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Biomedical subjects

Lawrence H Cohn

Publications and source records attributed to Lawrence H Cohn.

At least 19 recordsLinked to original sources
PubMed2007

Lymphatic drainage of the peritoneal space: a pattern dependent on bowel lymphatics.

BACKGROUND: Understanding lymph drainage patterns of the peritoneum could assist in staging and treatment of gastrointestinal and ovarian malignancies. Sentinel lymph nodes (SLNs) have been identified for solid organs and the pleural space. Our purpose was to determine whether the peritoneal space has a predictable lymph node drainage pattern. METHODS: Rats received intraperitoneal injections of near-infrared (NIR) fluorescent tracers: namely, quantum dots (designed for retention in SLNs) or human serum albumin conjugated with IRDye800 (HSA800; designed for lymphatic flow beyond the SLN). A custom imaging system detected NIR fluorescence at 10 and 20 minutes and 1, 4, and 24 hours after injection. To determine the contribution of viscera to peritoneal lymphatic flow, additional cohorts received bowel resection before NIR tracer injection. Associations with appropriate controls were assessed with the chi(2) test. RESULTS: Quantum dots drained to the celiac, superior mesenteric, and periportal lymph node groups. HSA800 drained to these same groups at early time points but continued flowing to the mediastinal lymph nodes via the thoracic duct. After bowel resection, both tracers were found in the thoracic, not abdominal, lymph node groups. Additionally, HSA800 was no longer found in the thoracic duct but in the anterior chest wall and diaphragmatic lymphatics. CONCLUSIONS: The peritoneal space drains to the celiac, superior mesenteric, and periportal lymph node groups first. Lymph continues via the thoracic duct to the mediastinal lymph nodes. Bowel lymphatics are a key determinant of peritoneal lymph flow, because bowel resection shifts lymph flow directly to the intrathoracic lymph nodes via chest wall lymphatics.

Animals↗
PubMed2006

Suture bicuspidization of the tricuspid valve versus ring annuloplasty for repair of functional tricuspid regurgitation: midterm results of 237 consecutive patients.

OBJECTIVE: Uncorrected functional tricuspid regurgitation has serious long-term morbidity and mortality. We reviewed our experience with tricuspid posterior annular bicuspidization versus ring tricuspid annuloplasty for treatment of functional tricuspid regurgitation. METHODS: From 1999 to 2003, 237 patients underwent tricuspid annuloplasty for functional tricuspid regurgitation as part of their cardiac surgical procedure. Bicuspidization was performed in 157 patients and ring annuloplasty in 80 patients. Preoperatively, 227 (96%) patients had moderate or greater tricuspid regurgitation with a median regurgitation of 3+. Follow-up information was obtained for 234 (99%) patients with a mean follow-up time of 3 years. Postoperative transthoracic echocardiograms were assessed for severity of tricuspid regurgitation. Moderate or greater tricuspid regurgitation was considered significant. Survival and development of recurrent tricuspid regurgitation were evaluated by Kaplan-Meier analysis. Tricuspid regurgitation and risk factors for recurrent regurgitation were identified and analyzed by multivariable ordinal longitudinal methods. RESULTS: At 3 years postoperatively, tricuspid regurgitation in patients treated by bicuspidization annuloplasty was zero to mild in 75%, moderate in 11%, moderate to severe in 6%, and severe in 8% of patients. In those undergoing ring annuloplasty, tricuspid regurgitation was zero to mild in 69%, moderate in 14%, moderate to severe in 7%, and severe in 10%. There was no significant difference between the two groups (P = .18). Risk factors for recurrent tricuspid regurgitation included higher preoperative regurgitation grade, preoperative tricuspid regurgitation without concomitant mitral regurgitation, and higher pulmonary artery systolic pressure. CONCLUSIONS: Bicuspidization annuloplasty and ring annuloplasty were effective at eliminating tricuspid regurgitation at 3 years postoperatively. Bicuspidization annuloplasty is a simple, inexpensive option for addressing functional tricuspid regurgitation. All patients with moderate-to-severe functional tricuspid regurgitation should undergo tricuspid annuloplasty regardless of the technique used.

Adult↗
PubMed2006

Effectiveness of same day percutaneous coronary intervention followed by minimally invasive aortic valve replacement for aortic stenosis and moderate coronary disease ("hybrid approach").

