N

NASPE. Abbreviation for the North American Society of Pacing and Electrophysiology.

NBG Code. A three- to five-letter code designating pacing mode devised and periodically updated by a committee from NASPE and BPEG. The NBG Code is universally used to describe the basic functions of the pacemaker. Each position in the code has a meaning (the first designates chamber paced, the second chamber sensed, the third the response to sensing, the fourth programmable functions such as rate modulation and the fifth antitachyarrhythmia functions) as does each letter (A = atrium, V = ventricle, D = dual, O = neither, I = inhibited, T = tracking, R = rate modulation, and so on). For example, a VVIR pacemaker paces in the ventricle, senses in the ventricle, has an inhibited response to sensing and offers rate modulation. See also ICHD code.

NIEPS. Noninvasive electrophysiologic programmed stimulation, a feature of certain pacemakers allowing the implanted pacemaker to be used for repeated electrophysiologic testing in the patient. Sometimes called NIPS.

Noise. A general, informal term for any type of interference, most commonly electrical interference or myopotentials.

Noise response. The pacemaker's predetermined pacing behavior (rate, mode or other changes) in the presence of interference.

Noise sampling period. The second or latter portion of the refractory period in some pacemakers during which incoming signals are interpreted as interference and are monitored. In many Pacesetter products, the refractory period consists of an initial or absolute refractory period (during which all signals, regardless of origin, are ignored) followed by the noise-sampling period or relative refractory period (during which signals at certain frequency ranges are monitored, causing the refractory period to be reset with an additional absolute or relative segment). Continued interference eventuates in asynchronous pacing. Also known as relative refractory period.

Nominal. (1) Stated values, for instance, nominal dimensions. (2) The settings of a pulse generator's programmable parameters as shipped. Nominal values may also be used to describe those programmable pacing parameter values which will safely pace the majority of patients. Also known as shipped settings.

Noncommitted. In theory, a type of dual-chamber pacemaker response in which the ventricular channel can sense and be inhibited by a ventricular response even after the atrial channel has just delivered an output pulse (that is, even if the sensed QRS complex falls during the AV delay). In actuality, there are no truly noncommitted dual chamber pacemakers at this time. See also committed. non-invasive. Describes medical instruments or procedures that do not require cutting the skin.