Chapter 42: Transthoracic Cardiac Pacing

INTRODUCTION

Transthoracic cardiac pacing is a historic technique of pacing the heart with an electrode introduced percutaneously into the ventricular cavity using a needle trocar introducer. There is sparse literature on transthoracic cardiac pacing, its benefits, and complications. Transthoracic pacing was a faster alternative to transvenous pacing in the patient with an acutely unstable dysrhythmia. The advent of effective and efficient transcutaneous pacing has made the indications for transthoracic pacing extremely rare. The technique of transthoracic pacing is included in this text because it is occasionally performed in situations where transcutaneous pacing is unavailable or ineffective.^1-3

The history of electrical stimulation of the heart dates to 1862 when Walsh discussed the possibility of causing the heart to contract through stimulation of the sympathetic nervous trunk by an induced current.⁴ It was largely understood by 1910 that the neuromuscular mechanism of the heart was electrically dependent. A needle electrode was used in 1928 to carry stimulating current directly to heart muscle.⁵ The first successful clinical application of external cardiac pacing was in 1952 with the resuscitation of two patients in asystole following bradycardia from a high-degree atrioventricular (AV) block.⁶ It was concluded that external cardiac pacing was a safe and effective means of resuscitating ventricular standstill. The devices caused significant chest pain, skeletal muscle spasm, and superficial skin burns and disrupted electrocardiogram (ECG) monitoring.⁶ The quest for alternative pacing modalities continued with the refinement of the transesophageal technique in 1957.⁷ The emergency use of a lumbar puncture needle introduced 5 mm into the myocardium, through which a conducting wire was introduced, was used to produce transthoracic cardiac pacing.⁸ A transvenous wire catheter was passed in 1959 that successfully applied an electrical current to the endocardial surface of the right atrium.⁹ Transvenous pacing subsequently became the most widely accepted method of emergency cardiac pacing until the reemergence of a modified external pacing system in 1981.¹⁰

ANATOMY AND PATHOPHYSIOLOGY

The heart is the only muscle of the body that generates its own electrical impulses. The initial cardiac impulse starts in the right atrium at the sinoatrial (SA) node. The sympathetic and parasympathetic nervous systems control the rate of impulse generation at the SA node. The electrical stimulus is conducted along the internal conduction pathways of the heart to the muscular atrial and ventricular walls. A delicate balance between electrolyte flux to create action potentials, myocardial integrity to allow impulses to become contractions, and an intact conduction system must be maintained. The blood supply to the conduction system of the heart originates from the right coronary artery. Arrhythmias and conduction delays are often the result of inadequate blood flow to the heart due to ventricular infarction and coronary artery occlusion.

INDICATIONS

Transthoracic cardiac pacing is a simple procedure and can be accomplished rapidly. The indications for transthoracic pacing ...