Evaluation of vascular aging on measures of cardiac function and mechanical efficiency: insights from in-silico modeling.

Introduction: This study evaluated the hypothesis that vascular aging (VA) reduces ventricular contractile function and mechanical efficiency (ME) using the left ventricular pressure-volume (PV) construct. Methods: A previously published in-silico computational model (CM) was modified to evaluate the hypothesis in two phases. In phase I, the CM included five settings of aortic compliance (CA) from normal to stiff, studied at a heart rate of 80 bpm, and phase II included the normal to stiff CA settings evaluated at 60, 100, and 140 bpm. The PV construct provided steady-state and transient data through a simulated vena caval occlusion (VCO). The steady-state data included left ventricular volumes (EDV and ESV), stroke work (SW), and VCO provided the PV area (PVA) data in addition to the three measures of contractile state (CS): end-systolic pressure-volume relationship (ESPVR), dP/dtmax-EDV and preload recruitable stroke work (PRSW). Finally, ME was calculated with the SW/PVA parameter. Results: In phase I, EDV and ESV increased, as did SW and PVA. The impact on the CS parameters demonstrated a small decrease in ESPVR, no change in dP/dtmax-EDV, and a large increase in PRSW. ME decreased from 71.5 to 60.8%, respectively. In phase II, at the normal and stiff CA settings, across the heart rates studied, EDV and ESV decreased, ESPVR and dP/dtmax-EDV increased and PRSW decreased. ME decreased from 76.4 to 62.6% at the normal CA and 65.8 to 53.2% at the stiff CA. Discussion: The CM generated new insights regarding how the VA process impacts the contractile state of the myocardium and ME.

Evaluation of ventricular-vascular coupling with critical care metrics: An in silico approach.

Mean arterial pressure and cardiac output provide insufficient guidance for the management of intraoperative hypotension (IOH). In silico models offer additional insights into acute changes in hemodynamic parameters that may be encountered during IOH. A computational model (CM) generated parameters quantifying ventricular-vascular coupling, and pressure-volume construct across levels of aortic compliance (CA ). We studied how a loss from normal-to-stiff CA impacts critical care metrics of hemodynamics during vascular occlusion. Pulse pressure (PP), end-systolic pressure (Pes ), arterial compliance (Art-ca), arterial elastance (Art-ea), and dynamic arterial elastance (Eadyn), along mechanical efficiency (ME) were measured at five levels of CA . A loss in CA impacted all variables. During steady-state conditions, PP, Pes , and stroke work increased significantly as CA decreased. Art-ca decreased and Art-ea increased similarly; Eadyn increased and ME decreased. During a decrease in preload across all CA levels, arterial dynamics measures remained linear. The CM demonstrated that a loss in CA impacts measures of arterial dynamics during steady-state and transient conditions and the model demonstrates that critical care metrics are sensitive to changes in CA . While Art-ca and Art-ea were sensitive to changes in preload, Eadyn did not change.

Tele-Operative Low-Cost Robotic Lung Ultrasound Scanning Platform for Triage of COVID-19 Patients.

Novel severe acute respiratory syndrome coronavirus 2 (COVID-19) has become a pandemic of epic proportions, and global response to prepare health systems worldwide is of utmost importance. 2-dimensional (2D) lung ultrasound (LUS) has emerged as a rapid, noninvasive imaging tool for diagnosing COVID-19 infected patients. Concerns surrounding LUS include the disparity of infected patients and healthcare providers, and importantly, the requirement for substantial physical contact between the patient and operator, increasing the risk of transmission. New variants of COVID-19 will continue to emerge; therefore, mitigation of the virus's spread is of paramount importance. A tele-operative robotic ultrasound platform capable of performing LUS in COVID-19 infected patients may be of significant benefit, especially in low- and middle-income countries. The authors address the issues mentioned above surrounding the use of LUS in COVID-19 infected patients and the potential for extension of this technology in a resource-limited environment. Additionally, first-time application, feasibility, and safety were validated in healthy subjects. Preliminary results demonstrate that our platform allows for the successful acquisition and application of robotic LUS in humans.

