Systolic time intervals as simple echocardiographic parameters of left ventricular systolic performance: correlation with ejection fraction and longitudinal two-dimensional strain

A Review on Recent Advancements of Biomedical Radar for Clinical Applications

The field of biomedical radar has witnessed significant advancements in recent years, paving the way for innovative and transformative applications in clinical settings. Most medical instruments invented to measure human activities rely on contact electrodes, causing discomfort. Thanks to its non-invasive nature, biomedical radar is particularly valuable for clinical applications. A significant portion of the review discusses improvements in radar hardware, with a focus on miniaturization, increased resolution, and enhanced sensitivity. Then, this paper also delves into the signal processing and machine learning techniques tailored for radar data. This review will explore the recent breakthroughs and applications of biomedical radar technology, shedding light on its transformative potential in shaping the future of clinical diagnostics, patient and elderly care, and healthcare innovation.

1-Year Mortality Prediction through Artificial Intelligence Using Hemodynamic Trace Analysis among Patients with ST Elevation Myocardial Infarction

Background and Objectives: Patients presenting with ST Elevation Myocardial Infarction (STEMI) due to occlusive coronary arteries remain at a higher risk of excess morbidity and mortality despite being treated with primary percutaneous coronary intervention (PPCI). Identifying high-risk patients is prudent so that close monitoring and timely interventions can improve outcomes. Materials and Methods: A cohort of 605 STEMI patients [64.2 ± 13.2 years, 432 (71.41%) males] treated with PPCI were recruited. Their arterial pressure (AP) wave recorded throughout the PPCI procedure was analyzed to extract features to predict 1-year mortality. After denoising and extracting features, we developed two distinct feature selection strategies. The first strategy uses linear discriminant analysis (LDA), and the second employs principal component analysis (PCA), with each method selecting the top five features. Then, three machine learning algorithms were employed: LDA, K-nearest neighbor (KNN), and support vector machine (SVM). Results: The performance of these algorithms, measured by the area under the curve (AUC), ranged from 0.73 to 0.77, with accuracy, specificity, and sensitivity ranging between 68% and 73%. Moreover, we extended the analysis by incorporating demographics, risk factors, and catheterization information. This significantly improved the overall accuracy and specificity to more than 76% while maintaining the same level of sensitivity. This resulted in an AUC greater than 0.80 for most models. Conclusions: Machine learning algorithms analyzing hemodynamic traces in STEMI patients identify high-risk patients at risk of mortality.

The hemodynamic cardiac profiler volume-time curves and related parameters: an MRI validation study

Background.The hemodynamic cardiac profiler (HCP) is a new, non-invasive, operator-independent screening tool that uses six independent electrode pairs on the frontal thoracic skin, and a low-intensity, patient-safe, high-frequency applied alternating current to measure ventricular volume dynamics during the cardiac cycle for producing ventricular volume-time curves (VTCs).Objective.To validate VTCs from HCP against VTCs from MRI in healthy volunteers.Approach.Left- and right-ventricular VTCs were obtained by HCP and MRI in six healthy participants in supine position. Since HCP is not compatible with MRI, HCP measurements were performed within 20 min before and immediately after MRI, without intermittent fluid intake or release by participants. Intraclass correlation coefficients (ICCs) were calculated to validate HCP-VTC against MRI-VTC and to assess repeatability of HCP measurements before and after MRI. Bland-Altman plots were used to assess agreement between relevant HCP- and MRI-VTC-derived parameters. Precision of HCP's measurement of VTC-derived parameters was determined for each study participant by calculating the coefficients of variation and repeatability coefficients.Main results.Left- and right-ventricular VTC ICCs between HCP and MRI were >0.8 for all study participants, indicating excellent agreement between HCP-VTCs and MRI-VTCs. Mean (range) ICC of HCP right-ventricular VTC versus MRI right-ventricular VTC was 0.94 (0.88-0.99) and seemed to be slightly higher than the mean ICC of HCP left-ventricular VTC versus MRI-VTC (0.91 (0.80-0.96)). The repeatability coefficient for HCP's measurement of systolic time (tSys) was 45.0 ms at a mean value of 282.9 ± 26.3 ms. Repeatability of biventricular HCP-VTCs was excellent (ICC 0.96 (0.907-0.995)).Significance.Ventricular volume dynamics measured by HCP-VTCs show excellent agreement with VTCs measured by MRI. Since abnormal tSys is a sign of numerous cardiac diseases, the HCP may potentially be used as a diagnostic screening tool.

AI-enabled epidermal electronic system to automatically monitor a prognostic parameter for hypertension with a smartphone

We present a wearable, flexible, wireless and smartphone-enabled epidermal electronic system (EES) for the continuous monitoring of a prognostic parameter for hypertension. The thin and lightweight EES can be tightly attached to the chest of a patient and synchronously monitor first lead electrocardiograms (ECG) and seismocardiograms (SCG). To demonstrate the concept, we developed the EES using state-of-the-art cleanroom technologies. Two types of sensors were integrated: A pair of metal electrodes to contact the skin and to record ECG and a vibration sensor based on a thin piezoelectric polymer to record SCG from the same location of the chest, simultaneously. The complete EES was powered by the near field communication functionality of the smartphone. We developed a machine-learning algorithm and trained it on public ECG data and recorded SCG signals to extract characteristic features of the recordings. Binary classifiers were used to automatically annotate peaks. After training, the algorithm was transferred to the smartphone to continuously analyze the timing between particular ECG and SCG peaks and to extract the Weissler's index as a prognostic parameter for hypertension. Tests with data of healthy control persons and clinical experiments with patients diagnosed with cardio-pulmonary hypertension showed a promising prognostic performance. The presented EES technology could be utilized for pre-screening of cardio-pulmonary hypertension, which is a strong burden in our today's healthcare system.

Analysis of risk factors for changes of left ventricular function indexes in Chinese patients with gout by echocardiography

Background: Echocardiographic data investigating the association between left ventricular (LV) function and gout is still limited. Purpose: To analyze the association of echocardiographic parameters based on two-dimentional speckle tracking analysis with clinically related indicators in patients with gout, and to provide a clinical basis for the early diagnosis and treatment of cardiovascular disease in patients with gout. Methods: This study collected gout patients who visited the outpatient and inpatient departments of the first affiliated hospital of chengdu medical college from November 2019 to December 2020. Spearman correlation test was performed to analyze the correlation coefficients between the laboratorial indicators with echocardiographic parameters. And the logistic regression analysis was performed to evaluate the independent effects. Results: The results of multivariate logistic regression showed that fasting plasma glucose (FPG) was a risk factor for the decrease in absolute value of global longitudinal strain [GLS (OR = 2.34; 95% CI, 1.01-5.39; p = 0.04)], Urea was a risk factor for absolute reduction in GCS (OR = 1.40; 95% CI, 1.07-1.85; p = 0.02), age (OR = 1.09, 95% CI, 1.04-1.16; p = 0.001), and hypertension (OR = 8.35; 95% CI, 1.83-38.02; p = 0.006) were risk factors for increased E/Em. High urea levels were significantly related with high risks of LVH (OR = 1.59, 95% CI, 1.04-2.43; p = 0.03) and enlargement of LAVI (OR = 1.68, 95% CI, 1.01-2.80; p = 0.04). Conclusion: Our study found that elevated urea and FPG were risk factors for subclinical LV myocardial dysfunction in patients with gout, which might provide a theoretical basis for the early diagnosis and treatment of heart disease in clinical practice.

Feasibility of Noninvasive Assessment of Cardiac Output during Exercise in Healthy Adults by a Novel Elaboration on Systolic Time Intervals

BACKGROUND

Although assessment of cardiovascular hemodynamics during exercise can provide clinical insights, it is challenging to acquire it in clinical settings.

OBJECTIVES

Accordingly, this preliminary study was to determine whether a novel elaboration on systolic time interval measures (eSTICO) method of quantifying cardiac output and stroke volume was comparable to those obtained using a validated soluble gas (open circuit CO measure [OpCircCO]) method or calculation based on oxygen consumption (oxygen consumption-based CO [VO2CO]) during exercise.

METHODS

For the present study, 14 healthy subjects (male: n = 12, female: n = 2) performed incremental exercise on a recumbent cycle ergometer. At rest and during exercise, cardiac output (CO) was obtained via the eSTICO method, while the OpenCircCO and VO2CO measures were obtained at the last minute of each workload.

