Nathan M Segerson

Klinikum Coburg, Landkreis Coburg, Bavaria, Germany

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Publications (34)121.27 Total impact

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    ABSTRACT: The objective of this study was to test the hypothesis that gastric bypass surgery (GBS) would favorably impact cardiac remodeling and function. GBS is increasingly used to treat severe obesity, but there are limited outcome data. We prospectively studied 423 severely obese patients undergoing GBS and a reference group of severely obese subjects that did not have surgery (n = 733). At a 2-year follow up, GBS subjects had a large reduction in body mass index compared with the reference group (-15.4 ± 7.2 kg/m(2) vs. -0.03 ± 4.0 kg/m(2); p < 0.0001), as well as significant reductions in waist circumference, systolic blood pressure, heart rate, triglycerides, low-density lipoprotein cholesterol, and insulin resistance. High-density lipoprotein cholesterol increased. The GBS group had reductions in left ventricular (LV) mass index and right ventricular (RV) cavity area. Left atrial volume did not change in GBS but increased in reference subjects. In conjunction with reduced chamber sizes, GBS subjects also had increased LV midwall fractional shortening and RV fractional area change. In multivariable analysis, age, change in body mass index, severity of nocturnal hypoxemia, E/E', and sex were independently associated with LV mass index, whereas surgical status, change in waist circumference, and change in insulin resistance were not. Marked weight loss in patients undergoing GBS was associated with reverse cardiac remodeling and improved LV and RV function. These data support the use of bariatric surgery to prevent cardiovascular complications in severe obesity.
    Journal of the American College of Cardiology 02/2011; 57(6):732-9. · 14.09 Impact Factor
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    ABSTRACT: MRI for AF Patient Selection and Ablation Approach. Introduction: Left atrial (LA) fibrosis and ablation related scarring are major predictors of success in rhythm control of atrial fibrillation (AF). We used delayed enhancement MRI (DE-MRI) to stratify AF patients based on pre-ablation fibrosis and also to evaluate ablation-induced scarring in order to identify predictors of a successful ablation. Methods and Results: One hundred and forty-four patients were staged by percent of fibrosis quantified with DE-MRI, relative to the LA wall volume: minimal or Utah stage 1; <5%, mild or Utah stage 2; 5-20%, moderate or Utah stage 3; 20-35%, and extensive or Utah stage 4; >35%. All patients underwent pulmonary vein (PV) isolation and posterior wall and septal debulking. Overall, LA scarring was quantified and PV antra were evaluated for circumferential scarring 3 months post ablation. LA scarring post ablation was comparable across the 4 stages. Most patients had either no (36.8%) or 1 PV (32.6%) antrum circumferentially scarred. Forty-two patients (29%) had recurrent AF over 283 ± 167 days. No recurrences were noted in Utah stage 1. Recurrence was 28% in Utah stage 2, 35% in Utah stage 3, and 56% in Utah stage 4. Recurrence was predicted by circumferential PV scarring in Utah stage 2 and by overall LA wall scarring in Utah stage 3. No recurrence predictors were identified in Utah stage 4. Conclusions: Circumferential PV antral scarring predicts ablation success in mild LA fibrosis, while posterior wall and septal scarring is needed for moderate fibrosis. This may help select the proper candidate and strategy in catheter ablation of AF.
    Journal of Cardiovascular Electrophysiology 01/2011; 22(1):16-22. · 3.48 Impact Factor
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    ABSTRACT: Salt Lake City, Utah; Farmington, Connecticut; and Rochester, New York Objectives The objective of this study was to test the hypothesis that gastric bypass surgery (GBS) would favorably impact cardiac remodeling and function.
