According to this study’s findings, older age was associated with suggestive of PH. However, there was no accompanying deterioration in heart (both systolic and diastolic) or lung function, but rather parameters indicating volume depletion (small LV end-systolic dimension and increased relative wall thickness) were related to suggestive of PH. There were no significant complications after surgery in patients with preoperative PH, and PH did not progress in any case during the follow-up. Although this study was not a prospective study and did not assess prognosis, there were no reports of postoperative complications associated with suggestive of PH after surgery.
Role of echocardiography
The role of echocardiography in screening of PH is pivotal in various clinical settings, including congenital heart disease and connective tissue disease [8-11]. PH is a hemodynamic and pathophysiologic condition defined as an increase in mean pulmonary artery pressure ≥25 mm at rest as assessed by right heart catheterization. It can be found in multiple clinical conditions with distinct pathogenetic and clinical features, such as pulmonary arterial hypertension and left heart, lung, and thromboembolic diseases . Because of the nature of PH, in the early stages of the disease, symptoms are non-specific, and there are often no significant physical changes. If there are risk factors, it is important to screen for PH before irreversible change occurs . In this regard, TTE, by providing direct and/or indirect signs of elevated pulmonary artery pressure, is an excellent noninvasive screening test for patients with symptoms or risk factors for PH, such as connective tissue disease, anorexigen use, pulmonary embolism, heart failure, and heart murmurs. It may also provide key information on both the etiology and prognosis of PH . A small degree of TR is present in most healthy individuals . TR peak velocity can be analyzed in the inflow view of the parasternal long axis, parasternal short axis view, and apical four-chamber view using CW Doppler imaging. The peak TR velocity reflects the PG between the right ventricle and RA. Using the modified Bernoulli equation, the PG between the RA and right ventricle can be estimated from the peak velocity of TR between the two chambers: peak PG = 4 × (peak TR velocity)2 [6,7]. Thus, RVSP is defined as the sum of RAP and peak PG, and RVSP >37 mmHg is suggestive of PH . Peak TR velocity <2.8-2.9 m/s and peak systolic pressure <35-36 mmHg are normal ranges [14,15]. Therefore, in this study, a patient in whom the RVSP was <35 was considered normal, and patients with RVSP of 35 mmHg were considered to have PH and were compared with those without PH.
Factors associated with elevated RVSP
RVSP increases with age in patients without other pathologies [16,17]. Likewise, patients with elevated RVSP were older than those with normal RVSP in this study.
According to Wroebl et al.’ study, the higher the RVSP estimated by TTE performed before lung transplantation in patients with chronic obstructive pulmonary disease (COPD), the longer the duration of treatment for mechanical ventilator after surgery . However, postoperative cardiac complications were not increased in patients with high RVSP in this study. Cleary, there were no patients with significant COPD or with poor lung function enrolled in this study, and there were no significant differences in PFT results in both patient groups.
Interestingly, small LV size (smaller end-systolic dimension of LV, small LV dimension) and slightly increased LV EF were associated with elevated RVSP, and smaller LVD and higher LV EF were independently associated with elevated RVSP. Small LV size was also associated with poor prognosis in patients with heart failure independent of EF , an increased risk of thrombosis in patients with LV assist device , and poor exercise capacity even in patients with normal EF . Several factors affect the standard value for LV dimension including age, sex, and race; among them, aging is related with a small LV chamber size . According to this study’s results, aging and elevated RVSP are related, so small LV cavity size, which is associated with elevated RVSP, may also be related to aging. However, since small LV cavity size is also an indicator that reflects volume depletion , it can be inferred whether it is related to an increase in RVSP due to vasoconstriction associated with volume depletion .
This study has a few limitations. Firstly, this was a single center study with a small study population, which is a major limitation. Secondly, in this study, it was not confirmed whether patients with PH before surgery improved after surgery. Thirdly, in particular, since this study had a retrospective study design, evaluation of the RV function was not routine. Therefore, an accurate evaluation of the RV function was not performed in patients with PH. However, the patients included in this study had normal right atrial and RV sizes, and no patients showed clinically significant RV failure.
TTE is widely used to identify cardiac function and causes in patients with various clinical conditions and symptoms, including heart disease. Therefore, even in situations where PH is not suspected (it does not belong to one of the five classifications of PH), RVSP is elevated. If RVSP is elevated without any other abnormalities on TTE that was performed to differentiate the cause of non-specific symptoms, such as dyspnea or chest pain, it is not easy to suspect PH or necessary to conduct an invasive work-up immediately. In this study, studies of PH found in patients with an MT revealed that the elevation of RVSP without other abnormalities was not clinically significant and was not associated with a poor prognosis.