Increased aortic pulse and fractional pulse pressures in patients with cardiac syndrome X

Deep-learning-based real-time individualization for reduce-order haemodynamic model

The reduced-order lumped parameter model (LPM) has great computational efficiency in real-time numerical simulations of haemodynamics but is limited by the accuracy of patient-specific computation. This study proposed a method to achieve the individual LPM modeling with high accuracy to improve the practical clinical applicability of LPM. Clinical data was collected from two medical centres comprising haemodynamic indicators from 323 individuals, including brachial artery pressure waveforms, cardiac output data, and internal carotid artery flow waveforms. The data were expanded to 5000 synthesised cases that all fell within the physiological range of each indicator. LPM of the human blood circulation system was established. A double-path neural network (DPNN) was designed to input the waveforms of each haemodynamic indicator and their key features and then output the individual parameters of the LPM, which was labelled using a conventional optimization algorithm. Clinically collected data from the other 100 cases were used as the test set to verify the accuracy of the individual LPM parameters predicted by DPNN. The results show that DPNN provided good convergence in the training process. In the test set, compared with clinical measurements, the mean differences between each haemodynamic indicator and the estimate calculated by the individual LPM based on the DPNN were about 10 %. Furthermore, DPNN prediction only takes 4 s for 100 cases. The DPNN proposed in this study permits real-time and accurate individualization of LPM's. When facing medical issues involving haemodynamics, it lays the foundation for patient-specific numerical simulation, which may be beneficial for potential clinical application.

A real-time patient-specific treatment strategy for enhanced external counterpulsation

Diastolic/systolic blood pressure ratio (D/S) ≥ 1.2 is the gold standard of enhanced external counterpulsation (EECP) treatment, but it does not show a clear clinical correspondence with the configuration of the EECP mode. As such, a single target results in different treatment effects in different individuals. The local haemodynamic effect (wall shear stress, WSS) of EECP on vascular endothelial cells is conducive to promote the growth of collateral circulation vessels and restore the blood supply distal to the stenosis lesion. Considering the haemodynamic effects of WSS on human arteries, this study developed a real-time patient-specific treatment strategy of EECP for patients with cardio-cerebrovascular diseases. Based on patient-specific haemodynamic data from 113 individuals, an optimization algorithm was developed to achieve the individualization of a 0D lumped-parameter model of the human circulatory system, thereby simulating the patient-specific global haemodynamic effects. 0D/3D coupled cardio-cerebrovascular models of two subjects were established to simulate the local WSS. We then established statistical models to evaluate clinically unmeasurable WSS based on measurable global haemodynamic indicators. With the aim of attaining appropriate area- and time-averaged WSS (ATAWSS, 4-7 Pa), as evaluated by global haemodynamic indicators, a closed-loop feedback tuning method was developed to provide patient-specific EECP treatment strategies. Results showed that for clinical data collected from 113 individuals, the individualized 0D model can accurately simulate patient-specific global haemodynamic effects (average error <5%). Based on two subjects, the statistical models can be used to evaluate local ATAWSS (error <6%) for coronary arteries and for cerebral arteries. An EECP mode planned by the patient-specific treatment strategy can promote an appropriate ATAWSS within a 16 s calculation time. The real-time patient-specific treatment strategy of EECP is expected to improve the long-term outcome for each patient and have potential clinical significance.

Definitions and incidence of cardiac syndrome X: review and analysis of clinical data

There is no consensus regarding the definition of cardiac syndrome X (CSX). We systematically reviewed recent literature using a standardized search strategy. We included 57 articles. A total of 47 studies mentioned a male/female distribution. A meta-analysis yielded a pooled proportion of females of 0.56 (n = 1,934 patients, with 95% confidence interval: 0.54-0.59). As much as 9 inclusion criteria and 43 exclusion criteria were found in the 57 articles. Applying these criteria to a population with normal coronary angiograms and treated in 1 year at a general hospital, the attributable CSX incidence varied between 3 and 11%. The many inclusion and exclusion criteria result in a wide range of definitions of CSX and these have large effects on the incidence. This shows the need for a generally accepted definition of CSX.

Effect of aortic pulse and fractional pulse pressures on early patency of sapheneous vein grafts

BACKGROUND

Coronary artery bypass grafting has a mortality benefit compared to medical therapy in some patient groups, such as those with left main or left anterior descending coronary artery disease, and those with left ventricular dysfunction. Therefore, patency of grafts, especially sapheneous grafts, is an important issue. Aortic pulse and fractional pulse pressures are strong and independent indicators of the risk of atherosclerosis. We studied whether there was any negative effect of increased aortic pulse and fractional pulse pressures on saphenous vein graft (SVG) patency in the short term.

METHODS

We evaluated aortic pulse and fractional pulse pressures of patients with occluded and patent SVGs, and investigated the relation between the two groups. One hundred and twenty-six patients with occluded SVGs with a mean age of 65.9+/-8.9 years and 114 patients with patent SVGs with a mean age of 66.9+/-8.6 years were studied consecutively. Aortic systolic and diastolic pressures were measured, and mean, pulse, and fractional pulse pressures (aortic pulse pressure/mean pressure) were calculated.

RESULTS

Aortic pulse and fractional pulse pressures were significantly higher in the occluded SVG group than in the patent SVG group (58+/-19 and 48+/-13 mmHg, P=0.001; 0.59+/-0.16 and 0.50+/-0.10, P<0.001, respectively). In addition, a cut-off value of 50 mmHg and 0.52 for aortic pulse and fractional pulse pressures were determined, respectively. Increased aortic pulse (>50 mmHg) and fractional pulse (>0.52) pressures were present in 54.0 and 58.7% of patients in group 1 and 28.1 and 33.3% of patients in group 2, respectively (P=0.004 and P=0.005, respectively). Having increased aortic pulse and fractional pulse pressures increased the risk of SVG occlusion by 3.00 and 2.85-folds, respectively. The multiple-adjusted odds ratio of the risk of SVG occlusion was 6.86 (95% confidence interval 2.14-21.96) and 4.76 (95% confidence interval 1.58-14.30) for the higher aortic pulse and fractional pulse pressure levels compared with lower levels, respectively.

CONCLUSION

Increased ascending aorta pulse and fractional pulse pressures have a significant and independent negative effect on the fate of SVGs.