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Biomedical subjects

B Heublein

Publications and source records attributed to B Heublein.

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

Prediction of the onset of atrial fibrillation after cardiac surgery using the monophasic action potential.

OBJECTIVE: To show that the monophasic action potential (MAP) recorded continuously from human epicardium may be used to predict the imminent onset of atrial fibrillation or flutter (AF) following surgery, thus allowing prophylactic treatment to be started. PATIENTS: 22 patients (14 male, 8 female; mean (SD) age 64 (12) years) undergoing aortic valve replacement. SETTING: Tertiary referral centre. METHODS: Over a mean observation period of 8 (2.7) days (range 4 to 14), nine episodes of AF were seen in six patients. Before AF, specific and significant alterations of the MAP morphology were observed. In seven of nine episodes the MAP shortened (25 (4)% 60 minutes before AF), developed a triangular shape, and the plateau amplitude decreased from 5.3 (1.2) to 2 (0.2) mV. In the two remaining episodes the beat to beat variability of cycle length and MAP duration at 90% repolarisation (MAPd90) increased significantly from 24 (7) ms and 12 (8) ms (24 hours before AF) to 137 (27) ms and 56 (11) ms (30 minutes before AF) respectively. AF was successfully treated by the administration of sotalol in three cases and by a combination of verapamil and digoxin in a further four. Previously observed changes of MAPd90 and MAP morphology regressed after conversion to sinus rhythm. CONCLUSIONS: The continuous and intermediate term recording of the MAP from atrial epicardium appears to be a valid tool for detecting imminent AF after cardiac surgery with a high sensitivity (99%) and specificity (88%). Optimised antiarrhythmic treatment may thus be given selectively for prophylaxis.

Action Potentials↗
PubMed1998

Silicon carbide-coated stents: clinical experience in coronary lesions with increased thrombotic risk.

PURPOSE: To report the results of a prospective, nonrandomized, multicenter study of a semiconductor-coated stent in coronary lesions at high risk for stent thrombosis. METHODS: A balloon-expandable tantalum stent was coated with silicon carbide to enhance thromboresistance (Tensum). Patients were enrolled in an observational study that compared coronary stenting with the Tensum stent in patients at low risk for stent thrombosis against those with factors predisposing to local thrombosis (acute myocardial infarction, small vessel diameter, recanalized chronic total occlusion, saphenous vein bypass grafts, and coronary allograft vascular disease). RESULTS: In 294 patients with 364 coronary lesions, 111 patients with 142 lesions were assigned to the high-risk group. Overall, 406 Tensum stents were implanted (94% procedural success) using antiplatelet medication only after the procedure. The stent thrombosis rate (2.7% overall) in the high-risk group (3.6%) was not significantly different from that of the low-risk patients (2.1%). CONCLUSIONS: Silicon carbide coating on coronary stents may inhibit acute/subacute stent thrombosis even in patients at high risk. Randomized trials are underway for further evaluation of this promising coated stent.

Adult↗
PubMed1998

Silicon Carbide Coating Ñ A Semiconducting Hybrid Design of Coronary Stents Ñ A Feasibility Study.

