Biomedical subjects

Georg Schmidt

Publications and source records attributed to Georg Schmidt.

25 records · Page 2Linked to original sources

PubMed2003

Risk stratification after acute myocardial infarction by heart rate turbulence.

BACKGROUND: Retrospective postinfarction studies revealed that decreased heart rate turbulence (HRT) indicates increased risk for subsequent death. This is the first prospective study to validate HRT in a large cohort of the reperfusion era. METHODS AND RESULTS: One thousand four hundred fifty-five survivors of an acute myocardial infarction (age <76 years) in sinus rhythm were enrolled. HRT onset (TO) and slope (TS) were calculated from Holter records. Patients were classified into the following HRT categories: category 0 if both TO and TS were normal, category 1 if either TO or TS was abnormal, or category 2 if both TO and TS were abnormal. The primary end point was all-cause mortality. During a follow-up of 22 months, 70 patients died. Multivariately, HRT category 2 was the strongest predictor of death (hazard ratio, 5.9; 95% CI, 2.9 to 12.2), followed by left ventricular ejection fraction (LVEF) < or =30% (4.5; 2.6 to 7.8), diabetes mellitus (2.5; 1.6 to 4.1), age > or =65 years (2.4; 1.5 to 3.9), and HRT category 1 (2.4; 1.2 to 4.9). LVEF < or =30% had a sensitivity of 27% at a positive predictive accuracy level of 23%. The combined criteria of LVEF < or =30%, HRT category 2 or LVEF >30%, age > or =65 years, diabetes mellitus, and HRT category 2 had a sensitivity of 24% at a positive predictive accuracy level of 37%. The combined criteria of LVEF < or =30% or LVEF >30%, age > or =65 years, diabetes mellitus, and HRT category 1 or 2 had a sensitivity of 44% at a positive predictive accuracy level of 23%. CONCLUSIONS: HRT is a strong predictor of subsequent death in postinfarction patients of the reperfusion era.

Aged↗

PubMed2003

Heart rate turbulence.

Survivors of acute myocardial infarction are at increased risk of sudden cardiac death. Recent trials have demonstrated that in selected high risk post-myocardial infarction patients mortality can be significantly reduced by implantation of an autonomic cardioverter defibrillator. Therefore, risk stratification strategies have gained increasing importance. Recently, a new method for risk stratification, coined heart rate turbulence, has been published. The method quantifies the physiological short term fluctuation of sinus rhythm cycle lengths following singular ventricular premature complexes. Heart rate turbulence is a consistent phenomenon in low risk patients with ischemic heart disease. The absence of this phenomenon indicates a significantly increased risk of subsequent mortality. The measures for quantifying heart rate turbulence, turbulence onset, and turbulence slope are strong risk predictors, even when adjusted for other established mortality predictors, such as left ventricular ejection fraction, arrhythmia count, heart rate variability, mean heart rate and history of previous myocardial infarction. Heart rate turbulence may be useful not only for risk prediction in post-myocardial infarction patients but also for risk prediction in other patients such as in patients with dilated cardiomyopathy and Chagas disease.

Arrhythmias, Cardiac↗

PubMed2003

Heart rate turbulence in Chagas disease.

Heart rate turbulence (HRT) quantifies the biphasic response of the sinus node to ventricular premature complexes (VPCs) and is a powerful electrocardiogram related risk predictor. VPCs are frequent in Chagas disease, a potentially lethal illness, and can hamper the analysis by conventional methods of autonomic heart control. The aim of the study was to examine HRT in patients with Chagas disease. Chagas disease patients and healthy controls (group 0, n = 11) without other diseases were submitted to a standardized protocol, including electrocardiogram, echocardiography, and 24-hour Holter monitoring. Chagas disease patients were divided according to their left ventricular systolic function: normal (group 1, n = 103) and reduced ejection fraction (group 2, n = 23). Two HRT indices, turbulence onset (TO) and turbulence slope (TS), were calculated and compared among groups after adjustment for covariates like the prevalence of VPCs and the mean heart rate. Chagas disease patients had significantly altered TO (group 1: -0.0186, group 2: -0.0126) and TS (group 1: 10.844, group 2: 7.870) values in comparison with controls (TO -0.0256, TS 19.829); P < 0.001 for both comparisons. In conclusion, HRT data may be useful in the electrocardiographic analysis of autonomic heart control in Chagas disease. Its prognostic value remains to be determined.

