Cardiac Pulse Research Articles

Numerical analysis of biothermal-fluids and cardiac thermal pulse of abdominal aortic aneurysm.

Abdominal aortic aneurysms are serious and difficult to detect, conditions can be deadly if they rupture. In this study, the heat transfer and flow physics of Abdominal Aortic Aneurysm (AAA) were discussed and associated with cardiac cycle to illustrate the cardiac thermal pulse (CTP) of AAA. A CTP and infrared thermography (IRT) evaluation-based on AAA and abdomen skin surface detection method was proposed, respectively. Infrared thermography (IRT) is a promising imaging technique that may detect AAA quicker and cheaper than other imaging techniques (as biomarker). From CFD rigid-wall and FSI Analysis, the transient bioheat transfer effect resulted in a distinct thermal signature (circular thermal elevation) on the temperature profile of midriff skin surface, at both regular body temperature and supine position, under normal clinical temperature. However, it is important to note that thermography is not a perfect technology, and it does have some limitations, such as lack of clinical trials. There is still work to be done to improve this imaging technique and make it a more viable and accurate method for detecting abdominal aortic aneurysms. However, thermography is currently one of the most convenient technologies in this field, and it has the potential to detect abdominal aortic aneurysms earlier than other techniques. CTP, on the other hand, was used to examine the thermal physics of AAA. In CFD rigid-wall Analysis, AAA had a CTP that only responded to systolic phase at regular body temperature. In contrast, a healthy abdominal aorta displayed a CTP that responded to the full cardiac cycle, including diastolic phase at all simulated cases. Besides, the findings from FSI Analysis suggest the influence of numerical simulation techniques on the prediction of thermal physics behaviours of AAA and abdominal skin surface. Lastly, this study correlated the relationship between natural convective heat transfer coefficient with AAA and provided reference for potential clinical diagnostic using IRT in clinical implications.

Evaluation of Cardiac- and Respiratory-driven Cerebrospinal Fluid Motions by Applying the S-transform to Steady-state Free Precession Phase Contrast Imaging.

To extract the status of hydrocephalus and other cerebrospinal fluid (CSF)-related diseases, a technique to characterize the cardiac- and respiratory-driven CSF motions separately under free breathing was developed. This technique is based on steady-state free precession phase contrast (SSFP-PC) imaging in combination with a Stockwell transform (S-transform). 2D SSFP-PC at 3 T was applied to measure the CSF velocity in the caudal-cranial direction within a sagittal slice at the midline (N = 3) under 6-, 10-, and 16-s respiratory cycles and free breathing. The frequency-dependent window width of the S-transform was controlled by a particular scaling factor, which then converted the CSF velocity waveform into a spectrogram. Based on the frequency bands of the cardiac pulsation and respiration, as determined by the electrocardiogram (ECG) and respirator pressure sensors, Gaussian bandpass filters were applied to the CSF spectrogram to extract the time-domain cardiac- and respiratory-driven waveforms. The cardiac-driven CSF velocity component appeared in the spectrogram clearly under all respiratory conditions. The respiratory-driven velocity under the controlled respiratory cycles was observed as constant frequency signals, compared to a time-varying frequency signal under free breathing. When the widow width was optimized using the scale factor, the temporal change in the respiratory-driven CSF component was even more apparent under free breathing. Velocity amplitude variations and transient frequency changes of both cardiac- and respiratory-driven components were successfully characterized. These findings indicated that the proposed technique is useful for evaluating CSF motions driven by different cyclic forces.

161 Biosensor in cardiology. T-care project: a preliminary study on innovative wearable non-invasive telemonitoring system

Abstract The demographic trend evolution and the modification of health needs highlight the requirement for a novel organization of the healthcare system. Telemedicine is a technological tool that allows a knockdown of geographic barriers being useful in the management of remote patient assistance. Telemedicine is roughly applied in different cardiology’s areas, from telemetric to implantable devices (loop recorders) in order to monitor cardiac rate, cardiac rhythm variations, and the onset of arrhythmic events. The aim of the present study is to assess the validity of wearable devices (T-shirt equipped with biosensors and bands with photopletimographic system) in monitoring EKG, cardiac rate, and pulse oximetry. We enrolled 38 patients, 25 of whom admitted to the Cardiology Unit, University of Bari. Main characteristics of the sample are listed in Table 1. The difference between traditional monitoring system and wearable biosensors in not statistically significant as shown in Figure 1; therefore the devices tested in this study show a satisfying level of reliability in monitoring cardiac rate, pulse oximetry, QT interval, QRS complexes, and onset of arrhythmic events. However, alerts produced by arrhythmias different from atrial fibrillation are not completely reliable; moreover, the software and the diagnostic algorithm need to be optimized for motion artefacts. For these reasons, results need to be reproduced on a large cohort of patients.

