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Biomedical subjects

G Breithardt

Publications and source records attributed to G Breithardt.

At least 199 records · Page 11Linked to original sources
PubMed1997

Progressive heterogeneity of myocardial perfusion in heart transplant recipients detected by thallium-201 myocardial SPECT.

UNLABELLED: Progressive graft atherosclerosis is a serious complication in long-term survivors after heart transplantation. Coronary angiography is insensitive with regard to the early and characteristic alterations. We evaluated the progression of these abnormalities and the influence of former rejection episodes. METHODS: Early after transplantation, 43 patients (34 men, mean age 53.7 +/- 10.7 yr) underwent stress and redistribution 201Tl myocardial SPECT after treadmill exercise. Twenty patients were followed-up to the second postoperative year, and 13 patients to the third postoperative year. Thallium-201 distribution and kinetic abnormalities were documented in a scheme enclosing 20 myocardial segments. Additionally, a score was developed that measured the degree of inhomogeneity of 201Tl distribution and the severity of perfusion defects, respectively. RESULTS: Regarding scintigraphy, pathologic results could be found in 40% of segments (redistribution, 25%; reverse redistribution, 30%; persistent defects, 49%). Score values in heart transplant recipients differed significantly from normal controls (p < 0.001) and were comparable to patients with single vessel disease of their native hearts. Thallium-201 inhomogeneity in recipients after treatable rejection episodes did not differ from results in recipients without any biopsy-proven rejection. The follow-up of cardiac transplant patients revealed a significant increase of score values up to the third year after transplantation (p < 0.02), despite reproducible normal angiography. There was no direct correlation between score values and IVUS results, although there was a parallel trend in 10 of 12 follow-ups. CONCLUSION: Despite normal coronary angiography, 201Tl myocardial SPECT frequently revealed pathologic results in heart transplant recipients. Scintigraphic results did not correlate with intimal thickening of epicardial coronary arteries accessible to intravascular ultrasonography in the early phase after transplantation. The presented score of inhomogeneity might reveal progressive disease possibly caused by small vessel alterations.

Case-Control Studies↗
PubMed1997

Long-term left ventricular assist device support: a novel pump rate challenge exercise protocol to monitor native left ventricular function.

A novel, hemodynamically guided exercise protocol with two different left ventricular assist device settings in two long-term recipients is presented. This protocol allows for quantitation of the contribution of the native left ventricle to total cardiac output. It facilitates estimation of the risk associated with device dysfunction, as well as prediction of left ventricular recovery and the potential for weaning.

Adult↗
PubMed1996

Interleukin-6 correlates with hemodynamic impairment during dobutamine administration in chronic heart failure.

Proinflammatory cytokines have been implicated in the pathophysiology of chronic heart failure. We determined mixed venous levels of interleukin-6 (IL6) in 18 heart transplant candidates before, 1, 4, and 24 h after initiation of dobutamine infusion (3 micrograms/kg/min) during hemodynamic evaluation. During the first 4 h of dobutamine, systemic vascular resistance decreased (1358 to 1024 dyn x s x cm-5, P = 0.01) while cardiac index (2.3 to 2.9 l/min/m2, P = 0.008) increased. Both returned to baseline after 24 h. IL6 was elevated at baseline compared to age-matched controls (1.5 (0/4.3) vs. 0 (0/0.5) P = 0.003). There was an increase in IL6 from 1.5 (0/4.3) to 3.6 (0.3/5.3) pg/ml after 24 h (P = 0.04). We found higher IL6 levels in the sicker half of patients as defined by pulmonary capillary wedge pressure > 24 mmHg (P = 0.005), mean pulmonary arterial pressure > or = 35 mmHg (P = 0.01), right atrial pressure > 13 mmHg (P = 0.02), and heart rate > or = 87/min (P = 0.02) as well as mean arterial pressure < 82 mmHg (P = 0.005). In conclusion, in this pilot study IL6 correlates with the severity of chronic heart failure during low dose dobutamine infusion.

Adult↗
PubMed1996

Can Tl-201 myocardial SPECT abnormalities in orthotopic heart recipients be explained by coronary vessel wall alterations assessed by intravascular ultrasound?

