Search PubMed⌕ Search

Biomedical subjects

G Steinbeck

Publications and source records attributed to G Steinbeck.

At least 37 records · Page 2Linked to original sources
PubMed2003

Non-invasive intravenous coronary angiography using electron beam tomography and multislice computed tomography.

BACKGROUND: Electron beam computed tomography (EBCT) and multislice computed tomography (MSCT) are both suitable for non-invasive identification of coronary stenoses. OBJECTIVE: To compare intravenous coronary EBCT angiography (EBCTA) and MSCT angiography (MSCTA) with regard to image quality and diagnostic accuracy. METHODS: EBCTA was done using an Imatron C-150 XP scanner in 101 patients following a standard protocol (slice thickness 3 mm, overlap 1 mm, acquisition time 100 ms, prospective ECG trigger). For MSCTA in a different set of 91 patients (using a Siemens Somatom Plus4VZ scanner), the whole volume of the heart was covered in a spiral technique by four simultaneous detector rows. Using retrospective ECG gating, the raw data were reconstructed in (mean (SD)) 215 (12) axial slices acquired in diastole (slice thickness 1.25 mm, overlap 0.5 mm, acquisition time 250 ms/slice). RESULTS: With EBCTA, 76% of predetermined coronary segments in a nine segment model could be assessed with diagnostic image quality, and with MSCTA, 82%. A low contrast to noise ratio with EBCTA, and the presence of motion artefacts with MSCTA were the main reasons for inadequate image quality. Using conventional angiography as the gold standard, 77% of stenoses of > 50% could be identified correctly with EBCTA and 82% with MSCTA. Significant stenoses were correctly ruled out in 93% of segments with EBCTA, and in 96% of segments with MSCTA. The average contrast to noise ratio was higher with MSCTA than with EBCTA (9.4 v 6.5; p < 0.001). CONCLUSIONS: EBCTA and MSCTA show similarly high levels of accuracy for determining and ruling out significant coronary artery stenoses. MSCTA is capable of providing good image quality in more coronary segments than EBCTA because of its better contrast to noise ratio and higher spatial resolution. Motion artefacts seen at heart rates of > 75 beats/min and a higher radiation exposure are the main limitations of MSCTA.

Coronary Angiography↗
PubMed2002

[Surgical and interventional use of radiofrequency current: is there interference with implantable cardioverter/defibrillators?].

BACKGROUND: During surgical and interventional procedures, interactions between implantable cardioverter defibrillators (ICD) and electrical cautery, respectively, application of radiofrequency (RF) energy may occur. Induction of inadequate shock therapies or device malfunction may result and represent a potential perioperative hazard for the patient. METHODS: Hence, we analyzed the intraoperative interactions in 23 consecutive ICD patients with regard to different surgical and interventional procedures. Sixteen surgical operations (general surgery n = 7, urologic n = 5, abdominal n = 2, gynecological n = 1, thoracic n = 1) and 7 interventional therapies (RF catheter ablation n = 5, endoscopic papillotomy n = 2) were performed. The ICD devices were all located in the left pectoral position and consisted of 15 single and 8 dual chamber defibrillators. During the procedure tachyarrhythmia detection (VF 295 +/- 21 ms, VT 370 +/- 55 ms) of the devices was maintained active (monitoring mode); only ICD therapies were inactivated. The indifferent electrode of the electrical cauter/RF generator was placed in standard positions (right mid femoral position n = 18, thoracic spine area n = 5). After the procedure, the ICD memory was checked for detections, respectively, for changes of the programming. RESULT: There was no misdetection or reprogramming of the ICD caused by electrical cautery or RF energy. CONCLUSIONS: Despite the lack of undesired interactions ICDs should be inactivated preoperatively to assure maximum patient safety. However, should inactivation be ineffective or not manageable, electromagnetic interference is highly unlikely.

Adult↗
PubMed2002

[Detection of coronary calcinosis with multislice spiral computerized tomography: an alternative to electron beam tomography].

