B

Bandpass filter. An electronic component that allows some frequencies of a signal to be passed with negligible loss in strength (amplitude) while other frequencies are either blocked or passed with reduced strength. In pacing, the bandpass filter is intended to selectively separate cardiac depolarization signals from repolarization and extracardiac signals.

Base rate. The rate at which the pulse generator paces in the absence of intrinsic activity, expressed in pulses per minute (ppm). It is a programmable function in most modern pulse generators. Sometimes called basic rate, minimum rate or lower rate. It is also the escape rate in the absence of hysteresis.

Basic interval. The time period between two consecutive paced events without an intervening sensed event. It is expressed in milliseconds. Also known as automatic interval, demand interval or pacing interval.

Battery. The internal power source of implantable pulse generators. Most pulse generators today use single-cell, lithium-iodine batteries. The chemical interaction between the anode (positive pole) and cathode (negative pole) through the electrolyte causes current flow through an external circuit.

Beginning of life. The start of service of a pulse generator battery, usually occurring at implant. Abbreviated BOL. See also end of life and recommended mended replacement time.

Bi-directional telemetry. The ability of a device to transmit and receive data. In pacing, bi-directional telemetry allows the pulse generator to be both interrogated and programmed. See also telemetry.

Bifurcated bipolar lead. A bipolar pacing lead having two terminal pins and requiring two pacing lead receptacles, as opposed to a bipolar pacing lead with an in-line terminal pin requiring one pacing lead receptacle. The conductors in a bifurcated bipolar lead may be located next to each other (side-by-side lead) or one may be wrapped around the other (coaxial lead). See also coaxial lead.

Bin. An electronic capability in the memory of some advanced pulse generators which stores a certain type of data. Bins are usually associated with rate ranges. For example, one cardiac event is recorded by the pulse generator, classified by rate range and then stored in the bin for that rate range. Bin counts can later be interrogated. biphasic. A waveform morphology having both a positive and negative deflection.

Bipolar. Having two poles. In pacing, bipolar refers to a lead with two electrodes, both of which could be located within the heart, or a pulse generator that can accommodate such a lead. See also unipolar.

Bipolar lead. A pacing lead with two electrical poles that are external from the pulse generator. The negative pole or cathode is the electrode at the extreme distal tip of the pacing lead, while the positive pole or anode is an annular electrode several millimeters proximal to the cathode. The cathode is the electrode through which the stimulating pulse is delivered. Bipolar leads are characterized by relatively small spikes on the paced EGG. See also unipolar lead.

Bipolar pulse generator. A pulse generator that can accommodate a bipolar lead and operate in a bipolar configuration.

Blanking period. The interval of time during which the pacemaker cannot sense any events. An interval initiated by the delivery of an output pulse during which the sense amplifier of the pulse generator is temporarily disabled. In dual-chamber pulse generators, the blanking period is intended to prevent the inappropriate detection of signals from the opposite chamber (crosstalk). Blanking periods are not available in all pulse generators and the blanking period, stated in milliseconds, may be preset or programmable. For example, following an atrial output pulse, the ventricular sensing amplifier is blanked for 12 ins. The purpose of this blanking period is to prevent the ventricular sensing circuit from detecting the atrial output pulse and falsely inhibit the ventricular output.

BPEG. Abbreviation for British Pacing and Electrophysiology Group, a subdivision of the British Cardiac Society.

BPM. Abbreviation for beats per minute. The abbreviation bpm usually refers to an intrinsic heart rate, while pulses per minute (ppm) usually refers to the paced rate. See also ppm.

Bradycardia. Slow heart rate, usually defined as less than 60 beats per minute, or any rate that is too slow to be physiologically appropriate for the patient's age, condition and activity level.

Bundle branch block. An intraventricular conduction disorder in which the conduction of electrical impulses through the right or left bundle branch is partially or completely interrupted. Bundle branch block causes one of the ventricles to contract before the other. Abbreviated BBB.

Burst pacing. Several sequential, rapid stimuli delivered to the heart by an external or, in some cases, implantable pacemaker, in an effort to terminate a tachycardia. Burst pacing can sometimes lead to atrial fibrillation or, if delivered to the ventricle, ventricular fibrillation.