Relation of ventricular repolarization to cardiac cycle length in normal subjects, hypertrophic cardiomyopathy, and patients with myocardial infarction.

BACKGROUND: Prolonged QT interval and QT dispersion have been reported to reflect an increased inhomogeneity of ventricular repolarization, which is believed to be responsible for the development of arrhythmic events in patients with long QT syndrome, coronary heart disease, and myocardial infarction, congestive heart failure, and hypertrophic cardiomyopathy (HC). HYPOTHESIS: This study was undertaken to determine whether an abnormal QT/RR dynamicity may reflect autonomic imbalance and may contribute to arrhythmogenesis in patients with heart disease. METHODS: The relation between QT, QTpeak (QTp), Tpeak-Tend (TpTe) intervals and cardiac cycle length was assessed in 70 normal subjects, 37 patients with HC, and 48 survivors of myocardial infarction (MI). A set of 10 consecutive electrocardiograms was evaluated automatically in each subject using QT Guard software (Marquette Medical Systems, Milwaukee, Wisc.). RESULTS: In patients with HC, all intervals were significantly prolonged compared with normals (p < 0.001 for QT and QTp; p < 0.04 for TpTc); in survivors of MI, this was true for the maximum QT and QTp intervals (p < 0.05). A strong linear correlation between QT, QTp, and RR intervals was observed in normals and in patients with MI and HC (r = 0.65-0.59, 0.82-0.77, 0.79-0.74, respectively, p < 0.0001). TpTe interval only showed a weak correlation with heart rate in normals (r = 0.24, p < 0.05) and was rate-independent in both patient groups (p = NS). Compared with normals, the slopes of QT/RR and QTp/RR regression lines were significantly steeper in patients with MI and HC (0.0990-0.0883, 0.1597-0.1551, 0.1653-0.1486, respectively). Regression lines were neither parallel nor identical between normals and patients (T > 1.96, Z > 3.07). There was no difference in steepness for TpTeR/RR lines between groups (0.0110, 0.0076, 0.0163, respectively). TpTe/QTp ratio was similar in normals and in patients with MI and HC (0.30 +/- 0.03, 0.31 +/- 0.07, 0.30 +/- 0.04, respectively), in the absence of any correlation between QTp and TpTe intervals, suggesting disproportional prolongation of both components of QT interval. CONCLUSION: Compared with normals, a progressive increase in QT and QTp intervals at slower heart rates in patients with MI and HC may indicate an enhanced variability of the early ventricular repolarization and may be one of the mechanisms of arrhythmogenesis.     

Diagnostic performance of QT interval variables from 24-h electrocardiography in the long QT syndrome

Aims The long QT syndrome is mainly defined by QT interval prolongation(QTc >0·44s). However, data obtained in genotyped patientsshowed that resting QTc measurement alone may be inaccuratefor ascertaining the phenotype. The aim of this study was toevaluate the diagnostic performance of QT interval rate-dependencein untreated chromosome 11-linked patients. Methods The study population consisted of 25 untreated longQT patients linked to chromosome 11 and 25 age- and gender-matchedcontrols. QTc intervals were measured on 12-lead resting ECGrecordings. From 24-h Holter recordings, the slope of the relationshipbetween ventricular repolarization and heart rate was studiedseparately day and night to assess neural modulation. Mean heartrates and rate-dependences of QT and Q-maximum of T (QTm) intervalswere compared between long QT patients and controls for bothtime periods. Results In both groups, the rate-dependences were modulatedby day–night influences. When compared to controls, longQT patients showed a significant increase at night in QT/RRslopes (0·158±0·05 vs 0·117±0·03,P=0·002)and QTm/RR slopes (0·163±0·05 vs 0·116±0·04,P=0·0006).Multivariate analysis, adjusting QTc interval on age and gender,discriminated between long QT patients and controls with a 76%sensitivity and a 84% specificity. A 96% sensitivity and a 96%specificity were reached by taking into account the QTm/RR slopeat night, the QTc interval and the mean heart rate during theday. Conclusion QT interval variables obtained from 24-h ECG recordingsimprove long QT syndrome diagnosis by showing an increased nocturnalventricular repolarization rate-dependence in genotyped chromosome11-linked patients.     

