QT intervals as an index of high serum calcium in hypercalcemia

The relationship between QT interval and serum calcium concentration (s-Ca) was examined in 9 hypercalcemic (s-Ca greater than 11 mg/dl) patients. Three QT intervals corrected by Bazett's formula were used for the analysis: the intervals from the beginning of the QRS to the onset (QoTc), the apex (QaTc), and the end of T wave (QeTc). The measurements of s-Ca and other electrolytes were made on the blood sample taken on the same day of the electrocardiogram (ECG) recordings. The normal range of s-Ca and three QTc intervals was determined in 50 outpatients with no cardiac disease. Three QT intervals in the hypercalcemic patients were significantly shortened with a diminution in the s-Ca. The QTc intervals showed significant negative correlation with s-Ca. Sensitivity of QoTc, QaTc, and QeTc in predicting high s-Ca was 83%, 57%, and 39%, respectively, and specificity was 100%, 100%, and 89%. The PQ interval tended to be prolonged in the case of hypercalcemia, but the change was statistically insignificant. These observations suggest that QT intervals can serve as an indicator of high s-Ca and that the QoTc seems to be a good indicator of the three QTc's.     

Reliability of QT intervals as indicators of clinical hypercalcemia

Reliability of corrected QT intervals (QoTc, QaTc, and QeTc) as indicators of clinical hypercalcemia was assessed in 14 hypercalcemic patients. Hypercalcemia was severe to extreme (serum calcium 14.9 to 22.8 mg/dl) in 11, moderate (13.4 mg/dl) in 1, and mild (12.2 and 11.8 mg/dl) in 2 patients. QT intervals during hypercalcemia were compared with those during normocalcemia either before or after development of hypercalcemia. QeTc interval showed neither significant correlation with serum calcium nor any consistent pattern of change with development of hypercalcemia or normalization of serum calcium. In contrast, QoTc and QaTc intervals shortened with development of hypercalcemia and returned toward normal with normalization of serum calcium in all the patients, and showed significant correlation with serum calcium (QoTc: r = -0.77, p less than 0.001, n = 35; QaTc: r = 0.82, p less than 0.001, n = 35). QaTc was short (less than 0.30 s) in all the ECGs in severe and moderate hypercalcemia and in 2 of the 5 ECGs in mild hypercalcemia. Combination of short QoTc (less than 0.18 s) and short QaTc was found to be highly specific for, and was present in 65% of ECGs, in moderate and severe hypercalcemia. Combination of normal QoTc (greater than 0.18 s) and normal QaTc (greater than 0.30 s) was not observed in moderate or severe hypercalcemia. We conclude that QoTc and QaTc intervals are reliable indicators of clinical hypercalcemia.     

右室心尖部和间隔部S1S2刺激电重构后对跨室壁复极离散的影响

目的通过观察右室不同部位S1S2刺激电重构后对室壁QRS间期、QRS波起始至T波顶点间期（QTp）、QT间期和T波峰末间期（Tp2e）影响,分析不同部位起搏对跨室壁复极离散的影响。方法选取因阵发性室上性心动过速拟行射频消融患者18例,随机分心尖部刺激组（RVA组,n=9）和间隔部刺激组（RVS组,n=9）,分别行S1S2刺激,测量每组体表起搏心电图V1导联S2刺激的QRS间期、QRS波起始至T波顶点间期（QTp）、QT间期和T波峰末间期（Tp2e）并进行统计分析。结果 RVS组较RVA组的QRS间期、QTp无差异、至S1S2500/260ms后QT间期及Tp2e明显减低;两组均随S1S2刺激间期缩短QT间期及Tp2e明显增大,而QRS间期及QTp无差异。结论电重构后RVS组比RVA组心室跨壁复极离散低、心脏同步性较好,是选择起搏的较好部位。     

