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Biomedical subjects

O E Dapunt

Publications and source records attributed to O E Dapunt.

At least 19 recordsLinked to original sources
PubMed2001

Coronary endothelial injury after local occlusion on the human beating heart.

BACKGROUND: Occlusion of coronary arteries during beating heart surgery bears the potential for mechanical trauma to the arterial wall with consequent endothelial injury. The aim of this study was to elucidate the effects of local occlusion on the beating heart in human coronary arteries. METHODS: Coronary arteries of patients with dilated cardiomyopathy (n = 7) or ischemic heart disease (n = 10) undergoing heart transplantation were locally occluded after starting cardiopulmonary bypass. Immediately after excision of the diseased heart, the vessels were fixed. Unoccluded segments served as controls. Integrity of endothelial lining was observed with scanning electron microscopy. RESULTS: Scanning electron microscopy revealed significantly more severe endothelial injury in the area of occlusion than in the adjacent, not manipulated control segments. In the region of local occlusion, plaque rupture was noted in three of 34 atherosclerotic vessel specimens, injury to side branches was evident in two of 44, and local microthrombus formation was evident in six of 44 samples. CONCLUSIONS: Local occlusion of human coronary arteries during beating heart coronary surgery may cause focal endothelial denudation, local microthrombosis, atherosclerotic plaque rupture, and injury to target vessel side branches.

Anastomosis, Surgical↗
PubMed1999

Intracoronary shunt insertion prevents myocardial stunning in a juvenile porcine MIDCAB model absent of coronary artery disease.

OBJECTIVE: The relevance of regional LV myocardial ischemia/reperfusion induced by temporary left anterior descending (LAD) coronary artery occlusion during minimally invasive direct coronary artery bypass (MIDCAB) grafting is controversial. The purpose of our study was (1) to determine the impact of conventional LAD occlusion during left internal thoracic artery (LITA)-LAD anastomosis on regional LV myocardial ischemia and function, and (2) to evaluate if intra-LAD shunt insertion during LITA-LAD anastomosis prevents potential regional LV ischemia and dysfunction in a pig model. METHODS: In 20 anesthetized, mechanically ventilated pigs we performed LITA-LAD anastomosis on the beating heart without cardiopulmonary bypass during either 15 min LAD occlusion (occlusion-group; n = 10) or 15 min intra-LAD shunt insertion to maintain blood supply to the myocardium beyond the anastomosis (shunt-group; n = 10). Besides standard hemodynamics we determined the global and regional LV wall motion score index (WMSI) using epimyocardial echocardiography. To quantitate structural myocardial alteration we determined the inducible heat-shock protein-70 (HSP-70) in LV anterior wall myocardial biopsies. Data were recorded at baseline, at 15 min of LAD occlusion or shunt insertion, respectively, and at 30 min of reperfusion. At the end of the experiments we determined myocardial adenine nucleotide (ATP, ADP, AMP) and glycogen content. RESULTS: In both groups WMSI was not significantly different at 15 min LAD occlusion or shunt insertion, respectively, as compared to baseline. However, at 30 min reperfusion both global and regional WMSI demonstrated significant LV dysfunction in the occlusion-group, whereas LV function in the shunt-group remained normal. This was associated with higher myocardial HSP-70 expression in the occlusion-group (P < 0.05). Myocardial adenine nucleotide and glycogen contents were significantly better preserved in the shunt-group. CONCLUSIONS: Our data show that in a porcine MIDCAB model 15 min LAD occlusion and 30 min reperfusion result in significant myocardial stunning. In contrast, maintenance of LAD perfusion using intracoronary shunt insertion minimizes ischemia/reperfusion injury and prevents regional LV dysfunction. Although our experiments were conducted in healthy pig hearts absent from coronary artery disease, similar results may--at least partially--be expected in humans, and thus, intracoronary shunts could be a useful tool for myocardial protection during 'off-pump revascularization'.

Adenine Nucleotides↗
PubMed1999

Simultaneous carotid and coronary artery surgery: indications and perioperative outcome.

BACKGROUND: A significant number of patients with coronary artery disease is diagnosed with additional carotid artery disease. This subset of patients has been identified as a high-risk group for cardiac and cerebral complications following surgical intervention. METHODS: In a retrospective analysis we investigated the perioperative outcome of combined single-stage carotid endarterectomy (CEA) and coronary artery bypass grafting (CABG) in 63 patients operated between January 1989 and August 1998. In all of these patients, CEA was performed prior to CABG and before initiation of cardiopulmonary bypass. RESULTS: Perioperative mortality rate was 7.9% (5/63) for simultaneous CEA and CABG and was due to cardiac complications in all patients. Postoperative unilateral neurological symptoms were diagnosed in 1 patient (1.7%) and were completely reversible. No neurologic events suggestive for permanent cerebral damage were observed during the 30 d postoperative period. CONCLUSIONS: In our study combined single-stage CEA and CABG was associated with low cerebral morbidity and patient outcome was mainly determined by cardiac complications. In this subset of patients, simultaneous CEA and CABG appears to be a safe method.