RESULTS

At peak, there was no difference between eSTICO and OpCircCO (12.39 ± 3.06 vs. 13.96 ± 2.47 L/min, p > 0.05), while there was a slight difference between eSTICO and VO2CO (12.39 ± 3.06 vs. 14.28 ± 2.55 L/min, p < 0.05). When we performed correlation analysis with all subjects and all measures of CO at all WL, between eSTICO and OpenCircCO, there was a good relationship (r = 0.707, p < 0.001) with a Bland and Altman agreement analysis demonstrating a -1.6 difference (95% LoA: -6.3-3.5). Between eSTICO and VO2CO, we observed an r = 0.865 (p < 0.001) and a Bland and Altman agreement analysis with a -1.2 difference (95% LoA: -4.8-2.4).

CONCLUSION

A novel exploitation of cardiac hemodynamics using systolic timing intervals may allow a relatively good assessment of CO during exercise in healthy adults.

Evaluation of cardiac indices using M-mode echocardiography after administration of metoclopramide and ondansetron in donkeys (Equus asinus): an experimental study

The aim of the present study was to evaluate cardiac indices using M-mode echocardiography after the administration of metoclopramide and ondansetron in donkeys. For this purpose, 10 apparently healthy Egyptian Baladi donkeys (Equus asinus) were used in a crossover prospective study. Two trials were conducted with the administration of metoclopramide hydrochloride anhydrous at a dose of 0.25 mg Kg-1 and ondansetron hydrochloride sodium at a dose of 0.15 mg Kg-1. The control group (placebo) received a total volume of 50 mL of isotonic saline at 0.9%. An echocardiographic examination was performed using a Digital Color Doppler Ultrasound System equipped with a 2-3.9 MHz phased array sector scanner transducer. In general, the fractional shortening (FS%) was significantly affected by the time for metoclopramide (p = 0.031) and ondansetron (p = 0.047) compared with those of placebo, with treatment with metoclopramide provoking significantly higher percentages of FS% at T60 (p = 0.009) and T90 (p = 0.028) compared with those for ondansetron and placebo. The interaction of time x treatment also showed a statistically significant alteration of FS% (p < 0.05), while the values returned to the basal line at T240. Metoclopramide induced a significant decrease in E-point to septal separation (EPSS) at T90 (p = 0.005), and T240 (p = 0.007) compared with ondansetron and placebo. The time x treatment interaction also showed a significant (p < 0.05) variation in EPSS, with values returning to the basal line at T300. Mitral valve opening velocity (DE SLP) values were significantly affected by time (p = 0.004) in the metoclopramide group compared with those of ondansetron and placebo. Administration of metoclopramide and ondansetron provoked significant alterations of DE SLP at T60 (p = 0.039), T120 (p = 0.036), and T300 (p = 0.005) compared with placebo. In conclusion, caution should be exercised when administering both treatments, especially to animals with suspected cardiac problems.

Age- and sex-based normal reference ranges of the cardiac time intervals: the Copenhagen City Heart Study

BACKGROUND

Color tissue Doppler imaging (TDI) M-mode can be used to measure the cardiac time intervals including the isovolumic contraction time (IVCT), the left ventricular ejection time (LVET), the isovolumic relaxation time (IVRT), and the combination of all the cardiac time intervals in the myocardial performance index (MPI) defined as [(IVCT + IVRT)/LVET]. The aim of this study was to establish normal age- and sex-based reference ranges for the cardiac time intervals.

METHODS AND RESULTS

A total of 1969 participants free of cardiovascular diseases and risk factors from the general population with limited age range underwent an echocardiographic examination including TDI. The median age was 46 years (25th-75th percentile: 33-58 years), and 61.5% were females. In the entire study population, the IVCT was observed to be 40 ± 10 ms [95% prediction interval (PI) 20-59 ms], the LVET 292 ± 23 ms (95% PI 248-336 ms), the IVRT 96 ± 19 ms (95% PI 59-134 ms) and MPI 0.47 ± 0.09 (95% PI 0.29-0.65). All the cardiac time intervals differed significantly between females and males. With increasing age, the IVCT increased in females, but not in males. The LVET did not change with age in both sexes, while the IVRT increased in both sexes with increasing age. Furthermore, we developed regression equations relating the heart rate to the cardiac time intervals and age- and sex-based normal reference ranges corrected for heart rate.

CONCLUSION

In this study, we established normal age- and sex-based reference ranges for the cardiac time intervals. These normal reference ranges differed significantly with sex.

Systolic Time Interval Extraction in Hypertensive and Hypotensive Pig Models Using Wearable Near-Field Radio-Frequency Sensors

Screening and monitoring for cardiovascular diseases (CVDs) can be enabled by analyzing systolic time intervals (STIs). As CVDs have a strong causal correlation with hypertension, it is important to validate STI sensor accuracy in hypertensive hearts to ensure consistent performance in this prevalent cardiac disease state. This work presents STI extraction using a non-invasive near-field radio-frequency (RF) sensor during normotension, hypertension, and hypotension in a pig model. Waveform features of semilunar and atrioventricular valve dynamics during systole were extracted to derive isovolumic contraction time (ICT) and left ventricular ejection time (LVET), benchmarked by a phonocardiogram and aortic catheterization. Study-wide mean relative ICT and LVET errors were -4.4ms and -3.6ms, respectively, demonstrating high accuracy during both normal and abnormal systemic pressures.Clinical relevance- This work demonstrates accurate STI extraction with relative error less than 5 ms from a non-invasive near-field RF sensor during normotensive, hypotensive, and hypertensive systemic pressures, validating the sensor's accuracy as a screening tool during this disease state.

Use of a Cardiac Scale to Predict Heart Failure Events: Design of SCALE-HF 1

BACKGROUND

There is a need for simple, noninvasive solutions to remotely monitor and predict worsening heart failure (HF) events. SCALE-HF 1 (Surveillance and Alert-Based Multiparameter Monitoring to Reduce Worsening Heart Failure Events) is a prospective, multicenter study that will develop and assess the accuracy of the heart function index-a composite algorithm of noninvasive hemodynamic biomarkers from a cardiac scale-in predicting worsening HF events.

METHODS

Approximately 300 patients with chronic HF and recent decompensation will be enrolled in this observational study for model development. Patients will be encouraged to take daily cardiac scale measurements.

RESULTS

Approximately 50 HF events, defined as an urgent, unscheduled clinic, emergency department, or hospitalization for worsening HF will be used for model development. The composite index will be developed from hemodynamic biomarkers derived from ECG, ballistocardiogram, and impedance plethysmogram signals measured from the cardiac scale. Biomarkers of interest include weight, peripheral impedance, pulse rate and variability, and estimates of stroke volume, cardiac output, and blood pressure captured through the cardiac scale. The sensitivity, unexplained alert rate, and alerting time of the index in predicting worsening HF events will be evaluated and compared with the performance of simple weight-based rule-of-thumb algorithms (eg, weight increase of 3 lbs in 1 day or 5 lbs in 7 days) that are often used in practice.

CONCLUSIONS

SCALE-HF 1 is the first study to develop and evaluate the performance of a composite index derived from noninvasive hemodynamic biomarkers measured from a cardiac scale in predicting worsening HF events. Subsequent studies will validate the heart function index and assess its ability to improve patient outcomes.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT04882449.

Detecting heart failure using novel bio-signals and a knowledge enhanced neural network

BACKGROUND

Clinical decisions about Heart Failure (HF) are frequently based on measurements of left ventricular ejection fraction (LVEF), relying mainly on echocardiography measurements for evaluating structural and functional abnormalities of heart disease. As echocardiography is not available in primary care, this means that HF cannot be detected on initial patient presentation. Instead, physicians in primary care must rely on a clinical diagnosis that can take weeks, even months of costly testing and clinical visits. As a result, the opportunity for early detection of HF is lost.

METHODS AND RESULTS

The standard 12-Lead ECG provides only limited diagnostic evidence for many common heart problems. ECG findings typically show low sensitivity for structural heart abnormalities and low specificity for function abnormalities, e.g., systolic dysfunction. As a result, structural and functional heart abnormalities are typically diagnosed by echocardiography in secondary care, effectively creating a diagnostic gap between primary and secondary care. This diagnostic gap was successfully reduced by an AI solution, the Cardio-HART™ (CHART), which uses Knowledge-enhanced Neural Networks to process novel bio-signals. Cardio-HART reached higher performance in prediction of HF when compared to the best ECG-based criteria: sensitivity increased from 53.5% to 82.8%, specificity from 85.1% to 86.9%, positive predictive value from 57.1% to 70.0%, the F-score from 56.4% to 72.2%, and area under curve from 0.79 to 0.91. The sensitivity of the HF-indicated findings is doubled by the AI compared to the best rule-based ECG-findings with a similar specificity level: from 38.6% to 71%.

CONCLUSION

Using an AI solution to process ECG and novel bio-signals, the CHART algorithms are able to predict structural, functional, and valve abnormalities, effectively reducing this diagnostic gap, thereby allowing for the early detection of most common heart diseases and HF in primary care.

