Accuracy of Echocardiographic Cardiac Index Assessment in Subjects with Preserved Left Ventricular Ejection Fraction

Pulmonary and Systemic Hemodynamics in Patients with Hyperthyroidism

BACKGROUND

There is an association between hyperthyroidism and pulmonary hypertension. However, the prevalence of pulmonary hypertension in hyperthyroidism and the underlying mechanisms are incompletely defined.

METHODS

Consecutive patients with severe hyperthyroidism, mostly due to Graves disease, were included in this single-center study. Echocardiographic assessment of pulmonary hemodynamics was performed at the time of hyperthyroidism diagnosis (baseline) and after normalization of thyroid hormones (follow-up; median 11 months). In a subset of patients, right heart catheterization and noninvasive assessment of central hemodynamics was performed.

RESULTS

Among all 99 patients, 31% had pulmonary hypertension at baseline. The estimated systolic pulmonary artery pressure correlated significantly with the estimated left ventricular filling pressure (E/e'). The invasively measured systolic pulmonary artery pressure correlated well with the estimated systolic pulmonary artery pressure. Cardiac output, E/e', left and right ventricular dimensions were significantly reduced from baseline to follow-up, whereas the estimated pulmonary vascular resistance did not differ. Diastolic blood pressure was significantly higher at follow-up, with no change in systolic blood pressure. The central systolic blood pressure, however, exhibited a trend for a reduction at follow-up, while the pulse wave velocity was significantly lower at follow-up.

CONCLUSIONS

Approximately one-third of patients with hyperthyroidism have evidence of pulmonary hypertension. Our data suggest that an increased cardiac output and left ventricular filling pressure are the main mechanisms underlying the elevated systolic pulmonary artery pressure in hyperthyroidism, whereas there is no evidence of significant pulmonary vascular disease.

CARDIAC OUTPUT IN CRITICALLY ILL PATIENTS CAN BE ESTIMATED EASILY AND ACCURATELY USING THE MINUTE DISTANCE OBTAINED BY PULSED-WAVE DOPPLER

ABSTRACT

Background: Cardiac output (CO) assessment is essential for management of patients with circulatory failure. Among the different techniques used for their assessment, pulsed-wave Doppler cardiac output (PWD-CO) has proven to be an accurate and useful tool. Despite this, assessment of PWD-CO could have some technical difficulties, especially in the measurement of left ventricular outflow tract diameter (LVOTd). The use of a parameter such as minute distance (MD) which avoids LVOTd in the PWD-CO formula could be a simple and useful way to assess the CO in critically ill patients. Therefore, the aim of this study was to evaluate the correlation and agreement between PWD-CO and MD. Methods: A prospective and observational study was conducted over 2 years in a 30-bed intensive care unit (ICU). Adult patients who required CO monitoring were included. Clinical echocardiographic data were collected within the first 24 h and at least once more during the first week of ICU stay. PWD-CO was calculated using the average value of three LVOTd and left ventricular outflow tract velocity-time integral (LVOT-VTI) measurements, and heart rate. Minute distance was obtained from the product of LVOT-VTI × heart rate. Pulsed-wave Doppler cardiac output was correlated with MD using linear regression. Cardiac output was quantified from the MD using the equation defined by linear regression. Bland-Altman analysis was also used to evaluate the level of agreement between CO calculated from MD (MD-CO) and PWD-CO. The percentage error was calculated. Results: A total of 98 patients and 167 CO measurements were analyzed. Sixty-seven (68%) were male, the median age was 66 years (interquartile range [IQR], 53-75 years), and the median Acute Physiology and Chronic Health Evaluation II score was 22 (IQR, 16-26). The most common cause of admission was shock in 81 patients (82.7%). Sixty-nine patients (70.4%) were mechanically ventilated, and 68 (70%) required vasoactive drugs. The median CO was 5.5 L/min (IQR, 4.8-6.6 L/min), and the median MD was 1,850 cm/min (IQR, 1,520-2,160 cm/min). There was a significant correlation between PWD-CO and MD-CO in the general population ( R2 = 0.7; P < 0.05). This correlation improved when left ventricular ejection fraction (LVEF) was less than 60% ( R2 = 0.85, P < 0.05). Bland-Altman analysis showed good agreement between PWD-CO and MD-CO in the general population, the median bias was 0.02 L/min, the limits of agreement were -1.92 to +1.92 L/min. The agreement was better in patients with LVEF less than 60% with a median bias of 0.005 L/min and limits of agreement of -1.56 to 1.55 L/min. The percentage error was 17% in both cases. Conclusion: Measurement of MD in critically ill patients provides a simple and accurate estimate of CO, especially in patients with reduced or preserved LVEF. This would allow earlier cardiovascular assessment in patients with circulatory failure, which is of particular interest in difficult clinical or technical conditions.

