Accessory pathways can be classified by their location, type of conduction (decremental or nondecremental), and whether they are capable of conducting anterogradely, retrogradely, or in both directions. Of note, accessory pathways of other types (such as atriofascicular, nodo-fascicular, nodo-ventricular, and fasciculoventricular pathways) are uncommon and are discussed only briefly in this document (Section 7). Manifest accessory pathways A pathway that conducts anterogradely to cause ventricular pre-excitation pattern on the ECG. (Continued) Page et al 2015 ACC/AHA/HRS SVT Guideline e513 True syncope is infrequent with SVT, but complaints of light-headedness are common. In patients with WPW syn- drome, syncope should be taken seriously but is not neces- sarily associated with increased risk of SCD.64 The rate of AVRT is faster when AVRT is induced during exercise,65 yet the rate alone does not explain symptoms of near- syncope. Elderly patients with AVNRT are more prone to syncope or near-syncope than are younger patients, but the tachycardia rate is generally slower in the elderly.66,67 The drop in blood pressure (BP) during SVT is greatest in the first 10 to 30 seconds and somewhat normalizes within 30 to 60 seconds, despite minimal changes in rate.68,69 Shorter ventriculoatrial intervals are associated with a greater mean decrease in BP.69 Studies have demonstrated a relationship between hemodynamic changes and the relative timing of atrial and ventricular activation. In a study of patients with AVNRT with short versus long ventriculoatrial intervals, there was no significant difference in tachycardia cycle ; however, the induction of typical AVNRT caused a marked initial fall in systemic BP, followed by only partial recovery that resulted in stable hypotension and a reduction in cardiac output due to a decrease in stroke volume. 