aVR导联临床应用的新视点

aVR导联是一个经常被忽略的导联,但是,近几年的研究显示aVR导联在诸多方面都发挥着重要的作用。aVR导联经典的临床应用包括窦性心律的确认、电轴的确定、右位心和左右手反联及心室肥厚的诊断。其临床应用的新发现包括:急性冠脉综合征时,aVR导联ST段抬高提示左主干、左前降支近端或三支病变;在ST段抬高型心肌梗死中aVR导联ST段抬高或下移是住院患者死亡率的独立预测因子,可用于危险分层;分析心律失常时,aVR导联可用于鉴别宽QRS型、窄QRS型心动过速;体表心电图的aVR导联结合V1、V2导联可以估算右房房颤周长,并且aVR导联P波振幅是心脏手术术后房颤发生的强有力的预测因子;Brugada综合征时出现"aVR征"有助于危险分层;右室负荷过重时,aVR导联ST段抬高是急性肺栓塞的死亡预测因子(单变量回归分析)和并发症的预测因子;aVR导联R波延迟是慢性右室压力负荷过重的独立预测因子且多见于肺动脉狭窄患者;特发性肺动脉高压的患者中,aVR导联R波>4mm,结合V1导联R波>6mm、R/SV1>1,R/SV5与R/SV1比值<0.04,Ⅱ导联P波>2.5mm可以诊断右室肥厚;当疑似预激综合征时,利用体表心电图同时出现PR间期≤120ms和PR离散度≥20ms、aVR导联缺少初始正向波(间隔R波)和V1导联水平面QRS移行提前这3步可识别心室预激,且具有较高的特异性和敏感性;连续监测aVR导联R波和R/S比例有助于预测三环类抗抑郁药物中毒时意识的恢复;急性心包炎时,aVR导联ST段压低、PR段抬高形成了急性心包炎的特征性表现,即"关节征",并且可能是急性心包炎最早甚至是唯一的心电图改变,具有早期诊断价值。

New viewpoints of lead aVR for clinical applications

Among electrocardiographic leads,lead aVR usually receives less attention in clinical evaluation of electrocardiogram(ECG). However recent researches reveal important roles lead aVR plays in various ways. The classical clinical applications of lead aVR include the identifications of sinus rhythm and axis and the diagnosis of dextrocardia,exchanges of the upper limb leads and ventricular hypertrophy. There were several other clinical applications discovered recently. Firstly,when acute coronary syndrome attacks,ST segment elevation in lead aVR could indicates the stenosis of left main coronary artery,proximal left anterior descending or three-vesseled coronary artery disease. When ST-segment-elevation typed myocardial infarction occurs,elevation or depression of ST segment could serve as independent predictor of mortality of inpatients and be utilized in the risk stratification. Secondly,lead aVR could be applied in differentiating wide or narrow QRS tachyarrhythmias. Combined with lead V1and V2,lead aVR of surface ECG can be utilized in the estimation of the cycle length of right atrial fibrillation. It implies that the amplitude of P wave in lead aVR was a powerful predictor of postoperative atrial fibrillation. And the morphology of R wave in lead aVR could be helpful in risk-stratifying patients with Brugada syndrome. Thirdly,when right ventricle is overloaded,ST segment elevation in lead aVR can provide some valuable information for predicting the death rate(by univariate regression analysis) and complication of acute pulmonary embolism. The R-wave delay in lead aVR is proved to be an independent predictor of overloaded right ventricle and more prevalent in patients with pulmonary stenosis. Among patients with idiopathic pulmonary arterial hypertension,R wave in lead aVR>4 mm in combination with R in V1>6 mm,R / S in V1>1,R / S in V5 to R / S in V1< 0.04 and P in Ⅱ > 2.5 mm could confirm the diagnosis of right ventricular hypertrophy. Fourthly,when Wolff-Parkinson-White syndrome probably occurs,a three stepwise criteria which is composed of the presence of both PR interval≤120 ms and PR dispersion≥20 ms,the absence of initial forward wave(septal R wave) in lead aVR and horizontal QRS transition in lead V1or before could be utilized in identifying ventricular preexcitation and the criteria proves to be very sensitive and specific. Furthermore,a serial monitoring of R wave and R / S ratio in lead aVR might be informative in predicting the recovery of consciousness from toxicity due to tricyclic antidepressants overdose. In addition,when acute pericarditis attacks,ST segment depression and PR segment elevation in lead aVR become characteristic representations of the disease,that is,knuckle sign,which may help in the diagnosis of acute pericarditis for it’s possibly the earliest and the only change of ECG.