Dancing swan in left hemithorax

A 67-yrs-old, diabatic,hypertensive individual was admitted for multivessel coronary artery bypass graft surgery . Off-Pump CABG was performed using Left Internal Thoracic Artery to Left Anterior Descending Artery, left radial artery to first Obtuse Marginal branch, and reversed saphenous vein graft to Posterior Descending Artery as conduits. His total chest drainage was 430 ml. His was discharged on 8th postoperative day. He was brought to emergency treatment unit on 28th postoperative day with cough and dyspoea.On examination he was dyspnoic, oxygen saturation was 88% on room air. Point of care Transthoracic Echocardiogram demonstrated “dancing swan in left hemi thorax” . (VIDEO). The TTE which included lung ultrasonography, showed left sided heterogeneously anechoic effusion with partial thin septation & floating echoes. The partially collapsed left lower lobe dances during each cardiac pulsation due to propagation of a waveform across this moderate effusion. Exudate effusions often demonstrate punctate, hyper echoic foci floating within the effusion, referred to as Plankton sign. Intercostal drain was inserted on left side and 1.8 liters of hemorrhagic fluid was drained, total chest drainage was 2.4 liters.

Associations in Alzheimer’s disease between intracranial vascular metrics from 4D‐flow MRI and β‐amyloid and tau PET

AbstractBackgroundCerebrovascular disease (CVD), has been linked with dementia stages of Alzheimer’s disease (AD); however, the question of whether CVD is associated with underlying AD pathophysiology remains unresolved. This work investigated the relationship between advanced MRI based cerebrovascular markers with AD biomarkers of β‐amyloid deposition and neurofibrillary tau tangles in subjects spanning the AD clinical spectrum.MethodSubjects: Study groups are summarized in figure 1. MRI: Whole brain 4D‐Flow data were acquired on a 3.0T system using a 32‐channel head coil. From 4D‐Flow images, intracranial blood flow, trans‐capillary pulse wave delay, and low frequency oscillations (LFOs) were estimated. Trans‐capillary pulse wave delay was defined as the cardiac pulse wave transit time from intracranial arteries‐to‐capillaries‐to‐veins and was measured from cardiac wave time‐to‐upstroke differences in arteries and veins. White matter hyperintensity (WMH) lesion volumes were segmented from T2‐FLAIR images using the Lesion Segmentation Toolbox in SPM12. PET: Four groups were established based on clinical diagnosis and biomarker positivity. Subjects were classified as cognitively normal (CN) or impaired (IM) (MCI or dementia) based on a clinical consensus review. Amyloid (A) (+/‐) was determined using a previously established global PiB DVR threshold >1.19 and tau (T) (+/‐) was determined using a previously established entorhinal cortex MK‐6240 SUVR threshold >1.27. Pairwise statistical differences were assessed using ANOVA followed by post‐hoc analysis (P<0.05 significance).ResultTrans‐capillary pulse wave delay was significantly longer in controls (A‐/T‐/CN) when compared with AD biomarker confirmed groups (fig 2 b) (P<0.001). Low frequency flow range and LFOs were significantly lower and diminished in A+T+ groups both cognitively normal and impaired (fig 3 P<0.001; fig 4 P=0.027, P=0.046, P=0.046). Linear regression analysis showed a weak correlation between trans‐capillary pulse wave delay and PiB and MK‐6240 (R2=0.12, R2=0.04), and between LFOs and PiB and MK‐6240 (R2=0.07, R2=0.03) (fig 5). No significant AT biomarker group differences were observed across other modalities such as traditional cardiovascular and cerebrovascular metrics, including WMH lesion volumes (fig 1).ConclusionAlthough more traditional measures of CVD were not related to biomarker groups, 4D‐Flow MRI based vascular markers suggest significant intracranial vascular stiffness and reduced autoregulation‐related vasomotion in AD biomarker positive subjects during preclinical AD.

