The long-term outcomes and prognostic factors of TA patients with PAI were investigated in this study. Of these patients, 90.8% were diagnosed with PH by RHC. Patients with PH were found to have a worse prognosis than patients without PH. Furthermore, 6MWD and PH-targeted therapy were independent predictors of cardiac death and repeated hospitalizations.
Pulmonary vascular damage caused by TA has not received sufficient attention in the clinical setting, apparent by the ACR diagnostic criteria for TA, where the role of pulmonary lesions has been ignored [10]. The prevalence of PAI among TA patients is still unclear, with varying percentages (13.3–61.7%) across different studies depending on disease duration, diagnostic criteria, and study populations [2–4, 11]. During our study period, from the 806 patients with TA, PAI was diagnosed by CTPA in 17.6%. Among TA patients with PAI, more attention should be paid to the diagnosis of PH. Previous studies have indicated that PH is associated with a poor prognosis. Toledano et al. reported a mortality rate of 20.5% in patients with PAI and 33.3% among patients with PH [12]. Yang et al. reported that 58.8% of TA patients with PAI had PH on echocardiography [13]. In their study, PH was defined as an estimated PASP of > 50 mmHg and TRV of > 3.4 m/s, which suggests a high probability of PH according to the European Society of Cardiology/European Respiratory Society guidelines [7]. In contrast, the PH was prevalent in 90.8% in our study and was diagnosed by RHC, which is considered the gold standard. It is important to note that nine patients had an estimated PASP of < 50 mmHg but showed signs of PH on RHC, suggesting that PH in TA patients with PAI is likely underestimated by echocardiography. Another reason for this difference could be related to the duration of the disease, which was longer in the patients of our study than in previous reports [7, 14].
The diagnosis of PAI in patients with TA is often delayed or misdiagnosed because of nonspecific respiratory manifestations and a lack of symptoms of systemic vessel involvement [15]. The main clinical manifestations in our study were dyspnea, chest tightness, hemoptysis, cough, fatigue, and chest pain, which were related to disease duration, severity, and the study population. TA patients with PAI were often misdiagnosed with lung disease in our study, including tuberculosis, pulmonary embolism, CTEPH, congenital malformations, asthma, and IPAH. Previous studies have indicated that diagnosis and treatment delays range from 3 to 72 months in these patients [15–17]. In our study, the median time from the initial symptoms to definitive diagnosis was 15.5 months (range, 2–247 months). Interestingly, one patient with a ventricular septal defect in our study was admitted to several hospitals and was misdiagnosed with both PH associated with congenital heart diseases and IPAH. This indicates the need for adherence to current guidelines, as well as screening for all possible causes of PH before making a final diagnosis.
In our study, 16 patients died from right heart failure caused by PH, which was associated with the PAI of TA. However, the risk factors affecting the prognosis of these patients remain unclear. The univariate regression analysis illustrated that the World Health Organization functional class, 6MWD, TBIL, tricuspid annular plane systolic excursion, the right ventricle/left ventricle ratio, and targeted treatment were all related to composite endpoint events. After adjusting for confounders, 6MWD and targeted therapy were independent predictors of cardiac death and repeated hospital admissions. The first-line treatment of active inflammation is corticosteroids, with suggested initial dosages of 0.5–1 mg/kg/day according to our experience. For the conventional treatment of TA patients with PAI and PH, PH-targeted therapy is necessary to improve the prognosis of these patients. Yang et al. found that the risk of death or readmission significantly increased if PASP was ≥ 100 mmHg in TA patients with PAI [13]. However, our results did not support this finding. This could be due to a PASP value that is lower than baseline in patients with severe right heart failure that significantly decreased the cardiac output at the end-stage. Interestingly, their study demonstrated that patients with an ESR ≥ 20 mm/h had a lower risk of death after repeated hospital admissions. Our findings were somewhat consistent with these results, as patients with PH were found to have lower ESR levels than those without PH. The reason for this phenomenon is unclear. This could be related to the decline of the body's inflammatory response in TA patients with PAI and PH at the end-stage.
A previous study found that both the initial and any changes in the 6MWD are predictive of morbidity and mortality in patients with PH, highlighting its use in clinical management and trials [18–20]. Our results suggest that the baseline 6MWD significantly worsens prognosis, where a lower value indicates a higher risk of death or readmission. Investigations focusing on the efficiency of targeted treatment of PH associated with TA patients are very limited, even in small samples. Sari et al. reported that only one patient with PAI and PH was treated with PH-specific agents, and a decrease in brain natriuretic peptide levels and an improvement in the 6MWD were observed with an 8-year follow-up [21]. Wang et al. found that PH-targeted therapy was useful in a small sample of TA patients with PAI and PH [22]. Our study indicates that PH targeted treatment is related to prognosis, lowering the risk of death and readmission. Additionally, in contrast to the results of Lee et al. [23], we did not find a relationship between PAI and disease activity. This is in accordance with a report from China [24]. The discrepancy between these results could be due to differences in the disease stage of TA because of its gradual onset.
This study has some limitations related to its retrospective cohort design, in addition to being conducted in a single center. Two patients were lost to follow-up, which may have led to an underestimation of mortality. However, as a national research center for TA, our center is a referral region from over the country, including cities, rural, and remote areas. Therefore, these TA patients with PAI are representative of other patients. Moreover, a long-term follow-up was conducted for these patients.