Biomedical subjects
Publications and source records attributed to L H Cohn.
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BACKGROUND: Surgical procedures using the latissimus dorsi (LD) muscle to assist chronic heart failure inflict major trauma on severely sick patients. A less invasive approach may prove beneficial. The aim of this article is to review our clinical and experimental approaches of dynamic aortomyoplasty (AMP) and emphasize the necessity to reorient surgical technique towards new directions and a less invasive thoracoscopic approach. MATERIALS AND METHODS: A clinical pilot study on dynamic descending AMP started in June 1995 and included four patients. Two of them could benefit from LD counterpulsation, surviving 6 months and 18 months. Following this clinical experience, we investigated, on an animal model, minimally invasive thoracoscopic surgery for this procedure. Twelve goats underwent endoscopic LD harvest and video-assisted aortic wrap, and were studied after surgical recovery from an anatomical and functional standpoint. RESULTS: Clinical AMP using open techniques provided extraaortic counterpulsation in NYHA Class IV patients contraindicated for other surgical therapies. However, surgical technique and strategy needed improvements for optimal cardiac assistance and better patient outcome. Minimally invasive thoracoscopic surgery was feasible and reproducible in goats, achieving improved anatomy and physiology as compared to the open technique in humans. When appropriate the wrapping technique and stimulation protocol were used, an optimal counterpulsation was demonstrated. We concluded that thoracoscopic AMP may provide a minimally invasive approach to cardiac assistance and thus, a new surgical option for patients presenting with chronic heart failure.
BACKGROUND: The history of surgery over the last 30 years has moved steadily toward minimally invasive surgery; more recent experience with the gall bladder, arthroscopy, and video-assisted thoracic surgery has confirmed this trend. METHODS: Our experience in minimally invasive valve surgery between July 1996 and October 1997 included 180 patients, 80 with aortic valve replacement and 100 with mitral valve replacement. The 80 aortic valve replacement patients consisted of 46 males and 34 females, with a mean age of 63 years (range 32 to 90 years) and mean New York Heart Association Functional Class 2.5. The etiology of disease was varied: degenerative in 41 patients, congenital in 17, rheumatic in 8, subacute bacterial endocarditis in 6, myxomatous in 4, and structural valve degeneration in 4. RESULTS: There were two (2.5%) operative deaths, both from multisystem organ failure. Only 16 (20%) of the 80 patients experienced new postoperative atrial fibrillation. The mean length of stay in the hospital was 5 days (range 3 to 24 days). Only 18 (23%) of the 78 surviving patients required posthospital rehabilitation, and there were no late deaths. Morbidity included cerebrovascular accident in 1 patient (1.2%), sternal infection in 1 (1.2%), groin infection in 1 (1.2%), and bleeding requiring reoperation in 1 (1.2%). CONCLUSIONS: Minimally invasive cardiac valve surgery is extremely effective and has become our current technique of choice in every mitral and aortic valve patient who does not have coronary artery disease because it reduces the length of hospital stay and cost, requires fewer blood transfusions, and stimulates less atrial fibrillation.
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BACKGROUND: Transmyocardial laser revascularization is a promising surgical technique used to treat nonreconstructable ischemic heart disease. Recent clinical data show that this technique improves the regional perfusion of ischemic myocardium and reduces angina. Presently, transmyocardial laser revascularization requires an open, lateral thoracotomy. We report here the use of thoracoscopic techniques to perform transmyocardial laser revascularization in a closed chest fashion. METHODS: Five Yorkshire farm pigs underwent left chest thoracoscopic exploration and pericardiotomy. A specialized laser handpiece then was introduced into the chest and thoracoscopic transmyocardial laser revascularization was performed (one channel per square centimeter) using an 800-W CO2 laser. RESULTS: Video analysis and gross pathology revealed that the anatomic area accessible to thoracoscopic transmyocardial laser revascularization included the entire left ventricular free wall distributions of the left anterior descending, left circumflex, and posterior descending arteries, from base to apex. Standard hematoxylin and eosin staining confirmed the creation of complete and patent 1-mm-diameter transmural channels throughout these distributions. CONCLUSION: We have shown that transmyocardial laser revascularization can be performed effectively and safely by thoracoscopy, and that this less invasive technique may reduce morbidity and provide a more cost-effective alternative therapy for nonreconstructable ischemic heart disease.
