Thomas Kleemann
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Thomas Kleemann has a total of 57 co-authors. Here are the top co-authors by number of shared publications:
- Jochen Senges
Stiftung Institut für Herzinfarktforschung (IHF), 67063 Ludwigshafen, Germany
3 shared publications - Johannes Brachmann
Department of Cardiology, Angiology and Pulmonology, Klinikum Coburg, 96450 Coburg, Germany
2 shared publications - Lars Eckardt
University Hospital, Münster, Germany
2 shared publications - Matthias Hochadel
Stiftung Institut für Herzinfarktforschung (IHF), Ludwigshafen, Germany
2 shared publications - Ralf Zahn
Medizinische Klinik B, Klinikum der Stadt Ludwigshafen am Rhein Gemeinnützige GmbH, Heart Centre Ludwigshafen, Ludwigshafen, Germany
2 shared publications - Tim Süselbeck
Clinic of Cardiology, Kardiologische Praxisklinik Ludwigshafen, Ludwig-Guttmann-Straße 11, 67071 Ludwigshafen
2 shared publications
Latest Publications
- Open Access
- 27 November 2025
- Published by Springer Nature in Herz
- Vol. 50 (6) , 405-406
Neue Entwicklungen in der kardialen Device-Therapie
- 27 November 2025
- Published by Springer Nature in Herz
- Vol. 50 (6) , 405-406
Open AccessNeue Entwicklungen in der kardialen Device-Therapie
- Open Access
- 10 February 2025
- Published by MDPI AG in Journal of Clinical Medicine
- Vol. 14 (4) , 1137
Pacemaker Versus Defibrillator Therapy in Patients Eligible for Cardiac Resynchronisation Therapy: Evidence from the German Device Registry
Background: According to current guidelines, cardiac resynchronisation therapy (CRT) is recommended in patients with significantly impaired left ventricular systolic function and left bundle branch block. However, the decision between pacemaker (CRT-P) and defibrillator (CRT-D) in patients eligible for CRT remains a matter of debate. Register data have shown a higher all-cause mortality in CRT-P in comparison to patients with a CRT-D. Here, we investigated clinical determinants of the selection of CRT-P vs. CRT-D and clinical outcome in large registry data from a multi-centre ‘real-life’ registry on patients with CRT defibrillator or pacemaker therapy. Methods: The German Device Registry (DEVICE) is a nationwide, prospective registry with one-year follow-up investigating 5451 patients receiving device implantations in 50 German centres. The present analysis of DEVICE focused on all patients from the register receiving cardiac resynchronization therapy. Results: Out of 1603 patients receiving cardiac resynchronisation therapy, 1536 (95.8%) received a CRT defibrillator system and 67 (4.2%) a CRT pacemaker system. Patients in the CRT-P group had a significantly better left ventricular systolic function compared to the CRT-D group (median 35% vs. 25%), and significantly less often had a history of myocardial infarction (9.0% vs. 25.2%). A preexisting pacemaker and a history of stroke/peripheral embolism were identified as determinants for the selection of CRT-P vs. CRT-D. Overall mortality after one-year follow-up was 8.0%. Patients with ischemic cardiomyopathy receiving CRT-P therapy had a higher one-year mortality than patients receiving CRT-D (21.2% vs. 8.9%, p = 0.020). On the other hand, patients with non-ischemic cardiomyopathy did not display differences between these two treatment groups (CRT-P 8.1%, CRT-D 6.6%, p = 0.72). Conclusions: Data from the German device registry show that most patients receiving cardiac synchronization therapy have an implanted CRT-D system. In comparison to patients with CRT-D, those with CRT-P more often had a non-ischemic cardiomyopathy and a preexisting pacemaker system. The outcomes between these two treatment groups were different as regards ischemic cardiomyopathy only.
