HOUSTON, TX, United States
HOUSTON, TX, United States

Time filter

Source Type

Grimes K.M.,University of Texas Health Science Center at San Antonio | Reddy A.K.,Baylor College of Medicine | Reddy A.K.,Indus Instruments | Lindsey M.L.,University of Mississippi Medical Center | Buffenstein R.,University of Texas Health Science Center at San Antonio
American Journal of Physiology - Heart and Circulatory Physiology | Year: 2014

The naked mole-rat (NMR) is the longest-lived rodent known, with a maximum lifespan potential (MLSP) of >31 years. Despite such extreme longevity, these animals display attenuation of many age-associated diseases and functional changes until the last quartile of their MLSP. We questioned if such abilities would extend to cardiovascular function and structure in this species. To test this, we assessed cardiac functional reserve, ventricular morphology, and arterial stiffening in NMRs ranging from 2 to 24 years of age. Dobutamine echocardiography (3 μg/g ip) revealed no age-associated changes in left ventricular (LV) function either at baseline or with exercise-like stress. Baseline and dobutamine-induced LV pressure parameters also did not change. Thus the NMR, unlike other mammals, maintains cardiac reserve with age. NMRs showed no cardiac hypertrophy, evidenced by no increase in cardiomyocyte cross-sectional area or LV dimensions with age. Age-associated arterial stiffening does not occur since there are no changes in aortic blood pressures or pulse-wave velocity. Only LV interstitial collagen deposition increased 2.5-fold from young to old NMRs (P < 0.01). However, its effect on LV diastolic function is likely minor since NMRs experience attenuated age-related increases in diastolic dysfunction in comparison with other species. Overall, these findings conform to the negligible senescence phenotype, as NMRs largely stave off cardiovascular changes for at least 75% of their MLSP. This suggests that using a comparative strategy to find factors that change with age in other mammals but not NMRs could provide novel targets to slow or prevent cardiovascular aging in humans. © 2014 the American Physiological Society.


Pollonini L.,University of Houston | Pollonini L.,Future Health | Rajan N.O.,Future Health | Rajan N.O.,Methodist Research Institute | And 6 more authors.
Journal of Medical Systems | Year: 2012

Remote patient monitoring (RPM) holds great promise for reducing the burden of congestive heart failure (CHF). Improved sensor technology and effective predictive algorithms can anticipate sudden decompensation events. Enhanced telemonitoring systems would promote patient independence and facilitate communication between patients and their physicians. We report the development of a novel hand-held device, called Blue Box, capable of collecting and wirelessly transmitting key cardiac parameters derived from three integrated biosensors: 2 lead electrocardiogram (ECG), photoplethysmography and bioelectrical impedance (bioimpedance). Blue Box measurements include time intervals between consecutive ECG R-waves (RR interval), time duration of the ECG complex formed by the Q, R and S waves (QRS duration), bioimpedance, heart rate and systolic time intervals. In this study, we recruited 24 healthy subjects to collect several parameters measured by Blue Box and assess their value in correlating with cardiac output measured with Echo-Doppler. Linear correlation between the heart rate measured with Blue Box and cardiac output from Echo- Doppler had a group average correlation coefficient of 0.80. We found that systolic time intervals did not improve the model significantly. However, STIs did inversely correlate with increasing workloads. © Springer Science+Business Media, LLC 2010.


Salazar B.H.,University of Houston | Reddy A.K.,Baylor College of Medicine | Reddy A.K.,Indus Instruments | Tao Z.,University of Houston | And 2 more authors.
IEEE Transactions on Biomedical Engineering | Year: 2015

The purpose of this study was to develop, assess, and validate a custom 32-channel system to analyze the electrical properties of 3-D artificial heart muscle (3D-AHM). In this study, neonatal rat cardiac cells were cultured in a fibrin gel to drive the formation of 3D-AHM. Once the tissues were fully formed, the customized electrocardiogram (EKG) sensing system was used to obtain the different electrophysiological characteristics of the muscle constructs. Additionally, this system was used to evaluate the electrical properties of native rat hearts, for comparison to the fabricated tissues and native values found in the literature. Histological evaluation showed extensive cellularization and cardiac tissue formation. EKG data analysis yielded time delays between the signals ranging from 0 to 7 ms. Optical maps exhibited slight trends in impulse propagation throughout the fabricated tissue. Conduction velocities were calculated longitudinally at 277.81 cm/s, transversely at 300.79 cm/s, and diagonally at 285.68 cm/s for 3D-AHM. The QRS complex exhibited an R-wave amplitude of 438.42 ± 36.96 μV and an average duration of 317.5 ± 16.5 ms for the tissue constructs. The data collected in this study provide a clearer picture about the intrinsic properties of the 3D-AHM while proving our system's efficacy for EKG data procurement. To achieve a viable and permanent solution, the bioengineered heart muscle must physiologically resemble native heart tissue as well as mimic its electrical properties for proper contractile function. This study allows us to monitor such properties and assess the necessary changes that will improve construct development and function. © 1964-2012 IEEE.