BACKGROUND: The mechanism by which cardiomyoplasty appears to enhance left ventricular (LV) function is not well understood. We applied the time-varying elastance model to study the effect of cardiomyoplasty on LV function, ventriculovascular coupling, and LV energetics in an acute canine model. METHODS: Right latissimus dorsi cardiomyoplasty was performed in 5 dogs. The end-systolic pressure-volume relation was generated by using brief caval occlusions. End-systolic elastance, effective arterial elastance, stroke work, internal work, total mechanical work, and stroke work efficiency (stroke work/total mechanical work) were calculated from these pressure-volume data. Myocardial oxygen consumption and overall mechanical efficiency (stroke work/myocardial oxygen consumption) were predicted using the myocardial oxygen consumption-total mechanical work relation. RESULTS: Skeletal muscle contraction significantly increased end-systolic elastance, an index of contractility. Although stroke work did not change significantly, the increase in end-systolic elastance led to a 29% decrease in total mechanical work, a 50% decrease in internal work, and an increase in stroke work efficiency from 53% to 66%. This was consistent with the observed 29% decrease in effective arterial elastance/end-systolic elastance, an indicator of ventriculovascular coupling that is related inversely to stroke work efficiency. Predicted myocardial oxygen consumption decreased by at least 22%, and predicted overall mechanical efficiency increased at a minimum from 16.1% to 18.4%. CONCLUSIONS: These results support the theory that cardiomyoplasty unloads the LV by decreasing LV volumes and increasing contractility. These effects appear to improve LV energetics by decreasing total mechanical work without significantly affecting stroke work, resulting in improved stroke work efficiency. The decrease in total mechanical work strongly suggests a decrease in myocardial oxygen consumption and an increase in overall mechanical efficiency.
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BACKGROUND: Peripheral arterial and venous cannulation for cardiopulmonary bypass is used increasingly for patients undergoing minimally invasive cardiac operations, complex reoperations, or repair of aortic dissection or aneurysm, and for patients with extensive arteriosclerotic aortic disease in whom aortic cannulation is a prohibitive embolic risk. The common femoral artery and vein are most commonly used for peripheral cannulation, but these sites may be predisposed to complications, primarily because the femoral vessels are commonly involved with arteriosclerotic disease. We have recently begun to use the axillary artery and axillary vein as alternative cannulation sites, achieving full cardiopulmonary bypass, providing antegrade aortic flow, and avoiding many of the complications associated with other sites. METHODS: Seven patients with peripheral vascular or aortic disease, or both, prohibiting safe aortic or femoral cannulation underwent cardiopulmonary bypass through axillary artery and axillary vein cannulation, approached through a small single subclavicular incision. RESULTS: All patients were successfully cannulated and axilloaxillary cardiopulmonary bypass was possible without the need for additional cannulas. All axillary vessels were closed primarily without complication. CONCLUSION: For an expanding population of patients with peripheral vascular and aortic disease, axilloaxillary bypass is a safe and practical alternative to aortic or femoral cannulation.
BACKGROUND: The present era of health care places major emphasis on significantly reducing cost and resource utilization while maintaining quality of care and patient satisfaction. Clinicians are being challenged to achieve this within the framework of a patient subset that is increasing in severity of disease and risk-adjusted mortality. The Brigham and Women's Cardiac Surgical Services Management Group was formed in 1987 to help accomplish these goals. METHODS: The principles we have followed involve protocols and people. The multidisciplinary group includes the chiefs of cardiac surgery and anesthesia, chief residents, physician assistants, perfusionists, intensive care unit nursing personnel, and case managers. Weekly meetings address every aspect of problems arising in the cardiac surgical service; separate weekly morbidity and mortality conferences are held. The Care Coordination Team establishes and monitors clinical pathways and recommends ways of improving all aspects of the service through a process of daily review on an individual patient basis. RESULTS: The volume of cardiac surgery at Brigham and Women's Hospital has increased steadily. The length of stay overall has decreased about 15%, and similarly, cost and total charges have also decreased. In addition, patient satisfaction has increased to a level of about 95%. CONCLUSIONS: The goals of cost-containment with improved patient care and outcome are possible through the collaborative efforts of representatives of all the personnel involved in cardiac care, as well as leadership by the surgical faculty.