In 2005, the investigators described a "hybrid" cardiovascular interventional strategy combining percutaneous coronary intervention (PCI) for coronary artery disease (CAD) followed by valve surgery for patients with urgent complex CAD and valve disease to reduce morbidity and mortality. This hybrid approach has been extended prospectively in elderly, high-risk patients with aortic stenosis scheduled for elective minimally invasive aortic valve replacement (MI-AVR) who, on preoperative coronary angiography, were found to have moderate CAD amenable to PCI. In this prospective, observational series, 18 patients (mean age 76 years) underwent elective hybrid MI-AVR with PCI from May 2003 to February 2006. Five patients had undergone previous coronary artery bypass grafting. Patients underwent coronary angiography the day of (n = 12) or evening before (n = 6) MI-AVR, and after identifying moderately severe CAD, all 18 underwent the implantation of drug-eluting stents to the affected coronary arteries, followed by MI-AVR. Although all patients received standard doses of antiplatelet medications, including acetylsalicylic acid (325 mg before PCI and 325 mg/day thereafter) and clopidogrel (300 mg after PCI, 75 mg/day thereafter for 90 days for the Cypher stent), there were no reoperations for bleeding; only 8 of 18 patients required postoperative blood transfusions. One patient died postoperatively from a colonic perforation, and there were no late mortalities after a mean follow-up of 19 months. In conclusion, this hybrid strategy has low morbidity and mortality and may be a new therapeutic option for older, high-risk patients with combined CAD and aortic valve disease.

Aged↗
PubMed2006

Sentinel lymph node mapping of the gastrointestinal tract by using invisible light.

BACKGROUND: Because many gastrointestinal (GI) tumors spread by way of lymphatics, histological assessment of the first draining lymph nodes has both prognostic and therapeutic significance. However, sentinel lymph node mapping of the GI tract by using available techniques is limited by unpredictable drainage patterns, high background signal, and the inability to image lymphatic tracers relative to surgical anatomy in real time. Our goal was to develop a method for patient-specific intraoperative sentinel lymph node mapping of the GI tract by using invisible near-infrared light. METHODS: We developed an intraoperative near-infrared fluorescence imaging system that simultaneously displays surgical anatomy and otherwise invisible near-infrared fluorescence images of the surgical field. Near-infrared fluorescent quantum dots were injected intraparenchymally into the stomach, small bowel, and colon, and draining lymphatic channels and sentinel lymph nodes were visualized. Dissection was performed under real-time image guidance. RESULTS: In 10 adult pigs, we demonstrated that 200 pmol of quantum dots quickly and accurately map lymphatic drainage and sentinel lymph nodes. Injection into the mid jejunum and colon results in fluorescence of a single lymph node at the root of the bowel mesentery. Injection into the stomach resulted in identification of a retrogastric node. Histological analysis in all cases confirmed the presence of nodal tissue. CONCLUSIONS: We report the use of invisible near-infrared light for intraoperative sentinel lymph node mapping of the GI tract. This technology overcomes the limitations of currently available methods, permits patient-specific imaging of lymphatic flow and sentinel nodes, and provides highly sensitive, real-time image-guided dissection.

Animals↗
PubMed2006

Optimal surgical management of severe tricuspid regurgitation in cardiac transplant patients.

BACKGROUND: Severe tricuspid regurgitation (TR) with signs of right-sided heart failure is rare after orthotopic heart transplantation (OHT). In some instances, this condition will require surgical correction using reconstructive surgery or prosthetic valve replacement. Repair techniques of atrioventricular valves are now well described. However, the results of the different surgical procedures in this setting have not been widely reported and may depend on the type of valvular dysfunction and lesions present. Herein we report our experience in a group of patients requiring surgical correction of symptomatic severe TR after OHT. METHODS: We reviewed our transplant experience during the period from July 1992 to July 1999 (n = 138 cardiac transplants). Eight patients (5.8%) developed symptomatic severe TR requiring surgical correction after a mean duration of 21 months after OHT. Patients were divided into 2 groups based on the mechanism of regurgitation using Carpentier's functional classification. In Group 1 (n = 4), the mechanism of tricuspid regurgitation was Carpentier's Type I, secondary to annular dilation. In Group 2 (n = 4) the mechanism of TR was leaflet prolapse (Type II), due to chordal rupture after biopsy injury. Initially, tricuspid valve integrity was surgically restored in all 8 patients with either valve repair (n = 6) or replacement (n = 2). In Group 1, 2 patients underwent valve repair using a ring annuloplasty and 2 patients underwent valve replacement with a bioprosthetic valve (n = 1) or pulmonary allograft (n = 1). In Group 2, all patients underwent valve repair using a variety of techniques in combination with tricuspid annuloplasty. RESULTS: During the follow-up period, 3 of the 6 (50%) primary repairs (1 patient in Group 1 and 2 in Group 2) failed and required replacement with a bioprosthesis at 8 days, 14 days and 4 years, respectively. The pulmonary allograft failed secondary to valvular stenosis and was replaced with a bioprosthesis after 10 months. Overall, no failures occurred in any of the 5 bioprosthetic valves placed at the primary operation (n = 1) or after failed tricuspid repair/pulmonary allograft (n = 4), after a mean follow-up of 55 months. CONCLUSIONS: TR requiring surgical correction after OHT is a rare condition and requires a tailored surgical strategy. This strategy should take into account the mechanism of valve dysfunction and specific valvular lesions. In patients with Type I dysfunction secondary to annular dilation, valve repair with a remodeling annuloplasty should be performed; however, in the presence of any residual TR on transesophageal echocardiography (TEE) at the completion of cardiopulmonary bypass (CPB), a valve replacement with a bioprosthesis is warranted during the same procedure. In patients with Type II dysfunction with leaflet prolapse and biopsy-induced chordal injury, a bioprosthetic valve replacement seems a reliable surgical option.

