Kathleen Garcia

Left Ventricular Hypertrophy in Hypertensive Adolescents Analysis of Risk by 2004 National High Blood Pressure Education Program Working Group Staging Criteria

The National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents recently recommended staging hypertension (HTN) in children and adolescents based on blood pressure severity. The use of blood pressure staging and its corresponding therapeutic approach was examined in this pooled analysis assessing the risk for end-organ damage, specifically left ventricular hypertrophy among hypertensive adolescents stratified by working group criteria. Newly diagnosed hypertensive adolescents and normotensive control subjects similar in age, race/ethnicity, gender, and body mass index completed casual and 24-hour ambulatory blood pressure measurements, M-mode echocardiography, and fasting serum laboratories. Hypertensive subjects had higher insulin and cholesterol but similar glucose levels as compared with control subjects. Among subjects with stage 1 HTN by casual blood pressure, 34% had white-coat HTN as opposed to 15% of stage 2 hypertensive subjects. Of the subjects with normal casual measurements, 20% had HTN by ambulatory monitoring. Subjects with stage 2 HTN by casual measurement alone (odds ratio: 4.13; 95% CI: 1.04 to 16.48) and after 24-hour ambulatory confirmation (odds ratio: 7.23; 95% CI: 1.28 to 40.68) had increased odds for left ventricular hypertrophy. In addition, the risk for left ventricular hypertrophy was similar for subjects with masked and confirmed stage 1 HTN, whereas subjects with white-coat HTN had a risk comparable to normotensive subjects. Thus, recommendations that adolescents with stage 2 HTN by casual measurements alone receive medication initially along with therapeutic lifestyle counseling are reasonable, though ambulatory blood pressure monitoring remains a valuable tool for evaluating children with stage 2 HTN, because >10% have white-coat HTN.

Cardiovascular Risk Factors and Sequelae in Hypertensive Children Identified by Referral Versus School-Based Screening

Abstract—To determine whether systematic differences exist between hypertensive children referred for evaluation by primary care providers and children identified through community-based screening, cardiovascular risk factors and surrogate markers of hypertensive injury were compared based on subject source (referral versus screening). Children referred to a hypertension clinic for persistently elevated blood pressure were compared with children identified as hypertensive during school screening of 5102 students in Houston public schools. M-mode echocardiography of the left ventricle was performed and subsequently reviewed by 2 independent sonographers blinded to identifying subject information. Subsets of subjects also underwent carotid artery ultrasound for measurement of intimal-medial thickness, overnight urine collections for microalbuminuria, and fasting serum cholesterol, triglycerides, and glucose. Ninety-seven total subjects (54 screening and 43 referral) met inclusion criteria and had technically adequate echocardiography performed. The prevalence of left ventricular hypertrophy (LVH) was 37%. Referral subjects demonstrated significantly greater left ventricular mass index (38.8 versus 34.2 g/m2.7; P <0.01) and a higher prevalence of LVH (49% versus 28%; P <0.05). Among subjects who underwent carotid ultrasound (n=75), carotid intimal-medial thickness was significantly higher in referral subjects (0.61 versus 0.57, P <0.05). When controlling for BMI z score, which was significantly higher in referral subjects, systematic differences by subject source did not persist. These findings suggest that hypertensive children who are predominantly overweight, independent of the manner in which patients come to medical attention, will manifest evidence of more severe cardiovascular disease assessed by surrogate markers such as left ventricular mass index or carotid artery intimal medial thickness.

Ultrasound in space.

Physiology of the human body in space has been a major concern for space-faring nations since the beginning of the space era. Ultrasound (US) is one of the most cost effective and versatile forms of medical imaging. As such, its use in characterizing microgravity-induced changes in physiology is being realized. In addition to the use of US in related ground-based studies, equipment has also been modified to fly in space. This involves alteration to handle the stresses of launch and different power and cooling requirements. Study protocols also have been altered to accommodate the microgravity environment. Ultrasound studies to date have shown a pattern of adaptation to microgravity that includes changes in cardiac chamber sizes and vertebral spacing. Ultrasound has been and will continue to be an important component in the investigation of physiological and, possibly, pathologic changes occurring in space or as a result of spaceflight.

