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Biomedical subjects

C Ozbek

Publications and source records attributed to C Ozbek.

At least 37 records · Page 2Linked to original sources
PubMed1997

Low energy transvenous cardioversion of short duration atrial tachyarrhythmias in humans using a single lead system.

The purpose of this study was to investigate the efficacy and safety of atrial cardioversion using an endocardial single lead system presently used for ventricular defibrillation. The study population consisted of 26 recipients of an ICD in combination with a conventional endocardial single lead system with the proximal spring electrode as anode in the SVC and the distal as cathode in the apex of the RV. Atrial tachyarrhythmias were induced by right atrial burst pacing. If the arrhythmia sustained > 1 minute, biphasic shocks synchronized with the R wave were delivered using the implanted device, beginning with an energy of 4 J. If 4 J failed to terminate the arrhythmia, energy was increased stepwise, if the first shock was successful, a step-down testing was performed after reinduction of atrial tachyarrhythmias. The mean atrial defibrillation threshold was 2.3 +/- 1.2 J (range, 0.5-5 J). A total of 154 shocks were delivered and no adverse effects were observed. The mean defibrillation threshold for atrial flutter was somewhat lower than that for AF (1.8 +/- 1 J vs 2.7 +/- 1.4 J, P = 0.08). There was no correlation between the atrial defibrillation threshold and a history of previously occurring atrial tachyarrhythmias, the kind of the underlying heart disease, a prescription of antiarrhythmic drugs, the dimension of the LA, the LVEF, or the ventricular DFT. Internal atrial cardioversion of short duration atrial tachyarrhythmias using a transvenous single lead system designed for ventricular defibrillation is feasible and safe at low energies, and may have important clinical applications.

Adult↗
PubMed1996

Atrial defibrillation: can modifications in current implantable cardioverter-defibrillators achieve this?

Atrial fibrillation (AF), the most common arrhythmia resulting in hospital admission, is a major health problem. The limited efficacy of antiarrhythmic drugs to control this rhythm disorder and their potential proarrhythmic risk led to the development of new techniques to ameliorate the treatment of AF. Transvenous atrial defibrillation using endocardial electrodes has been shown to be effective at low energy levels. An implantable atrial defibrillator could be a potentially valuable treatment option for patients with paroxysmal AF that is medically refractory. Research is currently under way to investigate several critical issues concerning this new therapeutic concept: long-term efficacy, safety, patient's tolerance, and an acceptable cost/benefit ratio. It is well known that AF often complicates the use of the implantable cardioverter-defibrillator (ICD) for ventricular tachyarrhythmias. Therefore, it would seem desirable to implement the capability for atrial defibrillation into current ICD systems. It has been shown that atrial defibrillation, using endocardial lead configurations specifically designed for ventricular defibrillation, is feasible at energies well within the capabilities of current ICD technology. Further research is needed to evaluate if some enhancement of the lead configuration in combination with possible advanced technology could reduce the atrial defibrillation threshold to a well tolerated level as a prerequisite for automated atrial defibrillation, in ICD recipients with concomitant paroxysmal AF.

Animals↗
PubMed1996

Effects of reperfusion after thrombolysis for myocardial infarction on the signal-averaged electrocardiogram.

Patients with early reperfusion after thrombolysis for acute myocardial infarction revealed a significantly reduced incidence of ventricular late potentials in the signal-averaged electrocardiogram obtained in the chronic post-infarction period in comparison to patients who did not meet the criteria for early successful thrombolysis (14 vs. 39%; P < 0.05). This data demonstrates that early reperfusion might prevent the development of an abnormal electrophysiological milieu after myocardial infarction.

Action Potentials↗
PubMed1996

Determinants of the natural course of ventricular late potentials after thrombolytic therapy for acute myocardial infarction.