    01/2011;
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    ABSTRACT: Because of small size and anatomic variation, implantation of intracardiac leads for permanent pacing in pediatric and congenital heart disease (CHD) patients can be challenging. A novel 4.1F bipolar catheter-delivered lead offers potential advantages for this population. OBJECTIVE; The purpose of this study was to retrospectively evaluate this lead performance in this specific population. We performed a retrospective descriptive analysis of all pediatric and adult CHD patients at a single center implanted with a 4.1F bipolar catheter-delivered active fixation pacemaker lead (Medtronic model 3830, Medtronic, Inc, Minneapolis, MN, USA). Over 10 months, 42 leads were implanted in 27 patients. Twenty-six atrial and 16 ventricular leads were placed. Patient ages were 1-28 years (mean 15 +/- 7), and weights were 7.8-104 kg (mean 51.5 +/- 26.6). Ventricular septal defect and D-transposition of great arteries were the most prevalent CHD diagnoses. Implant capture thresholds were 1.2 +/- 0.8 V at 0.5 ms in the atrium and 0.8 +/- 0.5 V at 0.5 ms in the ventricle. Implant sensing thresholds were 4.1 +/- 2.7 mV in the atrium and 12.1 +/- 4.9 mV in the ventricle. Phrenic nerve stimulation was avoided in all, and selective site pacing was achieved in most cases. Pacing and sensing thresholds remained stable during 90 +/- 52 days follow-up. No lead related complications, failures, or extractions were observed. In our single-center experience with pediatric and CHD patients, a novel small, catheter-delivered bipolar lead has proven safe and effective for atrial and ventricular pacing in acute and subacute time periods. Longer performance trends will be required to determine chronic efficacy.
    Congenital Heart Disease 03/2010; 5(2):149-56. · 1.01 Impact Factor
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    ABSTRACT: LA Debulking for Atrial Fibrillation.Introduction: Though pulmonary vein (PV) isolation has been widely adopted for treatment of atrial fibrillation (AF), recurrence rates remain unacceptably high with persistent and longstanding AF. As evidence emerges for non-PV substrate changes in the pathogenesis of AF, more extensive ablation strategies need further study.Methods: We modified our PV antrum isolation procedure to include abatement of posterior and septal wall potentials. We also employed recently described image-processing techniques using delayed-enhancement (DE) MRI to characterize tissue injury patterns 3 months after ablation, to assess whether each PV was encircled with scar, and to assess the impact of these parameters on procedural success.Results: 118 consecutive patients underwent debulking procedure and completed follow-up, of which 86 underwent DE-MRI. The total left atrial (LA) radiofrequency delivery correlated with percent LA scarring by DE-MRI (r = 0.6, P < 0.001). Based on DE patterns, complete encirclement was seen in only 131 of 335 PVs (39.1%). As expected, Cox regression analysis showed a significant relationship between the number of veins encircled by delayed enhancement and clinical success (hazard ratio of 0.62, P = 0.015). Also, progressive quartile increases in postablation posterior and septal wall scarring reduced recurrences rates with a HR of 0.65, P = 0.022 and 0.66, P = 0.026, respectively.Conclusion: Pathologic remodeling in the septal and posterior walls of the LA helps form the pathogenic substrate for AF, and these early results suggest that more aggressive treatment of these regions appears to correlate with improved ablation outcomes. Noninvasive imaging to characterize tissue changes after ablation may prove essential to stratifying recurrence risk. (J Cardiovasc Electrophysiol, Vol. 21, pp. 126-132, February 2010)
    Journal of Cardiovascular Electrophysiology 01/2010; 21(2):126 - 132. · 3.48 Impact Factor
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    ABSTRACT: Cardiac imaging, both noninvasive and invasive, has become a crucial part of evaluating patients during the electrophysiology procedure experience. These anatomical data allow electrophysiologists to not only assess who is an appropriate candidate for each procedure, but also to determine the rate of success from these procedures. This article incorporates a review of the various cardiac imaging techniques available today, with a focus on atrial arrhythmias, ventricular arrhythmias and device therapy.
    Future Cardiology 01/2010; 6(1):113-27.
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    ABSTRACT: Atrial fibrillation remains the most common arrhythmia in the USA and is associated with an increased risk for stroke, congestive heart failure and overall mortality. There has been a tremendous advance in the field of catheter ablation of atrial fibrillation that has resulted in better outcomes for patients. The approach for ablation of atrial fibrillation can be different depending on patients' presentation of paroxysmal or persistent atrial fibrillation. Pulmonary vein isolation remains the cornerstone of any ablation strategy for atrial fibrillation; however, further ablation, end points of the procedure, clinical end points for successful ablation and appropriate follow-up remain controversial. We aim to discuss these different approaches and the major controversies in catheter ablation of atrial fibrillation.
