Pulmonary valve acceleration fraction as a novel echo parameter to evaluate systolic pulmonary artery pressure during exercise echocardiography
Authors: Vakalis K , Berrill M , Meric B , Jimeno M , Chester R , Barron A , Kipourou K , Baltabaeva A 
Published: October 2024

Abstract

Background/Introduction
Long-COVID is a disabling chronic condition. Some patients have features of exercise-induced pulmonary hypertension (PHT) but non-invasive assessment during exercise stress echo (SE) is often limited by absence of reliable jet of tricuspid regurgitation (TR). We aimed to investigate novel Doppler echo parameters elicited from right ventricular (RV) outflow tract to aid diagnosis of exercise induced PHT among patients referred to our centre with Long-COVID symptoms.

Purpose
We investigated the ratio of the pulmonary valve acceleration time (PV AccT) to RV ejection time (RV ET) to calculate the pulmonary acceleration fraction (PV AccT/RV ET), thereby adjusting to heart rate. To identify its utility to estimate pulmonary artery pressure (PASP) during SE we correlated the PV AccT/RV ET and the TR-estimated RV systolic pressure (RVSP) in patients referred for evaluation of exercise-induced PHT in Long-Covid patients.

Methods
We developed a dedicated Covid-19 SE protocol to assess RV and pulmonary hemodynamics. From November 2022 to February 2023 all consecutive patients with Long-COVID symptoms underwent supine bike exercise with 3-min increments of workload of 25W. We did not evaluate the inferior vena cava during exercise, therefore estimated pressures from maximal TR jet velocities only.

Results
We enrolled 93 consecutive patients. The mean age was 50.1 years, 42.9% were female. No patients had RV impairment or RVSP &gt;40mmHg at baseline. The average exercise time was 12.4 minutes, only 33% achieved the sub-maximum target heart rate (THR), in 50/93 (53.7%) reasons for termination were recorded as shortness of breath. The pulmonary acceleration fraction could be recorded in every patient at rest and at stress, while 20/92 (21.7%) patients had insufficient spectral Doppler profile of TR to estimate RVSP. The PV acceleration fraction was correlated with the available RVSPs during exercise (Spearman’s ϱ -0.446 (95% CI -0.606- -0.251[p&lt;0.0001]). ROC analysis indicated a pulmonary acceleration fraction ≤0.44 was associated with the maximum Youden index to discriminate an increase in RVSP &gt;20mmHg during exercise (AUC =0.731 [p&lt;0.001]) with a sensitivity and specificity of 70.0% and 80.0%. In logistic regression analysis, a PV acceleration fraction ≤0.44 was independently associated with an increase in RVSP&gt;20mmHg during exercise independently of age, gender and baseline LVEF, LVEDV, TAPSE and baseline RVSP (p&lt;0.001).

Conclusions
Significant proportion of Long-COVID patients are limited by symptoms and not able to achieve THR during exercise. PV Acc T/ PV ET correlates well to RVSP and can be used to estimate PA pressure. A threshold of 0.44 appears independently associated with a benchmark of PA systolic pressure increase of &gt;20mmHg. Further studies needed to evaluate this new marker of pulmonary hypertension in other group of patients.