The intraindividual changes of ventricular late potentials and their possible determinants were examined prospectively in 88 consecutive patients (male: 75; mean age: 58 +/- 9 years) after thrombolytic therapy for acute myocardial infarction. Late potential analysis was performed 4 weeks and 12 months after acute myocardial infarction. At the same time, a left heart catheterization was performed to assess the extent of coronary heart disease and left ventricular ejection fraction. The incidence of late potential 4 weeks after acute myocardial infarction was 15% (13/88 patients). Eighteen percent (16/88) of the patients revealed changing results of late potential analysis: 9 patients lost late potential (late potential pos./neg.) 1 year after acute myocardial infarction and 7 patients presented new formation of late potential (late potential neg./pos.). Preserved late potentials were found in four patients (late potential pos./pos.). Late potential analysis remained negative in 68 patients (late potential neg./neg.). There was no influence of age, gender, site of infarction, clinical course, and medical treatment on the natural course of late potential. Changing results of late potential analysis seemed to be correlated with the evolution of left ventricular ejection fraction and the dynamics of coronary heart disease. In the group late potential pos./pos., comparable values for left ventricular ejection fraction were measured at both examinations, whereas late potential neg./neg. had a significant increase in ejection fraction. In the group late potential pos./neg., a significant improvement in left ventricular function was also measured. In contrast, the late potential neg./pos. group tended to have lower left ventricular ejection fractions 1 year after infarction. In the late potential neg./pos. and late potential pos./pos. groups, the extent of coronary artery disease returned to conditions comparable to baseline despite an initial reduction after coronary revascularization performed 4 weeks after infarction. Late potential neg./neg. and late potential pos./neg. revealed a stable benefit gained from coronary revascularization with a persistent reduction in the number of diseased vessels. Dynamic changes in the results of the signal-averaged ECG 1 year after thrombolytic therapy for acute myocardial infarction were observed in 18% of the patients. These changes seem to be correlated with the evolution of left ventricular function and the dynamics of coronary artery disease.

Action Potentials↗
PubMed1996

Influence of a non-ionic radiography contrast medium on the microcirculation.

UNLABELLED: PURPOSE, MATERIAL AND METHODS: Microcirculatory disturbances may be responsible for some of the adverse effects induced by contrast media. The influence of iopromide 370 (Ultravist) on cutaneous microcirculation was therefore investigated in 15 patients in a prospective study. Twenty ml of iopromide and 20 ml 0.9% NaCl were injected as reference in the subclavian artery at the beginning of a diagnostic coronary angiography. Erythrocyte velocity was measured in ipsilateral nailfold capillaries at the beginning of, during, and after the injection continuously up to 6 min after injection. RESULTS: On average, 30 s after injection of contrast medium, erythrocyte velocity decreased significantly by 51.3% (p<0.0001) and remained reduced up to 120 s. This reaction was observed in 14 out of 15 patients. Three patients showed a temporary cessation of capillary blood flow. CONCLUSION: The adverse effects sometimes seen during coronary angiography can be explained if similar contrast medium induced microcirculatory disturbances in the myocardial vasculature.

Adult↗
PubMed1996

[Diurnal distribution of spontaneous ventricular tachyarrhythmias in patients with implanted cardioverter defibrillator].

The purpose of this study was to analyze temporal patterns of spontaneous ventricular tachyarrhythmias in patients (p) with implantable cardioverter-defibrillator (ICD). By reading out the ICD-data logs 725 arrhythmic episodes (e) from 43 patients were investigated. After grouping the episodes into four defined time periods (period 1: midnight to 6 a.m., period 2: 6 a.m. to noon, period 3: noon to 6 p.m., period 4: 6 p.m. to midnight) according to the data stored by the device, the percentage of episodes per time period has been calculated for each patient who experienced at least 10 arrhythmic events (n = 22). A significant peak occurrence (mean 34%) could been demonstrated for the morning hours (period 2). Analyzing patients individually, 4 subgroups could be identified: group 1 with an episode peak in period 2 (9 p, 277 e, p < 0.01), group with an episode peak in period 3 (4 p, 83 e, p < 0.01), group 3 with a peak occurrence in period 4 (3 p, 110 e, p < 0.01) and group 4 with an equal episode distribution over all four time periods (6 p, 187 e). Comparing sustained and nonsustained tachyarrhythmias, the nonsustained episodes were found to be distributed much more equally, meanwhile the circadian variation for fast (HR > or = 240/min) and slower (HR < 240/min) arrhythmias was identical. Regarding episodes of patients on beta-blocker or class III-antiarrhythmic therapy the same circadian variation has been found. There was no significant difference between the subgroups of patients with an episode peak in period 2 and the other patients concerning age, sex, cardiac disease, left ventricular ejection fraction, clinical arrhythmia, beta-blocker or class III-antiarrhythmics, number of recorded episodes or follow-up time. Further studies are needed to determine a possible correlation between these findings and different circadian variations in individual psychovegetative activity.

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↗
PubMed1996

[Initial clinical experiences with low energy internal cardioversion of chronic atrial fibrillation after unsuccessful external cardioversion].