Speckle echocardiographic left atrial strain and stiffness index as predictors of maintenance of sinus rhythm after cardioversion for atrial fibrillation: a prospective study.

BACKGROUND: Echocardiographic left atrial (LA) strain parameters have been associated with atrial fibrillation (AF) in prior studies. Our goal was to determine if strain measures [peak systolic longitudinal strain (LAS) and stiffness index (LASt)] changed after cardioversion (CV); and their relation to AF recurrence. METHODS AND RESULTS: 46 participants with persistent AF and 41 age-matched participants with no AF were recruited. LAS and LASt were measured before and immediately after CV using 2D speckle tracking imaging (2DSI). Maintenance of sinus rhythm was assessed over a 6-month follow up. Mean LAS was lower, and mean LASt higher, in participants with AF before CV as compared to control group (11.9±1.0 vs 35.7±1.7, p<0.01 and 1.31±0.17 vs 0.23±0.01, p<0.01, respectively). There was an increase in the mean LAS immediately after CV (11.9±1.0 vs 15.9±1.3, p<0.01), whereas mean LASt did not change significantly after CV (p=0.62). Although neither LAS nor LASt were independently associated with AF recurrence during the follow-up period, change in LAS after cardioversion (post-CV LAS-pre-CV LAS) was significantly higher among individuals who remained in sinus rhythm when compared to individuals with recurrent AF (3.6±1.1 vs 0.4±0.8, p=0.02). CONCLUSIONS: LAS and LASt differed between participants with and without AF, irrespective of the rhythm at the time of echocardiographic assessment. Baseline LAS and LASt were not associated with AF recurrence. However, change in LAS after CV may be a useful predictor of recurrent arrhythmia.

Left atrial volume and geometry in healthy aging: the Cardiovascular Health Study.

BACKGROUND: The left atrium is a validated marker of clinical and subclinical cardiovascular disease. Left atrial enlargement is often seen among older individuals; however, there are few population-based data regarding normal left atrial size among older persons, especially from those who are healthy, and from women. Furthermore, because the left atrium is a 3D structure, the commonly used parasternal long-axis diastolic diameter often underdiagnoses left atrial enlargement. METHODS AND RESULTS: We evaluated left atrial size in 230 healthy participants (mean age, 76+/-5 years) free of prevalent cardiac disease, rhythm abnormality, hypertension, and diabetes selected from the Cardiovascular Health Study, a prospective community-based study of risk factors for cardiovascular disease in 5888 elderly participants. In addition to the standard long-axis measurement, we obtained left atrial superoinferior and lateral diameters and used these dimensions to estimate left atrial volume. These measurements were used to generate reference ranges for determining left atrial enlargement in older men and women, based on the 95% percentiles of the left atrial dimensions in healthy participants, both unadjusted, and after adjustment for age, height, and weight. In healthy elderly subjects, indices of left atrial size do not correlate with age or height but with weight and other measures of body build. CONCLUSIONS: These data provide normative reference values for left atrial size in healthy older women and men. The results should be useful for refining diagnostic criteria for left atrial dilation in the older population and may be relevant for cardiovascular risk stratification.

Cardiac mechanics in mild hypertensive heart disease: a speckle-strain imaging study.

