Heart Rate Range Research Articles

Thirty-Day Readmissions After Thoracic Endovascular Aortic Repair for Type B Aortic Dissection

Management of type B aortic dissection (TBAD) with thoracic endovascular aortic repair (TEVAR) carries a significant resource burden for the admitting hospital, including costs related to 30-day readmissions. Our objective was to define the patient population for 30-day readmissions after TEVAR for aortic dissection and to identify risk factors, readmission reasons, and possible preventive measures to reduce this readmission rate. A retrospective review of a prospectively collected database of all TEVARs performed to treat TBAD at a quaternary-level institution was performed. Patients readmitted to any of the institution's nine acute care hospitals within 30 days were identified and analyzed to characterize the significant demographic, comorbid, operative, and medical factors associated with readmission. Between 2012 and 2019, 294 patients underwent TEVAR for treatment of acute (n = 95 [48.8%]), subacute (n = 37 [12.6%]), or chronic (n = 112 [38.2%]) TBAD. Of the 279 patients alive at discharge, 45 patients (16.1%) were readmitted within 30 days, with a mean time to readmission of 11.8 ± 8.9 days. Readmission primary diagnosis was most commonly aorta related (n = 13 [28.9%]) or heart related (n = 11 [24.4%]); other reasons included gastroenterologic (n = 6 [13.3%]), neurologic (n = 5 [11.1%]), pulmonary related (n = 4 [8.9%]), infectious (n = 3 [6.7%]), and nonclassified (n = 2 [4.4%]). Of 45 readmitted patients, 7 (15.5%) underwent a secondary intervention during the index readmission. Preoperative renal failure (creatinine concentration >1.5 mg/dL) was associated with an increased rate of 30-day readmission (31.1% vs 16.7%; P = .024), as was private insurance status (26.7% vs 13.7%; P = .029). Patients who underwent intentional left subclavian artery coverage (zone 2) or had visceral/renal stents implanted at the time of TEVAR trended toward higher 30-day readmission rates compared with patients undergoing descending thoracic aortic coverage (zone 3-5) only (46.7% vs 37.8% vs 15.6%; P = .088). Blood pressure range and heart rate range in the 24-hour period before discharge were not predictive of 30-day readmission. Pain status and creatinine level at discharge were also not associated with increased rate of 30-day readmission. A consequential number of patients require readmission within 30 days after surgical treatment of TBAD with TEVAR. Reasons for readmission are commonly aorta related and heart related and are associated with preoperative renal failure and insurance status. Increased case complexity, including coverage of the left subclavian artery or the need for visceral/renal stenting at the time of TEVAR, is an independent predictor of increased 30-day readmission rate. Effectiveness of medical impulse control was not associated with 30-day readmission. These data provide insight into the quality-oriented metrics associated with endovascular treatment of TBAD.

Exploring the feasibility of seamless remote heart rate measurement using multiple synchronized cameras

Heart rate (HR) measurement and monitoring is of great importance to determine the physiological and mental status of individuals. Recently, it has been demonstrated that HR can be remotely retrieved from facial video-based photoplethysmographic signals captured using consumer-grade cameras. However, in existing studies, subjects are mostly required to keep their facial regions of interest (ROIs) within one single camera. To make this technique usable in a daily life situation where subjects move around freely, we launch a preliminary simulated study of seamless remote HR measurement using multiple synchronized cameras by combining ensemble empirical mode decomposition (EEMD) with time-delay canonical correlation analysis (TDCCA), termed as EEMD-TDCCA. At each time point, a target ROI with the largest area is first determined from all the ROIs provided by all the cameras. Then, the RGB time sequence is formed by taking average of all pixels within each target ROI. Afterwards, the green channel time sequence is decomposed into several intrinsic mode functions (IMFs) and only the IMF candidates, whose frequency corresponding to the maximum amplitude falling into the interested HR range will be further processed by TDCCA. Finally, the first pair of the canonical variables having the largest correlation coefficient is the HR source and the corresponding HR is derived by peak detection or frequency analysis. Thirty subjects were recruited and four state-of-the-art methods were employed for comparison. The best performance was achieved by using the proposed EEMD-TDCCA followed by frequency analysis, with the mean absolute error 4.11 bpm, mean percentage error 5.26%, root mean square error 5.37 bpm, the Pearson’s correlation coefficient 0.90 and the intra-class correlation coefficient 0.89, demonstrating the feasibility of our proposed seamless remote HR measurement framework. This study will provide a promising solution for practical and robust non-contact HR measurement applications.