Between January and September 1995, 54 consecutive patients (male: 34, age: 66 +/- 10 years) with symptomatic chronic atrial fibrillation (median duration: 4.5 months) were referred for external electrical cardioversion to our hospital. Mean left atrial diameter was 49 +/- 9 mm, heart disease was apparent in 81%. All patients were under antiarrhythmic drugs (class III: 85%). In 49 patients (91%) sinus rhythm was achieved. In five patients atrial fibrillation persisted after delivery of 360 Joules. These five patients were characterized by a significantly higher body weight in comparison to patients with successful external cardioversion. All five patients underwent low energy internal cardioversion the following day: biphasic R-wave synchronous shocks were delivered through catheters positioned in the right atrium and the coronary sinus using stepwise increased energy levels. Internal cardioversion was successful in all patients resistant to external cardioversion: stable sinus rhythm was established at a mean energy level of 13 +/- 6.7 Joules. No complications were observed. During the follow-up, each patient revealed a relapse of symptomatic atrial fibrillation within 2 weeks after internal cardioversion despite antiarrhythmic therapy, whereas only 16 patients (33%) lost sinus rhythm during the same period of time after external cardioversion (p < 0.01). During a mean follow-up of 283 +/- 72 days 21 patients (43%) preserved stable sinus rhythm after external cardioversion. Internal low energy cardioversion seems to be effective and safe in conversion of chronic atrial fibrillation resistant to external cardioversion. The clinical value of this invasive, time- and material-consuming therapy seems to be limited in this setting because of the high early relapse-rate in the investigated patient population. Further clinical studies in a larger cohort of patients are necessary.

Aged↗
PubMed1995

Comparison of mortality from acute myocardial infarction in patients receiving anistreplase with those not receiving thrombolysis.

Within 1 year, 434 patients were admitted to 14 hospitals with suspected acute myocardial infarction (AMI) < or = 4 hours after the onset of symptoms. Group A consisted of 171 patients (39%) treated with thrombolysis, and group B consisted of 263 patients (61%) with contraindications. Patients in group A more likely had a "definite AMI" (92%; group A1) than patients in group B (67%; group B1). Group B1 had 277 contraindications (1.6/per patient) with increased risk for life-threatening bleeding being the most frequently recorded at admission. The in-hospital mortality in group A1 was 7% (11 of 158) and in group B1, 27% (47 of 177) (p < 0.0001). Age and type of therapy (thrombolysis or no thrombolysis) were identified as independent predictors of increased mortality (p < 0.0001 and < 0.05, respectively). Thus, although most patients with an AMI are excluded from thrombolytic therapy because of contraindications, our data suggest that their in-hospital mortality is unexpectedly high. Further evaluation of this group of patients is warranted to define the impact of contraindications as an independent factor of mortality.

Aged↗
PubMed1995

Recombinant hirudin (HBW 023) prevents troponin T release after coronary angioplasty in patients with unstable angina.

OBJECTIVES: This study was performed to evaluate the efficacy of peri-interventional treatment with recombinant hirudin (r-hirudin [HBW 023]) compared with heparin in the prevention of troponin T release in patients with unstable angina. BACKGROUND: Percutaneous transluminal coronary angioplasty in patients with unstable angina is associated with a high risk of acute thrombotic complications. METHODS: Serial troponin T measurements were performed in 61 patients with unstable angina during the 48-h observation period after coronary angioplasty of the ischemia-related lesion. Patients were randomly assigned to peri-interventional intravenous treatment with either r-hirudin (dosage group I: 0.3-mg/kg body weight bolus, 0.12 mg/kg per h for 24 h; dosage group II: 0.5-mg/kg bolus, 0.24 mg/kg per h for 24 h) or heparin (150-IU/kg bolus, 20 IU/kg per h for 24 h). All patients received acetylsalicylic acid before coronary angiography. After 24 h, patients received a constant low dose infusion of either hirudin (0.04 mg/kg per h) or heparin (7 IU/kg per h) for another 24 h. The power of the study to detect a decrease in abnormal troponin T levels from 60% (heparin group) to 20% (combined r-hirudin groups) was 88%. RESULTS: Serial troponin T measurements revealed two peaks within the 48 h after coronary angioplasty in the heparin but not the hirudin groups. An elevated serum troponin T concentration (> 0.2 ng/ml) within 48 h of coronary angioplasty was found in 9 (24%) of 38 patients in the hirudin groups (5 [25%] of 20 in dosage group I; 4 [22%] of 18 in dosage group II) compared with 11 (58%) of 19 in the heparin group (p = 0.01). We observed major cardiac events (death, myocardial infarction, abrupt vessel closure) in 1 (4.8%) of 21 patients in dosage group I, 1 (5.3%) of 19 in dosage group II and 3 (14.3%) of 21 in the heparin group (p = 0.33). CONCLUSIONS: In this pilot trial, hirudin appears to be superior to heparin in preventing troponin T release after coronary angioplasty.