Functional imaging of human retina using integrated multispectral and laser speckle contrast imaging.

A novel integration of retinal multispectral imaging (MSI), retinal oximetry and laser speckle contrast imaging (LSCI) is presented for functional imaging of retinal blood vessels that could potentially allow early detection or monitoring of functional changes. We designed and built a cost-effective, scalable, retinal imaging instrument that integrates structural and functional retinal imaging techniques, including MSI, retinal oximetry and LSCI. Color fundus imaging was performed with 470 nm, 550 nm and 600 nm wavelength light emitting diode (LED) illumination. Retinal oximetry was performed using 550 nm and 600 nm LED illumination. LSCI of blood flow was performed using 850 nm laser diode illumination at 82 frames per second. LSCI can visualize retinal and choroidal vasculature without requiring exogenous contrast agents and can provide time-resolved information on blood flow, generating a cardiac pulse waveform from retinal vasculature. The technology can rapidly acquire structural MSI images, retinal oximetry and LSCI blood flow information in a simplified clinical workflow without requiring patients to move between instruments. Results from multiple modalities can be combined and registered to provide structural as well as functional information on the retina. These advances can reduce barriers for clinical adoption, accelerating research using MSI, retinal oximetry and LSCI of blood flow for diagnosis, monitoring and elucidating disease pathogenesis.

Abstract 12136: Detection of Sub-Clinical Left Ventricular Dysfunction in COVID-19 Patients

Introduction: Abnormalities of left ventricular (LV) strain have been shown to occur prior to impairment of global left ventricular function, measured by global LV ejection fraction (EF). Although first described in patients receiving cardiotoxic chemotherapy, impairment of LV strain prior to a decrease in EF has also been shown in many other disease states which affect LV function. This study was designed to assess impairment of LV strain in post COVID-19 patients with normal EF using cardiac MRI MyoStrain Fast-SENC (strain encoded) pulse sequences. Methods: An institutional cardiac imaging database was queried for all patients with documented COVID-19 test positivity and a normal LVEF >= 55% who underwent measurement of global longitudinal strain (GLS), global circumferential strain (GCS), and regional longitudinal and circumferential strain using cardiac MRI Fast-SENC pulse sequences. Global and regional strain measurements were compared to a cohort of healthy volunteers who also underwent CMR Fast-SENC imaging. Abnormal myocardial strain was defined as a value >-17%. Results: Of 50 COVID-19 patients in the cardiac imaging database who underwent CMR Fast-SENC imaging, 40 had a normal LVEF, constituting the study cohort. Mean GLS and GCS for the study cohort were -16.40% and -15.45% and for healthy volunteers were -19.71% and -20.93% respectively; both comparisons were statistically significant with an unpaired t-test (p<0.01). Furthermore, the prevalence of abnormal LV strain in COVID-19 patients with normal LVEF was 77.78%. Conclusions: These data suggest that impairment of LV strain (longitudinal and circumferential) occurs in COVID-19 patients who have a normal LVEF. Whether a decrease in GLS and/or GCS precede a decrease in LVEF, is beyond the scope of this study. However, the ability to evaluate progression of LV strain abnormalities with CMR may help identify changes in LV function before the onset of a reduction in LVEF and development of heart failure. The ability to identify and quantify abnormal left ventricular GLS and GCS with cardiac MRI also opens the door to assess any benefit of therapy, including anti-inflammatory agents, anti-viral drugs and steroids.

An ICA Investigation into the Effect of Physiological Noise Correction on Dimensionality and Spatial Maps of Intrinsic Connectivity Networks.