UNLABELLED: The aim of this study was to compare findings on coronary intravascular ultrasound and thallium-201 SPECT in patients following orthotopic heart transplantation. BACKGROUND: No data are available on whether pathological thallium scintigraphic findings in heart recipients are based on coronary vessel wall alterations identifiable by intravascular ultrasound. METHODS: 29 patients (mean age: 50.9 +/- 11.5 years; male n = 23) were investigated by means of intravascular ultrasound of selected coronary segments and thallium-201 myocardial SPECT. Patients were investigated 11.6 +/- 5.4 weeks post transplantation, a subgroup of 13 patients was re-investigated 70.2 +/- 18.4 weeks following transplantation. A total of 214 cross-sectional areas of the left coronary artery were examined using a 3.5 French intravascular ultrasound catheter to measure intimal index and the circumferential extension of a three-layer appearance of the vessel wall. Shortly after catheterisation, an ergometric stress-test was performed to examine all recipients by means of thallium-201 SPECT. In each patient, 20 segments of the left ventricle were evaluated using a score system of differentiate between persistent defects, redistribution, and reverse redistribution. A score was developed that measured the degree of inhomogeneity and severity of perfusion defects, respectively. Findings on scintigraphy were correlated to coronary intravascular ultrasound findings. RESULTS: At first investigation, mean intimal index of all evaluated coronary cross-sectional areas was 0.06 +/- 0.1. Sixty-four cross-sectional areas demonstrated a three-layer appearance of the vessel wall, mean circumferential extension was 72 +/- 122 degrees. Thallium scintigraphy demonstrated a total of 336 (40%) pathological left ventricular segments; 168 (20%) were regarded as permanent defects, 67 (8%) demonstrated redistribution and 101 (12%) showed reverse redistribution. The score of inhomogeneity was calculated as 5.8% +/- 2.6%. In the subgroup of patients at the follow-up study, the score was 6.4 +/- 2.8%. There was no correlation between intimal index and the score, nor could any correlation be confirmed between the score and the circumferential extension of a three-layer appearance of the vessel wall. At second investigation, no significant differences of intimal index (0.05 +/- 0.07) or circumferential extension of a three-layer appearance of the vessel wall (74 +/- 118 degrees) could be confirmed. The score was slightly, but significantly increased to 8.1 +/- 4.5% at the second investigation (P < 0.05). CONCLUSION: Early after orthotopic heart transplantation, pathologic thallium distribution patterns of the left ventricle could be observed. These pathological patterns did not correlate with the extent of diffuse coronary vessel wall alterations identifiable by intravascular ultrasound. After more than 1 year, the degree of scintigraphic abnormalities increased significantly, not accompanied by an increase of diffuse coronary vessel wall alterations.

Adult↗
PubMed1996

Noninvasive risk modeling after myocardial infarction.

The aim of this study was to extract and combine non-invasive risk parameters from the signal-averaged electrocardiogram (SAECG) and heart rate variability (HRV) based on 24-hour ambulatory electrocardiography to optimize the prognostic value for arrhythmic events after acute myocardial infarction. A prospective series of 553 men < 66 years of age enrolled in the Post-Infarction Late Potential study were analyzed. Within 2 to 4 weeks after acute myocardial infarction, all patients underwent SAECG and 24-hour ambulatory electrocardiography before hospital discharge. During 6 months of followup, 25 patients (4.5%) experienced arrhythmic events (sustained ventricular tachycardia, n = 11; ventricular fibrillation, n = 7; sudden cardiac death, n = 7). The predictive power of SAECG and HRV parameters was assessed using a Cox proportional-hazards model. In HRV analysis, the most significant differences between patients with and without arrhythmic events were observed for the beat-to-beat parameter root-meansquare of successive RR differences [RMSSD]): 25.7 +/- 16.9 ms in patients with arrhythmic events versus 34.1 +/- 18.6 ms in patients free of arrhythmic events (p = 0.004). Time domain analysis of the SAECG showed the QRS duration to be most significantly different in both patient groups: 106.4 +/- 18.7 ms (arrhythmic events) versus 95.3 +/- 18.7 ms (no arrhythmic events) (p = 0.001). Based on the Cox regression model, RMSSD and QRS duration were demonstrated to be independent significant risk factors (regression coefficient for QRS duration: cq = 0.014 +/- 0.006 ms(-1), p = 0.014; for RMSSD: cr = -0.041 +/- 0.016 ms(-1), p = 0.009). Based on the regression coefficients, an analytic risk model was developed describing the arrhythmic risk as a function of QRS duration, RMSSD, and time after infarction. We conclude that the combination of beat-to-beat changes of heart rate measured by RMSSD and QRS duration from the SAECG enhances noninvasive risk stratification after myocardial infarction.

