Impact of hyperaemic stenosis resistance on long-term outcomes of stable angina in the ILIAS Registry.

BACKGROUND: The hyperaemic stenosis resistance (HSR) index was introduced to provide a more comprehensive indicator of the haemodynamic severity of a coronary lesion. HSR combines both the pressure drop across a lesion and the flow through it. As such, HSR overcomes the limitations of the more traditional fractional flow reserve (FFR) or coronary flow reserve (CFR) indices. AIMS: We aimed to identify the diagnostic and prognostic value of HSR and evaluate the clinical implications. METHODS: Patients with chronic coronary syndromes (CCS) and obstructive coronary artery disease were selected from the multicentre ILIAS Registry. For this study, only patients with combined Doppler flow and pressure measurements were included. RESULTS: A total of 853 patients with 1,107 vessels were included. HSR more accurately identified the presence of inducible ischaemia compared to FFR and CFR (area under the curve 0.71 vs 0.66 and 0.62, respectively; p<0.005 for both). An abnormal HSR measurement was an independent and important predictor of target vessel failure at 5-year follow-up (hazard ratio 3.80, 95% confidence interval: 2.12-6.73; p<0.005). In vessels deferred from revascularisation, HSR seems to identify more accurately those vessels that may benefit from revascularisation rather than FFR and/or CFR. CONCLUSIONS: The present study affirms the theoretical advantages of the HSR index for the detection of ischaemia-Âinducing coronary lesions in a large CCS population. (Inclusive Invasive Physiological Assessment in Angina Syndromes Registry [ILIAS Registry], ClinicalTrials.gov: NCT04485234).

Effects of age on microvascular function in patients with normal coronary arteries.

BACKGROUND: It has been suggested that coronary microvascular function decreases with age, irrespective of the presence of epicardial atherosclerosis. AIMS: Our aim is to quantitatively investigate the effects of age on microvascular function in patients with normal coronary arteries. METHODS: In 314 patients with angina with no obstructive coronary artery disease (ANOCA), microcirculatory function was tested using the continuous thermodilution method. In 305 patients, the association between age and both resting and hyperaemic myocardial blood flow (Q), microvascular resistance (Rµ), absolute coronary flow reserve (CFR) and microvascular resistance reserve (MRR) was assessed. In addition, patients were divided into 3 groups to test for differences based on age quartiles (≤52 years [24.9%], 53-64 years [49.2%], ≥65 years [25.9%]). RESULTS: The mean age was 59±9 years with a range from 22 to 79 years. The mean resting Q (Qrest) was not different in the 3 age groups (88±34 mL/min, 82±29 mL/min, and 86±38 mL/min, R2=0.001; p=0.62). A trend towards a decreasing mean hyperaemic Q (Qmax) was observed with increasing age (223±79 mL/min, 209±84 mL/min, 200±80 mL/min, R2=0.010; p=0.083). The mean resting Rµ (Rµ,rest) were 1,204±460 Wood units (WU), 1,260±411 WU, and 1,289±455 WU (p=0.23). The mean hyperaemic Rµ (Rµ,hyp) increased significantly with advancing age (429±149 WU, 464±164 WU, 503±162 WU, R2=0.026; p=0.005). Consequently, MRR decreased with age (3.2±1.2, 3.1±1.0, 2.9±0.9; p=0.038). This trend was present in both the patients with (n=121) and without (n=184) coronary microvascular dysfunction (CMD). CONCLUSIONS: There is an age-dependent physiological increase in minimal microvascular resistance and decrease in microvascular function, which is represented by a decreased MRR and is independent of atherosclerosis. The age-dependent decrease in MRR was present in both patients with and without CMD and was most evident in patients with smooth coronary arteries.

A multi-objective optimisation approach for the linear modelling of cerebral autoregulation system.

OBJECTIVE: Dynamic cerebral autoregulation (dCA) has been addressed through different approaches for discriminating between normal and impaired conditions based on spontaneous fluctuations in arterial blood pressure (ABP) and cerebral blood flow (CF). This work presents a novel multi-objective optimisation (MO) approach for finding good configurations of a cerebrovascular resistance-compliance model. METHODS: Data from twenty-nine subjects under normo and hypercapnic (5% CO2 in air) conditions was used. Cerebrovascular resistance and vessel compliance models with ABP as input and CF velocity as output were fitted using a MO approach, considering fitting Pearson's correlation and error. RESULTS: MO approach finds better model configurations than the single-objective (SO) approach, especially for hypercapnic conditions. In addition, the Pareto-optimal front from the multi-objective approach enables new information on dCA, reflecting a higher contribution of myogenic mechanism for explaining dCA impairment.