BACKGROUND: We hypothesized that abnormalities in regional systolic strain (epsilon) might be present among hypertensive subjects with normal ejection fraction, and, if present, could be used to identify patients at high risk for heart failure. The aim of the current case-control study was to use speckle tracking imaging to identify subclinical global and regional systolic function abnormalities in hypertensive subjects with normal ejection fraction. METHODS AND RESULTS: Standard 2D Doppler echocardiography, tissue Doppler imaging, and 2D speckle strain imaging were performed in 52 hypertensive subjects with normal ejection fraction and 52 control subjects of similar age. Peak systolic (S'), and diastolic (E') annular velocities were obtained by tissue Doppler imaging, whereas longitudinal myocardial systolic velocity (V(l)) and circumferential, longitudinal, and radial strains (epsilon(c), epsilon(l), epsilon(r)) were obtained by speckle tracking. Midwall shortening and peak basal longitudinal strain (epsilon(l)) were used as indices of regional function. Hypertensive subjects had lower velocities--tissue Doppler imaging E' and S', and V(l)--and evidence of reduced regional function. Surprisingly, however, global epsilon values did not differentiate hypertensive subjects from control subjects. Among hypertensive patients, significant inverse associations were found between left ventricular mass and global longitudinal and circumferential epsilon (both P<0.05). CONCLUSIONS: Hypertensive heart disease with normal ejection fraction is associated with reduced myocardial velocities and reduced regional function but normal global epsilon. Our data suggest that velocity abnormalities occur early in hypertension and may be an appropriate target for preventive strategies because they occur before abnormalities in global epsilon.

Assessment of the right ventricle by echocardiography: a primer for cardiac sonographers.

The assessment of right ventricular (RV) structure and function by echocardiography has been improved by advancements that include Doppler tissue imaging, strain imaging, and three-dimensional imaging. Doppler tissue imaging and strain imaging can be useful for the assessment of regional RV systolic and diastolic function. Three-dimensional imaging has been reported to determine RV volumes and ejection fraction, which have previously been cumbersome to measure with conventional two-dimensional echocardiography. This article addresses the role of conventional and newer methods of echocardiography to assist sonographers in understanding the technical considerations, limitations, and pitfalls of image acquisition and analysis of RV structure and function.

Usefulness of the pulmonary arterial systolic pressure to predict pulmonary arterial wedge pressure in patients with normal left ventricular systolic function.

Tissue Doppler imaging combined with transmitral Doppler permits estimation of pulmonary artery wedge pressure (PAWP) in many, but not all, patients, whereas pulmonary artery systolic pressure (PASP) and cardiac output (time-velocity integral method) are routinely measured. It was hypothesized that simple Doppler echocardiographic measurements could be used to estimate PAWP in many patients by rearranging the equation for pulmonary vascular resistance ([mean pulmonary artery pressure - (left atrial pressure/cardiac output)] x 80). Data from 69 patients (mean age 59 +/- 15 years) were reviewed, including cardiac output, transmitral mitral E wave velocity, and lateral tissue Doppler imaging mitral annular early diastolic velocity. PAWP was determined in the 2 ways of (1) measured (PAWPm) using the regression equation PAWPm = 1.91 + (1.24 * transmitral mitral E wave velocity/mitral annular early diastolic velocity) developed and validated by Nagueh, and (2) using a nomogram that we developed to predict PAWP when cardiac output and PASP were known. Moderately strong correlation was found between PASP and PAWPm (r = 0.73), and this correlation improved when excluding patients with pulmonary or liver disease and restricting cardiac output to 3.5 to 6.0 L/min (physiologic range; r = 0.81). Furthermore, the relation between PAWPm and PASP allowed for discrimination of high versus low PAWP: 36 of 37 patients with PASP < or =30 mm Hg had PAWPm < or =15 mm Hg (sensitivity 97%, specificity 47%). Conversely, 9 of 9 patients with PASP > or =40 mm Hg had PAWPm > or =12 mm Hg (sensitivity 100%, specificity 70%). Predicted PAWP correlated well with PAWPm (r = 0.63) and improved when patients with liver or pulmonary disease were excluded (r = 0.83). In conclusion, PASP strongly correlated with PAWP, and this principle can be exploited to rapidly detect patients with low or high PAWP.

Direct ultrasound measurement of longitudinal, circumferential, and radial strain using 2-dimensional strain imaging in normal adults.