Arrhythmias, Cardiac↗
PubMed1996

Drugs or implantable cardioverter-defibrillators in patients with poor left ventricular function?

Poor left ventricular function is a predictor of sudden death. Both antiarrhythmic drugs and implantable cardioverter-defibrillators (ICDs) promise to reduce the sudden death rate in these patients and consequently improve survival. In patients without spontaneous ventricular tachyarrhythmias, only beta-blocking agents and amiodarone have been shown to reduce sudden death and improve survival in some studies, whereas class I antiarrhythmic drugs increased mortality. For patients with documented ventricular tachyarrhythmias, protection against sudden death by serially tested class I antiarrhythmic drugs is at best moderate. There is some evidence suggesting that therapy with class III antiarrhythmic drugs, either amiodarone or dl-sotalol, may reduce sudden death rates and improve overall mortality in comparison to therapy with class I antiarrhythmic drugs. ICDs have been shown to prevent sudden death reliably. In published patient cohorts in which only patients who were not inducible off antiarrhythmic drugs or still inducible on antiarrhythmic drugs received an ICD, the ICD seemed to improve overall survival in comparison to class I antiarrhythmic drugs. A small prospective randomized study that compared a conventional therapy strategy to primary ICD implantations showed an improved outcome with ICDs as therapy of first choice. However, these studies included many patients treated with class I antiarrhythmic drugs considered to be less effective. In matched control studies comparing the ICD to amiodarone or dl-sotalol, less sudden deaths and an improved overall survival could be shown for the ICD in general without stratification for left ventricular function. Thus, in patients with hemodynamically nontolerated ventricular tachyarrhythmias, the ICD seems to improve survival in comparison to class I antiarrhythmic drugs, dl-sotalol, or amiodarone. However, in patients with poor left ventricular function, therapy with ICDs seems to be less cost-effective than in patients with preserved left ventricular function. In patients with very poor left ventricular function who are evaluated for cardiac transplantation, the ICD seems to change only the mode of death from sudden to a nonsudden cardiac death if transplantation cannot be performed soon.

Anti-Arrhythmia Agents↗
PubMed1996

Comparison of d,l-sotalol and implantable defibrillators for treatment of sustained ventricular tachycardia or fibrillation in patients with coronary artery disease.

BACKGROUND: Implantable cardioverter-defibrillators (ICDs) and d,l-sotalol are widely used to treat ventricular tachyarrhythmia and ventricular fibrillation (VT/VF). The purpose of this study was to compare the long-term efficacy of d,l-sotalol and ICDs in patients with coronary artery disease. METHODS AND RESULTS: In a case-control study, 50 patients treated with oral d,l-sotalol were matched to 50 patients treated with ICDs. Both groups were matched for sex (82 men), age (58 +/- 10 years), ejection fraction (40 +/- 12%), extent of coronary artery disease, presenting arrhythmia, and year that treatment began. In all patients in the sotalol group, VT/VF was inducible in the drug-free electrophysiological study. Induction of sustained VT/VF was suppressed by d,l-sotalol (438 +/- 95 mg/d). In the ICD group, either VT/VF was not inducible (n = 5) or inducible sustained VT/VF was refractory to antiarrhythmic drug treatment (n = 45). Sotalol treatment led to a marked reduction in arrhythmic events. Whereas 83% of the patients in the sotalol group were free of sudden death and nonfatal VT at 3 years, only 33% of the ICD patients did not receive appropriate ICD therapies (P < .005). Actuarial rates for absence of sudden death at 3 years were 85% in the sotalol group and 100% in the ICD group (P < .005). Actuarial rates for overall survival at 3 years were 75% in the sotalol group and 85% in the ICD group (P = .02). CONCLUSIONS: In this case-control study, ICD therapy was more effective tha electrophysiologically guided antiar-rhythmic treatment with d,l-sotalol in prevention of sudden death and reduction of total morality in patients with coronary artery disease. Prospective studies are needed to confirm these results.

Administration, Oral↗
PubMed1996

RR interval variability in irregular monomorphic ventricular tachycardia and atrial fibrillation.

