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Biomedical subjects

L H Cohn

Publications and source records attributed to L H Cohn.

At least 145 records · Page 8Linked to original sources

The long-term follow-up of the Hancock Modified Orifice porcine bioprosthetic valve.

The Hancock Modified Orifice valve is a specially fabricated, trileaflet porcine valve, which has been in clinical use at the Brigham and Women's Hospital since 1976. Three hundred seventy-nine aortic valve replacements with this device were implanted from 1976 to 1985; 305 were isolated aortic valve replacements and 74 were in association with a mitral valve bioprosthesis. The 305 patients undergoing isolated aortic valve replacement, a Food and Drug Administration patient group, are the subject of this article. The mean valve size was 22.5 mm, with 115 21-mm valves used. The mean functional preoperative class was 3.2; 99 of 305 patients (32.5%) underwent concomitant coronary artery bypass grafting. There were six operative deaths (2%). Patients were followed from 6-14 years (mean 7.4 years), and analysis was completed in early 1991. The 10-year actuarial calculation of survival freedom from reoperation, thromboembolism, structural valve degeneration, perivalvular leak, infectious valve degeneration, and total morbidity and mortality are presented.

Actuarial Analysis↗

ACC/AHA guidelines for cardiac catheterization and cardiac catheterization laboratories. American College of Cardiology/American Heart Association Ad Hoc Task Force on Cardiac Catheterization.

It is evident that the practice of cardiac catheterization has undergone, and continues to undergo, marked change. Most prominent are the recent very rapid proliferation of catheterization laboratories in general and the development of newer types of catheterization laboratory. No uniform definitions exist for these newer laboratories, so meaningful communication is difficult. The new settings are of particular concern because their location, mobility, organization, and ownership raise questions about the quality of patient care. Most difficult to address are the questions about patient safety and physician conflict of interest. There are no objective data in peer-reviewed literature to support the reported safety and cost savings of these newer settings. Through deliberations, surveys, interviews, and correspondence with the cardiology community embraced by the ACC and the AHA, the task force generally found that in freestanding catheterization laboratories, access to emergency hospitalization may be delayed, and appropriate oversight may be lacking. Additionally, opportunities for self-referral may be fostered and the perception of commercialism and entrepreneurial excess in practice created. All of these problems must be avoided. The growth and development of some freestanding facilities, particularly the mobile laboratories, do not seem to have been driven by an increased need in remote communities or for temporary support but rather almost exclusively by a desire to capture market share. Accordingly, a series of definitions, guidelines, and recommendations for the laboratories as well as for patient selection has been developed. The consensus was that a very restrictive and cautious attitude to the newer settings is appropriate at this time. The justification for development or expansion of cardiac catheterization services must be patient need. Documentation of this need must be based on objective estimates of the number of patients with known or suspected cardiac disease who meet generally accepted indications for laboratory study. Concerns about the lack of data from prospective clinical trials of patient safety in such a group necessitate a very cautious attitude toward any new catheterization services, in particular those without in-house cardiac surgical support. In view of the lack of appropriately controlled safety and need data for hospital-based, mobile, or freestanding laboratories operating without on-site (accessible by gurney) cardiac surgery facilities, the task force reaffirms the position that further development of these services cannot be endorsed at this time. In addition, there is reason for major concern that such proliferation in catheterization services may contribute to increasing costs and troubling ethical questions.

American Heart Association↗

The mechanism of heart failure caused by cardiac allograft rejection.

Rejection of the cardiac allograft is often associated with reversible myocardial failure, the mechanism of which is not understood. We have examined this phenomenon in a small animal model that provides the opportunity for multimodality study of the rejection process. Heterotopic cardiac transplantation was performed in the Lewis rat with Lewis X Brown-Norway (allografts) or Lewis (isografts) donors. Without immunosuppression, allografts are completely rejected in 6 to 8 days. At 3 days cardiac grafts were explanted and mounted on a modified Langendorff apparatus for functional measurements or submitted for pathologic examination and biochemical determination of high-energy phosphates. Three-day isografts (n = 9) had minimal histologic changes. Pathologic examination of 3-day allografts (n = 13) showed lymphocytic infiltrate and myocyte necrosis, histologic features for which antirejection treatment is usually given clinically. For grafts subjected to functional studies (n = 11), heart rate, cardiac output, coronary flow, and stroke work were determined at baseline and in response to isoproterenol (3 x 10(-8) mol/ml). Three-day allografts (n = 6) and isografts (n = 5) had similar baseline function. The chronotropic response to isoproterenol was similar in allografts and isografts, but allografts had diminished cardiac output and stroke work after isoproterenol. Adenosine triphosphate levels were normal (41.9 nmol/mg) in 3-day allografts (n = 4). We have evaluated functional, biochemical, and pathologic changes associated with myocardial dysfunction during heterotopic cardiac transplant rejection in a small animal. This model reproducibly demonstrates diminished contractile reserve in 3-day allografts with normal baseline function and high-energy stores but histologically significant rejection.