[Changes of hemodynamic parameters in normal pregnant women and their relationship with maternal basic characteristics].

Objective: To investigate the variation of reference ranges of hemodynamic parameters in normal pregnancy and their relation to maternal basic characteristics. Methods: A total of 598 healthy pregnant women who underwent regular prenatal examination at the Third Affiliated Hospital of Guangzhou Medical University from January to December 2023 were prospectively enrolled, and noninvasive hemodynamic monitors were used to detect changes in hemodynamic parameters of the pregnant women with the week of gestation, including cardiac output (CO), stroke volume (SV), thoracic fluid content (TFC), systemic vascular resistance (SVR), mean arterial pressure (MAP), and heart rate (HR). Relationships between hemodynamic parameters and maternal basic characteristics, including age, height, and weight, were analyzed using restricted cubic spline. Results: (1) CO (r=0.155, P<0.001), TFC (r=0.338, P<0.001), MAP (r=0.204, P<0.001), and HR (r=0.352, P<0.001) were positively correlated with the week of gestation, and SV was negatively correlated with the week of gestation (r=-0.158, P<0.001). There was no significant correlation between SVR and gestational age (r=-0.051, P=0.258). (2) CO exhibited a positive correlation with maternal height and weight (all P<0.001). The taller and heavier of pregnant women, the higher their CO. A linear relationship was observed between maternal weight and SV, MAP and HR (all P<0.01). As maternal weight increased, SV, MAP and HR showed an upward trend. Furthermore, there was an inverse association between maternal age and SVR (P<0.001). (3) There was a significant nonlinear association observed between TFC and body mass index during pregnancy (P<0.05). Additionally, a nonlinear relationship was found between SVR and MAP in relation to maternal age (all P<0.05). Notably, when the age exceeded 31 years old, there was an evident upward trend observed in both SVR and MAP. Conclusions: The hemodynamic parameters of normal pregnant women are influenced by their height, body weight, and age. It is advisable to maintain a reasonable weight during pregnancy and give birth at an appropriate age.

Immediate cardiopulmonary responses to consecutive pulmonary embolism: a randomized, controlled, experimental study.

BACKGROUND: Acute pulmonary embolism (PE) induces ventilation-perfusion mismatch and hypoxia and increases pulmonary pressure and right ventricular (RV) afterload, entailing potentially fatal RV failure within a short timeframe. Cardiopulmonary factors may respond differently to increased clot burden. We aimed to elucidate immediate cardiopulmonary responses during successive PE episodes in a porcine model. METHODS: This was a randomized, controlled, blinded study of repeated measurements. Twelve pigs were randomly assigned to receive sham procedures or consecutive PEs every 15 min until doubling of mean pulmonary pressure. Cardiopulmonary assessments were conducted at 1, 2, 5, and 13 min after each PE using pressure-volume loops, invasive pressures, and arterial and mixed venous blood gas analyses. ANOVA and mixed-model statistical analyses were applied. RESULTS: Pulmonary pressures increased after the initial PE administration (p < 0.0001), with a higher pulmonary pressure change compared to pressure change observed after the following PEs. Conversely, RV arterial elastance and pulmonary vascular resistance was not increased after the first PE, but after three PEs an increase was observed (p = 0.0103 and p = 0.0015, respectively). RV dilatation occurred following initial PEs, while RV ejection fraction declined after the third PE (p = 0.004). RV coupling exhibited a decreasing trend from the first PE (p = 0.095), despite increased mechanical work (p = 0.003). Ventilatory variables displayed more incremental changes with successive PEs. CONCLUSION: In an experimental model of consecutive PE, RV afterload elevation and dysfunction manifested after the third PE, in contrast to pulmonary pressure that increased after the first PE. Ventilatory variables exhibited a more direct association with clot burden.

Effect of systemic vascular resistance on the agreement between stroke volume by non-invasive pulse wave analysis and Doppler ultrasound in healthy volunteers.