Comparison of cardiac index measurements in intensive care patients using continuous wave vs. pulsed wave echo-Doppler compared to pulse contour cardiac output

PURPOSE

Cardiac index (CI) assessments are commonly used in critical care to define shock aetiology and guide resuscitation. Echocardiographic assessment is non-invasive and has high levels of agreement with thermodilution assessment of CI. CI assessment is derived from the velocity time integral (VTI) assessed using pulsed wave (PW) doppler at the level of the left ventricular outflow tract divided by body mass index. Continuous wave (CW) doppler through the aortic valve offers an alternative means to assess VTI and may offer better assessment at high velocities.

METHODS

We performed a single centre, prospective, observational study in a 15-bed intensive care unit in a busy district general hospital. Patients had simultaneous measurements of cardiac index by Pulse Contour Cardiac Output (PiCCO) (thermodilution), transthoracic echocardiographic PW-VTI and CW-VTI. Mean differences were measured with Bland-Altman limits of agreement and percentage error (PE) calculations.

RESULTS

Data were collected on 52 patients. 71% were supported with noradrenaline with or without additional inotropic or vasopressor agents. Mean CIs were: CW-VTI 2.7 L/min/m² (range 0.78-5.11, SD 0.92). PW-VTI 2.33 L/min/m² (range 0.77-5.40, SD 0.90) and PiCCO 2.86 L/min/m² (range 1.50-5.56, SD 0.93). CW-VTI and PiCCO mean difference was - 0.16 L/min/m² PE 43.5%. PW-VTI and PiCCO had a mean difference of - 0.54 L/min/m² PE 38.6%. CW-VTI and PW-VTI had a mean difference of 0.38 L/min/m² PE 46.0%.

CONCLUSIONS

CI derived from both CW-VTI and PW-VTI methods underestimate CI compared to PiCCO, with the CW-VTI method having closer values overall to PiCCO. CW-VTI may offer a more accurate assessment of CI. If using Critchley's PE cutoff of 30%, none of the doppler methods may accurately reflect the actual cardiac index.

Valid and Reproducible Quantitative Assessment of Cardiac Volumes by Echocardiography in Patients with Valvular Heart Diseases-Possible or Wishful Thinking?

The analysis of left ventricular function is predominantly based on left ventricular volume assessment. Especially in valvular heart diseases, the quantitative assessment of total and effective stroke volumes as well as regurgitant volumes is necessary for a quantitative approach to determine regurgitant volumes and regurgitant fraction. In the literature, there is an ongoing discussion about differences between cardiac volumes estimated by echocardiography and cardiac magnetic resonance tomography. This viewpoint focuses on the feasibility to assess comparable cardiac volumes with both modalities. The former underestimation of cardiac volumes determined by 2D and 3D echocardiography is presumably explained by methodological and technical limitations. Thus, this viewpoint aims to stimulate an urgent and critical rethinking of the echocardiographic assessment of patients with valvular heart diseases, especially valvular regurgitations, because the actual integrative approach might be too error prone to be continued in this form. It should be replaced or supplemented by a definitive quantitative approach. Valid quantitative assessment by echocardiography is feasible once echocardiography and data analysis are performed with methodological and technical considerations in mind. Unfortunately, implementation of this approach cannot generally be considered for real-world conditions.

