Circadian Variation and Waking Hour Dynamics of the QT Interval

Background: The incidence of sudden cardiac death is maximal in the morning hours. Although ventricular arrhythmias have been implicated as a potential mechanism, and several neurohumoral factors affecting myocardial excitability have been shown to be raised in the early morning hours, it is not known if there is any circadian variation in the dynamics of ventricular repolarization when studied on a beat-to-beat basis. The objective of this study was to examine the range, diurnal variations, and circadian distribution of the variability of the QT interval in healthy subjects. Method: We developed and validated a new method for continuous measurement of QT intervals from 24-hour Holter recordings. The QT intervals measured semi-automatically were corrected by a linear regression formula derived independently for each patient from his own QT and RR values in 32 healthy males (20 ± 0.4 years). QT variability was assessed by the mean standard deviation of the average of consecutive uncorrected QT intervals (SDA-QT Index) and corrected QT intervals (SDA-QTc index) over 5-minute segments. The rate-dependent changes of the QT interval were studied as a function of the slope of the regression line between the QT and RR values. Results: The average QTc range was mean (SD) 79 (± 28) ms; the average maximal QTc interval was 481 (± 24) ms. The 95% upper confidence limit for the mean 24-hour QTc interval was 443 ms. The RR, QT, and QTc intervals were longer, while the SDA-QT and SDA-QTc indices were shorter during sleep. Hourly averages of the SDA-QT and SDA- QTc index revealed a sudden increase in QT variability in the first hour of waking (P < 0.0001 and P = 0.006). Conclusion: The dynamic behavior of the QT interval shows significant diurnal variations. The maximal QTc interval over 24 hours is longer than previously assumed. The period shortly following awakening is characterized by a peak in the variability of the QT interval. These changes may be indicative of autonomic instability during the early waking hours and correspond with the peak incidence of sudden arrhythmic death.     

过伸型胫骨平台骨折的临床治疗

目的探讨过伸型胫骨平台骨折的临床治疗。方法回顾性分析2013年11月—2017年12月南京医科大学第一附属医院治疗的12例过伸型胫骨平台骨折。其中男性4例,女性8例;年龄24～65岁,平均53.6岁;致伤原因均为道路交通伤。患者采用屈曲位复位,植骨后使用内外侧钢板固定。观察患者术后平台后倾角、美国特种外科医院膝关节功能评分(HSS评分)、关节屈曲度以及并发症情况。结果术后X线片显示均获得解剖复位。术后均无膝关节反曲,患者均得到随访6～18个月,平均9.7个月。骨折愈合时间8～12周,平均10.0周。所有患者术后测量后倾角5°～9°(平均7.9°),术后半年5°～10°(平均7.7°)。HSS评分90～98分(平均93.6分)。术后半年关节屈曲度120°～145°(平均131°),伸直均为0°。术后无一例发生钢板及螺钉断裂现象。结论通过恢复正常后倾角及关节面平整,充分植骨及锁定钢板固定治疗过伸型胫骨平台骨折,效果良好,值得临床推荐。     

Cochlear implant assessment and candidacy for children with partial hearing

Children who have partial hearing (PH) in the low frequencies and profound sensorineural hearing loss in the high frequencies can present a challenge to cochlear implant (CI) teams in terms of referral, assessment, and candidacy. Neither clinical criteria nor optimal timing for implantation has been explored in the literature. Data from both the Hearing Implant Centres of Birmingham Children's Hospital and St Thomas’ Hospital indicate that it is clinically appropriate to implant children with PH; they perform better with CIs than with hearing aids, even if their hearing is not fully preserved. We have also found that children need early access to high frequency sound in order to reach their full potential.     

Functional analysis of congenital stationary night blindness type-2 CACNA1F mutations F742C, G1007R, and R1049W

Congenital stationary night blindess-2 (incomplete congenital stationary night blindness (iCSNB) or CSNB-2) is a nonprogressive, X-linked retinal disease which can lead to clinical symptoms such as myopia, hyperopia, nystagmus, strabismus, decreased visual acuity, and impaired scotopic vision. These clinical manifestations are linked to mutations found in the CACNA1F gene which encodes for the Ca(v)1.4 voltage-gated calcium channel. To better understand the physiological effects of these mutations, three missense mutants, F742C, G1007R and R1049W, previously shown to be mutated in patients with CSNB-2, were transiently expressed in human embryonic kidney (HEK) tsA-201 cells and characterized using whole-cell patch clamp. The G1007R mutation is located in transmembrane segment 5 (S5) of domain III and R1049W is located in the extracellular linker between S5 and the P-loop of domain III. Both mutants produced full length proteins that targeted to the membrane but did not support ionic currents. In 20 mM Ba(2+), F742C (S6 domain II) produced a approximately 21 mV hyperpolarizing shift in half activation potential (V(a[1/2])) and a approximately 23 mV hyperpolarizing shift in half inactivation potential (V(h[1/2])). Additionally, F742C displayed slower inactivation kinetics and a smaller whole cell conductance (G(max)). In physiological 2 mM Ca(2+), F742C produced a approximately 19 mV hyperpolarizing shift in V(a[1/2]). These findings suggest that the pathology of CSNB-2 in patients with these missense mutations in the Ca(v)1.4 calcium channel is the result in either a gain of function (F742C) or a loss of function (G1007R, R1049W).     

