Changes In Cardiac Output Research Articles

High variability in the reproducibility of key hemodynamic responses to head-up tilt.

Increased blood pressure upon standing is considered a cardiovascular risk factor. We investigated the reproducibility of changes in aortic blood pressure, heart rate, stroke volume, cardiac output, and systemic vascular resistance during three passive head-up tilts (HUT) in 223 participants without cardiovascular medications (mean age 46 years, BMI 28 kg/m2, 54% male). Median time gap between the first and the second HUT was 9 weeks and the second and the third HUT 4 weeks. We utilized whole-body impedance cardiography and radial artery tonometry as methods. The participants were divided into quartiles of the changes in each hemodynamic variable during the first HUT, and the reproducibility of these changes was tested during successive HUTs. During the first HUT, significant differences were present in all between-quartile comparisons (n=6) of all variables. The differences persisted as follows: reduction of stroke volume in six out of six (6/6) between-quartile comparisons (p<0.001), decrease in cardiac output (p<0.001) and increase in heart rate in 5/6 comparisons (p<0.001), change in systemic vascular resistance in 3/6 comparisons (p<0.001), change in aortic systolic blood pressure in 1/6 comparisons (p=0.043), and change in aortic diastolic blood pressure in none (p=0.266). To conclude, the reproducibility of upright posture-induced changes is high for stroke volume, cardiac output, and heart rate, moderate for systemic vascular resistance, and modest for aortic blood pressure. While an increase in blood pressure during upright posture may be a cardiovascular risk factor, this effect may be attributed to other underlying hemodynamic variables that exhibit more reproducible posture-related changes.

Assessment of transpulmonary thermodilution, ultrasound dilution, and esophageal Doppler against direct pulmonary artery flow for cardiac output monitoring in anesthetized cats.

To assess the agreement of transpulmonary thermodilution (TPTD) and transpulmonary ultrasound dilution (TPUD) against direct measurement of main pulmonary artery flow with an ultrasound transit time flow probe (UTF) over a wide range of conditions in anesthetized cats. Additionally, the trending ability of TPTD, TPUD, and esophageal Doppler ultrasonography (EDU) was evaluated against UTF. 12 purpose-bred cats were used. One cat was used for a pilot study. The cats were instrumented according to the manufacturer's recommendation. Paired measurements were made over a wide range of cardiac output. Agreement was analyzed with Bland-Altman analysis with repeated measures, and trending ability was assessed by 4-quadrant plot and concordance rate. Interchangeable was defined as percentage error less than simplified total error. Acceptable trending was defined as concordance rate > 95%. Bias and percentage error were -0.084 L·min-1 and 38.2% for TPTD and -0.041 L·min-1 and 52.9% for TPUD. The concordance rate was 100%, 95.5%, and 64% to 65% for TPTD, TPUD, and EDU, respectively. Both TPTD and TPUD were not interchangeable to UTF. Both TPTD and TPUD provided acceptable trending ability but not EDU. Transpulmonary thermodilution and TPUD allow detection of the direction of cardiac output changes in anesthetized cats but not EDU. Clinical and research use of these 3 devices warrants careful consideration of the limitations presented in this study.

Electrical cardiometry for non-invasive cardiac output monitoring: a method comparison study in patients after coronary artery bypass graft surgery.

Cardiac output can be estimated non-invasively by electrical cardiometry with the ICON® monitor (Osypka Medical GmbH, Berlin, Germany). Conflicting results have been reported regarding the cardiac output measurement performance of electrical cardiometry. In this prospective method comparison study, we compared cardiac output measured using electrical cardiometry (EC-CO; test method) with cardiac output measured using intermittent pulmonary artery thermodilution (PATD-CO; reference method) in patients after coronary artery bypass graft (CABG) surgery. We calculated the mean of the differences with 95%-limits of agreement (95%-LOA) and their corresponding 95%-confidence intervals (95%-CI) using Bland-Altman analysis and calculated the percentage error. We also analyzed trending using four-quadrant plot analysis. We analyzed 157 paired cardiac output measurements of 41 patients. Mean ± standard deviation PATD-CO was 5.1 ± 1.3L/min and mean EC-CO was 5.3 ± 1.3L/min. The mean of the differences ± SD between PATD-CO and EC-CO was -0.2 (95%-CI -0.5 to 0.2) ± 1.2L/min with a lower 95%-LOA of -2.6 (95%-CI -3.1 to -2.0) L/min and an upper 95%-LOA of 2.3 (95%-CI 1.6 to 2.9)L/min. The percentage error was 47% (95%-CI, 37 to 56%). The concordance rate for cardiac output changes was 48%. In this study, the agreement between EC-CO and PATD-CO was not clinically acceptable in patients after CABG surgery. The trending ability of EC-CO was poor.

