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Biomedical subjects

N T Kouchoukos

Publications and source records attributed to N T Kouchoukos.

At least 37 records · Page 2Linked to original sources
PubMed1998

Profound hypothermia for spinal cord protection in operations on the descending thoracic and thoracoabdominal aorta.

Elective hypothermic cardiopulmonary bypass with or without circulatory arrest has been used successfully for the treatment of complex aneurysms of the descending thoracic and thoracoabdominal aorta. Hypothermia has a protective effect on spinal cord function, and its use has been associated with a low incidence of paraplegia in traditionally high-risk patients. In our series, 96 consecutive patients underwent resection and graft replacement of diseased aortic segments of the distal aortic arch, the descending thoracic aorta, or the thoracoabdominal aorta. Thirty-day mortality was 7.3%, and the incidence of spinal cord ischemic injury was 3.4%. Our experience with hypothermic cardiopulmonary bypass and circulatory arrest confirms the safety and efficacy of the technique for operations on the descending thoracic and thoracoabdominal aorta.

Aortic Aneurysm, Abdominal↗
PubMed1998

Surgical management of the severely atherosclerotic ascending aorta during cardiac operations.

Severe atherosclerosis of the ascending aorta is associated with an increased incidence of stroke after cardiac surgery. Direct intraoperative epiaortic scanning is a rapid and accurate means for detection of ascending aortic atherosclerosis. When severe atheromatous disease is detected, graft replacement of the ascending aorta is our preferred method of management. During an 11-year period, 81 patients (mean age 71 years) who underwent coronary artery bypass were found to have severe ascending aortic atherosclerosis by epiaortic scanning. Using hypothermic circulatory arrest, 80 patients underwent partial (5) or complete (75) ascending aortic replacement. One patient underwent resection of a protruding aortic atheroma. In addition to partial or total replacement of the ascending aorta, 34 patients had replacement of the aortic arch, 19 had a valve replacement, and 6 had carotid endarterectomy. The 30-day mortality was 8.6% (7 patients). Four patients (4.9%) sustained perioperative strokes and 2 (2.5%) sustained transient perioperative ischemic neurological deficits. The 3-year survival rate was 40%. There was one stroke 4 months postoperatively that eventually led to late death. Elective resection and graft replacement of the severely atherosclerotic ascending aorta using hypothermic circulatory arrest in patients undergoing cardiac operations is a safe procedure, associated with an acceptable incidence of postoperative stroke. The procedure may provide long-term protection from subsequent embolic cerebral vascular events. However, long-term survival has been disappointing and is primarily related to generalized atherosclerosis.

Aged↗
PubMed1997

Myocardial infarction and cardiac mortality in the Bypass Angioplasty Revascularization Investigation (BARI) randomized trial.

BACKGROUND: Cardiac mortality and myocardial infarction (MI) rates are used to evaluate the efficacy of coronary artery bypass grafting (CABG) and percutaneous transluminal coronary angioplasty (PTCA). We compared 5-year cardiac mortality and MI rates in 1829 patients with multivessel disease randomized to CABG or PTCA. METHODS AND RESULTS: The 5-year cardiac mortality rate was 8.0% in patients assigned to PTCA compared with 4.9% in those assigned to CABG (relative risk [RR] of 1.55 with a 95% confidence interval [CI] of 1.07 to 2.23; P=.022). In a subgroup of 1476 nondiabetic patients, there were no significant differences between treatment groups in cardiac mortality either overall (4.6% versus 4.2%; RR= 1.04, 95% CI, 0.65 to 1.66; P=.908) or in subgroups based on symptoms, left ventricular function, number of diseased vessels, or stenotic proximal left anterior descending artery. The two treatment groups had similar event rates for the combined end point of cardiac death or MI. The RR for cardiac mortality in 264 patients who sustained an MI compared with those who did not was 5.9 (P<.001). MIs were more common after CABG during index hospitalization (P=.004), but in the PTCA group, they were more common after discharge (P<.001). CONCLUSIONS: The Bypass Angioplasty Revascularization Investigation (BARI) trial indicates 5-year cardiac mortality in patients with multivessel disease was significantly greater after initial treatment with PTCA than with CABG. The difference was manifest in diabetic patients on drug therapy. There were no significant differences overall for the composite end point of cardiac mortality or MI between treatment groups or for cardiac mortality in nondiabetic patients regardless of symptoms, left ventricular function, number of diseased vessels, or stenotic proximal left anterior descending artery.

