A Right Heart Catheterization for the Diagnosis of Pulmonary Hypertension

FOR RELATED ARTICLE, SEE PAGE 684A right heart catheterization with invasive measurements of pulmonary vascular pressures is the gold standard for the diagnosis of pulmonary hypertension (PH).1Simonneau G. Montani D. Haemodynamic definitions and updated clinical classification of pulmonary hypertension.Eur Respir J. 2019; 53: 1801913Crossref PubMed Scopus (2071) Google Scholar However, there is little advice in guidelines on how to apply the procedure, except that it is to be done in the supine position with reading of pulmonary artery pressure (PAP) and wedged PAP (PAWP) at end-expiration.2Galiè N. Humbert M. Vachiery J.L. et al.2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension: The Joint Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS) Endorsed by: Association for European Paediatric and Congenital Cardiology (AEPC), International Society for Heart and Lung Transplantation (ISHLT).Eur Heart J. 2016; 37: 67-119Crossref PubMed Scopus (4318) Google Scholar The topic was rediscussed at the World Symposium on Pulmonary Hypertension held in 2018; consensus confirmed that PAP and PAWP should be measured without correction for respiratory pressure swings.3Vachiéry J.L. Tedford R.J. Rosenkranz S. et al.Pulmonary hypertension due to left heart disease.Eur Respir J. 2019; 53: 1801897Crossref PubMed Scopus (322) Google Scholar FOR RELATED ARTICLE, SEE PAGE 684 In this issue of CHEST, Khirfan et al4Khirfan G. Melillo C.A. Al Abdi S. et al.Impact of esophageal pressure measurement on pulmonary hypertension diagnosis in patients with obesity.Chest. 2022; 162: 684-692Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar argue that this method may not always be reliable. The authors found that correction for respirophasic changes by concomitant measurement of esophageal pressure and PAP in patients with obesity decreased the percentage of postcapillary PH from 60% to 8% and increased the percentages of no PH and precapillary PH from 0% to 23 % and 2% to 25 %, respectively. These are huge differences that, if accepted, would potentially lead to change in therapy. The data reported by Khirfan et al4Khirfan G. Melillo C.A. Al Abdi S. et al.Impact of esophageal pressure measurement on pulmonary hypertension diagnosis in patients with obesity.Chest. 2022; 162: 684-692Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar are consistent with a previous demonstration that exclusive reliance on end-expiratory PAWP leads to a false diagnosis of postcapillary PH in 29% of patients with clinically established precapillary disease, particularly in those with increased BMI.5LeVarge B.L. Pomerantsev E. Channick R.N. Reliance on end-expiratory wedge pressure leads to misclassification of pulmonary hypertension.Eur Respir J. 2014; 44: 425-434Crossref PubMed Scopus (51) Google Scholar Khirfan et al4Khirfan G. Melillo C.A. Al Abdi S. et al.Impact of esophageal pressure measurement on pulmonary hypertension diagnosis in patients with obesity.Chest. 2022; 162: 684-692Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar demonstrate that these differences are explained by the direct transmission of intrathoracic pressure to PAP and PAWP. The influence of intrathoracic pressures on the circulatory system has attracted attention since the introduction of cardiac catheterization in clinical practice in the 1950s.6Sharpey-Schafer E.P. The mechanism of syncope after coughing.BMJ. 1953; 2: 860-863Crossref PubMed Scopus (81) Google Scholar This effect is illustrated in Figure 1 by a historic recording of esophageal pressure and PAWP with the effects of coughing to increase intrathoracic pressure acutely.6Sharpey-Schafer E.P. The mechanism of syncope after coughing.BMJ. 1953; 2: 860-863Crossref PubMed Scopus (81) Google Scholar The transmission of intrathoracic pressures to pulmonary vascular pressures has been demonstrated repeatedly.7Rice D.L. Awe R.J. Gaasch W.H. et al.Wedge pressure measurement in obstructive pulmonary disease.Chest. 1974; 66: 628-632Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar,8Boerrigter B.G. Waxman A.B. Westerhof N. Vonk-Noordegraaf A. Systrom D.M. Measuring central pulmonary pressures during exercise in COPD: how to cope with respiratory effects?.Eur Respir J. 2014; 43: 1316-1325Crossref PubMed Scopus (66) Google Scholar The heart and the pulmonary circulation are within the chest, which is a pressure chamber with slightly subatmospheric pressure that is generated by opposing elastic recoil of lungs and chest wall. Intrathoracic pressure is approximately at −1 to 2 mm Hg at functional residual capacity in healthy resting subjects. Pulmonary vascular pressures and left ventricular end-diastolic pressure (LVEDP) vary with pleural pressure that is assessed by esophageal pressure in a close to 1:1 ratio.5LeVarge B.L. Pomerantsev E. Channick R.N. Reliance on end-expiratory wedge pressure leads to misclassification of pulmonary hypertension.Eur Respir J. 2014; 44: 425-434Crossref PubMed Scopus (51) Google Scholar, 6Sharpey-Schafer E.P. The mechanism of syncope after coughing.BMJ. 1953; 2: 860-863Crossref PubMed Scopus (81) Google Scholar, 7Rice D.L. Awe R.J. Gaasch W.H. et al.Wedge pressure measurement in obstructive pulmonary disease.Chest. 