Non-invasive assessment of stroke volume and cardiovascular parameters based on peripheral pressure waveform.

Cardiovascular diseases are the leading cause of death globally, making the development of non-invasive and simple-to-use tools that bring insights into the state of the cardiovascular system of utmost importance. We investigated the possibility of using peripheral pulse wave recordings to estimate stroke volume (SV) and subject-specific parameters describing the selected properties of the cardiovascular system. Peripheral pressure waveforms were recorded in the radial artery using applanation tonometry (SphygmoCor) in 35 hemodialysis (HD) patients and 14 healthy subjects. The pressure waveforms were then used to estimate subject-specific parameters of a mathematical model of pulse wave propagation coupled with the elastance-based model of the left ventricle. Bioimpedance cardiography measurements (PhysioFlow) were performed to validate the model-estimated SV. Mean absolute percentage error between the simulated and measured pressure waveforms was 4.0% and 2.8% for the HD and control group, respectively. We obtained a moderate correlation between the model-estimated and bioimpedance-based SV (r = 0.57, p<0.05, and r = 0.58, p<0.001, for the control group and HD patients, respectively). We also observed a correlation between the estimated end-systolic elastance of the left ventricle and the peripheral systolic pressure in both HD patients (r = 0.84, p<0.001) and the control group (r = 0.70, p<0.01). These preliminary results suggest that, after additional validation and possibly further refinement to increase accuracy, the proposed methodology could support non-invasive assessment of stroke volume and selected heart function parameters and vascular properties. Importantly, the proposed method could be potentially implemented in the existing devices measuring peripheral pressure waveforms.

Thoracic fluid content (TFC) using electrical cardiometry versus lung ultrasound in the diagnosis of transient tachypnea of newborn.

This study aimed to evaluate TFC by EC versus lung ultrasound (LUS) findings for diagnosing and follow-up of TTN in late preterm and term neonates. This prospective observational study was conducted on 80 neonates with gestational age ≥ 34 weeks. TTN group included 40 neonates diagnosed with TTN, and no lung disease (NLD) group included 40 neonates without respiratory distress. LUS and EC were performed within the first 24 h of life and repeated after 72 h. There was a statistically significant increase in TFC in TTN group on D1 [48.48 ± 4.86 (1 KOhm-1)] compared to NLD group [32.95 ± 4.59 (1 KOhm-1)], and then significant decrease in TFC in D3 [34.90 ± 4.42 (1 KOhm-1)] compared to D1 in the TTN group. There was a significant positive correlation between both TFC and LUS with Downes' score, TTN score, and duration of oxygen therapy in the TTN group.   Conclusion: Both LUS and TFC by EC provide good bedside tools that could help to diagnose and monitor TTN. TFC showed a good correlation with LUS score and degree of respiratory distress. What is Known: • Transient tachypnea of the newborn (TTN) is the most common cause of respiratory distress in newborns. • TTN is a diagnosis of exclusion, there are no specific clinical parameters or biomarker has been identified for TTN. What is New: • Thoracic fluid content (TFC) by electrical cardiometry is a new parameter to evaluate lung fluid volume and could help to diagnose and monitor TTN and correlates with lung ultrasound score.

Transthoracic impedance variability to assess quality of chest compression in out-of-hospital cardiac arrest.

BACKGROUND: Chest compression is a lifesaving intervention in out-of-hospital cardiac arrest (OHCA), but the optimal metrics to assess its quality have yet to be identified. The objective of this study was to investigate whether a new parameter, that is, the variability of the chest compression-generated transthoracic impedance (TTI), namely ImpCC , which measures the consistency of the chest compression maneuver, relates to resuscitation outcome. METHODS: This multicenter observational, retrospective study included OHCAs with shockable rhythm. ImpCC variability was evaluated with the power spectral density analysis of the TTI. Multivariate regression model was used to examine the impact of ImpCC variability on defibrillation success. Secondary outcome measures were return of spontaneous circulation and survival. RESULTS: Among 835 treated OHCAs, 680 met inclusion criteria and 565 matched long-term outcomes. ImpCC was significantly higher in patients with unsuccessful defibrillation compared to those with successful defibrillation (p = .0002). Lower ImpCC variability was associated with successful defibrillation with an odds ratio (OR) of 0.993 (95% confidence interval [95% CI], 0.989-0.998, p = .003), while the standard chest compression fraction (CCF) was not associated (OR 1.008 [95 % CI, 0.992-1.026, p = .33]). Neither ImpCC nor CCF was associated with long-term outcomes. CONCLUSIONS: In this population, consistency of chest compression maneuver, measured by variability in TTI, was an independent predictor of defibrillation outcome. ImpCC may be a useful novel metrics for improving quality of care in OHCA.

Cardiac hemodynamics phenotypes and individual responses to training in coronary heart disease patients.