Physiological processes such as cardiac pulsations and respiration can induce signal modulations in functional magnetic resonance imaging (fMRI) time series, and confound inferences made about neural processing from analyses of the blood oxygenation level-dependent (BOLD) signals. Retrospective image space correction of physiological noise (RETROICOR) is a widely used approach to reduce physiological signals in data. Independent component analysis (ICA) is a valuable blind source separation method for analyzing brain networks, referred to as intrinsic connectivity networks (ICNs). Previously, we showed that temporal properties of the ICA-derived networks such as spectral power and functional network connectivity could be impacted by RETROICOR corrections. The goal of this study is to investigate the effect of retrospective correction of physiological artifacts on the ICA dimensionality (model order) and intensities of ICN spatial maps. To this aim, brain BOLD fMRI, heartbeat, and respiration were measured in 22 healthy subjects during resting state. ICA dimensionality was estimated using minimum description length (MDL) based on i.i.d. data samples and smoothness FWHM kernel, and entropy-rate based order selection by finite memory length model (ER-FM) and autoregressive model (ER-AR). Differences in spatial maps between the raw and denoised data were compared using the paired t-test and false discovery rate (FDR) thresholding was used to correct for multiple comparisons. Results showed that ICA dimensionality was greater in the raw data compared to the denoised data. Significant differences were found in the intensities of spatial maps for three ICNs: basal ganglia, precuneus, and frontal network. These preliminary results indicate that the retrospective physiological noise correction can induce change in the resting state spatial map intensity related to the within-network connectivity. More research is needed to understand this effect.

Tachycardia and hypertension enhance tracer efflux from the spinal cord

BackgroundDisruption of cerebrospinal fluid (CSF)/interstitial fluid (ISF) exchange in the spinal cord is likely to contribute to central nervous system (CNS) diseases that involve abnormal fluid accumulation, including spinal cord oedema and syringomyelia. However, the physiological factors that govern fluid transport in the spinal cord are poorly understood. The aims of this study were to determine the effects of cardiac pulsations and respiration on tracer signal increase, indicative of molecular movement following infusion into the spinal cord grey or white matter.MethodsIn Sprague Dawley rats, physiological parameters were manipulated such that the effects of spontaneous breathing (generating alternating positive and negative intrathoracic pressures), mechanical ventilation (positive intrathoracic pressure only), tachycardia (heart atrial pacing), as well as hypertension (pharmacologically induced) were separately studied. Since fluid outflow from the spinal cord cannot be directly measured, we assessed the molecular movement of fluorescent ovalbumin (AFO-647), visualised by an increase in tracer signal, following injection into the cervicothoracic spinal grey or white matter.ResultsTachycardia and hypertension increased AFO-647 tracer efflux, while the concomitant negative and positive intrathoracic pressures generated during spontaneous breathing did not when compared to the positive-pressure ventilated controls. Following AFO-647 tracer injection into the spinal grey matter, increasing blood pressure and heart rate resulted in increased tracer movement away from the injection site compared to the hypotensive, bradycardic animals (hypertension: p = 0.05, tachycardia: p < 0.0001). Similarly, hypertension and tachycardia produced greater movement of AFO-647 tracer longitudinally along the spinal cord following injection into the spinal white matter (p < 0.0001 and p = 0.002, respectively). Tracer efflux was strongly associated with all blood vessel types.ConclusionsArterial pulsations have profound effects on spinal cord interstitial fluid homeostasis, generating greater tracer efflux than intrathoracic pressure changes that occur over the respiratory cycle, demonstrated by increased craniocaudal CSF tracer movement in the spinal cord parenchyma.

Insufficient sampling frequencies skew heart rate variability estimates: Implications for extracting heart rate metrics from neuroimaging and physiological data

BackgroundWhile cardiac pulsations are widely present within physiological and neuroimaging data, it is unknown the extent this information can provide valid and reliable heart rate and heart rate variability (HRV) estimates. The objective of this study was to demonstrate how a slight temporal shift due to an insufficient sampling frequency can impact the validity/accuracy of deriving cardiac metrics. MethodsTwenty-two participants were instrumented with valid/reliable industry-standard or open-source electrocardiograms. Five-minute lead II recordings were collected at 1000 Hz in an upright orthostatic position. Following artifact removal, the 1000 Hz recording for each participant was downsampled to frequencies ranging 2–500 Hz. The validity of each participant’s downsampled recording was compared against their 1000 Hz recording (“reference-standard”) using Bland-Altman plots with 95 % limits of agreement (LOA), coefficient of variation (CoV), intraclass correlation coefficients, and adjusted r-squared values. ResultsDownsampled frequencies of ≥ 50 and ≥ 90 Hz produced highly robust measures with narrow log-transformed 95 % LOA (<±0.01) and low CoV values (≤3.5 %) for heart rate and HRV metrics, respectively. Below these thresholds, the log-transformed 95 % LOA became wider (LOA range: ±0.1–1.9) and more variable (CoV range: 1.5–111.6 %). ConclusionThese results provide an important consideration for obtaining cardiac information from physiological data. Compared to the “reference-standard” ECG, a seemingly negligible temporal shift of the systolic contraction (R wave) greater than 11-milliseconds (90 Hz) away from its true value, lessened the validity of the HRV. Further research is warranted to determine the minimum sampling frequency required to obtain valid heart rate/HRV metrics from pulsatile waveforms.