BACKGROUND: Stroke volume can be estimated beat-to-beat and non-invasively by pulse wave analysis (PWA). However, its reliability has been questioned during marked alterations in systemic vascular resistance (SVR). We studied the effect of SVR on the agreement between stroke volume by PWA and Doppler ultrasound during reductions in stroke volume in healthy volunteers. METHODS: In a previous study we simultaneously measured stroke volume by PWA (SVPWA) and suprasternal Doppler ultrasound (SVUS). We exposed 16 healthy volunteers to lower body negative pressure (LBNP) to reduce stroke volume in combination with isometric hand grip to elevate SVR. LBNP was increased by 20 mmHg every 6 minutes from 0 to 80 mmHg, or until hemodynamic decompensation. The agreement between SVPWA and SVUS was examined using Bland-Altman analysis with mixed regression. Within-subject limits of agreement (LOA) was calculated from the residual standard deviation. SVRUS was calculated from SVUS. We allowed for a sloped bias line by introducing the mean of the methods and SVRUS as explanatory variables to examine whether the agreement was dependent on the magnitude of stroke volume and SVRUS. RESULTS: Bias ± limits of agreement (LOA) was 27.0 ± 30.1 mL. The within-subject LOA was ±11.1 mL. The within-subject percentage error was 14.6%. The difference between methods decreased with higher means of the methods (-0.15 mL/mL, confidence interval (CI): -0.19 to -0.11, P<0.001). The difference between methods increased with higher SVRUS (0.60 mL/mmHg × min × L-1, 95% CI: 0.48 to 0.72, P<0.001). CONCLUSION: PWA overestimated stroke volume compared to Doppler ultrasound during reductions in stroke volume and elevated SVR in healthy volunteers. The agreement between SVPWA and SVUS decreased during increases in SVR. This is relevant in settings where a high level of reliability is required.

A review regarding the article 'Effectiveness of mechanical circulatory support devices in reversing pulmonary hypertension among heart transplant candidates: A systematic review.'

Pulmonary hypertension (PH) with high pulmonary vascular resistance (PVR) is a very often diagnosed contraindication for orthotopic heart transplantation (OHT). It is a direct consequence of left ventricle failure characterized by high diastolic pressure obstructing the collection of blood from the pulmonary vessels. The occurrence of this situation grows with the increasing time of waiting for OHT, and with the progression of heart failure. Mechanical circulatory support (MCS) devices, particularly left ventricular assist devices (LVADs), have emerged as pivotal interventions for patients with fixed PH, offering a potential bridge to transplantation. The pathophysiological impact of PH in heart transplant candidates is profound, as it is associated with increased perioperative risk and heightened mortality post-transplantation. The selection of heart transplant candidates thus mandates a careful evaluation of PH, with an emphasis on distinguishing between reversible and fixed forms of the condition. Reversible PH can often be managed with medical therapies; however, fixed PH presents a more daunting challenge, necessitating more aggressive interventions like MCS. Patients are supported with LVADs until evidence of pulmonary afterload reversal is evident and then can be considered for heart transplantation. However, in those who are non-responders or have complications while being supported, their option for transplant is revoked. Despite these advancements, the heterogeneity of MCS devices and their mechanisms of action necessitates a nuanced understanding of their efficacy.

High output cardiac state: evaluating the incidence, plausible etiologies and outcomes.

INTRODUCTION: The high output cardiac state (HOCS) [cardiac index (CI) >4 L/min/m2 ], primarily driven by abnormally low systemic vascular resistance (SVR), is a relatively under-recognized condition. Although, majority of these patients meet criteria for heart failure (HF), their treatment should be aimed at the primary pathology, as the majority of guideline directed HF therapies can reduce SVR further. OBJECTIVES: To characterize patients with HOCS and provide valuable insight into the condition. METHODS: Patients investigated by right heart catheterization (RHC) at the St. Boniface Hospital, Winnipeg, Canada between January 2009 and November 2021 were reviewed. Two groups of patients were included: 1) HOCS [CI >4 L/min/m2], and 2) pre-HOCS [CI between 3.8-4.0 L/min/m2]. Their medical records were reviewed to identify plausible etiologies, relevant investigations, and outcomes. RESULTS: 177/2950 (6 %) patients met criteria for inclusion: 144/177 (81 %) with HOCS [mean age 51 years (range 19 - 82); 67/144 (47 %) female] and 33/177 (19 %) with pre-HOCS [mean age 55 years (range 30 - 83); 6/33 (18 %) female]. The most common plausible etiologies for the HOCS included anemia (36 %), obesity (34 %), cirrhosis (17 %), and lung disease (32 %). Trans-thoracic echocardiography and magnetic resonance imaging findings were non-specific and predominantly described preserved left ventricular ejection fraction, and pulmonary hypertension. The population experienced high rates of hospitalization, and significantly high mortality [36/144 (25 %) of HOCS at a median follow-up of 31.5 months, and 13/33 (39 %) of pre-HOCS at a median follow-up of 17 months]. CONCLUSIONS: HOCS is not an uncommon condition and is associated with high mortality. Current HF guideline should incorporate such evaluation into the diagnostic criteria.