BACKGROUND: Algorithms to reject irregular tachyarrhythmias are available in implantable cardioverter-defibrillator devices to discriminate ventricular tachycardia (VT) from atrial fibrillation (AF). The hazard of underdetection of irregular monomorphic VTs using these algorithms has not yet been fully evaluated. The purpose of this study was to determine the ability of a commonly used stability algorithm to reject AF and to correctly detect VT with a high RR interval variability. METHODS AND RESULTS: The electrophysiological studies from 232 patients with induced monomorphic VT (cycle length > 250 ms) and 21 with AF were reviewed. A preliminary analysis was performed to classify the VT episodes in irregular (successive RR differences > 20 ms after 4 seconds from onset) or regular (otherwise). Three study groups were defined: group 1 (27 patients with irregular VT), group 2 (22 randomly selected patients with regular VT), and group 3 (21 patients with AF). A computer program analyzed the first 50 RR intervals of the induced VT (AF), resetting a VT counter if the interval was greater than a tachycardia detection interval (TDI) or if its absolute difference with the preceding three beats exceeded a programmed stability value (STAB). The VT was detected when the VT counter reached a preset number of intervals (NIDs). Different combinations of TDI, STAB, and NID were analyzed. All VTs in group 2 were correctly detected. In contrast, up to 10 VTs from group 1 were not detected when high NIDs and low STAB parameters were programmed. With usual values (10 to 16 beats and 50 to 60 ms, respectively), only 1 to 2 VTs remained undetected, but 20% to 50% had a detection delay > 8 seconds. Undetected VTs were significantly slower than early detected VTs for most STAB and NID combinations. With usual stability and NID values, 10% to 20% of episodes of AF were inappropriately detected. Changes in TDI had a small impact on sensitivity and specificity when currently used values for stability were programmed. CONCLUSIONS: Animplantable cardioverter-defibrillator tachycardia detection algorithm with a stability criterion of 50 to 60 ms and 12 to 14 RR intervals is able to detect over 90% of monomorphic irregular VTs. Nevertheless, significant VT detection delays may arise, and inappropriate detection of AF cannot be totally prevented.

Adult↗
PubMed1996

Heart transplant candidates at high risk can be identified at the time of initial evaluation.

The increasing discrepancy between the numbers of patients selected for cardiac transplantation and the available donor organs requires validation of markers of high risk at the time of initial evaluation that may help to determine which patients profit from aggressive therapy. We retrospectively examined the case records of 91 heart transplant candidates selected out of a total of 140 consecutive patients referred for evaluation. Of these 91 patients, 48 were transplanted during follow-up. Of the remaining 43 patients, 25 died after a mean survival time of 1.6 +/- 2.5 months. The causes of death were pump failure in 18 (72%) and sudden cardiac death in 7 (28%). Multivariate analysis identified 4 out of 26 parameters at initial evaluation that distinguished the 25 nonsurvivors from the 18 survivors. These were: mean arterial pressure (P = 0.03), pulmonary capillary wedge pressure (P = 0.002), mean pulmonary artery pressure (P = 0.001), and fractional shortening (P = 0.007). The mode of death could not be predicted. We conclude that there are prognostic markers at initial evaluation that allow more restrictive selection of patients for cardiac transplantation and mechanical bridging.

Adult↗
PubMed1996

The clinical impact of thallium-201 reinjection for the detection of myocardial hibernation.

Thallium-201 reinjection improves detection of hibernating myocardium in about 30%-50% of persisting defects. The main goal of cardiac revascularization techniques is amelioration of clinical symptoms such as angina and dyspnoea; however, improvement in regional and global pump function is an additional and important target. The aim of this study was to investigate whether fill-in in the reinjection study is correlated with improved contractile function after treatment (percutaneous transluminal coronary angioplasty/aortocoronary bypass surgery). We studied 32 patients with coronary heart disease and impaired regional wall motion (RWM). RWM and ejection fraction (EF) were assessed by analysing ventriculographic images using the centreline method (values in standard deviations from mean values found in a healthy control group). Three 201Tl single-photon emission tomographic studies (stress, redistribution and reinjection) were performed prior to revascularization and analysed using a bull s-eye scheme. Patients were divided into two groups (group FI-=no fill-in, n=16; group FI+=fill-in, n=16). Fifty-six percent of all patients showed persisting defects, and 56% of these defects showed fill-in after reinjection. Fill-in in our patient group was independent of the size of the persisting defects. After revascularization RWM increased significantly in group FI+ (from -1.9 to 0.0 SD, P<0.001) whereas group FI- showed no significant change (from -1.6 to -1.8 SD). EF increased from -4.3 preoperatively to -2.1 SD postoperatively in group FI+ and did not change significantly in group FI- (-2.5 to -3.2 SD). The predictive value of reinjection for improvement of RWM was 88%. It is concluded that fill-in in the 201Tl reinjection image can predict recovery of RWM and EF after revascularization and should be used in all patients with impaired RWM and persisting defects independent of their extent.