On‐Orbit Prospective Echocardiography on International Space Station Crew

Objectives: A prospective trial of echocardiography was conducted on six crew members onboard the International Space Station. The main objective was to determine the efficacy of remotely guided tele‐echocardiography, including just‐in‐time e‐training methods and determine what is “space normal” echocardiographic data. Methods: Each crew member operator (n = 6) had 2‐hour preflight training. Baseline echocardiographic data were collected 55–167 days preflight. Similar equipment was used in each 60‐minute in‐flight session (mean microgravity exposure – 114 days [34 – 190]). On‐orbit ultrasound (US) operators used an e‐learning system within 24 hours of these sessions. Expert assistance was provided using US video downlink and two‐way voice. Testing was repeated 5–16 days after landing. Separate ANOVA was used on each echocardiographic variable (n = 33). Within each ANOVA, three tests were made: (a) effect of mission phase (preflight, in‐flight, postflight); (b) effect of echo technician (two technicians independently analyzed the data); (c) interaction between mission phase and technician. Results: Eleven rejections of the null hypothesis (mission phase or technician or both had no effect) were found that could be considered for possible follow up. Of these, eight rejections were for significant technician effects, not space flight. Three rejections of the null hypothesis (aortic valve time velocity integral, mitral E‐wave velocity, and heart rate) were attributable to space flight but determine to not be clinically significant. No rejections were due to the interaction between technician and space flight. Conclusion: Thus, we found no consistent clinically significant effects of long‐duration space flight on echocardiographic variables of the given group of subjects. (Echocardiography 2011;28:491‐501)

Sonography for determining the optic nerve sheath diameter with increasing intracranial pressure in a porcine model

This study investigated whether it is feasible to use sonography to monitor changes in the optic nerve sheath diameter in a porcine model.

New heights in ultrasound: first report of spinal ultrasound from the international space station.

BACKGROUND Changes in the lumbar and sacral spine occur with exposure to microgravity in astronauts; monitoring these alterations without radiographic capabilities on the International Space Station (ISS) requires novel diagnostic solutions to be developed. STUDY OBJECTIVES We evaluated the ability of point-of-care ultrasound, performed by nonexpert-operator astronauts, to provide accurate anatomic information about the spine in long-duration crewmembers in space. METHODS Astronauts received brief ultrasound instruction on the ground and performed in-flight cervical and lumbosacral ultrasound examinations using just-in-time training and remote expert tele-ultrasound guidance. Ultrasound examinations on the ISS used a portable ultrasound device with real-time communication/guidance with ground experts in Mission Control. RESULTS The crewmembers were able to obtain diagnostic-quality examinations of the cervical and lumbar spine that would provide essential information about acute or chronic changes to the spine. CONCLUSIONS Spinal ultrasound provides essential anatomic information in the cervical and lumbosacral spine; this technique may be extensible to point-of-care situations in emergency departments or resource-challenged areas without direct access to additional radiologic capabilities.

Point-of-care ultrasound in aerospace medicine: known and potential applications.

Since its initial introduction into the bedside assessment of the trauma patient via the Focused Assessment with Sonography for Trauma (FAST) exam, the use of point-of-care ultrasound has expanded rapidly. A growing body of literature demonstrates ultrasound can be used by nonradiologists as an extension of the physical exam to accurately diagnose or exclude a variety of conditions. These conditions include, but are not limited to, hemoperitoneum, pneumothorax, pulmonary edema, long-bone fracture, deep vein thrombosis, and elevated intracranial pressure. As ultrasound machines have become more compact and portable, their use has extended outside of hospitals to places where the physical exam and diagnostic capabilities may be limited, including the aviation environment. A number of studies using focused sonography have been performed to meet the diagnostic challenges of space medicine. The following article reviews the available literature on portable ultrasound use in aerospace medicine and highlights both known and potential applications of point-of-care ultrasound for the aeromedical clinician.