Carotid Stenosis↗
PubMed1998

Atrial natriuretic peptide-induced release of cyclic guanosine monophosphate by coronary bypass grafts.

BACKGROUND: Superior long-term patency rates of the internal mammary artery (IMA) versus saphenous vein (SV) after coronary artery bypass grafting are well documented. Higher production rates of vasodilating and platelet-inhibiting mediators (prostacyclin and nitric oxide) by the IMA seem to have a major impact on its long-term durability and resistance to coronary artery graft disease. For the right gastroepiploic artery (RGEA) marked release of protective mediators is reported as well. The vasodilating effect of cyclic guanosine monophosphate (cGMP) released after stimulation by atrial natriuretic peptide might serve as another graft protective system. The aim of the present study was to determine cGMP release by IMA, RGEA, and SV after atrial natriuretic peptide challenge. METHODS: Samples of human IMA (n = 19), RGEA (n = 7), and SV (n = 18) discarded during coronary artery bypass grafting were stimulated with 10(-6) mol/L atrial natriuretic peptide after a resting phase in nutrient medium. Release of cGMP was determined by 125-iodide radioimmunoassay. RESULTS: Basal cGMP production rates of the IMA (759.9 +/- 277.0 fmol/cm2) and RGEA (739.9 +/- 186.0 fmol/cm2) were higher than production rates of SV (281.2 +/- 64.0 fmol/cm2). Application of atrial natriuretic peptide led to a statistically significant increase of cGMP release in IMA grafts (1,939.3 +/- 778.0 fmol/cm2), whereas RGEA (618.4 +/- 141.3 fmol/cm2) and SV (221.7 +/- 64.5 fmol/cm2) remained at basal levels (p < 0.05). CONCLUSIONS: From these data we conclude that the IMA in comparison with the RGEA and SV produces more extracellular cGMP when stimulated by atrial natriuretic peptide. This effect might support the cGMP-mediated protective properties of nitric oxide and could underline the extraordinary suitability of the IMA as a bypass conduit.

Abdominal Muscles↗
PubMed1998

Stimulated prostacyclin release by conduits used for coronary artery bypass grafting.

A direct comparison of the three coronary artery bypass conduits internal mammary artery (IMA), right gastroepiploic artery (RGEA), and saphenous vein (SV) concerning arachidonic acid (AA) stimulated release of the vasodilating and platelet inhibiting mediator prostacyclin was the aim of the present study. Pieces of saphenous vein (n = 16), right gastroepiploic artery (n = 8), and internal mammary artery (n = 19) were obtained from patients undergoing coronary artery bypass grafting. After a resting phase of 30 min in HEPES medium arachidonic acid (AA) was added in order to stimulate prostacyclin release. Time-dependent production of the stable prostacyclin metabolite 6-keto-prostaglandin F1 alpha was determined following stimulation. Under basal conditions the IMA (12.4 ng/cm2) and RGEA (12.0 ng/cm2) released more prostacyclin than saphenous vein (4.0 ng/cm2). After AA stimulation 6-keto-prostaglandin F1 alpha release at 30 min was as follows: IMA 806.0 ng/cm2, RGEA 35.9 ng/cm2, SV 82.3 ng/cm2 (p < 0.0001 within grafts, p < 0.0001 between grafts, ANOVA for repeated measures). The internal mammary artery in comparison with the right gastroepiploic artery and saphenous vein seems to be better protected against local thrombotic events and development of coronary artery graft disease with the aid of the vasodilating and platelet inhibiting mediator prostacyclin.

Arachidonic Acid↗
PubMed1997

Intramural right atrial myocardial hemangioma treated by emergency surgery.

An unusual case of myocardial cavernous hemangioma causing dissection of the right atrial wall is described. A subsequent intramural hematoma presented as an extensive pseudotumor of the heart and was complicated by hematopericardium and tamponade. Tumor resection could be performed successfully. Diagnostic approach, surgical treatment and histopathological findings are presented.

Aortic Dissection↗
PubMed1996

Spinal cord protection in descending and thoracoabdominal aortic surgery--the role of distal perfusion.

