Cardiac Pacemaker Essay
CHAPTER 1
Basic principles of pacing
Malcolm Kirk
The aim of this chapter is to give sufficient background and information about cardiac pacemakers to allow interpretation of electrocardiograms (ECGs) and telemetry strips of normal pacemaker behavior. For more in-depth information, such as would be necessary for programming pacemakers, a standard pacing text should be consulted. Several of these are listed in the bibliography.
Most italicized terms are defined in the glossary at the end of the chapter.
Anatomy
The pertinent anatomy for cardiac pacing includes the sinoatrial (SA) node, the atrioventricular (AV) node, and the His-Purkinje system (Figure 1.1).
The SA node is located at the superior aspect of the crista terminalis (not
pictured), …show more content…
The pacemaker cannot sense activity in a chamber until the electrical activity actually reaches the pacemaker lead. Figure 1.8 illustrates that sensing in the ventricle occurs after the onset of the QRS complex.
Inhibition of output
A pacemaker can be programmed to inhibit pacing if it senses intrinsic activity, or it can be programmed to ignore intrinsic activity and deliver a pacing stimulus anyway. If a pacemaker is set so that it can be inhibited by intrinsic beats, then the pacemaker will not deliver a stimulus if it senses an intrinsic beat at the proper time. For example, if a pacemaker is set to pace in this way at 60 bpm, it will deliver a pacing stimulus only if an intrinsic beat does not occur within 1 second of the last sensed or paced beat.
Triggered pacing
Pacemakers can be programmed to deliver a pacing stimulus whenever intrinsic activity is sensed. This type of pacing is most often used in dual chamber pacemakers. Dual chamber pacemakers can be programmed to sense activity in one chamber (usually the atrium) and deliver a pacing stimulus …show more content…
(a) and (b) both show atrial sensing, and ventricular
pacing, in a tracking mode. The pacemaker settings are the same in both panels.
The difference is that in (b) the intrinsic atrial rate is faster.
patient’s own atrial rate (Figure 1.9). One would want to limit, of course, the maximum rate at which the pacemaker will track the atrial rhythm with ventricular pacing. This is discussed more extensively in the section on “Basic pacemaker programming – timing cycles.”
Pacing modes
A standard pacemaker code has been developed jointly by the North American
Society for Pacing and Electrophysiology, and the British Pacing and Electrophysiology Group (the NASPE/BPEG Generic Code, known as the NBG Code).
The pacing function provided by a pacemaker (or defibrillator) is usually given by a series of three or four letters. (There is a fifth position in the code, which is not commonly used.) Each position denotes a different aspect of pacemaker function. The identity of the letter in that position specifies the function. A given combination of three or four letters is called a mode. A more in-depth discussion of these modes, and in the clinical scenarios for which each is used, appears in Chapter
Basic principles of pacing
Malcolm Kirk
The aim of this chapter is to give sufficient background and information about cardiac pacemakers to allow interpretation of electrocardiograms (ECGs) and telemetry strips of normal pacemaker behavior. For more in-depth information, such as would be necessary for programming pacemakers, a standard pacing text should be consulted. Several of these are listed in the bibliography.
Most italicized terms are defined in the glossary at the end of the chapter.
Anatomy
The pertinent anatomy for cardiac pacing includes the sinoatrial (SA) node, the atrioventricular (AV) node, and the His-Purkinje system (Figure 1.1).
The SA node is located at the superior aspect of the crista terminalis (not
pictured), …show more content…
The pacemaker cannot sense activity in a chamber until the electrical activity actually reaches the pacemaker lead. Figure 1.8 illustrates that sensing in the ventricle occurs after the onset of the QRS complex.
Inhibition of output
A pacemaker can be programmed to inhibit pacing if it senses intrinsic activity, or it can be programmed to ignore intrinsic activity and deliver a pacing stimulus anyway. If a pacemaker is set so that it can be inhibited by intrinsic beats, then the pacemaker will not deliver a stimulus if it senses an intrinsic beat at the proper time. For example, if a pacemaker is set to pace in this way at 60 bpm, it will deliver a pacing stimulus only if an intrinsic beat does not occur within 1 second of the last sensed or paced beat.
Triggered pacing
Pacemakers can be programmed to deliver a pacing stimulus whenever intrinsic activity is sensed. This type of pacing is most often used in dual chamber pacemakers. Dual chamber pacemakers can be programmed to sense activity in one chamber (usually the atrium) and deliver a pacing stimulus …show more content…
(a) and (b) both show atrial sensing, and ventricular
pacing, in a tracking mode. The pacemaker settings are the same in both panels.
The difference is that in (b) the intrinsic atrial rate is faster.
patient’s own atrial rate (Figure 1.9). One would want to limit, of course, the maximum rate at which the pacemaker will track the atrial rhythm with ventricular pacing. This is discussed more extensively in the section on “Basic pacemaker programming – timing cycles.”
Pacing modes
A standard pacemaker code has been developed jointly by the North American
Society for Pacing and Electrophysiology, and the British Pacing and Electrophysiology Group (the NASPE/BPEG Generic Code, known as the NBG Code).
The pacing function provided by a pacemaker (or defibrillator) is usually given by a series of three or four letters. (There is a fifth position in the code, which is not commonly used.) Each position denotes a different aspect of pacemaker function. The identity of the letter in that position specifies the function. A given combination of three or four letters is called a mode. A more in-depth discussion of these modes, and in the clinical scenarios for which each is used, appears in Chapter