Search PubMed⌕ Search

Biomedical subjects

L H Cohn

Publications and source records attributed to L H Cohn.

At least 91 records · Page 5Linked to original sources
PubMed1995

Repair of mitral regurgitation from myxomatous degeneration in the patient with a severely calcified posterior annulus.

Severe posterior annular calcification poses a particular challenge to mitral valve repair. In a series of 252 mitral valve repairs for myxomatous degeneration performed between 1980 and 1993, 14 patients had a severely calcified posterior mitral valve annulus. Ages ranged from 61 to 81 years. Twelve patients were preoperative NYHA Class III or IV, and five patients required concurrent coronary artery bypass procedures. Operative techniques included complete resection of the calcified posterior annulus, resections of portions of the posterior leaflet with leaflet advancement, and placement of an annuloplasty ring. There were no operative deaths and all patients had a postoperative echocardiographic confirmation of relief from mitral regurgitation. During a mean follow-up time of 36 months (6 months to 8 years), there has been one late valve reoperation and only one late death, from thromboembolism in a patient with atrial fibrillation. These data indicate that even in the presence of severe calcification of the posterior mitral annulus, mitral valve repair for myxomatous degeneration can be performed with a low-operative risk and satisfactory long-term results.

Aged↗
PubMed1995

The effect of the single aortic cross-clamp technique on cardiac and cerebral complications during coronary bypass surgery.

Cardiac and cerebral events during coronary artery bypass graft (CABG) surgery remain a major cause of morbidity and mortality. Efforts made to reduce these events will have a significant impact on CABG results. The objective of this study was to examine our results in 394 patients undergoing primary CABG using the single clamp technique that probably has better myocardial and cerebral protective properties than the conventional technique of partial aortic occlusion. Age range was 35 to 88, mean of 66 years, and 168 (43%) were > or = 70 years of age; 121 (31%) were females, 118 (30%) were diabetic, 339 (82%) were in New York Heart Association Functional Class III or IV, 77 (20%) had a preoperative intra-aortic balloon pump, 213 (54%) were nonelective, 293 (75%) had three vessel disease, and 55 (14%) had critical left main coronary artery stenosis. Antegrade crystalloid cardioplegia was used in the majority of patients, and the distal and proximal anastomoses were sequentially constructed during a single period of total aortic occlusion. The mean number of grafts was 3.5, and 339 (86%) had > or = 3 grafts; at least one internal mammary artery was used in 346 (88%), a sequential vein or mammary artery in 181 (46%), and 55 (14%) had at least one coronary endarterectomy. The mean cross-clamp time, bypass time, and time to wean off bypass were 63, 83, and 20 minutes, respectively. The overall operative mortality was 11 of 394 (2.8%), a myocardial infarction/low-cardiac output state occurred in 19 (4.8%), and a stroke in 3 (0.8%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Comparing today's revascularization strategies for CAD. Benefits and drawbacks of thrombolytics, PTCA, CABG.

A number of factors must be considered when selecting a revascularization strategy for a patient with CAD: Is the patient's condition stable or unstable? How many vessels are affected? What are the benefits and drawbacks of each technique? For patients with an evolving infarction, either thrombolysis or PTCA can achieve early reperfusion. PTCA is also often helpful for those with one- or two-vessel disease; however, restenosis develops in 30% to 50% of patients, usually within 6 months. Although CABG can produce excellent long-term results for patients with three-vessel or left main artery disease and for those with proximal stenosis, the risk of perioperative complications and bypass graft disease remains significant.

Angioplasty, Balloon, Coronary↗
PubMed1995

Choosing a revascularization strategy for your patient with CAD. Consider both the clinical presentation and the urgency of the situation.

For patients with less severe coronary artery disease, particularly one- or two-vessel disease, initial therapy may be with either thrombolytics or angioplasty. In those with more extensive disease (three-vessel or left main artery disease or proximal left anterior descending artery stenosis), bypass grafting can significantly reduce mortality. However, a patient's risk profile markedly influences outcome regardless of the procedure performed. Because angioplasty achieves incomplete revascularization, patients may need repeated angiography or revascularization, or they may have recurrent angina. If bypass graft disease is prevented, surgery may be effective for up to 20 years.

Angioplasty, Balloon, Coronary↗
PubMed1995

A modified collection and rapid infusion system for shed whole blood autotransfusion during aortic aneurysm surgery.