BACKGROUND: Transmyocardial laser revascularization was used as the sole therapy for patients with ischemic heart disease not amenable to percutaneous transluminal coronary angioplasty or coronary artery bypass grafting. This technique uses a carbon dioxide laser to create transmyocardial channels for direct perfusion of the ischemic heart. METHODS: Since 1992, 200 patients, at eight hospitals in the United States, have undergone transmyocardial laser revascularization. The patients have a combined 1560 months of follow-up for an average of 10 +/- 3 months per patient. Their age was 63 +/- 10 years and their ejection fraction was 47% +/- 12%. Eighty-two percent had at least one previous bypass graft operation and 38% had a prior angioplasty. Preoperatively, the patients underwent nuclear single photon emission computed tomography perfusion scans to identify the extent and severity of their ischemia. These scans were repeated at 3, 6, and 12 months. Angina class, admissions for angina, and medications were recorded. RESULTS: The perioperative mortality was 9%. Angina class decreased significantly from before treatment to 3, 6, and 12 months (p < 0.001). Likewise, there was a significant decrease in the number of perfusion defects in the treated left ventricular free wall. Concomitantly, there was a significant decrease in the number of admissions for angina in the year after the procedure when compared with the year before treatment (2.5 vs 0.5 admissions per patient-year). CONCLUSION: These combined results indicate that transmyocardial laser revascularization provides angina relief, decreases hospital admissions, and improves perfusion in patients with severe coronary artery disease.
OBJECTIVE: This study compares the quality of valve replacement and repair performed through minimally invasive incisions as compared to the standard operation for aortic and mitral valve replacement. SUMMARY BACKGROUND DATA: With the advent of minimally invasive laparoscopic approaches to orthopedic surgery, urology, general surgery, and thoracic surgery, it now is apparent that standard cardiac valve operations can be performed through very small incisions with similar approaches. METHODS: Eighty-four patients underwent minimally invasive aortic (n = 41) and minimally invasive mitral valve repair and replacement (n = 43) between July 1996 and April 1997. Demographics, procedures, operative techniques, and postoperative morbidity and mortality were calculated, and a subset of the first 50 patients was compared to a 50-patient cohort who underwent the same operation through a conventional median sternotomy. Demographics, postoperative morbidity and mortality, patient satisfaction, and charges were compared. RESULTS: Of the 84 patients, there were 2 operative mortalities both in class IV aortic patients from multisystem organ failure. There was no operative mortality in the patients undergoing mitral valve replacement or repair. The operations were carried out with the same accuracy and attention to detail as with the conventional operation. There was minimal postoperative bleeding, cerebral vascular accidents, or other major morbidity. Groin cannulation complications primarily were related to atherosclerotic femoral arteries. A comparison of the minimally invasive to the conventional group, although operative time and ischemia time was higher in minimally invasive group, the requirement for erythrocytes was significantly less, patient satisfaction was significantly greater, and charges were approximately 20% less than those in the conventional group. CONCLUSIONS: Minimally invasive aortic and mitral valve surgery in patients without coronary disease can be done safely and accurately through small incisions. Patient satisfaction is up, return to normality is higher, and requirement for postrehabilitation services is less. In addition, the charges are approximately 20% less. These results serve as a paradigm for the future in terms of valve surgery in the managed care environment.
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Aortic valve replacement has proven reliable, relieves life-threatening symptoms, and improves long-term survival of patients with aortic stenosis and aortic regurgitation. Minimally invasive aortic valve replacement uses small incisions; reduces exposure of the patient to surgical trauma, blood utilization, and operative dissection; although still using cardiopulmonary bypass and achieving the same general quality as with the open operation. Early and medium term results for minimally invasive aortic valve replacement approaches show a reduction in pain, improved patient satisfaction, and improved mobility and return to full-time activity. Concomitantly, there should be decreased cost and a decreased reliance on post-hospital rehabilitation.
