Golzari Houtan, Dawson Neal V, Speroff Ted, Thomas Charles
Department of Medicine, MetroHealth Medical Center, Cleveland, Ohio, USA.
Conn Med. 2007 Aug;71(7):389-97.
Prolonged QTc (corrected QT) interval and torsades de pointes (TDP) are associated with hypocalcemia, hypomagnesemia, hypokalemia, possibly alkalosis and may result in syncope and sudden cardiac death.
The purpose of this study was to determine the prevalence of prolonged QTc intervals on admission electrocardiograms (ECGs) and its correspondence with simultaneous admission electrolyte values, adjusted for admission diagnoses, comorbidities, other ECG abnormalities, and medications potentially associated with QTc prolongation.
Consecutive patients (N=258) admitted to a general medical service with the admission electrolytes and ECGs. For each ECG, QTc was classified in 10 msec. intervals from QTc > or = 450 to QTc > or = 500 msec. as determined by the electronically measured QTc (Marquette ECG system). Medical records were reviewed for prespecified admission diagnoses, comorbidities and medications associated with QTc prolongation. The correspondence of admission electrolyte abnormalities and QTc prolongation was evaluated using univariate and multivariate statistical methods.
The prevalence of abnormal QTc intervals varied by the criterion applied, ranging from 25.2%, using the most lenient criterion of abnormality (QTc > or =450 msec.), to 3.5%, when the most restrictive criterion was applied (QTc > or = 500 msec.). In univariate analyses, there were no significant associations between QTc intervals and admission values for any of the electrolytes. In multivariate analyses, after adjusting for age, gender, ECG abnormalities and other covariates, none of the admission electrolyte values were significantly associated with prolonged QTc.
Using conventional criteria, electronically measured prolonged QTc intervals were quite common at the time of admission among general medicine service patients, hospitalized for non-cardiac complaints. Admission electrolyte values were not associated with QTc intervals. We conclude that the association of metabolic derangements and QTc abnormalities may not be as strong as is widely believed.
QTc（校正QT）间期延长和尖端扭转型室速（TDP）与低钙血症、低镁血症、低钾血症有关，可能还与碱中毒有关，可导致晕厥和心源性猝死。
本研究的目的是确定入院心电图（ECG）上QTc间期延长的患病率及其与同时测得的入院电解质值的相关性，并对入院诊断、合并症、其他ECG异常以及可能与QTc延长相关的药物进行校正。
连续纳入258例入住普通内科病房的患者，均有入院时的电解质检查结果和ECG记录。对于每份ECG，根据电子测量的QTc（Marquette ECG系统），将QTc以10毫秒的间隔进行分类，从QTc≥450毫秒到QTc≥500毫秒。查阅病历以获取预先确定的入院诊断、合并症以及与QTc延长相关的药物。采用单变量和多变量统计方法评估入院时电解质异常与QTc延长之间的相关性。
QTc间期异常的患病率因所采用的标准而异，从采用最宽松异常标准（QTc≥450毫秒）时的25.2%到采用最严格标准（QTc≥500毫秒）时的3.5%。在单变量分析中，QTc间期与任何一种电解质的入院值之间均无显著相关性。在多变量分析中，在对年龄、性别、ECG异常和其他协变量进行校正后，入院时的电解质值均与QTc延长无显著相关性。
采用传统标准，在因非心脏疾病主诉住院的普通内科患者入院时，电子测量的QTc间期延长相当常见。入院时的电解质值与QTc间期无关。我们得出结论，代谢紊乱与QTc异常之间的关联可能不像人们普遍认为的那么强。
