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T Klingenheben

Publications and source records attributed to T Klingenheben.

At least 37 records · Page 2Linked to original sources
PubMed1998

Assessment of QT dispersion for prediction of mortality or arrhythmic events after myocardial infarction: results of a prospective, long-term follow-up study.

BACKGROUND: Risk stratification by means of analysis of QT dispersion (QTD) in the 12-lead surface ECG is under intense investigation in various patient populations. The aim of the present prospective study was to evaluate the prognostic value of QTD and other ECG variables reflecting dispersion of ventricular repolarization in comparison with established risk stratifiers during long-term follow-up in a large cohort of post-myocardial infarction patients treated according to contemporary therapeutic guidelines. METHODS AND RESULTS: In 280 consecutive infarct survivors, the 12-lead ECG was optically scanned and digitized for analysis of QTD (QTmax-QTmin) and 25 other repolarization variables, including recently developed and validated parameters such as the T peak-to-T end interval and the area under the T wave. In addition, a variety of established risk stratifiers were assessed. After a mean follow-up period of 32+/-10 months, 30 patients reached one of the prospectively defined study end points (death, ventricular tachycardia, or resuscitated ventricular fibrillation). Comparisons between event and nonevent patients by means of Kaplan-Meier event probability analyses revealed that none of the ECG dispersion variables were of discriminative value. In contrast, variables such as left ventricular ejection fraction (P=0.007), mean 24-hour heart rate (P=0.022), or heart rate variability (P=0.007) proved to be potentially useful risk stratifiers in this patient population. On multivariate analysis, only LVEF, heart rate variability, and a history of thrombolysis were independent predictors of outcome. CONCLUSIONS: Determination of QTD from the surface ECG even when performed with the best available methodology failed to predict subsequent risk in this large series of infarct survivors.

Adult↗
PubMed1998

[Brief analysis of heart rate variability in for determining prognosis in the post-myocardial infarct period: methodologically reliable alternative to long-term ECG?].

Heart rate variability (HRV) has been established as an important risk parameter in patients surviving myocardial infarction. Recently, analysis of HRV-particularly of the standard deviation of NN intervals (SDNN)--from short term ECG recordings has been proposed as an alternative to that from 24 hour Holter monitorings. The present study is the first to compare SDNN from short term recordings to that from 24 hour recordings with respect to risk stratification after myocardial infarction. In 60 patients at the time of discharge from the hospital, SDNN from Holter monitoring averaged 93 +/- 30 ms compared to 39 +/- 18 determined from short term recordings. Patients with a prospectively defined clinical endpoint differed significantly from those with an uneventful course with respect to age, left ventricular ejection fraction, mean RR interval from Holter recording (753 +/- 153 vs 921 +/- 132 ms), mean RR from short term recording (783 +/- 153 vs 914 +/- 163 ms), and SDNN from the Hotler recording (71 +/- 27 vs 97 +/- 29 ms; p < 0.001). However, patients with and without a clinical event could not be separated by means of SDNN measured from short term ECG registrations (35 +/- 22 vs 41 +/- 19 ms; p = NS). Thus, SDNN measured from short term ECG recordings does not seem to be useful regarding risk stratification of patients after myocardial infarction. Analysis of HRV should be performed using 24 hour Holter monitoring, which provides more information and reflects circadian fluctuation in autonomic tone.

Adult↗
PubMed1998

Electrical storm in patients with transvenous implantable cardioverter-defibrillators: incidence, management and prognostic implications.