- 10 February 2025
- Published by MDPI AG in Journal of Clinical Medicine
- Vol. 14 (4) , 1137
Open AccessPacemaker Versus Defibrillator Therapy in Patients Eligible for Cardiac Resynchronisation Therapy: Evidence from the German Device Registry
Background: According to current guidelines, cardiac resynchronisation therapy (CRT) is recommended in patients with significantly impaired left ventricular systolic function and left bundle branch block. However, the decision between pacemaker (CRT-P) and defibrillator (CRT-D) in patients eligible for CRT remains a matter of debate. Register data have shown a higher all-cause mortality in CRT-P in comparison to patients with a CRT-D. Here, we investigated clinical determinants of the selection of CRT-P vs. CRT-D and clinical outcome in large registry data from a multi-centre ‘real-life’ registry on patients with CRT defibrillator or pacemaker therapy. Methods: The German Device Registry (DEVICE) is a nationwide, prospective registry with one-year follow-up investigating 5451 patients receiving device implantations in 50 German centres. The present analysis of DEVICE focused on all patients from the register receiving cardiac resynchronization therapy. Results: Out of 1603 patients receiving cardiac resynchronisation therapy, 1536 (95.8%) received a CRT defibrillator system and 67 (4.2%) a CRT pacemaker system. Patients in the CRT-P group had a significantly better left ventricular systolic function compared to the CRT-D group (median 35% vs. 25%), and significantly less often had a history of myocardial infarction (9.0% vs. 25.2%). A preexisting pacemaker and a history of stroke/peripheral embolism were identified as determinants for the selection of CRT-P vs. CRT-D. Overall mortality after one-year follow-up was 8.0%. Patients with ischemic cardiomyopathy receiving CRT-P therapy had a higher one-year mortality than patients receiving CRT-D (21.2% vs. 8.9%, p = 0.020). On the other hand, patients with non-ischemic cardiomyopathy did not display differences between these two treatment groups (CRT-P 8.1%, CRT-D 6.6%, p = 0.72). Conclusions: Data from the German device registry show that most patients receiving cardiac synchronization therapy have an implanted CRT-D system. In comparison to patients with CRT-D, those with CRT-P more often had a non-ischemic cardiomyopathy and a preexisting pacemaker system. The outcomes between these two treatment groups were different as regards ischemic cardiomyopathy only.
- 26 November 2024
- Published by Springer Nature in American Journal of Cardiovascular Drugs
- Vol. 25 (2) , 287-291
Impact of Renal Function Estimation Formulae on Use and Correct Dosing of NOACs in Patients with Non-valvular Atrial Fibrillation in Real Life in Germany
- 26 November 2024
- Published by Springer Nature in American Journal of Cardiovascular Drugs
- Vol. 25 (2) , 287-291
Impact of Renal Function Estimation Formulae on Use and Correct Dosing of NOACs in Patients with Non-valvular Atrial Fibrillation in Real Life in Germany
- Open Access
- 30 June 2024
- Published by MDPI AG in Journal of Clinical Medicine
- Vol. 13 (13) , 3858
Procedural Outcome and 1-Year Follow-Up of Young Patients Undergoing Implantable Cardioverter–Defibrillator Implantation—Insights from the German DEVICE I+II Registry
Background: The number of young patients receiving ICDs or CRT-Ds has been increasing in recent decades and understanding the key characteristics of this special population is paramount to optimized patient care. Methods: The DEVICE I+II registry prospectively enrolled patients undergoing ICD/CRT-D implantation or revision from 50 German centers between 2007 and 2014 Data on patient characteristics, procedural outcome, adverse events, and mortality during the initial stay and 1-year follow-up were collected. All patients under the age of 45 years were identified and included in a comparative analysis with the remaining population. Results: A total number of 5313 patients were enrolled into the registry, of which 339 patients (6.4%) were under the age of 45 years. Mean age was 35.0 ± 8.2 vs. 67.5 ± 9.7 years, compared to older patients (≥45 years). Young patients were more likely to receive an ICD (90.9 vs. 69.9%, p < 0.001) than a CRT-D device (9.1 vs. 30.1%). Coronary artery disease was less common in younger patients (13.6 vs. 63.9%, p < 0.001), whereas hypertrophic cardiomyopathy (10.9 vs. 2.7%, p < 0.001) and primary cardiac electrical diseases (11.2 vs. 1.5%, p < 0.001) were encountered more often. Secondary preventive ICD was more common in younger patients (51.6 vs. 39.9%, p < 0.001). Among those patients, survival of sudden cardiac death (66.7 vs. 45.4%, p < 0.001) due to ventricular fibrillation (60.6 vs. 37.9%, p < 0.001) was the leading cause for admission. There were no detectable differences in postoperative complications requiring intervention (1.5 vs. 1.9%, p = 0.68) or in-hospital mortality (0.0 vs. 0.3%, p = 0.62). Median follow-up duration was 17.9 [13.4–22.9] vs. 16.9 [13.1–23.1] months (p = 0.13). In younger patients, device-associated complications requiring revision were more common (14.1 vs. 8.3%, p < 0.001) and all-cause 1-year-mortality after implantation was lower (2.9 vs. 7.3%, p = 0.003; HR 0.39, 95%CI: 0.2–0.75) than in older patients. Conclusions: Young patients < 45 years of age received defibrillator therapy more often for secondary prevention. Rates for periprocedural complications and in-hospital mortality were very low and without differences between groups. Young patients have lower mortality during follow-up but experienced a higher rate of postoperative complications requiring revision, potentially due to a more active lifestyle.