OBJECTIVE: To determine the rates of subacute and acute thrombotic stent occlusion in patients with normal and high risk for stent thrombosis and to assess the 6 month follow-up with respect to in-stent restenosis, using a new principle of semiconductor coating (active passivating as metallic hybrid design). DESIGN: Open, non-randomized, prospective, observational, feasibility study. PATIENTS: One hundred sixty-five patients (215 stents) were scheduled consecutively with respect to lesions suitable for slotted tube stent implantation. Two subgroups of patients (stents) were identified based on the local thrombotic risk (common indications for stent implantation Ñ group I; lesions with high(er) risk for stent implantation (group II). A closed clinical 3Ð12 (mean 6.5 +/- 2.3) months follow-up was done in 126 (92.6%) eligible patients [164 (97.6%) stents]. Angiographic and/or IVUS data were available in 96 of 136 eligible patients (70.6%) after stenting 6.0 +/- 2.1 months). STENT-MATERIAL/MEDICATION: Balloon expandable tantalum three segment slotted tube stents which were coated with silicon carbide, diameter ranged from 2.5 to 4.0 mm were used. Stent deployment was limited by inflation pressure (12Ð16 Bar). Apart from patients with acute myocardial infarction (n = 15 stents) patients received heparin loading dose during the procedure only, no oral anticoagulation except aspirin (300 mg p.d.) and ticlopidine (250Ð500mg p.d.) given over 1 month. RESULTS: Acute complications. No in-hospital mortality occurred, stent-related myocardial infarction was 1.9%; major bleedings 0.5% of implanted stents. Acute stent thrombosis 1.4%, subacute stent thrombosis occurred in 0.5% (no significant difference between group I and II). Late events: From 136 eligible patients (range 15 daysÐ14 months) (187 stents) 92 patients (67.6%) with 142 stents (75.9%) were event-free. In-stent restenosis. Thirty-six percent (biased group of patients with events) resp. 26.8% (including negative clinical events) of the implanted stents were restenosed. An inverse relationship between vessel size and in-stent (re)stenosis was observed. CONCLUSIONS: Silicon-carbide coated coronary stents are suitable in standard as well as in high-risk situations. The rates for acute or subacute stent thrombosis are acceptably low even when using post-procedural conventional (aspirin/ticlopidine) anti-thrombotic medication in patients who are at high risk for stent thrombosis. An inverse relationship exists between stent-restenosis rate and the size of the reference segment of the implanted vessel.

Journal Article↗
PubMed1997

Coronary artery stenting in cardiac allograft vascular disease.

Cardiac allograft vascular disease is characterized by diffuse and multifocal heterogeneous myointimal hyperplasia with or without vascular remodeling. Catheter-based interventions are indicated in selected patients. This study documents our experience with percutaneous transluminal coronary angioplasty and coronary stents (n = 48) in a group of 27 patients 5.7 +/- 2.9 years after heart transplantation. Early and intermediate results were controlled by angiography and intravascular ultrasound. Conventional percutaneous transluminal coronary angioplasty resulted in a mild and mostly inadequate gain in luminal dimensions (lumen area: 3.17 +/- 0.92 mm2 to 3.70 +/- 1.21 mm2; minimal lumen diameter: 1.84 +/- 0.23 mm to 2.04 +/- 0.36 mm). Coronary stenting led to a further improvement of luminal gain (lumen area: 3.70 +/- 1.21 mm2 to 5.86 +/- 1.76 mm2; minimal lumen diameter: 2.04 +/- 0.36 mm to 2.53 +/- 0.38 mm). These results were stabilized by application of aspirin and ticlopidine only. There were no stent thromboses or bleeding complications, and early hospital discharge of the patients was possible. At follow-up (mean follow-up period 7.72 +/- 5.45 months (range 0.50 to 23.13 months) all patients were clinically event free. In six of 24 stented vessels (25%) in 16 patients, significant restenosis (>50%) was found by intravascular ultrasound (n = 20) or by angiography (n = 4) 6 months after stent placement. We conclude that in eligible cardiac allograft vascular disease lesions primary stenting may be the method of choice. However, further evaluation of the modalities of stent application and different stent designs with respect to long-term survival is necessary.

Adult↗
PubMed1996

Coating of cardiovascular stents with a semiconductor to improve their hemocompatibility.

Thrombogenesis on artificial surfaces can be described as an electron transfer reaction. To inhibit this oxidation process and thereby achieve high hemocompatibility, a surface requires semiconducting properties. However, because all known solid semiconductors are extremely brittle, the requirements for high hemocompatibility and mechanical stability cannot be met by any single material. Therefore, a hybrid design is introduced as a new approach to improve the hemocompatibility of cardiovascular stents.

Angiography↗
PubMed1995

Usefulness of increased myocardial cyclic adenosine 3',5'-monophosphate content as a sign of rejection after cardiac transplantation.