Assessing the Impact of Cardiac Output and Valve Orientation on Bioprosthetic Pulmonary Valve Hemodynamics Using In Vitro 4D-Flow MRI and High-Speed Imaging.

Pulmonary valve replacement (PVR) using bioprosthetic valves is a common procedure performed in patients with repaired Tetralogy of Fallot and other conditions, but these valves frequently become dysfunctional within 15years of implantation. The causes for early valve failure are not clearly understood. The purpose of this study was to explore the impact of changing cardiac output (CO) and valve orientation on local hemodynamics and valve performance. A 25mm bioprosthetic valve was implanted in an idealized 3D-printed model of the right ventricular outflow tract (RVOT). The local hemodynamics at three COs and two valve orientations were assessed using 4D-Flow MRI and high-speed camera imaging. Noticeable differences in jet asymmetry, the amount of recirculation, leaflet opening patterns, as well as the size and location of reversed flow regions were observed with varying CO. Rotation of the valve resulted in drastic differences in reversed flow regions, but not forward flow. Flow features observed in the valve with low CO in this study have previously been correlated with calcification, hemolysis, and leaflet fatigue, indicating their potential negative impact on local hemodynamics and leaflet performance.

Abstract 4136812: Optimal Pacing for Cerebral Perfusion: Elucidating Relationship Between Resting Pacemaker Heart Rate and Pulse Pressure

Background: Cognitive decline and dementia are significant global health concerns, with hypertension being a major risk factor. Increasingly, the elderly population is receiving pacemakers, and the pacing rates are set as low as 50bpm. Moreover, the relationship between blood pressure (BP) components, particularly diastolic BP (DBP) and pulse pressure (PP), and the risk of cognitive decline or dementia remains complex. The highest risk is observed in patients with low DBP and concurrently increased PP, likely indicating vascular stiffness. To our knowledge, no studies have assessed the programming of pacemakers to increase heart rates to target DBP and PP improving cerebral perfusion. Objectives: In patients with permanent pacemakers, resting heart rate (HR) can be artificially increased, and its consequence on hemodynamics, including PP, can be easily measured. This study aims to investigate the impact of increasing resting HR on PP in patients with poor vascular compliance. Secondary outcomes include evaluating changes in DBP, SBP, and cardiac output, as well as assessing patient tolerance to higher-paced heart rates through recording subjective symptoms. Methods: The study will employ a prospective cross-sectional interventional design. Digital plethysmography will be utilized to measure hemodynamic parameters, including systolic blood pressure (SBP), DBP, PP, and cardiac output, at baseline resting-paced heart rates. Subsequently, the pacemaker resting heart rate will be incrementally increased to a final rate of 100 beats per minute (bpm), with measurements taken 2-5 minutes after each change. Results: Ten out of twenty patients were recruited, with a mean age of 75.3 years old. The median change in PP from baseline HR of 70 to 100 was -8.7% (IQR -18.8 - +2.8, p= 0.114), SBP 4.2% (IQR 0 – 11.9, p=0.059), and DBP 20.1% (IQR 12.9 -23, p=0.005). There were no adverse outcomes and no patient-reported symptoms during higher pacing rates. Conclusion: This study provides the basis for proof of concept. Since an increased HR decreases PP, this will be subsequently tested against improvement in cerebral perfusion by cerebral Doppler studies, and its impact on cognitive function will be tested. This has the potential to change the standard of practice for patients with pacemakers and allow for collaboration across multiple specialties such as neurology, geriatric medicine and cardiology.

Space Travel: The Radiation and Microgravity Effects on the Cardiovascular System.

Space flight modulates the functions of the cardiovascular system. The exposure to space conditions can alter the cerebral blood flow, as well as the venous return. Anemia, cardiac output changes, and increased activity of the sympathetic nervous system can also be seen. Understanding cardiac changes prepares astronauts for both better in-flight adaptations and long-term protection against cardiovascular diseases. The heart could undergo radio-degenerative effects when exposed to space radiation, increasing the risk of cardiovascular diseases in the long run. A high frequency of arrhythmias, such as ventricular/atrial premature complexes, have been reported during the Gemini and Apollo missions. Additionally, microgravity can lead to progressive degeneration of the myocytes and muscle atrophy with altered gene expression and calcium handling, along with impaired contractility. This review summarizes the potential cardiovascular effects of spaceflight and prevention measures.

