Spectral analysis of non-contrast fluoroscopy for evaluation of pulmonary perfusion: Feasibility and sensitivity testing with a phantom.

BACKGROUND: Oscillating x-ray attenuation in the lungs provides an opportunity to evaluate pulmonary perfusion without contrast. Recent intensity-based methods have been compared to pulmonary scintigraphy and CT angiography but lack rigorous phantom studies. PURPOSE: A new method to quantify the periodic signal amplitude was employed using spectral analysis. Performance was characterized using a water phantom capable of creating an oscillating x-ray attenuation at physiologic amplitudes. Feasibility in detecting abnormal perfusion was performed on a volunteer with pulmonary vascular disease and compared to pulmonary angiography, the clinical gold standard. METHODS: For each fluoroscopic acquisition, the normalized temporal signal from each pixel was decomposed into its frequency components using Fourier transformation, and the spectral amplitude, defined as the x-ray pulsatility index (XPI), was determined at the desired frequency using a band-pass filter. XPI was displayed as a pixel-wise parametric colormap. Based on XPI maps generated using two human volunteers, a water bath phantom was constructed with a fluctuating fluid height and a 1 cm diameter pulsatility defect. Contrast-to-noise (CNR) of the defect was measured using fluoroscopy images acquired at variable fluid height fluctuation (0.1-1.9 mm) and oscillation frequency (30-60 bpm). Various sampling frame rates (3-30 fps) and acquisition durations (1.8-8 s) using truncated datasets were reconstructed from full datasets. Fluoroscopic images were obtained in a patient just prior to pulmonary angiography in the same projection. RESULTS: XPI maps in human subjects showed high signal to background contrast with high central XPI measuring up to 0.5. Phantom experiments revealed CNR was linearly correlated to fluid height change (r2  = 0.998). CNR is proportional to increasing sampling frame rate and increasing acquisition duration as expected with Fourier analysis. XPI map displayed multifocal perfusion defects in good agreement with pulmonary angiography. CONCLUSION: Spectral analysis is an accurate and sensitive method to detect small changes in periodic x-ray attenuation using a short fluoroscopic acquisition. This method demonstrated good agreement to pulmonary angiography and shows promise for clinical imaging of pulmonary perfusion using standard fluoroscopic methods.

Modeling the impact of delaying transcatheter aortic valve replacement for the treatment of aortic stenosis in the era of COVID-19.

OBJECTIVE: The aim of this study was to model the short term and 2-year overall survival (OS) for intermediate-risk and low-risk patients with severe symptomatic aortic stenosis (AS) undergoing timely or delayed transcatheter aortic valve replacement (TAVR) during the 2019 novel coronavirus (COVID-19) pandemic. METHODS: We developed a decision analysis model to evaluate 2 treatment strategies for both low-risk and intermediate-risk patients with AS during the COVID-19 novel coronavirus pandemic. RESULTS: Prompt TAVR resulted in improved 2-year OS compared with delayed intervention for intermediate-risk patients (0.81 vs 0.67) and low-risk patients (0.95 vs 0.85), owing to the risk of death or the need for urgent/emergent TAVR in the waiting period. However, if the probability of acquiring COVID-19 novel coronavirus is >55% (intermediate-risk patients) or 47% (low-risk patients), delayed TAVR is favored over prompt intervention (0.66 vs 0.67 for intermediate risk; 0.84 vs 0.85 for low risk). CONCLUSIONS: Prompt transcatheter aortic valve replacement for both intermediate-risk and low-risk patients with symptomatic severe AS results in improved 2-year survival when local healthcare system resources are not significantly constrained by the COVID-19.

Clinical Implications of Physical Function and Resilience in Patients Undergoing Transcatheter Aortic Valve Replacement.