心动过缓患者QT与RR间期的相关变化

分析33名病窦综合症和高度房室传导阻滞所致心动过缓患者的24小时动态心电图。用直线回归方程计算QT和RR间期回归直线的斜率(slode).分为RR间期≤1.4s(slopeL)和>1.4s(slope2)。发现所有患者的slope_2(0.0086±0.0039)明显小于sIope_1(0.0785±0.0057;P<0.001)。12名校正后QT间期(QT_c)≥0.44s患者(B组)的slope_1(0.0969±0.0083)和slope_2(0.0198±0.0049)均明显大于QT_c<0.44s患者(A组)的slope_1(0.063±0.0063;P<0.01)和slope_2(0.0022±0.0028;P<0.01)。slope_1和slope_2与QT_c呈正相关。表明心动过缓患者.随着心率的减慢,QT间期延长的量逐渐减少,与QT间期正常组相比,QT延长组当RR间期延长时.QT间期有较大的延长。     

Subject-specific heart rate dependency of electrocardiographic QT, PQ, and QRS intervals

Although heart rate dependency of QT interval is well known, the relationship of other electrocardiogram (ECG) parameters to heart rate has been researched less intensively. This study investigated the heart rate dependencies of QT interval, PQ interval, and QRS width in 40 healthy subjects (18 women; mean age, 30.4 +/- 8.1 years). In each subject, 3 long-term (approximately 13 hours) 12-lead ECGs were obtained for 3 day-time periods with gaps of 2 to 3 weeks between repeated recordings. In each recording, approximately 230 ECG measurements of QT interval, PQ interval, and QRS width were made, each preceded by stable heart rate. For each recording, linear regression slopes of QT/RR, PQ/RR, and QRS/RR relationships were obtained. Intrasubject SDs of individual values were compared with intersubject SDs of intrasubject means to test the individuality of the relationships. The intrasubject means of the slope values were also compared between sexes. The individual SDs of the QT/RR regression slopes were 0.0116 +/- 0.0065, whereas the population SD of intrasubject means was 0.0245 (P = 3.6 x 10(-15)). For the PQ/RR slopes and QRS/RR slopes, these values were 0.0085 +/- 0.0050 vs 0.0314 (P = 7.9 x 10(-28)) and 0.00189 +/- 0.00157 vs 0.00550 (P = 2.6 x 10(-17)), respectively. The QT/RR slopes were steeper in women than in men (0.194 +/- 0.019 vs 0.168 +/- 0.022, 0.0005), whereas the QRS/RR slopes were, on average, negative in women while positive in men (-0.00138 +/- 0.0045 vs 0.00335 +/- 0.0054, P = .005). There were no sex differences in the PQ/RR slopes (0.054 +/- 0.032 in women vs 0.055 +/- 0.031 in men, P = .95). Thus, not only the heart rate dependency of QT interval but also the rate dependencies of PQ interval and of QRS width show high intrasubject stability with substantial intersubject differences.     

不同部位起搏对体表心电图有关参数的影响

目的观察心脏不同部位起搏对体表心电图有关参数的影响。方法 10只健康猪,分别在右房(RA)起搏、右室心尖部心内膜起搏(RVEndo)及左室心外膜(LVEpi)起搏,记录并测量不同部位起搏后体表心电图12个导联的QRS波时限、QT间期、JT间期和T波峰-末间期(Tpe),计算Tpe平均值(TpeAVE)、Tpe最大值(TpeMAX)。结果 LVEpi起搏时QT间期、JT间期大于RA及RVEndo起搏时(P均<0.05);LVEpi起搏时TpeAVE,TpeMAX大于RA及RVEndo起搏时(P均<0.05),而RA与RVEndo起搏时此两指标无差异。结论 LVEpi起搏可能会增加健康心室整体复极离散。     