Pathophysiology and therapeutic options for cirrhotic portal hypertension.

Portal hypertension represents the primary non-neoplastic complication of liver cirrhosis and has life-threatening consequences, such as oesophageal variceal bleeding, ascites, and hepatic encephalopathy. Portal hypertension occurs due to increased resistance of the cirrhotic liver vasculature to portal blood flow and is further aggravated by the hyperdynamic circulatory syndrome. Existing knowledge indicates that the profibrogenic phenotype acquired by sinusoidal cells is the initial factor leading to increased hepatic vascular tone and fibrosis, which cause increased vascular resistance and portal hypertension. Data also suggest that the phenotype of hepatic cells could be further impaired due to the altered mechanical properties of the cirrhotic liver itself, creating a deleterious cycle that worsens portal hypertension in the advanced stages of liver disease. In this Review, we discuss recent discoveries in the pathophysiology and treatment of cirrhotic portal hypertension, a condition with few pharmacological treatment options.

Coronary Microvascular Function Following Severe Preeclampsia.

BACKGROUND: Preeclampsia is a pregnancy-specific hypertensive disorder associated with an imbalance in circulating proangiogenic and antiangiogenic proteins. Preclinical evidence implicates microvascular dysfunction as a potential mediator of preeclampsia-associated cardiovascular risk. METHODS: Women with singleton pregnancies complicated by severe antepartum-onset preeclampsia and a comparator group with normotensive deliveries underwent cardiac positron emission tomography within 4 weeks of delivery. A control group of premenopausal, nonpostpartum women was also included. Myocardial flow reserve, myocardial blood flow, and coronary vascular resistance were compared across groups. sFlt-1 (soluble fms-like tyrosine kinase receptor-1) and PlGF (placental growth factor) were measured at imaging. RESULTS: The primary cohort included 19 women with severe preeclampsia (imaged at a mean of 15.3 days postpartum), 5 with normotensive pregnancy (mean, 14.4 days postpartum), and 13 nonpostpartum female controls. Preeclampsia was associated with lower myocardial flow reserve (ß, -0.67 [95% CI, -1.21 to -0.13]; P=0.016), lower stress myocardial blood flow (ß, -0.68 [95% CI, -1.07 to -0.29] mL/min per g; P=0.001), and higher stress coronary vascular resistance (ß, +12.4 [95% CI, 6.0 to 18.7] mm Hg/mL per min/g; P=0.001) versus nonpostpartum controls. Myocardial flow reserve and coronary vascular resistance after normotensive pregnancy were intermediate between preeclamptic and nonpostpartum groups. Following preeclampsia, myocardial flow reserve was positively associated with time following delivery (P=0.008). The sFlt-1/PlGF ratio strongly correlated with rest myocardial blood flow (r=0.71; P<0.001), independent of hemodynamics. CONCLUSIONS: In this exploratory cross-sectional study, we observed reduced coronary microvascular function in the early postpartum period following preeclampsia, suggesting that systemic microvascular dysfunction in preeclampsia involves coronary microcirculation. Further research is needed to establish interventions to mitigate the risk of preeclampsia-associated cardiovascular disease.

Effectiveness of mechanical circulatory support devices in reversing pulmonary hypertension among heart transplant candidates: A systematic review.