- 30 June 2024
- Published by MDPI AG in Journal of Clinical Medicine
- Vol. 13 (13) , 3858
Open AccessProcedural Outcome and 1-Year Follow-Up of Young Patients Undergoing Implantable Cardioverter–Defibrillator Implantation—Insights from the German DEVICE I+II Registry
Background: The number of young patients receiving ICDs or CRT-Ds has been increasing in recent decades and understanding the key characteristics of this special population is paramount to optimized patient care. Methods: The DEVICE I+II registry prospectively enrolled patients undergoing ICD/CRT-D implantation or revision from 50 German centers between 2007 and 2014 Data on patient characteristics, procedural outcome, adverse events, and mortality during the initial stay and 1-year follow-up were collected. All patients under the age of 45 years were identified and included in a comparative analysis with the remaining population. Results: A total number of 5313 patients were enrolled into the registry, of which 339 patients (6.4%) were under the age of 45 years. Mean age was 35.0 ± 8.2 vs. 67.5 ± 9.7 years, compared to older patients (≥45 years). Young patients were more likely to receive an ICD (90.9 vs. 69.9%, p < 0.001) than a CRT-D device (9.1 vs. 30.1%). Coronary artery disease was less common in younger patients (13.6 vs. 63.9%, p < 0.001), whereas hypertrophic cardiomyopathy (10.9 vs. 2.7%, p < 0.001) and primary cardiac electrical diseases (11.2 vs. 1.5%, p < 0.001) were encountered more often. Secondary preventive ICD was more common in younger patients (51.6 vs. 39.9%, p < 0.001). Among those patients, survival of sudden cardiac death (66.7 vs. 45.4%, p < 0.001) due to ventricular fibrillation (60.6 vs. 37.9%, p < 0.001) was the leading cause for admission. There were no detectable differences in postoperative complications requiring intervention (1.5 vs. 1.9%, p = 0.68) or in-hospital mortality (0.0 vs. 0.3%, p = 0.62). Median follow-up duration was 17.9 [13.4–22.9] vs. 16.9 [13.1–23.1] months (p = 0.13). In younger patients, device-associated complications requiring revision were more common (14.1 vs. 8.3%, p < 0.001) and all-cause 1-year-mortality after implantation was lower (2.9 vs. 7.3%, p = 0.003; HR 0.39, 95%CI: 0.2–0.75) than in older patients. Conclusions: Young patients < 45 years of age received defibrillator therapy more often for secondary prevention. Rates for periprocedural complications and in-hospital mortality were very low and without differences between groups. Young patients have lower mortality during follow-up but experienced a higher rate of postoperative complications requiring revision, potentially due to a more active lifestyle.
- Open Access
- 21 February 2022
- Published by MDPI AG in Journal of Clinical Medicine
- Vol. 11 (4) , 1140
Symptom Severity and Health-Related Quality of Life in Patients with Atrial Fibrillation: Findings from the Observational ARENA Study
Background: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and is associated with impaired health-related quality of life (HRQoL), high symptom severity, and poor cardiovascular outcomes. Both clinical and psychological factors may contribute to symptom severity and HRQoL in AF. Methods: Using data from the observational Atrial Fibrillation Rhine-Neckar Region (ARENA) trial, we identified medical and psychosocial factors associated with AF-related symptom severity using European Heart Rhythm Association symptom classification and HRQoL using 5-level EuroQoL- 5D. Results: In 1218 AF patients (mean age 71.1 ± 10.5 years, 34.5% female), female sex (OR 3.7, p < 0.001), preexisting coronary artery disease (CAD) (OR 1.7, p = 0.020), a history of cardioversion (OR 1.4, p = 0.041), cardiac anxiety (OR 1.2; p < 0.001), stress from noise (OR 1.4, p = 0.005), work-related stress (OR 1.3, p = 0.026), and sleep disturbance (OR 1.2, p = 0.016) were associated with higher AF-related symptom severity. CAD (β = −0.23, p = 0.001), diabetes mellitus (β = −0.25, p < 0.001), generalized anxiety (β = −0.30, p < 0.001), cardiac anxiety (β = −0.16, p < 0.001), financial stress (β = −0.11, p < 0.001), and sleep disturbance (β = 0.11, p < 0.001) were associated with impaired HRQoL. Conclusions: Psychological characteristics, preexisting CAD, and diabetes may play an important role in the identification of individuals at highest risk for impaired HRQoL and high symptom severity in patients with AF.