胫骨去后倾化截骨在合并后倾角异常增大患者前交叉韧带翻修术中的临床应用北大核心CSCD

目的探讨胫骨去后倾化截骨加前交叉韧带(anterior cruciate ligament,ACL)翻修术治疗ACL初次重建术后失效合并胫骨平台后倾角(posterior tibial slope,PTS)异常增大患者的临床疗效。方法回顾分析2018年1月—2020年1月收治且符合选择标准的9例ACL初次重建术后失效合并PTS异常增大(≥17°)患者的临床资料。男8例,女1例;年龄21~42岁,中位年龄30岁。9例患者Lachman试验均为阳性;轴移试验阴性6例,Ⅰ度阳性2例,Ⅱ度阳性1例。PTS为(17.78±1.09)°、胫骨平台前移距离(anterior tibial translation,ATT)为(11.58±1.47)mm。国际膝关节文献委员会(IKDC)评分为(51.0±3.8)分,Lysholm评分为(49.7±4.6)分、Tegner评分为(3.7±0.7)分。初次重建至翻修时间为12~33个月,平均19.6个月。采用胫骨去后倾化截骨加ACL翻修术治疗。术后采用IKDC评分、Lysholm评分及Tegner评分评价膝关节功能改善情况,行Lachman试验、轴移试验评价膝关节稳定性,测量PTS及ATT观察膝关节形态学变化。结果术后切口均Ⅰ期愈合,未出现切口感染、脂肪液化、坏死以及下肢深静脉血栓形成、神经血管损伤等并发症。9例患者均获随访,随访时间12~36个月,平均25.8个月。末次随访时Lachman试验和轴移试验均为阴性。IKDC评分为(85.0±4.0)分、Lysholm评分为(87.7±2.8)分、Tegner评分为(6.8±0.7)分,PTS减小至(9.89±0.60)°,ATT缩短至(0.91±0.29)mm,与术前比较差异均有统计学意义(P<0.05)。结论胫骨去后倾化截骨加ACL翻修术治疗ACL初次重建术后失效合并PTS异常增大患者早期临床疗效明确,在改善膝关节稳定性同时可较好地维持正常膝关节形态。     

最大ST段／心率斜率及其在冠心病康复中的应用（Ⅰ）

心电运动试验是诊断冠心病及心脏功能评估的重要方法,然常规运动试验有局限性.我们为探讨最大ST段/心率斜率(斜率)与心肌缺血的确切关系及意义,从实用角度出发,对斜率测试方法进行改良,对其诊断作了研究.对22例患者作下列两项检查:平板运动试验并测试最大ST段/心率斜率和2周内行静息与运动心肌灌注SPECT.结果发现:斜率在检测冠心病程度上准确度高于ST段压低及其它常规分级运动试验指标.     

Extramedullary Guides Versus Portable,Accelerometer-Based Navigation for Tibial Alignment in Total Knee Arthroplasty: A Randomized,Controlled Trial: Winner of the 2013 HAP PAUL Award

Extramedullary (EM) tibial alignment guides have demonstrated a limited degree of accuracy in total knee arthroplasty (TKA). The purpose of this study was to compare the tibial component alignment obtained using a portable, accelerometer-based navigation device versus EM alignment guides. One hundred patients were enrolled in this prospective, randomized controlled study to receive a TKA using either the navigation device, or an EM guide. Standing AP hip-to-ankle and lateral knee-to-ankle radiographs were obtained at the first, postoperative visit. 95.7% of tibial components in the navigation cohort were within 2° of perpendicular to the tibial mechanical axis, versus 68.1% in the EM cohort (P < 0.001). 95.0% of tibial components in the navigation cohort were within 2° of a 3° posterior slope, versus 72.1% in the EM cohort (P = 0.007). A portable, accelerometer-based navigation device decreases outliers in tibial component alignment compared to conventional, EM alignment guides in TKA.     

Extreme Variability in Posterior Slope of the Proximal Tibia: Measurements on 2395 CT Scans of Patients Undergoing UKA?

Data regarding the posterior slope of the tibia (PTS) are limited and sometimes conflicting. The purpose of this study was to determine the native posterior tibial slope in patients undergoing a medial or lateral UKA. A retrospective review was performed on 2395 CT scans in patients indicated for UKA, and the PTS of the osteoarthritic compartment was measured relative to a plane set perpendicular to the sagittal, tibial mechanical axis. The mean preoperative PTS in patients undergoing medial UKA was 6.8° + 3.3°, with 34.3% between 4° and 7°. The mean preoperative PTS in patients undergoing lateral UKA was 8.0° + 3.3°, with 27.5% between 4° and 7°. If attempting to recreate a patient's preoperative tibial slope, a routine target of 5° to 7° will produce a posterior slope less than the patient's native anatomy in 47% of patients undergoing UKA. This is the first, large CT-based review of posterior slope variation of the proximal tibia in patients undergoing UKA.