The main concept tested is how a pacemaker or ICD is evaluated for actual performance and safety after implantation, focusing on how well the device and its leads will function in real life. The best endpoints are about electrical performance and therapy behavior: lead sensing and capture thresholds determine whether the device can reliably detect intrinsic heart activity and deliver pacing effectively; intact insulation checks ensure the leads won’t leak current or fracture, which could cause inappropriate sensing or failure to pace. The absence of unintended shocks is crucial for ICDs, confirming that the device does not misinterpret signals and deliver therapy when it isn’t needed. And appropriate therapy programming ensures the device’s detection criteria, therapy sequences, and pacing parameters are aligned with the patient’s rhythm and clinical needs, so therapies are delivered correctly and safely. Battery life estimates and cosmetic or wound-related aspects relate to other concerns, not the ongoing functional performance of the device.

Electroanatomic mapping platforms combine 3D anatomical reconstruction with electrical data to guide catheter navigation and ablation, providing activation and voltage maps in real time. EnSite and CARTO are the two most well-known systems that illustrate how these platforms function, each offering catheter localization within a 3D chamber, integration of electrical signals, and non-fluoroscopic guidance to map arrhythmias. The other options don’t fit because they’re imaging modalities or targets rather than mapping platforms (fluoro and MRI are imaging techniques), mapping targets or lines within a procedure (PV mapping and CTI line), or implanted devices (pacemaker and defibrillator).

Velocity is the distance traveled per unit time. In nerve conduction studies between two stimulation sites, you’re measuring how far apart those sites are and how long the impulse takes to travel from one site to the other. The time taken to traverse that segment is the difference in latencies, and the distance traveled is the difference in the stimulation-site distances. So the velocity is the distance difference divided by the latency difference: (D2 − D1) / (T2 − T1). This mirrors the basic speed formula and uses the exact segment the impulse travels. Using sums or reversing the ratio would not reflect the actual propagation along the segment and can give incorrect results (for example, adding distances or times isn’t measuring the travel over a single segment, and swapping numerator and denominator yields the inverse of velocity).

Inplexus lesions, because the injury involves a proximal, branching network feeding many nerves, the EMG pattern is not confined to a single nerve territory. Needle EMG tends to show a patchwork of denervation and reinnervation across multiple muscles supplied by different branches of the plexus. You’ll often see active denervation (fibrillation potentials or positive sharp waves) in several muscles, alongside motor units that are large or polyphasic due to collateral reinnervation, leading to a very complex overall picture. This complexity reflects the involvement of multiple nerve roots and trunks and the resulting mix of affected and partially spared fibers, rather than a straightforward, uniform deficit seen with a single nerve lesion. The other descriptions don’t fit: a simple pattern would suggest involvement of only one nerve; no denervation would be unusual with plexus injury; and focusing on decreased conduction velocity in distal nerves points to demyelination in a different setting, not the axonal, multifocal pattern typical of plexus injury.