Heart Rate Determination in Newborns at Risk for Resuscitation in a Low-Resource Setting: A Randomized Controlled Trial

To compare 2 different methods (auscultation with a stethoscope and umbilical cord palpation) of heart rate (HR) estimation in newborns at risk for resuscitation in a low-resource setting. Sixty newborns at risk for resuscitation born at the St. Luke Catholic Hospital in Wolisso (Ethiopia) were randomized to HR assessment by auscultation using a stethoscope or umbilical cord palpation. HR was assessed at 60, 90, 120seconds, and 5minutes of life. The primary outcome was the agreement of HR obtained by auscultation or palpation compared with the HR determined by electrocardiogram. Mean difference between auscultation using a stethoscope and electrocardiogram was -13 bpm, -4 bpm, -6 bpm, and -10 bpm at 60, 90, 120seconds, and at 5minutes of life. Mean difference between palpation and electrocardiogram of was -20 bpm, -25 bpm, -23 bpm, and -31 bpm at 60, 90, 120seconds, and at 5minutes of life. The magnitude of the difference between auscultation and electrocardiogram was lower than that between palpation and electrocardiogram over time (P=.007). HR range was correctly identified in 14 out of 16 measurements (87%) with HR <100 bpm. HR assessment by auscultation was more accurate compared with cord palpation, but both may provide adequate clinical information to healthcare providers in terms of HR ranges. The clinical advantage of providing a stethoscope in low-resource settings remains to be established. ClinicalTrials.gov: NCT03854435.

Ocular Pulse Elastography: Imaging Corneal Biomechanical Responses to Simulated Ocular Pulse Using Ultrasound.

PurposeIn vivo evaluation of corneal biomechanics holds the potential for improving diagnosis and management of ocular diseases. We aimed to develop an ocular pulse elastography (OPE) technique to quantify corneal strains generated by naturally occurring pulsations of the intraocular pressure (IOP) using high-frequency ultrasound.MethodsSimulated ocular pulses were induced in whole porcine and human donor globes to investigate the effects of physiologic variations in baseline IOP, ocular pulse amplitude, and frequency on corneal strains. Ocular pulse–induced strains were measured in additional globes before and after UVA-riboflavin–induced corneal crosslinking. The central cornea in each eye was imaged with a 50-MHz ultrasound imaging system and correlation-based speckle tracking of radiofrequency data was used to calculate tissue displacements and strains.ResultsOcular pulse–induced corneal strains followed the cyclic changes of IOP. Both baseline IOP and ocular pulse amplitude had a significant influence on strain magnitude. Variations in pulse frequency within the normal human heart rate range did not introduce detectable changes in corneal strains. A significant decrease of corneal strain, as quantified by the OPE technique, was observed after corneal crosslinking. The extent of corneal stiffening (i.e., strain reduction) seemed to correlate with the initial strain magnitude.ConclusionsThis ex vivo study demonstrated the feasibility of the OPE method to quantify corneal strains generated by IOP pulsation and detect changes associated with corneal crosslinking treatment.Translational RelevanceIntegrating in vivo measurement of IOP and ocular pulse amplitude, the OPE method may lead to a new clinical tool for safe and quick biomechanical evaluations of the cornea.

Electrocardiographic Studies in Shall Sheep

DOI: 10.5152/actavet.2019.19018 The use of sheep in experimental animal models has increased recently. In the present study, we investigated normal electrocardiogram (ECG) parameters of clinically healthy Shall sheep. The animals were divided into two gender and age groups. Electrocardiograms were recorded on a base-apex lead, using limb lead I for at least 2 minutes. The heart rate range was 71–166 beats/min, with an average and standard deviation of 112.47±29.36. Statistical tests did not reveal any significant differences between two genders and ECG parameters. On the other hand, there was a significant difference between different age groups in the heart rate (p<0.001), P duration (p=0.030), QRS duration (p=0.005), and the P–R interval (p=0.005), Q–T interval (p<0.001), and R–R interval (p<0.001). Sheep with sinus arrhythmias had a significantly lower mean heart rate than sheep with normal rhythm (p=0.007). Furthermore, an analysis indicated that there was a significant difference between the age groups and the cardiac dysrhythmias (p<0.01). The results of this study can be used as a reference in studies on the Shall sheep breed. Cite this article as: Mirabad, M., Rezakhani, A., 2019. Electrocardiographic Studies in Shall Sheep. Acta Vet Eurasia 45, 96-100.

