Pacemaker and defibrillator management is the subject of comprehensive reviews.1-8 The efficacy and cost-effectiveness of pacemakers are widely accepted, but the appropriate role for ICD insertion7 and biventricular pacing5 in older patients is still in evolution. Pacemaker and ICD technology are now applicable across the entire span of human age. Pacing for heart failure and ICD prophylaxis against lethal arrhythmias are recent frontiers. Electrophysiologists dominate these areas, reflecting decreased interest by thoracic surgeons and cardiology referral patterns. However, thoracic surgeons must maintain skills as implanters in order to serve as consultants or surgeons for complex or complicated cases. This chapter reviews practical information related to pacemaker and ICD insertion and management.
A permanent pacemaker or ICD consists of leads and a generator.2 The generator consists of a battery, a telemetry antenna, and integrated circuits. ICDs also include capacitors that store energy for high-output shocks. The power source is generally lithium iodide, but rechargeable and nuclear batteries have been used. The integrated circuits include programmable microprocessors, oscillators, amplifiers, and sensing circuits.2 The integrated circuits employ complementary metal-oxide semiconductor (CMOS) technology, which is subject to damage by ionizing radiation. Current pacemakers and ICDs monitor and report the status of internal components, external connections, programmed settings, recent activity, and notable arrhythmias. Unfortunately, each programmer controls only the devices of its manufacturer.4 Pacing systems compatible with magnetic resonance imaging (MRI)2 and wireless ICDs and pacemakers are now available, and wireless telemetry is available for remote follow-up.4
PACEMAKERS FOR CONTROL OF BRADYCARDIA
Early cardiac surgery was complicated by lethal iatrogenic heart block. Transthoracic pacing with Zoll cutaneous electrodes provided an early solution. Percutaneous endocardial pacing (1959) and “permanent” pacemakers using epicardial electrodes (1960) followed.9 Ensuing advances in bioengineering and technology have dramatically improved the quality of life for recipients. Persistent problems include lead durability, inflammatory responses to pacemaker materials, infection, device size, programmer compatibility, battery life, periodic battery replacement, and expense. Cardiac resynchronization therapy (CRT) for heart failure has made coronary sinus (CS) lead insertion an important technical skill.
Anatomy of Surgical Heart Block
The conduction system is vulnerable to injury during heart surgery. Complete heart block can result from suture placement during aortic, mitral, or tricuspid valve surgery, septal defect closure, or from myotomy for idiopathic hypertrophic subaortic stenosis. These lesions are mapped in Fig. 55-1. Infarction/abscess of the conduction system, inadequate myocardial protection, or trauma from retraction can also result in surgical heart block.
Anatomy of iatrogenic complete heart block. (A) His bundle and cardiac structures. Sites of injury are circled. (B) His bundle in the ventricular septum, below the noncoronary-right coronary aortic commissure. (C, D) During mitral surgery, the His bundle is on the ventricular septum anteromedial to the posterior commissure and right fibrous trigone. VSD = ventricular ...