Electron-beam CT (EBT) has been used for years as the gold standard to quantify coronary artery calcification as a marker of coronary atherosclerosis. With the introduction of Multi-Slice Spiral CT (MSCT) technology in 1999, EBT is now challenged in the determination of coronary calcium. The aim of this study was to determine the diagnostic accuracy of MSCT for the assessment of coronary calcium, comparing this new technique to EBT. The study population consisted of 54 male patients, aged 58 +/- 11 years with suspected coronary artery disease. For EBT, 40 axial slices (scan time = 100 ms, slice thickness = 3 mm) were acquired in one breath-hold (35 +/- 5 s) using an ECG-trigger at 80% of the RR interval. For MSCT, simultaneous acquisition of four axial slices (scan time = 250 ms, slice thickness = 2.5 mm) allowed the entire heart (40 slices) to be covered in one breath-hold (25 +/- 5 s) using a prospective ECG-trigger (R--450 ms). For quantification of coronary calcium the Agatston and the Volumetric calcium score (VCS) were applied. Mean Agatston score of the study group was calculated as 88 +/- 111 (median = 45), which is between the 25th and 75th age-corrected percentile of asymptomatic patients. For the Volumetric calcium score, number of lesions, calcium mass and density, no statistical difference was found between both imaging modalities. Agatston and Volumetric calcium score were statistically different between and within both scans. Mean variability of VCS of the two methods was calculated as 24% and was in the range of repeated EBT studies (14-44.9%). The Multi-Slice Spiral CT scanner is equivalent to EBT for the determination of coronary calcium and can, therefore, be used for calcium screening. Using a prospective ECG-trigger technique, the application of the Agatston method delivers statistically different results in comparison to EBT. With the application of the spiral mode technique, retrospective ECG-trigger and thinner slice thickness, further improvement in variability can be expected, thus allowing for follow-up studies to determine progression or regression of atherosclerosis with high accuracy.

Aged↗
PubMed2002

[Mechanisms of initiation in atrial fibrillation].

Atrial fibrillation is the most relevant arrhythmia in daily clinical practice. The pathophysiology is determined by multiple independent reentrant wavelets in both atria. Repetitive triggers and an underlying substrate may favor the initiation and maintenance of atrial fibrillation. Mapping studies in patients with drug-refractory paroxysmal atrial fibrillation identified potentials from the ostia of pulmonary veins as a main source of triggers that initiate atrial fibrillation. In ongoing clinical trials, catheter ablation of pulmonary vein foci is used to eliminate atrial premature beats and thereby prevent the initiation of atrial fibrillation. The autonomic modulation of the heart rate and the occurrence of other supraventricular tachycardias that degenerate into atrial fibrillation are also considered as triggering mechanisms of atrial fibrillation. Since symptomatic bradycardia is associated with an increased incidence of atrial fibrillation, atrial pacing therapies for prevention of atrial fibrillation are another concept. Ongoing clinical trials evaluating the efficacy of pacing in patients with and without a primary pacemaker indication are currently under investigation. To date, data to which extent anatomical and electrophysiological characteristics of the atria influence the initiation and maintenance of atrial fibrillation are still missing. The myocardial adaptation to atrial fibrillation, the so-called "atrial remodeling", includes shortening of the atrial refractory period, slowing of atrial conduction, shortening of the atrial action potential, a progressive reduction of L-type calcium channel expression and microfibrosis of the myocardial tissue. New drug developments target atrial remodeling by modulating ion channel function and receptors of the angiotensin metabolism.

Action Potentials↗
PubMed2001

Usefulness of calcium scoring using electron beam computed tomography and noninvasive coronary angiography in patients with suspected coronary artery disease.