    Expert Review of Cardiovascular Therapy 09/2009; 7(9):1091-101.
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    ABSTRACT: Pulmonary vein antrum isolation (PVAI) plays a pivotal role in the comprehensive treatment of atrial fibrillation (AF). The need for effective anticoagulation bridging following PVAI is associated with significant vascular complication rates and increased costs. We investigated the safety of PVAI in patients with therapeutic international normalized ratios (INR) the day of the procedure. A case-control analysis was performed on patients who underwent PVAI with therapeutic INR (>2). Patients with normal preprocedure INR served as controls. The incidence of major and minor hematomas, fistulas, vascular injury, and cardiac perforation or tamponade were catalogued. PVAI was performed under fluoroscopic, electro-anatomical, and intracardiac echocardiographic guidance, with an open irrigation ablation technique. A total of 194 patients (mean age 64 +/- 12) were included; 87 patients underwent PVAI with therapeutic INR (cases) and 107 with normal INR (controls). Persistent AF was more prevalent than paroxysmal AF in the therapeutic INR group. The mean INR for cases was 2.8 +/- 0.7 compared to 1.4 +/- 0.3 in the control group (P < 0.01). All procedures were completed without acute complications. Two major adverse events were observed, one in each arm. No significant difference in terms of minor (6.5% vs. 5.7%, P = 0.23) or major (0.93% vs. 1.15%, P = 0.49) vascular events or bleeding was detected between the therapeutic INR and the control group. The combined endpoint of major and minor complications did not differ among groups (9.35% vs. 8.05%, P = 0.19). Atrial fibrillation ablation in patients with therapeutic INR on the day of a procedure appears to be safe and feasible. Expensive outpatient anti-coagulation bridging may be safely avoided in this type of population.
    Pacing and Clinical Electrophysiology 08/2009; 32(8):995-9. · 1.75 Impact Factor
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    ABSTRACT: Atrial fibrillation (AF) is associated with diffuse left atrial fibrosis and a reduction in endocardial voltage. These changes are indicators of AF severity and appear to be predictors of treatment outcome. In this study, we report the utility of delayed-enhancement magnetic resonance imaging (DE-MRI) in detecting abnormal atrial tissue before radiofrequency ablation and in predicting procedural outcome. Eighty-one patients presenting for pulmonary vein antrum isolation for treatment of AF underwent 3-dimensional DE-MRI of the left atrium before the ablation. Six healthy volunteers also were scanned. DE-MRI images were manually segmented to isolate the left atrium, and custom software was implemented to quantify the spatial extent of delayed enhancement, which was then compared with the regions of low voltage from electroanatomic maps from the pulmonary vein antrum isolation procedure. Patients were assessed for AF recurrence at least 6 months after pulmonary vein antrum isolation, with an average follow-up of 9.6+/-3.7 months (range, 6 to 19 months). On the basis of the extent of preablation enhancement, 43 patients were classified as having minimal enhancement (average enhancement, 8.0+/-4.2%), 30 as having moderate enhancement (21.3+/-5.8%), and 8 as having extensive enhancement (50.1+/-15.4%). The rate of AF recurrence was 6 patients (14.0%) with minimal enhancement, 13 (43.3%) with moderate enhancement, and 6 (75%) with extensive enhancement (P<0.001). DE-MRI provides a noninvasive means of assessing left atrial myocardial tissue in patients suffering from AF and might provide insight into the progress of the disease. Preablation DE-MRI holds promise for predicting responders to AF ablation and may provide a metric of overall disease progression.
