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Biomedical subjects

C Stellbrink

Publications and source records attributed to C Stellbrink.

At least 37 records · Page 2Linked to original sources
PubMed2001

Impact of cardiac resynchronization therapy using hemodynamically optimized pacing on left ventricular remodeling in patients with congestive heart failure and ventricular conduction disturbances.

OBJECTIVES: We sought to investigate the impact of six months of cardiac resynchronization therapy (CRT) on echocardiographic variables of left ventricular (LV) function. BACKGROUND: Cardiac resynchronization therapy has recently been introduced as a new therapeutic modality in patients with advanced heart failure (HF) and conduction abnormalities. However, most studies have only investigated the early hemodynamic effects of CRT. METHODS: Twenty-five patients (12 women and 13 men; 59.8 +/- 5.1 years old) with advanced HF caused by ischemic (n = 7) or idiopathic dilated cardiomyopathy (n = 18) and a prolonged QRS complex were analyzed. All patients underwent early hemodynamic testing with a randomized testing protocol; echocardiographic measurements were compared before implantation and after six months of CRT. RESULTS: Left ventricular end-diastolic and end-systolic diameters (LVEDD and LVESD, respectively) were significantly reduced after six months (LVEDD from 71 +/- 10 to 68 +/- 11 mm, p = 0.027; LVESD from 63 +/- 11 to 58 +/- 11 mm, p = 0.007), as were LV end-diastolic and end-systolic volumes (LVEDV from 253 +/- 83 to 227 +/- 112 ml, p = 0.017; LVESV from 202 +/- 79 to 174 +/- 101 ml, p = 0.009). Ejection fraction was significantly increased (from 22 +/- 7% to 26 +/- 9%, p = 0.03). "Nonresponders," with regard to LV volume reduction, had significantly higher baseline LVEDV, compared with "responders" (351 +/- 52 vs. 234 +/- 74 ml, p = 0.018). Overall, there was only mild mitral regurgitation at baseline, with a minor reduction by semiquantitative analysis. The results of early hemodynamic testing did not predict the volume response. CONCLUSIONS: Cardiac resynchronization therapy may lead to a reduction in LV volumes in patients with advanced HF and conduction disturbances. Volume nonresponders have significantly higher baseline LVEDV.

Aged↗
PubMed2001

Differential effects of atropine and isoproterenol on inducibility of atrioventricular nodal reentrant tachycardia.

BACKGROUND: Radiofrequency ablation of the "slow pathway" in atrioventricular nodal reentrant tachycardia (AVNRT) relies on tachycardia non-inducibility after ablation as success criterion. However, AVNRT is frequently non-inducible at baseline. Thus, autonomic enhancement using either atropine or isoproterenol is frequently used for arrhythmia induction before ablation. METHODS: 80 patients (57 women, 23 men, age 50+/-14 years) undergoing slow pathway ablation for recurrent AVNRT were randomized to receive either 0.01 mg/kg atropine or 0.5-1.0 microg/kg/min isoproterenol before ablation after baseline assessment of AV conduction. The effects of either drug on ante- and retrograde conduction was assessed by measuring sinus cycle length, PR and AH interval, antegrade and retrograde Wenckebach cycle length (WBCL), antegrade effective refractory period (ERP) of slow and fast pathway and maximal stimulus-to-H interval during slow and fast pathway conduction. RESULTS: Inducibility of AVNRT at baseline was not different between patients randomized to atropine (73%) and isoproterenol (58%) but was reduced after atropine (45%) compared to isoproterenol (93%, P<0.001). Of the 28 patients non-inducible at baseline isoproterenol rendered AVNRT inducible in 21, atropine in 4 patients. Dual AV nodal pathway physiology was present in 88% before and 50% after atropine compared to 83% before and 73% after isoproterenol. Whereas both drugs exerted similar effects on ante- and retrograde fast pathway conduction maximal SH interval during slow pathway conduction was significantly shorter after isoproterenol (300+/-48 ms vs. 374+/-113 ms, P=0.012). CONCLUSION: Isoproterenol yields higher AVNRT inducibility than atropine in patients non-inducible at baseline. This may be caused by a more pronounced effect on antegrade slow pathway conduction.