The aim of this study was to investigate the reliability of calcium scoring (CS) and electron beam computed tomographic angiography (EBCTA) as a noninvasive tool in the diagnosis of coronary artery disease (CAD): 93 consecutive patients (aged 59 +/- 9 years) with symptoms suspicious for CAD underwent CS. In 87 of these subjects, an additional EBCTA investigation was performed. Using receiver-operating characteristic curve analysis, we determined a calcium score cut point providing an overall sensitivity of 80% and a specificity of 72% in detecting patients with CAD. For clinical purposes the use of cut points is difficult. We therefore determined score ranges providing >80% specificity (high score range) and >85% sensitivity (low score range) and determined the scores between these ranges as equivocal borderline scores. Calculated on a per-segment basis in assessable proximal and midcoronary segments, the sensitivity for detecting coronary stenoses >50% was 78%, and the specificity was 93%. Thus, 32 of 44 patients with significant CAD and 24 of 49 patients without CAD were correctly classified. The combination of CS and EBCTA predicted CAD in 77% (72 of 93) of patients. No or low calcium scores provided high specificity for ruling out CAD. The addition of EBCTA in those patients improved sensitivity. In patients with high calcium scores, accuracy of EBCTA was not significantly different from CS alone (72% vs 83%), whereas in patients with borderline scores it was significantly superior (80% vs 58%, p <0.03). Thus, the complementary use of CS and EBCTA appears beneficial, particularly in patients with borderline scores, and could improve sensitivity in the low score range. In the presence of high scores, no major diagnostic gain from an additional EBCTA versus CS alone could be observed.

Calcinosis↗
PubMed2001

[Exclusion of coronary calcium with electron beam tomography: an effective filter before invasive diagnosis in symptomatic patients?].

Electron beam computed tomography (EBCT) is the most sensitive and accurate method of measuring coronary calcium which indicates coronary atherosclerosis. We performed a prospective study in 1764 symptomatic patients who were referred to our hospital for coronary angiography because of suspected coronary artery disease. In all of these patients cardiac catheterization and coronary calcium scanning was performed within 3.2 +/- 4 days. 454/1225 men (37.0%) and 165/539 women (30.6%) had significant coronary stenoses > or = 75%. Only two men (0.4%) and no single woman (0.0%) with stenoses > or = 75% and only 3/323 patients (0.9%) with moderate stenoses (50-75%) did not exhibit coronary calcium. Coronary angiography excluded stenoses in 822 patients. Of these patients 261 (29.4%) did not reveal coronary calcium. In younger patients (< 60 years) without stenosis exclusion of coronary calcium was a frequent finding: 31% of men and 55.8% of women were free of coronary calcium. Thus, exclusion of coronary calcium with electron beam tomography defines a substantial subgroup of patients who have an extremely low risk of significant coronary stenosis despite suspected coronary artery disease in history and non-invasive testing. Determination of coronary calcium might, therefore, be an effective filter before invasive angiography in selected groups of symptomatic patients.

Adult↗
PubMed2001

Correlation of coronary calcification and angiographically documented stenoses in patients with suspected coronary artery disease: results of 1,764 patients.

OBJECTIVES: This study correlated the electron beam computed tomographic (EBCT) calcium scores with the results of coronary angiography in symptomatic patients in order to assess its value to predict or exclude significant coronary artery disease (CAD). BACKGROUND: Electron beam computed tomography is a sensitive method to detect coronary calcium. However, it is unclear whether it may play a role as a filter before invasive procedures in symptomatic patients. METHODS: A total of 1,764 patients (1,225 men and 539 women) with suspected CAD from a single center were included in our study. All patients underwent calcium screening with EBCT (C150XP Imatron) and conventional coronary angiography. RESULTS: Fifty-six percent of men and 47% of women revealed significant coronary stenoses (> or =50%). Total exclusion of coronary calcium (14% of the study group) was associated with an extremely low probability of stenosis (<1%). With calcium scores > or =20th, > or =100th or > or =75th percentile of age groups, the sensitivity to detect stenoses decreased to 97%, 93% and 81%, respectively, in men and to 98%, 82% and 76%, respectively, in women. At the same time, the specificity increased up to 77% in men and women. There was a significant difference in coronary calcium between men and women in all age groups; however, receiver-operating characteristic curves indicated that the test can be performed with equal accuracy in all of these subgroups. CONCLUSIONS: Calcium screening with EBCT is a highly sensitive and moderately specific test to predict stenotic disease. Exclusion of coronary calcium defines a substantial subgroup of patients, albeit symptomatic, with a very low probability of significant stenoses.

Adult↗
PubMed2001

Pressure-guided nonsurgical myocardial reduction induced by small septal infarctions in hypertrophic obstructive cardiomyopathy.