Measuring the accuracy of cardiac output using POCUS: the introduction of artificial intelligence into routine care

Background

Shock management requires quick and reliable means to monitor the hemodynamic effects of fluid resuscitation. Point-of-care ultrasound (POCUS) is a relatively quick and non-invasive imaging technique capable of capturing cardiac output (CO) variations in acute settings. However, POCUS is plagued by variable operator skill and interpretation. Artificial intelligence may assist healthcare professionals obtain more objective and precise measurements during ultrasound imaging, thus increasing usability among users with varying experience. In this feasibility study, we compared the performance of novice POCUS users in measuring CO with manual techniques to a novel automation-assisted technique that provides real-time feedback to correct image acquisition for optimal aortic outflow velocity measurement.

Methods

28 junior critical care trainees with limited experience in POCUS performed manual and automation-assisted CO measurements on a single healthy volunteer. CO measurements were obtained using left ventricular outflow tract (LVOT) velocity time integral (VTI) and LVOT diameter. Measurements obtained by study subjects were compared to those taken by board-certified echocardiographers. Comparative analyses were performed using Spearman’s rank correlation and Bland–Altman matched-pairs analysis.

Results

Adequate image acquisition was 100% feasible. The correlation between manual and automated VTI values was not significant (p = 0.11) and means from both groups underestimated the mean values obtained by board-certified echocardiographers. Automated measurements of VTI in the trainee cohort were found to have more reproducibility, narrower measurement range (6.2 vs. 10.3 cm), and reduced standard deviation (1.98 vs. 2.33 cm) compared to manual measurements. The coefficient of variation across raters was 11.5%, 13.6% and 15.4% for board-certified echocardiographers, automated, and manual VTI tracing, respectively.

Conclusions

Our study demonstrates that novel automation-assisted VTI is feasible and can decrease variability while increasing precision in CO measurement. These results support the use of artificial intelligence-augmented image acquisition in routine critical care ultrasound and may have a role for evaluating the response of CO to hemodynamic interventions. Further investigations into artificial intelligence-assisted ultrasound systems in clinical settings are warranted.

Evaluation of a New Echocardiographic Tool for Cardiac Output Monitoring: An Experimental Study on A Controlled Hemorrhagic Shock Model in Anesthetized Piglets

Background: Cardiac output (CO) monitoring is recommended in patients with shock. The search for a reliable, rapid, and noninvasive tool is necessary for clinical practice. A new echocardiographic CO flow index (COF) is the automatic calculation of the sub-aortic VTI multiplied by the automatic calculation of the heart rate (HR). The primary objective of this study was to show the correlation between COF and CO measured by thermodilution (COth) in a controlled hemorrhagic shock model in anesthetized piglets. Secondary objectives were to show the correlation between COth and CO calculated from left outflow tract (LVOT) measurement and manual VTI (COman), and CO measured by LVOT measurement and VTIauto (COauto). Methods: Prospective interventional experimental study. In seventeen ventilated and anesthetized piglets, a state of hemorrhagic shock was induced, maintained, then resuscitated and stabilized. The gold standard for CO and stroke volume measurement was thermodilution (COth). Results: 191 measurements were performed. The correlation coefficients (r) between COth and COF, COman, and COauto were 0.73 [0.62; 0.81], 0.66 [0.56; 0.74], and 0.73 [0.63; 0.81], respectively. Conclusions: In this study, the COF appears to have a strong correlation to the COth. This automatic index, which takes into account the HR and does not require the measurement of LVOT, could be a rapidly obtained index in clinical practice.

Can blood loss be assessed by echocardiography? An experimental study on a controlled hemorrhagic shock model in piglets

BACKGROUND

Assessment of the volemic loss is a major challenge during the management of hemorrhagic shock. Echocardiography is an increasingly used noninvasive tool for hemodynamic assessment. In mechanically ventilated patients, some studies suggest that respiratory variations of mean subaortic time-velocity integral (∆VTI) would be predictive of fluid filling response. An experimental model of controlled hemorrhagic shock provides a precise approach to study correlation between blood volume and cardiac ultrasonographic parameters.