We describe our experience in 10 patients (5 males) undergoing resection of a descending thoracic aortic aneurysm or a thoracoabdominal aortic aneurysm in which a modified shed whole blood collection and autotransfusion system was used. This modification allows several options for the processing and autotransfusion of shed blood: use of the cell saving device or the ultrafiltration of collected blood, and the autotransfusion of unprocessed shed whole blood. Either low dose heparin or sodium citrate was used for anticoagulation. All 10 patients underwent autotransfusion and volume resuscitation with the modified rapid infusion device. Total autotransfusion ranged from 1400 ml to 7843 ml. Ultrafiltration volumes ranged from 600 ml to 1100 ml. There were no intraoperative deaths and no patient reoperations for bleeding. Arterial blood gases, potassium, and platelet counts were all within the normal laboratory ranges. This modification enables the clinician to process poor quality shed blood and reinfuse whole blood, in an attempt to decrease the need for homologous blood products.

Aged↗
PubMed1994

Aortic dissection: new aspects of diagnosis and treatment.

Involvement of the ascending aorta constitutes a surgical emergency, making rapid diagnosis essential. Noninvasive imaging, once no better than aortic angiography, has been bolstered by the advent of transesophageal echocardiography. It can be performed at the bedside, its accuracy approaches 100%, and the patient can be on the way to the operating room within 10 minutes.

Adrenergic beta-Antagonists↗
PubMed1994

Single-clamp technique: an important adjunct to myocardial and cerebral protection in coronary operations.

To determine the myocardial and cerebral protective properties of the single cross-clamp (group I; n = 160) versus the partial occluding clamp (group II; n = 150) technique for construction of the proximal anastomoses, a retrospective analysis of 310 patients operated on by the same surgeon was performed. Group I patients were older (median age, 70 versus 64 years; p < or = 0.0001), with 83 (52%), versus 41 (27%) in group II, 70 years and older (p < or = 0.0001). More group I patients were in New York Heart Association functional class IV (42 [26%] versus 22 [15%]; p = 0.008); more required preoperative balloon counterpulsation (35 [22%] versus 16 [11%]; p = 0.006); and more required emergent operation (20 [13%] versus 3 [2%]; p < or = 0.0001). Antegrade crystalloid cardioplegia was used in both groups. The median cross-clamp time was 58 minutes for group I versus 44 minutes for group II (p < or = 0.0001). However, there was no significant difference between the two groups in terms of the number of bypass grafts, the use of the mammary artery, or the bypass time. The operative mortality was 2.5% (n = 4) for group I versus 5.3% (n = 8) for group II (p = 0.16), and the perioperative myocardial infarction/low cardiac output state was seen in 6 patients (3.8%) in group I versus 18 patients (12%) in group II (p = 0.006). The median creatine kinase MB release was 13 U/L for group I versus 19 U/L for group II (p = 0.0029).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Pituitary apoplexy following cardiopulmonary bypass: considerations for a staged cardiac and neurosurgical procedure.

Pituitary apoplexy in a pre-existing pituitary tumor can result in serious and permanent neurologic deficits following cardiac surgical procedures. Several factors related to the altered physiology of cardiopulmonary bypass (CPB) contribute separately or in combination to the development of this syndrome. Over the last year we have encountered two such cases in whom emergency and prompt decompression of the adenoma resulted in an improvement of the initial clinical presentation but nevertheless persistence of residual and devastating ocular manifestations. In the literature six similar cases have been reported following cardiac surgical procedures, with similar outcomes. In this report we describe our experience and management of these two patients, and that published in the literature. We propose a possible role for a staged cardiac and neurosurgical procedure as a prophylactic measure in patients with known pituitary tumor. The role of cerebral monitoring is also discussed.

Adenoma↗
PubMed1994

An external aortic root device for decreasing aortic regurgitation: in vitro and in vivo animal studies.

