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Biomedical subjects

S H Hohnloser

Publications and source records attributed to S H Hohnloser.

At least 19 recordsLinked to original sources
PubMed2003

T-wave alternans negative coronary patients with low ejection and benefit from defibrillator implantation.

In a trial of prophylactic implantation of a defibrillator, a mortality benefit was seen among patients with previous myocardial infarction and a left-ventricular ejection fraction of 0.30 or less. We identified 129 similar patients from two previously published clinical trials in which microvolt T-wave alternans testing was prospectively assessed. At 24 months of follow-up, no sudden cardiac death or cardiac arrest was seen among patients who tested T-wave alternans negative, compared with an event rate of 15.6% among the remaining patients. Testing of T-wave alternans seems to identify patients who are at low risk of ventricular tachyarrhythmic event and who may not benefit from defibrillator therapy.

Death, Sudden, Cardiac↗
PubMed2003

Prediction of early recurrence of atrial fibrillation after external cardioversion by means of P wave signal-averaged electrocardiogram.

BACKGROUND: Therapy of atrial fibrillation by electrical cardioversion (CV) is limited by the high rate of recurrences. Early recurrence of atrial fibrillation (ERAF) occurs in a subgroup of patients whose characteristics are poorly defined. This prospective study was performed to evaluate if the P wave signal-averaged ECG (PSAECG) is able to identify patients with an increased risk of ERAF after CV. METHODS: Patients with an indication for elective external CV were enrolled. After successful CV, PSAECGs were recorded at 0.5, 1, 24 h and 1 week. The ability of PSAECG parameters (signal-averaged P wave duration, PWD; root-mean-square of the voltage of the terminal 20, 30, and 40 ms of the signal-averaged P wave; RMS20, RMS30, RMS40) to predict ERAF (prospectively defined as AF recurrence within 4 h after CV) was assessed. RESULTS: Of 111 consecutive patients, 7 experienced ERAF, 30 patients had AF recurrence later during the 1-week follow-up. Patients with ERAF had a significantly prolonged signal-averaged PWD compared to patients who remained in SR (194+/-16 ms vs 139+/-3 ms at 0.5 h, p<0.001). As ROC analysis revealed, a PWD >/=154 ms at 30 min after CV had the highest predictive accuracy for ERAF (sensitivity 100%, specificity 82%, positive predictive value 33%, negative predictive value 100%). Other parameters of the PSAECG did not reveal significant differences between patients with and without ERAF. CONCLUSIONS: The PSAECG provides a sensitive noninvasive tool for detection of patients at risk of ERAF. Thus identified, tailored pharmacological therapy is conceivable to prevent ERAF.

Aged↗
PubMed2002

Relationship between clinical and echocardiography-derived parameters and atrial activation as measured by the P-wave signal-averaged electrocardiogram.

UNLABELLED: P-wave signal averaging is used in an attempt to detect patients at risk of atrial arrhythmias, particularly atrial fibrillation. Although many studies utilized this method, data on the relationship between clinical and echocardiographic variables and signal averaged P-wave parameters are sparse. Thus, we performed a prospective study to evaluate the influence of important clinical and echocardiographic variables on P-wave parameters. The study included 100 probands without demonstrable cardiac disease. P-wave signal averaging was performed after echocardiographic examination in all subjects. Overall P-wave duration averaged 122 +/- 16 ms and correlated significantly with age, left atrial and left ventricular end-diastolic diameter on univariate analysis (r = 0.287, 0.393 and 0.375; p = 0.004, < 0.0001 and < 0.0001, respectively). On multivariate analysis, however, age was the only independent factor affecting signal averaged P-wave duration (p = 0.02). There were statistically significant differences in left atrial size and P-wave duration if probands were grouped according to their age. CONCLUSION: There is a significant relationship between signal averaged P-wave duration and age. This may be due to increased atrial fibrosis in elderly subjects. These data should be considered when signal-averaged P wave duration is used as a risk stratifier in patients prone to atrial fibrillation.