OBJECTIVES: The purpose of this study was to determine the precise incidence, therapeutic options and prognostic implications of electrical storm in patients with transvenous implantable cardioverter-defibrillator (ICD) systems. BACKGROUND: Approximately 50% to 70% of patients treated with an ICD receive appropriate device-based therapy within the first 2 years. Most arrhythmic events require only one appropriate ICD firing for termination. However, some patients receive multiple appropriate shocks during a short period of time, a condition referred to as "arrhythmic or electrical storm." METHODS: This prospectively designed observational study comprised 136 recipients of transvenous ICDs who were followed for 403+/-242 days. Electrical storm was defined as ventricular tachycardia or fibrillation resulting in device intervention > or = 3 times during a single 24-h period. RESULTS: During follow-up, 57/136 patients (42%) received appropriate ICD therapy. Electrical storm occurred in 14/136 patients (10%) at an average of 133+/-135 days after ICD implantation. The mean number of arrhythmic episodes constituting electrical storm was 17+/-17 (range: 3 to 50; median 8) per patient. In 12 patients, electrical storm required hospital admission. The arrhythmia cluster could be terminated by a combined therapy with beta-blockers and intravenous amiodarone whereas class I antiarrhythmic drugs were only occasionally successful. The cumulative probability of survival as estimated by the Kaplan-Meier method showed that patients with an episode of electrical storm did not have a worse outcome compared to those without such an event. CONCLUSIONS: Electrical storm represents a frequent event in patients treated with modern ICDs. It occurs most commonly late after ICD implantation and can be managed by combined therapy with beta-blockers and amiodarone. Electrical storm does not independently confer increased mortality.

Adult↗
PubMed1998

Intracardiac QRS electrogram width--an arrhythmia detection feature for implantable cardioverter defibrillators: exercise induced variation as a base for device programming.

Delivery of inappropriate therapy of implantable cardioverter defibrillators (ICD) due to inaccurate arrhythmia detection represents a major clinical problem. Different arrhythmia detection criteria such as the "stability" of the cycle length or the suddenness of "onset" of tachycardia have been implemented in ICD software to prevent inappropriate therapy. The new Medtronic model 7223Cx ICD offers an additional detection parameter (QRS width), which reflects changes in the duration of ventricular depolarization as a tool to distinguish supraventricular from ventricular tachycardias. Although this criterion can be programmed based on ECG parameters derived from resting ECGs, this may not be sufficient since QRS width is subject to considerable changes due to transient myocardial ischemia, changes in autonomic tone, or frequency dependent effects of antiarrhythmic drugs. The present study aimed to determine frequency dependent changes in QRS width in individual patients at rest and during symptom-limited exercise testing in 16 patients with documented ventricular tachycardia (N = 13) or ventricular fibrillation (N = 3). The optimal EGM slew threshold and the individual variation of QRS width were determined. Measurements obtained at the end of the implantation procedure were compared to those performed at hospital discharge. The majority of patients showed a wider variation in QRS duration as measured from 30 consecutive cycles during exercise as compared to rest. For example, the QRS range (i.e., the difference between the maximal and the minimal QRS width measured) averaged 7 +/- 3 ms at rest and increased to 11 +/- 3 ms during exercise (P = 0.004) with an increase of > or = 4 ms observed in 11 (69%) of 16 patients. In 13 (81%) of 16 patients a reprogramming of at least one QRS width parameter from its value at the time of implantation was necessary. Thus, the QRS width measured from the intracardiac EGM shows significant intraindividual variations in different physiological conditions. For optimal programming of the QRS width parameter, measurements obtained during exercise are important.

Defibrillators, Implantable↗
PubMed1998

Worldwide clinical experience with a down-sized active can implantable cardioverter defibrillator in 162 consecutive patients. Worldwide 7221 ICD Investigators.

Treatment with an ICD is the first-line treatment for survivors of sudden cardiac death. More recently, evidence accumulates that prophylactic ICD therapy may be beneficial for selected subgroups of patients after myocardial infarction. Particularly for future studies on the value of prophylactic ICD therapy, downsized devices are needed to allow easy pectoral implantation with a single lead configuration and featuring extended memory capabilities. Accordingly, this study assesses the clinical performance of a downsized fourth-generation ICD in 162 consecutive patients. All devices could be successfully implanted pectorally, in 96% with a single lead configuration with a low defibrillation threshold of 10.6 +/- 5.2 J. During a 3-month follow-up, 26% of the patients received ICD therapy. Twenty percent had appropriate therapy for ventricular fibrillation (n = 9) and VT (n = 23), which was effective in all cases. Of the 450 episodes of VT, 426 were terminated by antitachycardia pacing. Fourteen patients (9%) had inappropriate ICD therapy mainly due to atrial fibrillation or sinus tachycardia, which could be reliably diagnosed by the ICD stored intracardiac electrograms.