Myocardial performance index as a measure of global left ventricular function improves following isometric exercise training in hypertensive patients

As the leading cause of cardiovascular disease and mortality, hypertension remains a global health problem. Isometric exercise training (IET) has been established as efficacious in reducing resting blood pressure (BP); however, no research to date has investigated its effects on the myocardial performance index (MPI). Twenty-four unmedicated hypertensive patients were randomized to 4 weeks of IET and a control period in a crossover design. Tissue Doppler imaging was used to acquire cardiac time intervals pre- and post-IET and during the control periods. IET significantly improved all measures of cardiac time intervals, including isovolumic relaxation time (83.1 ± 10.3 vs. 76.1 ± 11.2 ms, p = 0.006), isovolumic contraction time (84.8 ± 10.3 vs. 72.8 ± 6.4 ms, p < 0.001), ejection time (304.6 ± 30.2 vs. 321.4 ± 20.8 ms, p = 0.015) and the MPI (0.56 ± 0.09 vs. 0.47 ± 0.05, p < 0.001). This is the first study to demonstrate that IET significantly improves cardiac time intervals. These findings may have important clinical implications, highlighting the potential utility of IET in the management of cardiac health in hypertensive patients.

Heart sound-derived systolic time intervals for atrioventricular delay optimization in cardiac resynchronization therapy

BACKGROUND

Phonocardiography (PCG) can be used to determine systolic time intervals (STIs) from ventricular pacing spike to the first heart sound (VS1) and from the first to the second heart sound (S1S2).

OBJECTIVE

The purpose of this study was to investigate the relations between STIs and hemodynamics during atrioventricular (AV) delay optimization of biventricular pacing (BiVP) in animals and patients.

METHODS

Five pigs with AV block underwent BiVP, while PCG was collected from an epicardial accelerometer. In 21 patients undergoing cardiac resynchronization therapy device implantation, PCG was recorded with a pulse generator-embedded microphone. Optimal AV delays derived from shortest VS1 and longest S1S2 were compared with AV delays derived from highest left ventricular pressure (LVP), maximal rate of rise in LVP, and stroke work.

RESULTS

In pigs, VS1 and S1S2 predicted the AV delays with optimal hemodynamics (highest LVP, maximal rate of rise in LVP, and stroke work) by a median error of 2-28 ms, resulting in a median loss of <2% of pump function. In patients, VS1 and S1S2 predicted the optimal AV delay by errors of 32.5 and 37.5 ms, respectively, resulting in 0.2%-0.9% lower LVP and stroke work, which were reduced to 21 and 24 ms in 8 patients with a full-capture AV delay of >180 ms.

CONCLUSION

During BiVP with varying AV delays, close relations exist between PCG-derived STIs and hemodynamic parameters. AV delays advised by PCG-derived STIs cause only a minimal loss of pump function compared with those based on invasive hemodynamic measurements.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01832493.

Computer-Aided Detection of Fiducial Points in Seismocardiography through Dynamic Time Warping

Accelerometer-based devices have been employed in seismocardiography fiducial point detection with the aid of quasi-synchronous alignment between echocardiography images and seismocardiogram signals. However, signal misalignments have been observed, due to the heartbeat cycle length variation. This paper not only analyzes the misalignments and detection errors but also proposes to mitigate the issues by introducing reference signals and adynamic time warping (DTW) algorithm. Two diagnostic parameters, the ratio of pre-ejection period to left ventricular ejection time (PEP/LVET) and the Tei index, were examined with two statistical verification approaches: (1) the coefficient of determination (R2) of the parameters versus the left ventricular ejection fraction (LVEF) assessments, and (2) the receiver operating characteristic (ROC) classification to distinguish the heart failure patients with reduced ejection fraction (HFrEF). Favorable R2 values were obtained, R2 = 0.768 for PEP/LVET versus LVEF and R2 = 0.86 for Tei index versus LVEF. The areas under the ROC curve indicate the parameters that are good predictors to identify HFrEF patients, with an accuracy of more than 92%. The proof-of-concept experiments exhibited the effectiveness of the DTW-based quasi-synchronous alignment in seismocardiography fiducial point detection. The proposed approach may enable the standardization of the fiducial point detection and the signal template generation. Meanwhile, the program-generated annotation data may serve as the labeled training set for the supervised machine learning.

Can Seismocardiogram Fiducial Points Be Used for the Routine Estimation of Cardiac Time Intervals in Cardiac Patients?

The indexes of cardiac mechanics can be derived from the cardiac time intervals, CTIs, i.e., the timings among the opening and closure of the aortic and mitral valves and the Q wave in the ECG. Traditionally, CTIs are estimated by ultrasound (US) techniques, but they may also be more easily assessed by the identification of specific fiducial points (FPs) inside the waveform of the seismocardiogram (SCG), i.e., the measure of the thorax micro-accelerations produced by the heart motion. While the correspondence of the FPs with the valve movements has been verified in healthy subjects, less information is available on whether this methodology may be routinely employed in the clinical practice for the monitoring of cardiac patients, in which an SCG waveform distortion is expected because of the heart dysfunction. In this study we checked the SCG shape in 90 patients with myocardial infarction (MI), heart failure (HF), or transplanted heart (TX), referred to our hospital for rehabilitation after an acute event or after surgery. The SCG shapes were classified as traditional (T) or non-traditional (NT) on whether the FPs were visible or not on the basis of nomenclature previously proposed in literature. The T shape was present in 62% of the patients, with a higher ∓ prevalence in MI (79%). No relationship was found between T prevalence and ejection fraction (EF). In 20 patients with T shape, we checked the FPs correspondence with the real valve movements by concomitant SCG and US measures. When compared with reference values in healthy subjects available in the literature, we observed that the Echo vs. FP differences are significantly more dispersed in the patients than in the healthy population with higher differences for the estimation of the mitral valve closure (−17 vs. 4 ms on average). Our results indicate that not every cardiac patient has an SCG waveform suitable for the CTI estimation, thus before starting an SCG-based CTI monitoring a preliminary check by a simultaneous SCG-US measure is advisable to verify the applicability of the methodology.

Left Ventricular Ejection Time Measured by Echocardiography Differentiates Neurobehavioral Resilience and Vulnerability to Sleep Loss and Stress

There are substantial individual differences (resilience and vulnerability) in performance resulting from sleep loss and psychosocial stress, but predictive potential biomarkers remain elusive. Similarly, marked changes in the cardiovascular system from sleep loss and stress include an increased risk for cardiovascular disease. It remains unknown whether key hemodynamic markers, including left ventricular ejection time (LVET), stroke volume (SV), heart rate (HR), cardiac index (CI), blood pressure (BP), and systemic vascular resistance index (SVRI), differ in resilient vs. vulnerable individuals and predict differential performance resilience with sleep loss and stress. We investigated for the first time whether the combination of total sleep deprivation (TSD) and psychological stress affected a comprehensive set of hemodynamic measures in healthy adults, and whether these measures differentiated neurobehavioral performance in resilient and vulnerable individuals. Thirty-two healthy adults (ages 27-53; 14 females) participated in a 5-day experiment in the Human Exploration Research Analog (HERA), a high-fidelity National Aeronautics and Space Administration (NASA) space analog isolation facility, consisting of two baseline nights, 39 h TSD, and two recovery nights. A modified Trier Social Stress Test induced psychological stress during TSD. Cardiovascular measure collection [SV, HR, CI, LVET, BP, and SVRI] and neurobehavioral performance testing (including a behavioral attention task and a rating of subjective sleepiness) occurred at six and 11 timepoints, respectively. Individuals with longer pre-study LVET (determined by a median split on pre-study LVET) tended to have poorer performance during TSD and stress. Resilient and vulnerable groups (determined by a median split on average TSD performance) showed significantly different profiles of SV, HR, CI, and LVET. Importantly, LVET at pre-study, but not other hemodynamic measures, reliably differentiated neurobehavioral performance during TSD and stress, and therefore may be a biomarker. Future studies should investigate whether the non-invasive marker, LVET, determines risk for adverse health outcomes.

Relationship Between the Ratio of Acceleration Time/Ejection Time and Mortality in Patients With High-Gradient Severe Aortic Stenosis

Background

The ratio of acceleration time/ejection time (AT/ET) is a simple and reproducible echocardiographic parameter that integrates aortic stenosis severity and its consequences on the left ventricle. No study has specifically assessed the prognostic impact of AT/ET on outcome in patients with high‐gradient severe aortic stenosis (SAS) and no or mild symptoms. We sought to evaluate the relationship between AT/ET and mortality and determine the best predictive AT/ET cutoff value in these patients.