OBJECTIVES: We sought to assess the safety and efficacy of pressure-guided nonsurgical myocardial reduction (NSMR) with the induction of small septal infarctions in patients with hypertrophic obstructive cardiomyopathy (HOCM). BACKGROUND: Nonsurgical myocardial reduction has been shown to decrease left ventricular outflow tract (LVOT) obstruction and to improve symptoms in patients with HOCM. Infarct sizes differ considerably among studies published so far. METHODS: In 50 patients, the LVOT gradient was invasively determined at the time of the intervention, four to six months (n = 49) and 12 to 18 months (n = 25) after NSMR. New York Heart Association functional class and quality of life were assessed by using a standard questionnaire. Exercise capacity was tested by spiro-ergometry. Left ventricular (LV) mass was determined by electron beam computed tomography. RESULTS: Small septal infarctions (mean creatine kinase value 413 +/- 193 U/l) resulted in a sustained decrease in LVOT gradients, from 80 +/- 33 to 18 +/- 17 mm Hg after four to six months (p < 0.001, n = 49) and to 17 +/- 15 mm Hg (p < 0.001, n = 25) after 12 to 18 months. Nonsurgical myocardial reduction was followed by a decrease in LV hypertrophy, which was associated with a sustained increase in exercise capacity, as well as improvement in quality of life. CONCLUSIONS: Pressure-guided NSMR inducing small septal infarctions was sufficient to result in a sustained decrease in LVOT obstruction and to improve symptoms. The incidence of complications, such as complete heart block with necessary permanent pacemaker implantation (<10%), seems to be diminished by minimizing the infarct size.

Aged↗
PubMed2001

Early reinitiation of atrial fibrillation following external electrical cardioversion in amiodarone-treated patients.

UNLABELLED: Early reinitiation of atrial fibrillation (ERAF) following external or internal electrical cardioversion is one of the factors determining unsuccessful electrical cardioversion. Prevention of ERAF has not been studied systematically in patients on amiodarone therapy. METHODS AND RESULTS: 22 patients had ERAF within 1 min after external electrical cardioversion of atrial fibrillation. 11 patients were on amiodarone therapy and 11 patients had no antiarrhythmic medication. The effect of atropine, post-shock atrial pacing and intravenous ajmaline on ERAF was consecutively tested in these patients. Administration of atropine before repeated defibrillation or post-shock atrial pacing prevented ERAF in 9 of the 11 patients (82%) on amiodarone therapy but in only 3 of 11 patients (27%) without amiodarone (p<0.05). In the remaining patients, intravenous ajmaline was effective in the suppression of ERAF in 5 patients without amiodarone and in 1 patient with amiodarone. The PP interval preceding the atrial premature beat reinitiating atrial fibrillation was nonsignificantly longer in amiodarone-treated patients (1127+/-419 ms) in comparison to patients without amiodarone (896+/-271ms). 27% of patients without amiodarone at the time of electrical cardioversion and 55% of patients with amiodarone remained in sinus rhythm during the follow-up of 29+/-14 and 30+/-14 months, respectively. CONCLUSIONS: ERAF in patients on amiodarone can be treated by atropine or atrial pacing to prevent bradycardia-dependent ERAF. ERAF in amiodarone-treated patients does not apparently predict late recurrence of atrial fibrillation on continued amiodarone therapy.

Adult↗
PubMed2001

Electroanatomical mapping for visualization of atrial activation in patients with incisional atrial tachycardias.