Adult↗
PubMed2001

Morphology discrimination: a beat-to-beat algorithm for the discrimination of ventricular from supraventricular tachycardia by implantable cardioverter defibrillators.

Inappropriate therapy of SVTs by ICDs remains a major clinical problem despite enhanced detection criteria like "sudden onset" and "rate stability" in third-generation devices. Electrogram morphology discrimination offers an additional approach to improve discrimination of supraventricular tachycardia (SVT) from ventricular tachycardia (VT). In a prospective, multicenter study, patients received an ICD with a beat-to-beat algorithm for morphological analysis of the intracardiac electrogram (Morphology Discrimination, MD). A nominal programmingfor standard enhancement criteria and morphology discrimination was required at implant. Electrogram storage of tachycardia episodes irrespective of delivery of therapy was used to assess sensitivity and specificity of the morphology algorithm alone and in combination with established detection criteria. During a 126 6-month follow-up, 886 episodes of device stored electrograms from 82 of 256patients were evaluated. Atnominal settings, the MD algorithm correctly identified 423 of 551 episodes as VT resulting in sensitivity of 77%. The classification of SVT was met in 239 of 335 episodes resulting in specificity of 71%. In combination with sudden onset, sensitivityincreased to 99.5% at the expense of specificity (48%). In conclusion, SVT-VT discrimination based on morphological analysis alone results in limited sensitivity and specificity. Programming the monitor mode allows individual assessment of the performance of this detection enhancement feature during clinical follow-up without compromising device safety. Only in patients with documented efficacy of morphology discrimination should this feature be subsequently activated.

Algorithms↗
PubMed2001

Verapamil prevents stretch-induced shortening of atrial effective refractory period in langendorff-perfused rabbit heart.

INTRODUCTION: Atrial dilation and rapid pacing reduce atrial effective refractory periods (AERPs), thereby increasing the susceptibility to sustained atrial fibrillation (AF) in Langendorff-perfused rabbit hearts. It is unclear whether similar pathophysiologic mechanisms are operative in short-term electrophysiologic changes caused by dilation and rapid pacing. Therefore, we analyzed whether both forms of short-term electrophysiologic changes are similarly affected by pharmacologic interventions acting on different potential mechanisms underlying these changes. METHODS AND RESULTS: Thirty Langendorff-perfused rabbit hearts underwent a protocol with stepwise increase of intra-atrial pressure from 0 to 12 cm H2O followed by 10 minutes of rapid pacing at 4 cm H2O. The protocol was repeated after addition of glibenclamide (10 micromol/L, n = 7), cariporide (1 micromol/L, n = 7), or verapamil (1 micromol/L, n = 9). In the basal state, increase of intra-atrial pressure from 0 to 12 cm H2O decreased AERPs from 85 +/- 11 to 55 +/- 9 msec (P < 0.01), rapid pacing at low intra-atrial pressure (4 cmH2O) decreased AERP to a similar extent, from 81 +/- 11 to 60 +/- 10 (P < 0.01). At higher intra-atrial pressure, decrease of AERP was more pronounced (10 cm H2O: 37 +/- 2 msec) (n = 7). Addition of verapamil decreased basal AERP from 86 +/- 10 msec to 68 +/- 11 msec (P < 0.05). Short-term electrophysiologic changes due to atrial dilation were abolished; changes due to rapid pacing were reduced but still present. Glibenclamide and cariporide had no significant effect. CONCLUSION: Langendorff-perfused rabbit heart is a suitable model for studying short-term electrophysiologic changes due to both rapid pacing and atrial dilation. AERPs are shortened to a similar extent by both mechanisms, whereas a combination of the two leads to more pronounced AERP reduction. Calcium overload plays a crucial role in short-term electrophysiologic changes caused by atrial dilation, whereas atrial ischemia or acidosis has no significant impact.

Animals↗
PubMed2001

Evidence of sinoatrial block as a curative mechanism in radiofrequency current ablation of inappropriate sinus tachycardia.

