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Copyright ©ERS Journals Ltd 2008
Right ventricular dysfunction and functional limitation in idiopathic pulmonary fibrosis
1 Congenital Heart Centre and Centre for Pulmonary Hypertension, Royal Brompton Hospital, London, 2 Dept of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK. 3 Respiratory Failure Unit, Aristotle University of Thessaloniki, and 4 First Cardiology Dept, AHEPA Hospital, Thessaloniki, Greece.
To the Editors:
We read with great interest the paper by Dal Corso et al. 1 in a recent issue of the European Respiratory Journal. The authors used a 6-min step test to estimate effort tolerance and exercise-related oxyhaemoglobin desaturation in patients with interstitial lung disease. Although desaturation with exertion is well accepted as a prognostic tool in patients with interstitial lung disease, conflicting reports exist regarding the distance covered during the test 2–5. Moreover, evidence is lacking regarding the possible association between cardiac function, exercise capacity and exercise desaturation in patients with interstitial lung disease. In a small cohort of 22 patients (mean±SD age 65±9 yrs) with well-defined idiopathic pulmonary fibrosis (IPF), we used the 6-min walk test (6MWT) to assess prognosis and to investigate the association of exercise capacity with left and right ventricular echocardiographic parameters. All patients underwent a complete echocardiographic study, including two-dimensional, colour flow, spectral Doppler as well as tissue Doppler imaging for the evaluation of right and left ventricular systolic and diastolic function.
Mean time from initial diagnosis of the disease was 9 months. After a median follow-up period of 22 months, five deaths were recorded (four were due to respiratory failure decompensation and one followed sepsis). A cut-off value of 225 m for 6MWT distance predicted survival after follow-up with 100% sensitivity and 60% specificity (area under curve (AUC) 0.77, p = 0.01). Moreover, a cut-off value of >5% for desaturation with exercise predicted mortality with 58% sensitivity and 100% specificity (AUC 0.82, p = 0.006). Amongst all echocardiographic parameters, 6MWT distance correlated significantly with pulmonary artery systolic pressure (r = -0.53, p = 0.01; fig. 1
), early diastolic peak myocardial velocity of the tricuspid annulus (r = -0.45, p = 0.03; fig. 1) and late diastolic peak myocardial velocity of the tricuspid annulus (r = -0.44, p = 0.03). No correlation was found between oxygen desaturation during the 6MWT and any of the echocardiographic parameters.
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Although the number of patients evaluated was small, our results indicate that there is a close association between exercise capacity, indices of right ventricular diastolic function and prognosis in patients with IPF. Exercise capacity in patients with IPF has been shown to be limited mainly by gas exchange and ventilatory impairment 6. The conflicting reports in the literature regarding the relationship between 6MWT distance and mortality in IPF patients probably reflect differences in the exercise protocols and, particularly, the time and reason of the 6MWT termination 2–5. Nevertheless, the majority of authors 2–5 agree that the degree of desaturation seems to be a strong predictor of mortality, as we also confirmed in our cohort. Importantly, exercise capacity is not only dependent on respiratory function; cardiac function and muscle function are other important factors that can come into play 7. Moreover, poor 6MWT performance should raise suspicion of the presence of underlying pulmonary arterial hypertension.
As the prevalence of right ventricular dysfunction is high in patients with end-stage pulmonary disease 8, we believe that the echocardiographic evaluation of right ventricular function can be complementary to clinical evaluation and functional assessment in these patients.
REFERENCES
- Dal Corso S, Duarte SR, Neder JA, et al. A step test to assess exercise-related oxygen desaturation in interstitial lung disease. Eur Respir J 2007;29:330–336.
[Abstract/Free Full Text] - Eaton T, Young P, Milne D, Wells AU. Six-minute walk, maximal exercise tests: reproducibility in fibrotic interstitial pneumonia. Am J Respir Crit Care Med 2005;171:1150–1157.
[Abstract/Free Full Text] - Flaherty KR, Andrei AC, Murray S, et al. Idiopathic pulmonary fibrosis: prognostic value of changes in physiology and six-minute-walk test. Am J Respir Crit Care Med 2006;174:803–809.
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[Abstract/Free Full Text] - Lama VN, Flaherty KR, Toews GB, et al. Prognostic value of desaturation during a 6-minute walk test in idiopathic interstitial pneumonia. Am J Respir Crit Care Med 2003;168:1084–1090.
[Abstract/Free Full Text] - Harris-Eze AO, Sridhar G, Clemens RE, Zintel TA, Gallagher CG, Marciniuk DD. Role of hypoxemia and pulmonary mechanics in exercise limitation in interstitial lung disease. Am J Respir Crit Care Med 1996;154:994–1001.[Abstract]
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- Vizza CD, Lynch JP, Ochoa LL, Richardson G, Trulock EP. Right and left ventricular dysfunction in patients with severe pulmonary disease. Chest 1998;113:576–583.[Web of Science][Medline] [Order article via Infotrieve]
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