Cardiac allograft rejection represents a series of cellular and molecular events triggered by the recognition of the graft by the host immune system. One of the second messenger systems involved in mitogenic mechanisms is the cyclic adenosine 3',5'-monophosphate (cAMP)-coupled signaling system. The aim of this preliminary study was to evaluate whether rejection after cardiac transplantation is accompanied by changes in the expression of cAMP. Myocardial cAMP content was determined by radioimmunoassay in endomyocardial biopsy specimens taken during routine follow-up after cardiac transplantation with or without cellular and/or vascular (i.e., coronary vasculopathy) rejection, respectively. Analysis of the different subgroups of patients showed that patients without any signs of rejection (no vasculopathy, no cellular rejection) had the lowest myocardial cAMP content (1.41 +/- 0.12 pmol/mg wet weight). Patients with either cellular or vascular rejection had significantly higher myocardial cAMP levels (2.25 +/- 0.29 and 2.24 +/- 0.59 pmol/mg wet weight, respectively, p < 0.05). Patients with both cellular rejection and coronary vasculopathy had the highest cAMP levels (5.95 +/- 1.6 pmol/mg wet weight; p < 0.001). We speculate that cAMP may play a functional role in mediating rejection induced by mitogenic factors activated after cardiac transplantation, suggesting a possible "cross-talk" between different cellular signaling pathways.

Adult↗
PubMed1995

Endothelial dysfunction in heart transplanted patients with graft vasculopathy.

The pathological mechanism of cardiac transplant vasculopathy (TVP) is uncertain. We tested the hypothesis that the endothelial function, in terms of the release of endothelium-derived relaxing factor, is impaired in patients with angiographic evidence of transplant vasculopathy. In a pilot study, the effects of the substances used (substance P, acetylcholine, nitroglycerin) were assessed as regards tone of pre-contracted human coronary arteries in vitro, obtained from recipient hearts during cardiac transplantation. The study shows that substance P is a "pure' endothelium-dependent dilator of epicardial human coronary arteries, whereas acetylcholine has a more complex effect on vascular tone involving both a direct effect on the endothelium and the smooth muscle cells. In a second pilot study, the effects of intracoronary infusions of substance P (5-100 pmol.min-1) and acetylcholine (2-50 nmol.min-1) on flow velocity were compared in 10 patients undergoing cardiac catherization after heart transplantation. Flow velocity was determined by a 3F Doppler catheter placed into the proximal segment of the left anterior descending artery (LAD). Both drugs increased concentration-dependent flow velocity; substance P and acetylcholine maximally increased flow velocity by about 85 +/- 24% and 143 +/- 15%, respectively (P < 0.05). In a third study, 23 patients undergoing diagnostic cardiac catheterization were included approximately 40 months after heart transplantation. Patients were classified into those with (n = 8) and those without (n = 15) angiographic evidence of TVP. Coronary flow velocity (by Doppler) and epicardial coronary diameter (by quantitative angiography) were determined after intracoronary injections of substance P (20 pmol), nitroglycerin (0.1 mg), and papaverine (8 mg). Substances were injected through the central lumen which was placed into the LAD. Increases in flow velocity in response to substance P were significantly less in patients with TVP than in patients without evidence of TVP. Moreover, flow-mediated vasodilation in response to papaverine was almost abolished in patients with TVP. Vasodilation in response to nitroglycerin and maximal increase in flow velocity in response to papaverine was similar in both groups. These results suggest that TVP is associated with endothelial dysfunction, which may contribute to the pathogenesis of TVP and its vascular complications.

Acetylcholine↗
PubMed1994

Acute influence of beta-adrenergic antagonists on left ventricular diastolic function: contrasting results after administration of celiprolol and metoprolol.

Various beta-adrenergic receptor antagonists have different effects on myocardial function. A clinical study was performed in 30 patients with symptomatic coronary artery disease and systemic hypertension to compare the effects of single intravenous doses of 0.15 mg/kg celiprolol (n = 16) (third generation beta-blocking agent) and metoprolol (n = 14) (second generation) on left ventricular diastolic function. Parameters derived from pressure, volume, flow, time intervals and their combination were used to characterise diastolic function. After celiprolol administration, parameters of diastolic myocardial function improve (dp/dtip-; relaxation time constant T1, peak filling rate PFR; first-third filling rate FF1/3 or diastolic wall stress-time integral Sigdiasc) or remain unchanged. In contrast, after metoprolol administration parameters of diastolic function seem to be deteriorated (dp/dtip-, T1; Sigdiasc). This indicates an improvement in myocardial relaxation and filling under the influence of celiprolol but not under metoprolol. The left shift of the pressure-volume loops after celiprolol (n = 13), in contrast to metoprolol, supports this interpretation. Celiprolol did not show any deterioration of diastolic function in patients with coronary heart disease and arterial hypertension under these acute conditions.