    Circulation 05/2009; 119(13):1758-67. · 15.20 Impact Factor
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    ABSTRACT: During supraventricular and ventricular tachycardia, the arterial baroreflex predominates with minimal contribution from the cardiopulmonary reflex. To our knowledge, the role of the arterial baroreflex gain (BRG) during and immediately following termination of ventricular fibrillation (VF) has not been characterized. We hypothesized that (1) arterial BRG correlated with sinus node cycle length (SNCL) changes during VF, and that (2) the greater the arterial BRG, the greater the blood pressure (BP) recovery following successful defibrillation. Arterial BRG was assessed in 18 patients referred for the implantation of a defibrillator incorporating an atrial lead. The average SNCL was measured during the 5 seconds prior to VF induction and the last 5 seconds during VF before defibrillation. Percent SNCL change (%DeltaSNCL) was determined. Arterial BP recovery was calculated as the difference in mean BP following defibrillation compared to during VF. Arterial BRG ranged between -3 and 18 ms/mmHg. During VF, SNCL shortened in 11 patients (group A, mean %DeltaSNCL =-15%), and surprisingly lengthened in seven patients (group B, mean %DeltaSNCL = 5%). There was no correlation between %DeltaSNCL and arterial BRG. In fact, arterial BRG in group A was lower when compared with group B (P = 0.075). Similarly, there was no correlation between arterial BRG and BP recovery. We found no correlation between arterial BRG and %DeltaSNCL during VF, or BP recovery following defibrillation. Our findings of SNCL lengthening in 7 of 18 patients suggest that in some patients, arterial BRG plays a minor role during VF with a greater contribution from the cardiopulmonary BRG.
    Journal of Cardiovascular Electrophysiology 03/2009; 20(2):187-92. · 3.48 Impact Factor
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    ABSTRACT: The incidence of atrial flutter (AFL) post pulmonary vein antrum isolation (PVAI) in patients with atrial fibrillation (AF) is reported to be between 8% and 20%. The need for right or left AFL ablation during the initial PVAI procedure remains controversial. We prospectively compared mapping and ablation versus no ablative treatment of inducible AFL during PVAI. In 220 patients (167 men, mean age 56+/-15 years) with symptomatic AF presenting for PVAI, burst pacing from the high right atrium and coronary sinus was performed to determine AFL inducibility. A total of 25 patients with sustained (17 patients) or reproducible (eight patients) AFL were included in this study. Patients were randomized to mapping and ablation of AFL using the CARTO 3D mapping system (Biosense Webster, Diamond Bar, CA, USA) versus no further ablation. Typical AFL was induced in 48% of the patients. During a follow-up of 12+/-4 months, recurrences were determined by serial 48-h Holter and event monitors. Recurrence rates, time to recurrence, and AFL cycle length differences between both groups were not statistically significant. These data suggest that inducibility of AFL post PVAI does not predict long-term incidence of AFL. Moreover, this study demonstrates little benefit to mapping and ablation of these arrhythmias during the PVAI procedures.
    Pacing and Clinical Electrophysiology 01/2009; 31(12):1592-7. · 1.75 Impact Factor
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    01/2009;
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    ABSTRACT: Magnetic resonance imaging (MRI) based approaches are supporting rapid advances in all phases of the management of atrial fibrillation (AF) patients, especially with the use of contrast agents and novel MRI acquisition techniques. In this report, we summarize briefly some recent advances in our use of MRI for AF management with special focus on the impact of these findings on the modeling and simulation of AF. We summarize results from two clinical studies, one of patients before radio frequency ablation of atrial fibrillation and one after ablation. In pre-ablation patients, significant extent of enhancements in delayed enhancement MRI of the left atrium is predictive of worsened outcome from ablation. The presumed mechanism is the presence of fibrosis in the posterior wall of the left atrium and supports the known finding that patients in chronic atrial fibrillation develop elevated levels of fibrosis. The implications of this finding on modeling of atrial electrical activity are that any such models must include both structural and functional fibrosis if they are to reflect realistic conditions.
    Computers in Cardiology, 2008; 10/2008
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    ABSTRACT: We describe a noninvasive method of detecting and quantifying left atrial (LA) wall injury after pulmonary vein antrum isolation (PVAI) in patients with atrial fibrillation (AF). Using a 3-dimensional (3D) delayed-enhancement magnetic resonance imaging (MRI) sequence and novel processing methods, LA wall scarring is visualized at high resolution after radiofrequency ablation (RFA). Radiofrequency ablation to achieve PVAI is a promising approach to curing AF. Controlled lesion delivery and scar formation within the LA are indicators of procedural success, but the assessment of these factors is limited to invasive methods. Noninvasive evaluation of LA wall injury to assess permanent tissue injury may be an important step in improving procedural success. Imaging of the LA wall with a 3D delayed-enhanced cardiac MRI sequence was performed before and 3 months after ablation in 46 patients undergoing PVAI for AF. Our 3D respiratory-navigated MRI sequence using parallel imaging resulted in 1.25 x 1.25 x 2.5 mm (reconstructed to 0.6 x 0.6 x 1.25 mm) spatial resolution with imaging times ranging 8 to 12 min. Radiofrequency ablation resulted in hyperenhancement of the LA wall in all patients post-PVAI and may represent tissue scarring. New methods of reconstructing the LA in 3D allowed quantification of LA scarring using automated methods. Arrhythmia recurrence at 3 months correlated with the degree of wall enhancement with >13% injury predicting freedom from AF (odds ratio: 18.5, 95% confidence interval: 1.27 to 268, p = 0.032). We define noninvasive MRI methods that allow for the detection and quantification of LA wall scarring after RF ablation in patients with AF. Moreover, there seems to be a correlation between the extent of LA wall injury and short-term procedural outcome.