Angioplasty, Balloon, Coronary↗
PubMed1997

Neuronal apoptosis and necrosis following spinal cord ischemia in the rat.

We examined the characteristics of neuronal death induced by ischemia in the spinal cord. Spinal cord ischemia was induced in Long-Evans rats by occlusion of the descending aorta with a 2F Fogarty catheter for 20 min (model 1) or more limited aortic occlusion (15 min) coupled with blood volume reduction (model 2); rats were sacrificed 6 h-7 days later. The animals developed variable paraparesis in model 1 and reliable paraplegia in model 2. The extent of histopathological spinal cord damage, being maximal in the lumbar cord, correlated well with the severity of paraparesis. Two distinct types of spinal cord neuronal death were observed, consistent with necrosis and apoptosis. Neuronal necrosis was seen in gray matter laminae 3-7, characterized by the rapid (6 h) onset of eosinophilia on hematoxylin/eosin-stained sections, and gradual (1-7 days) development of eosinophilic ghosting. Although TUNEL positivity was present, disintegration of membranes and cytoplasmic organelles was seen under electron microscopy. Neuronal apoptosis was seen after 1-2 days in dorsal horn laminae 1-3, characterized by both TUNEL positivity and electron microscopic appearance of nuclear chromatin aggregation and the formation of apoptotic bodies. DNA extracted from the ischemic lumbar cord showed internucleosomal fragmentation (laddering) on gel electrophoresis. These data suggest that distinct spinal cord neuronal populations may undergo necrosis and apoptosis following transient ischemic insults.

Animals↗
PubMed1997

Reoperations on the aortic root and ascending aorta.

BACKGROUND: Reoperations on the aortic root and the ascending aorta are being performed with increasing frequency and remain a challenging problem. METHODS: Eighty-one patients (age range, 14 to 78 years) underwent reoperations on the aortic root or the ascending aorta during a 14.5-year interval ending October 1996. The previous operations were aortic valve procedure (28%), coronary artery bypass grafting (25%), aortic root replacement (24%), ascending aortic replacement (19%), and miscellaneous (5%). Twenty-two patients (27%) had had two or more previous operations. The principal indications for reoperation were true or false aneurysm (35%), acute or chronic dissection (28%), and malfunction of an aortic valve substitute (27%). The reoperations performed were aortic root replacement (composite graft, allograft, or autograft) in 48 patients and graft replacement of the ascending aorta in 33 patients. Concomitant procedures included aortic arch replacement in 43 patients (55%) and coronary artery bypass grafting in 33 patients (41%). RESULTS: The 30-day mortality rate was 8.6% (7 patients). It was 8.3% for aortic root replacement and 9.1% for ascending aorta replacement (p > 0.05). Using stepwise multivariate logistic regression analysis of 23 variables, preoperative functional class III/IV (p = 0.047) and duration of cardiopulmonary bypass (p = 0.007) were significant independent predictors of early death. The mean duration of follow-up was 3.6 years. The 1-year, 5-year, and 10-year survival rates were 89%, 81%, and 69%, respectively. Freedom from reoperation on the heart or ascending aorta was 98%, 92%, and 69%, respectively. Reoperation for false aneurysm (p = 0.050) and the presence of coexisting coronary artery disease requiring bypass grafting (p = 0.010) were the only significant predictors of late mortality. CONCLUSIONS: Reoperations on the aortic root and the ascending aorta can be accomplished with acceptable early mortality and satisfactory long-term results. More frequent resection of the aneurysmal or dissected segments of the ascending aorta and aortic root at the initial operation may reduce the need for subsequent reoperation.