- 21 February 2022
- Published by MDPI AG in Journal of Clinical Medicine
- Vol. 11 (4) , 1140
Open AccessSymptom Severity and Health-Related Quality of Life in Patients with Atrial Fibrillation: Findings from the Observational ARENA Study
Background: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and is associated with impaired health-related quality of life (HRQoL), high symptom severity, and poor cardiovascular outcomes. Both clinical and psychological factors may contribute to symptom severity and HRQoL in AF. Methods: Using data from the observational Atrial Fibrillation Rhine-Neckar Region (ARENA) trial, we identified medical and psychosocial factors associated with AF-related symptom severity using European Heart Rhythm Association symptom classification and HRQoL using 5-level EuroQoL- 5D. Results: In 1218 AF patients (mean age 71.1 ± 10.5 years, 34.5% female), female sex (OR 3.7, p < 0.001), preexisting coronary artery disease (CAD) (OR 1.7, p = 0.020), a history of cardioversion (OR 1.4, p = 0.041), cardiac anxiety (OR 1.2; p < 0.001), stress from noise (OR 1.4, p = 0.005), work-related stress (OR 1.3, p = 0.026), and sleep disturbance (OR 1.2, p = 0.016) were associated with higher AF-related symptom severity. CAD (β = −0.23, p = 0.001), diabetes mellitus (β = −0.25, p < 0.001), generalized anxiety (β = −0.30, p < 0.001), cardiac anxiety (β = −0.16, p < 0.001), financial stress (β = −0.11, p < 0.001), and sleep disturbance (β = 0.11, p < 0.001) were associated with impaired HRQoL. Conclusions: Psychological characteristics, preexisting CAD, and diabetes may play an important role in the identification of individuals at highest risk for impaired HRQoL and high symptom severity in patients with AF.
- 14 July 2020
- Published by Springer Nature in Journal of Interventional Cardiac Electrophysiology
- Vol. 61 (2) , 339-348
Reduction of inappropriate implantable cardioverter-defibrillator therapies using enhanced supraventricular tachycardia discriminators: the ReduceIT study
Purpose Inappropriate implantable cardioverter-defibrillator (ICD) shocks are associated with greater healthcare resource utilization, poorer quality-of-life, and higher mortality. We aimed to investigate the performance of enhanced supraventricular tachycardia (SVT) discrimination algorithms (morphology discrimination, rate stability, and sudden or chamber onset) for reducing inappropriate ICD therapies in patients with ICD/cardiac resynchronization therapy devices. Methods This prospective, non-randomized, multicenter study (ReduceIT) study took place at 56 sites across Germany and Estonia. Adults at risk of sudden cardiac death undergoing St. Jude Medical™ ICD or CRT-D implantation were included. The primary endpoint was freedom from inappropriate ICD shock at 12 months and was analyzed in the intention to treat (ITT) and per-protocol population. Results Overall, 733 patients (65.9 ± 11.4 years) were included, of which 40.9% and 59.1% received a single- and dual-chamber detection device, respectively. During follow-up (median 11.9 [0–21.6] months), 96.3% of patients experienced no inappropriate therapy (ITT). The sensitivity, specificity, and accuracy for VT/VF were 91.9%, 95.5%, and 94.7%, respectively. In the per-protocol population (n = 620), the proportion of patients free from inappropriate shock at 12 months was 98.4% (n = 610; 95% CI 97.1–99.2%) and exceeded the expected value of 93% (p < 0.0001) which was derived from the rates in the SPICE, ATPonFastVT, and DECREASE studies. A total of 44 patients (6.0%) died during follow-up, 19 deaths were cardiac-related which is consistent with a meta-analysis of EMPIRIC, MADIT-RIT, ADVANCE III, and PROVIDE. Serious device and procedure-related adverse effects occurred in 9.8% of patients. Conclusions In ICD/CRT-D devices with advanced SVT discriminators, device programming according to clinical setting and detection chamber significantly reduces the rate of inappropriate ICD shocks without compromising patient safety. The algorithms and settings described herein have particular clinical importance and their employment may be of benefit to ICD recipients.