Respiratory motion-compensated high-resolution 3D whole-heart T1\u03c1 mapping

BackgroundCardiovascular magnetic resonance (CMR) T1ρ mapping can be used to detect ischemic or non-ischemic cardiomyopathy without the need of exogenous contrast agents. Current 2D myocardial T1ρ mapping requires multiple breath-holds and provides limited coverage. Respiratory gating by diaphragmatic navigation has recently been exploited to enable free-breathing 3D T1ρ mapping, which, however, has low acquisition efficiency and may result in unpredictable and long scan times. This study aims to develop a fast respiratory motion-compensated 3D whole-heart myocardial T1ρ mapping technique with high spatial resolution and predictable scan time.MethodsThe proposed electrocardiogram (ECG)-triggered T1ρ mapping sequence is performed under free-breathing using an undersampled variable-density 3D Cartesian sampling with spiral-like order. Preparation pulses with different T1ρ spin-lock times are employed to acquire multiple T1ρ-weighted images. A saturation prepulse is played at the start of each heartbeat to reset the magnetization before T1ρ preparation. Image navigators are employed to enable beat-to-beat 2D translational respiratory motion correction of the heart for each T1ρ-weighted dataset, after which, 3D translational registration is performed to align all T1ρ-weighted volumes. Undersampled reconstruction is performed using a multi-contrast 3D patch-based low-rank algorithm. The accuracy of the proposed technique was tested in phantoms and in vivo in 11 healthy subjects in comparison with 2D T1ρ mapping. The feasibility of the proposed technique was further investigated in 3 patients with suspected cardiovascular disease. Breath-hold late-gadolinium enhanced (LGE) images were acquired in patients as reference for scar detection.ResultsPhantoms results revealed that the proposed technique provided accurate T1ρ values over a wide range of simulated heart rates in comparison to a 2D T1ρ mapping reference. Homogeneous 3D T1ρ maps were obtained for healthy subjects, with septal T1ρ of 58.0 ± 4.1 ms which was comparable to 2D breath-hold measurements (57.6 ± 4.7 ms, P = 0.83). Myocardial scar was detected in 1 of the 3 patients, and increased T1ρ values (87.4 ± 5.7 ms) were observed in the infarcted region.ConclusionsAn accelerated free-breathing 3D whole-heart T1ρ mapping technique was developed with high respiratory scan efficiency and near-isotropic spatial resolution (1.7 × 1.7 × 2 mm3) in a clinically feasible scan time of ~ 6 mins. Preliminary patient results suggest that the proposed technique may find applications in non-contrast myocardial tissue characterization.

The electrocardiographic peculiarities of Algerian competitive athletes in the region of Sétif

to study electrocardiographic abnormalities in Algerian competitive athletes in the Sétif region, and compare with other international studies. 621 competitive athletes aged 12 and over (86% male, mean age 17.38 years) were included in our observational and cross-sectional epidemiological study. Our study confirms the rarity of rhythmic incidents in athletes (regular sinus rhythm 81.3%, sinus arrhythmia 17.7%, rhythm disorders 1%). The prevalence of bradycardia is 20.6%. It is proportional to age and more pronounced among male athletes, the influence of training on heart rate is not significant since 8 hours of training per week. The prevalence of fragmented QRS is 12.6%. The index of Sokolow-Lyon > 35 mm is found in 31.9% of athletes, with a male predominance. The pathology index is found in 8.2% of athletes without significant difference between the two sexes, these criteria of the HVG are not influenced by training, but rather by the type of sport activity and the intensity of dynamic activity. The prevalence of BAV 1 (1.3% in our study) is independent of the importance of bradycardia. The prevalence of early repolarization (RP) is 26.1%, with male predominance. We investigated the influence of age, gender, sport, training, electrical LVH and heart rate on RP. The lower topography of RP is the most common (65.4%) and hooking is the predominant aspect (57.4%). The latter is influenced by gender, age, type of sport, training, heart rate and QRS range. While the impasto is influenced only by the amplitude of the QRS. PR is associated with concave and ascending ST segment elevation in 30.7% of cases. The prevalence of non-specific branch blocks is 1.3% ( Table 1 ). The ECG was normal in 29.3% of athletes with a female predominance and presents adaptive abnormalities to regular exercise in 66.3% with male predominance. 4.3% of athletes (with a female predominance) have abnormal aspects, not related to sports training.

