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Purpose Pacing to increase resting heart rate (HR) is commonly employed in order to improve hemodynamics and cardiac output (CO), particularly in post-operative setting when right ventricle (RV) dysfunction is present. We tested if right atrial (RA) pacing improves RV hemodynamics acutely, and if the degree of baseline RV dysfunction modifies this relationship. Methods We prospectively enrolled adult subjects with known or suspected pulmonary arterial hypertension (PAH) who underwent elective right heart catheterization between January 2013 and April 2016. RV pressure-volume (PV) analysis was performed with conductance catheters. RV volumes were calibrated by cardiac MRI same day. After measuring baseline PV data, a bipolar pacing wire was positioned in the RA and rate set to 80 to 90 beats per minute (bpm). Rate was increased in steps of 20 bpm. PV loops were recorded at end-expiration after 1 minute in each group: 80-99, 100-119, and 120-139 bpm. Parametric data were analyzed by Repeated Measures ANOVA, and non-parametric data were analyzed by Friedman Test. Baseline hemodynamic predictors of CO were analyzed by Repeated Measures simple linear regression. Results Twenty-three subjects were included in this analysis. Baseline mean RA pressure was 7 ± 3 mmHg with pulmonary vascular resistance of 5.2 ± 4.1 wood units. As HR increased with RA pacing, stroke volume (SV) declined in each pacing group (68±22, 61±19, 54±21 mL, respectively; p Conclusion As heart rate increases with RA pacing, RV contractility and CO increase modestly at the expense of cardiac efficiency.

Rationale: New isolation of Pseudomonas aeruginosa (Pa) is generally treated with inhaled antipseudomonal antibiotics such as tobramycin inhalation solution (TIS). A therapeutic approach that complements traditional antimicrobial therapy by reducing the risk of pulmonary exacerbation and inflammation may ultimately prolong the time to Pa recurrence. Objectives: To test the hypothesis that the addition of azithromycin to TIS in children with cystic fibrosis and early Pa decreases the risk of pulmonary exacerbation and prolongs the time to Pa recurrence. Methods: The OPTIMIZE (Optimizing Treatment for Early Pseudomonas aeruginosa Infection in Cystic Fibrosis) trial was a multicenter, double-blind, randomized, placebo-controlled, 18-month trial in children with CF, 6 months to 18 years of age, with early Pa. Azithromycin or placebo was given 3× weekly with standardized TIS. Measurements and Main Results: The primary endpoint was the time to pulmonary exacerbation requiring antibiotics and the secondary endpoint was the time to Pa recurrence, in addition to other clinical and safety outcomes. A total of 221 participants (111 placebo, 110 azithromycin) out of a planned 274 were enrolled. Enrollment was stopped early by the NHLBI because the trial had reached the prespecified interim boundary for efficacy. The risk of pulmonary exacerbation was reduced by 44% in the azithromycin group as compared with the placebo group (hazard ratio, 0.56; 95% confidence interval, 0.37–0.83; P = 0.004). Weight increased by 1.27 kg in the azithromycin group compared with the placebo group (95% confidence interval, 0.01–2.52; P = 0.046). No significant differences were seen in microbiological or other clinical or safety endpoints. Conclusions: Azithromycin was associated with a significant reduction in the risk of pulmonary exacerbation and a sustained improvement in weight, but had no impact on microbiological outcomes in children with early Pa. Clinical trial registered with clinicaltrials.gov (NCT02054156).

Right heart failure is a cause of morbidity and mortality in common and rare heart and lung diseases. Exposure to traffic-related air pollution is linked to left ventricular hypertrophy, heart failure, and death. Relationships between traffic-related air pollution and right ventricular (RV) structure and function have not been studied.To characterize the relationship between traffic-related air pollutants and RV structure and function.We included men and women with magnetic resonance imaging assessment of RV structure and function and estimated residential outdoor nitrogen dioxide (NO2) concentrations from the Multi-ethnic Study of Atherosclerosis, a study of individuals free of clinical cardiovascular disease at baseline. Multivariable linear regression estimated associations between NO2 exposure (averaged over the year prior to magnetic resonance imaging) and measures of RV structure and function after adjusting for demographics, anthropometrics, smoking status, diabetes mellitus, and hypertension. Adjustment for corresponding left ventricular parameters, traffic-related noise, markers of inflammation, and lung disease were considered in separate models. Secondary analyses considered oxides of nitrogen (NOx) as the exposure.The study sample included 3,896 participants. In fully adjusted models, higher NO2 was associated with greater RV mass and larger RV end-diastolic volume with or without further adjustment for corresponding left ventricular parameters, traffic-related noise, inflammatory markers, or lung disease (all P0.05). There was no association between NO2 and RV ejection fraction. Relationships between NOx and RV morphology were similar.Higher levels of NO2 exposure were associated with greater RV mass and larger RV end-diastolic volume.