Age-dependent changes in cardiac output following balloon pulmonary angioplasty: Implications for combination therapy in chronic thromboembolic pulmonary hypertension

Abstract Background Balloon pulmonary angioplasty (BPA) is an accepted treatment for patients with chronic thromboembolic pulmonary hypertension (CTEPH). However, some patients still have exercise intolerance even after normalizing mean pulmonary arterial pressure with BPA. Although medical therapy may be a potential option for such patients, it cannot be necessary for all patients. Low cardiac output (CO) after BPA is associated with exercise intolerance. However, the change in CO with BPA could be affected by the patient’s age and pulmonary hypertension (PH) medication status. The specific patients’ characteristics that require medical therapy following BPA remain unknown. Methods This single-centre, retrospective observational study included 286 patients with CTEPH who underwent BPA and right heart catheterization one year BPA at our hospital. The patients were classified into three age groups (younger: age &amp;lt; 60 years, n=91; middle-aged: 60 ≤ age &amp;lt; 70 years, n=91; elderly: 70 years ≤ age, n=104), and also stratified by two groups based on PH medication status (Group 1: patients without PH medications before and after BPA, Group 2: patients who received PH medications before BPA and discontinued them after BPA). CO and its percent change were compared between Groups 1 and 2 in each age group. Results CO increased significantly in the younger group (4.3±0.2 to 4.5±0.1 L/min, p=0.040) and decreased in the elderly group (4.0±0.1 to 3.8±0.1 L/min, p=0.035), resulting in no significant change overall. CO in the younger and middle-aged groups significantly increased after BPA in Group 1, whereas in Group 2, those in the middle-aged and elderly groups significantly decreased after BPA. The percent CO changes declined in an age-dependent manner in both groups. Conclusions Increasing CO with BPA alone may be challenging in elderly patients. Adjuvant medical therapy might be necessary, even after successful BPA, especially in elderly patients.Percent change in CO stratified by age

The value of the dynamic changes in cardiac power output in aortic stenosis patients following transcatheter aortic valve implantation: an exercise stress echocardiography study.

Evidence for risk stratification using exercise stress echocardiography (ESE) in patients undergoing transcatheter aortic valve implantation (TAVI) for severe aortic stenosis (AS) is currently lacking. Cardiac power output (CPO) has demonstrated prognostic value in patients undergoing TAVI for severe AS. This study investigated prognoses in patients undergoing TAVI for severe AS and to explore the additional information that ESE can provide for risk stratification. In this retrospective observational study, we included 96 consecutive patients who underwent TAVI for severe AS and patients with preserved left ventricular (LV) ejection fraction (≥ 50%) who underwent ESE at 3-6months after TAVI. CPO was calculated as 0.222 × cardiac output × mean blood pressure/LV mass, where 0.222 was the conversion constant to W/100g of the LV myocardium. All patients were followed up for all-cause mortality and hospitalization for heart failure. Of the 96 patients, 3 were excluded and 93 patients (82.0years; 45.2% male) were included in this study. During a median follow-up period of 1446 (1271-1825) days, the composite end point was reached in 17 patients. Multivariable Cox regression analysis revealed that CPO at rest and the change in CPO from rest to exercise (ΔCPO) were independently associated with the composite end point (hazard ratio = 0.278, p = 0.023). The addition of ΔCPO resulted in an incremental value of the model containing clinical and resting echocardiography variables (p = 0.030). This study suggests that resting CPO and exercise-induced changes in CPO are useful for risk stratification of patients undergoing TAVI for severe AS.

Evaluation of the Noninvasive Estimated Continuous Cardiac Output System for Pediatric Patients: A Prospective Observational Study.