Actuarial Analysis↗
PubMed1997

Neuronal cell death in the ischemic spinal cord: the effect of methylprednisolone.

BACKGROUND: Cell death occurs by either necrosis or apoptosis. The role of apoptosis in the neuronal degeneration after ischemia remains to be defined. We studied (1) the nature of neuronal death and (2) the neuroprotective action of methylprednisolone in a rat model of spinal cord ischemia. METHODS: Spinal cord ischemia was induced in adult Long-Evans rats by occluding the aortic arch for 14 minutes and simultaneously equilibrating the femoral artery pressure to the atmospheric pressure. Twenty rats were subjected to ischemia without treatment and another twenty to ischemia after treatment with methylprednisolone (30 mg/kg, 4 hours before ischemia). The animals were sacrificed and the lumbar spinal cords were examined on postoperative days 1 and 2. RESULTS: On day 1, neurons with morphology indicative of apoptosis were present in the gray matter. Their numbers increased from the ventral to the dorsal location. There were significantly fewer apoptotic neurons in the dorsal horn of the methylprednisolone-treated animals. DNA obtained from the spinal cord of untreated rats on days 1 and 2 showed laddering after electrophoresis, a feature of apoptosis. Pretreatment with methylprednisolone inhibited the development of DNA laddering. Methylprednisolone treatment was not associated with significantly improved neurologic function in the postoperative period. CONCLUSIONS: Apoptotic neuronal death occurs in the rat spinal cord after transient ischemia and is attenuated by pretreatment with methylprednisolone.

Animals↗
PubMed1997

Protection of rat spinal cord from ischemia with dextrorphan and cycloheximide: effects on necrosis and apoptosis.

OBJECTIVE: We examined the characteristics of neuronal cell death after transient spinal cord ischemia in the rat and the effects of an N-methyl-D-aspartate antagonist, dextrorphan, and a protein synthesis inhibitor, cycloheximide. METHODS: Spinal cord ischemia was induced for 15 minutes in Long-Evans rats with use of a 2F Fogarty catheter, which was passed through the left carotid artery and occluded the descending aorta, combined with a blood volume reduction distal to the occlusion. The rats were killed after 1, 2, and 7 days. Other groups of rats were pretreated with dextrorphan (30 mg/kg, intraperitoneally, n = 7), cycloheximide (30 mg, intrathecally, n = 7), or vehicle (saline solution, n = 12) and killed after 2 days. RESULTS: This model reliably produced paraplegia and histopathologically distinct morphologic changes consistent with necrosis or apoptosis by light and electron microscopic criteria in different neuronal populations in the lumbar cord. Scattered necrotic neurons were seen in the intermediate gray matter (laminae 3 to 7) after 1, 2, and 7 days, whereas apoptotic neurons were seen in the dorsal horn laminae 1 to 3 after 1 and 2 days. Deoxyribonucleic acid extracted from lumbar cord showed internucleosomal fragmentation (laddering) on gel electrophoresis indicative of apoptosis. The severity of paraplegia in the rats treated with dextrorphan and cycloheximide was attenuated 1 day and 2 days after ischemia. The numbers of both necrotic and apoptotic neurons were markedly reduced in both dextrorphan- and cycloheximide-treated rats. CONCLUSIONS: The results suggest that both N-methyl-D-aspartate receptor-mediated excitotoxicity and apoptosis contribute to spinal cord neuronal death after ischemia and that pharmacologic treatments directed at blocking both of these processes may have therapeutic utility in reducing spinal cord ischemic injury.

Animals↗
PubMed1997

Cell death suggestive of apoptosis after spinal cord ischemia in rabbits.