Hartley C.J.,Baylor College of Medicine | Reddy A.K.,Baylor College of Medicine | Madala S.,Indus Instruments | Entman M.L.,Baylor College of Medicine | Taffet G.E.,Baylor College of Medicine
Ultrasound in Medicine and Biology | Year: 2010

If volume flow was measured at each end of an arterial segment with no branches, any instantaneous differences would indicate that volume was increasing or decreasing transiently within the segment. This concept could provide an alternative method to assess the mechanical properties or distensibility of an artery noninvasively using ultrasound. The goal of this study was to determine the feasibility of using Doppler measurements of pulsatile velocity (opposed to flow) at two sites to estimate the volume pulsations of the intervening arterial segment. To test the concept over a wide range of dimensions, we made simultaneous measurements of velocity in a short 5 mm segment of a mouse common carotid artery and in a longer 20 cm segment of a human brachial-radial artery using a two-channel 20 MHz pulsed Doppler and calculated the waveforms and magnitudes of the volume pulsations during the cardiac cycle. We also estimated pulse wave velocity from the velocity upstroke arrival times and measured artery wall motion using tissue Doppler methods for comparison of magnitudes and waveforms. Volume pulsations estimated from Doppler velocity measurements were 16% for the mouse carotid artery and 4% for the human brachial artery. These values are consistent with the measured pulse wave velocities of 4.2 m/s and 10 m/s, respectively, and with the mouse carotid diameter pulsation. In addition, the segmental volume waveforms resemble diameter and pressure waveforms as expected. We conclude that with proper application and further validation, dual Doppler velocity measurements can be used to estimate the magnitude and waveform of volume pulsations of an arterial segment and to provide an alternative noninvasive index of arterial mechanical properties. (E-mail: cjhartley@ieee.org). © 2010 World Federation for Ultrasound in Medicine & Biology.


Hartley C.J.,Baylor College of Medicine | Reddy A.K.,Baylor College of Medicine | Madala S.,Indus Instruments | Entman M.L.,Baylor College of Medicine | And 2 more authors.
American Journal of Physiology - Heart and Circulatory Physiology | Year: 2011

With the growth of genetic engineering, mice have become increasingly common as models of human diseases, and this has stimulated the development of techniques to assess the murine cardiovascular system. Our group has developed nonimaging and dedicated Doppler techniques for measuring blood velocity in the large and small peripheral arteries of anesthetized mice. We translated technology originally designed for human vessels for use in smaller mouse vessels at higher heart rates by using higher ultrasonic frequencies, smaller transducers, and higher-speed signal processing. With these methods one can measure cardiac filling and ejection velocities, velocity pulse arrival times for determining pulse wave velocity, peripheral blood velocity and vessel wall motion waveforms, jet velocities for the calculation of the pressure drop across stenoses, and left main coronary velocity for the estimation of coronary flow reserve. These noninvasive methods are convenient and easy to apply, but care must be taken in interpreting measurements due to Doppler sample volume size and angle of incidence. Doppler methods have been used to characterize and evaluate numerous cardiovascular phenotypes in mice and have been particularly useful in evaluating the cardiac and vascular remodeling that occur following transverse aortic constriction. Although duplex ultrasonic echo-Doppler instruments are being applied to mice, dedicated Doppler systems are more suitable for some applications. The magnitudes and waveforms of blood velocities from both cardiac and peripheral sites are similar in mice and humans, such that much of what is learned using Doppler technology in mice may be translated back to humans. © 2011 by the American Physiological Society.