BACKGROUND: Pulmonary hypertension (PH) poses a significant challenge in the selection of candidates for heart transplantation, impacting their eligibility and post-transplant outcomes. Mechanical circulatory support (MCS) devices, particularly left ventricular assist devices (LVADs), have emerged as a therapeutic option to manage PH in this patient population. This systematic review aims to evaluate the effectiveness of MCS devices in reversing fixed pulmonary hypertension in heart transplant candidates. METHODS: A comprehensive literature search was conducted across multiple databases, including PubMed, Scopus, and Web of Science, to identify studies that evaluated the effectiveness of MCS devices in reversing fixed pulmonary hypertension in heart transplant candidates. Data on pulmonary vascular resistance, PH reversal, heart transplant eligibility, and post-transplant outcomes were extracted and synthesized. RESULTS: The review included studies that demonstrated the potential of MCS devices, especially LVADs, to significantly reduce pulmonary vascular resistance and reverse fixed pulmonary hypertension in heart transplant candidates. These findings suggest that MCS devices can improve transplant eligibility and may positively impact post-transplant survival rates. However, the literature also indicates a need for further comparative studies to optimize MCS device selection and treatment protocols. CONCLUSION: MCS devices, particularly LVADs, play a crucial role in the management of fixed pulmonary hypertension in heart transplant candidates, improving their eligibility for transplantation and potentially enhancing post-transplant outcomes. Future research should focus on comparative effectiveness studies to guide clinical decision-making and optimize patient care in this challenging clinical scenario.

MFAP4-Deficiency Aggravates Age-Induced Changes in Resistance Artery Structure, While Ameliorating Hypertension.

BACKGROUND: Abnormalities of resistance arteries may play essential roles in the pathophysiology of aging and hypertension. Deficiency of the vascular extracellular matrix protein MFAP4 (microfibrillar-associated protein 4) has previously been observed as protective against aberrant arterial remodeling. We hypothesized that MFAP4-deficiency would reduce age- and hypertension-dependent arterial changes in extracellular matrix composition and stiffening. METHODS: Mesenteric arteries were isolated from old (20-23 months) littermate Mfap4+/+ and Mfap4-/- mice, and 2-photon excitation microscopy imaging was used to quantify elastin and collagen volumes and dimensions in the vascular wall. Ten-week-old littermate Mfap4+/+ and Mfap4-/- mice were subjected to 20 days of continuous Ang II (angiotensin II) infusion and hypertension was monitored using invasive blood pressure measurements. Arterial stiffness, responses to vascular constrictors, and myogenic tone were monitored using wire- or pressure-myography. Collagen contents were assessed by Western blotting. RESULTS: MFAP4-deficiency significantly increased collagen volume and elastin fragmentation in aged mesenteric arteries without affecting arterial stiffness. MFAP4-deficient mice exhibited reduced diastolic pressure in Ang II-induced hypertension. There was no significant effect of MFAP4-deficiency on mesenteric artery structural remodeling or myogenic tone, although collagen content in mesenteric arteries was tendentially increased in hypertensive Mfap4+/+ mice relative to Mfap4-/- mice. Increased efficacy of vasoconstrictors (phenylephrine, thromboxane) and reduced stiffness were observed in Ang II-treated Mfap4-/- mouse mesenteric arteries in ex vivo myography recordings. CONCLUSIONS: MFAP4-deficiency reduces the elastin/collagen ratio in the aging resistance artery without affecting arterial stiffness. In contrast, MFAP4-deficiency reduces the stiffness of resistance arteries and ameliorates Ang II-induced hypertension.

Angiographic Coronary Slow Flow Is Not a Valid Surrogate for Invasively Diagnosed Coronary Microvascular Dysfunction.

BACKGROUND: Ischemia with no obstructive coronary arteries is frequently caused by coronary microvascular dysfunction (CMD). Consensus diagnostic criteria for CMD include baseline angiographic slow flow by corrected TIMI (Thrombolysis In Myocardial Infarction) frame count (cTFC), but correlations between slow flow and CMD measured by invasive coronary function testing (CFT) are uncertain. OBJECTIVES: The aim of this study was to investigate relationships between cTFC and invasive CFT for CMD. METHODS: Adults with ischemia with no obstructive coronary arteries underwent invasive CFT with thermodilution-derived baseline coronary blood flow, coronary flow reserve (CFR), and index of microcirculatory resistance (IMR). CMD was defined as abnormal CFR (<2.5) and/or abnormal IMR (≥25). cTFC was measured from baseline angiography; slow flow was defined as cTFC >25. Correlations between cTFC and baseline coronary flow and between CFR and IMR and associations between slow flow and invasive measures of CMD were evaluated, adjusted for covariates. All patients provided consent. RESULTS: Among 508 adults, 49% had coronary slow flow. Patients with slow flow were more likely to have abnormal IMR (36% vs 26%; P = 0.019) but less likely to have abnormal CFR (28% vs 42%; P = 0.001), with no difference in CMD (46% vs 51%). cTFC was weakly correlated with baseline coronary blood flow (r = -0.35; 95% CI: -0.42 to -0.27), CFR (r = 0.20; 95% CI: 0.12 to 0.28), and IMR (r = 0.16; 95% CI: 0.07-0.24). In multivariable models, slow flow was associated with lower odds of abnormal CFR (adjusted OR: 0.53; 95% CI: 0.35 to 0.80). CONCLUSIONS: Coronary slow flow was weakly associated with results of invasive CFT and should not be used as a surrogate for the invasive diagnosis of CMD.

