The Institutional Review Board of Samsung Medical Center approved this study (SMC 2023-08-121; date of approval: August 25, 2023). The requirement for informed consent from individual patients was waived due to the retrospective nature of the research, which presented minimal risk to participants.

A 70-year-old man underwent left ventricular assist device (LVAD) surgery for alcoholic dilated cardiomyopathy. At that time, his condition was classified as New York Heart Association class IV, and his blood type was O. The procedure was performed as a bridge to candidacy. The patient’s medical history included no comorbid conditions other than hypertension and atrial fibrillation. His Interagency Registry for Mechanically Assisted Circulatory Support profile was 3. Preoperatively, his left ventricular ejection fraction was measured at 18%, and his left ventricular end-diastolic diameter was 78 mm. The mean pulmonary artery pressure was recorded at 23 mm Hg, and the pulmonary capillary wedge pressure was 12 mm Hg. The patient was taking angiotensin receptor blockers, amiodarone, carvedilol, and edoxaban. Additionally, he had previously received a defibrillator implant for cardiac resynchronization therapy.

For the procedure, the HeartWare ventricular assist device (HVAD; Medtronic International Inc., Framingham, MA, USA) was implanted via sternotomy, and the LVAD outflow graft was anastomosed to the ascending aorta. A 19-mm expanded polytetrafluoroethylene (ePTFE) graft was wrapped with several sutures to maintain a tubular shape along the entire length of the outflow graft, in preparation for future redo surgery. Concomitant aortic valve closure was performed using Park’s stitch in response to mild aortic regurgitation. Following the procedure, the LVAD functioned consistently at 2,400 revolutions per minute (rpm), delivering a flow rate between 3.8 and 4 L/min and consuming 3.1 W of power. An echocardiography conducted 10 days after surgery revealed evidence of pericarditis, organized hematoma, inflammation, adhesions, pericardial thickening, and restrictive physiology. After continued high-dose steroid treatment, the patient showed improvement, and he was discharged 17 days after surgery.

Twenty-six months after the procedure, the patient experienced several ventricular tachycardia events. Echocardiography performed after admission revealed no meaningful changes compared to previous results. However, computed tomography (CT) angiography indicated moderate stenosis of the LVAD outflow graft (Fig. 1A, B). The patient remained asymptomatic, and observation was continued. However, 36 months after surgery, the patient presented with dizziness accompanied by low-flow alerts from the LVAD. Upon admission, the LVAD was operating at 2,600 rpm, maintaining a flow rate of 3 L/min while the patient was recumbent. However, this decreased to 2 L/min upon sitting or standing (Fig. 2). The patient’s blood pressure and heart rate were within normal limits. Echocardiography indicated inadequate decompression of the left ventricle, despite an increase in LVAD rpm. During echocardiography, the LVAD flow further decreased to 1 L/min. Subsequent CT angiography confirmed critical stenosis at the distal portion of the graft, along with diffuse external compression and narrowing of the outflow graft (Fig. 1C, D). Given these findings, on the day of admission, the decision was made to perform emergent surgery.

Figure 1. (A, B) Computed tomography (CT) angiography performed approximately 2 years after left ventricular assist device surgery shows evidence of stenosis in the outflow graft (indicated by the yellow arrow). (C, D) Upon readmission of the patient due to low-flow alerts, CT angiography was repeated, confirming critical stenosis of the distal portion of the graft along with diffuse external compression and narrowing of the outflow graft (denoted by the yellow arrow).

Figure 2. Log analysis reveals a decrease in flow to less than 2 L/min when standing or sitting upright prior to outflow graft correction surgery. The star indicates the point at which surgery was performed. VAD, ventricular assist device; lpm, liters per minute; rpm, revolutions per minute.

Since the outflow graft was positioned along the midline of the chest, redo sternotomy was carefully performed. Immediately following sternotomy, the LVAD flow greatly improved. The anterior wall of the ePTFE graft was removed, from its origin to the aortic anastomosis. A substantial volume of thick seroma tissue was discovered between the ePTFE and the outflow graft. This tissue and ePTFE have been completely removed. The maximum thickness of the organized seroma measured approximately 10 mm. No thrombosis or graft kinking was detected, and the attachment site appeared normal (Fig. 3A). Following the additional removal of tissues compressing the outflow graft, the procedure was concluded without applying wrapping to the outflow graft. Postoperatively, the LVAD flow rate was 3.6 L/min, the device was operating at 2,600 rpm, and the patient’s vital signs were stable. Surgical pathology of the debris surrounding the outflow graft identified it as a fibrinous clot (Fig. 3B). The patient was discharged without further complications and remained in good health 6 days after surgery.

Figure 3. (A) Intraoperative images depict biodebris between the outflow graft and protective graft, causing extrinsic compression. The complete removal of the protective graft led to complete relief of the outflow graft. (B) Surgical pathology of debris surrounding the outflow graft revealed a fibrinous clot (hematoxylin and eosin stain, ×400).

