Inappropriate Exercise-Induced Increase in Pulmonary Artery Pressure in Patients With Systemic Sclerosis
After evaluating pulmonary artery systolic pressure (PASP) and right ventricular (RV) function at baseline and immediately following exercise in patients with systemic sclerosis (SS) who do not have evidence of resting pulmonary arterial hypertension (PAH), is there an increase in PASP after exercise?
Echocardiograms with Doppler for diastolic function and estimation of PASP were obtained in 172 consecutive SS patients at rest and immediately following bicycle exercise. At baseline, all patients were New York Heart Association class I-II and had a peak tricuspid regurgitation jet velocity ≤3 m/s. Patients were excluded if they had a previous diagnosis of PAH, coronary artery disease, prior heart failure, significant valvular disease, significant interstitial lung disease (ILD) on high-resolution chest computed tomography, or evidence of left ventricular (LV) diastolic dysfunction on echocardiography. The identical protocol was performed on 88 disease-free control subjects.
Control and SS patients were statistically equivalent with respect to gender, age, basal surface area, and blood pressure. Additionally, LV diastolic and systolic dimensions and ejection fraction as well as cardiac index (CI) and mitral E/A ratio were statistically not different. PASP in controls at rest was 20.6 ± 3.7 mm Hg versus 26.2 ± 5.3 mm Hg in SS. RV dimensions and tricuspid annular plane systolic excursion were not different between the two groups. At the time of exercise, both groups achieved equivalent heart rate and workload. PASP following exercise was 25.9 ± 3.3 versus 36.9 ± 8.7 mm Hg in controls and SS patients, and the Δ PASP was 5.3 ± 4.1 in controls versus 10.7 versus 5.9 mm Hg in SS patients. Δ CI (L/m/m2) was 4.6 ± 2.3 versus 2.8 ± 1.2 in SS patients and Δ PASP/Δ CI was 1.2 ± 2.2 in controls versus 4.5 ± 4.3 in SS (all comparisons ≤0.0005). At rest, PASP values were normally distributed in both controls and SS. Following exercise, PASP values remained normally distributed, with a peak at 25.9 mm Hg in controls. Evaluation of PASP in SS patients following exercise revealed a bimodal distribution with a peak at 37.8 mm Hg and a second peak at 52.2 mm Hg. The second peak included patients with PASP ≥48 mm Hg, representing 13% of the total SS population. There were no identifiable clinical differences between the two SS populations with respect to age, systolic blood pressure, prevalence of mild pulmonary fibrosis, LV diastolic properties, or baseline PASP. RV systolic function was normal at rest in all SS patients. RV relaxation time was longer and RV annular E/A ratios were lower in SS patients than in control subjects who also exhibited evidence of worsening RV diastolic properties immediately following exercise. Patients in the lowest quartile of LV diastolic function had higher post-exercise PASP and Δ PASP than subjects in the highest quartile of LV diastolic function.
Exercise echocardiography identifies a subset of SS patients with an abnormal increase in PASP following exercise, who concurrently have signs of RV dysfunction.
SS has long been known to be associated with multiple complications, including development of PAH, which may become advanced and fatal. This study evaluated a consecutive series of SS patients without evidence of PAH at rest and nicely demonstrated not only an overall increase in PASP following exercise in these patients, but a bimodal distribution in which 13% of the SS population had an even more pathologically elevated PASP following exercise. There were no standard clinical correlates identifying this subpopulation; however, patients in that subgroup had subtle abnormalities in RV function at rest and following exercise. While no patient had advanced ILD, patients with even mild ILD tended to have slightly higher PASP with exercise than did those completely free of ILD. The only other subtle correlate of a more elevated PASP with exercise was evidence of mild LV diastolic dysfunction, all patients with significant LV diastolic dysfunction having been excluded by protocol. Whether the small (13%) subset of SS patients with more dramatic elevation of PASP following exercise will have a different clinical course or natural history remains conjectural.
Keywords: Ventricular Function, Left, Hypertension, Pulmonary, Heart Failure, Blood Pressure, Pulmonary Fibrosis, New York, Heart Rate, Pulmonary Artery, Scleroderma, Systemic, Echocardiography
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