Individuals with pulmonary hypertension (PH) have higher right-ventricular stroke work index and right-ventricular minute work index and lower stroke volume divided by end-systolic volume (SV/ESV) due to left-sided heart disease, according to study results recently published in the Journal of Cardiothoracic and Vascular Anesthesia. Cardiac index was similar among the individuals studied.

This exploratory study included 33 individuals treated with cardiac surgery for left-sided heart disease, among whom 10 had PH (defined as pulmonary artery pressure ≥25 mmHg). All participants were aged 20 or older and underwent surgery from September 2016 and March 2018.

Right-ventricular stroke work index was evaluated by taking the integral of the pressure-volume curve. SV/ESV was used to estimate right ventriculo-arterial coupling. Individuals with and without PH due to left-sided heart disease were compared in terms of right ventricular energetics.

Due to a small sample size, the Mann-Whitney U test was used to examine the differences between groups, while the Fisher exact test was used to examine differences in binary variables. 

Compared with no PH, individuals with PH had significantly higher right-ventricular stroke work index (690.7 mmHg·mL/m [95% CI, 601.6-737.1] vs 440.9 mmHg·mL/m [95% CI, 330.8-585.3]; P =.015) and right-ventricular minute work index (60,068 mmHg·mL/m²/min [95% CI, 35,547-68,741] vs 26,351 mmHg·mL/m²/min [95% CI, 17,316-32,517]; P =.011).

Cardiac index was statistically comparable between those with PH (2.5 L/min/m² [95% CI, 2.5-3.0]) and without (2.8 L/min/m² [95% CI, 2.4-3.0]; P =.798). Those with PH showed significantly lower SV/ESV compared with those without (0.520 [95% CI, 0.305-0.810] vs 0.820 [95% CI, 0.650-1.090]; P =.007).

At the end of surgery, those with PH were given a higher dose of catecholamine agents than those without (4.5 µg/kg/min [95% CI, 3.6-5.2] vs 2.8 µg/kg/min [95% CI, 2.5-3.2]; P =.003). 

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Limitations to this study include a small sample size and the use of simplified formulas to estimate end-systolic elastance, ventriculo-arterial coupling, and effective arterial elastance.

Study researchers concluded that “although cardiac index was similar between patients with and without PH because of [left-sided heart disease], [right-ventricular minute work index] was significantly higher in patients with PH. [Right-ventricular stroke work index] was significantly higher in patients with PH despite similar [stroke volume indexed for body surface area]. In addition, right ventriculo-arterial coupling (SV/ESV) was significantly lower in patients with PH, suggesting that patients with postcapillary PH have inefficient [right-ventricular] performance.”

Reference

Kanemaru E, Yoshitani K, Kato S, Fujii T, Tsukinaga A, Ohnishi Y. Comparison of right ventricular function between patients with and without pulmonary hypertension owing to left-sided heart disease: assessment based on right ventricular pressure-volume curves [published online May 27, 2019]. J Cardiothorac Vasc Anesth.  doi:10.1053/j.jvca.2019.05.025