BACKGROUND: In patients with coronary heart disease (CHD), individualized exercise training (ET) programs are strongly recommended to optimize peak oxygen uptake ( V ̇ $$ \dot{\mathrm{V}} $$ O2peak) improvement and prognosis. However, the cardiac hemodynamic factors responsible for a positive response to training remain unclear. The aim of this study was to compare cardiac hemodynamic changes after an ET program in responder (R) versus non-responder (NR) CHD patients. METHODS: A total of 72 CHD patients completed a 3-month ET program and were assessed by cycle ergometer cardiopulmonary exercise test (CPET: V ̇ $$ \dot{\mathrm{V}} $$ O2peak assessment) with impedance cardiography (ICG) for hemodynamic measurements before and after training. Cardiac hemodynamics (e.g., CO, CI, SV, ESV, EDV, and SVR) were measured by ICG during CPET. The R and NR groups were classified using the median change in V ̇ $$ \dot{\mathrm{V}} $$ O2peak (>the median for R and ≤the median for NR). RESULTS: In the R group, V ̇ $$ \dot{\mathrm{V}} $$ O2peak (+17%, p < 0.001), CO, CI, SV, and HR increased by 17%, 17%, 13%, and 5%, respectively (p < 0.05) after the training program. In the NR group, V ̇ $$ \dot{\mathrm{V}} $$ O2peak, CO, CI, and SV increased by 0.5%, 5%, 8%, and 6%, respectively (p < 0.01). The SVR decreased in both groups (-19% in R and -11% in NR, p < 0.001). CONCLUSION: Among CHD patients, the R group showed a better improvement in peak cardiac output via an increase in peak stroke volume and heart rate and a reduced systemic vascular resistance than the NR group. Different cardiac phenotype adaptations and clinical individual responses were identified in CHD patients according to the aerobic fitness responder's status.

Continuous non-invasive measurement of cardiac output in neonatal intensive care using regional impedance cardiography: a prospective observational study.

OBJECTIVES: To compare agreement between echocardiography and regional impedance cardiography (RIC)-derived cardiac output (CO), and to construct indicative normative ranges of CO for gestational age groups. DESIGN, SETTING AND PARTICIPANTS: Prospective cohort observational study performed in a tertiary centre in London, UK, including neonates born between 25 and 42 weeks' gestational age. EXPOSURES: Neonates on the postnatal ward had 2 hours of RIC monitoring; neonates in intensive care had RIC monitoring for the first 72 hours, then weekly for 2 hours, with concomitant echocardiography measures. MAIN OUTCOMES AND MEASURES: RIC was used to measure CO continuously. Statistical analyses were performed using R (V.4.2.2; R Core Team 2022). RIC-derived CO and echocardiography-derived CO were compared using Pearson's correlations and Bland-Altman analyses. Differences in RIC-derived CO between infants born extremely, very and late preterm were assessed using analyses of variance and mixed-effects modelling. RESULTS: 127 neonates (22 extremely, 46 very, 29 late preterm and 30 term) were included. RIC and echocardiography-measured weight-adjusted CO were correlated (r=0.62, p<0.001) with a Bland-Altman bias of -31 mL/min/kg (limits of agreement -322 to 261 mL/min/kg). The RIC-derived CO fell over 12 hours, then increased until 72 hours after birth. The 72-hour weight-adjusted mean CO was higher in extremely preterm (424±158 mL/min/kg) compared with very (325±131 mL/min/kg, p<0.001) and late preterm (237±81 mL/min/kg, p<0.001) neonates; this difference disappeared by 2-3 weeks of age. CONCLUSIONS: RIC is valid for continuous, non-invasive CO measurement in neonates. Indicative normative CO ranges could help clinicians to make more informed haemodynamic management decisions, which should be explored in future studies. TRIAL REGISTRATION NUMBER: NCT04064177.

Differential hemodynamic adaptations to tilt test in patients with idiopathic atrial fibrillation.

The hemodynamic response during the transition from the supine to standing position in idiopathic atrial fibrillation (AF) patients is not completely understood. This study aimed to analyze the hemodynamic changes that occur during the head-up tilt test in idiopathic AF patients. We investigated the hemodynamic changes during the head-up tilt test with impedance cardiography in 40 AF patients (12 with AF rhythm-AFr and 28 with sinus rhythm-AFsr) and 38 non-AF controls. Patients with AFr had attenuated SVI decrease after standing when compared to AFsr and non-AF [ΔSVI in mL/m2: -1.3 (-3.4 to 1.7) vs. -6.4 (-17.3 to -0.1) vs. -11.8 (-18.7 to -8.0), respectively; p < 0.001]. PVRI decreased in AFr but increased in AFsr and non-AF [ΔPVRI in dyne.seg.m2/cm5: -477 (-1148 to 82.5) vs. 131 (-525 to 887) vs. 357 (-29 to 681), respectively; p < 0.01]. Similarly, compared with non-AF patients, AFr patients also had a greater HR and greater CI increase after standing. The haemodynamic response to orthostatic challenge suggests differential adaptations between patients with AF rhythm and those reverted to sinus rhythm or healthy controls. Characterizing the hemodynamic phenotype may be relevant for the individualized treatment of AF patients.

Long-term myocardial effects of noninvasive ventilation in patients with obesity hypoventilation syndrome.

