The efficacy of hydrogel foams in talc Pleurodesis.

BACKGROUND: Malignant pleural effusions are a serious complication of many late stage cancers that adversely affect quality of life. Pleurodesis with talc slurry is a standard treatment option, but clinical failures occur, possible due to poor talc delivery. A novel drug-delivery system was developed that fills the entire thoracic cavity with a liquid foam containing talc. The foam is designed to gel and adhere to the tissue walls at body temperature, to improve talc deposition and efficacy. METHODS: Rheology, foam stability, and ex-vivo coating and bio-adhesion studies were performed on three concentrations of a novel hydrogel talc foam system that was developed to improve delivery of talc to the pleural surfaces. A New Zealand rabbit model of pleurodesis was used to evaluate effectiveness of the foams at inducing adhesion formation and compared to talc slurry. The rabbits were recovered after they had one of the test agents instilled into their pleura, and then sacrificed after 28 days. Pleurodesis was assessed by a blinded pathologist using a standardized pathological scoring system. RESULTS: All talc foam formulations produced foams that gelled at physiological temperatures and were relatively stable for at least two hours. As the concentration of the formulation increased the gelation temperature decreased and the foam adhesiveness increased. Rabbits that received talc foam had significantly greater adhesion formation than talc slurry (mean score of 2.21 vs. 1.18 (p < 0.05)). Rabbits that received the 20% foam developed the most adhesions. CONCLUSIONS: This study demonstrates that our triblock copolymer hydrogel foam delivery system enhances adhesion formation in an experimental model. This novel approach can have important clinical impact, potentially improving efficacy of existing therapies and reducing the need for more invasive treatments.

An improved method of delivering a sclerosing agent for the treatment of malignant pleural effusion.

BACKGROUND: Malignant pleural effusion (MPE) is a devastating sequela associated with cancer. Talc pleurodesis is a common treatment strategy for MPE but has been estimated to be unsuccessful in up to 20-50% of patients. Clinical failure of talc pleurodesis is thought to be due to poor dispersion. This monograph reports the development of a foam delivery system designed to more effectively coat the pleural cavity. METHODS: C57BL/6 mice were injected with Lewis lung carcinoma (LL/2) cells intrapleurally to induce MPE. The mice then received either normal saline (NS) control, foam control (F), talc slurry (TS, 2 mg/g) or talc foam (TF, 2 mg/g). Airspace volume was evaluated by CT, lungs/pleura were collected, and percent fibrosis was determined. RESULTS: The TF group had significantly better survival than the TS group (21 vs 13.5 days, p < 0.0001). The average effusion volume was less in the talc groups compared to the control group (140 vs 628 µL, p < 0.001). TF induced significant lung fibrosis (p < 0.01), similar to TS. On CT, TF significantly (p < 0.05) reduced loss of right lung volume (by 30-40%) compared to the control group. This was not seen with TS (p > 0.05). CONCLUSIONS: This report describes using a novel talc foam delivery system for the treatment of MPE. In the LL/2 model, mice treated with the TF had better survival outcomes and less reduction of lung volume than mice treated with the standard of care TS. These data provide support for translational efforts to move talc foam from animal models into clinical trials.

A Novel Technique for Experimental Flow Visualization of Mechanical Valves.

The geometry of the hinge region in mechanical heart valves has been postulated to play an important role in the development of thromboembolic events (TEs). This study describes a novel technique developed to visualize washout characteristics in mechanical valve hinge areas. A dairy-based colloidal suspension (DBCS) was used as a high-contrast tracer. It was introduced directly into the hinge-containing sections of two commercially available valves mounted in laser-milled fluidic channels and subsequently washed out at several flow rates. Time-lapse images were analyzed to determine the average washout rate and generate intensity topography maps of the DBCS clearance. As flow increased, washout improved and clearance times were shorter in all cases. Significantly different washout rate time constants were observed between valves, average >40% faster clearance (p < 0.01). The topographic maps revealed that each valve had a characteristic pattern of washout. The technique proved reproducible with a maximum recorded standard error of mean (SEM) of ±3.9. Although the experimental washout dynamics have yet to be correlated with in vivo visualization studies, the methodology may help identify key flow features influencing TEs. This visualization methodology can be a useful tool to help evaluate stagnation zones in new and existing heart valve hinge designs.

Percutaneous repair of post-myocardial infarction ventricular septal defect: current approaches and future perspectives.

Post-myocardial infarction ventricular septal defect is a devastating complication of ST-elevation myocardial infarction. Although surgical intervention is considered the gold standard for treatment, it carries high morbidity and mortality rates. We present 2 cases that illustrate the application of percutaneous closure of a post-myocardial infarction ventricular septal defect: the first in a patient who had undergone prior surgical closure and then developed a new shunt, and the second as a bridge to definitive surgery in a critically ill patient.

Coronary artery bypass via resternotomy after pectus excavatum repair.

Pectus excavatum is a chest wall deformity that commonly warrants pediatric surgical correction for cosmesis or respiratory impairment via sternotomy. The repair typically consists of sternal wedge osteotomy and subsequent placement of a Steinman pin across the sternum with fixation to the ribs bilaterally. Coronary artery bypass grafting (CABG) after surgical repair of the sternum with a metal implant poses an intriguing surgical challenge. Literature review reveals only one such previously described case. We present a case of coronary revascularization in an adult who previously underwent pectus excavatum repair with ligation of the internal mammary arteries. Our coronary revascularization was accessed through a resternotomy after surgical removal of the metal implant previously placed during the pectus excavatum repair. Autologous greater saphenous vein was used as a conduit for bypass. The patient did well postoperatively and was discharged on postoperative day 4. The pectus repair remained intact even after the median sternotomy was performed. This was confirmed at the 1-year follow-up for the patient. Resternotomy after pectus excavatum repair with a prosthetic implant poses a challenge to cardiothoracic surgeons. Many such repairs have been described in the pediatric population. As our society ages and coronary artery disease becomes more prevalent, this unique situation may be more commonly encountered. We present an approach to coronary artery bypass grafting via median resternotomy after pectus excavatum repair.

Thoracoscopic resection of unusual symptomatic pericardial cysts.

Pericardial cysts are mediastinal tumors that usually have a benign course. Diagnostic and therapeutic thoracoscopy are warranted for suspect mediastinal masses, unsuccessful nondiagnostic less invasive procedures, and symptomatic unusually located pericardial cysts. We report a case of thoracoscopic resection of symptomatic pericardial cysts.