The use of distal perfusion in descending thoracic and thoracoabdominal aortic surgery remains a controversial issue. Few mainly retrospective studies which directly compare simple clamping with distal perfusion are available. The aim of the present study was such a comparison in an own series of descending and thoracoabdominal aortic replacement. The records of 29 patients who underwent descending or thoracoabdominal aortic replacement between 1988 and 1994 were retrospectively reviewed. Patients were divided into two groups. Group I consisted of 14 patients who received aortic replacement using simple clamping, group II was represented by 15 patients who were operated with distal perfusion techniques. In group II left heart bypass with a centrifugal pump was used in 3 patients, and partial cardiopulmonary bypass with a roller pump in 12 patients. The paraplegia/paraparesis rate was 28.6% in group I and 0.0% in group II (p = 0.0258). There were no statistically significant differences regarding surgical revision for bleeding (14.3% in group I, 14.0% in group II), postoperative renal failure (14.3% in group I 13.3% in group II), postoperative ventilator dependence (9.0 days in group I, 11.2 days in group II), rate of postoperative multisystem organ failure (26.7% in group I, 33.3% in group II), length of stay in the ICU (13.6 days in group I and 13.9 days in group II), and 30-day mortality (21.4% in group I and 33.3% in group II). Methods of distal perfusion in comparison to simple clamping can lead to a lower paraplegia/paraparesis rate in descending and thoracoabdominal aortic surgery.

Adult↗
PubMed1996

[A new cardiac pacemaker stimulation technology (autocapture) allows, with unchanged life expectancy, reduction of generator size by half].

Energy delivery (stimulation amplitude) of a pacemaker should be adjusted to the depolarisation threshold of the heart, which is a nonconstant magnitude. As programming of the stimulation amplitude is time-consuming, many pacemakers are never adjusted to the measured threshold referring to energy delivery. The unnecessary energy loss subsequently reduces the longevity of the implanted devices and remains the weak point of modern pacemakers. Autocapture function (automatic stimulation threshold search, subsequently automatic amplitude regulation 0.3 V above measured threshold, evoked response detection to verify the efficacy of every stimulus and back up pulse in case of loss of capture) is for the first time realized in an extremely small, rate adaptive, multiprogrammable single chamber pacemaker (Microny SR+ 2425T). The pulse generator was tested in a multicentric, european clinical investigation study. These pacemakers were implanted in 8 patients (5 male, 3 female) between December 1994 and April 1995. Automatic measurement of Autocapture threshold revealed 0.7 +/- 0.15 V at implantation, 1.5 +/- 0.3 V after 1 month, 1.3 +/- 0.14 V after 6 months and 1.3 +/- 0.14 V 1 year after implantation. A safety margin of 0.3 V is added to the threshold value to secure capture, therefore mean stimulation amplitude is 1.6 V after 12 months implantation time. The Autocapture feature minimizes current drain and that means that this extremely small generator provides a comparable life as the twice as large common generators used at present time.

Aged↗
PubMed1995

Quantitative electroencephalography: a method to assess cerebral injury after hypothermic circulatory arrest.

Although hypothermic circulatory arrest and low-flow cardiopulmonary bypass are routinely used for surgical correction of congenital cardiac anomalies, use of long durations of arrest, often required for more complex repairs, raises serious concerns about cerebral safety. Searching for an intraoperative assessment that can reliably predict cerebral injury, we have found an excellent correlation between changes in quantitative electroencephalography intraoperatively and immediately postoperatively after prolonged hypothermic arrest, and neurologic and behavioral evidence of cerebral injury. After epidural placement of four recording electroencephalographic electrodes and baseline neurologic/behavioral and electroencephalographic assessment, 32 puppies were randomly assigned to one of four groups: hypothermic controls in which cooling to 18 degrees C was followed immediately by rewarming, 30 minutes of hypothermic circulatory arrest at 18 degrees C, 90 minutes of arrest at 18 degrees C, and 90 minutes of low-flow cardiopulmonary bypass at 25 ml/kg per minute at 18 degrees C. An electroencephalogram was recorded at baseline, after cooling, during rewarming, and at 2, 4, and 8 hours after the start of rewarming, as well as before the operation and 1 week after the operation. Postoperative neurologic and behavioral outcome was assessed 24 hours after cardiopulmonary bypass and daily for 1 week by means of a graded scale in which 0 is normal and 12 and 13 indicate severe neurologic injury (coma and death). Thirty animals survived the experimental protocol: two animals in the 90-minute hypothermic arrest group died before neurologic evaluation could be completed, and the remainder exhibited various degrees of neurologic and behavioral impairment, more severe on day 1 than on day 6. No animal in the remaining groups had a significant neurologic deficit. Quantitative electroencephalographic analysis shows marked differences between the 90-minute arrest group and the controls in the percent electroencephalographic silence during rewarming and at 2 hours, and in the percent recovery of baseline power at 2, 4, and 8 hours. At 2 hours after the start of rewarming, a correlation between electroencephalographic amplitude and neurologic/behavioral score on day 1 was carried out, which predicts with great certainty (p < 0.00001) that if electroencephalographic power at this time is less than 500 microV2, overt neurologic injury will subsequently become apparent. In addition, a significant shift from higher to lower frequency in the day 6 postoperative electroencephalogram compared with baseline occurs only in the 90-minute arrest group.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