OBJECTIVES: The purpose of this study was to determine if a device placed externally around the aortic root decreases regurgitant flow in acute aortic regurgitation. BACKGROUND: Aortic regurgitant flow is dependent on central aortic pressure and the aortic root and leaflet geometry. It may be possible to decrease aortic regurgitant severity by reducing aortic root size or dimension changes. METHODS: Aortic regurgitation was created in eight calf heart specimens suspended in a continuous flow system. Retrograde and antegrade aortic flow and distending aortic pressure were measured at baseline and after placement of an external aortic device at the level of the aortic annulus. In two additional specimens, the incompetent aortic valve was visualized fiberoptically before and after placement of the external device. Acute aortic regurgitation was created surgically in four live calves by excising a portion of the aortic leaflets. Antegrade and retrograde flow, left ventricular pressure, and central aortic pressure were measured at baseline, after creation of aortic regurgitation, and after placement of the external device. RESULTS: In the in vitro calf specimens, regurgitant flow decreased from 46.9 cc/sec to 15.1 cc/sec (66.0% +/- 21.8% decrease) after placement of the external device (p < 0.001). The regurgitant orifice area decreased from 0.13 +/- 0.04 cm2 to 0.04 +/- 0.02 cm2 after device placement (p < 0.001). Antegrade flow was reduced to a smaller extent (20.0% +/- 19.2% decrease) by the device (p < 0.05). Placement of the device around the aorta resulted in improved coaptation of the leaflets with a marked reduction in defect size by endoscopic visualization. Use of the external aortic device was associated with improvement in aortic regurgitant severity in three of four calves with surgically created aortic regurgitation. CONCLUSIONS: In these preliminary studies, acute experimental aortic regurgitant severity is decreased by the use of an external aortic device, probably due to reduction in aortic annular dimension changes and improved aortic leaflet apposition. Further studies are needed to determine the effectiveness of this device in chronic aortic regurgitation.

Animals↗
PubMed1994

Tricuspid regurgitation secondary to mitral valve disease: when and how to repair.

The etiology of tricuspid regurgitation (TR) in North American patients with mitral valve disease is almost entirely nonrheumatic functional dilatation of the tricuspid annulus. In mild TR, no operative therapy is necessary since relief of the left sided valve lesion will suffice to bring the pulmonary pressure down and, consequently, relief of TR for moderate (2+ to 3+) TR. We have used a technique of posterior annuloplasty using a DeVega type double running braided suture beginning at the commissure of the anterior and posterior leaflets and running to the commissure between the septal and posterior leaflets, and tied over an obturator. The technique takes less than 10 minutes. Seventy-one patients in the past 10 years have been treated with this technique with virtually 100% relief of TR. For severe TR, we advocate the use of Carpentier-Edwards annuloplasty ring with interrupted sutures (16 patients). We believe severe TR requires a fixed annulus for virtually the entire circumference of the valve. Functionally regurgitant tricuspid valves should be reconstructed and not replaced. The use of repair techniques for moderate (posterior annuloplasty) or severe (Carpenter-Edwards tricuspid annuloplasty ring) TR will be satisfactory for virtually all patients with this lesion.

Cardiac Output↗
PubMed1994

Right latissimus dorsi cardiomyoplasty improves left ventricular function by increasing peak systolic elastance (Emax).

BACKGROUND: Dynamic cardiomyoplasty remains a promising but poorly understood surgical modality for selected patients with dilated cardiomyopathy. Despite encouraging clinical results, objective evidence of enhanced ventricular function using traditional indexes (cardiac output, ejection fraction, and dP/dt) has been difficult to document after cardiomyoplasty. Several investigators have suggested that cardiomyoplasty acts partly by unloading the left ventricle. These indexes all depend somewhat on loading conditions, however, and might not detect such an interaction. The time-varying elastance model provides an index of contractility, Emax, that is relatively insensitive to changes in loading conditions. We applied this model to study the effect of right latissimus dorsi cardiomyoplasty on left ventricular function in an acute canine model. METHODS AND RESULTS: Five dogs underwent acute cardiomyoplasty using untrained right latissimus dorsi muscle. Instrumentation included Millar pressure transducers in the left ventricle and aortic root, an electromagnetic flow probe around the ascending aorta, and a volume conductance catheter in the left ventricle. A cuffed nerve electrode around the thoracodorsal nerve and a right ventricular sensing lead were connected to a Medtronic Cardiomyostimulator (5 V, 30 Hz, 1:1 synchronization). Transient caval occlusions were performed with the stimulator both off and on to calculate Emax and the slope of the end-systolic pressure-volume relationship (Ees). Turning the stimulator on significantly increased peak systolic elastance (Emax) and end-systolic elastance (Ees) in all five dogs by an average of 56% and 78%, respectively (P < .05). End-diastolic volume and end-systolic volume decreased by 18% and 28%, respectively (P < .05). All other measured hemodynamic parameters, including peak left ventricular pressure, mean arterial pressure, cardiac output, stroke volume, stroke work, ejection fraction, preload-recruitable stroke work, and dP/dt, did not change significantly. CONCLUSIONS: These results show that, in this acute canine model, right latissimus dorsi cardiomyoplasty significantly improves left ventricular function while decreasing left ventricular volumes. The results are consistent with the theory that cardiomyoplasty increases contractility while unloading the ventricle by decreasing end-diastolic volume. This increase in Emax despite inconsistent changes in other indexes underlies the importance of using load-insensitive indexes of ventricular function when studying cardiomyoplasty.