INTRODUCTION: Chronic effects of noninvasive ventilation on myocardial function in patients with obesity hypoventilation syndrome (OHS) are scarcely understood. The aim of the present study was to evaluate the long-term effects of volume-targeted bilevel positive airway pressure ventilation (BiPAP) on cardiac parameters and myocardial biomarkers in patients with OHS. METHODS: Clinically stable patients with OHS referred to the tertiary center for the initiation of long-term BiPAP therapy were consecutively enrolled. At baseline, all participants underwent overnight cardiorespiratory polygraphy. BiPAP therapy using volume-targeted spontaneous/timed mode delivered via an oro-nasal mask was initiated. Beat-to-beat noninvasive monitoring by impedance cardiography was used to assess heart function at baseline and after 3 and 12 months of BiPAP use. Serum troponin 1, N-Terminal Pro-B-Type Natriuretic Peptide (NT-ProBNP), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) were monitored. RESULTS: Thirteen patients (10 men; mean age, 55.8 ± 9.8 years; mean body mass index of 47.8 ± 5.9 kg/m2) were recruited. From baseline to 3, and to 12 months of BiPAP use, left ventricular stroke volume (SV), ejection time (LVET), and ejection time index significantly increased (P = 0.030; P < 0.001; P = 0.003, respectively), while heart rate and systolic time ratio significantly decreased (P = 0.004; P = 0.034, respectively). Reductions in serum NT-proBNP, IL-6 and TNF-α were observed (P = 0.045; P = 0.018; P = 0.003, respectively). No significant changes in serum troponin were detected throughout the study. CONCLUSIONS: The present findings of increased SV, in association with lengthening of LVET, reductions of NT-proBNP and reductions in circulatory inflammatory markers in patients with stable OHS and chronic moderate-to-severe daytime hypercapnia treated with BiPAP over 1 year support the role of this therapeutic mode in such patients.

Non-Invasive Assessment of Cardiodynamics by Impedance Cardiography during the Six-Minute Walk Test in Patients with Heart Failure. / Avaliação Cardiodinâmica Não Invasiva por Cardiografia de Impedância durante o Teste de Caminhada de Seis Minutos em Pacientes com Insuficiência Cardíaca.

BACKGROUND: Central Illustration: Non-Invasive Assessment of Cardiodynamics by Impedance Cardiography during the Six-Minute Walk Test in Patients with Heart Failure. The six-minute walk test (6MWT) is commonly used to evaluate heart failure (HF) patients. However, several clinical factors can influence the distance walked in the test. Signal-morphology impedance cardiography (SM-ICG) is a useful tool to noninvasively assess hemodynamics. OBJECTIVE: This study aimed to compare cardiac output (CO), heart rate (HR), and stroke volume (SV) acceleration and deceleration responses to 6MWT in individuals with HF and reduced ejection fraction (HFrEF) and healthy controls. METHODS: This is a cross-sectional observational study. CO, HR, SV and cardiac index (CI) were evaluated before, during, and after the 6MWT assessed by SM-ICG. The level of significance adopted in the statistical analysis was 5%. RESULTS: Twenty-seven participants were included (13 HFrEF and 14 healthy controls). CO and HR acceleration significantly differed between groups (p<0.01; p=0.039, respectively). We found significant differences in SV, CO and CI between groups (p<0.01). Linear regression showed an impaired SV contribution to CO change in HFrEF group (22.9% versus 57.4%). CONCLUSION: The main finding of the study was that individuals with HFrEF showed lower CO and HR acceleration values during the submaximal exercise test compared to healthy controls. This may indicate an imbalance in the autonomic response to exercise in this condition.

FUNDAMENTO: Figura Central: Avaliação Cardiodinâmica Não Invasiva por Cardiografia de Impedância durante o Teste de Caminhada de Seis Minutos em Pacientes com Insuficiência Cardíaca. O Teste de Caminhada de seis Minutos (TC6M) é comumente usado para avaliar pacientes com insuficiência cardíaca. No entanto, vários fatores clínicos podem influenciar a distância percorrida pelos pacientes no teste. A cardiografia de impedância (CI) na avaliação morfológica é uma ferramenta útil para avaliar a hemodinâmica cardíaca de maneira não invasiva. OBJETIVO: Este estudo teve como objetivo comparar as respostas de aceleração e desaceleração do Débito Cardíaco (DC), da Frequência Cardíaca (FC), e do Volume Sistólico (VS) ao TC6M de indivíduos com insuficiência cardíaca e fração de ejeção reduzida (ICFEr) com as de controles sadios. MÉTODOS: Este é um estudo transversal observacional. O DC, a FC, o VS e o Índice Cardíaco (IC) foram avaliados antes, durante e após o TC6M por CI. O nível de significância adotado na análise estatística foi 5%. RESULTADOS: Foram incluídos 27 participantes (13 com ICFEr e 14 controles sadios). A aceleração do DC e da FC foi significativamente diferente entre os grupos (p<0,01 e p=0,039, respectivamente). Encontramos diferenças significativas no VS, no DC e no IC entre os grupos (p<0,01). A regressão linear mostrou uma contribuição deficiente do VS à mudança no DC no grupo com ICFEr (22,9% versus 57,4%). CONCLUSÃO: O principal resultado deste estudo foi o fato de que indivíduos com ICFEr apresentaram valores mais baixos de aceleração do DC e da FC durante o teste de exercício submáximo em comparação a controles sadios. Isso pode indicar um desequilíbrio na resposta autonômica ao exercício nessa condição.

