Search PubMed⌕ Search

Biomedical subjects

L H Cohn

Publications and source records attributed to L H Cohn.

339 records · Page 19Linked to original sources
PubMedDate not supplied

Orthotopic pulmonic valve replacement with a pulmonary homograft as an interposition graft.

Pulmonary regurgitation (PR) following nonvalved reconstruction of the right ventricular outflow tract is usually well tolerated. However, a small percentage of patients develop progressive right ventricular dilatation and failure due to long-standing PR. When this group of patients becomes refractory to medical management, pulmonic valve replacement (PVR) may offer symptomatic relief and hemodynamic improvement. From a cumulative experience, the pulmonary homograft may be the optimal choice for PVR due to its very low transvalvular gradient assuring optimal hemodynamics, the absence of anticoagulation-related and thromboembolic complications, and the excellent mid-term results when compared to other valved conduit, including the aortic homograft. We report our experience in two patients who have been operated upon at the BWH between March and August 1995 for severe pulmonary valve insufficiency and right heart failure, who received cryopreserved pulmonary homografts. We also describe our technique of PVR using a pulmonary homograft as an orthotopic root replacement.

Adult↗
PubMedDate not supplied

Minimally invasive direct access heart valve surgery.

We review our experience with minimally invasive direct access (MIDA) heart valve surgery in 518 patients. Two hundred fifty-two patients underwent MIDA aortic valve replacement (AVR) or repair and 266 underwent MIDA mitral valve repair or replacement. Among the 250 AVRs, 157 (63%) were men, aged 63.2 +/- 14.6 years, NYHA functional Class 2.4 +/- 0.8. The surgical approach was right parasternal in 36 (14%) or upper hemisternotomy in 216 (86%). There were four (2%) operative deaths. Perioperative complications included 14 (5.6%) reexplorations for bleeding, 7 (3%) chest wound infections, 5 (2%) strokes, and 1 (0.4%) external iliac vein injury. Follow-up was complete in 193 (77%) patients, with a mean follow-up of 12 +/- 8 months. Late complications included 2 (0.8%) nonfatal myocardial infarctions, 4 (2%) reoperations for, respectively, 2 pericardial complications, 1 paravalvar leak, and 1 infected valve. There were five (2%) late deaths from congestive heart failure, pneumonia, hemorrhage, aneurysm, and cancer. Mean follow-up NYHA Class was 1.4 +/- 0.6. For the 266 mitral patients, 145 (54.5%) were men, age 58.7 +/- 13.6 years, functional Class 2.3 +/- 0.5. The surgical approach was right parasternal in 195 (73%), lower hemisternotomy in 53 (20%), right submammary thoracotomy in 9 (3.4%), or full sternotomy through a small skin incision in 9 (3.4%). There were 2 (0.8%) operative deaths. Perioperative complications included 4 (1.5%) reoperations for bleeding, 4 (1.5%) strokes, and 5 (2%) wound infections, and 3 (1%) ascending aortic complications. Follow-up was complete in 202 (76%) patients with a mean follow-up of 9.5 +/- 6.4 months. Late complications included one (0.4%) nonfatal myocardial infarction and three (1%) reoperations all converting repairs to replacements. There were three (1%) late deaths from suicide, pneumonia, and sudden death, respectively. Mean follow-up NYHA functional Class was 1.3 +/- 0.5. We conclude that MIDA heart valve surgery is safe and effective for the majority of patients requiring isolated elective aortic or mitral valve surgery.

Adolescent↗
PubMedDate not supplied

Minimally invasive valve surgery.