Battery‐Less Power Management Circuit Powered by a Wearable Piezoelectric Energy Harvester

A system that aims to manage the energy harvested from the finger movement using a glove‐type garment is proposed. For this, five polyvinylidene difluoride (PVDF) film‐type sensors are mounted on different interphalangeal joints of the fingers. A 68 μF/25 V ceramic capacitor is used as a storage device. A battery‐less power management circuit (PMC) is proposed to isolate the capacitor from the load to reduce the current consumption while charging. When the voltage across the capacitor reaches a threshold voltage, the user decides when to transfer the energy to the electronic load. To test the proposed system, the harvested and conditioned energy is used to power both the PMC and a battery‐less cardiac pulse detection circuit, achieving an autonomy of 20 s. This time depends on the voltage stored in the capacitor and the current consumption of the load. Using the proposed wearable system, it is possible to store up to 700 μJ in the capacitor when a subject manipulates a computer or a cellular phone for 10 min. The proposed system is not limited to the activities presented herein because it can harvest the biomechanical energy from any activity that involves finger movements.

Bioimpedance plethysmography with capacitive electrodes and sole force sensors: comparative trial

Foot impedance plethysmography was implemented using two types of electrodes (dry and capacitive) and sole force sensors. The latter are commonly used for assessing diabetic foot ulcers (DFU). For impedance plethysmography, a tetrapolar configuration has been used with three different plantar setups: four skin contact electrodes, four capacitive contact electrodes and two Force Sensing Resistors (FSRs). In this work, FSRs have been considered as possible capacitive electrodes because the top substrate contains interdigitating conductive electrodes and a semiconductive polymer. All the measurements have been performed using a 1 mA/10 kHz excitation current and have been tried under the feet of a standing person to detect impedance plethysmography signals. Contact electrodes allow a good cardiac pulse signal while capacitive contact through the socks features mains interferences. Force sensing resistors with their force-dependent resistance in parallel to the capacitive coupling, were not able to detect cardiac pulse. But promising results can be anticipated from these findings provided higher frequencies are used and larger sensor areas to help detect altered skin states in diabetic foot.

Brain-mimicking phantom for biomechanical validation of motion sensitive MR imaging techniques

Motion sensitive MR imaging techniques allow for the non-invasive evaluation of biological tissues by using different excitation schemes, including physiological/intrinsic motions caused by cardiac pulsation or respiration, and vibrations caused by an external actuator. The mechanical biomarkers extracted through these imaging techniques have been shown to hold diagnostic value for various neurological disorders and conditions. Amplified MRI (aMRI), a cardiac gated imaging technique, can help track and quantify low frequency intrinsic motion of the brain. As for high frequency actuation, the mechanical response of brain tissue can be measured by applying external high frequency actuation in combination with a motion sensitive MR imaging sequence called Magnetic Resonance Elastography (MRE). Due to the frequency-dependent behavior of brain mechanics, there is a need to develop brain phantom models that can mimic the broadband mechanical response of the brain in order to validate motion-sensitive MR imaging techniques. Here, we have designed a novel phantom test setup that enables both the low and high frequency responses of a brain-mimicking phantom to be captured, allowing for both aMRI and MRE imaging techniques to be applied on the same phantom model. This setup combines two different vibration sources: a pneumatic actuator, for low frequency/intrinsic motion (1 Hz) for use in aMRI, and a piezoelectric actuator for high frequency actuation (30–60 Hz) for use in MRE. Our results show that in MRE experiments performed from 30 Hz through 60 Hz, propagating shear waves attenuate faster at higher driving frequencies, consistent with results in the literature. Furthermore, actuator coupling has a substantial effect on wave amplitude, with weaker coupling causing lower amplitude wave field images, specifically shown in the top-surface shear loading configuration. For intrinsic actuation, our results indicate that aMRI linearly amplifies motion up to at least an amplification factor of 9 for instances of both visible and sub-voxel motion, validated by varying power levels of pneumatic actuation (40%–80% power) under MR, and through video analysis outside the MRI scanner room. While this investigation used a homogeneous brain-mimicking phantom, our setup can be used to study the mechanics of non-homogeneous phantom configurations with bio-interfaces in the future.

