His-Bundle Pacing: Great in Theory, But Difficult in Practice

The introduction of cardiac pacing in clinical practice led to logical concerns about the possible impact of the stimulation site on cardiac function. Key studies in the seventies,1,2 however, showed that atrial, right ventricular, and left ventricular pacing produced no short-term differences in ventricular physiology either in patients with or without heart disease. These studies appeared to close the subject, and the problem of cardiac pacing was reduced to one of finding both identifying easiest access point which produced fewest complications. These studies, which undoubtedly paved the way for the tremendous developments which followed in cardiac pacing, also masked the harmful effects of long-term right ventricular pacing. But 2 decades later, the technique was shown to be associated with several deleterious physiological effects, including asymmetrical ventricular hypertrophy,3 ventricular dilatation,3 myofibrillar disarray,4 increase in myocardial concentrations of catecholamines,5 and alterations in myocardial perfusion.6 We have had to wait even longer to learn the clinical relevance of these findings.7-9 Recent, clinical evidence of the negative effects of right ventricular pacing is, however, conclusive. In the DAVID study, fo