A novel treatment for the midaortic syndrome

Surgical management of pediatric renovascular hypertension and midaortic syndrome at a single-center multidisciplinary program

OBJECTIVE

To evaluate the outcomes of various surgical approaches in the treatment of renovascular hypertension and midaortic syndrome (MAS) in children.

METHODS

We performed a retrospective medical record review of patients who had undergone surgery for renovascular hypertension from 2010 to 2018 at our center under the care of a multidisciplinary team. The operative interventions included mesenteric artery growth improves circulation (MAGIC), tissue expander-stimulated lengthening of arteries (TESLA), aortic bypass using polytetrafluorethylene, renal artery reimplantation, and autotransplantation. The MAGIC procedure uses the meandering mesenteric artery as a free conduit for aortic bypass. The TESLA procedure is based on lengthening the normal distal aorta and iliac arteries by gradual filling of a retroaortic tissue expander for several weeks, followed by resection of the stenotic aorta and subsequent primary reconstruction.

RESULTS

A total of 39 patients were identified, 10 with isolated renal artery stenosis, 26 with MAS, and 3 with systemic inflammatory vasculitis. The median age at presentation and surgery was 6.4 years (range, 0-16.3 years) and 9.3 years (range, 0-9.2 years), respectively. The MAS-associated syndromes included neurofibromatosis type 1 (15.4%) and Williams syndrome (5.1%), although most cases were idiopathic. At surgery, 33.3% had had stage 1 hypertension (HTN), 53.8% stage 2 HTN, and 12.8% normal blood pressure with a median of three antihypertensive medications. Follow-up of 37 patients at a median of 2.5 years demonstrated normal blood pressure in 86.1%, stage 1 HTN in 8.3%, and stage 2 HTN in 5.6%, with a median of one antihypertensive medication for the entire cohort.

CONCLUSIONS

The patterns of vascular involvement leading to renovascular hypertension in children are variable and complex, requiring thoughtful multidisciplinary planning and surgical decision-making. The MAGIC and TESLA procedures provide feasible approaches for aortic bypass and reconstruction using autologous tissues and will result in normalization of blood pressure in 85% of children 2.5 years after surgery.

Regenerative robotics

Congenital diseases requiring reconstruction of parts of the gastrointestinal tract, skin, or bone are a challenge to alleviate especially in rapidly growing children. Novel technologies may be the answer. This article presents the state-of-art in regenerative robotic technologies, which are technologies that assist tissues and organs to regenerate using sensing and mechanotherapeutical capabilities. It addresses the challenges in the development of such technologies, among which are autonomy and fault-tolerance for long-term therapy as well as morphological conformations and compliance of such devices to adapt to gradual changes of the tissues in vivo. The potential as medical devices for delivering therapies for tissue growth and as tools for scientific exploration of regenerative mechanisms is also discussed.

Severe midaortic syndrome: a stepwise approach to treatment with drug-eluting balloons: a case report

Background

Severe forms of the midaortic syndrome cause persistent arterial hypertension and can lead to angina abdominalis. Untreated, morbidity, and mortality are significant. In addition to palliation through bypass surgery, few other therapeutic approaches lead to a long-term relief. Drug-eluting balloons (DEB) covered with paclitaxel, a cytostatic drug, have proven to be effective in bifurcational lesions and for in-stent stenoses in coronary arteries.

Case summary

In a 15-year-old girl with severe midaortic syndrome and multiple collateral arteries, four interventional balloon dilatations with DEB of increasing diameters resolved the stenosis within 8 months. After a procedure free interval of now 2.7 years, the anatomical and the physical condition of the patient remained unchanged.

Discussion

This stepwise approach, with a low procedural risk and a lasting result may justify further investigations into this combined treatment.

Strain induced esophageal growth in a novel rodent model

PURPOSE

Longitudinal esophageal strain has been shown to increase esophageal length but the contribution of tissue hyperplasia to this growth is unknown. We used a novel model of esophageal stretch to determine the cellular response to the strain stimulus.