高盐摄入及补钾对健康成人QT间期离散度的影响

目的 探讨慢性盐负荷及补钾对健康成人QT间期离散度(QTd)、T波峰-末间期(Tp-Te)的影响.方法 选取64例28～60岁血压正常者参与为期3周的慢性盐负荷及补钾试验,包括基线调查3 d(基线期),低盐饮食(低盐期)、高盐饮食(盐负荷期)和高盐补钾饮食(高盐补钾期)各7d.各期均测量体质量、血压,记录心电图,测量QT间期、QTd、校正QTd (QTdc)及Tp-Te.结果 低盐期QTd、QTdc、Tp-Te均＜基线期(QTd,45.6± 15.6对52.1 ±23.4,P＜0.05;QTdc,55.6±19.4对61.6±23.6,P＜0.05;Tp-Te,79.8±8.5对85.0±10.6,P＜0.01);盐负荷后QTdc、Tp-Te＞低盐期(QTdc,60.3±19.4对55.6±19.4,P＜0.05;Tp-Te,83.0±10.1对79.8±8.5,P＜0.01);在高盐摄入的基础上大剂量口服补钾QTd、QT-dc、Tp-Te均较高盐期缩小(QTd,42.6±15.1对47.4±19.0,P＜0.05;QTdc,52.2±18.0对60.3±19.4,P＜0.05;Tp-Te,79.1 ±8.5对83.0±10.1,P＜0.01).结论 盐负荷可升高血压并使QTd、QTde及Tp-Te增加,补钾可以减低高盐对QTd、QTdc、Tp-Te的影响,提示补钾可通过缩短心肌复极时间,降低心脏复极不均一性,对心律失常可能有一定预防作用.     

Beat‐to‐Beat QT Interval Variability Is Primarily Affected by the Autonomic Nervous System

Background : Beat‐to‐beat QT interval variability is associated with life‐threatening arrhythmias and sudden death, however, its precious mechanism and the autonomic modulation on it remains unclear. The purpose of this study was to determine the effect of drugs that modulate the autonomic nervous system on beat‐to‐beat QT interval. Method : RR and QT intervals were determined for 512 consecutive beats during fixed atrial pacing with and without propranolol and automatic blockade (propranolol plus atropine) in 11 patients without structural heart disease. Studied parameters included: RR, QTpeak (QRS onset to the peak of T wave), QTend (QRS onset to the end of T wave) interval, standard deviation (SD) of the RR, QTpeak, and QTend (RR‐SD, QTpeak‐SD, and QTend‐SD), coefficients of variation (RR‐ CV, QTpeak‐CV, and QTend‐CV) from time domain analysis, total power (TP; RR‐TP, QTpeak‐TP, and QTend‐TP), and power spectral density of the low‐frequency band (LF; RR‐LF, QTpeak‐LF, and QTend‐LF) and the high‐frequency band (HF; RR‐HF, QTpeak‐HF and QTend‐HF). Results : Administration of propranolol and infusion of atropine resulted in the reduction of SD, CV, TP, and HF of the QTend interval when compared to controlled atrial pacing (3.7 ± 0.6 and 3.5 ± 0.5 vs 4.8 ± 1.4 ms, 0.9 ± 0.1 and 0.9 ± 0.1 vs 1.2 ± 0.3%, 7.0 ± 2.2 and 7.0 ± 2.2 vs 13.4 ± 8.1 ms², 4.2 ± 1.4 and 4.2 ± 1.2 vs 8.4 ± 4.9 ms², respectively). Administration of propranolol and atropine did not affect RR interval or QTpeak interval indices during controlled atrial pacing. Conclusions : Beat‐to‐beat QT interval variability is affected by drugs that modulate the autonomic nervous system.     

Acute electrophysiologic effects of an HT2-serotonin antagonist,ketanserin, in humans

Summary The acute electrophysiologic effects of an intravenous bolus of ketanserin, a 5HT₂ serotonin blocker, were studied in ten patients (four females, six males) during invasive electrophysiology. Following baseline electrophysiologic measurements during sinus rhythm and fixed-rate atrial pacing at 600 ms, a bolus of 0.2 mg/kg ketanserin was given over a 3-minute period. After 30 minutes all measurements were repeated. Systemic blood pressure was measured at regular intervals throughout. During sinus rhythm, there was no significant change in the basic cycle length or in the PA, AH, HV, QRS, QT, and QTc intervals. During atrial pacing there was a nonsignificant increase in the QT interval, from 342±13 ms to 366±16 ms, and a significant increase in the QTc interval, from 422±27 ms to 449±29 ms (p<0.05). There was no reduction in blood pressure. Thus ketanserin produced a significant prolongation of the QTc interval, in the absence of hypokalemia, in humans.     