Background Gait speed is a reliable measure of physical function and frailty in patients with aortic stenosis undergoing transcatheter aortic valve replacement (TAVR). Slow gait speed pre-TAVR predicts worse clinical outcomes post-TAVR. The consequences of improved versus worsened physical function post-TAVR are unknown. Methods and Results The REPRISE III (Repositionable Percutaneous Replacement of Stenotic Aortic Valve Through Implantation of Lotus Valve System-Randomized Clinical Evaluation) trial randomized high/extreme risk patients to receive a mechanically-expanded or self-expanding transcatheter heart valve. Of 874 patients who underwent TAVR, 576 with complete data at baseline and 1 year were included in this analysis. Slow gait speed in the 5-m walk test was defined as <0.83 m/s. A clinically meaningful improvement (≥0.1 m/s) in gait speed 1 year after TAVR occurred in 39% of patients, 35% exhibited no change, and 26% declined (≥0.1 m/s). Among groups defined by baseline/1-year post-TAVR gait speeds, 1- to 2-year mortality or hospitalization rates were as follows: 6.6% (normal/normal), 8.0% (slow/normal), 20.9% (normal/slow), and 21.5% (slow/slow). After adjustment, slow gait speed at 1 year (regardless of baseline speed) was associated with a 3.5-fold increase in death/hospitalization between 1 and 2 years compared with those with normal baseline/1-year gait speed. Patients whose slow gait speed normalized at 1 year had no increased risk. One-year, but not baseline, gait speed was associated with death or hospitalization between 1 and 2 years (adjusted hazard ratio, 0.83 per 0.1 m/s faster gait; 95% CI, 0.74-0.93, P=0.001). Conclusions Marked heterogeneity exists in the trajectory of physical function after TAVR and this, more than baseline function, has clinical consequences. Identifying and optimizing factors associated with physical resilience after TAVR may improve outcomes. Registration URL: https://www.clini​caltr​ials.gov; Unique identifier: NCT02202434.

Association of Natriuretic Peptide Levels After Transcatheter Aortic Valve Replacement With Subsequent Clinical Outcomes.

Importance: Among those with aortic stenosis, natriuretic peptide levels can provide risk stratification, predict symptom onset, and aid decisions regarding the timing of valve replacement. Less is known about the prognostic significance and potential clinical utility of natriuretic peptide levels measured after valve replacement. Objective: To determine the associations of elevated B-type natriuretic peptide (BNP) levels after transcatheter aortic valve replacement (TAVR) and change in BNP levels between follow-up time points with risk of subsequent clinical outcomes. Design, Setting, and Participants: In this cohort study, patients with severe symptomatic aortic stenosis at intermediate, high, or prohibitive surgical risk for aortic valve replacement who underwent TAVR from the PARTNER IIA cohort, PARTNER IIB cohort, SAPIEN 3 intermediate-risk registry, and SAPIEN 3 high-risk registry were included. B-type natriuretic peptide levels were obtained at baseline and discharge as well as 30 days and 1 year after TAVR. For each measurement, a BNP ratio was calculated using measured BNP level divided by the upper limit of normal for the assay used. Outcomes were evaluated in landmark analyses out to 2 years. Data were collected from April 2011 to January 2019. Main Outcomes and Measures: All-cause death, cardiovascular death, rehospitalization, and the combined end point of cardiovascular death or rehospitalization. Results: Among 3391 included patients, 1969 (58.1%) were male, and the mean (SD) age was 82 (7.5) years. Most patients had a BNP ratio greater than 1 at each follow-up time point, including 2820 of 3256 (86.6%) at baseline, 2652 of 2995 (88.5%) at discharge, 1779 of 2209 (80.5%) at 30 days, and 1799 of 2391 (75.2%) at 1 year. After adjustment, every 1-point increase in BNP ratio at 30 days (approximately equivalent to an increase of 100 pg/mL in BNP) was associated with an increased hazard of all-cause death (adjusted hazard ratio [aHR], 1.11; 95% CI, 1.07-1.15), cardiovascular death (aHR, 1.16; 95% CI, 1.11-1.21), and rehospitalization (aHR, 1.08; 95% CI, 1.03-1.14) between 30 days and 2 years. Among those with a BNP ratio of 2 or more at discharge, after adjustment, every 1-point decrease in BNP ratio between discharge and 30 days was associated with a decreased hazard of all-cause death (aHR, 0.92; 95% CI, 0.88-0.96) between 30 days and 2 years. Conclusions and Relevance: Elevated BNP levels after TAVR was independently associated with increased subsequent mortality and rehospitalizations. Further studies to determine how best to mitigate this risk are warranted.

Lack of a Tricuspid Regurgitation Doppler Signal and Pulmonary Hypertension by Invasive Measurement.