Evaluation of dentists regulatory systems stress during the provision of dental care according to pulse oximetry data

To evaluate the status of individual hemodynamic parameters (HR) and respiratory indicators of dentists performing local anesthesia. Material and methods. In the period from April 2019 to December 2019 the determination of heart rate (Heart rate) and blood saturation at 120 doctors aged 25-55 years was performed. The value of blood saturation by non-invasive pulse oximeter technique: SpO2 measurement range 0-99%; heart rate range 18-300 beats per minute. The limit of 95-98% was considered normal. However, we consider it correct to note the introduction of an error of 0.1% due to the constant wearing of a dentist's tight polymer mask. All subjects were preliminarily determined by Robergs-Landvere formula: maximum heart rate (MF)=205.8-(0.685·age). Maximum HR limits for the groups of subjects were 185.6±3.1 beats per minute in the first group; 178.7±3.1 beats per minute in the second group; 171.5±3.4 beats per minute in the third group. In all groups the tendency to decrease blood saturation in case of pain appearance in patients during treatment against the background of block anesthesia, as well as during anesthesia on the mandible was determined. The definition of SpO2 showed a slight downward trend in blood saturation when pain occurs within normal parameters. Thus, the limit of changes in the index against the background of performed local anesthesia on the mandible was 95.2-96.1% and 96.3-96.6% on the maxilla. Measurement of arterial oxygen saturation in dentists showed a tendency for a slight decrease in this indicator within the normal range when the patient developed pain. Thus, the limit of changes in the indicator against the background of local anesthesia on the lower jaw was 95.2-96.1%, on the upper jaw - 96.3-96.6%.

Long-term effects of opioids on the cardiovascular system

Long-term effects of opioids on the cardiovascular system

Calculation the intensity of aerobic exercise in fitness

According to the vast majority of experts, aerobic exercises are basic in fitness. Their effectiveness in the practice involves the rational regulation of load parameters, one of which is the intensity of exercises. However as practice shows the proposed methods for determining the necessary intensity of aerobic exercises do not quite adequately take into account the individual characteristics - age and fitness level.&#x0D; The purpose of the research is to evaluate methods for calculating intensity of aerobic exercise in fitness. In our studies we proceeded from the fact that calculation methods should consider two main trends.&#x0D; &#x0D; At the aging heart rate at rest slightly rises, and the upper pulse during exercises decreases.&#x0D; A higher fitness connected with significant decrease in heart rate at rest and an increase in its upper rate at critical intensity (expanding the range of heart rate during exercise). According to the vast majority of specialists, aerobic exercise is basic in wellness physical culture. Their effective application in the practice of wellness work implies rational regulation of the load parameters, one of which is the intensity of work.&#x0D; &#x0D; As a result the analysis of real situations it was demonstrated that the calculation intensity of aerobic activity according to heart rate indicators using formulas that take into account only the age of the practitioners is applicable in a certain age range (up to about 50-55 years). As age increases the correctness of such calculations decreases and loses its meaning in certain point due to the fact that calculated indicators of heart rate during exercises may be less than those at rest.&#x0D; Karvonen formula which takes into account the individual level of physical fitness for heart rate at rest is more accurate for determining heart rate in aerobic exercise. Its using allows us more correctly determine the lower pulse during exercises declining it because decrease in resting heart rate. However this formula also declining the upper pulse during exercises, although it should increase as the cardiovascular system improves.