Methods and Results

A total of 353 patients (median age, 79 years; 46% women) with high‐gradient (mean pressure gradient ≥40 mm Hg and/or aortic peak jet velocity ≥4 m/s) SAS, left ventricular ejection fraction ≥50%, and no or mild symptoms were studied. The impact of AT/ET ≤0.35 or >0.35 on all‐cause mortality was retrospectively studied. During a median follow‐up of 39 (25th–75th percentile, 23–62) months, 70 patients died. AT/ET >0.35 was associated with a considerable increased mortality risk after adjustment for established prognostic factors in SAS under medical and/or surgical management (adjusted hazard ratio [HR], 2.54; 95% CI, 1.47–4.37; P<0.001) or conservative management (adjusted HR, 3.29; 95% CI, 1.70–6.39; P<0.001). Moreover, AT/ET >0.35 improved the predictive performance of models including established risk factors in SAS with better global model fit, reclassification, and discrimination. After propensity matching, increased mortality risk persisted when AT/ET >0.35 (adjusted HR, 2.10; 95% CI, 1.12–3.90; P<0.001).

Conclusions

AT/ET >0.35 is a strong predictor of outcome in patients with SAS and no or only mild symptoms and identifies a subgroup of patients at higher risk of death who may derive benefit from earlier aortic valve replacement.

Novel Approach to Assess Cardiac Function Using Systolic Performance and Myocardial Performance Indices From Simultaneous Electrocardiography and Phonocardiography Recordings in Dogs With Various Stages of Myxomatous Mitral Valve Disease

Background and Objective: Myxomatous mitral valve disease (MMVD) progression entails changes in the structural and functional properties of the heart affecting cardiac timings and intervals within the cardiac cycle. Conventionally, echocardiography is used to determine the cardiac time intervals (CTIs) including systolic and myocardial performance indices (SPI and MPI) in evaluating cardiac function. Alternatively, these CTIs can also be measured using simultaneous recordings of electrocardiography (ECG) and phonocardiography (PCG), but their values in different MMVD stages remain to be established. This study aimed to establish and prove the use of derived SPI and MPI from a dedicated device as a novel approach to assess cardiac function in different stages of MMVD dogs. Materials and Methods: A prospective study in 52 dogs with different MMVD stages measured the CTIs using a novel device. These were compared and correlated with standard echocardiographic parameters. The predictive value of SPI and three new proposed formulas to estimate MPI (i.e., F1, F2, and F3) in association with asymptomatic from symptomatic MMVD dogs were investigated. Results: Our findings revealed that CTI parameters measured from a novel device including QS1, QS2, S1S2, MPI-F1, and MPI-F2 were altered at different stages of MMVD. The SPI and all proposed MPI formulas were comparable with the systolic time interval and Tei index from echocardiography. In addition, the SPI, MPI-F1, and MPI-F2 were significantly correlated with the Tei index. However, the SPI was not able to differentiate the various stages of MMVD. Conversely, only the MPI-F1 (i.e., (QS1 + S2)/S1S2) demonstrated good predictive accuracy when compared between asymptomatic and symptomatic MMVD dogs similar to the Tei index. Moreover, this formula was able to differentiate stages B1 and C with remarkable predictive accuracy, higher sensitivity, and high specificity when compared with the Tei index. Conclusion: We have successfully described the CTI parameters in different MMVD stages using simultaneous ECG and PCG recordings in dogs. Furthermore, we have proven that the concept of using the newly proposed parameters from a novel device is equivalent to the Tei index. Thus, we established a novel approach to evaluate cardiac function and its supportive use in the diagnosis of MMVD patients.

Longitudinal Association of Arterial Stiffness and Pressure Wave Reflection with Decline of the Cardiac Systolic Performance in Healthy Men

AIMS

This prospective observational study aimed to examine the individual longitudinal associations of the increases in the arterial stiffness and pressure wave reflection with the decline in the cardiac systolic performance during the study period in healthy middle-aged Japanese men.

METHODS

In 4016 middle-aged Japanese healthy men (43±9 years), the brachial-ankle pulse wave velocity (baPWV), radial augmentation index (rAI), and pre-ejection period/ejection time (pre-ejection period (PEP)/ET) were measured annually during a 9-year study period.

RESULTS

The baPWV, rAI, and PEP/ET showed steady annual increases during the study period. According to the results of multivariate linear regression analyses, both the baPWV and rAI measured at the baseline showed significant independent associations with the PEP/ET measured at the baseline (baPWV: beta=0.17, p＜0.01 and rAI: beta=0.11, p＜0.01), whereas neither showed any association with the PEP/ET measured at the end of the study period. The results of the mixed-model linear regression analysis of the repeated-measures data collected over the 9-year study period revealed that the baPWV, but not the rAI, showed a significant longitudinal association with the PEP/ET (estimate=0.69 x 10^－4, p＜0.01).

CONCLUSION

In apparently healthy middle-aged Japanese men, the annual increase of the arterial stiffness, rather than the annual increase of the pressure wave reflection, appears to be more closely associated with the annual decline of the cardiac systolic performance as assessed by the systolic time interval.

Duration of early systolic lengthening: prognostic potential in the general population

BACKGROUND

When the left ventricle pressure rises during early systole, myocardial fibres with reduced contractility tend to stretch instead of shortening. This interval is known as duration of early systolic lengthening (DESL). We sought to investigate if DESL provides prognostic information on cardiovascular events.

METHODS AND RESULTS

In this prospective study we included 1210 participants from a low-risk general population who underwent speckle tracking echocardiography (men 41%, mean age 56 years, SD 16). Primary endpoints were incident heart failure (HF), myocardial infarction (MI), and cardiovascular death (CVD). We defined DESL as time from onset of Q-wave on the electrocardiogram to peak positive systolic strain. In addition, we assessed the ratio between DESL and duration of cardiac systole, DESLsystole.During median follow-up of 16 years, 90 (7%) developed HF, 50 (4%) MI, and 70 (6%) experienced CVD. Both DESL [hazard ratio (HR) 1.58 95%CI 1.16-2.15, P = 0.004 per 10 ms increase] and DESLsystole (HR 1.74 95%CI 1.24-2.47, P = 0.001 per 1% increase) were predictors of HF. Similarly, DESL (HR 1.40 95%CI 1.09-1.78, P = 0.007 per 10 ms increase) and DESLsystole (HR 1.58 95%CI 1.01-2.49, P = 0.047 per 1% increase) were predictors of MI. No associations were found with CVD. After adjusting for clinical and echocardiographic parameters, the associations remained significant. DESLsystole was superior to systolic echocardiographic parameters for predicting HF (P = 0.012).

CONCLUSION

DESL and the novel index of DESLsystole provide independent and novel prognostic information on the risk of HF and MI in the general population. Evaluation of DESL should be explored in future echocardiographic studies.

AI-Based Estimation of End-Systolic Elastance From Arm-Pressure and Systolic Time Intervals

Left ventricular end-systolic elastance (E_es) is a major determinant of cardiac systolic function and ventricular-arterial interaction. Previous methods for the E_es estimation require the use of the echocardiographic ejection fraction (EF). However, given that EF expresses the stroke volume as a fraction of end-diastolic volume (EDV), accurate interpretation of EF is attainable only with the additional measurement of EDV. Hence, there is still need for a simple, reliable, noninvasive method to estimate E_es. This study proposes a novel artificial intelligence—based approach to estimate E_es using the information embedded in clinically relevant systolic time intervals, namely the pre-ejection period (PEP) and ejection time (ET). We developed a training/testing scheme using virtual subjects (n = 4,645) from a previously validated in-silico model. Extreme Gradient Boosting regressor was employed to model E_es using as inputs arm cuff pressure, PEP, and ET. Results showed that E_es can be predicted with high accuracy achieving a normalized RMSE equal to 9.15% (r = 0.92) for a wide range of E_es values from 1.2 to 4.5 mmHg/ml. The proposed model was found to be less sensitive to measurement errors (±10–30% of the actual value) in blood pressure, presenting low test errors for the different levels of noise (RMSE did not exceed 0.32 mmHg/ml). In contrast, a high sensitivity was reported for measurements errors in the systolic timing features. It was demonstrated that E_es can be reliably estimated from the traditional arm-pressure and echocardiographic PEP and ET. This approach constitutes a step towards the development of an easy and clinically applicable method for assessing left ventricular systolic function.

The significance of left ventricular ejection time in heart failure with reduced ejection fraction

Left ventricular ejection time (LVET) is defined as the time interval from aortic valve opening to aortic valve closure, and is the phase of systole during which the left ventricle ejects blood into the aorta. LVET has been used for several decades to assess left ventricular function and contractility. However, there is a recent interest in LVET as a measure of therapeutic action for novel drugs in patients with heart failure with reduced ejection fraction (HFrEF), since LVET is shortened in these patients. This review provides an overview of the available information on LVET including methods of measuring LVET, mechanistic understanding of LVET, association of LVET with outcomes, mechanisms behind shortened LVET in HFrEF and the potential implications of drugs that affect and normalize LVET.