Differential diagnosis between LQT1 and LQT2 by QT/RR relationships using 24-hour Holter monitoring: A multicenter cross-sectional study

Background

The clinical course and therapeutic strategies in the congenital long QT syndrome (LQTS) are genotype-specific. However, accurate estimation of LQTS genotype is often difficult from the standard 12-lead ECG.

Objectives

This study aims to evaluate the utility of QT/RR slope analysis by the 24-hour Holter monitoring for differential diagnosis of LQTS genotype between LQT1 and LQT2.

Methods

This cross-sectional study enrolled 54 genetically identified LQTS patients (29 LQT1 and 25 LQT2) recruited from three medical institutions. The QT-apex (QTa) interval and the QT-end (QTe) interval at each 15-second were plotted against the RR intervals, and the linear regression (QTa/RR and QTe/RR slopes, respectively) was calculated from the entire 24-hour and separately during the day or night-time periods of the Holter recordings.

Results

The QTe/RR and QTa/RR slopes at the entire 24-hour were significantly steeper in LQT2 compared to those in LQT1 patients (0.262 ± 0.063 vs. 0.204 ± 0.055, p = .0007; 0.233 ± 0.052 vs. 0.181 ± 0.040, p = .0002, respectively). The QTe interval was significantly longer, and QTe/RR and QTa/RR slopes at daytime were significantly steeper in LQT2 than in LQT1 patients. The receiver operating curve analysis revealed that the QTa/RR slope of 0.211 at the entire 24-hour Holter was the best cutoff value for differential diagnosis between LQT1 and LQT2 (sensitivity: 80.0%, specificity: 75.0%, and area under curve: 0.804 [95%CI = 0.68–0.93]).

Conclusion

The continuous 24-hour QT/RR analysis using the Holter monitoring may be useful to predict the genotype of congenital LQTS, particularly for LQT1 and LQT2.

     

Differential diagnosis between LQT1 and LQT2 by QT/RR relationships using 24‐hour Holter monitoring: A multicenter cross‐sectional study

BackgroundThe clinical course and therapeutic strategies in the congenital long QT syndrome (LQTS) are genotype‐specific. However, accurate estimation of LQTS genotype is often difficult from the standard 12‐lead ECG.ObjectivesThis study aims to evaluate the utility of QT/RR slope analysis by the 24‐hour Holter monitoring for differential diagnosis of LQTS genotype between LQT1 and LQT2.MethodsThis cross‐sectional study enrolled 54 genetically identified LQTS patients (29 LQT1 and 25 LQT2) recruited from three medical institutions. The QT‐apex (QTa) interval and the QT‐end (QTe) interval at each 15‐second were plotted against the RR intervals, and the linear regression (QTa/RR and QTe/RR slopes, respectively) was calculated from the entire 24‐hour and separately during the day or night‐time periods of the Holter recordings.ResultsThe QTe/RR and QTa/RR slopes at the entire 24‐hour were significantly steeper in LQT2 compared to those in LQT1 patients (0.262 ± 0.063 vs. 0.204 ± 0.055, p = .0007; 0.233 ± 0.052 vs. 0.181 ± 0.040, p = .0002, respectively). The QTe interval was significantly longer, and QTe/RR and QTa/RR slopes at daytime were significantly steeper in LQT2 than in LQT1 patients. The receiver operating curve analysis revealed that the QTa/RR slope of 0.211 at the entire 24‐hour Holter was the best cutoff value for differential diagnosis between LQT1 and LQT2 (sensitivity: 80.0%, specificity: 75.0%, and area under curve: 0.804 [95%CI = 0.68–0.93]).ConclusionThe continuous 24‐hour QT/RR analysis using the Holter monitoring may be useful to predict the genotype of congenital LQTS, particularly for LQT1 and LQT2.     

Relation between ventricular repolarization duration and cardiac cycle length during 24-hour Holter recordings. Findings in normal patients and patients with long QT syndrome.