BACKGROUND AND PURPOSE: After spinal cord ischemia, some neurons remain viable after an ischemic insult but may be at risk of dying during reperfusion. We searched for morphological and biochemical features of apoptosis, which is a mechanism of delayed neuronal death, in a rabbit model of spinal cord ischemia. METHODS: The infrarenal aorta of White New Zealand rabbits (n = 24) was occluded for 40 minutes using a loop tourniquet. Rabbits were killed after 12, 24, or 48 hours (n = 8 per group). The loop was placed but never tightened in sham-operated rabbits (n = 6). The lumbar segment of the spinal cord (L5 to L7) was used for morphological studies, including hematoxylin and eosin staining and a modified terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining method. Electron microscopy was used to examine ultrastructural morphology. In addition, lumbar tissue was used for biochemical investigation of DNA laddering by agarose gel electrophoresis. RESULTS: After ischemia, the affected areas contained neurons with positive TUNEL staining. Positive neurons were located in laminae III to IX, although most were concentrated in the intermediate and ventral areas. Adjacent sections stained with hematoxylin and eosin exhibited ischemic cell changes (red and ghost neurons), while apoptotic bodies were also apparent. In addition, electron microscopy of ischemic tissue samples exhibited ultrastructural characteristics of apoptosis, including nuclear condensation and relatively normal organelle morphology. Finally, isolated DNA revealed a ladder on agarose gel electrophoresis, indicating DNA fragmentation into approximately 180 multiples of base pairs. CONCLUSIONS: Spinal cord ischemia in rabbits induces morphological and biochemical changes suggestive of apoptosis. These data raise the possibility that apoptosis contributes to neuronal cell death after spinal cord ischemia.

Animals↗
PubMed1997

Spinal cord ischemic injury. Development of a new model in the rat.

BACKGROUND AND PURPOSE: Spinal cord ischemic injury (SCII) with resulting paralysis is a major cause of morbidity after operations on the thoracic aorta. Since the vascular supply to the spinal cord is similar in rats and humans, the rat appears important for studies of mechanisms of injury and development of therapeutic strategies to avoid this complication. METHODS: In group A rats, we induced SCII using a previously described method, by occluding the descending thoracic aorta for 15, 20, 24, or 30 minutes with the inflated balloon of a 2F Fogarty catheter inserted through the femoral artery. In group B, the catheter was inserted through the left common carotid artery, and the aorta was occluded just distal to the carotid origin for 20 minutes. In group C, in addition to the procedure described for group B, hypovolemia was induced during a 12-minute period of aortic occlusion by equilibrating the left femoral artery pressure to the atmospheric pressure. The motor function of the hind limbs and the associated spinal cord histopathology were studied. RESULTS: At 96 hours, 9 of 10 rats in group C were paraplegic. This rate was significantly higher than that of group A (1 of 21, P = .00000) or group B (4 of 10, P < .03). In all groups, the histopathological changes became more severe from the rostral to the caudal direction along the spinal cord and from the peripheral to the central location in transverse sections. CONCLUSIONS: The combination of aortic arch occlusion with induced hypovolemia resulted in a reproducible model of SCII in rats.

Animals↗
PubMed1996

Volume requirements for cardiac surgery credentialing: a critical examination. The Ad Hoc Committee on Cardiac Surgery Credentialing of The Society of Thoracic Surgeons.

New volume requirements for coronary artery bypass grafting are being imposed on cardiac surgeons by hospitals, managed care groups, and others. The rationale for this is unclear. The available literature as well as additional sources relating volume and outcomes in cardiac surgery were extensively reviewed and reexamined. There are no data to conclusively indicate that outcomes of cardiac operations are related to a specific minimum number of cases performed annually by a cardiac surgeon. Each cardiothoracic surgeon should participate in a national database that permits comparison of his or her outcomes on a risk-adjusted basis with other surgeons. Until conclusive data become available that link volume to outcome, volume should not be used as a criterion for credentialing of cardiac surgeons by hospitals, managed care groups, or others. Instead, each surgeon should be evaluated on his or her individual results.

Cardiac Surgical Procedures↗
PubMed1996

Intraoperative transesophageal echocardiography and epiaortic ultrasound for assessment of atherosclerosis of the thoracic aorta.