Caracterización hemodinámica de pacientes con diagnóstico de hipertensión arterial y síndrome de apneas hipopneas obstructivas del sueño / Hemodynamic characterization of patients with diagnosis of arterial hypertension and obstructive sleep apnea hypopnea syndrome

Introducción. La hipertensión arterial (HTA) y el síndrome de apnea e hipopnea obstructiva del sueño (SAHOS) presentan alta prevalencia y relación. La HTA predispone a insuficiencia cardíaca, infarto de miocardio, insuficiencia renal y accidente cerebrovascular, mientras que el SAHOS es un problema sanitario emergente asociado a mayor morbimortalidad, por accidentes de tránsito y complicaciones cardiovasculares. El objetivo de este estudio es describir las características hemodinámicas de pacientes con diagnóstico de HTA y SAHOS. Material y métodos. Estudio observacional. Se incluyeron pacientes con diagnóstico reciente de HTA y SAHOS sin tratamiento. Se dividieron en tres categorías: HTA sin SAHOS, HTA con SAHOS y un grupo control de normotensos con SAHOS. Se realizó el diagnóstico mediante el registro de la presión arterial de consultorio y el monitoreo ambulatorio de la presión arterial. El patrón hemodinámico y el contenido de fluido torácico (CFT) fueron evaluados por cardiografía por impedancia (CGI) y se diagnosticó SAHOS por poligrafía respiratoria ambulatoria. Resultados. Los pacientes con HTA y SAHOS presentaron un patrón hemodinámico vasoconstrictor y valores superiores de TFC respecto de los normotensos con SAHOS y HTA sin SAHOS. Conclusión. Los resultados obtenidos sugieren mayor compromiso de los sistemas simpático y renina angiotensina aldosterona. Estos hallazgos brindan nuevas hipótesis para continuar esta línea de investigación con mayor número de pacientes.(AU)

Impedance cardiography in the evaluation of patients with arterial hypertension / Impedância cardiografica na avaliação de pacientes com hipertensão arterial

Arterial hypertension is responsible for high morbidity and mortality. Despite increasing awareness of the consequences of uncontrolled hypertension and the publication of several recommendations and guidelines, blood pressure control rates are suboptimal, and approximately half of the patients do not reach the targets. Defined as an increase in blood pressure, hypertension is characterized by hemodynamic abnormalities in cardiac output, systemic vascular resistance, or arterial compliance. Therefore, the approach to arterial hypertension can be improved by the knowledge of the hemodynamics underlying the blood pressure increase. Impedance Cardiography has emerged as a new strategy to customize therapy and monitor patients aiming to improve blood pressure control according to the hemodynamic profile, rather than a blind intensive care approach. This is a review of impedance cardiography evidence, its benefits, actual and future applications in the approach and management of arterial hypertension

Heart Rate Variability Analysis Based on Photoplethysmographic Signals

An algorithm for extracting tachograms for Heart Rate Variability (HRV) analysis on the basis of Photoplethysmographic (PPG) signals (instead of electro cardiograms) has been proposed. The main feature of this proposal is to detect peaks from correlograms between a pattern waveform and a sliding time window in the PPG signal. Analysis was carried out with a set of two groups of patients (young and elderly).HRV variables were estimated using the publicly available Kubios HRV package. Results showed that both the sympathetic component of the autonomous nervous system (assessed by LF/HF) and the cardiovascular complexity (assessed by correlation dimension) are reduced with age. These results are supported by literature and may be taken as a support for the validity of the proposed algorithm. Since oximeters for getting PPG signals are affordable even in poor settings, this allows extending autonomic nervous system studies into remote areas of developing countries(AU)

Se propone un algoritmo para obtener tacogramas con la finalidad de realizar estudios de variabilidad de la frecuencia cardiaca, partiendo de registros de señales fotopletismográficas (PPG). La principal peculiaridad de esta propuesta lo es la detección de los picos en las ondas de la señal PPG a partir de un correlograma obtenido como una secuencia de correlaciones entre una onda patrón y una ventana deslizante de la señal PPG. Se realizó un análisis de variabilidad de frecuencia cardiaca sobre dos grupos de pacientes (jóvenes y de avanzada edad). Las variables de variabilidad de frecuencia cardiaca seleccionadas se obtuvieron a partir del programa Kubios HRV, de acceso público y gratuito. Los resultados mostraron que tanto el componente simpático del Sistema Nervioso Autónomo (evaluado a través de la variable LF/HF) como la complejidad cardiovascular (evaluada a través de la dimensión de correlación) disminuyeron con la edad. Estos resultados encuentran apoyo en datos de la literatura que apoyan así la validez del algoritmo propuesto. Por cuanto el oxímetro utilizado para obtener las señales PPG está al alcance de instituciones primarias de salud se hace posible de esta manera extender estudios del sistema nervioso autónomo hacia áreas remotas de países en desarrollo(AU)