Mediation of Arterial Stiffness for Hyperuricemia-Related Decline of Cardiac Systolic Function in Healthy Men

Background: This prospective observational study examined whether hyperuricemia may be associated with impaired left ventricular (LV) systolic function and increased cardiac load resulting from increased arterial stiffness.

Methods and Results: In 1,880 middle-aged (mean [±SD] age 45±9 years) healthy men, serum uric acid (UA) levels, pre-ejection period/ejection time (PEP/ET) ratio, serum N-terminal pro B-type natriuretic peptide (NT-proBNP) levels, and brachial-ankle pulse wave velocity (baPWV) were measured at the start and end of the 3-year study period. Linear regression analysis revealed that serum UA levels measured at baseline were significantly associated with the PEP/ET ratio, but not with serum NT-proBNP levels, measured at baseline (β=0.73×10⁻¹, P<0.01) and at the end of the study period (β=0.68×10⁻¹, P<0.01). The change in the PEP/ET ratio during the study period was significantly greater in the High-UA (UA >7 mg/dL in 2009 and 2012) than Low-UA (UA ≤7 mg/dL in 2009 and 2012) group. Mediation analysis demonstrated both direct and indirect (via increases in baPWV) associations between serum UA measured at baseline and the PEP/ET ratio measured at the end of the study period.

Conclusions: In healthy middle-aged Japanese men, hyperuricemia may be associated with an accelerated decline in ventricular systolic function, both directly and indirectly, via increases in arterial stiffness.

Automativ assessment of systolic cardiac performance using PEP/LVET index

Congestive cardiac failure is one of the deadliest diseases in the world, with more than 26 million patients. Echocardiogram and angiography consider as the gold standards for heart failure diagnosis. Nevertheless, they are not commonly used for long-term follow up as they need highly skilled and experienced operator. In this paper, a simple and low-cost system for automatic assessment of systolic cardiac performance using systolic cardiac intervals is presented. The proposed system utilized electrocardiogram (ECG) and phonocardiogram (PCG) to calculate pre-ejection period (PEP) and left ventricle ejection time (LVET). The ratio between PEP and LVET was computed to assess the performance of the systolic cardiac function. ECG and PCG were acquired using a commercial stethoscope which was modified to convert PCG auscultation to electrical signals. ECG and PCG signals were digitized and transferred to a personal computer. A custom MATLAB application was designed to display the acquired ECG and PCG, and to compute PEP, LVET, and PEP/LVET ratio. The system was tested on 17 healthy subjects and results showed high agreement between the systolic heart function status assessed by the proposed system and the corresponding echocardiography results. These results imply that the proposed system could be used for long-term follow up for patients with congestive heart failure.

Gyrocardiography: A Review of the Definition, History, Waveform Description, and Applications

Gyrocardiography (GCG) is a non-invasive technique of analyzing cardiac vibrations by a MEMS (microelectromechanical system) gyroscope placed on a chest wall. Although its history is short in comparison with seismocardiography (SCG) and electrocardiography (ECG), GCG becomes a technique which may provide additional insight into the mechanical aspects of the cardiac cycle. In this review, we describe the summary of the history, definition, measurements, waveform description and applications of gyrocardiography. The review was conducted on about 55 works analyzed between November 2016 and September 2020. The aim of this literature review was to summarize the current state of knowledge in gyrocardiography, especially the definition, waveform description, the physiological and physical sources of the signal and its applications. Based on the analyzed works, we present the definition of GCG as a technique for registration and analysis of rotational component of local cardiac vibrations, waveform annotation, several applications of the gyrocardiography, including, heart rate estimation, heart rate variability analysis, hemodynamics analysis, and classification of various cardiac diseases.

Identification of the Vibrations Corresponding with Heart Sounds using Vibrational Cardiography

Cardiography enables diagnostic and preventive care in hospitals and outpatient scenarios. However, most heart monitors do not distinguish the phases of the cardiac cycle. The transition between phases is indicated by the primary heart sounds.

OBJECTIVE

Automatically identify the vibrations corresponding to both heart sounds.

METHODS

Cardiac activity was monitored for 15 subjects while at rest, during exertion, and while performing static breath holds. The subjects consisted of 6 males and 9 females between the ages of 18-39 years with no known cardiorespiratory ailments. Motion corresponding to the heart sounds was identified using vibrational cardiography (VCG). The waveforms were processed to obtain quantities associated with their linear jerk and rotational kinetic energy.

RESULTS

The ability to identity the first vibration was evaluated using the heart rate as a figure of merit. Its correlation with electrocardiography (ECG) measurements produced a r² coefficient of 0.9887. The second vibration was compared with impedance cardiography (ICG) based on its delay from the ECG R-peak, and the fraction of the beat duration occupied by left ventricular ejection time. The comparisons produced r² values of 0.251 and 0.2797, respectively.

CONCLUSION

The vibrations corresponding to both primary heart sounds have the potential to be analyzed using VCG.

SIGNIFICANCE

This study provides evidence of the feasibility of using VCG in identifying mechanical cardiovascular function. It facilitates non-invasive cardiac health monitoring in daily life.

Evaluation of Carotid Flow Time to Assess Fluid Responsiveness in the Emergency Department

Background:

Assessing fluid responsiveness in critically ill patients is challenging. Objective, noninvasive tests that are easy to perform are needed. Doppler measurements of dynamic carotid artery parameters such as carotid blood flow (CBF) and carotid flow time (CFT) are being studied as the potential indicators of volume responsiveness, but the data supporting its use are sparse.

Methods:

This prospective, observational study was conducted in the adult emergency department from June to September 2018. Patients who were prescribed a bolus of 500 ml of crystalloid for any indication were enrolled. Carotid Doppler was performed before and after a fluid bolus to measure the change in CBF and CFT. The aim of our study was to determine if CFT can be used as a marker of fluid responsiveness.

Results:

During the 4-month study period, 209 patients were recruited through convenient sampling after obtaining informed written consent. 29.6% of patients presented with a mean arterial pressure (MAP) <65, among whom 58.1% had septic shock. The baseline CBF was 643.0 ± 212.7 ml/min, and it was 583.9 ± 207.1 ml/min and 668 ± 210.8 ml/min in hypotensive and normotensive patients, respectively. Considering a >10% increase in CBF as fluid response, there were 59% responders and 41% nonresponders. The MAP increased by 9.5% in the responders, while there was no significant change in CFT after the fluid bolus. There was no difference in CFT among the responders as compared to the nonresponders. There was no correlation between the change of CBF and CFT (r^[207] = 0.013, P = 0.061) after the fluid bolus.

Conclusion:

Though easy to perform, CFT is probably not a good indicator of fluid responsiveness.

Noninvasive estimation of aortic hemodynamics and cardiac contractility using machine learning

Cardiac and aortic characteristics are crucial for cardiovascular disease detection. However, noninvasive estimation of aortic hemodynamics and cardiac contractility is still challenging. This paper investigated the potential of estimating aortic systolic pressure (aSBP), cardiac output (CO), and end-systolic elastance (E_es) from cuff-pressure and pulse wave velocity (PWV) using regression analysis. The importance of incorporating ejection fraction (EF) as additional input for estimating E_es was also assessed. The models, including Random Forest, Support Vector Regressor, Ridge, Gradient Boosting, were trained/validated using synthetic data (n = 4,018) from an in-silico model. When cuff-pressure and PWV were used as inputs, the normalized-RMSEs/correlations for aSBP, CO, and E_es (best-performing models) were 3.36 ± 0.74%/0.99, 7.60 ± 0.68%/0.96, and 16.96 ± 0.64%/0.37, respectively. Using EF as additional input for estimating E_es significantly improved the predictions (7.00 ± 0.78%/0.92). Results showed that the use of noninvasive pressure measurements allows estimating aSBP and CO with acceptable accuracy. In contrast, E_es cannot be predicted from pressure signals alone. Addition of the EF information greatly improves the estimated E_es. Accuracy of the model-derived aSBP compared to in-vivo aSBP (n = 783) was very satisfactory (5.26 ± 2.30%/0.97). Future in-vivo evaluation of CO and E_es estimations remains to be conducted. This novel methodology has potential to improve the noninvasive monitoring of aortic hemodynamics and cardiac contractility.