Adult↗
PubMed1996

Human recombinant insulin-like growth factor I and -II stimulate the expression of basic fibroblast growth factor but suppress the division of bovine coronary smooth muscle cells.

Insulin-like growth factor I and II (IGF-I and -II)--two 7.65- and 7.47-kDA polypeptides belonging to the somatomedine family--are regular constituents of human blood plasma. Both factors exert mitogenic activity on a variety of cell types including arterial smooth muscle cells. In the present study, the effect of IGF-I and -II on cultured bovine coronary smooth muscle cells (cSMC) was assessed. Human recombinant IGF-I and IGF-II added to cSMC cultured in a medium containing 10% fetal bovine serum (FBS) decreased the cell number and [3H]thymidine incorporation in a dose dependent fashion up to 40% and 43% compared to control cells (100%). At the same time, the expression of basic fibroblast growth factor (bFGF) increased from 60 pg/5 x 10(4) cells (control) to 75 (IGF-I) and 113 pg/5 x 10(4) cells (IGF-II). In parallel with enhanced bFGF expression, the bFGF receptor content per cell and the [35S]sulfate incorporation into extracellular and cell-associated proteoglycans also increased under the influence of IGF-I and -II. In contrast, with low serum concentration (0.1% FBS) the addition of IGF-I and -II to bovine cSMC cultures resulted in a slight increase in cell number, protein content and [3H]thymidine incorporation as described in previous studies. These results suggest that the mitogenic activity of IGF-I and -II towards coronary smooth muscle cells depends on culture conditions. In the presence of 10% fetal bovine serum that mimics in vivo conditions, IGF-I and -II did not necessarily act as mitogenic factors but inhibited the proliferation of cSMC in vitro possibly by modulating antagonizing the action of other growth factors. Irrespective of the inhibition of cell division, the cellular bFGF, the bFGF receptor and the bFGF activity-related proteoheparan sulfate were overexpressed under the influence of IGF.

Animals↗
PubMed1996

Predictive value of wavelet correlation functions of signal-averaged electrocardiogram in patients after anterior versus inferior myocardial infarction.

OBJECTIVES: This study sought to evaluate the prognostic value of wavelet correlation functions of the signal-averaged electrocardiogram (ECG) for arrhythmic events in patients after myocardial infarction. BACKGROUND: Wavelet transform of the signal-averaged ECG has been shown to be a nonstationary analysis technique describing the time evolution of frequency spectra throughout the QRS complex. To quantify the wavelet transform, we introduced the new concept of the wavelet correlation function. METHODS: The relation among wavelet correlation functions, ventricular late potentials and the site of infarction was investigated in 769 men < 66 years old who survived the acute phase of myocardial infarction (351 [46%] anterior, 418 [54%] inferior infarctions). Signal-averaged ECG recordings were obtained 2 to 3 weeks after infarction. During 6 months of follow-up, 33 patients (4.3%) experienced a malignant arrhythmic event. Wavelet correlation functions of the signal-averaged ECG were evaluated in a time-frequency plane ranging from 25 ms before QRS onset to 25 ms after QRS offset in the frequency range between 40 and 100 Hz. RESULTS: Patients with an anterior infarction had lower mean wavelet correlation coefficients (p < 0.001) and a lower incidence of ventricular late potentials than patients with an inferior infarction (32.3% vs. 42.7%, p = 0.003). The combination of wavelet correlation functions and late potentials increased the total predictive accuracy from 52% to 72% for inferior and from 64% to 76% for anterior infarctions. CONCLUSIONS: Spectral changes in the signal-averaged QRS complex are more prominent in anterior than inferior infarctions. Combination of late potential analysis and wavelet correlation functions increases the prognostic value for serious arrhythmic events after myocardial infarction.

Adult↗