BACKGROUND: Cardiac surgery has been the last area of clinical surgery to adopt and embrace minimally invasive surgical techniques. Since the onset of arterial embolectomy in 1965, arthroscopic knee surgery performed in 1975 and laparoscopic cholecystectomy in 1985, huge advances in videoscopic, thorascopic and small incision surgery has taken place in all specialties which now allow change in the traditional approaches to cardiac valve surgery. In 1996, the Brigham and Women's Hospital, along with other units, began minimally invasive cardiac valve surgery for patients who had isolated valve pathology without coronary disease. Our experience now totals 689 patients, including 353 minimally invasive mitral valve repair/replacements and 336 minimally invasive aortic valve replacements, including root replacement and reoperations. METHODS: This new operative approach involves smaller incisions, the mandatory use of transesophageal echocardiogram for the monitoring of operation quality and air removal, newer perfusion techniques and some modifications in the standard valve repair/replacement techniques. With this blending of TEE, better perfusion techniques and new exposure, the safety and quality of valve operations by these techniques have been excellent. RESULTS AND CONCLUSION: The operative mortality is equal to (AVR) or less than (MVP) conventional open sternotomy cases and there is a shorter length of stay in the ICU and post-ICU, leading to a lower cost than conventional procedures. There are also less blood transfusions, atrial fibrillation and posthospital rehabilitation requirements, and patients have indicated that there is a faster return to normality over the conventional operative approaches. This brief report summarizes our experience from July, 1996 to January 2001.

Heart Valve Diseases↗
PubMedDate not supplied

An engineering model of dynamic cardiomyoplasty. II. Clinical applications.

Previously, a modification to the Sunagawa engineering model for the isolated left ventricle and arterial system was proposed and validated for dynamic cardiomyoplasty in an acute goat preparation. To test the hypothesis that this model may be applied to the clinical scenario in cardiomyoplasty patients, we predicted human stroke volume using the model with human clinical data from the literature. Predicted stroke volume correlated well with published stroke volume in patients who have had the dynamic cardiomyoplasty procedure. These results suggest that the modest hemodynamic improvement commonly reported after the procedure is performed may be due to diminished latissimus dorsi strength after transformation. The validity of both the original Sunagawa model and the previously proposed modification for dynamic cardiomyoplasty is further supported with these results. A nomogram methodology for predicting stroke volume after dynamic cardiomyoplasty for any particular patient is presented.

Biomechanical Phenomena↗
PubMedDate not supplied

An engineering model of dynamic cardiomyoplasty. I.

Dynamic cardiomyoplasty (DCM) is an emerging surgical procedure for heart failure in which the patient's latissimus dorsi (LD) muscle is wrapped around the heart and stimulated to contract in synchrony with the heartbeat as a cardiac assist measure. A 6 week training protocol of progressive electrical stimulation renders the normally fatigueable skeletal muscle fatigue-resistant and suitable for chronic stimulation. To date, over 500 procedures have been performed in worldwide clinical trials. Investigators typically report symptomatic improvement and modest hemodynamic improvement in patients. Controversy exists regarding the exact mechanism of DCM. To test the hypothesis that DCM augments cardiac stroke volume through improvement in systolic function, we formulated an engineering model of dynamic cardiomyoplasty to predict stroke volume. The heart and the LD were modeled as nested (series) elastance chambers, and the vasculature was represented by a two-element Windkessel model. Using five healthy goats, we verified model predictions of stroke volume for both stimulator ON beats (y = 1.00x-0.08, r = 0.87, p < 0.0001) and OFF beats (y = 1.01x+1.06, r = 0.91, p < 0.0001), where x and y are the measured and predicted stroke volumes, respectively. The model confirms that using untrained latissimus dorsi applied to the normal myocardium produces only moderate increases in stroke volume and suggests that future research should focus on increasing LD strength after training.

Cardiomyoplasty↗
PubMedDate not supplied

Bench coronary angiography: a potentially useful method to assess coronary artery disease in the older donor heart without catheterization laboratory angiography.

To assess the diagnostic accuracy of ex vivo coronary artery arteriography, 12 sheep hearts were harvested, after random multiple coronary occlusions were created. The hearts were radiographed either in the flat (n = 6) or upright suspended (n = 6) position with the aorta cross-clamped. The aortic root was cannulated with an 18-gauge needle and flushed with cold normal saline solution. Five milliliters of iodinated contrast media was injected under constant hand pressure, and angiographic views were taken with a conventional, portable x-ray machine. The aortic root was then immediately flushed with normal saline solution under constant pressure to minimize contrast contact with the vascular endothelium. Total elapsed time including film development was 7 to 10 minutes. In hearts that were radiographed lying flat, a ventriculogram was obtained because of aortic incompetence. In hearts suspended in the upright position, normal coronary anatomy and previously placed coronary occlusions were easily detected in every heart that was read blindly by angiographers. To assess the effects of the contrast media on ventricular performance, five rabbit hearts were harvested and mounted on a Langendorff apparatus for functional analysis at controlled left ventricle volumes. Diastolic and systolic left ventricular pressures were unaffected by the dye injection. This simple and rapid method to evaluate coronary anatomy of the donor heart could be potentially useful in the assessment of older donor hearts in the operating room, thus increasing the volume of donor hearts available for transplantation.

