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• Response to Letter to Editors
  Yasuhiro Kondoh, Tomonori Sato, Taiki Furukawa and Ryo Teramachi
  Published on: 17 April 2024
• Letter to Editors
  Arata Azuma, Ganesh Raghu
  Published on: 15 April 2024

• Published on: 17 April 2024

  Response to Letter to Editors

  • Yasuhiro Kondoh, Pulmonologist Tosei General Hospital
  • Other Contributors:
    • Tomonori Sato, Pulmonologist
    • Taiki Furukawa, Pulmonologist
    • Ryo Teramachi, Pulmonologist

  We thank Professors Azuma and Raghu for their excellent suggestions and comments on our paper. Our study demonstrates the importance of pulmonary vascular resistance (PVR) as a prognostic factor in the initial evaluation of patients with interstitial lung disease (ILD) and highlights the greater significance of PVR over mPAP in right heart catheterisation (RHC) (1). We acknowledge that there is generally less emphasis on PVR compared to the more commonly discussed mean pulmonary arterial pressure (mPAP), and it was our intention to address this discrepancy with our study.
  It is important to clarify that we do not recommend systematic RHC at initial evaluation of ILD. Historically, our approach was to perform RHC more frequently at diagnosis, but in recent years, we have limited this to cases where pulmonary hypertension (PH) is suspected. We recently reported a system for predicting mPAP > 20mmHg using a Pa/Ao ratio ≥ 0.9, PaO2 < 80 Torr, and DLco percent predicted < 50% in patients with idiopathic pulmonary fibrosis (IPF) (2). We propose using this system to screen patients before undergoing RHC, with assessments of both mPAP and PVR.
  As Azuma and colleagues pointed out, exercise tolerance tests, including the 6-minute walk test (6MWT), might help in predicting PH. As patients with PH have significantly worse desaturation and walking distance in the 6MWT, those who show significant desaturation and/or reduced walking distance during 6MWT are likely to...

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  We thank Professors Azuma and Raghu for their excellent suggestions and comments on our paper. Our study demonstrates the importance of pulmonary vascular resistance (PVR) as a prognostic factor in the initial evaluation of patients with interstitial lung disease (ILD) and highlights the greater significance of PVR over mPAP in right heart catheterisation (RHC) (1). We acknowledge that there is generally less emphasis on PVR compared to the more commonly discussed mean pulmonary arterial pressure (mPAP), and it was our intention to address this discrepancy with our study.
  It is important to clarify that we do not recommend systematic RHC at initial evaluation of ILD. Historically, our approach was to perform RHC more frequently at diagnosis, but in recent years, we have limited this to cases where pulmonary hypertension (PH) is suspected. We recently reported a system for predicting mPAP > 20mmHg using a Pa/Ao ratio ≥ 0.9, PaO2 < 80 Torr, and DLco percent predicted < 50% in patients with idiopathic pulmonary fibrosis (IPF) (2). We propose using this system to screen patients before undergoing RHC, with assessments of both mPAP and PVR.
  As Azuma and colleagues pointed out, exercise tolerance tests, including the 6-minute walk test (6MWT), might help in predicting PH. As patients with PH have significantly worse desaturation and walking distance in the 6MWT, those who show significant desaturation and/or reduced walking distance during 6MWT are likely to have PH. We agree that there is a need for the development of non-invasive tests that can detect PH and elevated PVR in an earlier stage.

  1. Thorax. 2024 Apr 15;79(5):422-429.
  2. Furukawa T, et al. Eur Respir J. 2018 Jan 18;51(1):1701311.

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  Conflict of Interest:
  YK reports consulting fees from Asahi Kasei Pharma Corporation, Boehringer Ingelheim, Chugai Pharmaceutical, Healios K.K., Janssen Pharmaceutical KK, Shionogi and Taiho Pharmaceutical and lecture fees from Asahi Kasei Pharma Corporation, Bristol Myers Squibb, Boehringer Ingelheim, Eisai, Janssen Pharmaceutical KK, KYORIN Pharmaceutical, Mitsubishi Tanabe Pharma, NIPPON SHINYAKU, Novartis Pharma KK, Shionogi and Teijin Pharma outside the submitted work.

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• Published on: 15 April 2024

  Letter to Editors

  • Arata Azuma, Pulmonologist, MD, PhD Mihara General Hospital and Nippon Medical School
  • Other Contributors:
    • Ganesh Raghu, Pulmonologist, professor of Medicine, MD

  " We congratulate Sato et al to have undertaken the retrospective stud(y that surfaces clinical significance of pulmonary vascular resistance (PVR) as a predictor of mortality in patients with newly diagnosed ILD with normal mean MAP – i.e., < 30mmhg at rest ( 1) .

  While their obsrervation is interesting , are the authors advocating right heart catheterization(RHC) for patients with new onset ILD upfront at the time of initial evaluation undergoing diagnostic interventions for diagnosis of ILD ?

  Indeed, RHC is an invasive procedure, and the potential benefits and risks must be weighed in considering RHC for patients with new onset ILD for prognostication and consideration of possible therapeutic interventions. Are the authors recommending RHC for patients with new onset ILD without clues for pulmonary hypertension ?
  Do the authors have additional non invasive clinical variables/data that correlate with PVR > 2 wood units with mean PAP < 20 mmHg- such as decreased DLCO corrected for hemoglobin, oxygen desaturation with walking, extent of interstitial lung abnormalities , specific diagnosis in patients with new onset ILD that can be used to screen patients to undergo RHC ?
  Perhaps, a noninvasive method using an exercise test as was used in assessing patient's endurance of exercise in patients with IPF treated with pirfenidone for IPF(2) might be a screening test prior to considering RHC as a routine for patients with new ons...

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  " We congratulate Sato et al to have undertaken the retrospective stud(y that surfaces clinical significance of pulmonary vascular resistance (PVR) as a predictor of mortality in patients with newly diagnosed ILD with normal mean MAP – i.e., < 30mmhg at rest ( 1) .

  While their obsrervation is interesting , are the authors advocating right heart catheterization(RHC) for patients with new onset ILD upfront at the time of initial evaluation undergoing diagnostic interventions for diagnosis of ILD ?

  Indeed, RHC is an invasive procedure, and the potential benefits and risks must be weighed in considering RHC for patients with new onset ILD for prognostication and consideration of possible therapeutic interventions. Are the authors recommending RHC for patients with new onset ILD without clues for pulmonary hypertension ?
  Do the authors have additional non invasive clinical variables/data that correlate with PVR > 2 wood units with mean PAP < 20 mmHg- such as decreased DLCO corrected for hemoglobin, oxygen desaturation with walking, extent of interstitial lung abnormalities , specific diagnosis in patients with new onset ILD that can be used to screen patients to undergo RHC ?
  Perhaps, a noninvasive method using an exercise test as was used in assessing patient's endurance of exercise in patients with IPF treated with pirfenidone for IPF(2) might be a screening test prior to considering RHC as a routine for patients with new onset ILD " .

  1. Sato T, et al Thorax 2024
  2. Azuma A, et al AJRCCM 2005

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  Conflict of Interest:
  None declared.

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