METHODS

Male Sprague-Dawley rats underwent transection of the distal esophagus. The distal stump was ligated and stretched over a silicone tube. The proximal esophageal stump was anastomosed to the stomach to restore continuity. After two, four, or seven days, the silicone tube was removed and the esophageal segment was measured and compared to its initial length. Sham animals had only a thin piece of silicone tubing placed. Standardized histologic sections were evaluated for wall thickness. Immunofluorescence with DAPI, Ki-67, and Myogenin antibodies was used to assess nuclear density, proliferation indices, and myoblast differentiation indices.

RESULTS

Experimental animals demonstrated a significant increase in esophageal length compared to sham controls at four and seven days with no difference at two days. There was significant lengthening between four and seven days among the experimental animals. There was no change in wall thickness between experimental and sham animals at any time point. Nuclear density was increased at all time points, although this only reached significance at day four. Proliferation indices were significantly increased relative to sham controls at all time points. Esophageal strain induced significantly increased myoblast differentiation.

CONCLUSION

In this novel rat model of esophageal strain, lengthening is associated with stable esophageal wall thickness, increased nuclear density, increased cellular proliferation, and increased myogenin expression. These data suggest that true tissue hyperplasia may contribute to the increased length seen after esophageal strain.

Tissue expander stimulated lengthening of arteries (TESLA) induces early endothelial cell proliferation in a novel rodent model

BACKGROUND

We examine the mechanism of aortic lengthening in a novel rodent model of tissue expander stimulated lengthening of arteries (TESLA).

METHODS

A rat model of TESLA was examined with a single stretch stimulus applied at the time of tissue expander insertion with evaluation of the aorta at 2, 4 and 7day time points. Measurements as well as histology and proliferation assays were performed and compared to sham controls.

RESULTS

The aortic length was increased at all time points without histologic signs of tissue injury. Nuclear density remained unchanged despite the increase in length suggesting cellular hyperplasia. Cellular proliferation was confirmed in endothelial cell layer by Ki-67 stain.

CONCLUSIONS

Aortic lengthening may be achieved using TESLA. The increase in aortic length can be achieved without tissue injury and results at least partially from cellular hyperplasia. Further studies are required to define the mechanisms involved in the growth of arteries under increased longitudinal stress.

Aortic bypass and orthotopic right renal autotransplantation for midaortic syndrome: a case report

Background

Midaortic syndrome (MAS) is a rare vascular anomaly characterized by segmental narrowing of the distal descending thoracic or abdominal aorta. Renal or visceral arteries may also be affected to varying degrees. MAS is often associated with renovascular hypertension, and requires early intervention. When medical therapy and percutaneous interventions fail to control hypertension, surgical treatment is required. We report a case of MAS that failed to respond to bilateral renal artery stenting, but treated with aortic bypass and orthotopic right renal autotransplantation with good outcome.

Case presentation

A 31-year-old woman presented with headache and poorly controlled hypertension due to severe MAS. She had severe ostial stenoses of renal and visceral arteries. Her hypertension failed to respond to medical therapy (four drugs) and bilateral renal artery stenting. The implanted stent in the right renal artery rendered revascularization of the artery difficult. A one-stage revascularization was performed, which consisted of an aortoaortic bypass (between the suprarenal and infrarenal abdominal aorta) with a prosthetic graft, an orthotopic right renal autotransplantation and an aorto-left renal arterial bypass with autogenous saphenous vein grafts. Her recovery was uneventful. At 1-year follow-up, the patient remained well. Her hypertension improved. A postoperative computed tomography angiography showed that all the grafts were patent with no abnormalities at the anastomosis.

Conclusion

Multiple bypass surgery with reimplantation of autogenous vein graft onto the prosthetic graft is a feasible and effective procedure in renal artery revascularization for MAS. Orthotopic autotransplantation is the procedure of choice in complex renal artery reconstruction.