When the human brain goes diving: using near-infrared spectroscopy to measure cerebral and systemic cardiovascular responses to deep, breath-hold diving in elite freedivers.

Continuous measurements of haemodynamic and oxygenation changes in free living animals remain elusive. However, developments in biomedical technologies may help to fill this knowledge gap. One such technology is continuous-wave near-infrared spectroscopy (CW-NIRS)-a wearable and non-invasive optical technology. Here, we develop a marinized CW-NIRS system and deploy it on elite competition freedivers to test its capacity to function during deep freediving to 107 m depth. We use the oxyhaemoglobin and deoxyhaemoglobin concentration changes measured with CW-NIRS to monitor cerebral haemodynamic changes and oxygenation, arterial saturation and heart rate. Furthermore, using concentration changes in oxyhaemoglobin engendered by cardiac pulsation, we demonstrate the ability to conduct additional feature exploration of cardiac-dependent haemodynamic changes. Freedivers showed cerebral haemodynamic changes characteristic of apnoeic diving, while some divers also showed considerable elevations in venous blood volumes close to the end of diving. Some freedivers also showed pronounced arterial deoxygenation, the most extreme of which resulted in an arterial saturation of 25%. Freedivers also displayed heart rate changes that were comparable to diving mammals both in magnitude and patterns of change. Finally, changes in cardiac waveform associated with heart rates less than 40 bpm were associated with changes indicative of a reduction in vascular compliance. The success here of CW-NIRS to non-invasively measure a suite of physiological phenomenon in a deep-diving mammal highlights its efficacy as a future physiological monitoring tool for human freedivers as well as free living animals. This article is part of the theme issue 'Measuring physiology in free-living animals (Part II)'.

Data-driven beamforming technique to attenuate ballistocardiogram artefacts in electroencephalography-functional magnetic resonance imaging without detecting cardiac pulses in electrocardiography recordings.

Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) is a very promising non‐invasive neuroimaging technique. However, EEG data obtained from the simultaneous EEG–fMRI are strongly influenced by MRI‐related artefacts, namely gradient artefacts (GA) and ballistocardiogram (BCG) artefacts. When compared to the GA correction, the BCG correction is more challenging to remove due to its inherent variabilities and dynamic changes over time. The standard BCG correction (i.e., average artefact subtraction [AAS]), require detecting cardiac pulses from simultaneous electrocardiography (ECG) recording. However, ECG signals are also distorted and will become problematic for detecting reliable cardiac peaks. In this study, we focused on a beamforming spatial filtering technique to attenuate all unwanted source activities outside of the brain. Specifically, we applied the beamforming technique to attenuate the BCG artefact in EEG–fMRI, and also to recover meaningful task‐based neural signals during an attentional network task (ANT) which required participants to identify visual cues and respond accurately. We analysed EEG–fMRI data in 20 healthy participants during the ANT, and compared four different BCG corrections (non‐BCG corrected, AAS BCG corrected, beamforming + AAS BCG corrected, beamforming BCG corrected). We demonstrated that the beamforming approach did not only significantly reduce the BCG artefacts, but also significantly recovered the expected task‐based brain activity when compared to the standard AAS correction. This data‐driven beamforming technique appears promising especially for longer data acquisition of sleep and resting EEG–fMRI. Our findings extend previous work regarding the recovery of meaningful EEG signals by an optimized suppression of MRI‐related artefacts.

Spectral analysis of physiological brain pulsations affecting the BOLD signal.

