Cardiac implications of upper-arm arteriovenous fistulas: A case series

Background: Cardiovascular disease is a major cause of morbidity and mortality in patients with end-stage kidney disease. Arterio-venous fistulas (AVF), the gold standard for hemodialysis vascular access, are known to alter cardiac morphology and circulatory hemodynamics. We present a prospective case series of patients after creation of an AVF, explore the timeline for changes in their cardiac morphology, and detail considerations for clinicians. Methods: Patients were recruited in 2010 at multiple centers immediately prior to the creation of an upper-arm AVF and the initiation of hemodialysis. Cardiovascular magnetic resonance images were taken at intake before the creation of the AVF, 6-month follow-up, and 12-month follow-up. Image segmentation was used to measure left ventricular volume and mass, left atrial volume, and ejection fraction. Results: Eight patients met eligibility criteria. All eight patients had a net increase in left ventricular mass over enrollment, with a mean increase of 9.16 g (+2.96 to +42.66 g). Five participants had a net decrease in ejection fraction, with a mean change in ejection fraction of −5.4% (−21% to +5%). Upon visual inspection the patients with the largest ejection fraction decrease had noticeably hypertrophic and dilated ventricles. Left atrial volume change was varied, decreasing in five participants, while increasing in three participants. Changes in morphology were present at 6-month follow-up, even in patients who did not maintain AVF patency for the entirety of the 6-month period. Conclusion: All patients included in this prospective case series had increases in left ventricular mass, with variability in the effects on the ejection fraction and left atrial volume. As left ventricular mass is an independent predictor of morbidity and mortality, further research to determine appropriate vascular access management in both end-stage kidney disease and kidney transplant populations is warranted.

Artificial Intelligence-Based Echocardiographic Left Atrial Volume Measurement with Pulmonary Vein Comparison

This paper combines echocardiographic signal processing and artificial intelligence technology to propose a deep neural network model adapted to echocardiographic signals to achieve left atrial volume measurement and automatic assessment of pulmonary veins efficiently and quickly. Based on the echocardiographic signal generation mechanism and detection method, an experimental scheme for the echocardiographic signal acquisition was designed. The echocardiographic signal data of healthy subjects were measured in four different experimental states, and a database of left atrial volume measurements and pulmonary veins was constructed. Combining the correspondence between ECG signals and echocardiographic signals in the time domain, a series of preprocessing such as denoising, feature point localization, and segmentation of the cardiac cycle was realized by wavelet transform and threshold method to complete the data collection. This paper proposes a comparative model based on artificial intelligence, adapts to the characteristics of one-dimensional time-series echocardiographic signals, automatically extracts the deep features of echocardiographic signals, effectively reduces the subjective influence of manual feature selection, and realizes the automatic classification and evaluation of human left atrial volume measurement and pulmonary veins under different states. The experimental results show that the proposed BP neural network model has good adaptability and classification performance in the tasks of LV volume measurement and pulmonary vein automatic classification evaluation and achieves an average test accuracy of over 96.58%. The average root-mean-square error percentage of signal compression is only 0.65% by extracting the coding features of the original echocardiographic signal through the convolutional autoencoder, which completes the signal compression with low loss. Comparing the training time and classification accuracy of the LSTM network with the original signal and encoded features, the experimental results show that the AI model can greatly reduce the model training time cost and achieve an average accuracy of 97.97% in the test set and increase the real-time performance of the left atrial volume measurement and pulmonary vein evaluation as well as the security of the data transmission process, which is very important for the comparison of left atrial volume measurement and pulmonary vein. It is of great practical importance to compare left atrial volume measurements with pulmonary veins.