The estimated continuous cardiac output (esCCO) system is a hemodynamic monitor that uses electrocardiograms and pulse oximeter waves to noninvasively estimate cardiac output. The coefficients for esCCO measurement have been established for adult patients, but the appropriate coefficients for pediatric patients are unclear. Therefore, this study determined esCCO coefficients for pediatric patients and validated the accuracy and tracking ability of a modified esCCO system. An initial study compared cardiac output measurements using transthoracic echocardiography and esCCO in 60 pediatric patients aged <15 years who underwent elective noncardiac surgery. Consequently, the coefficients for the esCCO measurements were redefined for pediatric patients. The main study compared cardiac output measurements between transthoracic echocardiography and modified esCCO in 80 pediatric patients. Measurements were performed pre- and postoperatively, and the accuracy and trending ability of the cardiac output measurements were evaluated using Bland-Altman analysis and a polar plot. The correlation coefficients between the modified esCCO and transthoracic echocardiography were 0.96 and 0.98 in the pre- and postoperative measurements, respectively. In Bland-Altman analysis, the bias (standard deviation [SD]), 95% limits of agreement, and percentage error were 0.03 (0.28), -0.53 to 0.60, and 18% in the preoperative measurement, and -0.04 (0.19), -0.42 to 0.35, and 15% in the postoperative measurement, respectively. The polar plot showed that the cardiac output changes were well tracked, with an angular bias (SD) of 2.9° (6.0°) and radial 95% limits of agreement ranging from -9.2° to 14.9°. Cardiac output measurement by esCCO with modified coefficients for pediatric patients showed high accuracy and tracking ability compared with cardiac output measurement by transthoracic echocardiography. This noninvasive cardiac output measurement could benefit perioperative hemodynamic monitoring in children.

The role of point-of-care ultrasound to assess fluid responsiveness and fluid tolerance in the intensive care unit

Fluid accumulation is epidemiologically associated with adverse outcomes in various clinical contexts. Assessing fluid responsiveness identifies conditions where intravenous fluids can increase cardiac output, improve organ blood supply during hypoperfusion and prevent the administration of ineffective fluids with deleterious effects. Point-of-care ultrasound (POCUS) enables fluid administration guided by fluid responsiveness, serving as one of the few non-invasive technological aids widely accessible both within and outside the intensive care unit. In this review, we focus on how POCUS can complement the evaluation of fluid responsiveness and fluid tolerance. The topics include a review of POCUS techniques to estimate the change in cardiac output following preload modifying manoeuvers, evaluation of thoracic fluid tolerance through lung ultrasound, and evaluation of systemic fluid tolerance through venous Doppler and the venous excess ultrasound (VExUS) assessment.

Long-Term Continuous Terlipressin Infusion Improves Cardiac Reserve in Patients With Decompensated Cirrhosis

Cardiac dysfunction is a key factor in the pathogenesis of hepatorenal syndrome, for which terlipressin is the recommended first-line treatment. This study investigates whether long-term terlipressin can ameliorate the subclinical cardiac dysfunction observed in decompensated cirrhosis. Twenty-two patients with decompensated cirrhosis and ascites enrolled in a prospective study of home continuous terlipressin infusion were included. Cardiac function was assessed using dobutamine stress echocardiogram before and after 12 weeks of terlipressin. The primary outcome was the impact of terlipressin on cardiac reserve, the change in cardiac output (CO) in response to stress. The median age was 61 years (interquartile range, 56-64 years), the median Model for End-Stage Liver Disease score was 15 (interquartile range, 12.3-17.0), and 72.7% were male. The increase in CO in response to low-dose dobutamine was significantly higher following terlipressin (↑4.0 L/min [↑57.8%]) as compared with baseline (↑1.8 L/min [21.3%]) (P= .0001). The proportion of patients with impaired cardiac reserve (defined by ΔCO <25% after low-dose dobutamine) reduced from 81.8% at baseline to 40.9% after terlipressin, (P= .02), driven primarily by improvement in inotropic function. Resting CO decreased significantly after terlipressin from 8.9 ± 2.2 L/min to 7.2 ± 1.8 L/min (normal range 5-6 L/min) (P < .001), due to a decrease in stroke volume from 108 to 86 mL/beat (P= .006). Long-term continuous terlipressin infusion resulted in a significant increase in cardiac reserve and attenuation of the hyperdynamic state usually observed in decompensated cirrhosis. These data provide important mechanistic insight into the pathogenesis and reversibility of cardiac dysfunction in cirrhosis. Future studies are required to evaluate whether long-term terlipressin can prevent hepatic decompensating events such as hepatorenal syndrome in high-risk individuals. Australian New Zealand Clinical Trials Registry, Number: ACTRN12619000891123.

Incidence and associated factors for hypotension during continuous renal replacement therapy in critically ill patients.