Bioimpedância transtorácica comparada à ressonância magnética na avaliação do débito cardíaco / Transthoracic impedance compared to magnetic resonance imaging in the assessment of cardiac output

FUNDAMENTO: A ressonância magnética cardíaca é considerada o método padrão-ouro para o cálculo de volumes cardíacos. A bioimpedância transtorácica cardíaca avalia o débito cardíaco. Não há trabalhos que validem essa medida comparada à ressonância. OBJETIVO: Avaliar o desempenho da bioimpedância transtorácica cardíaca no cálculo do débito cardíaco, índice cardíaco e volume sistólico, utilizando a ressonância como padrão-ouro. MÉTODOS: Avaliados 31 pacientes, com média de idade de 56,7 ± 18 anos, sendo 18 (58%) do sexo masculino. Foram excluídos os pacientes cuja indicação para a ressonância magnética cardíaca incluía avaliação sob estresse farmacológico. A correlação entre os métodos foi avaliada pelo coeficiente de Pearson, e a dispersão das diferenças absolutas em relação à média foi demonstrada pelo método de Bland-Altman. A concordância entre os métodos foi realizada pelo coeficiente de correlação intraclasses. RESULTADOS: A média do débito cardíaco pela bioimpedância transtorácica cardíaca e pela ressonância foi, respectivamente, 5,16 ± 0,9 e 5,13 ± 0,9 L/min. Observou-se boa correlação entre os métodos para o débito cardíaco (r = 0,79; p = 0,0001), índice cardíaco (r = 0,74; p = 0,0001) e volume sistólico (r = 0,88; p = 0,0001). A avaliação pelo gráfico de Bland-Altman mostrou pequena dispersão das diferenças em relação à média, com baixa amplitude dos intervalos de concordância. Houve boa concordância entre os dois métodos quando avaliados pelo coeficiente de correlação intraclasses, com coeficientes para débito cardíaco, índice cardíaco e volume sistólico de 0,78, 0,73 e 0,88, respectivamente (p < 0,0001 para todas as comparações). CONCLUSÃO: A bioimpedância transtorácica cardíaca mostrou-se acurada no cálculo do débito cardíaco quando comparada à ressonância magnética cardíaca.

BACKGROUND: Cardiac magnetic resonance imaging is considered the gold-standard method for the calculation of cardiac volumes. Transthoracic impedance cardiography assesses the cardiac output. No studies validating this measurement, in comparison to that obtained by magnetic resonance imaging, are available. OBJECTIVE: To evaluate the performance of transthoracic impedance cardiography in the calculation of the cardiac output, cardiac index and stroke volume using magnetic resonance imaging as the gold-standard. METHODS: 31 patients with a mean age of 56.7 ± 18 years were assessed; of these, 18 (58%) were males. Patients whose indication for magnetic resonance imaging required pharmacologic stress test were excluded. Correlation between methods was assessed using the Pearson's coefficient, and dispersion of absolute differences in relation to the mean was demonstrated using the Bland-Altman's method. Agreement between methods was analyzed using the intraclass correlation coefficient. RESULTS: The mean cardiac output by transthoracic impedance cardiography and by magnetic resonance imaging was 5.16 ± 0.9 and 5.13 ± 0.9 L/min, respectively. Good agreement between methods was observed for cardiac output (r = 0.79; p = 0.0001), cardiac index (r = 0.74; p = 0.0001) and stroke volume (r = 0.88; p = 0.0001). The analysis by the Bland-Altman plot showed low dispersion of differences in relation to the mean, with a low amplitude of agreement intervals. Good agreement between the two methods was observed when analyzed by the intraclass correlation coefficient, with coefficients for cardiac output, cardiac index and stroke volume of 0.78, 0.73 and 0.88, respectively (p < 0.0001 for all comparisons). CONCLUSION: Transthoracic impedance cardiography proved accurate in the calculation of the cardiac output in comparison to cardiac magnetic resonance imaging.

Avaliação hemodinâmica na insuficiência cardíaca: papel do exame físico e dos métodos não invasivos / Hemodynamic assessment in heart failure: role of physical examination and noninvasive methods / Evaluación hemodinámica en la insuficiencia cardíaca: papel del examen físico y de los métodos no invasivos

