[More information--less pain. Procedure in pain following amputation of limbs. Brachial plexus injury and nerve root avulsion. Interview by Susanne Kammerer].
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Amputation, Surgical↗
Biomedical subjects
R Haberl
Publications and source records attributed to R Haberl.
Detection and quantification of coronary artery calcification with electron-beam and conventional CT.
To identify patients with increased risk of having coronary artery disease (CAD), electron-beam computed tomography (EBCT) was used for years for quantifying calcifications of the coronary arteries. The first direct comparison between EBCT and conventional CT was performed to determine the reliability of widely available conventional CT for the assessment of the coronary calcium score. Fifty male patients with suspected CAD were investigated with both modalities, EBCT and conventional 500-ms non-spiral partial scan CT. Scoring of the coronary calcification was performed according to the Agatston method. Forty-two of these patients underwent coronary angiography for the assessment of significant luminal narrowing. The correlation coefficient of the score values of both modalities was highly significant (r = 0.982, p < 0.001). The variability between the two modalities was 42%. Mean calcium score in patients with significant coronary luminal narrowing (n = 37) was 1104 +/- 1089 with EBCT and 1229 +/- 1327 with conventional CT. In patients without luminal narrowing (n = 5) mean calcium score was 73 +/- 57 with EBCT and 26 +/- 35 with conventional CT. Although images of the heart from conventional CT may suffer from cardiac motion artifacts, conventional CT has the potential to identify patients with CAD with accuracy similar to EBCT.
Artifacts↗
Identification of ventricular late potentials in the surface electrocardiogram during atrial, atrioventricular sequential, or single-chamber ventricular pacing.
Sudden cardiac death occurs in up to 30% of patients with cardiac pacemakers, caused by ventricular arrhythmias, but in these patients noninvasive risk stratification with Holter, exercise, or standard signal-averaged electrocardiogram is limited. This study investigated whether late potential analysis during cardiac pacing is applicable. In 50 postinfarction patients with documented sustained ventricular tachycardia (VT) and in 50 patients without VT, late potential analysis during sinus rhythm was compared with the corresponding patient's analysis during temporary pacing. During sinus rhythm late potentials were seen in 48 of 50 patients with VT and in 2 of 50 patients without VT. No significant changes were observed during atrial pacing. Modified QRS alignment for signal averaging, QRS endpoint definition, and adjusted cutoff values for abnormality in time and frequency domain analysis allowed retrieval of all late potentials observed during sinus rhythm even in ventricular-paced beats and retrograde conduction. By application of an adjusted analysis to 100 selected patients with permanent pacemakers (50 patients with a history of VT, 50 patients without VT) late potentials were detectable in 44 of 50 patients with VT and in 4 of 50 without VT (sensitivity 88%, specificity 92%). Thus, considering that varying pacing modes, ventricular-paced beats, and retrograde conduction do require modifications of standard late potential analysis, this is an applicable mode for noninvasive risk stratification even in patients with cardiac pacemakers.
Adult↗
Risk stratification following myocardial infarction in the thrombolytic era: a two-step strategy using noninvasive and invasive methods.
OBJECTIVES: We prospectively performed a two-step risk assessment in patients in the early phase after acute myocardial infarction (MI). BACKGROUND: Noninvasive methods like Holter electrocardiographic monitoring (HM) and determination of the left ventricular ejection fraction (EF) as well as the invasive technique of programmed ventricular stimulation (PVS) have been used to identify patients in the late phase after MI as candidates for prophylactic implantation of a cardioverter/defibrillator. However, it is unclear whether these results can be transferred to patients following acute MI. METHODS: A series of 657 patients with acute MI (< or = 75 years) underwent HM and EF. If one of the two methods yielded abnormal findings (HM > or = 20 ventricular ectopic beats/h/> or =10 ventricular pairs/day/ventricular tachycardia; EF < or = 40%), PVS was done (abnormal PVS: induction of monomorphic ventricular tachycardia, duration >10 s, cycle length > or = 230 ms). RESULTS: Of 657 patients, 304 (46%) had either an abnormal HM or EF. The PVS performed in 146 of 304 patients was abnormal in 22. During a mean follow-up of 37 months, there were 106 (16%) deaths, being sudden in 24 (3.6%), nonsudden cardiac in 45 (6.8%). The incidence of arrhythmic events (sudden cardiac death, symptomatic ventricular tachycardia, cardiac arrest) was 18% (4/22) with an abnormal PVS and only 4% (5/124) with a normal PVS (odds ratio 4.0, p=0.032). CONCLUSIONS: The rate of arrhythmic events is low in post-MI patients in the 1990s. Nevertheless, a two-step risk stratification is helpful in selecting candidates for a defibrillator trial aiming at primary prevention of sudden cardiac death after MI.