Inappropriate sinus tachycardia is a nonparoxysmal tachycardia characterized by high resting heart rates and a disproportionate response to activity. Sinus node modification with radiofrequency current has been used successfully as treatment for this arrhythmia. However, the electrophysiologic mechanisms leading to successful modification are not yet fully elucidated. We report a case of a patient with drug-resistant inappropriate sinus tachycardia in whom successful treatment of the arrhythmia was achieved by documented sinoatrial exit block induced by radiofrequency current applications.

Adult↗
PubMed2001

Stimulation of the left ventricle through the coronary sinus with a newly developed 'over the wire' lead system--early experiences with lead handling and positioning.

AIMS: This report describes the initial clinical results with a newly designed guiding catheter and an 'over the wire' pacing lead based on angiolasty technology to stimulate the left ventricle using the transvenous route via the coronary sinus (OTW-CV lead). METHODS AND RESULTS: In 75% of the 15 patients (6 males, 9 females, mean age of 53 +/- 9 years) with congestive heart failure, access to coronary sinus required less than 2 min; in one patient. the attempt failed. Mean R wave amplitudes plus or minus the standard deviation, measured at apical, mid-ventricular and basal positions the anterior (11.4 +/- 9.2, 10.8 +/- 6.2, 9.3 +/- 6.3 mV) and lateral or posterior veins (10.1 +/- 10.7, 8.6 +/- 6.4, 7.7 +/- 4.3 mV) showed a trend favouring the apex without statistical significance. Pacing impedance, measured at the same sites and vein tributaries, ranged from 670 +/- 191 to 915 +/- 145 ohms. Pacing thresholds measured at apical and mid ventricular sites were significantly lower than at the base in the anterior vein 2.5 +/- 2.8 and 2.8 +/- 1.8 vs 5.6 +/- 2.7 V at 0.5 ms, P<0.001). Thresholds in the lateral/posterior veins showed a similar trend but did not reach statistical significance (3.0 +/- 1.7, 3.6 +/- 1.4 +/- 1.8 V at 0.5 ms). In patients, in whom thresholds were determined in more than one vein, the 'best' mean threshold was 1.6 +/- 0.7 V. CONCLUSION: The new 'over the wire' lead and guiding catheter system allows uncomplicated access to the coronary sinus and the depth of the coronary vein tributaries. Left ventricular sensing and pacing thresholds are acceptable for chronic use in implanted cardiac rhythm management systems.

Adult↗
PubMed2000

Echocardiographic evidence of hemodynamic and clinical improvement in patients paced for heart failure.

Dilated cardiomyopathy is frequently associated with electrical conduction disturbances. Development of left bundle-branch block with discoordinated ventricular contraction pattern further contributes to impaired hemodynamic performance. Biventricular pacing has evolved as a new treatment option for patients with dilated cardiomyopathy and conduction disturbances. The "electrical" approach aims to normalize the disturbed contraction pattern, thereby improving hemodynamic function by simultaneous stimulation at different ventricular sites. Acute hemodynamic improvement with biventricular pacing has been demonstrated in patients with depressed left ventricular function and delayed intraventricular conduction. Due to the variations in optimal pacing site and atrioventricular delay, individual optimization to achieve optimal hemodynamic benefit is necessary. Echocardiography has the potential to provide hemodynamic data by Doppler techniques and combine these with geometric information about ventricular volumes, ejection fraction, and contraction patterns. This article focuses on the use of echocardiographic techniques for noninvasive optimization in cardiac pacing and presents preliminary experience from the initial trials on multisite pacing in heart failure.

Arrhythmias, Cardiac↗
PubMed2000

Pacing Therapies in Congestive Heart Failure II study.