Entre as doenças cardiovasculares, a insuficiência cardíaca (IC) apresenta elevada taxa de internação hospitalar, morbidade e mortalidade, consumindo grandes recursos financeiros do sistema de saúde no Brasil e em outros países. A correta determinação das pressões de enchimento do ventrículo esquerdo, por avaliação invasiva ou não invasiva, é fundamental para o adequado tratamento dos pacientes com IC crônica descompensada, considerando que a congestão é o principal fator determinante dos sintomas e da hospitalização. O exame físico tem se mostrado inadequado para prever o padrão hemodinâmico. Vários estudos sugerem que a concordância em achados de exame físico por diferentes médicos é pequena e que, por fim, as próprias alterações fisiológicas adaptativas na IC crônica mascaram importantes aspectos do exame físico. Como a avaliação clínica falha em prever a hemodinâmica e pelo fato de a utilização do cateter de Swan-Ganz de rotina não ser recomendada para esse fim em pacientes com IC, métodos de avaliação hemodinâmica não invasivos, como o BNP, o ecocardiograma e a bioimpedância cardiográfica, vêm sendo crescentemente utilizados. O presente trabalho tem por objetivo realizar, para o clínico, uma revisão da função de cada uma dessas ferramentas, na definição da condição hemodinâmica em que se encontram os pacientes com IC descompensada, visando a um tratamento mais racional e individualizado.

Among the cardiovascular diseases, heart failure (HF) has a high rate of hospitalization, morbidity and mortality, consuming vast resources of the public health system in Brazil and other countries. The correct determination of the filling pressures of the left ventricle by noninvasive or invasive assessment is critical to the proper treatment of patients with decompensated chronic HF, considering that congestion is the main determinant of symptoms and hospitalization. Physical examination has shown to be inadequate to predict the hemodynamic pattern. Several studies have suggested that agreement on physical findings by different physicians is small and that, ultimately, adaptive physiological alterations in chronic HF mask important aspects of the physical examination. As the clinical assessment fails to predict hemodynamic aspects and because the use of Swan-Ganz catheter is not routinely recommended for this purpose in patients with HF, noninvasive hemodynamic assessment methods, such as BNP, echocardiography and cardiographic bioimpedance, are being increasingly used. The present study intends to carry out, for the clinician, a review of the role of each of these tools when defining the hemodynamic status of patients with decompensated heart failure, aiming at a more rational and individualized treatment.

Entre las enfermedades cardiovasculares, la insuficiencia cardíaca (IC) presenta una elevada tasa de ingreso hospitalario, morbilidad y mortalidad, consumiendo enormes recursos financieros del sistema de sanidad en Brasil, y de otros países. La correcta determinación de las presiones en el llenado del ventrículo izquierdo, por evaluación invasiva o no invasiva, es fundamental para el adecuado tratamiento de los pacientes con IC crónica descompensada, considerando que la congestión es el principal factor determinante de los síntomas y del ingreso. El examen físico ha sido inadecuado para prever el estándar hemodinámico. Varios estudios sugieren que la concordancia en los hallazgos del examen físico por diferentes médicos es pequeña y que, las propias alteraciones fisiológicas adaptativas en la IC crónica, disimulan los importantes aspectos del examen físico. Como la evaluación clínica falla a la hora de prevenir la hemodinámica, y también por el hecho de que la utilización del catéter de Swan-Ganz de rutina no se recomiende con ese fin en los pacientes con IC, los métodos de evaluación hemodinámica no invasivos, como el PNB, el ecocardiograma y la bioimpedancia cardiográfica, están en aumento. Este trabajo pretende realizar, a favor del médico, una revisión de la función de cada una de esas herramientas, para definir la condición hemodinámica en que están los pacientes con IC descompensada, objetivando un tratamiento más racional e individualizado.

Evaluación hemodinámica no invasiva con cardiografía de impedancia: aplicaciones en falla cardíaca y en hipertensión arterial / Non-invasive hemodynamic evaluation with impedance cardiography: applications in heart failure and hypertension

La cardiografía de impendancia (CGI) representa un método no invasivo para la evaluación del estado hemodinámico latido a latido. Aunque se introdujo por primera vez hace más de 40 años, la CGI ha mostrado un resurgimiento en la última década, a partir de una serie de estudios clínicos que han demostrado su precisión en la estimación del volumen latido, tanto contra el "gold-standard" invasivo (termodilución), como contra los métodos de referencia no invasivos (ecocardiografía). Diversos estudios demuestran la utilidad de esta técnica en el manejo del paciente con falla cardíaca y en el enfoque diagnóstico y terapéutico de la hipertensión arterial, por lo cual constituyen actualmente dos de las aplicaciones clínicas más importantes de la CGI. En falla cardiaca, los cambios en el volumen de líquido del tórax y del gasto cardíaco evaluados por CGI, han demostrado ser predictores de descompensación aguda, incluso semanas antes del inicio de la sintomatología respiratoria; además, permiten identificar el origen cardiogénico o respiratorio de la disnea cuando el examen físico y los demás paraclínicos no son concluyentes. En los pacientes con hipertensión arterial no controlada o resistente, la CGI permite realizar una mejor caracterización del fenotipo hipertensivo y elegir la estrategia farmacológica más específica para intervenir la alteración hemodinámica predominante (resistencia vascular vs. gasto cardiaco elevado). En este artículo se realiza una revisión de los principios biofísicos de la CGI y su utilidad en la evaluación no invasiva del estado hemodinámico, así como una evaluación crítica de la literatura que da soporte a su aplicación clínica en el tratamiento de la falla cardíaca y la hipertensión arterial.

