| Ventricular performance quantities such as the end-systolic pressure-volume relationship (ESPVR) have been the subject of numerous basic science studies, yet their clinical use remains limited, particularly in the right ventricle (RV). This is primarily due to the difficulty of volume measurements in the small, crescent-shaped RV via catheterization. However, such parameters are a superior indicator of ventricular function compared with other hemodynamic measures used in the prognosis of pulmonary arterial hypertension (PAH), such as pulmonary vascular resistance index (PVRI). Thus, there is clinical interest in methods that estimate ESPVR and related parameters while being minimally invasive.;The aim of this study is to examine one such method, a modified single-beat method which estimates the ventricular-vascular coupling ratio (VVCR), or the ratio of end-systolic ventricular elastance (Ees) to arterial elastance (Ea). Within the single-beat elastance framework, the maximum isovolumic pressure (Pmax,iso) and end-systolic pressure are found; based on a novel assumption about the slopes of Ees and Ea, VVCR is then computed using only pressure. A lower coupling ratio is hypothesized to be a good indicator of RV dysfunction and failure, as represented by the World Health Organization Functional Class (WHO-FC). Furthermore, an initial investigation into a non-invasive form of this method was performed, in which pressure data is obtained from the velocity of the tricuspid regurgitant (TR) jet measured by Doppler ultrasound.;A total of 98 patients undergoing RV catheterization for PAH were used in this study. The VA coupling ratio was calculated using two definitions for end-systole: 32 ms prior to dP/dtmin; and observed Pmax . Logistic regressions were performed for each coupling ratio, PVRI, and the combination of ratio (Pmax) and PVRI against WHO-FC. The corrected Akaike Information Criteria (AICc) was computed for each regression, and each regression equation was used to predict the WHO-FC for each patient, and correct and incorrect predictions were compared for each method. The AICc for PVRI was slightly lower at 185.12 than the ratio (Pmax) at 187.75 or ratio (Pes) at 188.70, implying a slightly better yet comparable fit to the data by PVRI. Furthermore, ratio (Pmax) was as good or better at predicting WHO-FC II (66.7% for ratio and 41.7% for PVRI) and WHO-FC III (52.4% for each), and the combination of ratio and PVRI was better than PVRI alone at predicting both WHO-FC II (58.3%) and WHO-FC III (61.9%). Therefore, it is likely that the VA coupling ratio contains useful information reflective of RV dysfunction and failure that is not necessarily reflected by PVRI, and shows promise for clinical use in the prognosis of PAH in the future. |