Angina, Unstable↗
PubMed1994

Myocardial metabolic imaging by means of fluorine-18 deoxyglucose/technetium-99m sestamibi dual-isotope single-photon emission tomography.

The detection of preserved glucose uptake in hypoperfused dysfunctional myocardium by fluorine-18 deoxyglucose (FDG) positron emission tomography (PET) represents the method of choice in myocardial viability diagnostics. As the technique is not available for the majority of patients due to cost and the limited capacity of the PET centres, it was the aim of the present work to develop and test FDG single-photon emission tomography (SPET) with the means of conventional nuclear medicine. The perfusion marker sestamibi (MIBI) was used together with the metabolic tracer FDG in dual-isotope acquisition. A conventional SPET camera was equipped with a 511-keV collimator and designed to operate with simultaneous four-channel acquisition. In this way, the scatter of 18F into the technetium-99m energy window could be taken into account by a novel method of scatter correction. Thirty patients with regional wall motion abnormalities at rest were investigated. The results of visual wall motion analysis by contrast cine-ventriculography in nine segments/heart were compared with the results of quantitative scintigraphy. The scintigraphic patterns of MIBI and FDG tracer accumulation were defined as normal, matched defects and perfusion-metabolism mismatches. Spatial resolution of the system was satisfactory, with a full width at half maximum (FWHM) of 15.2 mm for 18F and 14.0 mm for 99mTc, as measured by planar imaging in air at 5 cm distance from the collimator. Image quality allowed interpretation in all 30 patients. 88% of segments without relevant wall motion abnormalities presented normal scintigraphic results. Seventy-five akinetic segments showed mismatches in 27%, matched defects in 44% and normal perfusion in 29%. We conclude that FDG-MIBI dual-isotope SPET is technically feasible with the means of conventional nuclear medicine. Thus, the method is potentially available for widespread application in patient care and may represent an alternative to the 201Tl reinjection technique.

Coronary Disease↗
PubMed1994

Factors affecting the restenosis rate after percutaneous transluminal coronary angioplasty.

In an open study follow-up angiographies were performed independently from the clinical course on altogether 131 consecutive patients (99 men, 32 women) six months after percutaneous transluminal coronary angioplasty (PTCA). During this period patients received at least 320 mg of aspirin daily. Possible factors affecting the restenosis rate included age, sex, diabetes mellitus, arterial hypertension, abnormal lipid metabolism, smoking, dosage of aspirin administered, degree of stenosis shown by affected vessels before dilatation, number of vascular segments dilated and platelet reactivity. Restenosis was defined as a renewed narrowing of the dilated segment by 50% or more, with an increase in stenosis by at least 20%. In the present study the following restenosis rates were found six month after a primarily successful PTCA: 30% for the entire sample (39 out of 131 patients); 25% in patients with normal platelet function, 50% in those with mildly abnormal platelet function, and 60% in those with frankly abnormal platelet function; 24% in non-diabetic patients and 45% in diabetics. Analysis of the findings showed that abnormal platelet function and the presence of diabetes mellitus were the most important factors in the subsequent development of restenosis after angioplasty. The same also applied in a more restricted manner to the degree of stenosis present before angioplasty.

Aged↗
PubMed1994

Clinical results of coronary excimer laser angioplasty: report from the European Coronary Excimer Laser Angioplasty Registry.

From January 1991 to January 1993 the clinical and angiographic data of 470 patients were included in the European Coronary Excimer Laser Angioplasty Registry. Symptoms were CCS class 3 in 23% and CCS class 4 in 14.7%; unstable angina was present in 14.7% and 6.6% of patients had acute myocardial infarction. Of 477 treated lesions, 60% were type B2, and 19% type C. The lesion was located in the LAD in 61%, in the LCX in 16%, in the RCA in 20%, in a protected left main stem in 1.3% and in a saphenous vein graft in 2.5%, respectively. Failure of laser angioplasty occurred in 56 (12%) interventions. By multivariate analysis failure was associated with the intention to treat long segmental lesions (risk ratio (RR) 3.6, confidence interval (CI) 2.9 to 4.4; P = 0.0005), segments with severe prestenotic tortuosity (RR 3.5, CI 2.4 to 4.6; P = 0.02) and total occlusions (RR 2.1; CI 1.4 to 2.8; P = 0.05). Complications included vasospasm (13.4%), dissection (14.7%), flow limiting dissection (4%), reclosure (7.8%), and perforation (1.9%). Myocardial infarction occurred in 2.1%, CABG was requested in 1.9%, and the mortality was 1.5%. Procedural success was achieved in 89%. Individual morphological criteria for a reduced procedural success were the presence of a thrombus (RR 6.4; CI 5.0 to 7.7; P = 0.007) and vessel calcification (RR 2.6; CI 1.9 to 3.2; P = 0.005). Procedural success was slightly lower in type C lesions (86%) than in type B2 (88%) type B1 (95%), and type A lesions (92%), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1994

High resolution ECG and left ventricular volume after acute myocardial infarction.

