Key result
Empirical RC time overestimates values by ~76% vs direct curve fit but strongly identifies PAH.
Why the study?
The concept of a constant pulmonary RC time has been challenged, and direct curve-fit analysis remains largely unexplored despite being a feasible reference approach.
How do different methods of calculating pulmonary circulation RC time compare in patients with varying pulmonary hemodynamics?
Observational (n=182)
Single-blind
No
How do different methods of calculating pulmonary circulation RC time compare in patients with varying pulmonary hemodynamics?
Answers are grounded in this paper and cite their sources.
The empirical formula for pulmonary RC time yields systematic overestimation, whereas semilogarithmic analysis provides reliable estimates and identifies prolonged RC time in PAH compared to PH-LHD.
The notion of a constant relationship between resistance and capacitance (RC time) in the pulmonary circulation has been challenged by more recent research. The RC time can be obtained using either a simplified empirical approach or a semilogarithmic equation. Although direct curve-fit analysis is a feasible and ostensibly reference approach for RC analysis, it remains largely unexplored. We aimed to study the relationship between various RC methods in different states of pulmonary hemodynamics. Methods: In total, 182 patients underwent clinically indicated right heart catheterization. The pressure curves were exported and processed using the MATLAB software. We calculated the RC time using the empirical method (RC EST ), semilogarithmic approach (RC SL ), and direct measurement of curve fit (RC FIT ). Results: Among 182 patients, 137 had pulmonary hypertension due to left heart disease (PH-LHD), 35 had pulmonary arterial hypertension (PAH), and 10 demonstrated normal hemodynamics (non-PH). RC EST consistently overestimated the RC FIT and RC SL measurements by a mean of 75%. With all three methods, the RC values were longer in the PAH (RC FIT = 0.36±0.14 s) than in the PH-LHD (0.27±0.1 s) and non-PH (0.27±0.09 s) groups (p < 0.001). Although the RC SL and RC FIT values were similar among the three subgroups, they exhibited broad limits of agreement. Finally, the RC EST demonstrated a strong discriminatory ability (AUC = 0.86, p<0.001, CI = 0.79-0.93) in identifying PAH. Conclusion: RC time in PAH patients was substantially prolonged compared to that in PH-LHD and non-PH patients. The use of the empirical formula yielded systematic RC overestimation. In contrast, the semilogarithmic analysis provided reliable RC estimates, particularly for group comparisons.
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Manouras et al. (2023) conducted an observational in Pulmonary Hypertension (n=182). Empirical RC time calculation (RCEST) vs. Direct curve fit (RCFIT) and semilogarithmic (RCSL) RC time calculation was evaluated on Discriminatory ability of empirical RC time (RCEST) in identifying pulmonary arterial hypertension (AUC 0.86, 95% CI 0.79-0.93, p=<0.001). The empirical method for calculating RC time systematically overestimated values by 76% compared to direct curve fit analysis, but demonstrated strong discriminatory ability (AUC 0.86) for PAH.
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