Doppler ultrasound of the central retinal artery in microgravity

BACKGROUND Ocular changes have been noted during long-duration spaceflight; we studied central retinal artery (CRA) blood flow using Doppler before, during, and after long-term microgravity exposure in astronauts compared with data from a control group of nonastronauts subjected to head-down tilt (HDT). METHODS Available Doppler spectra of International Space Station (ISS) crewmembers were obtained from the NASA Lifetime Surveillance of Astronaut Health database, along with 2D ultrasound-derived measurements of the optic nerve sheath diameter (ONSD). CRA Doppler spectra and optic nerve sheath images were also obtained from healthy test subjects in an acute HDT experiment at 20 min of exposure (the ground-based analogue). RESULTS HDT CRA peak systolic velocity in the ground-based analogue group increased by an average of 3 cm -s(-1) (33%) relative to seated values. ONSD at 300 of HDT increased by 0.5 mm relative to supine values. CRA Doppler spectra obtained on orbit were of excellent quality and demonstrated in-flight changes of +5 cm x s(-1) (50%) compared to preflight. ONSD increased in ISS crewmembers during flight relative to before flight, with some reversal postflight. DISCUSSION A significant ONSD response to acute postural change and to spaceflight was demonstrated in this preliminary study. Increases in Doppler peak flow velocities correlated with increases in ONSD. Further investigations are warranted to corroborate the relationship between ONSD, intracranial pressure, and central retinal blood flow for occupational surveillance and research purposes.

Concept of Operations Evaluation for Using Remote-Guidance Ultrasound for Exploration Spaceflight.

BACKGROUND Remote-guidance (RG) techniques aboard the International Space Station (ISS) have enabled astronauts to collect diagnostic-level ultrasound (US) images. Exploration-class missions will likely require nonformally trained sonographers to operate with greater autonomy given longer communication delays (> 6 s for missions beyond the Moon) and blackouts. Training requirements for autonomous collection of US images by non-US experts are being determined. METHODS Novice US operators were randomly assigned to one of three groups to collect standardized US images while drawing expertise from A) RG only, B) a computer training tool only, or C) both RG and a computer training tool. Images were assessed for quality and examination duration. All operators were given a 10-min standardized generic training session in US scanning. The imaging task included: 1) bone fracture assessment in a phantom and 2) Focused Assessment with Sonography in Trauma (FAST) examination in a healthy volunteer. A human factors questionnaire was also completed. RESULTS Mean time for group B during FAST was shorter (20.4 vs. 22.7 min) than time for the other groups. Image quality scoring was lower than in groups A or C, but all groups produced images of acceptable diagnostic quality. DISCUSSION RG produces US images of higher quality than those produced with only computer-based instruction. Extended communication delays in exploration missions will eliminate the option of real-time guidance, thus requiring autonomous operation. The computer program used appears effective and could be a model for future digital US expertise banks. Terrestrially, it also provides adequate self-training and mentoring mechanisms.

Preflight, In-Flight, and Postflight Imaging of the Cervical and Lumbar Spine in Astronauts

BACKGROUND Back pain is a common complaint during spaceflight that is commonly attributed to intervertebral disc swelling in microgravity. Ultrasound (US) represents the only imaging modality on the International Space Station (ISS) to assess its etiology. The present study investigated: 1) The agreement and correlation of spinal US assessments as compared to results of pre- and postflight MRI studies; and 2) the trend in intervertebral disc characteristics over the course of spaceflight to ISS. METHODS Seven ISS astronauts underwent pre- and postflight US examinations that included anterior disc height and anterior intervertebral angles with comparison to pre- and postflight MRI results. In-flight US images were analyzed for changes in disc height and angle. Statistical analysis included repeated measures ANOVA with Bonferroni post hoc analysis, Bland-Altman plots, and Pearson correlation. RESULTS Bland-Altman plots revealed significant disagreement between disc heights and angles for MRI and US measurements while significant Pearson correlations were found in MRI and US measurements for lumbar disc height (r2 = 0.83) and angle (r2 = 0.89), but not for cervical disc height (r2 = 0.26) or angle (r2 = 0.02). Changes in anterior intervertebral disc angle-initially increases followed by decreases-were observed in the lumbar and cervical spine over the course of the long-duration mission. The cervical spine demonstrated a loss of total disc height during in-flight assessments (∼0.5 cm). DISCUSSION Significant disagreement but significant correlation was noted between US and MRI measurements of disc height and angle. Consistency in imaging modality is important for trending measurements and more research related to US technique is required.Harrison MF, Garcia KM, Sargsyan AE, Ebert D, Riascos-Castaneda RF, Dulchavsky SA. Preflight, in-flight, and postflight imaging of the cervical and lumbar spine in astronauts. Aerosp Med Hum Perform. 2018; 89(1):32-40.