Current noninvasive techniques used to evaluate left ventricular systolic function are limited by dependence on the angle of insonation (tissue Doppler imaging/TDI) or limited by availability (MRI tagging). We utilized 2-dimensional speckle strain (epsilon) imaging (1) to establish normal values for all three epsilon vectors; (2) to compare circumferential epsilon values with circumferential shortening (midwall fractional shortening (FS(mw)); (3) to examine the relationship between left ventricular epsilon and wall stress; and (4) to compare 2D echocardiographic characteristics by gender. Echocardiography was performed in 60 normal subjects (mean 39 +/- 15 years). Small, but significant regional heterogeneity was seen in circumferential epsilon, but not in radial or longitudinal epsilon. We found an inverse correlation between circumferential epsilon and stress (r =-0.29, p<0.05) as well as longitudinal epsilon and stress (r =-0.11, P < 0.05), though the relationships were not close. We also observed a linear relationship between mean circumferential epsilon and FS(mw) (r = 0.29, P < 0.05). In conclusion, (1) 2-dimensional epsilon imaging permits measurement of regional systolic epsilon values in the majority of normal individuals; (2) epsilon values furnished by this method obey expected stress-shortening relationships; (3) systolic epsilon displays minor regional heterogeneity in the circumferential direction; (4) for the first time, a close relationship between FS(mw) and mean circumferential epsilon was demonstrated; and (5) there are minor gender-related differences in LV geometry and function.

Heart failure in the "oldest old": clinical and echocardiographic insights.

While the incidence and prevalence of heart failure (HF) increase markedly with age, few studies have included data on a large series of patients aged 85 years and older. Clinical and echocardiographic data from 533 patients admitted to a tertiary care hospital for acute HF were obtained. Data from the oldest old (>or=85 years; n=252; mean age, 91.9+/-3.6 years) were compared with data from those aged 65 to 74 years (n=123; mean age, 70.1+/-2.8 years) and 75 to 84 years (n=158; mean age, 79.4+/-2.9 years). Echocardiographic data were consistent with hypertensive remodeling. The proportion of patients with HF and a preserved left ventricular ejection fraction was greatest in the oldest patients (61%) in comparison to patients aged 65 to 74 years (48%) and 75 to 84 years (48%). Approximately three-fourths of the oldest patients were women, and two-thirds of women had a left ventricular ejection fraction >or=50%.

Analysis of left ventricular systolic function using midwall mechanics in patients >60 years of age with hypertensive heart disease and heart failure.

Normal ejection fraction (EFs) is often equated with normal systolic function. However, midwall mechanics reveal systolic dysfunction in hypertensive heart disease accompanied by hypertrophic remodeling. Midwall mechanics are unstudied in patients with acute diastolic heart failure (HF). This study analyzed left ventricular (LV) midwall stress-shortening relations in 61 patients aged >60 years with hypertensive heart disease, HF, and normal EF. Sixty-one hypertensive patients (mean age 78 +/- 10 years) who presented with HF, each with an EF >50%, underwent echocardiography. Midwall mechanics were compared with those of 79 controls (mean age 75 +/- 8 years) without structural heart disease. Relative wall thickness (0.63 +/- 0.11 vs 0.46 +/- 0.10 mm) and LV mass (237 +/- 67 vs 177 +/- 57 g) were significantly greater in patients with HF compared with controls. Mean EFs were similar in patients with HF and controls (64 +/- 9% vs 67 +/- 9%). Although mean endocardial fractional shortening (35 +/- 7% vs 37 +/- 7%) was not significantly different, midwall shortening in patients with HF was significantly less compared with controls (16 +/- 2% vs 19 +/- 3%, p <0.05). Eighteen of the 61 patients with HF (30%) had midwall shortening that was <95% confidence intervals of the normal midwall stress-shortening relations. By this criterion, these patients had systolic dysfunction despite normal EF; they had smaller LV chambers (in dimension and volume), greater relative wall thickness, and smaller stroke volumes. In conclusion, almost 1/3 of patients hospitalized with diastolic HF had systolic dysfunction, characterized by abnormal midwall stress-shortening relations.