OBJECTIVES

The main objective was to analyze the ∆VTI changes during hemorrhage in an anesthetized-piglet model of controlled hemorrhagic shock. The secondary objective was to evaluate ∆VTI during the resuscitation process after hemorrhage and other echocardiographic parameters changes during the whole protocol.

METHODS

Twenty-four anesthetized and ventilated piglets were bled until mean arterial pressure reached 40 mm Hg. Controlled hemorrhage was maintained for 30 minutes before randomizing the piglets to two resuscitation groups: fluid filling group resuscitated with saline solution and noradrenaline group resuscitated with saline solution and noradrenaline. Echocardiography and hemodynamic measures, including pulsed pressure variations (PPV), were performed at different stages of the protocol.

RESULTS

The correlation coefficient between ΔVTI and PPV with the volume of bleeding during the hemorrhagic phase were respectively 0.24 (95% confidence interval, 0.08-0.39; p < 0.01) and 0.57 (95% CI, 0.44-0.67; p < 0.01). Two parameters had a moderate correlation coefficient with hemorrhage volume (over 0.5): mean subaortic time-velocity index (VTI) and mitral annulus diastolic tissular velocity (E').

CONCLUSION

In this hemorrhagic shock model, ΔVTI had a low correlation with the volume of bleeding, but VTI and E' had a correlation with blood volume comparable to that of PPV.

Reduced exercise capacity in patients with systemic sclerosis is associated with lower peak tissue oxygen extraction: a cardiovascular magnetic resonance-augmented cardiopulmonary exercise study

BACKGROUND

Exercise intolerance in systemic sclerosis (SSc) is typically attributed to cardiopulmonary limitations. However, problems with skeletal muscle oxygen extraction have not been fully investigated. This study used cardiovascular magnetic resonance (CMR)-augmented cardiopulmonary exercise testing (CMR-CPET) to simultaneously measure oxygen consumption and cardiac output. This allowed calculation of arteriovenous oxygen content gradient, a recognized marker of oxygen extraction. We performed CMR-CPET in 4 groups: systemic sclerosis (SSc); systemic sclerosis-associated pulmonary arterial hypertension (SSc-PAH); non-connective tissue disease pulmonary hypertension (NC-PAH); and healthy controls.

METHODS

We performed CMR-CPET in 60 subjects (15 in each group) using a supine ergometer following a ramped exercise protocol until exhaustion. Values for oxygen consumption, cardiac output and oxygen content gradient, as well as ventricular volumes, were obtained at rest and peak-exercise for all subjects. In addition, T1 and T2 maps were acquired at rest, and the most recent clinical measures (hemoglobin, lung function, 6-min walk, cardiac and catheterization) were collected.

RESULTS

All patient groups had reduced peak oxygen consumption compared to healthy controls (p < 0.022). The SSc and SSc-PAH groups had reduced peak oxygen content gradient compared to healthy controls (p < 0.03). Conversely, the SSc-PAH and NC-PH patients had reduced peak cardiac output compared to healthy controls and SSc patients (p < 0.006). Higher hemoglobin was associated with higher peak oxygen content gradient (p = 0.025) and higher myocardial T1 was associated with lower peak stroke volume (p = 0.011).

CONCLUSIONS

Reduced peak oxygen consumption in SSc patients is predominantly driven by reduced oxygen content gradient and in SSc-PAH patients this was amplified by reduced peak cardiac output. Trial registration The study is registered with ClinicalTrials.gov Protocol Registration and Results System (ClinicalTrials.gov ID: 100358).

Noninvasive Hemodynamic Monitoring of Cocaine-Induced Changes in Cardiac Output and Systemic Vascular Resistance in Subjects With Chronic Cocaine Use Disorder

BACKGROUND

Cocaine use disorder (CUD) is a common problem in the United States and worldwide. The mechanisms by which cocaine induces acute cardiovascular toxicity are various. When systemically absorbed through inhaled or intravenous routes, cocaine induces an acute rise in the heart rate (HR) and blood pressure (BP) leading to a significant increase in the cardiac output (CO) and myocardial oxygen demand. Subjects with chronic CUD represent a special population that has experienced long-term cocaine exposure, often without showing signs of cardiovascular disease. We herein present prospectively collected data on the acute hemodynamic effects of intravenous cocaine in a cohort of nontreatment-seeking individuals with CUD without cardiovascular disease.

