Pulmonary Vascular Response Patterns to Exercise: Is there a Role for Pulmonary Arterial Pressure Assessment during Exercise in the Post-Dana Point Era?

Pulmonary capillary hemangiomatosis: the role of invasive cardiopulmonary exercise testing

Pulmonary capillary hemangiomatosis (PCH) is a rare form of pulmonary arterial hypertension (PAH) characterized by pulmonary capillary proliferation and pseudoinvasion of collagenous septal structures. PCH is often accompanied by veno-occlusive changes and pulmonary hypertensive arterial remodeling. The clinical and pathological diagnosis of PCH can be subtle and easily missed. Most reported cases of PCH have been associated with resting PAH. We report the cases of 3 patients who initially presented with exertional dyspnea with normal to mildly elevated resting pulmonary arterial pressures and marked intrapulmonary shunting. In all 3 patients, invasive cardiopulmonary exercise testing was suggestive of pulmonary vascular disease. Owing to abnormalities on invasive exercise testing, lung biopsies were performed; these were diagnostic of PCH, and the patients were referred for lung transplantation. We describe unique features of these 3 cases-including novel pathological findings and the presence of intrapulmonary shunting in all 3 patients-and we discuss the role of cardiopulmonary exercise testing in the evaluation of PCH.

Genetic and hypoxic alterations of the microRNA-210-ISCU1/2 axis promote iron-sulfur deficiency and pulmonary hypertension

Iron-sulfur (Fe-S) clusters are essential for mitochondrial metabolism, but their regulation in pulmonary hypertension (PH) remains enigmatic. We demonstrate that alterations of the miR-210-ISCU1/2 axis cause Fe-S deficiencies in vivo and promote PH. In pulmonary vascular cells and particularly endothelium, hypoxic induction of miR-210 and repression of the miR-210 targets ISCU1/2 down-regulated Fe-S levels. In mouse and human vascular and endothelial tissue affected by PH, miR-210 was elevated accompanied by decreased ISCU1/2 and Fe-S integrity. In mice, miR-210 repressed ISCU1/2 and promoted PH. Mice deficient in miR-210, via genetic/pharmacologic means or via an endothelial-specific manner, displayed increased ISCU1/2 and were resistant to Fe-S-dependent pathophenotypes and PH. Similar to hypoxia or miR-210 overexpression, ISCU1/2 knockdown also promoted PH. Finally, cardiopulmonary exercise testing of a woman with homozygous ISCU mutations revealed exercise-induced pulmonary vascular dysfunction. Thus, driven by acquired (hypoxia) or genetic causes, the miR-210-ISCU1/2 regulatory axis is a pathogenic lynchpin causing Fe-S deficiency and PH. These findings carry broad translational implications for defining the metabolic origins of PH and potentially other metabolic diseases sharing similar underpinnings.

Pulmonary vascular response patterns during exercise in interstitial lung disease

When overt pulmonary hypertension arises in interstitial lung disease (ILD), it contributes to exercise intolerance. We sought to determine the functional significance of abnormal pulmonary arterial pressure (PAP) responses to exercise in ILD.27 ILD patients and 11 age-matched controls underwent invasive cardiopulmonary exercise testing (iCPET). Mean PAP (mPAP) was indexed to cardiac output (Q'T) during exercise, with a mPAP-Q'T slope ≥3 mmHg·min·L(-1) defined as an abnormal pulmonary vascular response.All control subjects had mPAP-Q'T slopes <3 mmHg·min·L(-1) (mean±sem 1.5±0.1 mmHg·min·L(-1)). 15 ILD patients had mPAP-Q'T slopes ≥3 mmHg·min·L(-1) (4.1±0.2 mmHg·min·L(-1)) and were labelled as having ILD plus pulmonary vascular dysfunction (PVD). Subjects without pulmonary hypertension and with mPAP-Q´T slopes <3 mmHg·min·L(-1) (1.9±0. 2 mmHg·min·L(-1)) were labelled as ILD minus PVD (n=12). ILD+PVD and ILD-PVD patients did not differ in terms of age, sex, body mass index, pulmonary function testing or degree of exercise oxygen desaturation. Peak oxygen consumption was lower in ILD+PVD than in ILD-PVD (13.0±0.9 versus 17±1.1 mL·kg(-1)·min(-1), p=0.012) and controls (19.8±1.7 mL·kg(-1)·min(-1), p=0.003). ILD+PVD patients had increased dead space volume (VD)/tidal volume (VT) and minute ventilation/carbon dioxide production at the anaerobic threshold.In ILD, mPAP-Q'T slope ≥3 mmHg·min·L(-1) is associated with lower peak oxygen consumption, increased VD/VT and inefficient ventilation. While noninvasive parameters were unable to predict those with abnormal pulmonary vascular responses to exercise, iCPET-derived mPAP-Q'T slope may aid in identifying physiologically significant, early pulmonary vascular disease in ILD.

Hemodynamic responses to rapid saline loading: the impact of age, sex, and heart failure

BACKGROUND

Hemodynamic assessment after volume challenge has been proposed as a way to identify heart failure with preserved ejection fraction. However, the normal hemodynamic response to a volume challenge and how age and sex affect this relationship remain unknown.

METHODS AND RESULTS

Sixty healthy subjects underwent right heart catheterization to measure age- and sex-related normative responses of pulmonary capillary wedge pressure and mean pulmonary arterial pressure to volume loading with rapid saline infusion (100-200 mL/min). Hemodynamic responses to saline infusion in heart failure with preserved ejection fraction (n=11) were then compared with those of healthy young (<50 years of age) and older (≥50 years of age) subjects. In healthy subjects, pulmonary capillary wedge pressure increased from 10±2 to 16±3 mm Hg after ~1 L and to 20±3 mm Hg after ~2 L of saline infusion. Older women displayed a steeper increase in pulmonary capillary wedge pressure relative to volume infused (16±4 mm Hg·L(-1)·m(2)) than the other 3 groups (P≤0.019). Saline infusion resulted in a greater increase in mean pulmonary arterial pressure relative to cardiac output in women compared with men regardless of age. Subjects with heart failure with preserved ejection fraction exhibited a steeper increase in pulmonary capillary wedge pressure relative to infused volume (25±12 mm Hg·L(-1)·m(2)) than healthy young and older subjects (P≤0.005).

CONCLUSIONS

Filling pressures rise significantly with volume loading, even in healthy volunteers. Older women and patients with heart failure with preserved ejection fraction exhibit the largest increases in pulmonary capillary wedge pressure and mean pulmonary arterial pressure.