- 14 July 2020
- Published by Springer Nature in Journal of Interventional Cardiac Electrophysiology
- Vol. 61 (2) , 339-348
Reduction of inappropriate implantable cardioverter-defibrillator therapies using enhanced supraventricular tachycardia discriminators: the ReduceIT study
Purpose Inappropriate implantable cardioverter-defibrillator (ICD) shocks are associated with greater healthcare resource utilization, poorer quality-of-life, and higher mortality. We aimed to investigate the performance of enhanced supraventricular tachycardia (SVT) discrimination algorithms (morphology discrimination, rate stability, and sudden or chamber onset) for reducing inappropriate ICD therapies in patients with ICD/cardiac resynchronization therapy devices. Methods This prospective, non-randomized, multicenter study (ReduceIT) study took place at 56 sites across Germany and Estonia. Adults at risk of sudden cardiac death undergoing St. Jude Medical™ ICD or CRT-D implantation were included. The primary endpoint was freedom from inappropriate ICD shock at 12 months and was analyzed in the intention to treat (ITT) and per-protocol population. Results Overall, 733 patients (65.9 ± 11.4 years) were included, of which 40.9% and 59.1% received a single- and dual-chamber detection device, respectively. During follow-up (median 11.9 [0–21.6] months), 96.3% of patients experienced no inappropriate therapy (ITT). The sensitivity, specificity, and accuracy for VT/VF were 91.9%, 95.5%, and 94.7%, respectively. In the per-protocol population (n = 620), the proportion of patients free from inappropriate shock at 12 months was 98.4% (n = 610; 95% CI 97.1–99.2%) and exceeded the expected value of 93% (p < 0.0001) which was derived from the rates in the SPICE, ATPonFastVT, and DECREASE studies. A total of 44 patients (6.0%) died during follow-up, 19 deaths were cardiac-related which is consistent with a meta-analysis of EMPIRIC, MADIT-RIT, ADVANCE III, and PROVIDE. Serious device and procedure-related adverse effects occurred in 9.8% of patients. Conclusions In ICD/CRT-D devices with advanced SVT discriminators, device programming according to clinical setting and detection chamber significantly reduces the rate of inappropriate ICD shocks without compromising patient safety. The algorithms and settings described herein have particular clinical importance and their employment may be of benefit to ICD recipients.
- Open Access
- 25 October 2018
- Published by Springer Nature in Herz
- Vol. 43 (7) , 583
Welchen Weg geht die moderne Schrittmachertherapie?
- 25 October 2018
- Published by Springer Nature in Herz
- Vol. 43 (7) , 583
Open AccessWelchen Weg geht die moderne Schrittmachertherapie?
- 1 May 2013
- Published by Springer Nature in Herzschrittmachertherapie + Elektrophysiologie
- Vol. 24 (2) , 136-138
A patient with severely reduced LV function and electrical storm saved by wearable cardioverter-defibrillator: a case report
The wearable cardioverter-defibrillator (WCD) is indicated in patients who are considered to be at temporarily high risk for sudden cardiac death (SCD), when an implantable defibrillator is not yet clearly indicated. We report the case of a 41-year-old patient with a newly diagnosed severely reduced left ventricular (LV) function for suspected myocarditis and repeated nonsustained ventricular tachycardia (VT). This patient was supplied with a WCD who came back to the hospital 4 weeks after discharge with an electrical storm and adequate discharge of the WCD. After application of amiodarone, no further arrhythmias were detected during intrahospital course. For further risk stratification, we performed a magnetic field imaging (MFI), that was reported to be useful in risk assessment of SCD in patients with ischemic cardiomyopathy. This measurement showed a normal result, but we decided to give an implantable cardioverter-defibrillator (ICD) to the patient. During a follow-up of 1 year, no further arrhythmias occurred. With this case, we report the efficacy of a WCD, which is a novel tool in patients at temporarily high risk of SCD and we report a novel method of risk stratification in patients with a high risk of SCD.