Adult↗
PubMed2001

Baroreflex sensitivity and heart rate variability in the identification of patients at risk for life-threatening arrhythmias: implications for clinical trials.

BACKGROUND: The need for accurate risk stratification is heightened by the expanding indications for the implantable cardioverter defibrillator. The Multicenter Automatic Defibrillator Implantation Trial (MADIT) focused interest on patients with both depressed left ventricular ejection fraction (LVEF) and the presence of nonsustained ventricular tachycardia (NSVT). Meanwhile, the prospective study Autonomic Tone and Reflexes After Myocardial Infarctio (ATRAMI) demonstrated that markers of reduced vagal activity, such as depressed baroreflex sensitivity (BRS) an heart rate variability (HRV), are strong predictors of cardiac mortality after myocardial infarction. METHODS AND RESULTS: We analyzed 1071 ATRAMI patients after myocardial infarction who had data on LVEF, 24-hour ECG recording, and BRS. During follow-up (21 +/- 8 months), 43 patients experienced cardiac death, 5 patients had episodes of sustained VT, and 30 patients experienced sudden death and/or sustained VT. NSVT, depressed BRS, or HRV were all significantly and independently associated with increased mortality. The combination of all 3 risk factor increased the risk of death by 22x. Among patients with LVEF<35%, despite the absence of NSVT, depressed BRS predicted higher mortality (18% versus 4.6%, P = 0.01). This is a clinically important finding because this grou constitutes 25% of all patients with depressed LVEF. For both cardiac and arrhythmic mortality, the sensitivity of lo BRS was higher than that of NSVT and HRV CONCLUSIONS: BRS and HRV contribute importantly and additionally to risk stratification. Particularly when LVEF is depressed, the analysis of BRS identifies a large number of patients at high risk for cardiac and arrhythmic mortalit who might benefit from implantable cardioverter defibrillator therapy without disproportionately increasing the number of false-positives.

Arrhythmias, Cardiac↗
PubMed2001

[P-wave signal averaging-ECG: normal values and reproducibility].

Signal averaging techniques are used for detection of low amplitude, high frequency signals in the surface ECG. P-wave signal-averaging has been used to predict the risk for development of atrial tachyarrhythmias in patients with structural heart disease. There is, however, a lack of prospective studies evaluating normal values of the P-wave signal-averaged ECG in healthy individuals. Moreover, day-to-day reproducibility of results of P-wave signal-averaging is not precisely known. Thus, the aim of this study was to determine normal values and reproducibility of time-domain P-wave signal-averaging in a large cohort of healthy volunteers. A commercially available device (MAC 5000, Marquette Hellige) was used for signal-averaging. A vector magnitude was calculated from Frank's orthogonal leads after P-waves were sampled and filtered with a spectral filter using fast fourier transform. We examined 123 volunteers without cardiovascular disease at two occasions. Mean P-wave duration was 114 +/- 13 ms for the overall study population. There was a slight but statistically significant increase in filtered P-wave duration with age (r = 0.32, p < 0.001). All values were reliably reproducible upon the second examination (r = 0.624 to 0.706, p < 0.0001). These results may serve as a future reference to other studies examining patients with structural heart disease.

Adult↗
PubMed2001

What do implantable cardioverter/defibrillators teach us about the mechanisms of sudden cardiac death?

Almost two decades of experience with the ICD have resulted in a better understanding of the nature of life-threatening ventricular tachyarrhythmias. The most pertinent achievements in this respect stem from clinical follow-up observations in patients with important clinical entities such as dilated cardiomyopathy or the Brugada syndrome. For instance, patients with dilated cardiomyopathy presenting with syncope and a negative electrophysiological study have been shown to have a high incidence of appropriate usage of their ICD. On the other hand, relative little has been gained from the extensive electrogram storage capabilities of third and fourth generation ICDs. Basically, careful evaluation of these electrograms has confirmed previous anecdotal data obtained from analysis of Holter recordings of patients who died suddenly while wearing the ECG recorder. In most instances, VT/VF episodes are triggered by relatively late-coupled premature beats whereas short--long--short sequences have been observed only in few patients. One future research avenue concerns the more detailed analysis of changes in cardiac autonomic tone preceding the occurrence of sustained ventricular tachyarrhythmias which can be assessed from the electrogram storage of the ICD.