OBJECTIVES: This study sought to determine the role of transesophageal echocardiography (TEE) and epiaortic ultrasound in the detection of atherosclerosis of the ascending aorta in patients undergoing cardiac surgery. BACKGROUND: Atherosclerosis of the ascending aorta is a major risk factor for perioperative stroke and systemic embolism in patients undergoing cardiac surgery. METHODS: Forty-four patients underwent prospective evaluation of the ascending aorta with two ultrasound techniques-epiaortic ultrasound and biplane TEE-and by palpation. The severity of atherosclerosis was graded on a four-point scale as normal, mild, moderate or severe. RESULTS: A comparison of results with biplane TEE and those with epiaortic ultrasound yielded a kappa value of 0.12 (95% confidence interval 0 to 0.25), indicating poor correlation between the two. Compared with epiaortic ultrasound, biplane TEE significantly underestimated the severity of ascending aortic atherosclerosis, and this underestimation was more marked in the distal ascending aorta (p < 0.0001). When compared with epiaortic ultrasound and biplane TEE, palpation of the ascending aorta significantly underestimated the presence and severity of atherosclerosis (p < 0.0001 for both). CONCLUSIONS: Epiaortic ultrasound is more accurate than TEE for identification of atherosclerosis of the ascending aorta, but both ultrasound techniques are superior to palpation. Epiaortic ultrasound and TEE provide complementary information regarding thoracic aortic atherosclerosis. Modification of surgical technique on the basis of results of intraoperative epiaortic ultrasound and TEE in elderly patients undergoing cardiac procedures may prevent atheroembolic complications.

Aged↗
PubMed1996

Functional outcome in the elderly after coronary artery surgery.

Patients 80 years of age and older who underwent coronary artery bypass grafting (CABG) were surveyed to determine their postoperative status. Basic activities of daily living were performed by 93%, and 62% of those surveyed reported health satisfaction. CABG can be performed in the elderly population with good functional outcome and an improved quality of life.

Activities of Daily Living↗
PubMed1996

Unusual accelerated progression of saccular aneurysms in an ectatic right coronary artery.

Localized aneurysmal dilation or ectasia of coronary arteries is a relatively uncommon angiographic finding, of which the pathophysiological mechanism remains speculative. The majority of patients diagnosed with this clinical entity usually present with angina pectoris. Furthermore, it is rare to find isolated ectasia or aneurysm dilation of the coronary arteries in patients with no prior history of coronary artery disease. The natural course is usually slowly progressive. This case demonstrates an unusual accelerated dilation of coronary saccular aneurysms, within a year of diagnosis, in a patient who presented with new onset congestive heart failure. Although the diagnosis was made with coronary angiography, both magnetic resonance imaging and transesophageal echocardiography were of critical diagnostic value to identify the size and extension of the aneurysms as well as the presence of intraluminal thrombi.

Aged↗
PubMed1995

Sensitive detection of abnormal aortic architecture in Marfan syndrome with high-frequency ultrasonic tissue characterization.