Adenosine Triphosphate↗

The dynamics of antegrade cardioplegia with simultaneous coronary sinus occlusion. Effects on aortic root infusion pressure, coronary sinus pressure, and myocardial cooling.

It has been suggested that antegrade cardioplegia with coronary sinus occlusion improves homogeneous myocardial cooling and reduces myocardial injury in the presence of coronary artery occlusion. Little data are available on the exact relationships among the basic elements or this intervention, including antegrade infusion rate, aortic root pressure, the degree of coronary sinus occlusion, coronary sinus pressure, and myocardial cooling. The purpose of this study was to determine these relationships and to provide some basic guidelines for better understanding of this intervention. Twenty-two sheep were placed on cardiopulmonary bypass, the distal left anterior descending artery was occluded, and the proximal coronary sinus was snared. Sixteen combinations of infusion rate (3, 5, 7, or 9 ml/kg/min) and coronary sinus occlusion (total, subtotal, or moderate occlusion or no occlusion) were adopted for each 2 minutes of antegrade cardioplegia, yielding 96 measurements. Myocardial temperatures in the occluded and nonoccluded regions, aortic root infusion pressure, and coronary sinus pressure were measured during each infusion of cardioplegic solution. Coronary sinus occlusion was then released, and the whole heart was reperfused for 30 minutes for another infusion of cardioplegic solution and measurements. Results showed good degrees of linearity between infusion rate and aortic root infusion pressure for all coronary sinus occlusion and noninfusion groups (p less than 0.01). A positive effect of coronary sinus occlusion on aortic root infusion pressure was observed. The graded increases in infusion rate with various degrees of coronary sinus occlusion were constantly associated with elevation of coronary sinus pressure (p less than 0.01). It was also noted that myocardial temperatures in the region of the occluded left anterior descending artery were significantly lower in coronary sinus occlusion groups than in nonocclusion groups (p less than 0.01 or 0.05). Myocardial temperature in the nonoccluded region decreased significantly with the stepwise increases in infusion rate (p less than 0.01), but not with the increases in coronary sinus occlusion (not significant). Based on this and previous studies, we recommend that the induced coronary sinus pressure be safely maintained in the range of 25 to 35 mm Hg and that further studies be focused on the infusion rate of 5 ml/kg/min with subtotal or total coronary sinus occlusion for the intervention of antegrade cardioplegia plus coronary sinus occlusion.

Animals↗

Therapy of acute aortic regurgitation.

Management considerations for dealing with a patient with acute regurgitation of the aortic valve have been emphasized. Recognition and treatment of the most usual causes of acute aortic regurgitation have been described and the emphasis placed on early surgical treatment in the appropriate patient. In particular, management strategies for acute infective endocarditis and acute aortic dissection must be done on a timely basis. Operative intervention earlier rather than later generally improves results and prevents the long-term complications of delayed operations in anatomically complex patients. Whereas accurate preoperative diagnosis and attempts in medical treatment are mandatory before embarking on surgical therapy, the best results are achieved when definitive repair is performed early in the patient's course. Failure to do so inevitably leads to complications that only worsen the ultimate outcome in terms of morbidity and mortality.

Acute Disease↗

HLA histocompatibility affects cardiac transplant rejection and may provide one basis for organ allocation.

