Delayed intrinsicoid deflection: Electrocardiographic harbinger of heart disease

Delayed intrinsicoid deflection (DID) is an emerging electrocardiogram (ECG) marker of major clinical significance that is increasingly getting attention. Intrinsicoid deflection measures ventricular depolarization in the initial portion of the QRS complex, and DID is defined as an R wave peak time of ≥50 ms in leads V(5) and V(6). Prior studies have identified an independent association between DID and cardiovascular conditions such as left ventricular hypertrophy, heart failure, and sudden cardiac death. The exact mechanism that results in DID remains unknown. Animal models indicate that DID may result from abnormal calcium and potassium conductance as well as extracellular matrix remodeling. DID remains an ECG marker of interest given its potential predictive value of underlying cardiovascular pathology and adverse events. This review provides an update on the proposed mechanisms and associations, as well as the clinical and research implications of DID.