胺碘酮治疗室性心律失常对TpTe的影响

目的:观察胺碘酮治疗室性心律失常治疗时程对心电图T波顶点至T波终点的宽度(T-peak to T-end interval,TpTe)的影响。方法: 85例室性心律失常患者,胺碘酮150 mg静脉注射,继以1 mg/kg,持续6 h,后减量至0.5 mg/kg,持续48 h后停用,静脉胺碘酮24 h后,开始同时加用口服胺碘酮,每次0.2 g ,1日3次,1周;每次0.2 g,每日2次,1周; 0.2 g每日1次维持,观察用药后1、3、7、10、14、17、21 d心率、TpPe、QT、TpPe-c、QTc变化。结果: 心律失常控制率达92%（78/85）。治疗有效组自治疗后第1天心率明显减慢,QT间期明显延长（P≤0.01）,14 d时达最大值,后趋于平稳,但未见统计学意义差异。但整个治疗时程中胺碘酮对TpTe、TpTe-c及QTc未见有统计学意义的改变。结论: 胺碘酮治疗室性心律失常不影响TpTe,TpPe独立于心率,不需要心率校正。     

糖尿病与冠心病人QT间期及离散度变化的相关性研究

糖尿病和冠心病人的QTc和QTd明显长于非患病病者，町为预测心血管事件的发生提供依据。方法：采用病例一病例对照的研究方法，将130例糖尿病、冠心病病人分为冠心病组（G1）53例、糖尿病组（C2）47例、糖尿病合并冠心病组（G3）30例，对比QTc和QTd的变化及其与糖尿病和冠心病的相关性。结果：G3组病人的QTc和QTd较G1、G2组明显延长（P=0．010和0．017），相关分析结果显示QTd与QTc明显相关（R=0．252P=0．004），糖尿病或CHD病人的QTc与是否合并CHD或糖尿病独立相关（？=0．368和0．336P=0．007和0．046）。结论：糖尿病对心肌电活动的影响与心肌缺血引起的相近，二者合并出现后加重了心肌电活动的l不稳定性。     

关于Q—T间期测量导联选择的探讨

为寻求１２导联心电图中能测出最大Ｑ－Ｔ值的导联，观察正常人和急性心肌梗塞病人各１００例心电衅１２导联Ｑ－５ｃ间其。结果表明：不论是正常人或包性心肌梗塞病，也不论心肌梗塞发生部位，其Ｑ－Ｔｃ均值均以Ｖ２，Ｖ３为最大，最大Ｑ－Ｔｃ差值的均值也以Ｖ２，Ｖ３为最小，且此二导联Ｕ波对Ｑ－Ｔ测量的干扰较小。     

QTc、JTc间期与QT/TQ比的正常值及临床意义

本文报道1 309名正常人的QTc间期(<440ms),JTc间期(<360ms)和QT/TQ比(<1.1),并与急性心肌梗塞(AMI)和单纯完全性左、右束支传导阻滞(CLBBB、CRBBB)患者对比,发现AMI、CLBBB、CRBBB患者QTc和QT/TQ比均明显大于正常组(P<0.01),而JTc间期仅AMI组显著长于正常组(P<0.01)。结果提示,JTc间期较QFc间期能更好地反映心室肌复极状态,对心室除极顺序正常和异常均适用。若能综合分析以上三值,对临床指导意义更大。     

特发性室性心动过速患者QT间期与RR间期关系的研究

为研究特发性室性心动过速（ＩＶＴ）患者日常活动中的心室复极状况，对１７例左室ＩＶＴ（ＩＬＶＴ，即ＩＬＶＴ组）、１０例右室ＩＶＴ（ＩＲＶＴ，即ＩＲＶＴ组）、１７例正常人（正常对照组）进行２４小时动态心电图检查，测量ＱＴ间期，计算其与ＲＲ间期的关系。三组间平均、最大、最小ＱＴ间期及校正ＱＴ间期均无显著性差异。ＩＲＶＴ组ＱＴ间期与ＲＲ间期直线回归方程的斜率值较正常对照组高（０．２４３±０．０４３ｖｓ０．２０１±０．０３９，Ｐ＜０．０５），ＩＬＶＴ组斜率值与正常对照组比较无显著性差异（０．１９０±０．０４３ｖｓ０．２０１±０．０３９，Ｐ＞０．０５）。尽管ＩＲＶＴ的患者经检查心脏未见明显器质性病变，但存在心室复极的心率适应性异常的改变，此可能是该类患者心肌电不稳定的原因之一     