Prospective human lymphocyte antigen (HLA) typing is not performed for heart transplantation, and the relation between HLA matching and cardiac graft rejection is unclear. Recipient and donor HLA matching were analyzed retrospectively in 51 patients undergoing orthotopic cardiac transplantation. Immunosuppression was based on cyclosporine and prednisone. During the mean follow-up of 34 months (range, 16 to 63 months), the 46 operative survivors had an average of 3.95 rejection episodes (range, zero to 11 episodes). Twenty-one patients had steroid-resistant rejection requiring treatment with polyclonal or monoclonal antithymocyte globulin. Human lymphocyte antigen typing was available for 44 patients, and antigens were grouped in broad specificities. Patients with two or more HLA-A or HLA-B matches had a reduced number of rejection episodes (3/10 versus 19/34) and a lower incidence of steroid-resistant rejection (1/10 versus 18/34; p = 0.01). Inclusion of HLA-DR matches did not alter the findings. There was a strong correlation between the increased frequency of rejection and the incidence of steroid-resistant rejection (p less than 0.0001). Four of six late deaths occurred in patients with steroid-resistant rejection; four were due to acute rejection and two to graft atherosclerosis. Although not currently done, prospective HLA matching is feasible with present typing methods. Our results suggest a rationale for prospective histocompatibility testing in cardiac transplantation with allocation of donor hearts to patients with two or more HLA matches.

Adult↗

Decreased operative risk of surgical treatment of mitral regurgitation with or without coronary artery disease.

The consecutive 2 year experience with patients undergoing first-time surgery for mitral regurgitation with and without coronary artery disease was reviewed. From January 1988 to January 1990, 127 patients with pure mitral regurgitation undergoing first-time operation were surgically treated. No other valve lesion, no reoperation and no congenital defects were included. The mean patient age was 62 years with 26% of the patients greater than 70 years. Twenty-six percent of the entire group was in functional class IV. Seventy-five patients received mitral valve repair and 52 underwent mitral valve replacement with a St. Jude or Hancock valve. In patients undergoing mitral valve repair, there was a higher incidence of those greater than 70 years old and of coronary artery disease and in patients undergoing mitral valve replacement there was a higher incidence of functional class IV. The operative mortality rate was 2.3% (3 of 127 patients). No patient failed to be discontinued from cardiopulmonary bypass and all three deaths occurred after mitral valve replacement, with one from complications of chronic renal failure and dialysis. There was no significant difference in patients who either did or did not have a concomitant coronary artery bypass graft and there was no difference related to age or functional class. Postoperative complications occurred in five patients in the valve repair group, including recurrent mitral regurgitation in two necessitating reoperation, and in three patients in the valve replacement group. With newer operative and postoperative management techniques, especially preservation of the papillary muscle annular continuity, the risk of mitral valve surgery, particularly of valve repair, is considerably lower than in previous years.

Coronary Disease↗

Reoperative cardiac surgery using a new femoral venous right atrial cannula.

A new ultra-thin but nonkinkable catheter was used for transfemoral venous right atrial drainage for cardiopulmonary bypass in 35 patients undergoing reoperations for coronary artery disease (CAD) (14), valve replacement (16), combined valve and CAD (4), and left ventricular aneurysm resection (1). Adequate flow rates were obtained with these cannula of 25, 27, and 29 French diameter in all patients. This technique provided excellent drainage of the heart allowing for a decompressed heart to dissect with no bleeding or damage to patent obstructed cardiopulmonary bypass grafts. There was no mortality over perioperative myocardial infarction postoperatively.

Cardiac Catheterization↗

The role of mechanical devices.

Devices to support the circulation and directly assist the ventricle during surgery are now both reliable and essential. The intraaortic balloon counterpulsation device is used in patients who fail to wean easily from cardiopulmonary bypass, who develop ischemia in the immediate postoperative period, or who have low output in the maximal edema phase, 4 to 8 hours postoperatively. Complications relate to the insertion of the device, which may cause major arterial disruption, lower leg ischemia, or distal arterial thromboemboli. Ventricular assist device (VAD) support is indicated when, despite the use of the intraaortic balloon, the patient's hemodynamics remain severely depressed and the patient is unable to wean from bypass. There are several contraindications to the use of VADs, including pulmonary hemorrhage. Nevertheless, as experience with the many different types of VADs increases, their use may be extended to periods of days or even months. Various mechanical support devices have been used to bridge to cardiac transplantation, with ranging degrees of success. Decisions concerning the use of mechanical devices for this purpose must take into account both the standard contraindications to transplantation, and contraindications that develop or are acquired during intervention with the bridging device. Current and future experience will decide which devices will be accepted for common clinical use.