Hyperaemia during dynamic handgrip exercise is preserved in healthy young subjects after recovery from COVID-19.

We sought to investigate possible impaired hyperaemia during dynamic handgrip exercise (HGE) in young healthy individuals who had recovered from COVID-19. We tested the vascular function in individuals recovered from COVID-19 using a nitric oxide donor (i.e., sodium nitroprusside; SNP), which could revert a possible impaired endothelial function during HGE. Further, we tested whether individuals who recovered from COVID-19 would present exaggerated brachial vascular resistance under an adrenergic agonist (i.e., phenylephrine; PHE) stimuli during HGE. Participants were distributed into two groups: healthy controls (Control; men: n = 6, 30 ± 3 years, 26 ± 1 kg/m2; and women: n = 5, 25 ± 1 years, 25 ± 1 kg/m2) and subjects recovered from COVID-19 (post-COVID; men: n = 6, 29 ± 3 years, 25 ± 1 kg/m2; and women: n = 10, 32 ± 4 years, 22 ± 1 kg/m2). Participants in the post-COVID group tested positive (RT-PCR) 12-14 weeks before the protocol. Heart rate (HR), brachial blood pressure (BP), brachial blood flow (BBF) and vascular conductance (BVC) at rest were not different between groups. The HGE increased HR (Control: Δ9 ± 0.4 bpm; and post-COVID: Δ11 ± 0.4 bpm) and BP (Control: Δ6 ± 1 mmHg; and post-COVID: Δ12 ± 0.6 mmHg) in both groups. Likewise, BBF (Control: Δ632 ± 38 ml/min; and post-COVID: Δ620 ± 27 ml/min) and BVC (Control: Δ6.6 ± 0.4 ml/min/mmHg; and post-COVID: Δ6.1 ± 0.3 ml/min/mmHg) increased during HGE. SNP did not change HGE-induced hyperaemia but did decrease BP, which induced a reflex-related increase in HR. PHE infusion also did not change the HGE-induced hyperaemia but raised BP and reduced HR. In conclusion, exercise-induced hyperaemia is preserved in healthy young subjects 12-14 weeks after recovery from COVID-19 infection.

Innervation of the coronary arteries and its role in controlling microvascular resistance.

The coronary circulation plays a crucial role in balancing myocardial perfusion and oxygen demand to prevent myocardial ischemia. Extravascular compressive forces, coronary perfusion pressure, and microvascular resistance are involved to regulate coronary blood flow throughout the cardiac cycle. Autoregulation of the coronary blood flow through dynamic adjustment of microvascular resistance is maintained by complex interactions among mechanical, endothelial, metabolic, neural, and hormonal mechanisms. This review focuses on the neural mechanism. Anatomy and physiology of the coronary arterial innervation have been extensively investigated using animal models. However, findings in the animal heart have limited applicability to the human heart as cardiac innervation is generally highly variable among species. So far, limited data are available on the human coronary artery innervation, rendering multiple questions unresolved. Recently, the clinical entity of ischemia with non-obstructive coronary arteries has been proposed, characterized by microvascular dysfunction involving abnormal vasoconstriction and impaired vasodilation. Thus, measurement of microvascular resistance has become a standard diagnostic for patients without significant stenosis in the epicardial coronary arteries. Neural mechanism is likely to play a pivotal role, supported by the efficacy of cardiac sympathetic denervation to control symptoms in patients with angina. Therefore, understanding the coronary artery innervation and control of microvascular resistance of the human heart is increasingly important for cardiologists for diagnosis and to select appropriate therapeutic options. Advancement in this field can lead to innovations in diagnostic and therapeutic approaches for coronary artery diseases.

Measuring Absolute Coronary Flow and Microvascular Resistance by Thermodilution: JACC Review Topic of the Week.