AIMS: Incisional atrial tachycardias in patients following surgery for congenital heart disease are based on complex structural abnormalities in these hearts. The aim of this study was to evaluate the use of the electroanatomical mapping system, CARTO, in consecutive patients with different forms of incisional atrial tachycardia. METHODS AND RESULTS: The electroanatomical mapping system combines electrophysiological and spatial information and allows visualization of atrial activation in a three-dimensional anatomical reconstruction of the atria. Electroanatomical mapping of right atrial activation was performed in 10 patients after surgery for congenital heart disease, surgery for Wolff-Parkinson-White syndrome, or heart transplantation presenting with 13 incisional atrial tachycardias. The three-dimensional mapping allowed a rapid distinction between focal (n=3) and reentrant mechanisms (n=10) and visualization of the activation wavefronts along anatomical and surgically created barriers. Electroanatomical activation maps (mean right atrial activation time 213+/-107 ms) were constructed with 89+/-60 catheter positions during an average mapping time of 48+/-33 min. Reentrant tachycardias propagating through the tricuspid annulus-vena cava inferior isthmus (n=6) or along periatriotomy loops (n=4) were identified in eight patients. Ectopic atrial foci near surgical scars could be localized in three patients. Catheter ablation by creation of a lesion in a critical isthmus of conduction or by targeting the arrhythmogenic focus eliminated 11 of 13 incisional atrial tachycardias. CONCLUSION: Visualization of atrial activation in a three-dimensional reconstruction of the right atrium using the electroanatomical mapping system CARTO facilitates understanding of the mechanism and defines the reentrant circuits of incisional atrial tachycardias. This new method may improve the success rate of electrophysiologically guided and anatomically guided catheter ablation of incisional atrial tachycardias.

Adult↗
PubMed2000

Influence of stent design on 1-year outcome after coronary stent placement: a randomized comparison of five stent types in 1,147 unselected patients.

The objective of this randomized trial was to assess whether differences in stent design are translated in different clinical outcomes in patients undergoing coronary stent placement. This multicenter randomized trial included 1,147 patients who were randomly assigned to receive one of five types of stainless steel stents: Inflow, MULTI-LINK, NIR, Palmaz-Schatz, and PURA-A stent. Primary endpoint of the study was event-free survival at 1 year. Event-free survival at 1 year was significantly different between the groups (P = 0.014), ranging from 69.4% to 82.4%. Similarly, freedom from myocardial infarction was also significantly different (P = 0.022), with values between 88.2% and 95.2%. Diameter stenosis at 6 months varied from 38.1% +/- 25.0% to 45.6% +/- 27.7% (P = 0. 046), late lumen loss ranged from 1.01 +/- 0.70 mm to 1.20 +/- 0.82 mm (P = 0.085), and the incidence of restenosis varied between 25.3% and 35.9% (P = 0.145). Thus, stent design has a significant impact on the long-term results after coronary stent placement.

Aged↗
PubMed2000

[Diagnostic imaging in cardiac diagnosis].

PURPOSE: Cardiac imaging includes determination of the size and structure of the cardiac chambers, valves, great vessels and the coronary arteries, chamber and valvular function, myocardial perfusion, viability and metabolism. MATERIAL AND METHODS: Chest roentgenography, angiography, echocardiography and nuclear imaging are commonly used but computed tomography and magnetic resonance imaging also offer a promising potential. RESULTS: Coronary angiography is the gold standard in assessing coronary anatomy. Fast CT technologies such as electron-beam and multi-low-CT are promising non-invasive imaging modalities in the assessment of coronary artery disease. With intravascular ultrasound early stages of coronary atherosclerosis can be detected. For the assessment of myocardial perfusion and viability as well as cardiac function, scintigraphic methods are widely accepted. However, MRI methods have also reached a high degree of accuracy. Evaluation of chamber and valvular function is, due to its wide availability, the field of echocardiography. CONCLUSIONS: In clinical routine chest roentgenography, angiography, echocardiography and nuclear imaging are well established. The value of computed tomography and magnetic resonance imaging in the evaluation of coronary artery disease, myocardial perfusion, viability and metabolism is yet to be defined.

Coronary Disease↗
PubMed2000

[Variable late potentials in long-term ECG of the post-infarct patient at risk for ventricular fibrillation].