Adult↗

PubMed2003

Prognostic significance of heart rate turbulence following ventricular premature beats in patients with idiopathic dilated cardiomyopathy.

UNLABELLED: Heart Rate Turbulence in Dilated Cardiomyopathy. INTRODUCTION: The aim of this study was to investigate the prognostic significance of heart rate turbulence (HRT) characterized by HRT onset and slope after ventricular premature beats in patients with idiopathic dilated cardiomyopathy (IDC). METHODS AND RESULTS: Blinded HRT analysis was performed in 242 patients with IDC who were enrolled in the Marburg Cardiomyopathy database between 1992 and 2000. During 41 +/- 23 months of follow-up, 54 patients (22%) died or underwent heart transplant. On Cox univariate regression analysis, abnormal HRT onset, HRT slope, HRT onset combined with HRT slope, left ventricular (LV) ejection fraction, LV size, and New York Heart Association (NYHA) functional class III showed a significant association with total mortality or the need for heart transplant. On multivariate analysis, abnormal HRT onset identified patients without transplant-free survival, as did LV size and NYHA class III heart failure. Major arrhythmic events were observed in 42 patients (17%) during follow-up. On univariate analysis, abnormal HRT onset, HRT onset combined with HRT slope, male sex, NYHA class III, LV ejection fraction, and LV size were associated with a higher incidence of major arrhythmic events. On multivariate analysis, only LV ejection fraction remained as a significant arrhythmia risk predictor, with a relative risk of 2.2 per 10% decrease in ejection fraction (95% confidence interval 1.5-3.2). CONCLUSION: In this selected patient population with IDC, HRT onset is a significant predictor of transplant-free survival, as are LV size and NYHA class. For arrhythmia risk stratification, however, only LV ejection fraction remained a significant risk predictor on multivariate analysis.

Age Distribution↗

PubMed2003

Heart rate turbulence following ventricular premature beats in healthy controls.

BACKGROUND: Heart rate turbulence (HRT) has recently been described as a strong, independent risk stratifier in postinfarct patients. To date, however, the incidence of false positive HRT findings in adults is unknown. Therefore, we performed a blinded, retrospective analysis of HRT in a prospectively collected database of 110 apparently healthy persons to determine the prevalence and clinical significance of abnormal HRT findings in healthy controls using previously published cut-off values. METHODS AND RESULTS: The study included 43 out of 110 apparently healthy adults, in whom a sufficient number of ventricular premature beats were available for HRT analysis on 24-hour Holter recordings. The HRT slope was dichotomized at 2.5 ms per R-R interval and HRT onset was dichotomized at 0% using previously established criteria to define an abnormal HRT analysis in postinfarct patients. Using these definitions, abnormal HRT results were found in 2 out of 43 controls (5%) for HRT slope and in 8 out of 43 controls (19%) for HRT onset without any cardiac deaths during 32 +/- 15 months follow-up. CONCLUSIONS: The incidence of false positive HRT results in healthy middle-aged volunteers is low for HRT slope (5%), but not for HRT onset (19%) when previously published cut-off values are used to define abnormal HRT results. Thus, HRT slope dichotomized at 2.5 ms per R-R interval, but not HRT onset dichotomized at 0%, may be used as a relatively specific tool for risk stratification in middle-aged persons.

Adult↗

PubMed2002

Heart rate turbulence-based predictors of fatal and nonfatal cardiac arrest (The Autonomic Tone and Reflexes After Myocardial Infarction substudy).