Physiological pulsations have been shown to affect the global blood oxygen level dependent (BOLD) signal in human brain. While these pulsations have previously been regarded as noise, recent studies show their potential as biomarkers of brain pathology. We used the extended 5 Hz spectral range of magnetic resonance encephalography (MREG) data to investigate spatial and frequency distributions of physiological BOLD signal sources. Amplitude spectra of the global image signals revealed cardiorespiratory envelope modulation (CREM) peaks, in addition to the previously known very low frequency (VLF) and cardiorespiratory pulsations. We then proceeded to extend the amplitude of low frequency fluctuations (ALFF) method to each of these pulsations. The respiratory pulsations were spatially dominating over most brain structures. The VLF pulsations overcame the respiratory pulsations in frontal and parietal gray matter, whereas cardiac and CREM pulsations had this effect in central cerebrospinal fluid (CSF) spaces and major blood vessels. A quasi‐periodic pattern (QPP) analysis showed that the CREM pulsations propagated as waves, with a spatiotemporal pattern differing from that of respiratory pulsations, indicating them to be distinct intracranial physiological phenomenon. In conclusion, the respiration has a dominant effect on the global BOLD signal and directly modulates cardiovascular brain pulsations.

Automated Cardiac Pulse Cycle Analysis From Photoplethysmogram (PPG) Signals Generated From Fingertip Videos Captured Using a Smartphone to Measure Blood Hemoglobin Levels.

Two billion people are affected by hemoglobin (Hgb) related diseases. Usual clinical assessments of Hgb are conducted by analyzing venipuncture-obtained blood samples in laboratories. A non-invasive, cheap, point-of-care and accurate Hgb test is needed everywhere. Our group has developed a non-invasive Hgb measurement system using 10-second Smartphone videos of the index fingertips. Custom hardware sets were used to illuminate the fingers. We tested four lighting conditions with wavelengths in the near-infrared spectrum suggested by the absorption properties of two primary components of blood-oxygenated Hgb and plasma. We found a strong linear correlation between our measured and laboratory-measured Hgb levels in 167 patients with a mean absolute percentage error (MAPE) of 5%. In our initial analysis, critical tasks were performed manually. Now, using the same data, we have automated or modified all the steps. For all, male, and female subjects we found a MAPE of 6.43%, 5.34%, and 4.85 and mean squared error (MSE) of 0.84, 0.5, and 0.49 respectively. The new analyses however, have suggested inexplicable inconsistencies in our results, which we attribute to laboratory measurement errors reflected in a non-normative distribution of Hgb levels in our studied patients, as well as excess noise in the specific signals we measured in the videos. Based on these encouraging results, and the promise of greater accuracy with our revised hardware and software tools, we now propose a rigorous validation study to demonstrate that this approach to hemoglobin measurement is appropriate for general clinical application.

POS-413 MANAGEMENT OF HYPERTENSION AFTER RENAL SYMPATHETIC DENERVATION IN MALE PATIENTS

Renal sympathetic denervation (RSD) is a catheter-based medical procedure that uses radiofrequency ablation on the renal sympathetic nerves to attenuate cardiac pulse pressure as well as juxtaglomerular renin release through beta-1 adrenergic receptor stimulation. Early studies on RSD demonstrated a marked benefit in the patients who underwent the procedure, but early cases have left more to be desired due to heterogeneity of clinical trial designs. Currently, the International Consensus Statement on Renal Denervation reports the need for further evaluation of RSD efficacy and suggested that RDN should not be offered to patients outside of clinical trials. Despite the International Consensus Statement recommendations, there are a number of reported peer-reviewed case reports of hypertensive patients undergoing renal denervation, yet there is currently no literature or systematic review on these case reports determining if the patient outcomes have produced similar results to the current literature of RSD clinical trials. Therefore, the aim of this study is to evaluate the efficacy of RSD treatment in attenuating hypertension among patients. A systematic review of the literature was performed on MEDLINE, Google Scholar, and the Cochrane Database of Systematic Reviews for renal denervation case studies. This study methodology was registered by PROSPERO International prospective register of systematic reviews (National Institute for Health Research). The search was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and checklist. Twenty-four male patients were found to be undergoing renal sympathetic denervation for hypertension treatment. The mean age of the patient population was 48.75 (CI: 41.68 - 55.82). The mean body mass index (BMI) was 31.02 (CI: 24.69 - 37.34). The reported duration of an ablation varied among each study, noting the shortest duration at 10 seconds, and the longest duration at 120 seconds. At post-RSD treatment, the mean 24-hour post-operative systolic blood pressure of reported cases was 144.40 mmHg (CI: 114.03 - 174.77). At 1-month follow-up, the mean systolic blood pressure was 142.00 mmHg (CI: 117.91 - 166.10). At 3-month follow-up, mean systolic blood pressure decreased to 126.25 mmHg (CI: 117.21 - 135.29). At 6-month follow-up, the mean systolic blood pressure increased to 160.00 mmHg. At 1-year follow-up, the mean systolic blood pressure of reported cases decreased to 131.00 mmHg. After RSD treatment, patient follow-up histories reported a mean number of 3.00 antihypertensive medications (CI: 1.96 - 4.04). On average, the severity of hypertension declined from borderline-malignant hypertension to stage I hypertension. The resulting reduction in blood pressure during these follow-up visits is consistent with the results of larger renal denervation registry studies, which addresses the International Consensus Statement’s desire for further evidence. However, one of the concerns posed in the literature regarding renal sympathetic denervation was the lack of reliable improvements in blood pressure over a prolonged period of time. Areas of interest that merit further study include tracking blood pressure changes beyond one year, monitoring for complications, and following changes in all-cause mortality.

