Electrocardiographic abnormalities in patients with low or moderate risk pulmonary embolism: Prevalence and association with PO ₂ /FiO ₂ ratio

Introduction:Pulmonary embolism (PE) is a relatively common and potentially life-threatening condition. Previous studies have documented that approximately 70% of patients with mild to massive PE have an abnormal electrocardiogram (ECG). Aims and Objectives: To determine the prevalence of initial ECG findings in patients admitted for low and moderate risk PE and the possible association of those findings with the oxygenation index (PO 2 /FiO 2 ratio). Methods: Seventy two outpatients [age (mean ± SD): 60.4±18.5 years] admitted for low or moderate risk PE were retrospectively studied. The diagnosis was established on the basis of computed tomography pulmonary angiography in 73.6% (n=53), lung perfusion scintigraphy in 23.6% (n=17), or other methods in 2.8% (n=2) of total cases of PE. Results: Twenty three patients (31.9%) had normal ECG on admission. Sinus tachycardia was the most frequent ECG abnormality [37.5% (n=27)]. Other abnormalities observed were as follows: atrial fibrillation or flutter [8.3% (n=6)], right bundle branch block [12.5% (n=9)], “P pulmonale” [11.1% (n=8)], ST segment depression [1.4% (n=1)], T-wave inversion [18.1% (n=13)], T-wave flattening [12.5% (n=9)], and S1Q3T3 pattern [11.1% (n=8)]. The combined presence of supraventricular tachycardias (SVTs) and QRS abnormalities was associated with a significantly lower PO 2 /FiO 2 ratio, compared to patients with either SVTs, QRS abnormalities or normal ECG [one-way ANOVA: F(3,68)=3.77, p=0.014]. Conclusions:Approximately 2/3 of patients with PE have ECG abnormalities on admission. The combined presence of SVTs and QRS abnormalities is associated with lower PO 2 /FiO 2 ratio.