This work aimed to analyse retrospective data on hypotension incidence and associated factors among patients requiring continuous renal replacement therapy. The incidence and risk factors of continuous renal replacement therapy-related hypotension have not been adequately explored. The study was designed as a retrospective analysis. Patients who required continuous renal replacement therapy in the ICU between January 2017 and June 2021 were reviewed. The multivariate logistic regression model was used to determine the associated factors of hypotension. Hypotension occurred in 242 out of 885 circuits (27.3%) among 140 patients. The logistic regression analysis identified seven factors associated with the occurrence of hypotension during CRRT: serum albumin (OR = 0.969, 95%CI: 0.934-0.999), serum calcium (OR = 0.514, 95%CI: 0.345-0.905), CO2CP (OR = 0.933, 95%CI: 0.897-0.971), use of vasopressors (OR = 5.731, 95%CI: 4.023-8.165), hypotension before CRRT initiation (OR = 2.779, 95%CI:1.238-6.242), age (OR = 1.016, 95%CI: 1.005-1.027), and fluid removal rate (OR = 1.002, 95%CI: 1.001-1.003). Hypotension frequently occurs in patients receiving continuous renal replacement therapy, especially in the early stages. Multiple factors can be associated with cardiac output or peripheral resistance changes, including excessive ultrafiltration, vasopressors, serum albumin and serum calcium levels, and carbon dioxide combining power.

Preconception Physical Exercise Is Associated with Phenotype-Specific Cardiovascular Alterations in Women at Risk for Gestational Hypertensive Disorders.

Background/Objectives: Gestational hypertensive disorders (GHD) pose significant maternal and fetal health risks during pregnancy. Preconception physical exercise has been associated with a lower incidence of GHD, but insights into the cardiovascular mechanisms remain limited. This study aimed to evaluate the effect of preconception physical exercise on the complete cardiovascular functions of women at risk for GHD in a subsequent pregnancy. Methods: A non-invasive hemodynamics assessment of arteries, veins, and the heart was performed on 40 non-pregnant women at risk for developing GHD in a subsequent pregnancy. Measurements of an electrocardiogram Doppler ultrasound, impedance cardiography and bio-impedance spectrum analysis were taken before and after they engaged in physical exercise (30-50 min, 3×/week, 4-6 months). Results: After a mean physical exercise period of 29.80 weeks, the total peripheral resistance (TPR), diastolic blood pressure and mean arterial pressure decreased in the total study population, without changing cardiac output (CO). However, in 42% (9/21) of women categorized with high or low baseline CO (>P75 or <P25 resp.), a shift in CO was observed towards the normal reference interquartile range (P25-P75). This was associated with improved hepatic venous and central arterial hemodynamic functions. Similar changes in TPR occurred in 38% (11/29) of women classified as having low or high baseline TPR. Conclusions: As in pregnancy, output- or resistance-dominant cardiovascular profiles already exist prior to conception. This study illustrates that preconception physical exercise shifts high or low CO and/or TPR towards the normal midrange, allowing women at risk for GHD to start a subsequent pregnancy with a more gestation-adaptable cardiovascular system.

Evaluation of Electrical Cardiometry to Assess Fluid Responsiveness in Patients with Acute Circulatory Failure: A Comparative Study with Transthoracic Echocardiography.

Acute circulatory failure is commonly encountered in critically ill patients, that requires fluid administration as the first line of treatment. However, only 50% of patients are fluid-responsive. Identification of fluid responders is essential to avoid the harmful effects of overzealous fluid therapy. Electrical cardiometry (EC) is a non-invasive bedside tool and has proven to be as good as transthoracic echocardiography (TTE) to track changes in cardiac output. We aimed to look for an agreement between EC and TTE for tracking changes in cardiac output in adult patients with acute circulatory failure before and after the passive leg-raising maneuver. Prospective comparative study, conducted at a Tertiary Care Teaching Hospital. We recruited 125 patients with acute circulatory failure and found 42.4% (53 out of 125) to be fluid-responsive. The Bland-Altman plot analysis showed a mean difference of 2.08 L/min between EC and TTE, with a precision of 3.8 L/min. The limits of agreement (defined as bias ± 1.96SD), were -1.7 L/min and 5.8 L/min, respectively. The percentage of error between EC and TTE was 56% with acceptable limits of 30%. The percentage error beyond the acceptable limit suggests the non-interchangeability of the two techniques. More studies with larger sample sizes are required to establish the interchangeability of EC with TTE for tracking changes in cardiac output in critically ill patients with acute circulatory failure. Sharma S, Ramachandran R, Rewari V, Trikha A. Evaluation of Electrical Cardiometry to Assess Fluid Responsiveness in Patients with Acute Circulatory Failure: A Comparative Study with Transthoracic Echocardiography. Indian J Crit Care Med 2024;28(7):650-656.