BACKGROUND: Aneurysmal dilation of the aorta with subsequent rupture or dissection occurs frequently in patients with Marfan syndrome and is the primary cause of morbidity. These complications are related to the altered composition and disorganized structure of the aortic media. Our goal was to use high-frequency ultrasonic tissue characterization to identify these structural changes in abnormal aorta from patients with Marfan syndrome. We measured integrated backscatter and anisotropy of backscatter of ultrasound from specimens of aorta from patients with Marfan syndrome undergoing aortic root replacement and compared these values with those from aortic specimens of patients without clinical aortic pathology. METHODS AND RESULTS: Aortic tissue was obtained at the time of surgery from 11 patients with Marfan syndrome undergoing repair of an aortic aneurysm or dissection. Normal tissue was obtained at the time of autopsy from 8 patients without evidence of aortic disease. Acoustic microscopy at 50 MHz was performed to measure integrated backscatter from each specimen. The magnitude of ultrasonic anisotropy of backscatter for each tissue type was determined as an index of the three-dimensional (3D) organization of the vessel matrix. The collagen content of each specimen was determined with a hydroxyproline assay. Marfan aortas exhibited less backscatter than did normal aortas (-40.9 +/- 2.9 versus -32.6 +/- 2.2 dB for patients with Marfan syndrome and healthy subjects, respectively, P < .0001). No significant difference in collagen concentrations was observed between normal and Marfan aorta (262.7 +/- 52.7 versus 282.4 +/- 41.8 mg/g tissue for normal and Marfan aortas, respectively, P = .42), despite the large difference in backscatter. Histological analysis revealed striking differences in both the amount and organization of the elastin in the aortic aneurysm segments from patients with Marfan syndrome compared with normal aorta. Normal aorta was characterized by well-formed elastin fibers arranged in a lamellar pattern. The media from aneurysms in Marfan aorta exhibited a profound decrease in elastin content that was associated with loss of the highly aligned and ordered lamellar arrangement. The directional dependence of scattering, or ultrasonic anisotropy, also differed dramatically between the two tissue types. Backscatter from normal aorta decreased substantially when the media was insonified parallel compared with perpendicular to the principal axis of the elastin fibers. Marfan aorta exhibited a much smaller directional dependence of scattering. Normal aortas manifested a 14-fold greater ultrasonic anisotropy than did Marfan aortas (24.1 +/- 3.7 versus 12.4 +/- 3.3 dB for normal and Marfan aortas, P < .0001), which is indicative of the profound extent of matrix disorganization in Marfan syndrome. CONCLUSIONS: These data show that high-frequency ultrasonic tissue characterization sensitively detects changes in vessel wall composition and organization that occur in the aorta of patients with Marfan syndrome. Aortic segments from these patients manifested a significant decrease in integrated backscatter compared with normal aorta (approximately 8 dB, or greater than a 6-fold decrease in scattering). A 15-fold reduction in the ultrasonic anisotropy of Marfan tissue was observed, which suggests a marked disorganization of the 3D architecture of these aortas. These data support the hypothesis that high-frequency ultrasonic tissue characterization may be useful for identifying abnormalities of vessel wall composition, architecture, and material properties.

Adult↗
PubMed1995

Life expectancy in the Marfan syndrome.

Data reported in 1972 indicated that lifespan in patients with the Marfan syndrome is markedly shortened, and that most deaths are cardiovascular. This study was performed to determine whether survival in the Marfan syndrome has changed since 1972, and to discern whether treatment (medical or surgical) has altered prognosis. Survival curves were generated on 417 patients from 4 referral centers, with a definite diagnosis of the Marfan syndrome. Birth date, age at death, cardiovascular surgery, or treatment with beta blockers, or any combination of these, were included in the analysis. Forty-seven of 417 patients died. Mean age at death (41 +/- 18 years) was significantly increased compared with age in 1972 (32 +/- 16 years, p = 0.0023). Median (50%) cumulative probability of survival in 1993 was 72 years compared with 48 years in 1972. Of 112 surgically treated patients, 10-year probability of survival was 70%. Patients undergoing surgery after 1980 enjoyed significantly increased survival than patients who had undergone operation before 1980 (p = 0.008). In conclusion, life expectancy for patients with the Marfan syndrome has increased > 25% since 1972. Reasons for this dramatic increase may include (1) an overall improvement in population life expectancy, (2) benefits arising from cardiovascular surgery, and (3) greater proportion of milder cases due to increased frequency of diagnosis. Medical therapy (including beta blockers) was also associated with an increase in probable survival.

Adult↗
PubMed1995

Pulmonary artery aneurysm: review and case report.

Aneurysms involving the main pulmonary artery and its branches are rare. Clinical experience is limited and current knowledge is mainly derived from autopsy findings. This case report describes a patient with a pulmonary artery aneurysm associated with a previous, partially corrected stenotic pulmonary valve. The patient presented with symptoms suggestive of aneurysm dissection three decades after commissurotomy. The diagnostic approach and therapeutic intervention are emphasized with a review of the literature.

Aneurysm↗