BACKGROUND: Transthoracic echocardiography (TTE) is used to estimate pulmonary artery systolic pressure, but an adequate tricuspid regurgitation velocity (TRV) needed to calculate pulmonary artery systolic pressure is not always present. It is unknown whether the absence of a measurable TRV signifies normal pulmonary artery pressure. METHODS AND RESULTS: We extracted hemodynamic, TTE, and clinical data from Vanderbilt's deidentified electronic medical record in all patients referred for right heart catheterization between 1998 and 2014. Pulmonary hypertension (PH) was defined as mean pulmonary artery pressure ≥25 mm Hg. We examined the prevalence and clinical correlates of PH in patients without a reported TRV. We identified 1262 patients with a TTE within 2 days of right heart catheterization. In total, 803/1262 (64%) had a reported TRV, whereas 459 (36%) had no reported TRV. Invasively confirmed PH was present in 47% of patients without a reported TRV versus 68% in those with a reported TRV (P<0.001). Absence of a TRV yielded a negative predictive value for excluding PH of 53%. Right ventricular dysfunction, left atrial dimension, elevated body mass index, higher brain natriuretic peptide, diabetes mellitus, and heart failure were independently associated with PH among patients without a reported TRV. CONCLUSIONS: PH is present in almost half of patients without a measurable TRV who are referred for both TTE and right heart catheterization. Clinical and echocardiographic features of left heart disease are associated with invasively confirmed PH in subjects without a reported TRV. Clinicians should use caution when making assumptions about PH status in the absence of a measurable TRV on TTE.

Racial differences in patients referred for right heart catheterization and risk of pulmonary hypertension.

African Americans (AA) have a higher incidence of pulmonary hypertension (PH) risk factors. Few studies have examined the racial differences in the prevalence and etiology of PH and direct comparison of invasive hemodynamics between AAs and Caucasians has rarely been reported. In this study, we examined whether racial differences exist in patients referred for right heart catheterization (RHC) and hypothesized that AA race is an independent risk factor for PH and is associated with increased adjusted mortality. We extracted data for AA and Caucasian patients who underwent RHC at Vanderbilt between 1998 and 2014. Clinical information was obtained from Vanderbilt's Synthetic Derivative, a de-identified mirror of our Electronic Medical Record. A total of 4576 patients were analyzed, including 586 (13%) AAs and 3990 (87%) Caucasians. AAs were younger than Caucasians by an average of eight years, but had more prevalent heart failure, features of metabolic syndrome, and higher creatinine. AAs also had higher mean pulmonary artery pressure and pulmonary vascular resistance. After adjusting for relevant co-morbidities, the AA race is associated with 41% increased risk of PH (odds ratio [OR] = 1.41, 95% confidence interval [CI] = 1.12-1.79). Among patients with PH, AA race is associated with 24% increased adjusted mortality (hazard ratio [HR] = 1.24, 95% CI = 1.09-1.45). AAs were younger but had more prevalent cardiometabolic and renal disease and worse pulmonary hemodynamics. The AA race is an independent risk factor for PH. Among patients with PH, the AA race is associated with increased adjusted mortality. Future studies should focus on delineating whether genetic or environmental factors contribute to PH risk in AAs.

Pulmonary hypertension in patients with chronic kidney disease: invasive hemodynamic etiology and outcomes.

Pulmonary hypertension (PH) is common in patients with chronic kidney disease (CKD) and associated with increased mortality but the hemodynamic profiles, clinical risk factors, and outcomes have not been well characterized. Our objective was to define the hemodynamic profile and related risk factors for PH in CKD patients. We extracted clinical and hemodynamic data from Vanderbilt's de-identified electronic medical record on all patients undergoing right heart catheterization during 1998-2014. CKD (stages III-V) was defined by estimated glomerular filtration rate thresholds. PH was defined as mean pulmonary pressure ≥ 25 mmHg and categorized into pre-capillary and post-capillary according to consensus recommendations. In total, 4635 patients underwent catheterization: 1873 (40%) had CKD; 1518 (33%) stage 3, 230 (5%) stage 4, and 125 (3%) stage 5. PH was present in 1267 (68%) of these patients. Post-capillary (n = 965, 76%) was the predominant PH phenotype among CKD patients versus 302 (24%) for pre-capillary ( P < 0.001). CKD was independently associated with pulmonary hypertension (odds ratio = 1.4, 95% confidence interval = 1.18-1.65). Mortality among CKD patients rose with worsening stage and was significantly increased by PH status. PH is common and independently associated with mortality among CKD patients referred for right heart catheterization. Post-capillary was the most common etiology of PH. These data suggest that PH is an important prognostic co-morbidity among CKD patients and that CKD itself may have a role in the development of pulmonary vascular disease in some patients.