[Bioprosthesis degeneration and reoperation in the aortic and mitral position].

In agreement with our experiences from our first study 15 patients (8 men, 7 women) underwent reoperation because of degeneration of bioprosthetic valves implanted in aortic or mitral position during the last 24 months. At reoperation 4 patients had a more complex cardiac procedure (double valve replacement, double valve replacement with bypass grafting, valve replacement with enlargement of the valvular area). There was no acute operation and only 1 patient was serious symptomatic preoperatively (NYHA IV). We revealed a mean implantation time of 126.4 months +/- 32.2 (median 130) for all bioprostheses without a significant difference in implant time regarding to aortic or mitral position. At reoperation bypass time (p = 0.001) and aortic clamp time (p = 0.011) was significantly longer compared to the first operation. There was no perioperative death, all patients are still alive and in good condition (8 of them NYHA I, 7 NYHA II). The early change of tissue degenerated bioprostheses can be carried out under elective conditions with improved postoperative outcome: mortality and morbidity remains acceptable low. In our group incremental risk factors for early mortality are severely affected patients with low functional status (NYHA IV) and acute operation. Preoperative coronary angiography remains essential for evaluation of concomitant coronary artery disease.

Adult↗
PubMed1994

[Successful resuscitation in severe hypothermia following near-drowning].

A six-year-old boy fell into an ice-cold mountain stream and was immediately washed away. He was rescued 65 min later, 6 1/2 km downstream, seemingly lifeless with a rectal temperature of 16.4 degrees C. He was flown by helicopter to the surgical clinic of Innsbruck University, while resuscitation measures were undertaken by an accompanying doctor. After cannulation of the femoral artery and vein, extracorporeal circulation (ECC) with a child-size oxygenator was started and the blood rewarmed over 96 min in steps of 3 degrees C. Once circulatory stability and adequate cardiac output had been achieved ECC was gradually discontinued while the patient was still slightly hypothermic. Ten months after the accident the boy is restored to health, except for minimal residual neurological signs. There is a high chance for full neurological recovery.

Brain Damage, Chronic↗
PubMed1994

Cerebral effects of low-flow cardiopulmonary bypass and hypothermic circulatory arrest.

Although both hypothermic circulatory arrest (HCA) and low-flow cardiopulmonary bypass (CPB) are accepted techniques for the operative management of complex cardiovascular pathology, the potential for neurologic sequelae is still a concern. To assess the relative safety of these techniques, we compared cerebral hemodynamics and clinical outcome in two groups of puppies. Sixteen puppies underwent 45 minutes of either HCA or low-flow CPB (25 mL.kg-1.min-1) after cooling to 13 degrees C. Methodology included radioactive microsphere determination of cerebral blood flow; calculation of cerebral oxygen extraction (arteriovenous oxygen content difference) and consumption; measurement of glucose consumption, and determination of cerebrovascular resistance. Measurements were obtained at baseline (37 degrees C), 13 degrees C, and 30 degrees C and at 2, 4, and 8 hours after HCA or low-flow CPB. No neurologic deficits were observed in any of the survivors (15/16). In both groups, cerebral metabolic rate of oxygen was maintained at baseline or greater levels postoperatively. Cerebrovascular resistance rose slightly in the low-flow CPB group postoperatively in contrast to a marked elevation in the HCA group. During the period of high cerebrovascular resistance after HCA, cerebral metabolic rate of oxygen was maintained by increased oxygen extraction. After low-flow CPB, oxygen extraction was not significantly different from baseline, presumably because of less severe changes in cerebrovascular resistance. Glucose metabolism followed the same trends as oxygen metabolism in both groups. These data suggest that after HCA there is a vulnerable interval, lasting as late as 8 hours postoperatively, in which cerebrovascular resistance remains high and cerebral metabolism is maintained primarily by high oxygen and glucose extraction. Any additional stress during this interval (a decrease in arterial oxygen content or perfusion pressure) could result in cerebral injury.

Animals↗