Adrenergic beta-Antagonists↗
PubMed1994

[Follow-up and characteristics of restenoses after coronary stent implantation in asymptomatic patients and patients with few symptoms].

Following coronary Palmaz-Schatz single stent implantation 50 patients had an angiographic follow-up after 4-6 and after 12 months. Quantitative angiography revealed that the restenosis process has finished 4-6 months after stent implantation in the majority of patients. In the present study, 6% had, however, developed symptomatic restenosis at 1-year follow-up. Detailed assessment of 15 patients revealed that the residual stenosis after stent implantation is most prominent at the stent edges, however, restenosis did occur in all segments in about the same amount. Analysis of several clinical and morphologic variables did not reveal any particular risk factor for the development of restenosis. The results of the present study do suggest that follow-up angiography should be performed 4-6 months after stent placement.

Adult↗
PubMed1993

Impaired coronary dilator responses to substance P and impaired flow-dependent dilator responses in heart transplant patients with graft vasculopathy.

OBJECTIVES: Because pathologic mechanisms for transplant vasculopathy are still uncertain, we tested the hypothesis that endothelial function, in terms of the release of endothelium-derived relaxing factor (EDRF), is impaired in patients with evidence of angiographic transplant vasculopathy. BACKGROUND: The long-term prognosis after heart transplantation is mainly determined by the development of transplant vasculopathy. METHODS: The study included 23 patients undergoing diagnostic cardiac catheterization approximately 40 months after heart transplantation. Patients were classified into those with (n = 8) and those without (n = 15) angiographic evidence of transplant vasculopathy. Coronary flow velocity (by intravascular Doppler echocardiography) and epicardial coronary diameter (by quantitative angiography) were determined after intracoronary bolus injections (1 ml) of the endothelium-dependent dilator substance P (20 pmol) and the endothelium-independent dilators nitroglycerin (0.1 mg) and papaverine (8 mg). Substances were injected through the lumen of the Doppler catheter, which was placed into the midportion of the left anterior descending artery. RESULTS: Increases in blood flow velocity in response to substance P were significantly less in patients with than in patients without evidence of transplant vasculopathy. In addition, flow-mediated dilation of epicardial coronary arteries in response to papaverine was abolished in patients with such evidence. Vasodilation of epicardial coronary arteries in response to nitroglycerin and increases in flow velocity in response to papaverine were similar in both groups. CONCLUSIONS: These results suggest that transplant vasculopathy in heart transplant patients is associated with endothelial dysfunction (that is, impaired EDRF-mediated vasodilation). Furthermore, responsiveness of epicardial arteries to increased flow appears to be abolished in patients with evidence of transplant vasculopathy. These abnormal vascular functions may contribute to the pathogenesis of transplant vasculopathy and its vascular complications.

Adult↗
PubMed1993

The inferior epigastric artery for coronary bypass grafting. Functional assessment and clinical results.

The use of the internal thoracic artery (ITA) for coronary bypass grafting (CBG) has resulted in superior long-term function. Other autologous arteries have been investigated also, but the role of the inferior epigastric artery (IEA) for CBG has not yet been defined. From March 91 to August 92, IEA grafts were used in 50 male patients aged 30-68 years/mean 54.9) combined with 1 (n = 40) or 2 (n = 8) ITA grafts. Pedicled grafts were dissected (length: 8.5-16.5, 13.1 cm) but left in situ covered by sponges soaked with papaverine solution until going on bypass. There was no mechanical or pharmacological intraluminal manipulation. Distal free flow (in situ) was 41.8 ml/min (16-95 ml/min). A total of 146 grafts were constructed (2.9/patient), including free IEA-CBG performed to the LAD (n = 28) or its diagonal branches (n = 22). The operative mortality was 2.0%, there were no sternal wound complications but superficial abdominal infections in 5 patients. Recatheterization (1-6 months postoperatively) revealed an 82.6% patency rate (19/23) in IEA, compared to 100% in ITA, grafts. In vitro stimulation of arterial segments by endothelium- or muscular-dependent relaxation revealed a response (% of the maximum) of 92.4% in IEA and 74.6% in ITA to acethylcholine, while the response to nitroglycerin was 92.7% and 98.6%, respectively. Our clinical results would support the concept of combining IEA and ITA for arterial revascularization in CBG. Inferior epigastric artery grafts should provide adequate blood flow and good long-term patency due to preservation of their endothelial function.