Paradoxical changes in brain natriuretic peptide levels and loading conditions after intravenous conscious sedation.

BACKGROUND: Elevated filling pressure and wall stress have been proposed as stimuli for elevated brain natriuretic peptide (BNP) levels. Narcotic and benzodiazepine sedation, such as is used for transesophageal echocardiography (TEE), is known to decrease filling pressures. We hypothesized that lower filling pressure and wall stress associated with intravenous conscious sedation (IVCS) would lead to lower BNP levels. METHODS: We studied BNP levels, blood pressure, and echocardiographic indices of filling pressure and wall stress before and after IVCS and TEE. RESULTS: When data before and after IVCS and TEE were compared, mean blood pressure decreased (149 +/- 24/83 +/- 14 mm Hg vs 126 +/- 29/69 +/- 14; P < .01), as did mitral Doppler E wave velocity (82 +/- 23 cm/s vs 76 +/- 22; P < .05), right ventricular/atrial gradient (31 +/- 10 mm Hg vs 29 +/- 13; P < .05), and wall stress. However, BNP levels increased (195 +/- 407 pg/mL vs 238 +/- 458; P < .01). CONCLUSIONS: In a series of patients undergoing clinically indicated TEE, BNP levels increase above baseline after IVCS. The increase in BNP occurs despite lower blood pressure, lower mitral Doppler E velocity, lower right ventricular/atrial gradient, and lower wall stress compared with baseline. The mechanism of the paradoxical increase in BNP is not entirely clear, but it may conceivably be a result of counterregulatory hormone release caused by acute decrease in blood pressure.

Brain natriuretic peptide levels fall rapidly after cardioversion of atrial fibrillation to sinus rhythm.

BACKGROUND: Brain natriuretic peptide (BNP) levels have been reported to fall following cardioversion of atrial fibrillation (AF). The mechanism for the fall in BNP has not been elucidated and the potential confounding effects of sedation have not been investigated. Sedation may alter BNP levels via its effects on loading conditions. Accordingly, we studied whether BNP levels change shortly after cardioversion and attempted to control for possible effects of sedation. METHODS: BNP levels were obtained before and after cardioversion in patients with AF and in a control group of patients undergoing intravenous conscious sedation for transesophageal echocardiography. RESULTS: BNP levels dropped (260 +/- 255 vs. 190 +/- 212 pg/ml, p < 0.05) 40 min after cardioversion, decreasing in 33 of 41 subjects who achieved sinus rhythm. By contrast, mean BNP did not fall in subjects in whom cardioversion was not successful. The change in BNP level was not related to the degree of change in heart rate. No control subject experienced a change in cardiac rhythm; BNP levels increased (195 +/- 407 vs. 238 +/- 458 pg/ml, p < 0.05) in 18/22 subjects after sedation. Baseline BNP levels were elevated in subjects with AF, and BNP levels were elevated in parallel with heart failure symptoms. CONCLUSIONS: The rapid fall in BNP after cardioversion (1) may reflect prompt hemodynamic improvement associated with rhythm change and (2) does not appear to be due to the effects of sedation.

The utility of newly derived Doppler echocardiographic variables in the diagnosis and management of patients with heart failure.

Doppler echocardiography, because of its noninvasive nature, is an ideal tool to evaluate patients with heart failure (HF), offering the potential to improve early identification and management of these patients. Although traditional Doppler indices have allowed characterization of diastolic filling abnormalities associated with various HF states, important limitations are recognized. More refined Doppler techniques such as analysis of color M-mode flow propagation velocity, tissue Doppler imaging, and strain parameters can add to the ability of the noninvasive laboratory to improve the identification and management of this group of patients. These newer techniques as well as the traditional Doppler assessment of transmitral left ventricular inflow and pulmonary venous inflow velocities are reviewed as methods to improve the diagnosis and management of patients with HF.