Right ventricular dysfunction: Lessons from congenital and acquired heart disease

Professor of Pediatrics, University of Toronto Faculty of Medicine, Head, Division of Cardiology,
Hospital for Sick Children, Toronto, Ontario, Canada
Andrew N. Redington

The results of an electronic search of the literature of the last three decades underscore the lack of attention paid to right ventricular form and function, publication's concerning the left ventricle outnumbering those of the right ventricle by approximately 10 to 1. Nonetheless, the last decade has seen increased recognition of the importance of right ventricular (RV) function in the circulation. The negative impact of coexisting RV dysfunction in dilated and ischemic cardiomyopathy is well established, for example, but it is in congenital heart disease where right ventricular dysfunction is now accepted as being pivotal to the natural and unnatural history of so many of the disease complexes. Now that operative mortality of the early repair has fallen to very low levels, attention has turned to improving longer-term outcomes and preservation of function, not least that of the right ventricle. However, because of the unique haemodynamics associated with RV dysfunction, its impact may only become apparent clinically after decades of follow-up. It is in this regard that the study of adolescent and adult survivors can be so instructive. Indeed, many of the concepts now being applied to the early treatment of congenital heart diseases, have evolved from the study of the long-term survivors in adult congenital heart clinics. Our changing management of tetralogy of Fallot is a perfect example. Inappropriate concerns regarding the importance of residual RV outflow tract obstruction, and ignorance of the adverse effects of pulmonary incompetence, resulted in the frequent use of generous transannular patches in the 1960's, 70's and 80's. Early mortality fell progressively during these first three decades of tetralogy surgery, but as we learned more about the protean late complications associated with pulmonary incompetence in the 1990's, contemporary surgical strategies have been redirected towards preserving pulmonary valve function.
While ignorance of the potential impact of dysfunction may explain some of the lack of attention paid to the right ventricle, there is another pragmatic, but no less important, reason for the relative scarcity of mechanistic research. There can be no doubt that the adequate assessment of RV performance is more difficult than that of its left ventricular counterpart. While the prolate ellipsoid of the left ventricle lends itself to geometric assumptions and mathematical interpretation, the shape, geometry, and anatomical location of the right ventricle all conspire against precise assessment. Add to this the effects of coexisting congenital abnormalities, beat to beat changes occurring with respiration, the profound changes that may occur with abnormalities of the pulmonary vascular bed, and right/left heart interactions, and it is easy to see why understanding of RV function has lagged behind that of the left. Nonetheless, each of these issues is of fundamental importance to the physiology of the circulation as a whole, and a variety of methods are now available for the assessment of RV performance.
In this presentation I will attempt to describe some of the ways in which our understanding of right ventricular physiology have evolved over the past two decades.