External outflow graft obstruction (eOGO) is a rare but life-threatening complication [1,2]. The outflow grafts of LVAD are typically composed of gelatin-impregnated woven polyester. To prevent adhesion during redo surgery and to provide protection from band relief, the distal outflow graft is wrapped in an impermeable ePTFE membrane [3]. Obstruction is known to develop when a gelatinous substance accumulates, forming an organized seroma. This creates a gap between the outflow graft and the ePTFE membrane or band relief, leading to obstruction [4]. However, the precise mechanisms underlying seroma formation remain elusive. This complication has been sporadically reported with various devices, including the HVAD, HeartMate (HM) II (Abbott, Chicago, IL, USA), and HM 3 (Abbott).

Several factors have been identified as increasing the risk of eOGO. These include long-term LVAD support, the use of an extended outflow graft, graft kinking, and the presence of a large gap between the bend relief and the outflow graft. Prolonged LVAD support is generally associated with an elevated risk of eOGO [1,5]. In one study, the rates of eOGO following HM 3 support were 0.6% at 1 year, 2.8% at 2 years, 4% at 3 years, and 9.1% at 5 years [1]. This risk also varies across institutions, with higher-volume centers experiencing a higher frequency of heart transplantation and shorter durations of support, potentially decreasing the rate of eOGO. Initially, the patient in the present report underwent LVAD implantation as a bridge to candidacy. However, since the patient’s blood type was O and he was over 70 years old, heart transplantation was not pursued. Consequently, the patient remained on LVAD support.

Graft kinking may lead to increased pressure prior to twisting, potentially resulting in oozing and the accumulation of a gelatinous substance [1]. With the HM II, such accumulation has been observed in response to a gap present between the bend relief and the outflow graft. The HM 3 is generally known to have a larger space between the bend relief and outflow graft compared to the HVAD [2,6]. However, in the present case, accumulation occurred between the ePTFE and outflow grafts. At our institution, it is standard practice to wrap the distal outflow graft in Gore- Tex grafts or membranes in bridge-to-transplant patients. This leaves substantial space between this graft or membrane and the outflow graft, which may have contributed to the observed accumulation and resulting obstruction.

In its early stages, eOGO can present with a variety of symptoms, including low-flow alerts, dyspnea, shock, anemia, arrhythmia, right heart failure, angina pectoris, and pulmonary edema. However, these symptoms are not specific to eOGO, underscoring the importance of early suspicion and diagnosis. Accurate diagnosis typically necessitates the use of CT or angiography, and treatment is generally required for patients who exhibit more than 50% obstruction or who are symptomatic. While the need for routine surveillance is a subject of debate, outflow graft stenosis is frequently identified during such monitoring [2,5]. However, cases with hemodynamic significance are rare. Emergencies can arise when symptoms appear suddenly, with a rapid decrease in pump flow; a failure to diagnose under these circumstances can have fatal consequences [1,2].

Three treatment options exist to address clinically significant eOGO: urgent heart transplantation, surgical decompression, and stent placement [1]. One study demonstrated favorable outcomes of endovascular treatment, which is a convenient alternative to invasive surgery for patients at high risk [7]; however, a risk exists of late failure or recurrence, particularly in areas not supported by stents [2]. Stent placement can induce twisting of the outflow graft, resulting in reduced pump flow and necessitating emergency surgical intervention [2]. In contrast, surgical decompression and debridement involve removal of the covering and associated biodebris. This method differs from stenting and carries a reduced risk of restenosis, especially in tight spaces [2]. In the present case, extensive stenosis throughout the outflow graft rendered stent placement impractical. Furthermore, given the severity of stenosis near the obstruction site and the difficulty of addressing it with stent placement without removing the surrounding compressive materials, surgical intervention was considered more suitable. Additionally, due to the comparatively high risk of recurrence associated with stent placement, a surgical approach was chosen.

Various modifications to the protective graft and surgical technique have been proposed, including the use of a less constrictive or fenestrated protective wrap, an additional incision to allow fluid to escape, or a more lateral placement of the outflow graft with an adjusted surgical configuration and without the use of a protective wrap [8]. When securing the outflow graft covering with sutures, it is crucial to avoid overtightening and to incorporate multiple perforations to create a longitudinal opening. This strategy is designed to prevent the accumulation of gelatinous material between the outflow graft and its covering, thereby reducing the risk of external outflow graft obstruction.

At our institute, outflow graft wrapping is performed for heart transplant candidates in preparation for redo sternotomy. For non-heart transplant candidates, this wrapping is omitted from the protocol. When implementing outflow graft wrapping for redo sternotomy preparation, a longitudinal opening is created prior to the application of the wrap. Throughout this process, care is taken to ensure sufficient space between the outflow graft and adjacent structures to avoid compression or undue constriction. Furthermore, the length of the graft is adjusted to reposition the outflow graft laterally, which helps minimize the risk of outflow graft obstruction.

This case illustrates that surgical decompression can be performed both safely and effectively. Furthermore, we recommend exercising caution to avoid wrapping the outflow graft, particularly in patients receiving long-term LVAD support, due to the potential risk of obstruction.

Author contributions

Conceptualization: SMK, IP, JHY. Data curation: SMK, IP, KS. Project administration: YHC. Visualization: SMK, IP, YHC. Writing–original draft: SMK, IP. Writing–review & editing: all authors. Final approval of the manuscript: YHC.

Conflict of interest

No potential conflict of interest relevant to this article was reported.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.