BACKGROUND. The interval from the R wave to the maximum amplitude of the T wave (RTm) contains the heart rate dependency of ventricular repolarization. METHODS AND RESULTS. A computer algorithm was developed to quantify the RTm and preceding RR intervals for each of more than 50,000 beats on 24-hour ambulatory electrocardiographic (Holter) recordings to evaluate the dynamic relation between repolarization duration and cycle length. The relation of RTm to the preceding RR interval (RTm/RR slope) was determined by the best-fit linear regression equation between these two parameters. Eleven normal subjects and 16 patients with long QT syndrome (LQTS) were investigated. Six of the normal subjects had Holter recordings obtained before and after beta-blocker therapy. beta-Blockers were associated with a significant (p = 0.005) reduction in the RTm/RR slope from 0.13 +/- 0.02 to 0.10 +/- 0.02. The mean value of the RTm/RR slope was significantly (p = 0.003) larger in the LQTS patients (0.21 +/- 0.08) than in normal subjects (0.14 +/- 0.03). CONCLUSIONS. These findings indicate that 1) quantification of the dynamic relation between ventricular repolarization and RR cycle length can be obtained on a large number of Holter-recorded heart beats; 2) beta-blockers reduce the RTm/RR slope in normal patients; and 3) LQTS patients have an exaggerated delay in repolarization at long RR cycle lengths.     

甲状腺功能亢进与心室复极化关系的meta分析

目的分析甲状腺功能亢进（甲亢）对于心室复极化的影响。方法：计算机检索PubMed、EMBASE、中国期刊全文数据库、维普数据库、万方数据库于1960年～2013年12月公开发表的相关文献,用Revman 5．2进行meta分析。结果：分析纳入7项病例对照研究,甲亢病例425例,对照组366例。甲亢时心率校正的QT间期（QTc）较对照组显著延长（MD=18．46,95％CI：10．19-26．73,P〈0．01）,心率校正的QT离散度（QTcd）也显著延长（MD=19．38,95％CI：13．59-25．18,P〈0．01）。QT间期与对数化后的促甲状腺素（TSH）呈负相关（Pearson相关系数r=-0．748,P〈0．01;加权线性回归系数R2=0．557,P〈0．01）。结论：甲亢患者的心室复极化显著延长。     

Clinical significance of heart rate variability for the monitoring of cardiac autonomic neuropathy in end-stage renal disease patients

Background and aimsThe aim of this study is to determine whether the measurement of continuous heart rate variability (HRV) is useful in the evaluation of cardiac autonomic neuropathy (CAN) in end-stage renal disease (ESRD) patients.Methods and resultsThis cross-sectional study was performed at Seoul St. Mary's hospital between June 2017 and February 2018. Seventy-seven ESRD patients, and 29 healthy controls (HCs) were asked to wear a continuous ambulatory HRV monitor for 24 h. General cardiac function was evaluated using transthoracic echocardiogram (TTE), pulse wave velocity (PWV), coronary calcium scoring (CCS), and 24-h ambulatory blood pressure monitoring (ABPM). HRV parameters of ESRD patients and HCs, and the correlation of HRV parameters with cardiovascular screening methods were observed. All HRV parameters were significantly decreased in ESRD patients compared to HCs (P < 0.001). In the correlation analysis between TTE results and HRV parameters, 24-h standard deviation of all N–N intervals (24SDNN), 24-h standard deviation of sequential 5-min N–N interval means (24DANN) and Low Frequency Power/High Frequency Power (LF/HF) ratio showed negative correlations with E/e’, LAVI and TR velocity which are representative indices for the diastolic function of the heart (P < 0.05). HRV parameters showed negative correlations with baPWV, CCS, and 24-h ABPM results as well (P < 0.05). Hemoglobin and serum albumin showed positive correlations with HRV parameters, and glucose, BUN, creatinine, and iPTH levels showed negative correlations (P < 0.05).ConclusionContinuous HRV monitoring may be a useful tool for the evaluation of CAN in ESRD.