Left ventricular output indices in hospitalized heart failure: when "simpler" may not mean "better"

Assessment of left ventricular (LV) output in hospitalized patients with heart failure (HF) is important to determine prognosis. Although echocardiographic LV ejection fraction (EF) is generally used to this purpose, its prognostic value is limited. In this investigation LV-EF was compared with other echocardiographic per-beat measures of LV output, including non-indexed stroke volume (SV), SV index (SVI), stroke distance (SD), ejection time (ET), and flow rate (FR), to determine the best predictor of all-cause mortality in patients hospitalized with HF. A final cohort of 350 consecutive patients hospitalized with HF who underwent echocardiography during hospitalization was studied. At a median follow-up of 2.7 years, 163 patients died. Non-survivors at follow-up had lower SD, SVI and SV, but not ET, FR and LV-EF than survivors. At multivariate analysis, only age, systolic blood pressure, chronic kidney disease, chronic obstructive pulmonary disease, use of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers and SVI remained significantly associated with outcome [HR for SVI 1.13 (1.04-1.22), P = 0.003]. In particular, for each 5 ml/m² decrease in SVI, a 13% increase in risk of mortality for any cause was observed. SVI is a powerful prognosticator in HF patients, better than other per-beat measures, which may be simpler but partial or incomplete descriptors of LV output. SVI, therefore, should be considered for the routine echocardiographic evaluation of patients hospitalized with HF to predict prognosis.

Association between systolic ejection time and outcomes in heart failure by ejection fraction

AIMS

Worsening heart failure (HF) is associated with shorter left ventricular systolic ejection time (SET), but there are limited data describing the relationship between SET and clinical outcomes. Thus, the objective was to describe the association between SET and clinical outcomes in an ambulatory HF population irrespective of ejection fraction (EF).

METHODS AND RESULTS

We identified ambulatory patients with HF with reduced EF (HFrEF) and HF with preserved EF (HFpEF) who had an outpatient transthoracic echocardiogram performed between August 2008 and July 2010 at a tertiary referral centre. Multivariable logistic regression was used to evaluate the association between SET and 1-year outcomes. A total of 545 HF patients (171 HFrEF, 374 HFpEF) met eligibility criteria. Compared with HFpEF, HFrEF patients were younger [median age 60 years (25th-75th percentiles 50-69) vs. 64 years (25th-75th percentiles 53-74], with fewer females (30% vs. 56%) and a similar percentage of African Americans (36% vs. 35%). Median (25th-75th percentiles) EF with HFrEF was 30% (25-35%) and with HFpEF was 54% (48-58%). Median SET was shorter (280 ms vs. 315 ms, P < 0.001), median pre-ejection period was longer (114 ms vs. 89 ms, P < 0.001), and median relaxation time was shorter (78.7 ms vs. 93.3 ms, P < 0.001) among patients with HFrEF vs. HFpEF. Death or HF hospitalization occurred in 26.9% (n = 46) HFrEF and 11.8% (n = 44) HFpEF patients. After adjustment, longer SET was associated with lower odds of the composite of death or HF hospitalization at 1 year among HFrEF but not HFpEF patients.

CONCLUSION

Longer SET is independently associated with improved outcomes among HFrEF patients but not HFpEF patients, supporting a potential role for normalizing SET as a therapeutic strategy with systolic dysfunction.

Investigating the estimation of cardiac time intervals using gyrocardiography

OBJECTIVE

Assessment of cardiac time intervals (CTIs) is essential for monitoring cardiac performance. Recently, gyrocardiography (GCG) has been introduced as a non-invasive technology for cardiac monitoring. GCG measures the chest's angular precordial vibrations caused by myocardium wall motion using a gyroscope sensor attached to the sternum. In this study, we investigated the accuracy and reproducibility of estimating CTIs from the GCG recordings of 50 adults.

APPROACH

We proposed five fiducial points for the GCG waveforms associated with the opening and closure of aortic and mitral valves. Two annotators annotated the suggested points on each cardiac cycle. The points were compared to the corresponding opening and closing of cardiac valves delineated on Tissue Doppler imaging (TDI) recordings. The fiducial points were annotated on seismocardiography (SCG) and impedance cardiography (ICG) signals recorded simultaneously.

MAIN RESULTS

For estimating the timing of mitral valve closure, aortic valve opening, aortic valve closure, and mitral valve opening, 40%, 67%, 75%, and 70% of GCG annotations fell in the corresponding echocardiography ranges, respectively. The results showed moderate-to-excellent (r = 0.4-0.92; p-value < 0.01) correlation between the measured and the reference CTls. A myocardial performance index (Tei index) adapted using joint GCG and SCG resulted in a moderate correlation (r = 0.4; p-value < 0.001).

SIGNIFICANCE

The findings showed that the CTIs can be easily measured using GCG. Also, we found that using SCG and GCG recordings together could provide an opportunity to estimate CTIs more accurately, and make it possible to calculate the Tei index as an indicator of myocardial performance.

The right ventricular myocardial systolic-to-diastolic duration ratio in children after surgical repair of Tetralogy of Fallot

Right ventricular (RV) function impacts clinical outcomes after surgical repair of Tetralogy of Fallot (rTOF). However, assessment of RV function remains difficult. We investigated the RV myocardial systolic-to-diastolic (S/D) duration ratio derived from strain imaging time intervals to characterize RV myocardial performance, exploring its relation with peak oxygen consumption during exercise (V̇o₂) and cardiac magnetic resonance-derived RV dilation and function in rTOF. We retrospectively analyzed 76 children with rTOF and 42 normal controls. The RV myocardial S/D duration ratio was measured from RV global and regional 2D speckle tracking longitudinal strain. Time from QRS onset to peak systolic strain was defined as the systolic duration. The S/D duration ratio was calculated and corrected for heart rate (HR). Postsystolic shortening (PSS) duration was defined as shortening time after cessation of pulmonary systolic antegrade flow. The RV myocardial S/D duration ratio, corrected or uncorrected for HR, was significantly higher in rTOF vs. controls (1 ± 0.3 vs. 0.8 ± 0.2, P = 0.004) in relation to prolonged PSS. The HR-corrected myocardial S/D duration ratio correlated weakly with RV ejection fraction (EF, r = -0.37, P = 0.001) and V̇o₂ (r = -0.32, P = 0.042). In multiregression analysis, RV EF was independently associated with the myocardial S/D duration ratio. The RV myocardial S/D duration ratio is a parameter of RV myocardial performance and efficiency, incorporating elements of systolic and diastolic performance, mechanical dyssynchrony, and PSS. The S/D duration ratio is associated with exercise capacity and RV dysfunction in rTOF.NEW & NOTEWORTHY This is the first study to assess right ventricular myocardial performance using the systolic-to-diastolic duration ratio derived from 2D strain. Seventy-six children with repaired Tetralogy of Fallot were evaluated. Echocardiographic data were correlated with cardiac magnetic resonance and peak oxygen consumption during exercise. The results show the right ventricular myocardial systolic-to-diastolic duration ratio incorporates systolic and diastolic performance, electromechanical dyssynchrony, and postsystolic shortening and is associated with exercise capacity in repaired Tetralogy of Fallot.

Acute correction of electromechanical dyssynchrony and response to cardiac resynchronization therapy

Aims

Echocardiographic measures of dyssynchrony at baseline have not demonstrated a good ability to predict response to cardiac resynchronization therapy (CRT). The purpose of this study was to determine if the acute correction of electromechanical dyssynchrony, assessed by the change in simple pulsed‐Doppler measures, was related to CRT response at 6 months.

Methods and results

Echocardiography was performed at baseline and at pre‐discharge after CRT implantation. Intraventricular, interventricular, and atrioventricular dyssynchrony were evaluated by the left pre‐ejection interval (LPEI), the interventricular mechanical delay, and the ratio of left ventricular filling time to RR interval, respectivelxy. A patient was considered responder if he/she was alive without hospitalization for heart failure and had an absolute increase of left ventricular ejection fraction (LVEF) >5 points. Forty‐eight patients (mean age 67 ± 11 years, 73% male, mean LVEF 30 ± 5%) were included. CRT led to an acute correction of intraventricular and interventricular dyssynchrony but not to an acute correction of atrioventricular dyssynchrony. There were 31 (65%) responders at 6 months. Two factors were independently associated with CRT response in multivariate analysis: ischemic cardiomyopathy (odds ratio 0.19, 95% confidence interval 0.04–0.87; P= 0.032) and delta LPEI (odds ratio 1.03 per 1 ms decrease, 95% confidence interval 1.01–1.05; P = 0.007). By receiver operating characteristic analysis, the optimal cut‐off value of delta LPEI was −16 ms. The proportion of responders in patients without ischemic cardiomyopathy and with a delta LPEI greater than −16 ms was 85%.

Conclusions

Acute correction of intraventricular electromechanical dyssynchrony evaluated by the LPEI predicted CRT response at 6 months.

The repeatability of estimated systolic time intervals in healthy subjects using seismocardiogram and electrocardiogram

OBJECTIVE

We investigated the repeatability of systolic time intervals (STIs) in healthy subjects using a combination of seismocardiogram (SCG) and electrocardiogram (ECG). STIs have been extensively used in the past to quantify heart performance, particularly the left ventricle. In this study, STIs included pre-ejection period (PEP), left ventricular ejection time (LVET), and their ratio.