Animals↗
PubMed1994

'No touch' dissection, antegrade-retrograde blood cardioplegia, and single aortic cross-clamp significantly reduce operative mortality of reoperative CABG.

BACKGROUND: We assessed the improvement in total and cardiac-related operative mortality in 131 consecutive patients after reoperative coronary artery bypass surgery (CABG). METHODS AND RESULTS: The patients were divided into two consecutive groups, A (1988 to 1989) and B (1990 to 1993), on the basis of the implementation of alternative techniques of myocardial protection. The techniques in group B included the "no touch" technique or minimal dissection before bypass, routine femoral artery and vein exposure, and frequent cannulation for cardiopulmonary bypass and antegrade and retrograde blood cardioplegia, with all vascular anastomoses (proximal and distal) performed with a single aortic cross-clamp and cardioplegic arrest. Cardiac mortality from low cardiac output or myocardial infarction was 15% versus 0%, P = .002. Multivariate analysis of demographics, perioperative risk factors, and myocardial protection techniques revealed that only membership in group A and the requirement for an intra-aortic balloon counterpulsation independently predicted mortality. By univariate analysis, group A had significantly more patients with three-vessel disease and patients who required urgent or emergent procedures, but analysis of patients in these subgroups also demonstrates a significant reduction in mortality in the "no touch" patients (group B). Although no technique was independently responsible for reduced operative mortality, all the myocardial protection techniques implemented in group B combined to reduce the risk of reoperative CABG. CONCLUSIONS: With appropriate myocardial protection techniques, the risk of reoperative CABG should be similar to that for a primary procedure.

Constriction↗
PubMed1994

Aortic valve endocarditis. Determinants of early survival and late morbidity.

BACKGROUND: Aortic valve surgery for endocarditis remains a high-risk procedure. The objective of this study was to analyze the interaction between the various subsets of endocarditis (native, prosthetic, healed, and active), timing of surgery, and their influence on early and late outcomes. METHODS AND RESULTS: During a 20-year period starting January 1972, 200 patients underwent aortic valve replacement for infective endocarditis (age range, 13 to 88 years; median, 53 years). There were 51 (26%) females, and 109 (55%) were in New York Heart Association functional class IV before surgery. Native valve endocarditis (NVE) and prosthetic valve endocarditis (PVE) were present in 132 (66%) and 68 (34%) patients, respectively. Surgery was required in 120 (60%) during the active phase (AE) and 80 (40%) during the healed phase (HE) of endocarditis. The main indication for surgery in the healed group was progressive congestive heart failure. The indications for the active group were congestive heart failure (68%), continuing active sepsis (70%), echocardiographic vegetation (28%), peripheral emboli (30%), and arrhythmias (13%). Streptococcal infections predominated in NVE, staphylococcal in PVE and AE; culture-negative endocarditis predominated in the healed group. Isolated aortic valve surgery was performed in 68% of the patients, and concomitant procedures (32%) included mitral valve and coronary bypass procedures. The overall operative mortality (OM) was 12.5%. The OM was 7.5% and 22% for NVE and PVE, respectively (P = .004), and 7% for HE versus 15% for AE (P = .06). The OM for early PVE was 33% versus 18% for late PVE (P < .05). Multivariate logistic regression analysis identified PVE and New York Heart Association functional class IV to be independent predictors for early death. Recurrent endocarditis occurred 26 times in 24 patients (11 early, 13 late), with three operative deaths in the early group, all due to residual staphylococcal infections. Freedom from recurrent endocarditis was significantly different between HE (96 +/- 3% and 86 +/- 6% at 5 and 10 years, respectively) and AE (89 +/- 3% and 83 +/- 4%, respectively (P = .02). Long-term survival for discharged patients was 81 +/- 3% and 63 +/- 5% at 5 and 10 years, respectively, with no significant difference between NVE, PVE, AE, and HE. CONCLUSIONS: These data suggest that for active endocarditis, surgery should be delayed to achieve a healed status provided there is no pressing need for immediate surgery. Patients with staphylococcal endocarditis, particularly on a prosthesis, should be operated on sooner and should be covered with antibiotics for an extended period to prevent recurrent PVE. This study stresses the need for aggressive antibiotic prophylaxis, particularly in the presence of a prosthesis.

Aortic Valve↗
PubMed1994

Rapid noninvasive diagnosis and surgical repair of acute ascending aortic dissection. Improved survival with less angiography.

