It is frequently a normal variant in asymptomatic older children. Other causes include left-sided heart disease, single ventricles, and cardiomyopathies. Cause for concern is that it can be associated with an AV canal defect or inlet VSD. This refers to the mean QRS vector being less than 0 degrees. Holter monitors interpreted by non-pediatric cardiologists may label this as recurrent SVT. Frequently these situations result in sinus tachycardia because of the fear reaction. Unfortunately, when it is very pronounced, it can be a cause for concern in the patient or parents who interpret the irregular rhythm as abnormal or possibly (in medical families) as a sign of atrial fibrillation. This is invariably normal and physiologic. If a murmur is present or there are potential cardiac symptoms or the QRS duration is >120msec cardiology evaluation is warranted. Sometimes medications can cause conduction delay, this is felt to be benign. But since there is a small proportion of patients who do have an abnormality, a decision on whether or not the patient should be evaluated further depends on the reasons for the electrocardiogram.Ĭause for concern: This may be a manifestation of RV enlargement in situations such as an atrial septal defect or anomalous pulmonary venous return. The difficulty for cardiologists reading an electrocardiogram with conduction delay without seeing the patient is that it is tempting to label it as normal since the vast majority of the patients with this, in fact, have a normal heart. It is mostly a variant of normal, especially in athletes. This is also known as conduction delay, IVCD, or incomplete right bundle branch block (iRBBB). This is a brief review of the terminology and implications of ECG interpretations to assist providers in their decision making. In 1,224 white men with normal QRS morphologies and frontal axis (-25 to 100), the 98% upper and lower bounds of QRSD with the 12SL algorithm, like that seen in BSMs, was 80-116 ms, peak 96 ms.The physician receiving ECG results may question what these mean in some instances, what is significant and finally, what to do with the results. Sixty-three (5%) had a QRSD greater than or equal to 112 and less than or equal to 116 ms-36 of this group had normal morphology 1 had typical RBBB and 26 had R' V1, V2 (considered a normal variant as it occurred in 360 of 1,164 remaining with QRSD less than or equal to 108). Twenty-seven of 1,254 (2.1%) had QRSD greater than or equal to 120 ms-14 of these had normal morphology 2 had RBB 3 had atypical RBB 5 had R' in V1, V2 2 had WPW and 1 had Superior Fascicular Block. The frontal QRS axis was between -30 and -65 in 22 of 1,254 (1.8%). All had a negative history (including drugs known to affect the cardiovascular or pulmonary systems), a negative family history (in immediate family members before age 55), no physical findings suggestive of heart disease, a normal blood chemistry profile, pulmonary function tests, and symptom limited bicycle exercise test. The QRS duration (QRSD) on a digital 12 simultaneous lead ECG was measured by a commercially available recording cart (Marquette MACII 12SL) in 1,254 white male safety workers (ages 19-65, mean 34).
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