    Journal of the American College of Cardiology 10/2008; 52(15):1263-71. · 14.09 Impact Factor
  • Nathan Segerson, Tobin Lim, Nassir F Marrouche
    Heart rhythm: the official journal of the Heart Rhythm Society 08/2008; 5(7):965-7. · 4.56 Impact Factor
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    ABSTRACT: Although modest elevations in pacing rate improve cardiac output and induce reflex sympathoinhibition, the threshold rate above which hemodynamic perturbations induce reflex sympathoexcitation remains unknown. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressures (MAP) and sympathetic nerve activity (SNA) were measured during normal sinus rhythm (NSR) and atrioventricular (AV) sequential pacing in 25 patients. Pacing was performed at 100, 120, and 140 beats/min with an AV interval of 100 ms. Patients were divided into two groups based on normal or abnormal left ventricular ejection fraction (LVEF): group 1 (n = 11; mean LVEF, 55%) and group 2 (n = 14; mean LVEF, 31%). In group 1, relative to NSR, SBP decreased an average of 2%, 3%, and 8% at 100, 120, and 140 beats/min (P < 0.001), respectively. DBP and MAP increased 9%, 15%, and 15% (P = 0.001) and 3%, 6%, and 5% [P = not significant (NS)], respectively. In group 2, SBP reductions were even greater, with an average decrease of 4%, 8%, and 16% (P < 0.001). Whereas DBP increased 9%, 9%, and 8% at 100, 120, and 140 beats/min (P = NS), MAP increased 3% and 2% at 100 and 120 beats/min but decreased 3% at 140 beats/min (P = 0.001). SNA recordings were obtained in 11 patients (6 in group 1 and 5 in group 2). In group 1, SNA decreased during all rates, with a mean 21% reduction. In group 2, however, SNA decreased at 100 and 120 beats/min (49% and 38%) but increased 24% at 140 beats/min. Patients with depressed LVEF exhibited altered hemodynamic and sympathetic responses to rapid sequential pacing. The implications of these findings in device programming and arrhythmia rate control await future studies.
    AJP Heart and Circulatory Physiology 06/2008; 295(3):H1076-H1080. · 4.01 Impact Factor
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    ABSTRACT: Several noninvasive measures of cardiac risk such as heart rate variability (HRV) cannot be used in patients with atrial fibrillation (AF). One promising exception is the measure of ventricular cycle length entropy (VCLE) where initial data suggest that a reduction in VCLE portends an increased risk of cardiac death in patients with chronic AF. In this study, we hypothesized that measures of short-term HRV during sinus rhythm would correlate with measures of cycle length entropy during paroxysms of AF. We tested 25 Holter recordings of paroxysmal AF from the Physionet AF Prediction Database. We calculated HRV parameters including standard deviation of all NN intervals (SDNN), the root mean square root of the differences between adjacent NN intervals (RMSSD), standard deviation of 5-minute averages of NN intervals (SDANN), percentage of adjacent NN interval differences >50 ms (pNN50), and interbeat correlation coefficient (ICC) from 30 minutes of normal sinus rhythm, and entropy measures (the Shannon Informational Entropy [ShEn] and Average of Approximate Entropy [ApEn]) from 5 minutes of AF that occurred during the same 24-hour monitor. Pairwise correlations were used to assess associations, as regression residuals were normally distributed. The mean entropy measures during AF were: ShEn: 4.78 +/- 0.82, ApEn: 0.198 +/- 0.21. When assessed during the 30 minutes immediately preceding AF onset, ICC showed a significant negative correlation with both ShEn (r =-0.65, P < 0.001) and ApEn (r =-0.60, P < 0.01). RMSSD also correlated with both ShEn (r = 0.41, P = 0.04) and ApEn (r = 0.39, P = 0.05), but other HRV measures showed no correlation with VCLE during AF. Reductions in RMSSD or increases in ICC, two short-term HRV measures that are known to reflect parasympathetic function in sinus rhythm, are correlated with reductions in the entropy of ventricular response intervals during AF. Our findings suggest that entropy during AF may be modulated, in part, by vagal innervation.