Impedance cardiography (ICG) represents a non-invasive method for hemodynamic assessment in a beat-to-beat basis. Since its introduction more than forty years ago, a renewed interest in the use of this technique during the last decade has been noticed, mainly as a result of a series of clinical studies showing its precision in the estimation of stroke volume either against invasive gold standard (i.e. thermodilution) or against non-invasive reference methods (i.e. echocardiography). On the other hand, ICG has demonstrated to be useful for the management of heart failure patients and for the diagnostic and therapeutic approach to hypertension, which currently constitute two of the major applications of ICG. In heart failure patients, changes in thoracic fluid content and cardiac output tracked by ICG have shown to be predictors of acute decompensation even weeks before respiratory symptoms appear; also allowing identification of a cardiac vs. respiratory origin of dyspnea when physical examination and laboratory tests are not conclusive. In the particular case of patients with uncontrolled or severe hypertension, ICG makes possible a better characterization of hypertensive phenotype leading to a more specific choice of pharmacological agents to treat the primary hemodynamic alteration (i.e elevated peripheral resistance vs. elevated cardiac output). The present review, provides a review of the biophysical principles of ICG and its precision in measuring stroke volume and present a critical assessment of the literature supporting its clinical application in the management of heart failure and arterial hypertension.

Principios de la evaluación hemodinámica no invasiva con cardiografía de impedancia / Principles of non-invasive hemodynamic assessment with impedance cardiography

La cardiografía de impedancia es una técnica no invasiva que permite una determinación rápida, continua y reproducible del gasto cardiaco latido a latido. Mide los cambios en la resistencia eléctrica del tórax que se producen por las variaciones en el volumen sanguíneo en la aorta durante el ciclo cardiaco. La medición continua del cambio en la impedancia o las fluctuaciones del volumen sanguíneo durante la sístole y la diástole, permite determinar el volumen latido, el gasto cardiaco, la contractilidad miocárdica y el contenido total de fluido del tórax. Entre las ventajas de esta técnica se incluyen su fácil implementación y asequibilidad, así como la posibilidad de ser realizada por prácticamente cualquier miembro del equipo de salud. La precisión de la cardiografía de impedancia ha sido validada en numerosos estudios en diferentes escenarios clínicos: hipertensión arterial, falla cardiaca, hipertensión pulmonar, optimización de la terapia de resincronización cardiaca y en pacientes críticos, situaciones en las que provee información sobre el estado hemodinámico sin los riesgos de otras técnicas invasivas o mínimamente invasivas. Es además un método de fácil aplicación y costo-efectivo para el diagnóstico y seguimiento de la respuesta a las intervenciones terapéuticas en múltiples patologías. La técnica representa así un cambio en los paradigmas del monitoreo hemodinámico.

Impedance cardiography (ICG) is a non-invasive technique that allows a rapid, continuous and reproducible beat-to-beat cardiac output estimation. This technique measures thoracic electrical resistance changes produced by variations in the blood volume in the aorta during the cardiac cycle. Continuous measurement of impedance changes or fluctuations of blood volume during systole and diastole allow the determination of stroke volume, cardiac output, myocardial contractility, and total thoracic fluid content. Between the advantages of this technique are included its easy implementation and accessibility, as well as the possibility of its measurement by practically any member of the health team. Impedance cardiography accuracy has been validated in several clinical scenarios such as arterial hypertension, heart failure, pulmonary hypertension, optimization of cardiac resynchronization therapy, and in critically ill patients, situations where it provides information about the hemodynamic state without the risks and costs of other invasive or minimally invasive techniques. It is also an easy to use, cost-effective method for the diagnosis and follow-up of the response to therapeutic interventions in multiple clinical scenarios. Thus, this technology represents a change in the paradigms of hemodynamic monitoring.

O uso dos índices de impedância da artéria esplênica na avaliação da hipertensão portal / Utilization of splenic impedance indices in the evaluation of portal hypertension

OBJETIVO: Estudar os índices de impedância - índices de resistência (IR) e pulsatilidade (IP) - da artéria esplênica em pacientes com hepatopatia crônica. MATERIAIS E MÉTODOS: Foram estudados, prospectivamente, 42 pacientes com cirrose hepática e 21 pacientes com hepatite crônica. RESULTADOS: Foi observado que, nos pacientes com cirrose, ambos os índices estiveram elevados (IR = 0,63 ± 0,08 e IP = 1,02 ± 0,22) em comparação com os pacientes com hepatite crônica (IR = 0,58 ± 0,06 e IP = 0,89 ± 0,15) e os indivíduos do grupo controle (IR = 0,57 ± 0,04 e IP = 0,87 ± 0,11). Os cirróticos com evidência de circulação colateral à ultra-sonografia apresentaram, no entanto, menores índices de resistência (IR = 0,60 ± 0,08) em comparação com os cirróticos sem circulação colateral (IR = 0,65 ± 0,07), possivelmente devido ao shunt portossistêmico provocado pelos vasos colaterais. Não houve diferença significativa dos índices entre pacientes com e sem varizes esofagianas. CONCLUSÃO: O trabalho demonstrou que os índices de impedância da artéria esplênica podem ser úteis na avaliação de pacientes com hepatopatia crônica e hipertensão portal, contribuindo com dados adicionais à ultra-sonografia com eco-Doppler colorido.

