The specificity of negative P wave in lead I and aVL that indentifed a left atrial focus was 100% and 95% respectively, but the sensitivity was only 30% and 50% respectively.

• I导联和aVL导联P波负向预测左房房速的特异性分别达到了 10 0%25和 95%25 ,但敏感性分别仅有 30%25和 5 0%25 ;