Arrhythmias, Cardiac↗
PubMed2001

Prevalence, characteristics and clinical implications of regular atrial tachyarrhythmias in patients with atrial fibrillation: insights from a study using a new implantable device.

OBJECTIVES: This study prospectively analyzed atrial tachyarrhythmia (AT) organization and antitachycardia pacing (ATP) success in patients with an implanted device for AT therapy. BACKGROUND: In patients with atrial fibrillation (AF), the incidence of regular, slow ATs amendable by ATP is unknown. METHODS: Forty patients with previously documented AT (70% with AF) received a new pacemaker with atrial electrogram (AEG) storage and atrial ATP capabilities for standard pacing indications. The AEGs acquired during the first month (study phase 1) were classified into high (type I), intermediate (type II) and low (type III) degrees of organization. Atrial ATP was then activated, and treated AT episodes were retrieved three and six months after implantation (study phase 2). RESULTS: Of 824 AEGs retrieved before ATP activation (study phase 1), 351 (43%) were classified as type 1, 47% as type II and 10% as type III. Episodes of AT starting as type I (35%) and type II or III (65%) maintained their type over 1 min in 73%. All patients with an exclusive history of AF also showed type I AEGs. In 361 subsequently treated AT episodes (study phase 2), ATP was successful in 62% of type I and 34% of type II episodes, but not in type III (p < 0.0001). CONCLUSIONS: The majority of patients with a history of AF show not only disorganized but also highly organized AT episodes, which can be successfully terminated by ATP.

Aged↗
PubMed2001

Effect of metoprolol and d,l-sotalol on microvolt-level T-wave alternans. Results of a prospective, double-blind, randomized study.

OBJECTIVES: The study evaluated the effects of metoprolol, a pure beta-blocker, and d,l-sotalol, a beta-blocker with additional class III antiarrhythmic effects, on microvolt-level T-wave alternans (TWA). BACKGROUND: Assessment of TWA is increasingly used for purposes of risk stratification in patients prone to sudden death. There are only sparse data regarding the effects of beta-blockers and antiarrhythmic drugs on TWA. METHODS: Patients with a history of documented or suspected malignant ventricular tachyarrhythmias were eligible. All patients underwent invasive electrophysiologic (EP) testing including programmed ventricular stimulation and determination of TWA at increasing heart rates using atrial pacing. Reproducibility of TWA at two consecutive drug-free baseline measurements was tested in a random patient subset. Following baseline measurements, all patients were randomized either to double-blind intravenous infusion of sotalol (1.0 mg/kg) or metoprolol (0.1 mg/kg). Results of TWA assessment at baseline and after drug exposure were compared. RESULTS: Fifty-four consecutive patients were studied. In 12 patients, repetitive baseline measurement of TWA revealed stable alternans voltage (V(alt)) values (9.1 +/- 5.8 microV vs. 8.5 +/- 5.7 microV, p = NS). After drug administration, V(alt) decreased by 35% with metoprolol (7.9 +/- 6.0 microV to 4.9 +/- 4.2 microV; p < 0.001) and by 38% with sotalol (8.6 +/- 6.8 microV to 4.4 +/- 2.3 microV; p = 0.001). In eight patients with positive TWA at baseline, repeated measurement revealed negative test results. CONCLUSIONS: In patients prone to sudden cardiac death, there is a reduction in TWA amplitude following the administration of antiadrenergic drugs. This result indicates that TWA is responsive to the pharmacologic milieu and suggests that, to assess a patient's risk of spontaneous ventricular arrhythmia, the patient should be tested while maintaining the pharmacologic regimen under which the risk of arrhythmia is being assessed. This applies particularly for beta-blocker therapy.