Function of mechanically lengthened jejunum after restoration into continuity

PURPOSE

Distraction enterogenesis is a potential treatment for patients with short bowel syndrome. We previously demonstrated successful lengthening of jejunum using a degradable spring device in rats. Absorptive function of the lengthened jejunum after restoration into intestinal continuity needs to be determined.

METHODS

Encapsulated polycaprolactone springs were placed into isolated jejunal segments in rats for four weeks. Lengthened segments of jejunum were subsequently restored into intestinal continuity. Absorption studies were performed by placing a mixture of a non-absorbable substrate and glucose into the lumen of the restored jejunum.

RESULTS

Restored jejunal segments demonstrated visible peristalsis at specimen retrieval. Compared to normal jejunal controls, restored segments demonstrated equal water absorption and greater glucose absorption. Restored segments had thicker smooth muscle, increased villus height, increased crypt depth, and decreased sucrase activity compared to normal jejunum. The density of enteric ganglia increased after restoration to near normal levels in the submucosa and to normal levels in the myenteric plexus.

CONCLUSION

Jejunum lengthened with a degradable device demonstrates peristaltic and enzymatic activity as well as glucose and water absorption after restoration into intestinal continuity. Our findings further demonstrate the therapeutic potential of a degradable device.

A novel biodegradable device for intestinal lengthening

PURPOSE

Previous studies demonstrated successful mechanical lengthening of rat jejunum using an encapsulated Nitinol spring device over a stabilizing guidewire. We sought to improve the applicability of intestinal lengthening by creating a biodegradable device.

METHODS

Using properties of the Nitinol spring device, polycaprolactone (PCL) springs with similar outer diameter and spring constant were created. After in vitro testing in dry and hydrated environments, they were used to lengthen 1-cm isolated segments of rat jejunum in vivo. Retrieved segments were analyzed histologically.

RESULTS

Optimal PCL spring devices had an average spring constant 1.8 ± 0.4 N/m, pitch 1.55 ± 0.85 mm, and band width 0.825 ± 0.016 mm. In vitro testing demonstrated stable spring constants. Jejunal segments were lengthened from 1.0 cm to 2.7 ± 0.4 cm without needing a stabilizing guidewire. Histology demonstrated increased smooth muscle thickness and fewer ganglia compared to controls. Lengthened jejunum was successfully restored into intestinal continuity and demonstrated peristalsis under fluoroscopy.

CONCLUSIONS

A novel biodegradable spring device was successfully created and used to mechanically lengthen intestinal segments. Use of a biodegradable device may obviate the need for retrieval after lengthening. This improves device applicability and may be useful for the treatment of short bowel syndrome.

Midaortic syndrome: 30 years of experience with medical, endovascular and surgical management

BACKGROUND

Midaortic syndrome is often associated with refractory hypertension. The aim of our study was to better understand the short- and medium-term outcomes in this patient population utilizing a multidisciplinary management approach.

METHODS

We conducted a review of patients with midaortic syndrome treated at our institution over the past 30 years.

RESULTS

Fifty-three patients presented at a median age of 6.7 years (birth to 28.7 years). Thirty-five patients (66 %) underwent invasive management (percutaneous techniques: 21; surgical techniques: 5; both: 9). Percutaneous interventions were acutely successful in decreasing the gradient across the obstruction and degree of luminal stenosis. However, freedom from reintervention was 58 % at 1 year and 33 % at 5 years. Freedom from reintervention after a surgical procedure was longer: 83 % at 1 year and 72 % at 10 years. At the most recent follow-up, the majority of patients (69 %) were normotensive. The median duration between time of presentation and achievement of blood pressure control was 5.7 (0.4-21.1) years. The median number of anti-hypertensive medications was 1 (0-5).

CONCLUSIONS

A multidisciplinary management strategy which couples comprehensive medical management with catheter-based and surgical interventions can lead to adequate blood pressure control and preservation of end-organ function in patients with midaortic syndrome.