Combined Modality Therapy↗
Functional changes of ventricular late potentials by provocation with increase of heart rate. Evaluation during atrial pacing.
BACKGROUND: Standard methods fail to reveal late potentials in 20 to 30% of patients with ventricular arrhythmias after myocardial infarction. However, these patients may develop transient delayed ventricular activation during increases in heart rate. METHODS AND RESULTS: Atrial pacing was performed, at the rates of 100 min-1 and 120 min-1, in 50 patients after myocardial infarction. Twenty-six patients had a history of documented, sustained ventricular tachycardia, 12 had a history of ventricular fibrillation and 12 no history of ventricular arrhythmias. The low-noise surface electrocardiogram was analysed before and during atrial pacing in the time and frequency domains. Fifteen of 26 patients with ventricular tachycardia, four of 12 with ventricular fibrillation and three of 12 without ventricular arrhythmias experienced late potentials during sinus rhythm. Atrial pacing led to a shift of 26 +/- 15 ms of preexistent late potentials into the ST segment, this being greater in patients with anterior infarctions and to an increase in magnitude in patients with inferior infarctions. In patients without late potentials during sinus rhythm, atrial pacing provoked late potentials in eight of 11 patients with ventricular tachycardia, in four of eight patients with ventricular fibrillation and in one of nine patients without ventricular arrhythmias. Low amplitude signals (LAS) were increased in patients after inferior and filtered QRS in patients after anterior infarction. In 10 patients without cardiac disease no late potentials were detectable in the time and frequency domain either at rest or during increased heart rate. CONCLUSIONS: Increase in heart rate may unmask late potentials in patients prone to malignant ventricular arrhythmias. Therefore, functional late potential analysis with non-invasive clinical stress tests, i.e. exercise tests, should be performed only with an adequate rate response. This might identify patients at risk of malignant ventricular arrhythmias otherwise not identified with conventional late potential analysis.
Arrhythmias, Cardiac↗
Circadian variability of late potential analysis in Holter electrocardiograms.
Appearance of ventricular tachycardia, ventricular fibrillation, and sudden cardiac death has diurnal variations. We retrospectively studied, using digital Holter electrocardiogram, whether a time course in the appearance of late potentials may be associated with malignant ventricular arrhythmias. The 24-hour recordings in 200 patients after myocardial infarction (50 patients with documented, sustained, monomorphic and reproducibly inducible ventricular tachycardia (< 270/min) (group I), 50 patients resuscitated from ventricular fibrillation (group II), and 100 patients without ventricular arrhythmias (group III) were divided into 24 segments, 60 minutes each. Late potential analysis was performed using the Simson method in the time domain in each segment and compared to a conventional short-term registration. Late potential analysis in conventional short-term recordings during arbitrarily chosen daytimes revealed late potentials in 80% of patients in group I, 38% of patients in group II, and in 16% of patients without ventricular arrhythmias. In at least one 60-minute segment late potentials were found in group I in 92%, in group II in 88% (P < 0.05 vs conventional analysis), and in group III in 19%. Interestingly, in patients with a history of ventricular fibrillation late potentials appeared significantly more often during morning hours (6-12 AM: 82% vs 26% at 12 AM-6 PM, 30% at 6 PM-12 PM, and 42% at 12 PM-6 AM, P < 0.05), especially during phases with heart rate accelerations. Late potential analysis for risk stratification in conventional short-term recordings is feasible for patients prone to ventricular tachycardia, but patients prone to ventricular fibrillation would be more effectively stratified using 24-hour registrations with detection of circadian variations of late potential appearance.