1974; 66: 628-632Abstract Full Text Full Text PDF PubMed Scopus (39) Google Scholar, 8Boerrigter B.G. Waxman A.B. Westerhof N. Vonk-Noordegraaf A. Systrom D.M. Measuring central pulmonary pressures during exercise in COPD: how to cope with respiratory effects?.Eur Respir J. 2014; 43: 1316-1325Crossref PubMed Scopus (66) Google Scholar Hyperventilation is associated with more negative inspiratory pressure and more positive expiratory pressures and eventual dynamic hyperinflation, which further increases and prolongs positive end-expiratory pressures. Dynamic hyperinflation may occur in exercising healthy subjects but is observed more constantly in patients with obstructive lung disease or obesity. Patients with overweight typically hyperventilate with decreased lung volumes and restrictive physiology associated increase in airway resistance.9Salome C.M. King G.G. Berend N. Physiology of obesity and effects of lung function.J Appl Physiol (1985). 2010; 108: 206-211Crossref PubMed Scopus (500) Google Scholar In these circumstances, end-expiratory reading of PAWP and LVEDP may reflect the contribution of esophageal pressure excessively.10Kovacs G. Avian A. Pienn M. Naeije R. Olschewski H. Reading pulmonary vascular pressure tracings: how to handle the problems of zero leveling and respiratory swings.Am J Respir Crit Care Med. 2014; 190: 252-257Crossref PubMed Scopus (152) Google Scholar On the other hand, except for associated changes in functional residual capacity , this does not matter to pulmonary vascular resistance because PAP and PAWP are affected equally by pleural pressure,10Kovacs G. Avian A. Pienn M. Naeije R. Olschewski H. Reading pulmonary vascular pressure tracings: how to handle the problems of zero leveling and respiratory swings.Am J Respir Crit Care Med. 2014; 190: 252-257Crossref PubMed Scopus (152) Google Scholar which is a point confirmed in the study by Khirfan et al.4Khirfan G. Melillo C.A. Al Abdi S. et al.Impact of esophageal pressure measurement on pulmonary hypertension diagnosis in patients with obesity.Chest. 2022; 162: 684-692Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar One can agree with Khirfan et al4Khirfan G. Melillo C.A. Al Abdi S. et al.Impact of esophageal pressure measurement on pulmonary hypertension diagnosis in patients with obesity.Chest. 2022; 162: 684-692Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar that pulmonary vascular pressure measurements are best corrected by esophageal pressure in patients with increased ventilation or dynamic hyperinflation like in obesity or COPD and especially during exercise. However, esophageal pressure measurements are time-consuming in the catheterization laboratory, require expertise in catheter insertion and calibration, and are not always possible. In our experience, patients find the insertion of an esophageal balloon catheter more uncomfortable than a cardiac catheterization. In the study by Khirfan et al,4Khirfan G. Melillo C.A. Al Abdi S. et al.Impact of esophageal pressure measurement on pulmonary hypertension diagnosis in patients with obesity.Chest. 2022; 162: 684-692Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar the esophageal probe could not be placed in four patients because of poor tolerance to the procedure (ie, gagging or coughing and/or persistent coiling of the catheter in the pharynx). Repetitive attempts were needed in eight other patients. There has been suggestion that right atrial pressure could be a surrogate of esophageal pressure.8Boerrigter B.G. Waxman A.B. Westerhof N. Vonk-Noordegraaf A. Systrom D.M. Measuring central pulmonary pressures during exercise in COPD: how to cope with respiratory effects?.Eur Respir J. 2014; 43: 1316-1325Crossref PubMed Scopus (66) Google Scholar However, right atrial pressure was not correlated to esophageal pressure in the study by Khirfan et al.4Khirfan G. Melillo C.A. Al Abdi S. et al.Impact of esophageal pressure measurement on pulmonary hypertension diagnosis in patients with obesity.Chest. 2022; 162: 684-692Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar A satisfactory compromise therefore may be to average pressure readings over several respiratory cycles.8Boerrigter B.G. Waxman A.B. Westerhof N. Vonk-Noordegraaf A. Systrom D.M. Measuring central pulmonary pressures during exercise in COPD: how to cope with respiratory effects?.Eur Respir J. 2014; 43: 1316-1325Crossref PubMed Scopus (66) Google Scholar,10Kovacs G. Avian A. Pienn M. Naeije R. Olschewski H. Reading pulmonary vascular pressure tracings: how to handle the problems of zero leveling and respiratory swings.Am J Respir Crit Care Med. 2014; 190: 252-257Crossref PubMed Scopus (152) Google Scholar This actually was proposed for exercise but not resting measurements in European guidelines.2Galiè N. Humbert M. Vachiery J.L. et al.2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension: The Joint Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS) Endorsed by: Association for European Paediatric and Congenital Cardiology (AEPC), International Society for Heart and Lung Transplantation (ISHLT).Eur Heart J. 2016; 37: 67-119Crossref PubMed Scopus (4318) Google Scholar A more consistent recommendation hopefully will be issued in the near future. Another interesting finding by Khirfan et al4Khirfan G. Melillo C.A. Al Abdi S. et al.Impact of esophageal pressure measurement on pulmonary hypertension diagnosis in patients with obesity.Chest. 