    Journal of Cardiovascular Electrophysiology 05/2008; 19(10):1031-6. · 3.48 Impact Factor
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    ABSTRACT: The catheter-based ablation of atrial fibrillation has been transformed greatly by the introduction of new technologies and techniques. This article describes the major advancements in real-time navigation systems, including both 3D mapping systems and 2D echocardiography. The relative strengths and weakness of these systems and their accuracy on clinical outcome is also discussed. Finally, we explore current and emerging MRI technologies that will allow the assessment of disease progression and enable procedural planning.
    Future Cardiology 05/2008; 4(3):253-60.
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    ABSTRACT: Bradyarrhythmias (BA) have been reported in patients with sleep apnea (SA), but the incidence of SA in patients with BA remains unclear. A case-control study was conducted to assess the prevalence of high-risk features of SA in patients with documented BA on 24-hour Holter monitoring compared with patients without BA. Controls were age-matched patients selected from those with no evidence of BA on 24-hour Holter monitoring. BA were defined as the presence of pauses of >3 seconds, regardless of the mechanism, and/or heart rate <40 beats/min during presumed waking hours (8 a.m. to 8 p.m.). High-risk features of SA were determined by the Berlin Questionnaire, with positive results defined as having '2 of 3 positive high-risk categories. Body mass index (BMI), hypertension, beta-blocker use, and other underlying characteristics were cataloged. Nineteen patients with documented BA and 47 with no BA were identified. The mean ages and BMIs in the active and control groups were not statistically significant. High-risk features for SA were present in 57.8% of patients in the BA group compared with 21.3% in the control group (p = 0.003). After controlling for age, BMI, hypertension, and beta-blocker use, patients with BA were 6 times more likely to have high-risk features of SA compared with those without BA (logistic regression odds ratio 6.1, 95% confidence interval 1.5 to 24, p = 0.012). In conclusion, irrespective of BMI, age, and other underlying risk factors, the presence of daytime BA was highly associated with high-risk features of SA.
    The American Journal of Cardiology 04/2008; 101(8):1147-50. · 3.21 Impact Factor
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    ABSTRACT: Increased spatial and temporal dispersion of repolarization contributes to ventricular arrhythmogenesis. Beat-to-beat fluctuations in T-wave timing are thought to represent such dispersion and may predict clinical events. The purpose of this study was to assess whether a novel noninvasive measure of beat-to-beat instability in T-wave timing would provide additive prognostic information in post-myocardial infarction patients. We studied 678 patients from 12 hospitals with 32-lead 5-minute electrocardiogram recordings 6-8 weeks after myocardial infarction. Custom software identified R wave-to-T wave intervals (RTIs) and diastolic intervals (DIs). Repolarization scatter (RTI:DI(StdErr)) was then calculated as the standard error about the RTI:DI regression line. In addition, left ventricular ejection fraction (LVEF), short-term heart rate variability (HRV) parameters, and QT variability index were measured. Patients were followed for the composite endpoint of death or life-threatening ventricular arrhythmia. After a mean follow-up of 63 months, 134 patients met the composite endpoint. An RTI:DI(StdErr) >5.50 ms was associated with a 210% increase in arrhythmias or deaths (P <.001). After adjusting for LVEF, RTI:DI(StdErr) remained an independent predictor (P <.001). RTI:DI(StdErr) was also independent of short-term HRV parameters and the QT variability index. Increased repolarization scatter, a measure of high-frequency, cycle-length-dependent repolarization instability, predicts poor outcomes in patients after myocardial infarction.
    Heart Rhythm 02/2008; 5(2):208-14. · 5.05 Impact Factor