METHODS AND RESULTS

Baseline physiologic data were collected while participants underwent infusion of escalating doses of cocaine (10, 20, and 40 mg administered over 2 minutes) at baseline and after receiving single-blind placebo treatment. Continuous noninvasive hemodynamic monitoring was performed throughout the infusion sessions using the ccNexfin finger cuffs (Edwards Lifesciences Corp, Irvine, CA). The recorded arterial BP tracings allowed for the measurement of beat-to-beat changes in HR, BP, stroke volume, CO, and systemic vascular resistance (SVR). None of the subjects experienced a treatment-related serious adverse event. Cocaine produced significant dose-dependent increases in median HR, BP, CO, and +dP/dt (a measure of cardiac contractility) and a significant dose-dependent reduction in median SVR.

CONCLUSIONS

Intravenous cocaine in a cohort of otherwise healthy subjects with CUD produced dose-dependent increases in CO, largely explained by an increase in HR, accompanied by a dose-dependent decrease in SVR.

Comparisons of Noninvasive Methods Used to Assess Exercise Stroke Volume in Heart Failure with Preserved Ejection Fraction

INTRODUCTION

Cardiopulmonary exercise testing (CPET) plays an important role in properly phenotyping signs and symptoms of heart failure with preserved ejection fraction (HFpEF). The prognostic value of CPET is strengthened when accompanied by cardiac hemodynamic measurements. Although recognized as the "gold" standard, cardiac catheterization is impractical for routine CPET. Thus, advancing the scientific/methodologic understanding of noninvasive techniques for exercise cardiac hemodynamic assessment is clinically impactful in HFpEF. This study tested the concurrent validity of noninvasive acetylene gas (C2H2) uptake, echocardiography (ECHO), and oxygen pulse (O2pulse) for measuring/predicting exercise stroke volume (SV) in HFpEF.

METHODS

Eighteen white HFpEF and 18 age-/sex-matched healthy controls participated in upright CPET (ages, 69 ± 9 yr vs 63 ± 9 yr). At rest, 20 W, and peak exercise, SV was measured at steady-state via C2H2 rebreathe (SVACET) and ECHO (SVECHO), whereas O2pulse was derived (=V˙O2/HR).

RESULTS

Resting relationships between SVACET and SVECHO, SVECHO and O2pulse, or SVACET and O2pulse were significant in HFpEF (R = 0.30, 0.36, 0.67), but not controls (R = 0.07, 0.01, 0.09), respectively. Resting relationships persisted to 20 W in HFpEF (R = 0.70, 0.53, 0.70) and controls (R = 0.05, 0.07, 0.21), respectively. Peak exercise relationships were significant in HFpEF (R = 0.62, 0.24, 0.64), but only for SVACET versus O2pulse in controls (R = 0.07, 0.04, 0.33), respectively. Standardized standard error of estimate between techniques was strongest in HFpEF at 20 W: SVACET versus SVECHO = 0.57 ± 0.22; SVECHO versus O2pulse = 0.71 ± 0.28; SVACET versus O2pulse = 0.56 ± 0.22.

CONCLUSIONS

Constituting a clinically impactful step towards construct validation testing, these data suggest SVACET, SVECHO, and O2pulse demonstrate moderate-to-strong concurrent validity for measuring/predicting exercise SV in HFpEF.