APPROACH

We conducted the repeatability test of STI estimation through two experiments. The first involved three consecutive one-minute recordings separated by one-minute intervals, and the second involved two one-minute recordings separated by 24 h. Twenty healthy subjects participated in our study. We considered the coefficient of variation (CV) to quantify the repeatability. As there was no agreed upon values for optimal CV values, we compared our results with an alternative method using a combination of impedance cardiography (ICG) and ECG. Similar to our method, the alternative method was noninvasive and could be employed for personal heart monitoring. We also studied the repeatability after STIs were corrected for heart rate using two approaches. The first approach used a multiplicative factor per subject based on the heart rates in each recordings of that subject. The second approach employed sex-specific regression models for all subjects (Weissler's equations).

MAIN RESULTS

We found that the repeatability of our method (SCG and ECG) was in agreement with the alternative method (ICG and ECG) in both experiments. Moreover, the Weissler's equations approach for heart rate increased the repeatability.

SIGNIFICANCE

It can be concluded that estimation of PEP, LVET and their ratio through SCG and ECG signals was repeatable in healthy subjects.

Estimation of Beat-to-Beat Interval and Systolic Time Intervals Using Phono- and Seismocardiograms

Systolic time intervals Pre-Ejection Period (PEP) and Left Ventricular Ejection Time (LVET) are widely used indicators of cardiac functions. While accurate assessment of them requires costly equipment such as echocardiography devices, a satisfactory estimation can be done by analyzing signals from simple accelerometer and microphone attached to human chest. This paper reports a study where heart rate and the systolic intervals were derived from phonocardiogram (PCG) and seismocardiogram (SCG) simultaneously. Both sensors, the microphone for PCG and the accelerometer for SCG were attached on the chest wall, close to sternum (PCG) and apex of the heart (SCG). The signals were acquired from 10 participants in a 33-minute laboratory protocol with synchronized ECG measurements. Both signals went through an identical processing path: band pass filtering, envelope extraction with Hilbert transformation and peak detection from the envelope signal. In heart rate estimation, PCG and SCG reached 84% and 93% accuracy, respectively. The systolic interval accuracy estimation was based on deviation analysis as the absolute reference values for PEP and LVET were not available. In PEP estimation, the average standard deviations during the rest periods of the protocol were 4 ms for PCG and 8 ms for SCG. In LVET estimation, the deviations were nearly 10 fold compared to PEP. However, the results show that both methods can be used for accurate heart rate estimation and with careful mechanical attachment also PEP can be accurately derived from both. Due to sharper envelope signal waveform, PEP estimation was more accurate with PCG than with SCG.

Long-Term Hemodynamic Improvement after Transcatheter Mitral Valve Repair

BACKGROUND

Correction of mitral regurgitation (MR) alters the load on the left ventricle. There are few data on the long-term hemodynamic adaptations of the cardiovascular system after transcatheter mitral valve repair (TMVR). The aim of this study was to determine a comprehensive hemodynamic status using noninvasive pressure-volume analysis.

METHODS

Pressure-volume parameters were calculated from echocardiography with simultaneous arm-cuff blood pressure measurements at baseline before TMVR and 12 months after TMVR. Eighty-eight consecutive patients undergoing edge-to-edge mitral clip implantation because of grade 3+ or 4+, symptomatic (79.5% in New York Heart Association functional class ≥III) MR were prospectively enrolled. The mean left ventricular (LV) ejection fraction was 42 ± 14%. Sixty-seven percent of the patients had secondary MR.

RESULTS

Twelve months after TMVR, 17.7% of patients had died, and 19.0% were rehospitalized because of decompensated heart failure. MR grade was ≤2+ in 90% of surviving patients, and 77% were in New York Heart Association functional class ≤II. LV end-diastolic volume index decreased from 87 ± 38 to 77 ± 40 mL/m² (P < .0001), end-systolic volume index changed from 54 ± 34 to 50 ± 36 mL/m² (P = .018), hence total stroke volume index was reduced (from 34 ± 11 to 28 ± 7 ml/m², P < .0001). Ejection fraction and global longitudinal peak systolic strain remained unchanged. Increased forward ejection fraction (30 ± 14% vs 41 ± 20%, P < .0001), cardiac index (from 1.7 ± 0.4 to 1.9 ± 0.5 mL/min/m², P = .003), and peak power index (214 ± 114 vs 280 ± 149 mm Hg/sec, P = .0001) as well as similar end-systolic elastance at reduced LV volumes indicated improved LV performance. Cardiac efficiency, measured as cardiac index relative to myocardial energy, was improved (0.012 ± 0.008 vs 0.019 ± 0.010 mm Hg^-1, P = .002). Logistic regression analysis revealed baseline values of total ejection fraction and diastolic pulmonary pressure gradient as predictors of clinical improvement (odds ratios, 1.076 [P = .009] and 0.812 [P = .015], respectively) after TMVR.

CONCLUSIONS

One year after TMVR, patients showed reverse remodeling and improved LV performance that was associated with improved symptom status. This hemodynamic improvement supports TMVR as long-term effective therapy for patients with symptomatic MR.

Modeling arterial pulse waves in healthy aging: a database for in silico evaluation of hemodynamics and pulse wave indexes

The arterial pulse wave (PW) is a rich source of information on cardiovascular (CV) health. It is widely measured by both consumer and clinical devices. However, the physical determinants of the PW are not yet fully understood, and the development of PW analysis algorithms is limited by a lack of PW data sets containing reference CV measurements. Our aim was to create a database of PWs simulated by a computer to span a range of CV conditions, representative of a sample of healthy adults. The typical CV properties of 25-75 yr olds were identified through a literature review. These were used as inputs to a computational model to simulate PWs for subjects of each age decade. Pressure, flow velocity, luminal area, and photoplethysmographic PWs were simulated at common measurement sites, and PW indexes were extracted. The database, containing PWs from 4,374 virtual subjects, was verified by comparing the simulated PWs and derived indexes with corresponding in vivo data. Good agreement was observed, with well-reproduced age-related changes in hemodynamic parameters and PW morphology. The utility of the database was demonstrated through case studies providing novel hemodynamic insights, in silico assessment of PW algorithms, and pilot data to inform the design of clinical PW algorithm assessments. In conclusion, the publicly available PW database is a valuable resource for understanding CV determinants of PWs and for the development and preclinical assessment of PW analysis algorithms. It is particularly useful because the exact CV properties that generated each PW are known.NEW & NOTEWORTHY First, a comprehensive literature review of changes in cardiovascular properties with age was performed. Second, an approach for simulating pulse waves (PWs) at different ages was designed and verified against in vivo data. Third, a PW database was created, and its utility was illustrated through three case studies investigating the determinants of PW indexes. Fourth, the database and tools for creating the database, analyzing PWs, and replicating the case studies are freely available.

Possible Mechanisms Underlying Elevated Serum N-Terminal Pro-Brain Natriuretic Peptide in Healthy Japanese Subjects

Background: The precise mechanisms underlying elevation of serum N-terminal pro-brain natriuretic peptide (NT-proBNP) in healthy subjects have not been fully clarified.

Methods and Results: In 2,844 Japanese healthy subjects with serum NT-proBNP <125 pg/mL, (1) brachial-ankle pulse wave velocity and (2) second peak of the peripheral systolic blood pressure minus diastolic blood pressure (pulse pressure 2 [PP2]), as markers of cardiac afterload; (3) fibrosis 4 score (FIB-4 score, a marker of liver fibrosis), as a marker of cardiac preload; and (4) ratio of the pre-ejection time to ejection time (PEP/ET), as a marker of cardiac systolic function, were measured. At the first examination, after the adjustments, log-transformed serum NT-proBNP was associated with PP2 and FIB-4 score, but not with PEP/ET. These parameters were successfully measured again after a 3-year interval in 1,978 subjects. On Pearson’s correlation analysis, change in PP2 and FIB-4 score during the study period was significantly correlated with change in serum NT-proBNP (r=0.05, 0.09, respectively; P<0.01).

Conclusions: In apparently healthy Japanese subjects, both increased cardiac preload and increased cardiac afterload, but not impaired cardiac systolic function, may be associated with elevated serum NT-proBNP.

