Cardiac rhythm management devices (CRMDs) are becoming increasingly common as our population ages and indications for their use broaden.1 These devices are becoming increasingly complex. Single-chamber devices with only a pacing function have given way to dual-chamber devices with the ability to sense and programmable features (e.g., automatic mode switching or rate responsiveness). Implantable cardioverter-defibrillators (ICD) have been developed as primary and secondary prevention for sudden cardiac death and have a backup pacemaker function. Biventricular pacemakers are known as cardiac resynchronization therapy (CRT). They were developed to coordinate the action of the right and left ventricles for patients with reduced systolic function and delayed conduction defined by a wide QRS. Most CRT devices have an associated defibrillator (CRT-D) since indications for CRT are associated with a high risk for ventricular tachycardia (VT) and ventricular fibrillation (VF).
Have a very low threshold for formal device interrogation and Cardiologist consultation when a malfunction is suspected given the complexity of the current generation of pacemakers. The Emergency Physician must be careful not to prematurely attribute a patient’s presentation to a pacemaker malfunction. Consider life-threatening and other conditions while awaiting pacemaker interrogation. Any critical illness causing severe metabolic derangements (e.g., acidosis, hypoxemia, or hyperkalemia) can interfere with device function by altering the tissue interface with the myocardium.
Pacemakers have become more complex. They are more reliable with better hermetic sealing, better batteries and circuitry, the use of bipolar instead of unipolar leads, and special programming to prevent rhythm-related complications. Pseudo-malfunctions occur when a device is functioning as programmed but there are unexpected or unusual electrocardiogram (ECG) findings. The pseudo-malfunction is more common than a true malfunction.
It may not be obvious when a patient presents to the Emergency Department if their symptoms are due to a pacemaker malfunction. The patient may not even provide a history of having pacemaker. The goal of this chapter is to prepare the Emergency Physician to manage patients presenting with symptoms that may be related to these devices and to understand how the presence of a pacemaker may affect patient care. The common term pacemaker spike is used instead of pacemaker artifact throughout this chapter.
INDICATIONS FOR PACEMAKER PLACEMENT
Consensus guidelines for pacemaker placement have been established by the American College of Cardiology (ACC), the American Heart Association (AHA), and the Heart Rhythm Society (HRS).2 Pacemakers are placed most often for symptomatic bradycardia from sinus node dysfunction or atrioventricular block (Figures 45-1 and 45-2). CRT pacemakers are placed for advanced heart failure with conduction delays as defined by a wide QRS interval. CRT improves cardiac function, quality of life, and survival.3 Placement of ICDs is for primary and secondary prevention of VT or VF. ICD patients often overlap with patients needing CRT, with most CRT devices having a defibrillator, known as CRT-D.4