Synchronized Chest Compressions for Pseudo-PEA: Proof of Concept and a Synching Algorithm

Objective: The two objectives of this report are: first, to describe a comparison of chest compressions unsynchronized or synchronized to native cardiac activity in a porcine model of hypotension, and second, to develop an algorithm to provide synchronized chest compressions throughout a range of native heart rates likely to be encountered when treating PEA cardiac arrest. Methods: We adapted our previously developed signal-guided CPR system to provide compressions synchronized to native electrical activity in a porcine model of hypotension as a surrogate of PEA arrest. We describe the first comparison of unsynchronized to synchronized compressions in a single animal as a proof-of-concept. We developed an algorithm to provide optimal synchronized chest compressions regardless of intrinsic PEA heart rate while simultaneously maintaining the chest compression rate within a desired range. We tested the algorithm with computer simulations measuring the proportion of intrinsic and compression beats that were synchronized, and the compression rate and its standard deviation, as a function of intrinsic heart rate and heart rate jitter. Results: We demonstrate and compare unsynchronized versus synchronized chest compressions in a single porcine model with an intrinsic rhythm and hypotension. Synchronized, but not unsynchronized, chest compressions were associated with increased blood pressure and coronary perfusion pressure. Our synchronized chest compression algorithm is able to provide synchronized chest compressions to over 90% of intrinsic beats for most heart rates while maintaining an average compression rate between 90 and 140 compressions per minute with relatively low variability. Conclusions: Synchronized chest compression therapy for pulseless electrical rhythms is feasible. A high degree of synchronization can be maintained over a broad range of intrinsic heart rates while maintaining the compression rate within a satisfactory range. Further investigation to assess benefit for treatment of PEA is warranted.

INDIVIDUALIZED SPORTS MANAGEMENT SCHEME FOR PREGNANT WOMEN IN CHINA

In recent years, pregnant women in China generally face problems such as unbalanced and excessive nutrition, lack of proper exercise during pregnancy, which shows a significant increase in weight during pregnancy, leading to an increasing trend of perinatal complications. At present, there is less sports health management system for pregnant women throughout pregnancy. In view of this, based on the existing research in related fields, this study deeply explores the appropriate monitoring methods of pregnant women’s sports in China. In this study, effective and convenient testing methods and evaluation criteria were proposed for pregnant women’s sports and psychology. The research idea was a method based on the pulse wave to detect pregnant women’s cardiac reserve capacity, and grading the Diastolic/Systolic value of pregnant women as a reference for grading individualized target heart rate range of moderate intensity exercise. The effective time and energy expenditure of pregnant women were assessed by monitoring the exercise process. The purpose is to help and guide pregnant women in the whole process of pregnancy self-movement management, and thus improve the quality of maternal health care services in China.

VDT visual fatigue monitoring based on feature extraction from unconstrained BCG

An unconstrained visual display terminal (VDT) visual fatigue monitoring method based on BCG is studied. A VDT visual fatigue test is designed and implemented in this study, also acceleration signals are obtained by using an acceleration sensor, which is installed on the seat back. Then, BCG is obtained by adaptive threshold wavelet denoising, FFT, frequency domain filtering in the range of heart rate, and IFFT. Low frequency (LF) is extracted after the RR interval and JJ interval are calculated by the wavelet algorithm. Curves of two kinds of LF with the usage of VDT were obtained and were identical. Thus, the authors can draw conclusions that BCG can replace ECG to achieve unconstrained monitoring of VDT visual fatigue and LF gradually increases with VDT visual fatigue becoming more and more serious. Finally, we compare LF curves of BCG and ECG during use VDT to draw a conclusion that BCG can replace ECG to monitor VDT visual fatigue in an unconstrained way. Also, the confidence interval is used to verify the reliability of SD subjective evaluation, and the conclusion is reliable.

Abstract 254: Synchronized Chest Compressions for Pseudo-PEA: Proof of Concept and Synching Algorithm