Adult↗
PubMed1998

T wave alternans as a predictor of recurrent ventricular tachyarrhythmias in ICD recipients: prospective comparison with conventional risk markers.

INTRODUCTION: The current standard for arrhythmic risk stratification is electrophysiologic (EP) testing, which, due to its invasive nature, is limited to patients already known to be at high risk. A number of noninvasive tests, such as determination of left ventricular ejection fraction (LVEF) or heart rate variability, have been evaluated as additional risk stratifiers. Microvolt T wave alternans (TWA) is a promising new risk marker. Prospective evaluation of noninvasive risk markers in low- or moderate-risk populations requires studies involving very large numbers of patients, and in such studies, documentation of the occurrence of ventricular tachyarrhythmias is difficult. In the present study, we identified a high-risk population, recipients of an implantable cardioverter defibrillator (ICD), and prospectively compared microvolt TWA with invasive EP testing and other risk markers with respect to their ability to predict recurrence of ventricular tachyarrhythmias as documented by ICD electrograms. METHODS AND RESULTS: Ninety-five patients with a history of ventricular tachyarrhythmias undergoing implantation of an ICD underwent EP testing, assessment of TWA, as well as determination of LVEF, baroreflex sensitivity, signal-averaged ECG, analysis of 24-hour Holter monitoring, and QT dispersion from the 12-lead surface ECG. The endpoint of the study was first appropriate ICD therapy for electrogram-documented ventricular fibrillation or tachycardia during follow-up. Kaplan-Meier survival analysis revealed that TWA (P < 0.006) and LVEF (P < 0.04) were the only significant univariate risk stratifiers. EP testing was not statistically significant (P < 0.2). Multivariate Cox regression analysis revealed that TWA was the only statistically significant independent risk factor. CONCLUSIONS: Measurement of microvolt TWA compared favorably with both invasive EP testing and other currently used noninvasive risk assessment methods in predicting recurrence of ventricular tachyarrhythmias in ICD recipients. This study suggests that TWA might also be a powerful tool for risk stratification in low- or moderate-risk patients, and needs to be prospectively evaluated in such populations.

Adult↗
PubMed1997

[Combined therapy with transvenous cardioverter/defibrillator and anti-bradycardia pacemaker systems].

Implantable cardioverter/ defibrillators (ICD) represent in many patients with ventricular tachyarrhythmias the first line treatment. Up to 15% of the patients requiring an ICD need concomitant permanent cardiac pacing for bradyarrhythmias resulting in the need of simultaneous ICD- and antibradycardic pacemaker-therapy. We present four patients with successful implantation of a transvenous ICD-system (Medtronic Jewel 7220 and Micro Jewel 7221; electrode: Medtronic 6939), all of which had an antibradycardic pacemaker (2 unipolar, 2 bipolar) implanted prior to ICD-implantation. Meticulous intraoperative testing in order to avoid adverse interactions between the two systems has been carried out successfully in all cases. Possible adverse interactions comprise oversensing of pacemaker signals by the ICD with subsequent inadequate therapy, inhibition of defibrillation therapy during ventricular fibrillation caused by false detection of pacemaker spikes by the ICD as well as reprogramming of the pacemaker after shock delivery. A review of the published literature yielded 91 reported cases of combined ICD- and pacemaker-therapy. In 16% of the patients, one or more of the mentioned complications have been observed. Those occurred more frequently with unipolar than with bipolar pacemaker-systems. Thus, combined therapy with antibradycardic pacemaker and transvenous ICD-systems can be performed safely.

Aged↗
PubMed1997

Heart rate variability used as an arrhythmia risk stratifier after myocardial infarction.

Heart rate variability (HRV) is considered to represent a noninvasive tool to assess cardiac autonomic tone at the level of the sinus node. It has been shown to have predictive power for risk assessment in patients surviving acute myocardial infarction. For this purpose, HRV should be assessed from 24-hour Holter recordings obtained 7-10 days following the infarction. Although there is some recovery of HRV during the first 3 months after infarction, HRV remains reduced in postinfarction patients compared to values obtained in healthy individuals. Compared to assessment of left ventricular function as a risk marker, HRV is superior with respect to prediction of arrhythmic events and sudden death whereas both parameters yield comparative power for prediction of total cardiac mortality. Since the predictive power of HRV analysis alone is relatively low, the combined use of HRV measurements together with traditional risk markers (such as ventricular ectopic beats, signal-averaged ECG, or left ventricular function) results in improved risk prediction with positive predictive accuracy in the range of 30%-50%.