Diagnosing coronary microvascular dysfunction remains challenging, primarily due to the lack of direct measurements of absolute coronary blood flow (Q) and microvascular resistance (Rµ). However, there has been recent progress with the development and validation of continuous intracoronary thermodilution, which offers a simplified and validated approach for clinical use. This technique enables direct quantification of Q and Rµ, leading to precise and accurate evaluation of the coronary microcirculation. To ensure consistent and reliable results, it is crucial to follow a standardized protocol when performing continuous intracoronary thermodilution measurements. This document aims to summarize the principles of thermodilution-derived absolute coronary flow measurements and propose a standardized method for conducting these assessments. The proposed standardization serves as a guide to ensure the best practice of the method, enhancing the clinical assessment of the coronary microcirculation.

Effects of School-Based High-Intensity Interval Training on Hemodynamic Parameters and Heart Rate Variability: A Randomized Controlled Trial.

ABSTRACT: Ketelhut, S, Ketelhut, K, Ketelhut, SR, and Ketelhut, RG. Effects of school-based high-intensity interval training on hemodynamic parameters and heart rate variability: A randomized controlled trial. J Strength Cond Res 38(6): 1033-1040, 2024-The purpose of this study was to assess the effects of a child-specific school-based high-intensity interval training (HIIT) implemented into physical education (PE) classes on various hemodynamic parameters and heart rate variability indices. Forty-six students (age 11 ± 1 year) were randomized into an intervention (INT n = 22) and a control group (CON n = 24). During a 12-week period, the INT and CON groups participated in regular PE twice weekly (45-90 minutes). The INT group received HIIT during the first 20 minutes of the 2 PE classes. Systolic and diastolic blood pressure, total peripheral resistance, aortic pulse wave velocity (aPWV), heart rate, SD of normal to normal heartbeat intervals, the root mean square of successive differences between normal heartbeats (RMSSD), the proportion of differences between adjacent normal to normal heartbeat intervals of more than 50 ms, low-frequency power, high-frequency power, and the LF/HF ratio were assessed before and after the experimental period. A p value ≤0.05 was considered statistically significant. Forty students (20 INT; 20 CON) were included in the analysis. A significant time × group interaction was detected for aPWV ( p = 0.05, η2 = 0.099), RMSSD ( p = 0.010, η2 = 0.161), low-frequency power ( p = 0.009, η2 = 0.165), high-frequency power ( p < 0.001, η2 = 0.272), and the LF/HF ratio ( p < 0.001, η2 = 0.354). The INT group revealed significant improvements for the respective parameters. School-based HIIT can induce improvements in cardiovascular parameters. These results highlight the potential of embedding HIIT within the school setting, offering a time-efficient exercise intervention.

Hemodynamic evaluation in preterm infants using ultrasonic cardiac output monitor (USCOM).

We aimed to establish reference ranges for USCOM parameters in preterm infants, determine factors that affect cardiac output, and evaluate the measurement repeatability. This retro-prospective study was performed at Fondazione IRCCS San Gerardo dei Tintori, Monza, Italy. We included infants below 32 weeks of gestational age (GA) and/or 1500 g of birth weight (BW). We excluded infants with congenital heart diseases or hemodynamic instability. Measurements were performed at 3 ± 1, 7 ± 2, and 14 ± 2 postnatal days. We analyzed 204 measurements from 92 patients (median GA = 30.57 weeks, BW = 1360 g). The mean (SD) cardiac output (CO) was 278 (55) ml/min/kg, cardiac index (CI) was 3.1 (0.5) L/min/m2, and systemic vascular resistance (SVRI) was 1292 (294) d*s*cm-5/m2. CO presented a negative correlation with postmenstrual age (PMA), while SVRI presented a positive correlation with PMA. The repeatability coefficient was 31 ml/kg/min (12%).  Conclusion: This is the first study describing reference values for USCOM parameters in hemodynamically stable preterm infants and factors affecting their variability. Further studies to investigate the usefulness of USCOM for the longitudinal assessment of patients at risk for cardiovascular instability or monitoring the response to therapies are warranted. What is Known: • The ultrasonic cardiac output monitoring (USCOM) has been widely used on adult and pediatric patients and reference ranges for cardiac output (CO) by USCOM have been established in term infants. What is New: • We established reference values for USCOM parameters in very preterm and very-low-birth-weight infants; the reference ranges for CO by USCOM in the study population were 198-405 ml/kg/min. • CO normalized by body weight presented a significant negative correlation with postmenstrual age (PMA); systemic vascular resistance index presented a significant positive correlation with PMA.