Comparison of Different Methods for Estimating Cardiac Timings: A Comprehensive Multimodal Echocardiography Investigation

Cardiac time intervals are important hemodynamic indices and provide information about left ventricular performance. Phonocardiography (PCG), impedance cardiography (ICG), and recently, seismocardiography (SCG) have been unobtrusive methods of choice for detection of cardiac time intervals and have potentials to be integrated into wearable devices. The main purpose of this study was to investigate the accuracy and precision of beat-to-beat extraction of cardiac timings from the PCG, ICG and SCG recordings in comparison to multimodal echocardiography (Doppler, TDI, and M-mode) as the gold clinical standard. Recordings were obtained from 86 healthy adults and in total 2,120 cardiac cycles were analyzed. For estimation of the pre-ejection period (PEP), 43% of ICG annotations fell in the corresponding echocardiography ranges while this was 86% for SCG. For estimation of the total systolic time (TST), these numbers were 43, 80, and 90% for ICG, PCG, and SCG, respectively. In summary, SCG and PCG signals provided an acceptable accuracy and precision in estimating cardiac timings, as compared to ICG.

Echocardiographic assessment of left ventricular systolic function in neonatal calves with naturally occurring sepsis or septic shock due to diarrhea

Sepsis is associated with clinically relevant cardiovascular changes. The objectives of this study were to evaluate the clinical value of echocardiography for monitoring left ventricular (LV) systolic function in septic calves. A prospective longitudinal study was performed using a convenience sample. Twenty septic calves and 10 healthy calves were enrolled in the study. Arterial blood pressure (BP) was measured and M-mode echocardiography performed to characterize LV systolic function; the latter included measurement of ejection fraction, EF; stroke volume, SVI and cardiac output indexed to body weight, CI; E-point of septal separation, EPSS; pre-ejection period, PEP; ejection time, LVET; ratio of PEP to LVET; velocity of circumferential shortening, Vcf, LV end-diastolic volume index (LVEDVI) and LV end-systolic volume index (LVESVI) on admission and 6, 24, 48 and 72 h later in septic calves and once in healthy calves. Admission data were compared using the Mann-Whitney U test and P < .05 was considered significant. Decreased preload and afterload were present in septic calves, as indicated by marked decreases in BP, LVEDVI, LVESVI, SVI, CI, EPSS when compared to healthy calves. Systolic function appeared adequate in septic calves, based on EF and FS compared to control calves. There was no difference in heart rate, LVET, PEP:LVET, or Vcf between septic and health calves. We conclude that circulatory dysfunction, rather than systolic dysfunction predominates in septic calves. Positive associations on admission between CI and LVEDVI, LVESVI, and SVI support this conclusion. Echocardiographic determination of LVEDVI and CI appears useful in directing treatment in septic calves.

Age related structural and functional changes in left ventricular performance in healthy subjects: a 2D echocardiographic study

Left ventricular (LV) adaptation to aging is currently poorly understood. We aimed to characterize age related changes in LV structure and function by studying a large group of healthy subjects across a wide age range. Prospectively enrolled healthy volunteers (n = 778, 327 females; age 18 to 100 years, mean age 49.8 ± 18.1 years), were divided into 4 age groups: 18 to 34 years (n = 165); 35 to 49 years (n = 242), 50 to 79 years (n = 334) and ≥ 80 years (n = 40). All subjects underwent clinical examination, as well as comprehensive transthoracic echocardiogram [TTE]. Body mass index, systolic blood pressure (BP), and left atrial volume (p < 0.0001) increased with age while diastolic BP (p < 0.0001) decreased over time. LV mass/body surface area (BSA) and relative wall thickness increased with age (p < 0.0001) coincident with worsening parameters of diastolic function (E/A and E/Em, p < 0.0001). The ejection fraction and Sm did not change significantly. Stroke volume, ejection time index, flow rate and stroke work significantly increased with age (p < 0.01). The arterial elastance (Ea), a measure of ventricular afterload, and ventricular elastance (Ees), an index of LV systolic stiffness did not change with age nor did their ratio (Ees/Ea) the latter being an expression of ventricular-arterial coupling. Age, gender and LVM were the main independent variables associated with LV systolic function. In conclusion, LV adaptation to aging in a healthy cohort is characterized by concentric LV remodeling, increased contractility and preserved ventricular-arterial coupling.

Right ventricular total isovolumic time: Reference value study

BACKGROUND

There is lack of noninvasive indices to detail the right side cardiovascular physiology. Total isovolumic time (tIVT) is a sensitive marker of left ventricular electromechanical efficiency and systolic-diastolic interaction. The aim of the study was to evaluate normal reference value of the right ventricular tIVT with increasing age.

METHODS AND RESULTS

One hundred and eighty-one healthy volunteers (51% male) underwent transthoracic echocardiography. The population was divided into four categories according to age: A < 30 years; B 30-39 years; C 40-49 years; and C ≥ 50 years old. tIVT was computed in seconds/minutes as: 60 - (tET + tFT). tET and tFT are the total ejection and filling time adjusted by the heart rate, measured, respectively, from the onset to the end of the right ventricle (RV) forward flow through the pulmonary valve and from the onset of the E-wave and the end of the A-wave at the level of the tricuspid valve. The mean RV tIVT was 7 ± 1.1 s/min and increased significantly with age, from a 3.4 to 9.7 s/min(P < 0.0001). Significant correlation was found between tIVT and trans-tricuspid E/E' (P < 0.0001; 0.78 (95% CI: 0.715-0.831) while weaker between tIVT and E/A (P = 0.001; -0.283 95% CI: -0.413 to -0.143).

CONCLUSION

The normal values of RV tIVT increase with age and correlate significantly with Doppler diastolic parameters.

P wave peak time: A time window to evaluate left ventricular diastolic function

The activation time from electrical signals to chamber conformational change has long been demonstrated to associate with LV performance and ventriculo-arterial coupling with prognostic implications in heart failure patients. P wave peak time (PWPT), an easily obtainable parameter from conventional surface electrocardiography, represents the time taken for excitation spreading from sinoatrial node to the maximal summation of positive deflection from both atria. Increased PWPT denotes prolonged intra- or inter-atrial conduction time and indicates elevated intra-atrial pressure. As shown in a recently published study, PWPT was highly correlated with LV end diastolic pressure (LVEDP) derived from direct measurement during cardiac catheterization. With its objective and easily obtainable nature, clinical application of PWPT to evaluate diastolic function can be expected, if more studies in different populations can confirm its clinical utility.

Realization and Technology Acceptance Test of a Wearable Cardiac Health Monitoring and Early Warning System with Multi-Channel MCGs and ECG

In this work, a wearable smart clothing system for cardiac health monitoring with a multi-channel mechanocardiogram (MCG) has been developed to predict the myo-cardiac left ventricular ejection fraction (LVEF) function and to provide early risk warnings to the subjects. In this paper, the realization of the core of this system, i.e., the Cardiac Health Assessment and Monitoring Platform (CHAMP), with respect to its hardware, firmware, and wireless design features, is presented. The feature values from the CHAMP system have been correlated with myo-cardiac functions obtained from actual heart failure (HF) patients. The usability of this MCG-based cardiac health monitoring smart clothing system has also been evaluated with technology acceptance model (TAM) analysis and the results indicate that the subject shows a positive attitude toward using this wearable MCG-based cardiac health monitoring and early warning system.

Systolic time intervals assessed from analysis of the carotid pressure waveform

OBJECTIVE

The timing of mechanical cardiac events is usually evaluated by conventional echocardiography as an index of cardiac systolic function and predictor of cardiovascular outcomes. We aimed to measure the systolic time intervals, namely the isovolumetric contraction time (ICT) and pre-ejection period (PEP), by arterial tonometry.

APPROACH

Sixty-two healthy volunteers (age 47  ±  17 years) and 42 patients with heart failure and reduced ejection fraction were enrolled (age 66  ±  14 years). Pulse waves were recorded at the carotid artery by arterial tonometry together with simultaneous aortic transvalvular flow by Doppler-echocardiography, synchronized by electrocardiographic gating. The ICT was determined from the time delay between the electrical R wave and the carotid pressure waveform, after adjustment for the pulse transit time from the aortic valve to the carotid artery site, estimated by an algorithm based on the carotid-femoral pulse wave velocity. The PEP was evaluated by adding the electrical QR duration to the ICT.

MAIN RESULTS

The ICT derived from carotid pulse wave analysis was closely related to that measured by echocardiography (r  =  0.90, p  <  0.0001), with homogeneous distribution in Bland-Altman analysis (mean difference and 95% confidence interval  =  0.2 from  -14.2 to 14.5 ms). ICT and PEP were higher in cardiac patients than in healthy volunteers (p  <  0.0001). The ratio between PEP and left ventricular ejection time was related to the ejection fraction measured with echocardiography (r  =  0.555, p  <  0.0001).

SIGNIFICANCE

The timing of electro-mechanical cardiac events can be reliably obtained from the carotid pulse waveform and carotid-femoral PWV, evaluated using arterial tonometry. Systolic time intervals assessed with this approach showed good agreement with measurements performed with conventional echocardiography and may represent a promising additional application of arterial tonometry.