Introduction: Pulseless electrical activity (PEA) is a common rhythm in cardiac arrest with a persistently poor outcome. This report describes our successful development of a synchronized compression device and algorithm to treat PEA with or without intrinsic myocardial contractions. Methods: We adapted our previously developed signal-guided CPR system to provide synchronized compressions in a porcine model of cardiac arrest. We describe the first comparison of unsynchronized to synchronized compressions in a single animal as a proof-of-concept. We developed an algorithm to provide optimal synchronized chest compressions regardless of intrinsic heartrate while simultaneously maintaining the chest compression rate within a desired range. We tested the algorithm with computer simulations measuring the proportion of intrinsic and compression beats that were synchronized, and the compression rate and its standard deviation, as a function of intrinsic heartrate and heartrate jitter. Results: We demonstrate and compare unsynchronized versus synchronized chest compressions in a single porcine model with an intrinsic rhythm and hypotension. Synchronized, but not unsynchronized, chest compressions were associated with increased blood pressure and coronary perfusion pressure (Figure). Our synchronized chest compression algorithm is able to provide synchronized chest compressions to over 90% of intrinsic beats for most heartrates while maintaining an average compression rate between 95 and 135 BPM with relatively low variability. Conclusion: Synchronized chest compression therapy for pulseless electrical rhythms is feasible. A high degree of synchronization can be maintained over a broad range of intrinsic heart rates while maintaining the compression rate within a satisfactory range. Further investigation to assess benefit for treatment of PEA is warranted.

Accuracy of wrist-worn heart rate monitors for rate control assessment in atrial fibrillation

BackgroundWrist-worn heart rate (HR) monitors are increasingly popular. A paucity of data exists on their accuracy in atrial fibrillation (AF) in ambulatory patients. We sought to assess the HR accuracy of two commercially available smart watches [SW] (Fitbit Charge HR [FB] and Apple Watch Series 3 [AW]) compared with Holter monitoring in an ambulant patient cohort. MethodsThirty-two participants ≥18 years referred for 24-hour Holter monitoring were prospectively recruited. Each participant was randomly allocated to wear either a FB or AW along with their Holter monitor. ResultsAcross all devices, 53,288 heart rate values were analysed from 32 participants. Twenty wore the AW (17 had persistent AF and 3 had sinus rhythm [SR]) while 12 participants wore the FB (9 in persistent AF and 3 in SR). Participants in SR demonstrated strong agreement compared to Holter monitoring (bias <1 beat, limits of agreement [LoA] −11 to 11 beats). In AF, both devices underestimated HR measurements (bias −9 beats, LoA −41 to 23). The degree of underestimation was more pronounced when HR > 100 bpm (bias of −28 beats for HR range 100–120 bpm, −48 for 120–140 bpm, and −69 for >140 bpm) compared to a slower HR (bias of −6 for HR range 80–100 bpm, <1 for 60–80 bpm, and −1 for <60 bpm). ConclusionIn ambulatory patients, smartwatches underestimated HR in AF particularly at HR ranges >100 bpm. Further improvements in device technology are needed before integrating them into the clinical management of rate control in AF.

The heart rate method for estimating oxygen uptake: analyses of reproducibility using a range of heart rates from commuter walking

BackgroundThe heart rate method, based on the linear relation between heart rate and oxygen uptake, is potentially valuable to monitor intensity levels of physical activities. However, this depends not least on its reproducibility under standard conditions. This study aims, therefore, to evaluate the reproducibility of the heart rate method in the laboratory using a range of heart rates associated with walking commuting.MethodsOn two different days, heart rate and oxygen uptake measurements were made during three submaximal (model 1) and a maximal exercise intensity (model 2) on a cycle ergometer in the laboratory. 14 habitual walking commuters participated. The reproducibility, based on the regression equations from test and retest and using three levels of heart rate from the walking commuting, was analyzed. Differences between the two models were also analyzed.ResultsFor both models, there were no significant differences between test and retest in the constituents of the regression equations (y intercept, slope and r value). Neither were there any systematic differences in estimated absolute levels of VO2 between test and retest for either model. However, some rather large individual differences were seen in both models. Furthermore, no significant differences were seen between the two models in slopes, intercepts and r values of the regression equations or in the estimated VO2.ConclusionThe heart rate method shows good reproducibility on the group level in estimating oxygen consumption from heart rate–oxygen uptake relations in the laboratory, and based on three levels of heart rate which are representative for walking commuting.

