When QRS duration is prolonged (equal or greater than 100 millisec) following a normally conducted P wave or with atrial fibrillation but the morphology is not that of LBBB, RBBB, or WPW then the diagnosis of NSIVCD is made. If Q waves are present this can be called peri-infarction block. Acute prolongation of the QRS duration can be due to drugs such as Quinidine. This can be a normal variant and is not always associated with cardiac pathology. Clinical correlation (history and physical exam) is needed to identify associated cardiac abnormalities.

Clinical correlation (history and physical exam) is needed to identify associated cardiac problems. If there is a history of CHF or an abnormal cardiac exam then an echocardiogram is indicated. If Q waves are present and there is a history of a myocardial infarction then an echocardiogram is indicated to determine if an ACE inhibitor should be given to lessen the possibility of CHF exacerbation and other complications. If a drug like quinidine is being taken and can be related temporally to the IVCD then increasing dosage is not indicated.