Adrenergic beta-Antagonists↗
PubMed2001

Discrimination between ventricular and supraventricular tachycardia by dual chamber cardioverter defibrillators: importance of the atrial sensing function.

Although the addition of atrial sensing in dual chamber ICDs may improve the ability of the device to discriminate between supraventricular (SVT) and ventricular tachycardia (VT), atrial sensing errors may also negatively affect tachycardia classification. This prospective study evaluated the incidence of atrial sensing errors in a dual chamber ICD and their impact on VT/SVT discrimination. In 145 patients, a dual chamber ICD (Defender) was implanted. Analysis of 1,241 tachycardia episodes stored during a mean follow-up of 14+/-8 months revealed atrial sensing errors in 817 (66%) episodes. Upon expert review, device-based classification was confirmed in 509 (98%) of 522 SVT episodes. No false device-based SVT classification was related to atrial sensing errors. Of 719 episodes classified as VT by the device, 645 (90%) were confirmed. There were 74 episodes of false-positive VT detection. Of these, 63 were related to atrial sensing errors: atrial undersensing in 58 (92%) and atrial oversensing in 5 (8%) episodes. Atrial sensing errors led to incorrect VT/SVT discrimination in 51 (4%) of 1,241 episodes. Only the occurrence of paroxysmal atrial fibrillation and abdominal site of device implantation showed a significant influence on false VT/SVT discrimination. Atrial sensing errors are frequently encountered in dual chamber ICDs. Due to the VT/SVT discrimination algorithm, atrial sensing errors only led to misclassification in 4 % of all episodes, mainly due to atrial undersensing. No VT underdetection due to atrial oversensing occurred.

Algorithms↗
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

Pace-termination and pacing for prevention of atrial tachyarrhythmias: results from a multicenter study with an implantable device for atrial therapy.

INTRODUCTION: Patients with bradycardia requiring permanent pacing frequently suffer from additional atrial tachyarrhythmias (ATs). This study evaluated the safety and efficacy of atrial antitachycardia pacing (ATP) and the performance of pacing for AT prevention implemented into a new pacemaker. METHODS AND RESULTS: In patients with conventional indications for permanent pacing, an investigational DDDRP pacemaker (Medtronic AT500, model 7253) was implanted. The primary study objectives were to determine the safety of overall device functioning and its efficacy in terminating spontaneous AT. A secondary endpoint was to determine the reliability of AT detection. Pacemaker memory functions were used to analyze the impact of dedicated pacing algorithms on AT prevention. In 33 European and Canadian centers, 325 patients were enrolled (mean follow-up 2.3+/-1.3 months). Complication-free survival at 3 months was 88%. In 2,145 episodes stored with atrial electrograms, AT detection was confirmed in 97%. The algorithm for continuous overdrive pacing increased the percentage of atrial pacing to 97%. After ATP activation, 16,683 of 52,468 AT episodes were treated (120 patients). Of these, 8,903 episodes (53%) were terminated successfully by ATP. No proarrhythmic effect of preventive pacing or atrial ATP was observed. Preventive pacing algorithms increased the median percentage of atrial pacing from 62% to 97%. However, the number of AT/AF (atrial fibrillation) episodes (4.1 vs 4.1 per patient per day) and the time in AT/AF (13.7% vs 12.8%) was not significantly different before and after activation of preventive pacing. CONCLUSION: DDDRP pacing with a new system for AT therapy was safe and associated with successful pace-termination of AT in 53% of episodes. Preventive pacing and atrial ATP algorithms represent two new functions that can be implemented safely into pacemaker systems for nonpharmacologic treatment of ATs in patients requiring pacemaker therapy.