Norepinephrine or phenylephrine for the prevention of post-spinal hypotension after caesarean section: A double-blinded, randomized, controlled study of fetal heart rate and fetal cardiac output

Study objectiveSpinal anesthesia often causes hypotension, with consequent risk to the fetus. The use of vasopressor agents has been highly recommended for the prevention of spinal anesthesia-induced hypotension during caesarean delivery. Many studies have shown that norepinephrine can provide more stable maternal hemodynamics than phenylephrine. We therefore tested the hypothesis that norepinephrine preserves fetal circulation better than phenylephrine when used to treat maternal hypotension consequent to spinal anesthesia. DesignProspective, randomized, double-blinded study. SettingOperating room. PatientsWe recruited 223 parturients with uncomplicated singleton pregnancies who were scheduled for elective caesarean section under combined spinal-epidural anesthesia. InterventionsThe patients received prophylactic intravenous infusion of either 0.08 μg/kg/min norepinephrine or 0.5 μg/kg/min phenylephrine for prevention of spinal anesthesia-induced hypotension. MeasurementsChanges in fetal heart rate and fetal cardiac output before and after spinal anesthesia were measured using noninvasive Doppler ultrasound. Main results90 subjects who received norepinephrine infusion and 93 subjects who received phenylephrine infusion were ultimately analyzed in the present study. The effects of norepinephrine and phenylephrine on the change of fetal heart rate and fetal cardiac output at 3 and 6 min after spinal block were similar. Although there was a statistically significant decrease in fetal cardiac output at 6 min after subarachnoid block initiation in both the norepinephrine group (mean difference 0.02 L/min; 95% CI, 0–0.04 L/min; P = 0.03) and the phenylephrine group (mean difference 0.02 L/min; 95% CI, 0–0.04 L/min; P = 0.02), it remained within the normal range. ConclusionsProphylactic infusion of comparable doses of phenylephrine or norepinephrine has similar effects on fetal heart rate and cardiac output changes after spinal anesthesia. Neither phenylephrine nor norepinephrine has meaningful detrimental effects on fetal circulation or neonatal outcomes.

#2570 Non-invasive blood pressure monitoring in dialysis patients using pulse wave velocity

Abstract Background and Aims Dialysis patients are at high risk of circulatory dysregulation and hypotension during treatment. Intradialytic hypotension (IDH) is a potentially life-threatening complication. The main causes are high ultrafiltration volumes and high ultrafiltration rates when patients tend to gain a lot of weight between dialysis treatments. A lack of patient compliance with regard to drinking volumes and a lack of residual diuresis are risk factors for this. Close circulatory monitoring and therapy settings to avoid absolute or relatively high UF rates to prevent IDH are frequently used. These are primarily the frequent non-invasive measurement of blood pressure using cuffs, the measurement of relative blood volume and the adjustment of ultrafiltration rates to these values. Prophylactically, the dialysis time can be extended, ultrafiltration profiles or ultrafiltration breaks can be planned, the dialysate temperature can be lowered and the composition of the dialysate can be adjusted. Despite all attempts, however, the incidence of IDH in everyday clinical practice is too high. The non-invasive measurements with cuffs are not carried out frequently enough, the measurement of the relative blood volume only covers a partial range, sudden changes in vascular tension or cardiac output are not recorded. Method The pulse wave velocity (PWV) is a well-known parameter for describing the propagation of the pressure wave after ejection of the heart beat volume in the arteries. The PWV is dependent on blood pressure, vessel wall tension and cardiac output. Changes in blood pressure can therefore be recognised by measuring the PWV. With the help of a measuring device (PESAS) for the ECG signal and peripheral pulse plethysmography, PWV can be measured non-invasively, continuously, for every heartbeat and, above all, hardly noticed by the patient. The PESAS allows the time-synchronised measurement of ECG and peripheral plethysmography curves and thus the determination of PWV. It is an experimental device. We would like to present a study showing the use of a measuring device (PESAS) in 15 prevalent dialysis patients for the detection of IDH. All study participants were examined during 3 dialysis treatments. Results The measurement of PWV in chronic dialysis patients during treatment is technically feasible. The measurement is tolerated by the patients. Changes in PWV could be detected in the patients during the course of dialysis; these were also dependent on the ultrafiltration rates. Individual patient reactions to volume withdrawal varied, with both increases and decreases in PWV being demonstrated. An acute change in PWV was usually associated with a drop in blood pressure. Continuous measurement allowed IDH events to be detected earlier than intermittent blood pressure measurement with cuffs. Sudden drops in blood pressure could be detected better and earlier with the PESAS system than by measuring the relative blood volume. Conclusion The PESAS system is suitable for monitoring dialysis patients to prevent IDH. Further adjustments and optimisation of the evaluation algorithms are necessary.