Impact of empagliflozin on subclinical left ventricular dysfunctions and on the mechanisms involved in myocardial disease progression in type 2 diabetes: rationale and design of the EMPA-HEART trial

Background

Asymptomatic left ventricular (LV) dysfunction is highly prevalent in type 2 diabetes patients. Unlike the other hypoglycemic drugs, SGLT2 inhibitors have shown potential benefits for reducing cardiovascular death and risk factors, aside from lowering plasma glucose levels. With this study we aim at determining whether the treatment with empagliflozin is associated with an improvement in LV functions in diabetic patients with asymptomatic LV dysfunction against Sitagliptin, which is presumably neutral on myocardial function. To determine changes in LV systolic and diastolic functions we will use speckle-tracking echocardiography, a novel sensitive, non-invasive, bedside method allowing the calculation of LV global longitudinal strain (GLS), an index of myocardial deformability, as well as 3D echocardiography, which allows a better evaluation of LV volumes and mass.

Methods

The EMPA-HEART trial will be a phase III, open label, active-controlled, parallel groups, single centre, exploratory study conducted in Pisa, Italy. A cohort of 75 diabetic patients with normal LV systolic (2D-Echo EF > 50%) and renal (eGFR sec MDRD > 60 ml/min/1.73 mq) functions and no evidence of valvular and/or ischemic heart disease will be randomized to either Empagliflozin 10 mg/die or Sitagliptin 100 mg/die. The primary outcome is to detect a change in GLS from baseline to 1 and 6 months after treatment initiation. The secondary outcomes include changes from baseline to 6 months in 3-D Echocardiography EF, left atrial volume and E/E′, VO₂max as measured at cardiopulmonary test, cardiac autonomic function tests (R–R interval during Valsalva manoeuvre, deep-breathing, lying-to-standing), and the determination of a set of plasma biomarkers aimed at studying volume, inflammation, oxidative stress, matrix remodelling, myocyte strain and injury.

Discussion

SGLT2 inhibitors might affect myocardial functions through mechanisms acting both directly and indirectly on the myocardium. The set of instrumental and biohumoral tests of our study might actually detect the presence and entity of empagliflozin beneficial effects on the myocardium and shed light on the mechanisms involved. Further, this study might eventually provide information to design a clinical strategy, based on echocardiography and/or biomarkers, to select the patients who might benefit more from this intervention.

Trial registration EUDRACT Code 2016-0022250-10

Integration of Flow-Gradient Patterns Into Clinical Decision Making for Patients With Suspected Severe Aortic Stenosis and Preserved LVEF: A Systematic Review of Evidence and Meta-Analysis

OBJECTIVES

This study was designed to evaluate the evidence base for the 2014 American Heart Association/American College of Cardiology (AHA/ACC) guidelines for severe aortic stenosis (SAS) and preserved left ventricular ejection fraction by comparing the natural history of the disease in subgroups of low-gradient (LG) aortic stenosis patients with high-gradient (HG) patients.

BACKGROUND

The 2014 AHA/ACC valvular disease guidelines recommend estimation of stroke volume index by echocardiography in patients with suspected LG SAS and preserved left ventricular ejection fraction.

METHODS

PubMed, Embase, and Scopus databases were searched for all studies that have compared the natural history of SAS with preserved ejection fraction in flow-gradient patterns. We studied the following 3 subgroups: HG, low-flow low-gradient (LFLG), and normal-flow low-gradient (NFLG). The random effects model was used to pool individual study results. The end-point was long-term all-cause mortality.

RESULTS

A total of 9 studies with 3,065 patients fulfilled the criteria. Compared to HG SAS, both LFLG and NFLG patients had a higher burden of comorbidities such as coronary artery disease and hypertension. Atrial fibrillation was more prevalent in LFLG patients. Moreover, end-diastolic volume index was smaller for LFLG patients and indexed aortic valve area was larger for NFLG patients. All-cause mortality was similar between HG and LFLG subgroups (relative risk: 1.07; 95% confidence interval: 0.83 to 1.38; p = 0.60), whereas patients with NFLG had a significantly lower all-cause mortality compared to the HG subgroup (relative risk: 0.64; 95% confidence interval: 0.47 to 0.86; p = 0.004).

CONCLUSIONS

Patients with LFLG SAS have similar outcomes compared to HG SAS but worse compared to NFLG SAS. These findings support estimating stroke volume index in patients with suspected LG SAS. All analyses revealed high heterogeneity and further high-quality studies are necessary.