Adolescent↗
PubMed2001

Risk of development of delayed atrioventricular block after slow pathway modification in patients with atrioventricular nodal reentrant tachycardia and a pre-existing prolonged PR interval.

AIMS: The objective of this prospective study was to assess risk factors for the development of atrioventricular block following slow pathway modification in patients with atrioventricular nodal reentrant tachycardia and a pre-existing prolonged PR interval. METHODS AND RESULTS: Of 346 consecutive patients with atrioventricular nodal reentrant tachycardia undergoing slow pathway modification, 18 patients (62 +/- 7 years; five females) were found to have a prolonged PR interval prior to ablation. Total elimination of the functional slow pathway was assumed if the antegrade effective refractory period following slow pathway modification was longer than the cycle length of atrioventricular nodal reentrant tachycardia. To detect atrioventricular node conduction disturbances, 24-h Holter recordings were performed 1 day prior to slow pathway modification, and 1 day, 1 week, 1, 3 and 6 months after the procedure. Six patients developed late atrioventricular block. The incidence of delayed atrioventricular block following successful slow pathway modification was higher in patients with, compared to patients without, prolonged PR interval at baseline (6/18 vs 0/328, P < .001). In the former group, the antegrade effective refractory period was longer in patients with, compared to those without, a delayed atrioventricular block (492 +/- 150 ms vs 332 +/- 101 ms, P < 0.05). The incidence of delayed atrioventricular block was higher in patients with total elimination of the slow pathway compared to patients without (5/7 vs 1/11, P < 0.01). CONCLUSIONS: Slow pathway modification in patients with atrioventricular nodal reentrant tachycardia and a prolonged PR interval is highly effective. However, there is a significant risk of development of delayed atrioventricular block, particularly when the procedure results in total elimination of the slow pathway.

Case-Control Studies↗
PubMed2001

Predictors of medical events and of their competitive interactions in the Cardiac Insufficiency Bisoprolol Study 2 (CIBIS-2).

AIMS: Predictive factors for medical events and interactions between events were not reported in the Cardiac Insufficiency Bisoprolol Study 2 (CIBIS-2). We examined the interactions among death, permanent treatment withdrawals, nonlethal cardiovascular hospitalizations and their own occurrence in a given patient, the treatment received, and baseline variables during CIBIS-2. METHODS AND RESULTS: A Cox model for censored data was used to analyze the relations among baseline variables, medical events, and their interactions with treatment. We used competitive risk analysis to examine the interactions between successive events in a given patient during follow-up. No baseline variable predicted the reduction of mortality with bisoprolol. Withdrawal from bisoprolol therapy was more frequent in patients whose baseline heart rate was in the lower tertile of the distribution (P =.0002) but otherwise was not different between patients randomized to bisoprolol and to placebo. Event history analysis revealed that bisoprolol reduced mortality (P =.0006) and hospitalizations for nonlethal cardiovascular events (P =.003) in patients in whom treatment was not permanently withdrawn. Analysis of survival curves in patients who permanently discontinued treatment showed that bisoprolol did not reduce mortality compared with placebo in this population (relative risk 1.03, 95% CI 0.67-1.59; P =.88). Recurrent nonlethal events were reduced by bisoprolol. CONCLUSION: In CIBIS-2, medical events were significantly influenced by treatment withdrawal. Patients who derive benefit from bisoprolol therapy are those in whom treatment is not permanently withdrawn.

Adrenergic beta-Antagonists↗
PubMed2001

Torsade de pointes tachycardia as a rare manifestation of acute enteroviral myocarditis.

A patient with cardiac arrest and documented torsade de pointes ventricular tachycardia is presented in whom acute coxsackievirus B2 myocarditis was identified as the most likely underlying cardiac condition. This case shows that torsade de pointes may occur as a rare manifestation of viral myocarditis. Serial serological tests and endomyocardial biopsies may be helpful in establishing a diagnosis in such patients.

Acute Disease↗