227 Myocardial work evaluation in severe aortic stenosis undergoing transcatheter aortic valve implantation

Aims Myocardial work (MW) is a novel echocardiographic technique which assesses left ventricular (LV) performance through LV pressure-strain loops. MW corrects speckle tracking echocardiography (STE)-derived parameters for afterload using non-invasive systolic blood pressure (SBP) as a surrogate for LV systolic pressure. In patients with severe aortic stenosis (AS), the corrected MW (cMW) has been proposed, consisting in adding the mean aortic gradient in SBP. This method revealed to be feasible and reliable, demonstrating good correlation with invasively measured LV systolic pressure. To evaluate myocardial performance of patients with severe AS, before and after transcatheter aortic valve implantation (TAVI), by MW indices. Methods patients with severe AS undergoing TAVI were included. Transthoracic, standard echocardiography and STE were performed the day before the procedure and within 2 days after. MW was calculated by combining STE-derived indices with non-invasively estimated LV systolic pressure. Results 30 patients (79±5 years old, 56% females) with severe AS (mean gradient 47±14 mmHg, aortic valve area 0.6±0.1 cm2), and eligible for TAVI were enrolled. Baseline global longitudinal strain was impaired (GLS −15±4%), in presence of normal LV ejection fraction (LVEF 57±10%). Corrected global work index and global constructive work were preserved at baseline and markedly decreased after TAVI (cGWI 2322±791 vs. 1710±505 mmHg%, P=0.001; cGCW 2774±803 vs. 2083±536 mmHg%, P=0.0007). Corrected global wasted work and global work efficiency were respectively higher and lower than reference values existing in literature, and no significant changes were observed after TAVI (cGWW 276±174 vs. 277±165 mmHg%, P=0.974; cGWE 89±5 vs. 87±5%, P=0.177). A significant inverse correlation was found between baseline cGWI and left atrial volume index (r = −0.5, P=0.03). Conclusions Patients with severe aortic stenosis and preserved LVEF show a good LV performance before and after TAVI, with a significant decrease in MW indices after TAVI, because of the reduced afterload due to AS treatment. The negative correlation between left atrial volume and cGWI may reflect the extent of myocardial damage in AS. However, further studies with larger sample size and appropriate follow-up are needed to evaluate the role of MW in prognosis and risk stratification of this subset of patients.

Left Atrial Volume Correlates with Mitral Annulus Size: An MDCT Study

Aim: Although the association between left ventricular dilation and mitral annulus dilation is well understood, the potential variation in the size of the mitral annulus during dilation of the left atrium is currently unknown. In order to investigate the link between the two variables, we used multidetector computed tomography (MDCT) and looked at patients who had a dilated left atrium, assessing if the mitral valve also dilates. Materials and Methods: The study included 107 patients with paroxysmal and persistent atrial fibrillation, in whom catheter ablation was performed using pulmonary vein isolation ± atrial substrate modification. Eighty patients were male (74.8%), with a mean age of 55.8 years (±9.87 with a minimum age of 26 years and a maximum age of 79 years), of which 57.1% had paroxysmal AF and the rest had persistent fibrillation. All the patients underwent multiple-detector CT (MDCT) with contrast medium before the ablation. CT images were integrated into the three-dimensional mapping system CARTO 3, after which the diameters of the mitral annulus, area, and circumference were measured. Left atrial size was evaluated by measuring the diameters, area, and volume. Results: The left atrial area was 247 ± 65.7 cm2 and the left atrial volume was 139 ± 56.3 mL. The transverse mitral annulus (MA) was 29.9 ± 5.3 mm and the longitudinal diameter was 41.9 ± 7.6 mm. The MA circumference and area were 15.0 ± 3.5 cm and 14.2 ± 4.6 cm2, respectively. The following statistically significant correlation was identified between the dimensions of the mitral annulus and the diameters of the left atrium: the transverse mitral annulus correlates with the antero-posterior (AP) LA diameter (R = 0.594, p < 0.01) and the longitudinal MA diameter correlates with the latero-lateral (LL) LA diameter (R = 0.576, p < 0.01). Furthermore, the MA area correlates with the LA volume (R = 0.639, p < 0.001). Conclusions: The volume of the left atrium correlates with the area of the mitral annulus. In patients with paroxysmal and persistent AF, an increase in left atrial dimensions is further associated with an increase in mitral valve dimensions.