Grant
Agency: Department of Health and Human Services | Branch: | Program: SBIR | Phase: Phase II | Award Amount: 1.33M | Year: 2012

Cardiac arrhythmias are a major public health burden. There are 250,000 - 400,000 sudden cardiac deaths (SCD) in the US every year, accounting for up to 20% of all deaths in adults; the majority of these are due to ventricular fibrillation. In addition, approximately 2.5 million Americans now suffer atrial fibrillation (AF), a number that is expected to surpass 5 million by 2050. Strong evidence indicates that risk for both SCD and AF include a prominent genetic component. Genetically-modified mice are a powerful model to study mechanisms underlying cardiac arrhythmias and heart failure. In larger animals, clinical pacemakers can be used to develop models of chronic AF or pacing-induced heart failure, among others. However, it has not been possible to develop similar models in transgenic or knockout mice due to the lack of availability of miniature, implantable pacemakers. Existing implantable telemetry devices for cardiac monitoring in small animals are either too large, too heavy, or have inadequate batterylife. Moreover, these devices are not able to pace the hearts, which is essential for the development of the above models. The goal of this contract is to develop a small (lt 1cc), light-weight (lt 1gram), batteryless, wireless programmable implantable device for in vivo stimulation and monitoring of cardiac electrical activity in mice and other small animals. With batteryless operation by resonant inductive power transfer and wireless operation with a standard mouse cage, such a device will be suitable for long-term, ambulatory pacing and ECG monitoring in mice.


Grant
Agency: Department of Health and Human Services | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2010

Not Available


Grant
Agency: Department of Health and Human Services | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 98.50K | Year: 2010

DESCRIPTION (provided by applicant): Wearable Sensor for Continuous Noninvasive Monitoring of Pulse Pressure Blood pressure and pulse pressure are among the most commonly measured parameters to assess cardiovascular function. However, existing solutions for continuous noninvasive monitoring require cumbersome cuffs and are unsuitable for true ambulatory use. We propose to develop a compact, cuff-less, wearable patch sensor for continuous noninvasive monitoring of pulse pressure for human use. The sensor will be adhered like a band-aid to the skin over the carotid or brachial artery and will use pulsed Doppler ultrasound to continuously measure blood flow velocity, arterial diameter with a 1 micron resolution and local pulse transit times with 0.1 millisecond resolution. These measurements are input to an algorithm to estimate pulse pressure for each heartbeat without the need for calibration. The sensor can also estimate systolic, diastolic, and mean pressure with intermittent calibration against an independent measurement. An added benefit of the sensor is the simultaneous measurement of other useful hemodynamic parameters: heart rate, local pulse wave velocity, and arterial diameter. The sensor will consist of a multi-element high frequency ultrasound transducer, pulsed Doppler electronics for measurement of blood flow velocity and arterial wall displacement, an embedded microcontroller with software for calculation of hemodynamic parameters, and a bi-directional wireless link for telemetry. During phase I we will 1) build a multi-element Doppler transducer and bench top wired Pulsed Doppler electronics, 2) validate the technique and algorithms with in-vivo animal studies, and 3) demonstrate pulse pressure measurement in humans by comparison with snapshot measurements by expert operators using auscultation, and by comparison with continuous measurements from commercially available cuff based devices. During phase II we will refine the transducer, electronics and algorithms, add wireless capability, perform validation with human studies, and miniaturize the transducer and electronics to fit into a compact wearable adhesive patch (40mm x 20mm x 10mm). The final result will be a cost-effective commercial product that addresses an unmet need in the market for a compact cuff-less wearable noninvasive pulse pressure monitor and will have wide applicability in home care (white coat hypertension, chronic cardiac disease monitoring), in hospital care (ICU, ER), in portable use (ambulances, disaster medicine, battle field triage), and for remote health monitoring of personnel (battle field, hazardous industrial locations, and space). PUBLIC HEALTH RELEVANCE: Blood pressure and pulse pressure are among the most commonly measured parameters to assess cardiovascular function. However, existing solutions for continuous noninvasive monitoring require cumbersome cuffs and are unsuitable for true ambulatory use. The proposed work will result in a compact, cuff-less, wearable patch sensor for continuous non-invasive monitoring of pulse pressure in humans. This device will have wide applicability in home care (white coat hypertension, chronic cardiac disease monitoring), in hospital care (ICU, ER), in portable use (ambulances, disaster medicine, battle field triage), and for remote health monitoring of personnel (battle field, hazardous industrial locations, and space).

Loading Indus Instruments collaborators
Loading Indus Instruments collaborators