Ventricular resynchronization therapy (VRT) by left or biventricular stimulation is gaining increasing acceptance as a new therapy in addition to drugs in patients with advanced heart failure and intraventricular conduction disturbances. Several studies have demonstrated acute hemodynamic benefit of VRT in these patients, although there are only limited long-term data in small patient cohorts. Many open questions remain: whether to pace both ventricles or the left ventricle alone, the optimal left ventricular pacing site, the criteria used to identify the optimal candidate for VRT (e.g., QRS width), and the importance of an integrated defibrillator function in a VRT device. The Pacing Therapy in Congestive Heart Failure (PATH-CHF) II study is a prospective, randomized, cross-over study currently investigating the potential benefit of VRT in a population with advanced heart failure, with or without an accepted indication for an implantable defibrillator. It focuses on the effects of optimized univentricular pacing in these patients, and both acute hemodynamic and chronic functional effects are assessed. Acute hemodynamic testing mainly investigates the impact of different left ventricular pacing sites, alone or combined with right ventricular sites, on hemodynamic performance. Primary endpoint of the study is an improvement in functional capacity as assessed by cardiopulmonary exercise testing and 6-minute walk distance; secondary endpoints include improvement in quality of life (assessed by Minnesota quality of life score, New York Heart Association (NYHA) functional class, and hospitalization frequency), and improvements in prognostic and hemodynamic parameters. The trial aims to enroll 64 patients with full datum sets (separately in 2 groups with a QRS of < or = 150 or > 150 msec, respectively) in 9 European centers. The enrollment began September 1998, and is expected to conclude in summer 2000 to reach the number of necessary datum sets.

Arrhythmias, Cardiac↗
PubMed2000

Should stimulation site be tailored in the individual heart failure patient?

Right ventricular pacing at various sites and shortened atrioventricular (AV) delay has failed to demonstrate a convincing short-term and long-term improvement of left ventricular function. Left-ventricular-based stimulation offers a new therapeutic option for patients with symptomatic congestive heart failure and conduction disturbances, especially of left bundle-branch block configuration. Left ventricular mechanical improvement seems mainly dependent on the pacing site, in addition to optimizing the AV delay. Predominantly retrospective data suggest that pacing the posterolateral free wall results in the greatest hemodynamic improvement. Based on the evaluation of different pacing sites in 2 patients, we noted that site is of major importance for maximal improvement of left ventricular function, and pacing at a suboptimal site can even deteriorate left ventricular contractility. Moreover, lead technology has advanced rapidly and different areas of the left ventricle can now be reached transvenously for acute and chronic placement. Therefore, ongoing trials will help to identify the optimal pacing site and might indicate whether invasive testing will be required in the future.

Arrhythmias, Cardiac↗
PubMed2000

[A new ICD morphology criterion for differentiating supraventricular and ventricular tachycardia].

The high incidence of inappropriate therapies due to supraventricular tachycardia remains a major unsolved problem of the implantable cardioverter defibrillator. A new morphology discrimination (MD) algorithm has been introduced to improve specificity of ICD therapy without loss of sensitivity. It was the aim of this study to systematically analyze sensitivity and specificity of the MD criterion in combination with the enhanced detection criteria sudden onset and rate stability in the detection of ventricular and supraventricular tachycardia. After ICD implantation in 259 patients, 787 detected episodes in 74 patients with available stored electrograms were documented during a follow-up period of 359 +/- 214 days. With a nominal programming of the MD algorithm at > or = 60%, sensitivity and specificity for all episodes were 82.6%/77.2%. For sinus tachycardia, atrial fibrillation and atrial flutter the specificities were 80.6%, 69.6% and 75%, respectively. In patients with primarily appropriate MD detection, sensitivity and specificity significantly improved to 95.8%/91.7%. Programming the sudden onset criterion with < 100 ms and the stability criterion with < 50 ms, sensitivity and stability of the combined application of the MD algorithm and sudden onset and MD algorithm and stability were 96.2%/52.2% and 94.4%/63.8%, respectively. The MD criterion in combination with other enhanced detection criteria might significantly improve specificity of tachyarrythmia detection of ICD therapy.

Aged↗
PubMed2000

Intraoperative amiodarone as prophylaxis against atrial fibrillation after coronary operations.