Animals↗
PubMedDate not supplied

Ischemic injury before heart transplantation does not cause coronary arteriopathy in experimental isografts.

In this study we investigated whether the duration of ischemia before heart transplantation was related to coronary arteriopathy. Heterotopic cardiac isografts were done in 24 Lewis rats. Group 1 hearts (n = 4) were transplanted immediately after harvesting. Hearts in groups 2 (n = 8), 3 (n = 6), and 4 (n = 6) were implanted after preservation at 4 degrees C for 1, 2, or 3 hours, respectively. No immunosuppressive drugs were given. After 120 days, grafts were removed and evaluated by means of light microscopy for coronary artery intimal proliferation. Minimal intimal thickening was noted throughout, and no differences among the groups were found. Pretransplant ischemia in the absence of other factors does not cause coronary arteriopathy after heart transplantation.

Abdomen↗
PubMedDate not supplied

Heart transplantation for intractable prosthetic valve endocarditis.

A 25-year-old woman with active systemic lupus erythematosus and infective endocarditis was seen initially with porcine aortic bioprosthetic stenosis, perivalvar regurgitation, and native mitral regurgitation 9 years after aortic valve replacement for lupus endocarditis. Double-valve replacement was performed with St. Jude Medical mechanical prostheses. After operation the patient developed fever and an elevated white blood cell count. One month later she had increasing mitral and aortic perivalvular regurgitation and intermittent complete heart block. At reoperation both annuli showed evidence of continued infection, and she underwent annular reconstructions with pericardium and double-valve re-replacement. Cultures grew Mycoplasma hominis. Despite long-term therapy with appropriate antibiotics, within 2 months she developed recurrent perivalvar regurgitation with congestive heart failure. Orthotopic heart transplantation was performed. The postoperative course was notable for significant leukocytosis and spontaneous culture negative hemothorax that required thoracotomy for drainage. The patient recovered and is now well 14 months after operation.

Adult↗
PubMedDate not supplied

Experimental orthotopic heart autotransplantation.

Expanding interest in heart transplantation has raised important questions about graft atherosclerosis and in pediatric patients the growth and development of the denervated heart. Models used to study graft atherosclerosis and the development of the immature transplanted heart require appropriate controls. We have developed a technique for orthotopic autotransplantation of the heart in sheep that allows preservation of the sinoatrial node and maintenance of sinus rhythm after reimplantation. The autotransplantation model is potentially useful, since graft rejection can be eliminated without immunosuppressive therapy in a large, outbred species.

Animals↗
PubMedDate not supplied

Computerized intraoperative calculation of instantaneous prosthetic aortic valve area.

Improved assessment of valve area is essential to understanding the performance of prosthetic valves. The authors studied six patients undergoing aortic valve replacement using mechanical (ME) or porcine (PO) prostheses. Instantaneous cardiac output (CO) (L/min) was measured in the aorta using an ultrasonic flow probe. Left ventricular and aortic pressures (mmHg) were measured using Millar catheters. Data were analyzed using an IBM PC-AT. Valve area (cm2) was determined using Gorlin's formula (AG) and a new formula for instantaneous area derived mathematically and using a theoretic constant. AG, mean (AI) and peak (Apk) instantaneous areas were compared to geometric measures of area (Aactual) in vitro. Peak instantaneous area correlates best with measured area. Intraoperative assessment using the ultrasonic flow probe and computer analysis is helpful in understanding the dynamic properties of prosthetic valves in vivo.

Aortic Valve↗
PubMedDate not supplied

Changing patterns in donor and recipient risk: a 10-year evolution in one heart transplant center.