Atri-U: assisted image analysis in routine cardiovascular magnetic resonance volumetry of the left atrium

Background Artificial intelligence can assist in cardiac image interpretation. Here, we achieved a substantial reduction in time required to read a cardiovascular magnetic resonance (CMR) study to estimate left atrial volume without compromising accuracy or reliability. Rather than deploying a fully automatic black-box, we propose to incorporate the automated LA volumetry into a human-centric interactive image-analysis process. Methods and results Atri-U, an automated data analysis pipeline for long-axis cardiac cine images, computes the atrial volume by: (i) detecting the end-systolic frame, (ii) outlining the endocardial borders of the LA, (iii) localizing the mitral annular hinge points and constructing the longitudinal atrial diameters, equivalent to the usual workup done by clinicians. In every step human interaction is possible, such that the results provided by the algorithm can be accepted, corrected, or re-done from scratch. Atri-U was trained and evaluated retrospectively on a sample of 300 patients and then applied to a consecutive clinical sample of 150 patients with various heart conditions. The agreement of the indexed LA volume between Atri-U and two experts was similar to the inter-rater agreement between clinicians (average overestimation of 0.8 mL/m2 with upper and lower limits of agreement of − 7.5 and 5.8 mL/m2, respectively). An expert cardiologist blinded to the origin of the annotations rated the outputs produced by Atri-U as acceptable in 97% of cases for step (i), 94% for step (ii) and 95% for step (iii), which was slightly lower than the acceptance rate of the outputs produced by a human expert radiologist in the same cases (92%, 100% and 100%, respectively). The assistance of Atri-U lead to an expected reduction in reading time of 66%—from 105 to 34 s, in our in-house clinical setting. Conclusions Our proposal enables automated calculation of the maximum LA volume approaching human accuracy and precision. The optional user interaction is possible at each processing step. As such, the assisted process sped up the routine CMR workflow by providing accurate, precise, and validated measurement results.

Left Atrial Volume Index Predicts Future Improvement of B-Type Natriuretic Peptide Levels After Transcatheter Aortic Valve Replacement

Background: In patients with symptomatic severe aortic stenosis (AS), those who experienced readmission due to heart failure after transcatheter aortic valve replacement (TAVR) showed poor prognosis. Furthermore, poor BNP improvement is associated with increased morbidity and mortality. However, little is known about the clinical parameters related to the change in BNP levels after TAVR procedure.Methods and Results: This study population consisted of 127 consecutive patients of symptomatic severe AS with preserved ejection fraction (EF) who underwent TF-TAVR. The median BNP level was significantly decreased from 252.5 pg/ml to 146.8 pg/ml in all 127 patients 1 year after TF-TAVR (P<0.01). However, the patients could be divided into 2 groups according to decrease (72%) or increase (28%) in plasma BNP level. Multivariate logistic regression analysis revealed that AV peak velocity, pre-procedural BNP, and larger left atrial volume index (LAVI) were found to be an independent predictor of increased BNP level 1 year after TAVR (OR 0.55, 95% CI 0.38-0.77; p<0.01). LAVI were negatively correlated with the change in BNP level before and 1 year after TAVR (r=0.47, P<0.01). The ROC analysis demonstrated that 52.9ml/m2 was the optimal cut-off value of LAVI for decreasing BNP 1 year after TAVR (area under the curve 0.69) with 64% sensitivity and 70% specificity.Conclusions: In addition to AV peak velocity and pre-procedural BNP, LAVI independently predicts future improvement of BNP levels 1 year after TAVR. Our findings indicate an additive predictive value of assessment of LAVI before TAVR procedure for risk stratification.