Effects of medical therapy and age on cardiac output changes following balloon pulmonary angioplasty: Implications for combination therapy in chronic thromboembolic pulmonary hypertension

BACKGROUNDSome patients with chronic thromboembolic pulmonary hypertension (CTEPH) exhibit exercise intolerance due to reduced cardiac output (CO) even after successful balloon pulmonary angioplasty (BPA). Medical therapy is a potential option for such cases; however, it is unclear which patients necessitate it even after BPA. METHODSThis study included 286 patients with CTEPH who underwent BPA and right heart catheterization one year after the final BPA and classified them into No-medication and Withdrawal groups. The No-medication group comprised patients without pulmonary hypertension (PH) medications before and after BPA, while the Withdrawal group included patients who received PH medications before BPA and discontinued them after BPA. We assessed differences in the changes in CO after BPA from baseline (ΔCO) between the two groups. Additionally, we evaluated the ΔCO among different age categories within each group: younger (< 60 years), middle-aged (60 to 70 years), and older-adults (≥ 70 years). RESULTSAfter adjusting baseline covariates, overall ΔCO did not differ significantly. However, ΔCO was significantly increased in No-medication group but decreased in Withdrawal group (0.32 and −0.33, difference in ΔCO: −0.65, 95% confidence intervals: −0.90 to −0.40). A significantly positive effect on ΔCO was observed only in younger individuals, with a significant interaction between age and ΔCO in both groups. CONCLUSIONSIncreasing CO with BPA alone may be challenging with age in patients with CTEPH. Given that discontinuation of PH medication after BPA decreased CO more than the effect of BPA, medical therapy might be necessary even after successful BPA.

Cardiac workload study in patients with hypertrophic cardiomyopathy

The relevance of studying the heart load is determined by the need to assess its reserves at different degrees of heart failure for further selection of treatment tactics. The aim of the work is to evaluate the influence of pressure and cardiac output changes on the left and right ventricular workload in patients with hypertrophic obstructive cardiomyopathy. The haemodynamic data of 69 patients divided into two subgroups according to the value of cardiac index greater and less than the mean value were considered. It was found that the change in the left ventricular power of the heart of patients with hypertrophic obstructive cardiomyopathy is determined by the change in both cardiac index and blood pressure. In better-off patients with high cardiac index, the effect of blood pressure is higher and cardiac output is lower. In severe patients with a low cardiac index, the influence of blood pressure is reduced and cardiac index is increased. The formation of right ventricular power, both in patients with high cardiac index and low, is not affected by changes in cardiac output. Changes in the right ventricular power index are determined by variations in pulmonary artery pressure to a greater extent in well patients and to a lesser extent in severe patients. Since there are 23.1% variations in cardiac index and 60% variations in pulmonary arterial pressure, it is assumed that there is a regulatory mechanism that changes cardiac output opposite to pulmonary artery pressure fluctuations. Comparison of left and right ventricular power indices with the data given in the literature showed that both for all examined patients with hypertrophic obstructive cardiomyopathy and divided into groups, the average values of left and right ventricular power indices correspond to the range of power fluctuations in healthy people at rest. The range of left ventricular power index variation by 3.5 times, and right ventricular power index variation by 10 times in patients with hypertrophic obstructive cardiomyopathy is determined by multifunctional relationships of cardiovascular system function indices (pressures and cardiac output), which determines the necessity of personalised therapy selection, taking into account the mechanisms of their formation. The results obtained during the study of the effect of changes in pressure and cardiac index on the power developed by the left and right parts of the heart must be taken into account when choosing therapy in patients with hypertrophic obstructive cardiomyopathy. Practical significance. The results will be used in the choice of treatment in order to optimize the load on the heart in patients with hypertrophic obstructive cardiomyopathy.