Abdominal Muscles↗
PubMed1993

A case of coronary stenosis developing after successful aortic valve repair in Cogan's syndrome.

Cogan's syndrome has been described as entity of progressive deafness and interstitial keratitis with variable cardiovascular involvement leading to aortic insufficiency or orificial stenosis of coronary or aortic arch vessels. So far, aortic valve replacement either with mechanical or biological prosthesis was favored for correction of the valvular lesion. A patient with primary successful aortic valve repair followed by coronary revascularization for left coronary ostial stenosis occurring after the first operation is presented.

Adult↗
PubMed1993

[Multicenter results of coronary implantation of balloon expandable Palmaz-Schatz vascular stents].

Intracoronary stenting was designed to handle acute vessel closure after balloon angioplasty and to reduce the rate of restenosis. In three cardiology centers the implantation of 200 balloon-expandable Palmaz-Schatz stents was attempted in 179 patients. The implantation was successful in 170 patients (95%). During bail-out implantation for acute vessel closure or symptomatic dissections after balloon angioplasty, implantation succeeded in 60 (91%) of 66 attempted patients, who recovered immediately from ischemia. Three patients received emergency bypass surgery and three patients were kept on medical therapy. Restenosis after 4 to 6 months, defined as > 50% diameter reduction, was documented angiographically in 18 (15.3%) of 118 presently controlled patients. Patients with single stent implantation (n = 106) presented a late restenosis rate of 10.4% in contrast to patients with multiple stent implantation (n = 12), who presented a restenosis rate of 58.4%. Similar results on restenosis were found for patients with elective and bail-out stent implantation. Acute thrombotic stent occlusion occurred in three patients (1.8%) during the first 24 h after stenting. Three to 9 days after implantation subacute stent thrombosis occurred in 15 (8.8%) of 170 patients. Despite adequate therapy including thrombolysis, balloon angioplasty or emergency bypass surgery in 14 of 15 patients Q-wave myocardial infarction was documented in six patients and non Q-wave myocardial infarction in five patients. The following parameters were identified as risk factors for the development of subacute stent thrombosis: bail-out indication, unstable angina, type C lesion, stenosis length > 1.5 cm, plaque area > 3.5 mm2, symptomatic dissection after balloon angioplasty, incomplete wrapping of the dissection after stenting and residual distal vessel irregularities after stenting. Bleeding complications occurred in 12.4% of the patients and were related to the anticoagulation and antiaggregation therapy. In conclusion, the implantation of Palmaz-Schatz stents is an excellent bail-out device to treat acute vessel closure or symptomatic dissections after angioplasty. Elective and bail-out single stent implantation is associated with a reduced rate of restenosis when compared to conventional balloon angioplasty. At present, subacute stent thrombosis and bleeding complications are the major limitations with a combined rate of 15.9%.

Adult↗
PubMed1992

Changes in cardiac beta 1- and beta 2-adrenoceptor densities after human cardiac transplantation: relation to transplant coronary vasculopathy and pretransplantation disease.

In 100 patients 12 to 60 months after cardiac transplantation, the influence of transplant coronary vasculopathy and of the pretransplantation disease (end-stage heart failure caused by coronary artery disease or dilated cardiomyopathy) on the beta-adrenergic receptor (AR) numbers and beta 1/beta 2-AR ratio of right ventricular biopsies was determined. Patients with coronary vasculopathy (CVP) after cardiac transplantation had lower absolute numbers of beta 1-AR compared with patients without CVP. Since patients with CVP had increased left ventricular (LV) end-diastolic pressure and LV muscle mass, it is suggested that decreased beta 1-AR may be the result of an altered hemodynamic situation of the transplanted heart after development of CVP. Patients with dilated cardiomyopathy (DCM) before cardiac transplantation showed a decrease in total beta-AR and of the beta 1/beta 2-AR ratio as a result of an increase in beta 2-AR and a decrease in beta 1-AR numbers. The decreased beta 1/beta 2-AR ratio in patients with previous DCM may indicate that the beta-AR system of the transplanted heart might be influenced (at least in part) by pathophysiologic factors that are characteristic of the pretransplantation disease ultimately leading to cardiac transplantation and persisting after cardiac transplantation.

Adult↗