Assisted Circulation↗

Relative risks of left ventricular aneurysmectomy in patients with akinetic scars versus true dyskinetic aneurysms.

From 1971 to 1988, 303 patients underwent left ventricular aneurysm resection. We analyzed preoperative and procedure-related variables to ascertain risk factors for surgery. A distinction was made between akinetic and dyskinetic aneurysms to assess potential relation with postoperative outcome. Indications for surgery were arrhythmia in 20 patients, congestive heart failure in 81, angina in 133, congestive heart failure and angina in 42, and other combinations in the remaining 27 patients. The left ventricular aneurysm was dyskinetic in 180 patients and akinetic in 121. Risk factors and surgical procedures were similar in both groups. Left ventricular ejection fraction was less than or equal to 30% in 98 patients. Coronary bypass grafting was performed in 269 patients, with an average of 2.3 grafts per patient. Mitral valve replacement, the most common concomitant procedure, was performed in 16 patients. Intra-aortic balloon assist was required postoperatively in 47 patients. Overall operative mortality was 13% (38 patients) and was due to low cardiac output in 23 patients and arrhythmia in 12 patients. Univariate and multivariate analyses related early mortality to New York Heart Association functional classification of heart failure, the predominant indications of arrhythmia or congestive heart failure, left ventricular ejection fraction less than or equal to 30%, the need for intra-aortic balloon support, and the excision of an akinetic (18%) rather than dyskinetic (8%) left ventricular aneurysm. Over a follow-up period averaging nearly 5 years, the actuarial survival at 5 years was 63% in the dyskinetic group and 51% in the akinetic group.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Artery Bypass↗

Neurological and ophthalmological phenomena after aortic conduit surgery.

Transient neurological and visual signs have been observed in some patients after valved conduit replacement of the aortic valve and ascending aorta. Twenty-seven patients having valved conduit replacement between February 1982 and October 1988 were compared with 21 patients having combined aortic valve replacement (AVR) and ascending aorta (AA) graft replacement. Follow-up in 100% of both groups was obtained for 0.3-6.6 years (mean, 2.6 +/- 0.3 years). Among 20 surviving valved conduit patients, 10 (50.0%) experienced repetitive neurological and visual signs, including scotomata (seven), transient motor ischemic attacks (two), amaurosis fugax (four), and recurring attention lapses suggesting petit mal seizures (one). No patient with AVR + AA graft experienced any events (p = 0.004). All valved conduit and seven (53.8%) of AVR + AA graft patients were on warfarin (p = 0.0016). These events retained the same pattern although they diminished in frequency after 12 months in seven patients (70.0%) and after initiation of dipyridamole in two patients. Rehabilitation was similar in both groups: 18 of 20 (90.0%) valved conduit and 12 of 16 (75.0%) AVR + AA graft patients (p = NS). Transient, repetitive, nonprogressive neurological and ophthalmological phenomena are frequent after valved conduit replacement. The pathophysiological mechanism is unclear, but antiplatelet therapy may provide symptomatic control.

Aorta↗

Cardioplegia for the immature myocardium. A comparative study in the neonatal rabbit.

This study examined the effect of hypothermia (15 degrees C) alone or combined with various cardioplegic solutions on functional recovery of the neonatal heart after 120 minutes of global ischemia in an isolated working rabbit heart model. Control hearts were preserved with hypothermia alone, and groups 1 to 6 were given different hyperkalemic crystalloid cardioplegic solutions. Each cardioplegic solution differed in Na+ and Ca++ content. Aortic flow, coronary flow, cardiac output, heart rate, peak systolic pressure, and stroke work were measured before ischemia and after 35 and 45 minutes of reperfusion. There were no statistical differences in hemodynamic recovery in the six groups in which cardioplegia was used. However, hearts preserved with multidose hyperkalemic cardioplegia showed significantly better recovery of cardiac output (86% versus 75%; p less than 0.05), coronary flow (88% versus 72%; p less than 0.05), and stroke work (86% versus 75%; p less than 0.05) than those preserved with hypothermia alone. These results suggest that hypothermic hyperkalemic cardioplegia improves preservation of the neonatal rabbit heart but that variations in Ca++ and Na+ content appear not to provide further myocardial protection.