Cardiomyocyte Ketone Metabolism Regulates Myocardial Hyperemia

Myocardial perfusion is inextricably coupled to metabolism, with increases in physiologic cardiac demand promoting coronary vasodilation. Despite its wide acceptance, the hypothesis that cardiomyocyte metabolism autoregulates myocardial perfusion lacks mechanistic detail; however, clinical and preclinical studies suggest a signaling role for intermediary metabolites in the vasodilatory response. In particular, the ketone body precursor, β-hydroxybutyrate (3-OHB), enhances myocardial blood flow in humans, but the mechanism by which it does so remains unclear. Here, we determined the extent to which 3-OHB influences myocardial hyperemia in mice. Intravenous 3-OHB infusion (0.5 g/kg) in adult mice (12–24 wks) raised circulating 3-OHB levels (0.5 ± 0.1 to 5.1 ± 0.6 mM; p=0.005) and increased myocardial perfusion (18.6 ± 4.4 to 50.9 ± 10.4 mL/min/g; p=0.024), as measured by myocardial contrast echocardiography. Enhanced perfusion induced by 3-OHB occurred in the absence of changes in cardiac output or systolic performance. Next, to determine if 3-OHB directly dilates the coronary vasculature, we exposed pressurized (80 mmHg), small-diameter (100–260 μm) coronary arteries from mice (C57/Bl6J and 6N) to 3-OHB (0.1–5 mM) but found no significant changes in diameter. Based on these results, we tested whether cardiomyocyte metabolism of 3-OHB is required for the vasodilatory response. We deleted β-hydroxybutyrate dehydrogenase (BDH1) selectively in cardiomyocytes using Bdh1fl/fl mice crossed with tamoxifen-inducible Cre recombinase mice (csBDH1−/−). Although 3-OHB robustly enhanced myocardial perfusion (6.9 ± 1.4 to 21.3 ± 5.6 mL/min/g; p=0.031) at sustained cardiac workloads and peripheral vascular resistance in Cre-negative littermate (control) mice, csBDH1−/− mice completely lacked the 3-OHB-induced hyperemic response (8.0 ± 2.5 to 6.3 ± 2.8 mL/min/g; p&gt;0.999). Together, these data indicate that 3-OHB evokes workload-independent enhancement of myocardial perfusion through a mechanism that requires cardiomyocyte metabolism of 3-OHB. Our results support the general concept that acute changes in metabolic substrate availability may influence oxygen delivery to cardiomyocytes via a cardiomyocyte-vascular signaling nexus. R01HL163818, R01HL142710, R01HL163003, P30GM127607, P30GM127607-05S1, Jewish Heritage Fund for Excellence (JHFE), S10OD025178. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Microtubules distinctly contribute to the performance of the healthy and pressure-overloaded RV

Introduction: Microtubules (MT) are a key contributor to cardiomyocyte contractility and mechanics. Recently, our group reported that acute depolymerization of MT reduces viscosity and elasticity and alters anisotropy of healthy and pressure-overloaded right ventricular (RV) tissues. While RV free wall viscosity and elasticity are distinctly upregulated with chronic pressure overload, how organ function is affected by viscoelastic contribution of the MT remains unknown. Our aim was to investigate the role of MT polymerization in RV function from its effect on RV tissue viscoelasticity. We hypothesized that the MT differentially contributes to healthy and pressure-overloaded RV function. Methods: All procedures and methods were approved by Colorado State University IACUC. Pulmonary hypertension (PH) was induced in 6-week-old male rats via 3-week monocrotaline treatment. Healthy age- and sex-matched rats served as control. Pressure-volume (PV) relationships were obtained by RV catheterization before and after intramyocardial injections of 0.3mM colchicine (COL) to acutely depolymerize the MT network and reduce tissue viscoelasticity. Functional impacts were evaluated by monitoring changes in RV end-systolic pressure (ESP), cardiac output (CO), stroke volume (SV), ejection fraction (EF), dP/dt max and min, cardiac effciency (CE), and the end-systolic pressure-volume relation (ESPVR). Results: As expected, monocrotaline treatment induced marked PH and RV contractile dysfunction, indicated by a significant elevation of RV ESP with reduced CO and ESPVR. In the healthy RV, COL treatment led to marked reductions in all functional parameters, indicating that the MT network is critical to maintain RV performance and contractile function in the healthy heart. In the pressure-overloaded RV, COL treatment similarly reduced SV, CO, EF, and dP/dt max and min, but increased CE and ESPVR, indicating that MT depolymerization improved mechanical effciency and contractility. To rule out effects caused by bolus injections alone, we administered a similar quantity of saline and observed no effects on the PV parameters in healthy RV. Discussion: Our study is the first to investigate the acute effect of MT depolymerization on RV function in healthy and diseased states. We found distinct contributions of MT to the contractile function and mechanical effciency of healthy and pressure-overloaded RVs. These findings reveal a critical influence of tissue viscoelasticity on RV physiology and dysfunction, emphasizing the importance of considering myocardial viscoelastic behavior in future studies investigating cardiac remodeling and heart failure pathophysiology. This work is partially supported by the National Science Foundation (NSF) grant 2244994. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.