- 1 May 2013
- Published by Springer Nature in Herzschrittmachertherapie + Elektrophysiologie
- Vol. 24 (2) , 136-138
A patient with severely reduced LV function and electrical storm saved by wearable cardioverter-defibrillator: a case report
The wearable cardioverter-defibrillator (WCD) is indicated in patients who are considered to be at temporarily high risk for sudden cardiac death (SCD), when an implantable defibrillator is not yet clearly indicated. We report the case of a 41-year-old patient with a newly diagnosed severely reduced left ventricular (LV) function for suspected myocarditis and repeated nonsustained ventricular tachycardia (VT). This patient was supplied with a WCD who came back to the hospital 4 weeks after discharge with an electrical storm and adequate discharge of the WCD. After application of amiodarone, no further arrhythmias were detected during intrahospital course. For further risk stratification, we performed a magnetic field imaging (MFI), that was reported to be useful in risk assessment of SCD in patients with ischemic cardiomyopathy. This measurement showed a normal result, but we decided to give an implantable cardioverter-defibrillator (ICD) to the patient. During a follow-up of 1 year, no further arrhythmias occurred. With this case, we report the efficacy of a WCD, which is a novel tool in patients at temporarily high risk of SCD and we report a novel method of risk stratification in patients with a high risk of SCD.
- 7 February 2012
- Published by Wiley in Journal of Cardiovascular Electrophysiology
- Vol. 23 (7) , 735-740
Comparison Between Atrial Fibrillation‐Triggered Implantable Cardioverter‐Defibrillator (ICD) Shocks and Inappropriate Shocks Caused by Lead Failure: Different Impact on Prognosis in Clinical Practice
Prognostic Impact of Inappropriate Shocks.Introduction: Recent studies suggest a worse impact of inappropriate shock therapies on the outcome of patients with an implantable cardioverter‐defibrillator (ICD). However, it is not known whether the worse impact is attributed to the ICD shock itself or due to the underlying heart disease. The aim of the study was to evaluate the impact of inappropriate ICD shocks on clinical outcome by comparing ICD shocks triggered by atrial fibrillation (AF) with shocks caused by lead failure.Methods and Results: A total of 1,411 consecutive patients of the prospective single‐center ICD‐registry Ludwigshafen who underwent an ICD implantation between 1992 and 2008 for primary or secondary prevention of sudden cardiac death were analyzed. During the median follow‐up of 3 years, 297 (21%) patients experienced inappropriate ICD shocks. Sixty percent of patients had inappropriate shocks due to AF and 24% due to lead defect or T‐wave oversensing. Multiple ICD shocks (≥2) triggered by AF were associated with a worse prognosis, whereas a single shock due to AF or 1 or multiple shocks resulting from lead failure were not. ICD shocks caused by AF occurred more often in tandem with a serious adverse event than in patients with a lead failure (15% vs 6%, P < 0.05).Conclusion: Multiple ICD shocks triggered by AF are associated with a worse prognosis in ICD patients, whereas a single shock due to AF or shocks resulting from lead failure are not. These data support that the ICD shock itself has no worse impact on the outcome of ICD patients. (J Cardiovasc Electrophysiol, Vol. 23, pp. 735‐740, July 2012)
- 7 February 2012
- Published by Wiley in Journal of Cardiovascular Electrophysiology
- Vol. 23 (7) , 735-740
Comparison Between Atrial Fibrillation‐Triggered Implantable Cardioverter‐Defibrillator (ICD) Shocks and Inappropriate Shocks Caused by Lead Failure: Different Impact on Prognosis in Clinical Practice
Prognostic Impact of Inappropriate Shocks.Introduction: Recent studies suggest a worse impact of inappropriate shock therapies on the outcome of patients with an implantable cardioverter‐defibrillator (ICD). However, it is not known whether the worse impact is attributed to the ICD shock itself or due to the underlying heart disease. The aim of the study was to evaluate the impact of inappropriate ICD shocks on clinical outcome by comparing ICD shocks triggered by atrial fibrillation (AF) with shocks caused by lead failure.Methods and Results: A total of 1,411 consecutive patients of the prospective single‐center ICD‐registry Ludwigshafen who underwent an ICD implantation between 1992 and 2008 for primary or secondary prevention of sudden cardiac death were analyzed. During the median follow‐up of 3 years, 297 (21%) patients experienced inappropriate ICD shocks. Sixty percent of patients had inappropriate shocks due to AF and 24% due to lead defect or T‐wave oversensing. Multiple ICD shocks (≥2) triggered by AF were associated with a worse prognosis, whereas a single shock due to AF or 1 or multiple shocks resulting from lead failure were not. ICD shocks caused by AF occurred more often in tandem with a serious adverse event than in patients with a lead failure (15% vs 6%, P < 0.05).Conclusion: Multiple ICD shocks triggered by AF are associated with a worse prognosis in ICD patients, whereas a single shock due to AF or shocks resulting from lead failure are not. These data support that the ICD shock itself has no worse impact on the outcome of ICD patients. (J Cardiovasc Electrophysiol, Vol. 23, pp. 735‐740, July 2012)