Patients with left ventricular dysfunction have a poor long-term prognosis. The ejection fraction is a powerful predictor of survival. Nevertheless, it has become clear in the last 10 years that parameters other than left ventricular pump function also have a large prognostic role, especially in severe cardiac disease with a low ejection fraction. Of the more intriguing new variables, right ventricular (RV) function appears particularly destined for widespread clinical use.
The first evidence that the RV ejection fraction might predict short-term and long-term outcome came from patients with advanced heart failure, notably transplant candidates, in whom RV functional studies are used to prioritize surgery. RV function was evaluated in addition to conventional clinical and hemodynamic parameters in 142 consecutive ambulatory transplant candidates, mostly in New York Heart Association (NYHA) classes III and IV, with a mean ejection fraction of 20%.
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Over a mean follow-up of 11 ±9 months, 33 patients were transplanted, 41 died, and 68 remained alive. Whereas there was substantial overlap in left ventricular ejection fraction between patients divided by outcome, RV ejection fractions were significantly lower in those who died or were transplanted. Cox multivariate analysis showed three independent prognostic indicators: cause of heart failure, heart failure score, and RV ejection fraction.
The utility of RV functional assessment in less advanced heart disease has been less studied, but the evidence appears similar. In 62 patients with idiopathic dilated cardiomyopathy and a mean ejection fraction of 30%, 40% of whom were in NYHA class II, the RV ejection fraction proved an independent prognostic parameter on multivariate analysis, together with the left ventricular ejection fraction.
Similarly, a more recent study (1998), addressing the prognostic role of the RV ejection fraction specifically in moderate heart failure, identified NYHA class, percent of maximal predicted V02, and the RV ejection fraction as independent predictors of survival and event-free cardiac survival. The receiver operator characteristic (ROC) curve of RV ejection could be used to determine cardiovascular mortality and urgent transplantation at 1 year. The value of 35% had the highest sensitivity and specificity (70% and 58%, respectively). Separate analysis of patients by NYHA class (II and III) showed that the RV ejection fraction remained the best predictor of event-free survival (free from cardiovascular death or urgent transplantation). Hence the utility of the RV ejection fraction in selecting patients at higher risk irrespective of NYHA class.
Since the RV ejection fraction was a more accurate predictor of survival in patients stratified by etiology, and specific studies of the RV ejection fraction in ischemic heart dysfunction are scarce, it is reasonable to assume that the RV ejection fraction has clear prognostic utility only in idiopathic dilated cardiomyopathy. RV function studies are thus indicated routinely in these patients, whatever the degree of congestive heart failure.
There is considerable evidence that patients with primary pulmonary hypertension (PPH) should also undergo RV function assessment. In the largest study of the natural history of PPH (NIH Registry), which included long-term follow-up in 194 patients, the most common cause of death was progressive right heart failure. The finding that patients with symptoms for <1 year and those with symptoms for >3 years had a similar mean pulmonary artery pressure suggests that this parameter rises to fairly high levels early in the disease course and that the main determinant of survival is more the ability of the right heart to cope with the increased workload than the degree of pulmonary hypertension per se.
The right ventricle acts as volume chamber in contrast to the left ventricular pressure chamber. Its shape and mode of contraction are less documented than those of the left ventricle. For these reasons, the best way to assess RV function may differ somewhat from the conventional method employed for the left ventricle (ventricular ejection fraction). It is unsurprising that multivariate analysis in echocardiographic and hemodynamic studies assessing the prognostic import of different variables on right heart function in PPH should have found that right atrial volume or pressure may even obscure the role played by RV function.
Instrumental finding; right ventricular hemodynamics; right ventricular ejection fraction; primary pulmonary hypertension; idiopathic dilated cardiomyopathy; prognosis.