A theoretical framework for retrospective correction to the arterial input function in quantitative myocardial perfusion MRI.

To develop and evaluate a flexible, Bloch-equation based framework for retrospective correction to the arterial input function (AIF) obtained with quantitative cardiac perfusion pulse sequences. Our framework initially calculates the gadolinium concentration [Gd] based on T1 measurements alone. Next, is estimated from this initial calculation of [Gd] while assuming fast water exchange and using the literature native T2 and static magnetic field variation (ΔB0 ) values. Finally, the [Gd] is recalculated after performing correction to the Bloch equation signal model. Using this approach, we performed correction to historical phantom and in vivo, dual-imaging perfusion data sets from 3 different patient groups obtained using different pulse sequences and imaging parameters. Images were processed to quantify both the AIF and resting myocardial blood flow (MBF). We also performed a sensitivity analysis of our correction to ±20% variations in native T2 and ΔB0 . Compared with the ground truth [Gd] of phantom, the normalized root-means-square-error (NRMSE) in measured [Gd] was 5.1%, 1.3%, and 0.6% for uncorrected, our corrected, and Kellman's corrected, respectively. For in vivo data, both the peak AIF (7.0 ± 3.0 mM vs. 8.6 ± 7.1 mM, 7.2 ± 0.9 mM vs. 8.6 ± 1.7 mM, 7.7 ± 1.8 mM vs. 10.3 ± 5.1 mM, P < .001) and resting MBF (1.3 ± 0.1 mL/g/min vs. 1.1 ± 0.1 mL/g/min, 1.3 ± 0.1 mL/g/min vs. 1.1 ± 0.1 mL/g/min, 1.2 ± 0.1 mL/g/min vs. 0.9 ± 0.1 mL/g/min, P < .001) values were significantly different between uncorrected and corrected for all 3 patient groups. Both the peak AIF and resting MBF values varied by <5% over the said variations in native T2 and ΔB0 . Our theoretical framework enables retrospective correction to the AIF obtained with dual-imaging, cardiac perfusion pulse sequences.

Early detection of significant congenital heart disease: The contribution of fetal cardiac ultrasound and newborn pulse oximetry screening.

Fetal cardiac and newborn pulse oximetry screening has greatly facilitated the detection of cardiac abnormalities, which may be serious with potentially dire neonatal consequences. The prenatal diagnosis of a serious cardiac abnormality allows the attending obstetrician to organise the much safer in-utero transfer of the fetus for delivery at a tertiary centre, particularly if there is evidence of a duct-dependent lesion that may require the infusion of Prostaglandin E1 to maintain duct patency pending surgical intervention. Newborn pulse oximetry alerts the paediatrician that the baby may have a significant cardiac abnormality, which warrants further elucidation prior to discharge, rather than for the baby to represent unwell a few days later. Despite these advances, serious cardiac abnormalities may be missed on screening. Their detection then falls back onto the clinical acumen of the attending paediatrician/family physician to review the history, carefully elicit and evaluate the clinical signs further aided by whatever investigations that may be available at the birthing hospital, frequently less resourced than the tertiary centres. At the outset, a brief synopsis is provided of the clinical findings that may point to a cardiac abnormality. That is followed by a critical review of the accuracy of prenatal and newborn pulse oximetry screening with emphasis on the lesions that may be missed. Suggestions are made as to how to improve the diagnostic accuracy.