from under-powered statistics due to the small sample size.
The acute angle between inflow cannula and device body of HeartMate II left ventricular assist device (LVAD) (Abbott, Pleasanton, California) is associated with device thrombosis. However, most studies utilized two-dimensional (2D) angle obtained from chest roentgenogram (CXR), which is unlikely accurate. We aimed to create and validate a formula to estimate actual three-dimensional (3D) angle.
We retrospectively reviewed the cohort undergoing HeartMate II LVAD implantation between 2008 and 2016. A formula for calculating 3D angles of the LVAD inflow cannula relative to the device body was mathematically derived, using simple 2D measurements from CXR.
The cohort included consecutive 275 patients with HeartMate II (median age: 60 [25% quartile: 51, 75% quartile: 68] years). There was no significant difference between the calculated 3D angles (from formula) and actual 3D angles (from computed tomography) from the subset group with 3D computed tomography (n = 28) (71.7° ± 13.4° vs 71.1° ± 11.5°, P = .858). Among all participants, the calculated 3D angle (from formula) was 74.4° ± 14.2°, which was significantly larger than the 2D projected angle (from CXR) (65.2° ± 11.3°, P < .001). There was no statistical difference in the calculated 3D angles (from formula) between patients with/without device thrombosis, hemorrhagic stroke, ischemic stroke, or mortality (P > .05 for all).
We established a novel formula to mathematically calculate actual 3D angles between inflow cannula and device body of HeartMate II. The formula would help investigators to validate their findings of the relationship between 2D projected angle (from CXR) and device thrombosis.
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Original articleAdult cardiacSurgical Technique Influences HeartMate II Left Ventricular Assist Device Thrombosis

Background

Methods

Results

Conclusions

Section snippets

Patients and Methods

Baseline Patient Characteristics

Comment

J Am Coll Cardiol

J Thorac Cardiovasc Surg

J Heart Lung Transplant

J Am Coll Cardiol

J Heart Lung Transplant

J Heart Lung Transplant

J Thorac Cardiovasc Surg

Int J Radiat Oncol Biol Phys

Ann Thorac Surg

Semin Thorac Cardiovasc Surg

Original article
Adult cardiac
Surgical Technique Influences HeartMate II Left Ventricular Assist Device Thrombosis