P1236Revealing cardiac mechanics with CMR whilst CRT is active: the first step

Abstract Introduction Cardiac resynchronisation therapy (CRT) is a routine treatment for heart failure with reduced ejection fraction and conduction delay to improve symptoms and prognosis. Technological advancements both in cardiac magnetic resonance (CMR) and devices (MRI-conditional modes) now enable investigation of the haemodynamic response to CRT over a range of heart rates. Methods Patients with a CRT-D device were enrolled from heart failure clinics at a single tertiary centre. A complete device system assessment and baseline device check was conducted to ensure MRI compatibility and suitability. Left ventricular (LV) volumes and systolic blood pressure were measured at baseline and heart rates of 75, 90, 100, 115, 125, and 140 bpm (randomised order) with CRT active and intrinsic conduction (AOO). MRI conditional mode parameters were replicated through standard parameter modification to ensure biventricular pacing during CRT active scans. All scans were conducted using a 3.0 T Siemens Prisma MRI scanner with analysis on commercially available software. Contractility was derived from the systolic blood pressure and left ventricular end systolic volume. A post scan device and lead assessment was conducted to assess for scanning safety. Results Scanning was conducted in 22 patients (safety cohort). Post scan battery voltage reduced by 2.9±1.0%. Mean change in atrial, right ventricular and left ventricular lead impedance was 0.5±0.06%, 3.0±0.04% and −1.7±0.05% respectively. Mean change in atrial, right ventricular and left ventricular pacing threshold was 0.0±0.3%, 8.3±0.3% and 5.6±0.3%. No patient experienced symptoms related to scanning or device failure. Preliminary data for patients with CRT on and off have been analysed (paired analysis cohort, n=8, 6 men). Mean age was 71.1±8.2, aetiology was primarily ischaemic (62.5%) with the remainder dilated cardiomyopathy. The mean LV ejection fraction at baseline was 29.4±12.9%. Biventricular pacing led to acute improvements in ejection fraction (p=0.005), left ventricular cardiac output (p&lt;0.0001) and contractility (p=0.05) over the entire range of heart rates studied. We also noted an improvement in the force frequency relationship during biventricular pacing with a higher peak contractility (p=0.05), a higher heart rate at which this occurred (HR=130) and a generally up sloping relationship when compared with intrinsic conduction. Conclusion We have demonstrated for the first time, the mechanistic improvements in cardiac contractility consequent to CRT using CMR and also that MRI scans of conditional devices can be safe with CRT active. Acknowledgement/Funding Dr A Koshy is conducting a PhD supported by grant from Medtronic. Dr Klaus Witte has received honoraria from Medtronic

Swimming-related effects on cerebrovascular and cognitive function.

Both acute and regular exercise influence vascular and cognitive function. Upright aquatic exercise increases mean middle cerebral artery blood velocity (MCAvmean) and has been suggested as favorable for cerebrovascular adaptations. However, MCAvmean has not been reported during swimming. Thus, we examined the cerebrovascular and cognitive effects of swimming. Ten land‐based athletes (22 ± 5 years) and eight swimmers (19 ± 1 years) completed three cognitive tasks and four conditions that were used to independently and collectively delineate the swimming‐related factors (i.e., posture, immersion, CO2 retention [end‐tidal CO2; PETCO2], and motor involvement). Measurements of MCAvmean and PETCO2 were taken throughout each condition. Prone posture increased MCAvmean by 11% (P < 0.01 vs. upright land). Water immersion independently increased MCAvmean when upright (12%; P < 0.01) but not prone (P = 0.76). The consequent rise in PETCO2 during head‐out, breast‐stroke swimming (50% heart rate range) independently increased MCAvmean by 14% (P < 0.01), while the motor involvement of swimming per se did not significantly change MCAvmean (P = 0.32). While accounting for sex, swimmers had ~17% lower MCAvmean during all rest conditions (P ≤ 0.05). However, in a subset of participants, both groups had similar internal carotid artery diameters (P = 0.99) and velocities (P = 0.97). Water immersion per se did not alter cognition (P ≥ 0.15), but 20 min of moderate‐intensity swimming improved visuomotor performance by 4% (P = 0.03), regardless of athlete group (P = 0.12). In conclusion, breast‐stroke swimming increased MCAvmean mostly due to postural and PETCO2 effects, with minimal contributions from water immersion or motor activity. Lastly, swimming improved cognitive functioning acutely, regardless of athlete group. Future research should explore the chronic effects of swimming on cerebrovascular function and cognition, particularly in aging.

