Pacemaker and defibrillator management is the subject of comprehensive reviews.1 In the author's experience with 2760 procedures, 23% of pacemaker recipients and 5% of implantable cardioverter defibrillator (ICD) recipients were octogenarians. The incidence of pacemaker insertion in patients older than 75 was 2.6% in a recent survey. The efficacy and cost-effectiveness of pacemakers are widely accepted, but the appropriate role for ICD insertion and biventricular pacing in older patients is still in evolution. Pacemaker and ICD technology is now applicable across the entire span of human age, with pacing for heart failure and ICD prophylaxis against lethal arrhythmias recent frontiers. Electrophysiologists now dominate these areas, reflecting decreased interest by thoracic surgeons and cardiology referrals. However, thoracic surgeons must maintain skills as implanters and consultants 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 leads2 and a generator. The generator contains 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.3 The integrated circuits employ CMOS (complementary metal-oxide semiconductor) technology, which is subject to damage by ionizing radiation.4 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.
Early cardiac surgery was complicated by lethal iatrogenic heart block. Transthoracic pacing with Zoll cutaneous electrodes provided a solution.5 Percutaneous endocardial pacing (1959)6 and "permanent" pacemakers using epicardial electrodes (1960)7 followed. 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, and expense. Development of resynchronization therapy has made coronary sinus 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 or during closure of septal defects or during myotomy for idiopathic hypertrophic subaortic stenosis. These lesions are illustrated in Fig. 59-1. Infarction of the conduction system or inadequate myocardial protection 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) The 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 ...