Angiography has been considered the gold standard for the diagnosis of acute dissection of the ascending aorta, but it may increase mortality by imposing an unnecessary delay before surgical repair. In addition, coronary angiography has often been considered essential as well. From 1988 to 1993, 37 patients (median age 61 years, 30 men and 7 women) had acute dissection of the ascending aorta. All of the initial 15 patients (group I) had angiography, even through the diagnosis of aortic dissection had already been made noninvasively in 14; six (40%) of 15 died, three of aortic rupture and none of complications of coronary artery disease. Among the next 22 patients (group II), 21 had a noninvasive diagnosis of acute dissection of the ascending aorta (eight by echocardiography; 13 by computed tomography), and 19 (86%) were operated on without angiography; two died (9%, p = 0.03 versus group I) and neither death was due to aortic rupture or coronary artery disease. Overall, either root or selective coronary angiography was attempted in 18 of 37 patients, but it documented coronary artery disease in only two patients (11%). Coronary artery disease was found in four other patents at autopsy; three of them, including two that died of aortic rupture, had angiography that failed to reveal the coronary artery disease. Noninvasive diagnosis of acute dissection of the ascending aorta is reliable and avoids the risks and delays inherent in invasive angiography. Rapid noninvasive diagnosis of aortic dissection and avoidance of routine angiography appear to improve survival by expediting surgical intervention and thus decreasing the risk of aortic rupture.

Acute Disease↗
PubMed1994

Prevention of complement-induced pulmonary hypertension and improvement of right ventricular function by selective thromboxane receptor antagonism.

The effect of complement activation on the pulmonary vascular system and on right ventricular function was studied in sheep (n = 12) by injection of cobra venom factor. Animals were instrumented for measurement of pulmonary flow, mean pulmonary artery pressure, right ventricular stroke work, arterial blood gases, and systemic vascular resistance. Blood was sampled from the left atrium and pulmonary artery to measure thromboxane B2, the metabolite of thromboxane A2, by radioimmunoassay. After baseline measurements, animals were randomly assigned to receive a selective thromboxane receptor antagonist SQ30741 as a 10 mg/kg bolus with an infusion of 10 mg/kg per hour or else to receive vehicle. Cobra venom factor was then injected (30 U/kg) in all animals, and data were recorded at 15, 30, 60, 90, and 120 minutes. In control animals there was a 2.4-fold increase in mean pulmonary artery pressure and a 76% increase in right ventricular stroke work at 15 minutes from baseline (p < 0.05); these values remained elevated for 30 minutes and returned to baseline by 1 hour with no change in systemic vascular resistance. Arterial oxygenation decreased by 124% at 15 minutes and remained depressed through the experiment, but in treated animals oxygen tension remained unchanged from baseline. Thromboxane B2 increased 95% from baseline in the control group and 1.5 fold in treated animals and followed a similar time course as the functional measurements (p < 0.05). A pulmonary vascular thromboxane B2 gradient of approximately 1000 pg/ml was measured at 15 and 30 minutes in both control and treated groups. (p < 0.05) We conclude that after complement activation in this model pulmonary hypertension and decreased oxygen tension are mediated by thromboxane release from the pulmonary vascular bed. This increased afterload causes a stress on the right ventricle as demonstrated by the increased right ventricular stroke work. Selective thromboxane receptor antagonism may be a beneficial therapy for pulmonary hypertension in patients after cardiopulmonary bypass.

Animals↗
PubMed1994

The long-term results of mitral valve reconstruction for the "floppy" valve.

The myxomatous degenerated, prolapsed, or floppy mitral valve is the most common etiology of mitral regurgitation in North American populations. We performed mitral valve reconstruction for this diagnosis in 252 patients from 1984 to 1993. There were 165 males and 87 females ranging in age from 23 to 84 years (mean 64 years); 93 (37%) were > or = 70 years. One hundred eighty-six were New York Heart Association Functional Class III or IV and 29% (72) underwent concomitant coronary bypass operation. Operations included posterior leaflet resection, anterior leaflet resection treatment of chordal pathology by shortening or Gore-Tex replacement, and ring annuloplasty. There were five operative deaths for an operative mortality of 2%. The operative risk in patients under 70 years was 1 of 159 (0.6%) and 4 of 93 (4%) in patients older than 70 years. Ninety percent of patients are asymptomatic in a follow-up period extending 10 years, while structural valve degeneration requiring reoperation at 5 years was 85%. From 1990 to 1993 there has been a less than 5% absolute incidence of structural valve degeneration. Mitral valve reconstruction for complicated floppy mitral valve is feasible and offers excellent early and medium-term results.

Adult↗