A previous report on heart rate (HR) turbulence showed its value in postinfarction risk stratification. The present study determines the predictive value of HR turbulence in a low-risk population after acute myocardial infarction and provides insight into its pathophysiologic correlates. With use of the database of the The Autonomic Tone and Reflexes After Myocardial Infarction (ATRAMI) study, data were obtained from 1,212 survivors with a mean duration of follow-up of 20.3 months. The a priori end point was defined as the combination of fatal cardiac arrest and nonfatal cardiac arrest. HR turbulence characterized by turbulence onset (TO) and turbulence slope (TS) was calculated and correlated with baroreflex sensitivity (BRS) and the SD of the normal-to-normal RR intervals (SDNN). A composite index of cardiac autonomic function was assessed by combining HR turbulence (TO and TS), BRS, and SDNN. Both TO and TS correlated moderately but significantly with BRS and SDNN (r = 0.26 to 0.44, p <0.001 for all correlations). On Cox's univariate regression analysis, the RRs for abnormal values of TO, TS, and the combination of abnormal TO and TS were 1.86 (95% confidence interval [CI] 0.96 to 3.61, p = 0.065), 4.08 (95% CI 2.11 to 7.89, p <0.0001), and 6.87 (95% CI 3.06 to 15.45, p <0.0001), respectively. The composite autonomic index (combined TO, TS, BRS, and SDNN) was the strongest risk predictor: for all 4 abnormal factors, RR 16.79 (95% CI 6.01 to 46.89, p <0.0001). On multivariate analysis, abnormal TO and TS, and left ventricular ejection fraction remained as independent predictors: RRs 4.07 (95% CI 1.70 to 9.77, p = 0.0017) and 3.53 (95% CI 1.76 to 7.06, p = 0.0004), respectively. In a separate model, the composite autonomic index was the strongest multivariate risk predictor: RR 8.67 (95% CI 2.72 to 7.65, p = 0.0003) for all abnormal factors, and adjusted for left ventricular ejection fraction. Thus, this study confirms the independent value of HR turbulence in predicting fatal cardiac arrest and nonfatal cardiac arrest in a low-risk post-acute myocardial infarction population. By combining HR turbulence, BRS, and SDNN, a comprehensive assessment of cardiac autonomic reflexes and modulation can be obtained.

Autonomic Nervous System↗

PubMed2002

A phenomenon of heart-rate turbulence, its evaluation, and prognostic value.

Identification of high-risk cardiac patients is crucial for stratification strategies and prevention of cardiovascular events, including death. Single ventricular premature beat triggers some oscillations in cardiac cycle duration (the shortening followed by the lengthening of the cycle intervals) in healthy subjects and low-risk patients with ischaemic heart disease and/or heart failure. This phenomenon is called heart-rate turbulence (HRT). It was shown in retrospective and prospective studies that the absence of HRT is associated with increased risk of subsequent mortality in cardiac patients. HRT can be quantified by two variables: turbulence onset (TO), describing an early acceleration phase, and turbulence slope (TS), describing a late deceleration phase of heart rate after ventricular premature beat. Both TO and TS are independent one from another and from other conventional risk predictors. The combination of TO and TS seems to be the strongest Holter-based risk predictor and has some addictive predictive value to left ventricular ejection fraction, heart rate variability, and the averaged diurnal heart rate and baroreflex sensitivity. In addition, HRT has a predictive value in patients treated with beta-blockers and amiodarone. Moreover, it is thought that HRT is mediated by baroreflex and therefore can be used as a non-invasive measure of its sensitivity and autonomic nervous system function. Blunted HRT can be observed in diabetic patients with autonomic dysfunction and in patients with atropine-blocked vagal nerve activity. Moreover, it seems that a diurnal variation of HRT exists because it is better expressed during sleep. However, the use of HRT is limited to patients with dominant sinus rhythm and the presence of single ventricular beat. Nevertheless, the assessment of HRT is an inexpensive and simple method and can be performed with a routine ambulatory 24-hour ECG recording.

Arrhythmias, Cardiac↗