BACKGROUND: Expansion of the donor pool and liberalization of recipient criteria have occurred since the introduction of cyclosporine for heart transplantation. METHODS: We sought to evaluate the impact of these changes on outcome during a 10-year period in one program. A total of 251 transplantations were retrospectively reviewed and divided into two periods (1984 to 1989 and 1990 to 1994). RESULTS: In the latter period, there were increases in donor and recipient age, degree of weight mismatch, ischemic time, bypass time, and severity of illness in the recipient before transplantation as judged by status at the time of transplantation and preoperative requirements for pharmacologic or mechanical support. Despite these changes, time to hospital discharge decreased and a trend to improved survival was seen with the use of Kaplan-Meier analysis. CONCLUSIONS: These findings suggest that improvements in perioperative and posttransplantation care have permitted a safe expansion of both the donor pool and recipient criteria for transplantation.

Adult↗
PubMedDate not supplied

Pneumococcal aortitis in the antibiotic era.

The pneumococcus remains in the antibiotic era a formidable pathogen, capable of atypical, lethal clinical presentations. We report two fatal cases of thoracic aortitis caused by Streptococcus pneumoniae in the setting of bacteremic illness from this pathogen. One case occurred in an aortic graft and the other arose in a native aorta. We also discuss the indolent clinical presentation and the diagnostic failure of transesophageal echocardiography and leukocyte scintigraphy. Persistent pyrexia with atypical chest pain and unexplained blood loss should alert clinicians to the possibility of this uncommon, yet lethal complication of pneumococcal disease.

Aged↗
PubMedDate not supplied

Thromboxane A2 mediates reperfusion injury after heart preservation.

To assess the role of the eicosanoid thromboxane A2, a potent vasoconstrictor and platelet activator, in reperfusion injury after heart preservation, donor rats (n = 18) were anesthetized, and their hearts were rapidly excised, arrested with cardioplegic solution, and fitted with a left ventricular balloon. Seven hearts were subjected to 45 minutes of ischemia at 15 degrees C, simulating implantation, (group 1) during which the carotid and jugular vessels of support rats were cannulated for ex vivo blood reperfusion. Remaining hearts were preserved in 4 degrees C saline solution for 3 hours followed by 45 minutes at 15 degrees C (group 2, n = 11). Before reperfusion of group 2 hearts, support rats received either vehicle (group 2a, n = 6) or thromboxane A2 receptor antagonist SQ29548 (0.2 mg/kg) (group 2b, n = 5). After 1 hour of reperfusion, left ventricular peak-systolic pressure and end-diastolic pressure were measured in all hearts at incremental ventricular volumes. The slope of the peak-systolic pressure-volume relation and the volume-axis intercept of the end-diastolic pressure-volume relation were also measured. No significant differences were noted in mean peak-systolic pressure, at any left ventricular volume, nor slope of the peak-systolic pressure-volume relation between groups, indicating that neither preservation nor SQ29548 treatment affected systolic contractile performance in this model. Through all left ventricular volume, however, end-diastolic pressure was significantly lower (p < 0.05) in group 2b compared to group 2a, and overall did not differ significantly from group 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Innovative techniques in skeletal muscle cardiac assistance: first experimental study on minimally invasive aortomyoplasty and cardiomyoplasty.

Skeletal muscle cardiac assistance as a treatment modality for heart failure is considered a high-risk procedure subject to strict patient selection. The aim here is to develop minimally invasive techniques to improve surgical outcomes and increase clinical indications. Ten goats (45-55 kg) were studied. In six, the latissimus dorsi muscle (LDM) was harvested via an open technique on one side vs a minimally invasive technique on the other using video assistance through two 3 cm incisions. Surgical maneuvers and length of procedures were noted. Animals were recovered, observed daily for local complications, and killed after 1 week for comparative anatomic and histopathologic studies. In four other goats, minimally invasive aortomyoplasty or cardiomyoplasty was performed using video assistance (2 aortomyoplasty, 2 cardiomyoplasty). In this experimental series, there were no surgical complications. The minimally invasive LDM harvest required a mean of 81 min (range 55-116 mn) with no gross evidence of muscle damage. The technique of LDM harvesting was standardized and is reproducible. Aortic and cardiac wraping were also achieved through three ports and a left minithoracotomy of 4 cm, using the right or left LDM. A scarf technique for the descending aortomyoplasty using the left LDM, and an anterior wrapping for cardiomyoplasty using the left or right LDM was technically feasible with video assistance. This study suggests future clinical applicability.

Animals↗