Arrhythmias, Cardiac↗
PubMed1997

T wave alternans during exercise and atrial pacing in humans.

INTRODUCTION: Evidence is accumulating that microvolt T wave alternans (TWA) is a marker of increased risk for ventricular tachyarrhythmias. Initially, atrial pacing was used to elevate heart rate and elicit TWA. More recently, a noninvasive approach has been developed that elevates heart rate using exercise. METHODS AND RESULTS: In 30 consecutive patients with a history of ventricular tachyarrhythmias, the spectral method was used to detect TWA during both atrial pacing and submaximal exercise testing. The concordance rate for the presence or absence of TWA using the two measurement methods was 84%. There was a patient-specific heart rate threshold for the detection of TWA that averaged 100 +/- 14 beats/min during exercise compared with 97 +/- 9 beats/min during right atrial pacing (P = NS). Beyond this threshold, there was a significant and comparable increase in level of TWA with decreasing pacing cycle length and increasing exercise heart rates. CONCLUSIONS: The present study is the first to demonstrate that microvolt TWA can be assessed reliably and noninvasively during exercise stress. There is a patient-specific heart rate threshold beyond which TWA continues to increase with increasing heart rates. Heart rate thresholds for the onset of TWA measured during atrial pacing and exercise stress were comparable, indicating that heart rate alone appears to be the main factor of determining the onset of TWA during submaximal exercise stress.

Adult↗
PubMed1996

Changes in plasma epinephrine concentration and in heart rate during head-up tilt testing in patients with neurocardiogenic syncope: correlation with successful therapy with beta-receptor antagonists.

INTRODUCTION: Tilt table testing is widely used in the management of patients with neurocardiogenic syncope. However, the exact pathophysiologic mechanism of this disorder is still under debate. Likewise, therapy of these patients continues to represent a challenge in many cases. Therefore, the present study aimed to gain further insight into the pathophysiology of this syndrome and to examine easily accessible clinical parameters that can improve therapy selection. METHODS AND RESULTS: In 16 patients with neurocardiogenic syncope, changes in endogenous catecholamine concentrations were determined during repeated tilt table testing before and during treatment with metoprolol. Tachycardia preceded syncope in 8 of 10 responders compared to only 1 of 6 nonresponders (P < 0.05). In responders, the relative increase in epinephrine levels averaged 197% +/- 51% during drug-free tilting and 75% +/- 33% during repeated testing while on beta-blocker therapy (P < 0.05). In nonresponders, there was a smaller relative increase in epinephrine averaging 137% +/- 35% at baseline tilt. During repeated tilt testing, a similar increase was observed in these patients with recurrent syncope (156% +/- 104%; P = NS compared to baseline). CONCLUSION: In patients with neurocardiogenic syncope who show both an increase in epinephrine concentration during tilt test and sinus tachycardia prior to the onset of symptoms, beta-blocker treatment is very effective. These findings confirm the major role of sympathetic activation as a trigger of syncope. Particularly, heart rate changes at the onset of syncope may allow early identification of patients responding to antiadrenergic therapy.

Adrenergic beta-Antagonists↗
PubMed1996

Amiodarone Therapy After Previous Sotalol-induced Torsade de Pointes: Analysis of AT Dispersion to Predict Proarrhythmia.