Aged↗
Ischemia-induced changes of the signal-averaged electrocardiogram: experimental investigation during percutaneous transluminal coronary angioplasty balloon-occluded coronary artery.
INTRODUCTION: The influence of myocardial ischemia on the detection of an arrhythmogenic substrate with the signal-averaged ECG is unclear. METHODS AND RESULTS: In 80 patients with single vessel coronary artery disease and a critical stenosis of the left anterior descending vessel selected after coronary angiography in whom percutaneous transluminal coronary angioplasty (PTCA) was planned, we retrospectively investigated the signal-averaged ECGs in the time domain before, during, and after occlusion of the coronary artery by the PTCA balloon. Forty patients were resuscitated from ventricular fibrillation (VF group), and 40 patients had no ventricular arrhythmia (non-VF group). Late potentials were seen at rest in 26 of 40 patients in the VF group. During ischemia, the duration of the filtered QRS complex and the duration of low-amplitude signals < 40 microV increased significantly. In another 14 patients in the VF group, late potentials were observed only during ischemia. In 4 of 26 patients in the VF group without prior infarction but with severe ischemia present at rest, successful PTCA eliminated preexistent late potentials. In the non-VF group, one patient had late potentials present at rest. In two patients with prior infarction, late potentials were provokable only during transmural ischemia. CONCLUSION: Myocardial ischemia is able to modify detection of an arrhythmogenic substrate with the signal-averaged ECG.
Aged↗
[Drug therapy and prevention of recurrence of supraventricular tachyarrhythmias].
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Anti-Arrhythmia Agents↗
[Virtual and three-dimensional bronchoscopy with spiral and electron beam computed tomography].
PURPOSE: To compare spiral computed tomography (CT) and electron-beam CT (EBT) for 3D and virtual CT-bronchoscopy. MATERIALS AND METHODS: 17 patients with various disorders of the tracheobronchial system were examined using fiberoptic bronchoscopy, spiral CT and EBT. 3D images were reconstructed from CT data sets using automated segmentation based on volume-growing methods. Surface-rendered, volume-rendered, and hybrid reconstructions were visualized in real time using a data helmet. RESULTS: All data sets could be processed to high-quality three-dimensional (3D) and virtual reconstructions. The reduction of motion artifacts due to shorter scan times made EBT data sets better suited for automated segmentation and less susceptible to motion artifacts. 3D and virtual reconstructions did not increase the diagnostic sensitivity of CT compared to axial reconstructions alone. CONCLUSIONS: Shorter scan times of CT imaging yield higher-quality 3D and virtual reconstructions. Modern reconstruction techniques are valuable visualization tools for select indications and are the prerequisite for future developments in computer-aided medicine.
Bronchial Neoplasms↗
[Significance of calcium detection with electron-beam tomography in coronary disease].
PURPOSE: Coronary calcium is a powerful indicator of arteriosclerosis and can be detected very precisely with electron beam tomography. The method can be applied in patients with known coronary artery disease or in asymptomatic patients at risk of arteriosclerotic disease. METHODS: The standard protocol of EBT consists of 30 to 40 slices of 3-mm thickness with a scan time of 100 ms, no overlap. No contrast medium is needed. The total scan can be performed within one breathhold. The calcium score is calculated as described by Agatston. Radiation exposure amounts to 0.8 mSv per total screen. We used spiral CT with and without ECG trigger as an alternative. RESULTS: At the University of Munich we performed an EBT scan of the heart in 1100 patients within the last year. In 567 patients coronary angiography was performed also (+/- 3 days). Confirming previous reports in the literature, we found a correlation of the calcium score with the age and gender of the patients. Severe coronary artery disease (stenoses > or = 75%) was associated with significantly more calcium than less severe CAD. The calcium score did not discriminate between one-, two- and three-vessel disease. The site of calcification does not correlate with the localization of stenoses. Thirty-three percent of the patients with significant coronary artery disease showed a normal age-adjusted calcium score; a total of 8.1% of patients with severe stenoses did not reveal any coronary calcification (score = 0). With asymptomatic patients there are only a few studies available. Soft plaques cannot be detected with EBT, but in most patients soft plaques occur together with hard plaques. Our results show that spiral CT of the newest generation may also be used for calcium screening. There was an excellent correlation of the calcium scores of EBT and spiral CT at all levels of calcification. DISCUSSION: Coronary calcium is a sensitive marker of coronary artery disease. In the clinical setting EBT is indicated in patients with known coronary artery disease (to evaluate prognosis), in patients who are unable to perform a stress test, and in patients with atypical chest pain. However, lack of calcification may be associated with severe stenoses in a minority of patients. The clinical value in asymptomatic patients needs to be defined: randomized studies are necessary. We see a possible indication in patients with known risk factors, in whom primary preventive strategies could be performed more selectively and cost-effectively.