BACKGROUND: New onset of atrial fibrillation is a frequent complication after coronary artery bypass grafting and is a major cause of postoperative morbidity. Preoperative oral treatment with amiodarone hydrochloride has been shown to be efficacious as prophylaxis. The present study investigated whether intraoperative use of intravenous amiodarone has a preventive effect on the incidence of atrial fibrillation after coronary revascularization. METHODS: In a prospective study, 150 consecutive patients (mean age, 63 +/- 8 years; 132 men and 18 women) undergoing coronary artery bypass grafting were randomly assigned to one of three groups. Two groups received different doses of intravenous amiodarone (group I, 300-mg bolus and 20 mg x kg(-1) x day(-1) for 3 days; group II, 150-mg bolus and 10 mg x kg(-1) x day(-1) for 3 days) after aortic cross-clamping and one group, placebo (group III). Continuous electrocardiographic online monitoring was performed for 10 days. Arrhythmias were analyzed with respect to type, frequency, duration, and clinical relevance. RESULTS: New onset of atrial fibrillation occurred in 24% of patients in group I, 28% in group II, and 34% in group III (p = not significant). Atrial fibrillation with a rapid ventricular response (>120 beats per minute) was significantly more frequent in the control group (group I, 14%; group II, 24%; group III, 32%; p < 0.05, group I versus group III) and appeared significantly earlier (group I, day 4.3 +/- 2.5; group II, day 4.8 +/- 2.9; group III, day 2.6 +/- 1.3; p < 0.05, group III versus groups I and II). Temporary atrial pacing because of bradycardia (<60 beats per minute) was necessary significantly more often in group I (group I, 48%; group II, 40%; group III, 28%; p < 0.05, group I versus group III). Early mortality rate (group I, 4%; group II, 2%; group III, 4%), rate of perioperative complications (group I, 14%; group II, 20%; group III, 14%), and duration of hospital stay (group I, 14.0 days; group II, 14.4 days; group III, 14.7 days) were not different between groups. CONCLUSIONS: Intraoperative prophylactic use of amiodarone does not prevent new onset of atrial fibrillation in patients undergoing coronary artery bypass grafting and had no effect on outcome. Therefore, intraoperative prophylactic treatment with amiodarone at the tested doses does not appear to be justified.

Amiodarone↗
PubMed2000

[Catheter ablation of accessory pathways and atrioventricular nodal reentry tachycardia].

Radiofrequency current catheter ablation has gained acceptance as primary long-term therapy for patients with symptomatic accessory pathways and symptomatic atrioventricular nodal reentrant tachycardia (AVNRT) with frequent recurrences. In both arrhythmias, curative treatment is possible in more than 90% of cases at a low complication rate although an incidence of about 1% complete AV block after slow pathway ablation has to be taken into account when this therapy is considered. The recurrence rate is 3-10% for accessory pathways and 0-15% for AVNRT. The high success rate of catheter ablation has already led to a shift in the indications for the procedure where the percentage of patients with accessory pathways is decreasing and there is an increase of patients with AVNRT and newer indications (atrial flutter, focal atrial tachycardias).

Catheter Ablation↗
PubMed1999

Spatial features in body surface potential maps of patients with ventricular tachyarrhythmias with or without coronary artery disease.

Body surface potential maps (BSPM) from patients with coronary artery disease or no structural heart disease were analyzed with respect to their spatial features and QT/QTc dispersion in order to determine whether BSPM allows identification of patients with ventricular fibrillation. QRST integral maps and QT/QTc dispersion were acquired from simultaneous recordings of 62 ECG leads during sinus rhythm in patients with idiopathic ventricular fibrillation (n=13), ventricular fibrillation and coronary artery disease (n=22), coronary artery disease without ventricular fibrillation (n=21) and healthy controls (n=18). The Karhunen-Loeve transformation was applied to reduce the dimensionality of the data matrix of the QRST map to eight coefficients. Linear discriminant analysis allowed discrimination between idiopathic ventricular fibrillation patients and controls with high sensitivity (85%) and specificity (89%). However, discrimination between coronary artery disease patients with or without ventricular fibrillation was poor (68% and 67%, respectively). QTc dispersion calculated from BSPM was longer in idiopathic ventricular fibrillation patients than in controls (99+/-30 ms vs 70+/-14 ms, P=0.009) in contrast to QTc dispersion taken from 12-lead ECG (53+/-21 ms vs. 47+/-12 ms, P=n.s.). No significant difference was noted for coronary artery disease patients with or without ventricular fibrillation. In conclusion, repolarization disturbances detected by BSPM allow identification of ventricular fibrillation patients without structural heart disease. However, our results do not suggest a major impact of QT/QTc dispersion or QRST integral mapping for identification of ventricular fibrillation patients with coronary artery disease.