Adult↗
PubMed2006

Operative and long-term survival of elderly is significantly improved by mitral valve repair.

BACKGROUND: We review our 10-year experience of mitral valve (MV) repair in comparison with MV replacement in the elderly for floppy mitral valves/mitral valve prolapse (FMV/MVP). The use of MV repair for this entity has not been fully utilized by surgeons. METHODS: Two hundred ninety-two consecutive patients aged > or = 70 years receiving mitral surgery for regurgitation due to FMV/MVP were reviewed from our prospective database between January 1, 1992, and December 31, 2002. Patients receiving concomitant coronary artery bypass grafting (CABG) were included. Two hundred eighteen patients underwent repairs and 74 replacements. Postoperative and long-term follow-up data were obtained. Mean follow-up time for survivors was 6.2 +/- 2.5 years for MV repair and 6.8 +/- 2.7 years for MV replacement. RESULTS: Patients with isolated MV repair showed lower inhospital mortality compared with MV replacement (0.7% vs 13.9%, P = .002) with reduced length of stay (8.7 +/- 7.6 vs 9.6 +/- 5.2 days, P = .049). There was improvement in 5-year mortality favoring repair versus replacement (81% +/- 3% vs 63% +/- 3%, P = .001). With concomitant CABG, there was minimal difference in survival up to 5 years. Freedom from valve replacement was 93.9% +/- 1.3% for MV repair and 98.2% +/- 0.4% for MV repair with CABG at 10 years. Mitral valve repair was an independent protector of long-term mortality within multivariate correlates (hazard ratio 0.43, 95% CI 0.19-0.97, P = .041). CONCLUSIONS: In elderly patients, MV repair reduced in-hospital mortality and length of stay and increased long-term survival. With concomitant CABG, survival was similar to replacement. The preferred option for elderly patients with FMV/MVP is MV repair, especially in those without coronary artery disease.

Aged↗
PubMed2006

Replacement of the quadricuspid aortic valve: strategy to avoid complete heart block.

Quadricuspid aortic valves are rarely encountered by the cardiac surgeon during aortic valve replacement. The most common location for the supranumerary cusp is between the noncoronary and the right coronary cusp, located over the membranous septum, which can potentially increase the risk of complete heart block after valve replacement. We present three quadricuspid aortic valve replacements, one of which was complicated by complete heart block postoperatively. We suggest a strategy to possibly avoid this complication.

Adult↗
PubMed2006

Predicting survival in patients requiring renal replacement therapy after cardiac surgery.

BACKGROUND: We sought to develop and internally validate a prediction score for all-cause in-hospital mortality in patients who have acute renal failure and require renal replacement therapy after cardiac surgery. METHODS: From January 1992 to July 2001, 136 of 14,000 patients (0.9%) had acute renal failure requiring renal replacement therapy after cardiac surgery. Multivariate logistic regression analysis, based on pre-renal replacement therapy variables, was used to construct a predictive score for all causes of in-hospital mortality. Subsequently, the score was validated in 27 patients who underwent surgery between August 2001 and March 2003. RESULTS: In-hospital mortality was 58% (79 of 136). From the logistic regression model, we assigned a score (range, 0 to 6) based on the presence of independent predictors of operative mortality (preoperative creatinine < or = 1.5 mg/dL [odds ratio (OR) = 5.0], hypertension [OR = 4.4], predialysis coma [OR = 9.6], sepsis [OR = 6.4], and total bilirubin > or = 2 mg/dL [OR = 5.6]). Higher scores strongly predicted mortality: patients who scored 3 or higher before the initiation dialysis (n = 54), had a mortality rate of 94% (51 of 54). In contrast, patients who scored 1 or less on this scale (n = 36), had a mortality of 16% (6 of 36). In the validation cohort, the sensitivity of the new score at the cutoff of 2 or fewer points versus 3 or more points was 0.71, the specificity was 0.90, the positive predictive value was 0.92, and the negative predictive value was 0.64. CONCLUSIONS: The prediction score represents a simple and accurate tool for predicting in-hospital mortality associated with renal replacement therapy for cardiac surgery patients before the institution of this resource-intensive treatment.