Age Factors↗

Favorable results of coronary artery bypass grafting in patients older than 75 years.

There is controversy whether the short-term and long-term results of coronary artery bypass grafting in elderly patients justify performing the procedure. Between January 1977 and December 1986, 4580 patients underwent coronary artery bypass grafting, of whom 222 (4.9%) were 75 years old or older (mean 77 years). There were 143 men and 79 women and 139 (63%) were in New York Heart Association class IV. One hundred forty-six patients (66%) had had at least one preoperative myocardial infarction. Myocardial revascularization was performed under emergency conditions in 17 patients (18%). The mammary artery was used in 43%, 96% of the patients received two or more grafts. The mean number of bypass grafts was 3.1 per patient. The overall hospital mortality rate was 10.8% (24/222), 3.6% for elective procedures, 14.9% in urgent cases, and 35% in emergencies. In contrast, the overall early mortality rate was 3.1% in 4358 patients less than 75 years old. Complications occurred in 83 patients (37%). Of the patients discharged from the hospital, 198 were followed up for a mean of 48 months (1 to 130). Actuarial probability of survival was 75% at 48 months. Postoperatively 70% were in New York Heart Association class I or II and only 21% were rehospitalized for cardiac problems. During the follow-up period 77% of the patients were free from angina, and of those experiencing angina the mean time from operation to the first episode was 75 months. Although elderly patients have a somewhat increased operative mortality rate, particularly if operated on urgently or emergently, long-term survival and freedom from angina are excellent and justify continued performance of coronary bypass grafting in selected patients over 75 years of age.

Actuarial Analysis↗

Management of general surgical complications following cardiac transplantation.

Between February 1984 and May 1988, 55 patients underwent orthotopic cardiac transplantation at the Brigham and Women's Hospital, Boston, Mass. Basic immunosuppression was accomplished with steroid and cyclosporine therapies. Twelve patients suffered 14 major complications, including perforated ulcer in 3 patients; pancreatitis in 3 patients; pneumatosis coli in 2 patients; and cholecystitis, colonic necrosis, appendicitis, incarcerated umbilical hernia, pancreatic abscess, and toxic epidermal necrolysis in 1 patient each. Aggressive management of the patients included laparotomy in all but 2 patients with mild pancreatitis and the patient with toxic epidermal necrolysis, who was treated as a patient with a severe burn. In all of the patients, there was a resolution of these complications, except in one 59-year-old man with fatal hemorrhagic pancreatitis. Eleven of the 14 complications occurred during the initial hospitalization. The fatal case of pancreatitis was 1 of 5 (9%) operative mortalities in the entire series. Fifty operative survivors have been followed up for an average of 19 months, with four late deaths (8%) related to rejection. The actuarial probability of survival in patients discharged from the hospital was 90% at 12, 24, and 48 months.

Adolescent↗

Hematological complications with the St. Jude valve and reduced-dose Coumadin.

We examined hematological complications in 415 patients having valve replacement with the St. Jude mechanical prosthesis (212, aortic valve replacement [AVR]; 159, mitral valve replacement [MVR]; and 44, AVR + MVR). There were 164 men and 251 women with a mean age of 59 years (range, 20 to 88 years). Preoperatively 386 patients were in New York Heart Association functional classes III and IV. There were 154 associated procedures (37%), the most common being myocardial revascularization. Overall hospital mortality was 7.5% (31/415), 7% after AVR, 8% after MVR, and 7% after AVR + MVR. All operative survivors were anticoagulated with Coumadin (crystalline warfarin sodium) to maintain the prothrombin time at 1.5 times control. During a mean follow-up of 21 months (range, 6 to 60 months), there were 29 late deaths (7.6%) and 5 patients (1.3%) lost to follow-up. No patient experienced structural valve degeneration. At 48 months, actuarial freedom from thromboembolism was 87% +/- 3% after AVR and 91% +/- 9% after MVR; from anticoagulation-related hemorrhage, 97% +/- 3% after AVR and 91% +/- 3% after MVR; and from hemolysis, 100% after AVR and 98% +/- 2% after MVR. Freedom from all valve-related morbidity at 4 years was 82% +/- 5% after AVR and 75% +/- 10% after MVR. Actuarial survival at 48 months was 80% +/- 4% after AVR and 65% +/- 7% after MVR.

Adult↗