Body Surface Potential Mapping↗
PubMed1999

Effect of pacing chamber and atrioventricular delay on acute systolic function of paced patients with congestive heart failure. The Pacing Therapies for Congestive Heart Failure Study Group. The Guidant Congestive Heart Failure Research Group.

BACKGROUND: Previous studies of pacing therapy for dilated congestive heart failure (CHF) have not established the relative importance of pacing site, AV delay, and patient heterogeneity on outcome. These variables were compared by a novel technique that evaluated immediate changes in hemodynamic function during brief periods of atrial-synchronous ventricular pacing. METHODS AND RESULTS: Twenty-seven CHF patients with severe left ventricular (LV) systolic dysfunction and LV conduction disorder were implanted with endocardial pacing leads in the right atrium and right ventricle (RV) and an epicardial lead on the LV and instrumented with micromanometer catheters in the LV, aorta, and RV. Patients in normal sinus rhythm were stimulated in the RV, LV, or both ventricles simultaneously (BV) at preselected AV delays in a repeating 5-paced/15-nonpaced beat sequence. Maximum LV pressure derivative (LV+dP/dt) and aortic pulse pressure (PP) changed immediately at pacing onset, increasing at a patient-specific optimal AV delay in 20 patients with wide surface QRS (180+/-22 ms) and decreasing at short AV delays in 5 patients with narrower QRS (128+/-12 ms) (P<0.0001). Overall, BV and LV pacing increased LV+dP/dt and PP more than RV pacing (P<0.01), whereas LV pacing increased LV+dP/dt more than BV pacing (P<0.01). CONCLUSIONS: In this population, CHF patients with sufficiently wide surface QRS benefit from atrial-synchronous ventricular pacing, LV stimulation is required for maximum acute benefit, and the maximum benefit at any site occurs with a patient-specific AV delay.

Aged↗
PubMed1999

Effect of biphasic shock duration on defibrillation threshold with different electrode configurations and phase 2 capacitances: prediction by upper-limit-of-vulnerability determination.

BACKGROUND: The defibrillation threshold (DFT) may be affected by biphasic shock duration (BSD), electrode configuration, and capacitance. The upper limit of vulnerability (ULV) may be used to estimate the DFT. For different lead configurations and phase 2 capacitances, we investigated in 18 pigs whether the use of ULV may predict waveforms with lowest DFT. METHODS AND RESULTS: -DFT and ULV were determined by up-down protocols for 10 BSDs. ULVs were measured by T-wave scanning during ventricular pacing (cycle length 500 ms). In protocol 1 (n=6), a pectoral "active can" was combined with an electrode in the superior vena cava as common cathode and a right ventricle electrode as anode (AC+SVC). In protocol 2 and protocol 3 (n=6 each), only the "active can" was used as proximal electrode (AC). Capacitance was 150 microF during both phases in protocol 1 and protocol 3 but 150 microF (phase 1) and 300 microF (phase 2) in protocol 2. ULV and DFT demonstrated a linear correlation in each protocol (r=0.78 to 0.84). Lowest DFTs were found at 10 ms for AC+SVC and at 14 ms for AC (P<0.001). At optimal BSDs, voltage DFTs did not differ significantly between AC (527+/-57 V) and AC+SVC (520+/-70 V). Switching capacitors for phase 2 in a way that reduced leading-edge voltage by 50% while doubling capacity did not change BSD for optimal voltage DFT but increased minimum DFT from 527+/-57 V to 653+/-133 V (P=0.04). CONCLUSIONS: The BSD with lowest DFT is shorter for AC+SVC than for AC. There is no significant difference in voltage DFT between both at optimal BSD. A lower phase 2 capacitance reduces DFTs irrespective of BSD. Because strength-duration curves for DFT and ULV correlate for different BSDs, lead systems, and phase 2 capacitances, ULV determination may allow the prediction of waveforms with lowest DFT.

Animals↗