CHAPTER 84 Cardiac Devices for the Treatment of Bradyarrhythmias and Tachyarrhythmias

Preoperative Evaluation before Implantation of Cardiac Devices

Postimplantation Care of Transvenous Cardiac Devices

Complications of Implantable Cardiac Devices

Management of Cardiac Devices during and after Surgery

HISTORICAL PERSPECTIVE AND OVERVIEW

Paul Zoll developed the first transcutaneous electronic pacemaker in 1952 for the treatment of life-threatening bradycardia.¹ The first internal pacemaker was implanted in 1958 for the treatment of complete heart block² and in the management of Stokes-Adams seizures.³ Early pacemaker models were simple, fixed-rate devices. Thoracic surgeons performed the majority of early implants by placing epimyocardial leads directly on the exposed heart; these leads were connected to an abdominally implanted pulse generator. Modern pacemakers have sophisticated microprocessors that apply diagnostic and therapeutic algorithms, which have dramatically increased their versatility.

The development of the implantable cardioverter-defibrillator (ICD) was pioneered by Michel Mirowski.⁴^–⁶ The initial purpose of the ICD was to provide immediate, automatic defibrillation to ambulatory patients who were victims of a lethal ventricular arrhythmia. Mirowski performed the first human ICD implantation in 1980.⁵ First-generation ICDs were composed of large generators (>200 cm³ volume) implanted in an abdominal pocket with epicardial defibrillator patches; these early ICDs were capable only of high-energy shocks. Current ICDs are small (<40 cm³ volume) but contain all the advanced pacing functions of modern pacemakers as well as complex tachycardia treatment options (Figs. 84-1 and 84-2). Despite their diminutive size, newer ICDs have become progressively superior in their sensing, detection, and treatment of arrhythmias. Since the late 1990s, ICDs have emerged as the single most effective lifesaving intervention in modern medicine.⁷^–¹¹

Figure 84–1 Implantable cardioverter-defibrillators in 1980.

(Courtesy of Medtronic Inc.)

Figure 84–2 Implantable cardioverter-defibrillators today. VT/VF, ventricular tachycardia/ventricular flutter.

(Courtesy of Medtronic Inc.)

With increased sophistication and miniaturization of pulse generators and the development of the much simpler and safer transvenous approach for implantation of cardiac devices, indications for cardiac pacing as well as for ICDs have dramatically expanded.^12,¹³ It is estimated that nearly 800,000 cardiac devices were implanted in North America in 2007 and more than 1,500,000 worldwide.¹⁴

The remainder of this chapter focuses on the description, implantation techniques, indications, and complications of current implantable cardiac pacemakers and defibrillators.

INDICATIONS FOR IMPLANTATION OF CARDIAC DEVICES

The American College of Cardiology/American Heart Association/Heart Rhythm Society guidelines for device-based therapy of cardiac rhythm abnormalities were updated in May 2008.^13,¹⁵

Temporary Pacemakers

Indications

Placement of a temporary pacemaker is indicated whenever hemodynamic compromise is present because of a bradyarrhythmia. Temporary pacemakers should also be placed prophylactically if high risk for development of hemodynamically important bradycardia is present. Specific guidelines for placement of temporary pacemakers in the setting of acute myocardial infarction exist.¹⁶ Temporary transvenous pacing is indicated in symptomatic sinus bradycardia, sinus pauses of more than 3 seconds, or sinus bradycardia with a heart rate below 40 beats per minute associated with hypotension or hemodynamic compromise, if unresponsive to maximum doses (2 mg) of intravenous atropine. Other class I indications for temporary transvenous pacing in acute myocardial infarction include ventricular asystole, alternating left and right bundle branch block, and new bundle branch block or fascicular block and right bundle branch block in the setting of Möbitz II second-degree atrioventricular (AV) block.¹⁶

Venous Access

Table 84-1 summarizes the different sites that can be used for insertion of a temporary pacemaker.¹⁷ Careful consideration of the site to be used is important as it relates to the particular patient and advantages and disadvantages of each site. For instance, the internal jugular and subclavian veins may be chosen when need for stability and longer pacing requirement is anticipated. If a permanent pacemaker will be required in the future, the temporary pacemaker should be placed through a vein remote from the preferred site for permanent pacemaker implantation. Use of the antecubital veins minimizes bleeding in the coagulopathic patient. However, the risk of cardiac perforation or lead dislodgement is higher if the arm is not kept fully immobilized.

Table 84–1 Sites for Placement of a Temporary Pacemaker

Site	Advantages	Disadvantages
Femoral vein	Easy access	Leg must remain immobilized
		High infection risk
		Fluoroscopy required for proper placement
		Patient must lie flat
Internal jugular vein	Good site for pacer placement (right better than left)	Risk of pneumothorax, inadvertent carotid artery puncture
Internal jugular vein	Good site for pacer placement (right better than left)	Patient must lie flat for access; Trendelenburg’s position preferred to avoid air embolism
Subclavian vein	Good site for pacer placement (left better than right)	Risk of pneumothorax, hemothorax with inadvertent subclavian artery puncture
Subclavian vein	Good site for pacer placement (left better than right)	Patient must lie flat for access; Trendelenburg’s position preferred to avoid air embolism
Antecubital vein (basilic, median basilic, or cephalic)	Access is low risk	Risk of dislodgement; arm must remain immobilized
	Good site for pacer placement (left better than right)	Basilic or median basilic preferred (cephalic has tortuous course to central veins)
	Good site for pacer placement (left better than right)	Fluoroscopy required for pacer placement

From Baim DS, Grossman W, editors. Grossman’s cardiac catheterization, angiography, and intervention. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2000.