Adolescent↗
[Methods of quantification of coronary artery calcifications with electron-beam and conventional computed tomography].
PURPOSE: To compare electron beam CT (EBCT) und prospectively ECG gated conventional CT for the detection and quantification of coronary artery calcifications. METHODS: 42 patients (mean age 62.8 +/- 8.8 years) were scanned, both with EBCT and ECG gated sequential CT. For quantification, the traditional "total calcium score" (TCS) according to the Agatson method as well as the "volumetric calcium score" (VCS) as determined with a stand-alone workstation (NetraMD) was calculated for both modalities. RESULTS: There was close correlation between EBCT and conventional CT, both for TCS (r = 0.984) as well as for VCS (r = 0.986) score values. The median difference was 17% for TCS and 13% for VCS. The difference between the two modalities was not statistically significant (p = 0.44). CONCLUSION: EBCT and prospectively ECG triggered conventional CT are equivalent for the quantification of coronary artery calcifications. The extent of calcifications can be established with both modalities using either TCS or VCS score values.
Age Factors↗
[Significance of electron-beam tomography in the evaluation of the patency of aortocoronary bypasses].
PURPOSE: Electron beam tomography (EBT) permits acquisition of images with high spatial and temporal resolution. The value of EBT and other imaging modalities for the depiction of patent coronary artery bypass grafts (ACVB, IMA) are compared to coronary angiography and an overview of current results is given. MATERIAL AND METHODS: Graft patency can be evaluated with indirect methods stress, such as echocardiography, radionuclide ventriculography, myocardial scintigraphy, positron-emission tomography (PET) and direct imaging modalities, such as Doppler/2D echocardiography, EBT, spiral computed tomography (SCT) and magnetic resonance angiography (MRA). RESULTS: With indirect methods graft patency can be evaluated with sensitivity of 64-100% and specificity of 73-100%. EBT and SCT are equivalent in sensitivity (= 94%) in the assessment of open venous grafts and specificity is up to 100%, but EBT is superior in the diagnosis of patent IMA grafts (sensitivity 100% vs 89%). Visualization of high-grade venous bypass stenosis seems possible with EBT. MRA with gradient echo technique is highly accurate in the assessment of patent venous grafts (sensitivity 77-93%) but has limited value in the evaluation of IMAs (sensitivity = 53%). Promising are ultrafast 3D-MRA methods which permit high accuracy (sensitivity = 94-96%) in assessing venous and arterial grafts. DISCUSSION: Indirect imaging methods cannot differentiate between an occluded bypass, progression of coronary artery disease and myocardial infarction. EBT and SCT are equivalent in the diagnosis of open and occluded venous grafts, but EBT is superior in the assessment of patent IMA grafts. Visualization of high-grade venous bypass stenosis seems possible with EBT. MRA techniques, especially ultrafast 3D-MR methods, are highly accurate in the assessment of patent venous and arterial grafts but are still limited to scientific research.
Coronary Artery Bypass↗
[Functional imaging of the heart with electron-beam computed tomography].