BACKGROUND: Polymorphic ventricular tachycardia of the torsade de pointes type represents, potentially, the most dangerous side effect of antiarrhythmic drugs that prolong ventricular repolarization. Much effort has been devoted to the identification of the degree of drug-associated QT prolongation that might predict the occurrence of torsade de pointes. However, there is still no general agreement as to which level of QT prolongation might be the harbinger of torsade and which may simply represent the manifestation of the class III antiarrhythmic effect of a given compound. METHODS AND RESULTS: A 70-year-old woman who had survived an episode of cardiac arrest outside of a hospital was treated with dl-sotalol (320 mg/d). After 8 days of therapy, she developed two episodes of hemodynamically unstable torsade de pointes. Sotalol was withdrawn and after extensive diagnostic work, therapy with amiodarone therapy was comparable to that observed during sotalol exposure, the patient tolerated amiodarone and is now free of recurrent ventricular tachyarrhythmias over a follow-up period of 1 year. Analysis of QT dispersion in the surface electrocardiograph revealed a marked increase during sotalol therapy but not during amiodarone administration (77 vs 47 ms). During drug-free control, QT dispersion was 43 ms. CONCLUSIONS: These findings emphasize the potential usefulness of determination of QT dispersion from the surface ECG to assess disparity in ventricular recovery, which is known to favor the occurrence of torsade de pointes. These observations need to be corroborated in large prospective trials. Finally, this case report further emphasizes the low arrhythmogenic potential of amiodarone-an unexplained paradox, the understanding of which might provide insights for the development of newer antifibrillatory compounds.

Journal Article↗
PubMed1996

[Stratification of patients at risk for sudden cardiac death with special reference to the autonomic nervous system].

The autonomic nervous system plays a decisive role in the genesis of sudden cardiac death. During recent years, two noninvasive tests for quantitative assessment of cardiac autonomic tone have become available: analysis of heart rate variability from 24-h ambulatory recordings and determination of baroreflex-sensitivity by means of the phenylephrine method. Numerous experimental and clinical studies suggest that heart rate variability assesses tonic vagal activity whereas baroreflex-sensitivity is considered to reflect phasic or reflex vagal activity. Both methods, however, are not redundant but rather complimentary. An advantage of assessment of baroreflex-sensitivity is represented by the fact that it can be performed under controlled laboratory conditions which yields a good intra- and interindividual comparability of test results. Some retrospective as well as prospective studies have assessed the value of determination of cardiac autonomic tone with respect to risk stratification after myocardial infarction. In general, these studies indicate that the combined assessment of autonomic tone together with left ventricular function yields an improved prediction particularly of the risk of dying due to arrhythmic events. It appears that baroreflex-sensitivity is particularly useful to predict arrhythmic events whereas heart rate variability seems to be linked more to cardiovascular mortality. Preliminary results of the largest prospective study of this kind, the ATRAMI study, indicate that the combined assessment of LVEF and baroreflex-sensitivity considerably improve risk stratification after myocardial infarction. If the final analysis of this trial confirms this, prospective interventional studies should be initiated to evaluate our ability of reducing the risk of sudden death based on noninvasive risk stratification.

Animals↗
PubMed1995

Circadian variation of heart rate variability in postinfarction patients with and without life-threatening ventricular tachyarrhythmias.

INTRODUCTION: Determination of heart rate variability (HRV) is widely used for noninvasive assessment of cardiac autonomic tone. A decreased HRV is associated with an increased mortality in patients surviving an acute myocardial infarction. There are, however, only sparse data about the circadian variation of different components of HRV that may be linked to the well-known circadian fluctuations in the occurrence of sudden death. In addition, the potential prognostic impact of circadian variations of HRV has not been examined. METHODS AND RESULTS: The present study compared the circadian variation of HRV from 14 postinfarction patients who had survived at least one episode of out-of-hospital cardiac arrest (cardiac arrest group) with that of 14 age- and sex-matched patients without a history of malignant arrhythmias after their index infarct (control group). Several time- and frequency-domain measures of HRV were assessed from 24-hour Holter recordings. Circadian variations of high- (HF), low- (LF), and total-frequency (TF) components were determined by calculating for each parameter the hourly difference from the day's mean. The average of these differences was calculated for every hour as well as for predefined day and night periods. There was no significant difference between the two groups with regard to HRV indices that predominantly reflect vagal tone, such as SDNN (78 +/- 25 vs 96 +/- 24 msec), pNN50 (2.7% +/- 4.6% vs 4.9% +/- 4.2%), or HF (6.3 +/- 3.0 vs 7.8 +/- 3.2 msec; cardiac arrest vs control group). There was also no significant difference in the circadian variation of LF or TF between the two groups during daytime and nighttime. However, a significant difference in circadian variation of HF was found during daytime (0.02 +/- 0.5 vs -0.6 +/- 0.5 msec; P = 0.006) and nighttime (0.19 +/- 0.64 vs 1.5 +/- 0.75 msec; P = 0.0002). In cardiac arrest survivors, there was no difference in the mean deviation of HF between the day- and the nighttime periods. CONCLUSIONS: These results show an almost complete abolition in circadian variation of parasympathetic tone in postinfarction patients surviving an episode of out-of-hospital cardiac arrest, whereas circadian variation of sympathetic tone is comparable to that of postinfarction patients without arrhythmic episodes. These findings indicate that determination of diurnal variation of HRV may add to the prognostic value of HRV with respect to identifying patients at high risk of sudden death.