BACKGROUND: To investigate the theory of decreased myocardial oxygen consumption (MVo2) in dynamic cardiomyoplasty (DCM), previous studies have calculated indices of MVo2 in DCM. These previous studies, however, used left ventricular pressure in formulas that assumed the assumed the heart to be in its native state, with the reference pressure at the epicardium assumed to be atmospheric. In DCM, however, the reference pressure at the epicardium is no longer atmospheric but rather is the compressive pressure generated by the latissimus dorsi (LD). We therefore used the transmural myocardial pressure, Pt, to calculate indices of MVo2 in DCM. METHODS AND RESULTS: A half-ellipsoidal, fluid-filled balloon was interposed between the LD and myocardium in a balloon-mediated cardiomyoplasty procedure in five goats. With commonly used LD stimulation parameters, Pt was calculated as left ventricular pressure minus balloon luminal pressure. Using Pt, the transmural tension time index (TtTI) and transmural pressure volume area (PtVA) were calculated. In another series of four goats, LD stimulation parameters were optimized and the TtTI and PtVA recalculated. With standard LD stimulation parameters, the TtTI decreased by 48%, from 15.8 to 8.2 mm Hg.s, and the PtVA by 21%, from 775 to 612 mm Hg.mL, as the LD was stimulated to contract. When the optimized parameters were used, the TtTI decreased by 45%, from 11.2 to 6.2 mm Hg.s, and the PtVA by 33%, from 1984 to 1371 mm Hg.mL. CONCLUSIONS: Our results suggest that DCM with a fluid-filled balloon decreases MVo2 as the LD contracts and that LD stimulation parameters have a determining effect on this benefit.
BACKGROUND: Atrial fibrillation (AF) after coronary artery bypass surgery (CABG) is the most common sustained arrhythmia. Its pathophysiology is unclear, and its prevention and management remain suboptimal. The aim of this prospective study was to determine the current incidence of AF, identify its clinical predictors, and examine its impact on resource utilization. METHODS AND RESULTS: Over a 12-month period ending July 31, 1994, a CABG procedure was performed on 570 consecutive patients (age range, 32 to 87 years; median age, 67 years; 232 [41%] were > or = 70 years; 175 [31%] were women; 173 [30%] were diabetics; 364 [65%] required nonelective surgery; 86 [15%] had had a prior CABG; and 86 [15%] had had prior percutaneous transluminal coronary angioplasty). AF occurred in 189 patients (33%). The median age for patients with AF was 71 years compared with 66 for patients without (P = .0001). Multivariate logistic regression analysis (odds ratio, +/- 95% CI, P value) was used to identify the following independent predictors of postoperative AF: increasing age (age 70 to 80 years [OR = 2; CI, 1.3 to 3; P = .002], age > 80 years [OR = 3; CI, 1.6 to 5.8; P = .0007]), male gender (OR = 1.7; CI, 1.1 to 2.7; P = .01), hypertension (OR = 1.6; CI, 1.0 to 2.3; P = .03), need for an intraoperative intraaortic balloon pump (OR = 3.5; CI, 1.2 to 10.9; P = .03), postoperative pneumonia (OR = 3.9; CI, 1.3 to 11.5; P = .01), ventilation for > 24 hours (OR = 2; CI, 1.3 to 3.2; P = .003), and return to the intensive care unit (OR = 3.2; CI, 1.1 to 8.8; P = .03). The mean length of hospital stay after surgery was 15.3 +/- 28.6 days for patients with AF compared with 9.3 +/- 19.6 days for patients without AF (P = .001). The adjusted length of hospital stay attributable to AF was 4.9 days, corresponding to > or = $10 055 in hospital charges. CONCLUSIONS: AF remains the most common complication after CABG and consequently is a drain on hospital resources. Concerted efforts to reduce the incidence of AF and the associated increased length of stay would result in substantial cost saving and decrease patient morbidity.