PURPOSE: Electron-beam computed tomography (EBCT) enables examinations with a very short acquisition time of 50 ms and thus permits cardiac imaging without motion artifacts. Utilizing eight detector rings simultaneous image acquisition in up to eight levels and complete imaging of the whole heart is possible. In studies, functional imaging with EBCT was compared to our angiocardiography, echocardiography, radionuclide, ventriculography and magnetic resonance tomography. MATERIALS AND METHODS: ECG-triggered long- and short-axis cine studies were performed with the Imatron C-150 Evolution, acquiring 160 and 156 images at 8 and 12 levels. After manual tracing of epicardial and endocardial borders, ventricular size, ejection fraction, wall-thickening and myocardial mass were calculated. RESULTS: A very high correlation between EBCT and direct determination of right and left ventricle (r = 0.98 and r = 0.99) was demonstrated. Compared to echocardiography, angiocardiography and radionuclide ventriculography, assessment of ventricular function was more precise and more reliable. DISCUSSION: EBCT allows the exact and reliable determination of left and right ventricular function. Also precise assessment of myocardial mass is possible. However, the high radiation exposure and diagnostic effort have to be considered.
Angiocardiography↗
[Diagnosis of pulmonary embolism with spiral and electron-beam CT].
PURPOSE: To compare spiral (SCT) and electron-beam CT (EBT) for the diagnosis of pulmonary embolism (PE). MATERIALS AND METHODS: From June 1997 to June 1998 188 patients with suspected acute or chronic thromboembolism of the pulmonary arteries were examined. A total of 108 patients were scanned using SCT and 80 patients using EBT. On each scanner two different scan protocols were evaluated. RESULTS: PE was diagnosed in 38 patients using EBT and in 49 patients using SCT. Especially with EBT, isolated peripheral emboli could be confidently diagnosed. When EBT and SCT were compared for the analysis of peripheral pulmonary arteries, some paracardiac segmental and subsegmental vessels were significantly better analyzable with EB. Additional or diseases other than PE were diagnosed in 112 patients. Other diagnoses included bronchial carcinoma and aortic dissection. CONCLUSIONS: Advanced CT scanning techniques allow the highly accurate diagnosis of central and peripheral PE. Other potentially life-threatening underlying diseases are also readily recognized.
Aortic Dissection↗
[Analysis of functional changes in ventricular late potentials for risk assessment of ventricular tachycardias after myocardial infarct].
BACKGROUND: Electrophysiological abnormalities during ischaemia and increased heart rate may influence the detection of ventricular late potentials in the surface electrocardiogram. Whether the analysis of functional changes adds information to the risk stratification of patients prone to ventricular tachycardia is unclear. METHODS: We therefore retrospectively investigated 100 selected patients (25 with documented, sustained ventricular tachycardia (< 230/min) ( = VT group), 25 resuscitated from ventricular fibrillation (VF group) and 50 without ventricular arrhythmias (phi VT/VF group)) in the chronic phase after myocardial infarction. Late potential analysis was performed at rest, during atrial pacing at a rate of 100/min and 120/min (n = 60), during and after occlusion of the coronary artery for coronary angioplasty (PTCA) (n = 70), and immediately after maximum exercise using selective signal averaging. RESULTS: At rest in 72% of patients in the VT group, in 32% of the VF group, and in 6% of the phi VT/VF group late potentials could be found. During atrial pacing in 80% of patients in the VT group, in 72% of the VF group, and in 10% of the patients in the phi VT/VF group and during ischaemia because of occluded coronary artery in 86% of patients in and the VT group, 70% of the VF group, and in 20% of the patients of the phi VT/VF group late potentials were present. Immediately after maximum exercise which let both ischaemia and increased heart rate, late potentials were detectable in 92% of patients in the VT group, 80% of the VF group, and in 14% of patients in the phi VT/VF group. Similar results could be achieved by using the Holter-ECG after exact correction of recorder tape speed variations. 62% of patients with only by ischaemia, increased heart rate or exercise provokable late potentials and all patients with preexistent not by PTCA extinguished late potentials developed recurrent ventricular tachycardias during the one year follow-up period. Patients without late potentials (n = 50) and patients with preexistent by PTCA extinguished late potentials (n = 11) had no recurrent ventricular tachycardias. Cycle length of recurrent and clinical tachycardia in patients with preexistent not by PTCA extinguished late potentials (n = 18) were significantly longer than in patients with only provokable late potentials (n = 21). CONCLUSIONS: Analysis of functional changes of ventricular late potentials with exercise or in Holter ECG recordings promises considerable improvement of postinfarction risk stratification especially in patients prone to ventricular fibrillation.