Autonomic Nervous System↗
PubMed1995

[Neurocardiac syncope: pathophysiology, diagnosis, therapy].

The diagnostic work-up and the appropriate therapy of patients with recurrent syncopy represents an often encountered clinical problem. The underlying etiology of a syncopal episode remains not infrequently unknown despite intensive and sometimes costly diagnostic procedures. Particularly in young patients with syncopal attacks, the diagnosis of neurocardiogenic syncope has been established on the basis of normal findings during conventional cardiologic and neurologic work-up. Only since the introduction of the tilt-table test into clinical practice has the clinician had a diagnostic tool to prove the neurocardiogenic etiology of a syncopal episode. It has been demonstrated that this diagnostic method yields a good reproducibility which makes it suitable to assess the efficacy of therapeutic interventions. There have been several therapeutic recommendations according to the multifactorial pathogenesis of neurocardiogenic syncope. Among these, therapy with beta-receptor blocking agents or with theophylline appears to be the most promising treatment modalities. The results obtained in the studies reviewed in the present article have increased our knowledge with respect to the pathogenesis of neurocardiogenic syncope as well as the diagnostic procedures and treatment modalities in patients afflicted with this disorder.

Adrenergic beta-Antagonists↗
PubMed1994

Amiodarone-associated proarrhythmic effects. A review with special reference to torsade de pointes tachycardia.

PURPOSE: To assess the incidence of amiodarone-mediated aggravation of ventricular tachyarrhythmias or the development of new arrhythmias, such as torsade de pointes, in patients with cardiac disease. DATA SOURCES AND STUDY SELECTION: A MEDLINE literature search was done to identify articles published during the last 20 years that presented data on amiodarone-associated proarrhythmic events. The articles were divided into three categories: case reports, uncontrolled retrospective studies, and prospective controlled trials. In addition, articles were identified that examined the effects of amiodarone in patients with previously documented drug-induced torsade de pointes. RESULTS: 65 English-language case reports dealing with torsade de pointes during amiodarone therapy were found in the literature. In many of these cases, other predisposing factors for the development of torsade de pointes were reported. Seventeen studies each reported data from at least 50 patients who were treated with amiodarone for at least 6 months. Of 2878 patients included in these trials, 57 were reported to have a proarrhythmic event while exposed to the drug (an overall incidence of 2%). Torsade de pointes was observed in one third of these patients (an overall incidence of 0.7%). In seven placebo-controlled trials in which the drug was given as monotherapy, amiodarone was not associated with the development of a proarrhythmic event in any patient. Finally, in three reports, 31 patients with previous drug-mediated torsade de pointes were exposed to amiodarone during short- and long-term therapy. In none of these patients did a recurrent episode of torsade de pointes develop, despite the amiodarone-induced prolongation of the QTc interval, which was equivalent to that observed at the time of torsade de pointes during exposure to previous drugs. CONCLUSIONS: Amiodarone appears to be associated with a remarkably low frequency of proarrhythmic events and an incidence of torsade de pointes of less than 1.0%. This low arrhythmogenicity and the negligible negative inotropic effect of the compound constitute properties that make amiodarone particularly useful in treating high-risk patients prone to sudden cardiac death. Its potential to reduce this risk is currently being evaluated in several large prospective trials.

Amiodarone↗