Acute Kidney Injury↗
PubMed2006

Midterm results of the edge-to-edge technique for complex mitral valve repair.

BACKGROUND: The edge-to-edge technique (E2E) has been advocated for the complex repair of myxomatous mitral valves. We compared outcomes of E2E performed in patients at risk for systolic anterior motion (SAM) versus outcomes in patients with residual mitral regurgitation (MR) after repair completion. METHODS: A total of 1,612 patients had repair of myxomatous mitral valves between June 1997 and December 2003 at Brigham and Women's Hospital. The E2E was used in 72 (4.5%) patients. Fifty-two patients (52/72; group I) had E2E for persistent MR after complex repair. Twenty patients (20/72; group II) had E2E for high risk of post-repair SAM and left ventricular outflow tract obstruction. Mean age of the patients was 61 +/- 14 years; 47 were male, average New York Heart Association class at admission was 2.4 +/- 0.6, and mean left ventricular ejection fraction was 56 +/- 12%. RESULTS: The operative mortality was zero. Immediate postoperative MR was significantly improved in all patients compared with the preoperative grade (p value < 0.0005). Mean follow-up was 388 days. In those in whom E2E was used for residual MR without SAM risk (group I), postoperative MR (> or = 2+) was detected in 15 of 52 patients at 6 months. In group II, SAM was completely eliminated and the mean MR grade in the immediate postoperative period was 0.5 +/- 0.7. There was no long-term recurrence of MR in group II. CONCLUSIONS: This study suggests that E2E eliminates SAM and long-term MR in patients with pre-repair echocardiographic predictors of SAM. The E2E is not efficacious in preventing long-term recurrent MR if performed for residual MR after complex mitral repair.

Aged↗
PubMed2006

Minimally invasive approaches to aortic valve surgery: Brigham experience.

Aortic valve surgery is a proven and effective therapy for severe aortic stenosis and insufficiency. Conventional aortic valve surgery is performed with a full sternotomy, cardiopulmonary bypass, and replacement of the diseased aortic valve. Unlike minimally invasive (or "off-pump") coronary artery bypass, minimally invasive aortic valve surgery still requires cardiopulmonary bypass but refers primarily to smaller incisions and access. Minimally invasive approaches to aortic valve surgery have evolved over the past decade and have become the standard in institutions that perform large-volume minimally invasive cardiac surgery. The upper hemisternotomy has become our standard approach to isolated aortic valve surgery. It is a safe and effective technique with a similar morbidity and mortality to conventional aortic valve surgery. Patients derive clear benefits from this minimally invasive approach including less pain, shorter length of hospital stay, and faster return to preoperative function levels.

Adult↗
PubMed2006

Future directions in cardiac surgery.

The future of cardiac surgery is interesting, challenging, and changing. In coronary artery disease, operations are becoming more difficult due to previous stent placement and population aging, but there is a sense that volume is increasing, especially in centers that perform operations for diffuse disease and those that can perform truly minimally invasive procedures with robotic takedown of mammary arteries and perform anastomoses thoracoscopically. In valve disease, there will be increasing numbers of elderly patients requiring surgery, especially for aortic valve disease; a combination of minimally invasive surgery, hybrid procedures, and perhaps percutaneous valve placement in the truly high risk will be required. Mitral valve repair will become increasingly used as well as some percutaneous valve devices. In 5 years, most thoracic aneurysms will be treated by endovascular stenting and adults with congenital disease will be a small but growing population of patients.

Aortic Diseases↗
PubMed2005

Direct-access valve replacement a novel approach for off-pump valve implantation using valved stents.

OBJECTIVES: This study validates the off-pump antegrade transventricular route for ultrasound-guided direct-access aortic valved stent implantation. BACKGROUND: Direct-access aortic valved stent implantation offers numerous advantages over the remote-access percutaneous approach and may one day provide an alternative to surgical aortic valve replacement. METHODS: Valved stents were implanted off-pump in 12 pigs (68.5.0 +/- 7.3 kg) via direct-access transapical approach using a left-sided mini-thoracotomy and continuous ultrasonic and fluoroscopic guidance. Acute valved stent function was studied with intravascular and intracardiac ultrasound. All valved stents were tested in vitro before insertion. Macroscopic analysis was performed at necropsy. RESULTS: In 8 of 12 pigs, valved stents were delivered to the target site over the native aortic valve leaflets without interference of coronary blood flow and with good acute valve function. Two valved stents were deployed and supra-annularly occluded the coronary orifice, leading to fatal outcome. Two valved stents dislodged into the left ventricle, one because of size mismatch and one that failed to unfold correctly. CONCLUSIONS: Twelve pigs underwent deployment of a valved stent in the aortic position. Six valves observed for an average 4.5-h period showed satisfactory postimplantation valve function.

Animals↗