OBJECTIVE: The aim of the present study was to analyze splenic impedance indices - resistive index (RI) and pulsatility index (PI) - in patients with chronic liver disease. MATERIALS AND METHODS: Forty-two patients with hepatic cirrhosis and 21 patients with chronic hepatitis were prospectively evaluated. RESULTS: In patients with cirrhosis, both indices were higher (RI = 0.63 ± 0.08; PI = 1.02 ± 0.22) than those found in patients with chronic hepatitis (RI = 0.58 ± 0.06; PI = 0.89 ± 0.15) and in the control group individuals (RI = 0.57 ± 0.04; PI = 0.87 ± 0.11). However, cirrhotic patients with evidence of collateral circulation at ultrasound presented lower resistive indices (RI = 0.60 ± 0.08) compared with those without collateral circulation (RI = 0.65 ± 0.07), possibly due to the portosystemic shunt caused by collateral vessels. There was no significant difference of indices between patients with and without esophageal varices. CONCLUSION: The present study has demonstrated that splenic artery impedance indices may be useful in the evaluation of patients affected by chronic liver disease and portal hypertension, contributing with additional data at color Doppler ultrasound.

Estimativa não-invasiva do débito cardíaco durante o exercício a partir de impedância cardiográfica e consumo de oxigênio em idosos / Non-invasive estimate of cardiac output during exercise based on impedance cardiography and oxygen uptake in the elderly

OBJETIVO: O presente estudo analisou a concordância entre as estimativas do débito cardíaco (Q) geradas por dois métodos indiretos e sua aplicabilidade em 54 homens e 77 mulheres (60-90 anos). MÉTODOS: Os indivíduos realizaram um teste cardiopulmonar de exercício progressivo máximo em ciclo-ergômetro. O Q foi estimado a partir do consumo de oxigênio e da impedância cardiográfica a 50 por cento e 100 por cento da carga máxima alcançada no teste (Wmáx). Os limites de concordância e as diferenças médias (vieses) foram avaliados segundo a metodologia proposta por Bland e Altman, enquanto a relação entre os métodos foi analisada por regressão linear e correlação intraclasse (ICC). RESULTADOS: Na carga equivalente a 50 por cento Wmáx, a diferença entre as médias dos métodos foi de -0,58 Lòmin-1 (6,3 por cento menor para a medida da impedância), e o limite de concordância de ± 2,54 Lòmin-1 (24,7 por cento). Em 100 por cento Wmáx, a diferença foi de 1,03 Lòmin-1 (8,5 por cento maior para a medida da impedância), com um limite de concordância de ± 3,35 Lòmin-1 (27,6 por cento). Os valores de ICC e as curvas de regressão obtidas entre os métodos foram: Qimp=1,82+0,75Q VO2 (r²=0,765, p<0,001; ICC=0,727, p<0,01) para 50 por cento Wmáx; Qimp=0,93+1,00Q VO2 (r²=0,755, p<0,001; ICC=0,796, p<0,01) para 100 por cento Wmáx. CONCLUSÃO: Os resultados sugerem uma boa concordância na estimativa do Q no exercício em idosos pelos dois métodos, o que se revela compatível com os achados de estudos similares com indivíduos jovens.

OBJECTIVE: This study assessed the agreement between cardiac output (Q) measurements generated by two indirect methods and their applicability in 54 men e 77 women (aged 60-90). METHODS: The subjects performed a cardiopulmonary test with incremental to maximal exercise on a cycle-ergometer. "Q" was estimated based on oxygen uptake and on impedance cardiography at 50 percent and 100 percent of the maximal workload (Wmax) reached during the test. The limits of agreement and mean differences (biases) were estimated using the methodology proposed by Bland-Altman, whereas the relationship between the methods was analyzed by linear regression and intra-class correlation (ICC). RESULTS: For the load equivalent do 50 percent of Wmax, the bias between the means of the two methods was -0.58 Lòmin-1 (6.3 percent smaller for the impedance measurement) and the limit of agreement was ± 2.54 Lòmin-1 (24.7 percent). At 100 percent of Wmax, the bias was 1.03 Lòmin-1 (8.5 percent greater for the impedance measurement) with a limit of agreement of ± 3.35 Lòmin-1 (27.6 percent). ICC values and the regression curves obtained between the methods were: Qimp=1.82+0.75Q VO2 (r²=0.765, p<0.001; ICC=0.727, p<0.01) at 50 percent Wmax; and Qimp=0.93+1.00Q VO2 (r²=0.755, p<0.001; ICC=0.796, p<0.01) at 100 percent Wmax. CONCLUSION: These results suggest that there is a good agreement between the two methods for the measurement of Q during exercise in the elderly, which is compatible with the findings of similar studies with young subjects.