BACKGROUND: Ventricular late potentials are found more readily in post-infarction patients who had sustained ventricular tachycardia than in those who survived ventricular fibrillation. Hypothetically, a daytime variability of late potentials might be responsible for this finding. METHOD: Therefore a conventional late potential analysis only performed once a day was compared to a late potential analysis in time and frequency domain repeatedly performed every hour in the Holter-ECG of 160 post-infarction patients (50 patients (= VT-group) with documented, sustained ventricular tachycardia (cycle-length > 230 ms), 50 patients (= VF-group) who survived, documented ventricular fibrillation and 60 patient, without ventricular arrhythmias (= O VT/VF-group)). RESULTS: The conventional analysis showed late potentials in time domain in 72% of the patients in the VT-group, in 40% of patients in the VF-group and in 20% of the patients in the O VT/VF-group. The Holter-ECG showed late potentials to be permanently present in frequency domain in 66% of the patients in the VT-group, in only 6% in the patients in the VF-group and in no patient in the O VT/VF-group. However, in at least one analysis we detected late potentials in 84% of patients of the VF-group, in 90% of patients in the VT-group and in 18% of patients in the O VT/VF-group. Transiently detectable late potentials in patients of the VF-group were predominantly seen at heart rate accelerations in the morning hours, ST-segment shifts or transitory decreased heart rate variability. CONCLUSIONS: Post-infarction patients with sustained ventricular tachycardia predominantly have constantly detectable late potentials over 24 hours. In these patients conventional late potential is successful for post-infarction risk stratification at any time of the day. However, in post-infarction patients who survived ventricular fibrillation, late potentials are found to be transitory and only detectable by Holter-ECG. Thus, late potential analysis performed in the Holter-ECG might improve post-infarction risk stratification in patients prone to sudden cardiac death.

Aged↗
PubMed2000

Selective pressure-regulated retroinfusion of coronary veins as an alternative access of ischemic myocardium: implications for myocardial protection, myocardial gene transfer and angiogenesis.

There is renewed interest in the coronary venous system as an alternative access to ischemic myocardium. Selective pressure-regulated retroinfusion is a catheter-based approach which has been shown to increase the efficacy of retrograde oxygen delivery and drugs in experimental and clinical studies. Selective pressure-regulated retroinfusion may also target retrograde delivery of angiogenic growth factors and gene vectors to ischemic myocardium.

Angiogenesis Inducing Agents↗
PubMed2000

Non-invasive coronary bypass graft imaging after multivessel revascularisation.

Non-invasive imaging techniques for the detection of graft patency after multivessel coronary revascularisation may be useful for follow-up after surgery. Forty consecutive asymptomatic patients (38 men, age 59.9+/-1.3 years) who had undergone coronary bypass surgery with at least three grafts were examined by spiral computed tomography or magnetic resonance angiography 24.9+/-0.3 months after surgery, using conventional angiography as reference. In total, 133 grafts (37 internal mammary artery, 96 venous grafts) were analysed. Spiral computed tomography studies were performed with a subsecond scanner; for magnetic resonance angiography, a three-dimensional contrast-enhanced gradient echo technique with ultrashort echo time during breath holding was used. For spiral computed tomography, sensitivities were 76% (internal mammary artery) and 100% (venous graft). This was compared with 100% (internal mammary artery) and 92% (venous graft) assessed by magnetic resonance angiography (P=ns). The positive predictive values were 100% for internal mammary artery and venous graft (spiral computed tomography) and 100% (internal mammary artery), 92% for venous grafts studied by magnetic resonance angiography (P=ns). Both subsecond spiral computed tomography and contrast-enhanced magnetic resonance angiography are highly accurate and relatively non-invasive approaches of assessing coronary graft patency after multivessel revascularisation and have potential for follow-up assessment in the long term.

Contrast Media↗
PubMed2000

Amiodarone: maximising survival benefit with empiric or guided therapy.

Review of available data suggests that serial drug testing in patients with a history of sustained ventricular tachyarrhythmias using various antiarrhythmic drugs including amiodarone is able to identify subgroups with favorable and unfavorable outcome (patient groups with suppression vs. no suppression of inducibility of VT/VF). These results more likely reflect patient selection rather than drug effects, thus limiting the role of electrophysiologically guided antiarrhythmic therapy to actively modify outcome. All major and actual antiarrhythmic drug trials including an amiodarone arm, have chosen to deliver this drug empirically in both patients with asymptomatic as well as severely symptomatic life-threatening sustained ventricular tachyarrhythmias instead of a guided approach. The empiric approach is therefore adequate until new valid data comparing the empiric with the guidedor the invasive with the non invasiveapproach tell us otherwise.

Amiodarone↗