Prognostic Significance of Heart Rate and Beta-Blocker Use in Sinus Rhythm in Patients with Heart Failure and Preserved Ejection Fraction.

Prognostic significance of heart rate (HR) in heart failure with preserved ejection fraction (HFpEF) remains poorly understood. To evaluate the association of HR and beta-blocker use with all-cause mortality and the optimal HR range in patients with HFpEF and sinus rhythm (SR). During a follow-up of 2.7years (IQR 1.2-4.1years), the 330 patients with median age 73 (IQR 64-79) years, 52.1% men, were included. HFpEF was defined as patients with EF ≥ 50%. The outcome measure was all-cause mortality. In total, 96 (29.1%) of patients with HFpEF and SR died. A linear tendency between HR and mortality was observed in SR. Compared to the reference strata HR ≤ 60bpm, HR increment was associated with progressively increased risk in mortality (Chi-square = 13.90, Log rank P = 0.001) by Kaplan-Meier analyses. Univariate Cox regression showed that in SR, compared with that in HR 61-80bpm, the unadjusted hazard ratios for mortality were 0.41 (95% CI 0.23-0.74, P = 0.003) in HR ≤ 60bpm, 1.38 (95% CI 0.85-2.24, P = 0.189) in HR > 80bpm. Multivariate Cox regression showed that compared with that in HR 61-80bpm, the adjusted hazard ratios for mortality were 0.37 (95% CI 0.19-0.75, P = 0.005) in HR ≤ 60bpm, 0.96 (95% CI 0.52-1.74, P = 0.899) in HR > 80bpm. Univariate Cox regression showed that the unadjusted hazard ratios for mortality were 0.52 (95% CI 0.33-0.84, P =0.003) in patients with beta-blocker as compared patients without beta-blocker. Multivariate Cox regression showed that the adjusted hazard ratios for mortality were 0.48 (95% CI 0.26-0.87, P = 0.016) in patients with beta-blocker as compared patients without beta-blocker. HR is independently associated with increased all-cause mortality in SR and a lower HR (≤ 60bpm) is favorable for better outcome in HFpEF patients with SR. Beta-blocker use is associated with reduced mortality and a lower HR is associated with reduced mortality in HFpEF patients with SR.

Behavioural anxiety predisposes rabbits to intra-operative apnoea and cardiorespiratory instability

Rabbits are prone to complications from both anaesthesia and anxiety. Given that anxiety can often impact quality of anaesthesia, we developed a novel cage-side anxiety assessment, and sought to determine whether it correlated to pre- and intra-operative cardiorespiratory changes. We examined 31 singly-housed, female New Zealand white rabbits scheduled for a brief experimental ophthalmic surgery using the anxiety assessment, which consisted of behavioural observations, a modified human intruder test, and a novel object test, all performed in the home cage; however, the novel object test was dismissed mid-study when the first group of rabbits tested (n = 14) approached the object in almost equal time. On the day of surgery, in addition to monitoring standard cardiorespiratory parameters, we ranked the ease of intubation, and recorded the frequency of pre- and intra-operative apnoea. Our anxiety assessment produced almost perfect inter-observer agreement (κ = 1.00) and acceptable internal consistency of its tests (α = 0.75). We found that 9 rabbits were behaviourally anxious, and 22 were non-anxious. Anxious rabbits exhibited an increased frequency of intra-operative apnoea (F = 7.03, p = 0.01), and trended towards showing a wider maximum (F = 4.05, p = 0.06) and range of heart rate (F = 3.74, p = 0.07) as compared with the non-anxious group. Additionally, irrespective of anxiety, rabbits that experienced pre-operative apnoea were more difficult to intubate (U = 7.50, p = 0.001). Based upon these results, our anxiety assessment successfully differentiated a sub-population of rabbits that were behaviourally anxious and exhibited cardiorespiratory instability during surgery. This practical cage-side tool can be used as a pre-anaesthetic screen to identify rabbits that may be prone to complications and enable pre-operative intervention. Given that cages are comparatively barren to the natural environment, home-cage novel object tests may be less useful in laboratory species, as the excitement of a new enrichment overcomes potential neophobia. In summary, employing the anxiety assessment as an adjunct to individually planned anaesthesia regimens serves as a refinement to the welfare of rabbits.