Adult↗
T wave spectral variance: A new method to determine inhomogeneous repolarization by T wave beat-to-beat variability in patients prone to ventricular arrhythmias.
Inhomogeneous repolarization is considered to be associated with increased risk of ventricular arrhythmias, but exact determination of the end of the T wave is difficult, and a single measurement of the QTc interval may be insufficient for risk stratification. A new algorithm was therefore developed to determine the beat-to-beat variability of the T wave in Holter electrocardiographic recordings. This algorithm, termed T Wave Spectral Variance (TWSV) uses the two-dimensional fast Fourier transform to determine the beat-to-beat variability of the T wave in Hotter ECG recordings. The two-dimensional fast Fourier transform was calculated by use of a data matrix with 1,024 consecutive single beats (first dimension) and a 200-ms segment centered on the T wave (second dimension). The power spectra of the 2D-FFT revealed the frequency content of the T wave in the first dimension and the periodicity of these frequencies in cycles per beat in the second dimension. A TWSV index of periodicity was calculated by dividing total spectral energy by spectral energy at 0 cycles per beat. A TWSV index of 0 means a constant T wave from beat to beat; a TWSV index of 1 means a completely irregular T wave. Of the 200 patients investigated, all of whom had had myocardial infarctions, 50 had documented sustained ventricular tachycardia (VT) (<230 beats/min) (group 1), 50 had ventricular fibrillation (VF) (group 2), and 100 were without VT or VF (group 3); 10 normal subjects were also investigated. The visually determined QTc was 442 +/- 62 ms in group 1, 402 +/- 13 ms in group 2, 411 +/- 26 ms in group 3, and 398 +/- 43 ms in normal subjects (differences not significant). The TWSV index was 0.95 +/- 0.14 in group 1, 0.90 +/- 0.16 in group 2, and 0.64 +/- 0.24 in group 3; it showed a highly constant T wave in normal subjects (0.52 +/- 0.23). Differences between patients with VT and VF as against patients without VT or VF were significant (P < .05), whereas no statistical differences between patients with VT and VF could be found. Thus, TWSV, a new method to assess beat-to-beat variability of the T wave, revealed increased heterogeneity of repolarization in patients prone to both VT and VF after myocardial infarction, whereas a single QTc interval measurement showed no significant differences.
Algorithms↗
Can ECG spectral analysis improve the noninvasive surveillance of acute rejection?
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Acute Disease↗
Single-beat analysis of ventricular late potentials in the surface electrocardiogram using the spectrotemporal pattern recognition algorithm in patients with coronary artery disease.
AIMS: Post-infarction risk stratification can be ascertained from beat-to-beat variations in ventricular late potentials. However, gaining such information by conventional late potential analysis using signal averaging is still not possible. METHODS: We therefore developed the spectrotemporal pattern recognition algorithm in order to detect beat-to-beat variations in late potentials. Based on the spectrotemporal pattern recognition algorithm two-dimensional correlation function, the typical spectral pattern of late potentials can be identified in spectrotemporal maps of single beats, even in the presence of noise. RESULTS: Surface electrocardiograms of 385 patients after myocardial infarction (85 with documented sustained ventricular tachycardia (group 1), 100 with fast, polymorphic ventricular tachycardia (> 270 cycles.min-1) or primary ventricular fibrillation (group 2), 200 without ventricular arrhythmias (group 3) and 45 healthy volunteers (group 4), were analysed. The spectrotemporal pattern recognition algorithm detected late potentials in single beats in 89% of group 1 patients, in 79% of group 2, in 22% of group 3 and in 4% of normals. The spectrotemporal pattern recognition algorithm measured late potential frequency and extension of late potentials into the ST segment, which was significantly different between groups 1 and 2. Beat-to-beat variations in late potentials, with respect to frequency and extension into the ST segment, were markedly higher in patients with a history of primary ventricular fibrillation. CONCLUSION: Single-beat analysis using the spectrotemporal pattern recognition algorithm may improve risk stratification of patients after myocardial infarction, and provides information on patients prone to ventricular fibrillation.
Action Potentials↗