冠状动脉旁路移植术对QT、QTc、JT离散度的影响

目的　探讨冠状动脉旁路移植术 (Coronary artery bypass graftings,CABG)对冠心病患者 QT间期离散度(QTd)、QTc离散度 (QTcd)及 JT离散度 (JTd)的影响。方法　测定 33例 CABG术前和术后的 QTd为 CABG组 ,并以 33例确诊为冠心病行冠状动脉造影 ,而暂未行 CABG手术和装支架的病人作对照组。结果　 1CABG前和对照组比较 QTd无显著增大 (P>0 .0 5 )。 2 CABG组术后病人的 QTd、QTcd及 JTd显著减小 (P<0 .0 5 )。 3对照组冠状动脉造影术后 QTd、QTcd及 JTd与术前比较 ,无明显改变 (P>0 .0 5 )。结论　 CABG能使 QTd、QTcd及 JTd减小     

Epinephrine Bolus Test in Detecting Long QT Syndrome Mutation Carriers with Indeterminable Electrocardiographic Phenotype

Background: In long QT syndrome (LQTS), prolonged and heterogeneous ventricular repolarization predisposes to serious arrhythmias. We examined how QT intervals are modified by epinephrine bolus in mutation carriers of three major LQTS subtypes with indefinite QT interval. Methods: Genotyped, asymptomatic subjects with LQTS type 1 (LQT1; n = 10; four different KCNQ1 mutations), type 2 (LQT2; n = 10; three different HERG mutations), and type 3 (LQT3; n = 10; four different SCN5A mutations), and healthy volunteers (n = 15) were examined. Electrocardiogram was recorded with body surface potential mapping system. After an epinephrine 0.04 μg/kg bolus QT end, QT apex, and T‐wave peak‐to‐end (Tpe) intervals were determined automatically as average of 12 precordial leads. Standard deviation (SD) of the 12 channels was calculated. Results: Heart rate increased 26 ± 10 bpm with epinephrine bolus, and similarly in all groups. QT end interval lengthened, and QT apex interval shortened in LQTS and normals, leading to lengthening of Tpe interval. However, the lengthening in Tpe was larger in LQTS than in normals (mean 32 vs 18 ms; P < 0.05) and SD of QT apex increased more in LQTS than in normals (mean 23 vs 7 ms; P < 0.01). The increase in Tpe was most pronounced in LQT2, and in SD of QT apex in LQT1 and LQT2. Conclusions: Abrupt adrenergic stimulation with a moderate dose of exogenous epinephrine affects ventricular repolarization in genotype‐specific fashion facilitating distinction from normals. This delicate modification may help in diagnosing electrocardiographically silent mutation carriers when screening LQTS family members. Ann Noninvasive Electrocardiol 2011;16(2):172–179     

心脏病室性心律失常患者Tp-e间期、Tp-e/Q-T比值的研究

目的探讨器质性心脏病患者Tp-e间期、Tp-e/Q-T比值与室性心律失常的关系。方法选择器质性心脏病患者85例,分为两组,器质性心脏病室性心律失常组(A组)43例,并进一步按LOWN分级分为两个亚组,A1组(LOWN2-3级)20例,A2组(LOWN3级以上)23例;器质性心脏病无室性心律失常组(B组)42例。另选择健康体检者40例为正常对照组(C组)。采用常规12导联同步心电图及24小时动态心电图分析比较各组的Q-T间期、Q-Tc间期、Tp-e间期、Tp-ec间期和Tp-e/Q-T测值。结果 A组Q-T间期、Q-Tc间期、Tp-e间期、Tp-ec间期、Tp-e/Q-T测值比C组显著升高,差异有统计学意义(P<0.05),而Q-Tc间期、Tp-e间期、Tp-ec间期、Tp-e/Q-T比B组显著升高,差异有统计学意义(P<0.05)。上述各测值A2组比A1组显著升高,差异有统计学意义(P<0.05或P<0.01)。结论 Tp-e间期、Tp-e/Q-T等心电学指标与室性心律失常的发生有关,对室性心律失常的发生具有预测意义。