The presence of ventricular late potentials (LPs) early after acute myocardial infarction (AMI) was recently reported to correlate with left ventricular dilatation subsequent to AMI. We assessed prospectively the relationship between LP (time domain) in the late phase of AMI and left ventricular end-diastolic volume (EDV) measured by equilibrium radionuclide angiocardiography 4 weeks and 12 months after AMI. In 80 consecutive patients 4 weeks and 12 months after thrombolytic therapy for AMI, LP and EDV were determined (EDV1, EDV2). There was no significant correlation between QRS duration (r = 0.18), RMS40 (r = 0.08), or LAS40 (r = 0.1) and EDV1 or EDV2 in patients with or without LP at baseline. In both groups (patients with [n = 15] and without LP [n = 65]), EDV1 and EDV2 were comparable (128 +/- 32 mL vs 126 +/- 35 mL; 114 +/- 40 mL vs 117 +/- 36 mL; P = NS). In addition, there was no significant difference between EDV1 and EDV2 in patients who developed new LP (n = 6) or lost LP (n = 9) 12 months after AMI. In contrast to LP in the very early phase after AMI, there seems to be no significant correlation between the high resolution ECG in the late phase after thrombolytic therapy for AMI and left ventricular EDV.

Electrocardiography↗
PubMed1993

[Complications after coronary angiography and balloon dilatation].

All major complications within four weeks after diagnostic cardiac catheterization (DCCA; n = 4,778) or percutaneous transluminal coronary angioplasty (PTCA; n = 3,073) were analysed prospectively in 7,851 patients (5,769 men, 2,082 women; mean age 59.4 [16-88] years). There were 116 such complications in 114 patients, 46 (0.9%) after DCCA, 70 (2.3%) after PTCA. 76% of all complications occurred during the first two days after the procedure: bleeding in 29 patients, false aneurysms in 15, arterial occlusions in 12, venous ones in three, cerebral ischaemia in 12, fulminant pulmonary emboli in three, cardiac complications in 27, and others in 15. There were five deaths in connection with a DCCA, 18 with PTCA. Complications were twice as common in women as in men (DCCA: 1.5% vs 0.7%, P < 0.05; PTCA: 4.2% vs 1.7%, P < 0.001). Complications after DCCA were more frequent in those aged over 55 years (1.2% vs 0.3%, P < 0.05); after PTCA they were more frequent in those aged over 65 years (4.1% vs 1.3%, P < 0.05). Other risk factors for complications were: peripheral arterial occlusive disease for arterial occlusion (P < 0.001), high heparin dosage with DCCA (P < 0.05), and additional venous puncture with DCCA (P < 0.01).

Adolescent↗
PubMed1992

[Excimer laser coronary angioplasty after primary unsuccessful PTCA].

Excimer laser coronary angioplasty is a new technique for ablation of coronary stenosis, however, the indications for its application are still controversial. We describe two male patients, 60 and 65 years old, who underwent unsuccessful balloon PTCA with a short, concentric and calcified coronary stenosis, although balloon inflation pressure was increased to a maximum in both cases. Excimer laser angioplasty following the failed procedures showed no evidence for tissue ablation angiographically, but a repeat attempt with balloon angioplasty was successful in both cases. Thus, laser angioplasty may be considered as an adjunct technique to balloon angioplasty after a failed PTCA in resistant, non-inflatable lesions.

Aged↗
PubMed1991

Treatment of unstable angina pectoris (European experience).

Unstable angina pectoris is used to describe accelerated angina, new onset of angina, or prolonged angina. The natural history of the angina varies according to clinical presentation. The 1-year mortality rate ranges from 2% to nearly 40%. Specific therapy includes nitrates, beta-adrenergic blockers, and/or calcium antagonists as well as antithrombotic therapy in the form of aspirin. Patients with severe angina at rest and ST- and T-wave changes should be admitted to a coronary care unit where full-dose heparin is administered. Coronary angiography should be performed in individuals who fail to respond to the conventional therapy in order to evaluate other therapeutic options, including percutaneous transluminal coronary angioplasty (PTCA) and coronary bypass surgery. In some cases, especially in patients with intracoronary thrombus, thrombolytic therapy may be beneficial.

Angina, Unstable↗