2022; 162: 684-692Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar was the effects of body position. In their patients, shifting from supine to sitting decreased both mean PAP and PAWP pressure by 10 to 12 mm Hg, which can be explained in part by decreased systemic venous return and in part by decreased esophageal pressure. It has been shown that end-expiratory esophageal pressure increases by an average of 10 cm H2o (or 7.5 mm Hg) in the supine position in both subjects with and without obesity.11Owens R.L. Campana L.M. Hess L. Eckert D.J. Loring S.H. Malhotra A. Sitting and supine esophageal pressures in overweight and obese subjects.Obesity. 2012; 20: 2354-2360Crossref PubMed Scopus (30) Google Scholar Higher supine values are to be explained mainly by the weight of mediastinal content on the esophageal balloon, the so-called “mediastinal artifact.” In the study by Khirfan et al,4Khirfan G. Melillo C.A. Al Abdi S. et al.Impact of esophageal pressure measurement on pulmonary hypertension diagnosis in patients with obesity.Chest. 2022; 162: 684-692Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar the contribution of the mediastinal artifact to upright decrease in PAWP was estimated to be approximately 70%.4Khirfan G. Melillo C.A. Al Abdi S. et al.Impact of esophageal pressure measurement on pulmonary hypertension diagnosis in patients with obesity.Chest. 2022; 162: 684-692Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar This observation leaves the question open of the ideal body position for the diagnosis of pre- or postcapillary PH. Measurement and interpretation of pulmonary vascular pressures are not easy because of within cardiac cycle and respiratory cycle variations.12Naeije R. Chin K. Differentiating precapillary from postcapillary pulmonary hypertension.Circulation. 2019; 140: 712-714Crossref PubMed Scopus (26) Google Scholar For the cardiac cycle, QRS-gating is probably the best method to ensure that PAWP reading is end-diastolic (that is, the best surrogate for LVEDP to assess left ventricular preload).3Vachiéry J.L. Tedford R.J. Rosenkranz S. et al.Pulmonary hypertension due to left heart disease.Eur Respir J. 2019; 53: 1801897Crossref PubMed Scopus (322) Google Scholar,12Naeije R. Chin K. Differentiating precapillary from postcapillary pulmonary hypertension.Circulation. 2019; 140: 712-714Crossref PubMed Scopus (26) Google Scholar For the respiratory cycle, esophageal pressure corrections are ideal; however, averaging pressures over several respiratory cycles is probably an acceptable compromise.8Boerrigter B.G. Waxman A.B. Westerhof N. Vonk-Noordegraaf A. Systrom D.M. Measuring central pulmonary pressures during exercise in COPD: how to cope with respiratory effects?.Eur Respir J. 2014; 43: 1316-1325Crossref PubMed Scopus (66) Google Scholar,10Kovacs G. Avian A. Pienn M. Naeije R. Olschewski H. Reading pulmonary vascular pressure tracings: how to handle the problems of zero leveling and respiratory swings.Am J Respir Crit Care Med. 2014; 190: 252-257Crossref PubMed Scopus (152) Google Scholar,12Naeije R. Chin K. Differentiating precapillary from postcapillary pulmonary hypertension.Circulation. 2019; 140: 712-714Crossref PubMed Scopus (26) Google Scholar The diagnosis of PH relies on a step-by-step evaluation process with eventual integration of right heart catheterization measurements in the context of a clinical probability.2Galiè N. Humbert M. Vachiery J.L. et al.2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension: The Joint Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS) Endorsed by: Association for European Paediatric and Congenital Cardiology (AEPC), International Society for Heart and Lung Transplantation (ISHLT).Eur Heart J. 2016; 37: 67-119Crossref PubMed Scopus (4318) Google Scholar However, clinicians, in the end, may still face the difficult single number-dependent differential diagnosis between pre- and postcapillary PH. Khirfan et al4Khirfan G. Melillo C.A. Al Abdi S. et al.Impact of esophageal pressure measurement on pulmonary hypertension diagnosis in patients with obesity.Chest. 2022; 162: 684-692Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar show elegantly that esophageal pressure is to be taken into account; even so, uncertainty remains with respect to limits of normal historically determined in the supine position. Outcome studies will be needed to assess the clinical relevance of physiologically orthodox supine vs upright measurements of pulmonary vascular pressures. Financial/nonfinancial disclosures: None declared. Impact of Esophageal Pressure Measurement on Pulmonary Hypertension Diagnosis in Patients With ObesityCHESTVol. 162Issue 3PreviewAdjusting pulmonary hemodynamics for Pes in patients with obesity leads to a pronounced reduction in the number of patients who receive a diagnosis of postcapillary PH. Measuring Pes should be considered in patients with obesity, particularly those with elevated PAWP. Full-Text PDF