Coronary Microvascular Resistance Research Articles

[Angina and no obstruction on coronary angiography : New approaches to the diagnosis and treatment of vasomotor disorders].

Clinical management of patients with angina and no obstructive coronary artery disease (ANOCA) is still challenging. This scenario affects up to 50% of patients undergoing diagnostic coronary angiography due to suspected coronary artery disease. Many patients report along and debilitating history before adequate diagnostics and management are initiated. This article describes the current recommendations for diagnostic assessments and treatment in patients with ANOCA. Focus is placed on invasive diagnostics in the catheter laboratory, pharmacological/interventional treatment as well as the patient journey. In patients with ANOCA, the current European Society of Cardiology (ESC) guidelines suggest that invasive assessments using acetylcholine and adenosine for the diagnosis of an underlying coronary vasomotor disorder should be considered. Acetylcholine is used to diagnose coronary spasm, whereas adenosine is used in conjunction with awire-based assessment for the measurement of coronary flow reserve and microvascular resistance. The invasive assessments allow the determination of what are referred to as endotypes (coronary spasm, impaired coronary flow reserve, enhanced microvascular resistance or acombination thereof). Establishing adiagnosis is helpful to: (a)initiate targeted treatment to improve quality of life, (b)reassure the patient that acardiac cause is found and (c)to assess individual prognosis. Currently, patients with ANOCA are often not adequately managed. Referral to specialised centres is recommended to prevent long and debilitating patient histories until expertise in diagnosis and treatment becomes more widespread.

Impact of coronary hyperemia on collateral flow correction of coronary microvascular resistance indices.

Recently, a novel method to estimate wedge pressure (Pw)-corrected minimal microvascular resistance (MR) was introduced. However, this method has not been validated since, and there are some theoretical concerns regarding the impact of different physiological conditions on the derivation of Pw measurements. This study sought to validate the recently introduced method to estimate Pw-corrected MR in a Doppler-derived study population and to evaluate the impact of different physiological conditions on the Pw measurements and the derivation of Pw-corrected MR. The method to derive "estimated" hyperemic microvascular resistance (HMR) without the need for Pw measurements was validated by estimating the coronary fractional flow reserve (FFRcor) from myocardial fractional flow reserve (FFRmyo) in a Doppler-derived study population (N = 53). From these patients, 24 had hyperemic Pw measurements available for the evaluation of hyperemic conditions on the derivation of Pw and its effect on the derivation of both "true" (with measured Pw) and "estimated" Pw-corrected HMR. Nonhyperemic Pw differed significantly from Pw measured in hyperemic conditions (26 ± 14 vs. 35 ± 14 mmHg, respectively, P < 0.005). Nevertheless, there was a strong linear relationship between FFRcor and FFRmyo in nonhyperemic conditions (R2 = 0.91, P < 0.005), as well as in hyperemic conditions (R2 = 0.87, P < 0.005). There was a strong linear relationship between "true" HMR and "estimated" HMR using either nonhyperemic (R2 = 0.86, P < 0.005) or hyperemic conditions (R2 = 0.85, P < 0.005) for correction. In contrast to a modest agreement between nonhyperemic Pw-corrected HMR and apparent HMR (R2 = 0.67, P < 0.005), hyperemic Pw-corrected HMR showed a strong agreement with apparent HMR (R2 = 0.88, P < 0.005). We validated the calculation method for Pw-corrected MR in a Doppler velocity-derived population. In addition, we found a significant impact of hyperemic conditions on the measurement of Pw and the derivation of Pw-corrected HMR.NEW & NOTEWORTHY The following are what is known: 1) wedge-pressure correction is often considered for the derivation of indices of minimal microvascular resistance, and 2) the Yong method for calculating wedge pressure-corrected index of microvascular resistance (IMR) without balloon inflation has never been validated in a Doppler-derived population and has not been tested under different physiological conditions. This study 1) adds validation for the Yong method for calculated wedge-pressure correction in a Doppler-derived study population and 2) shows significant influence of the physiological conditions on the derivation of coronary wedge pressure.

Coronary microvascular resistance comparison of coronary arteries with and without considering vascular diameter: A retrospective, single‐center study

AbstractBackground and AimsMeasurement of coronary microvascular resistance (MR) is essential for diagnosing nonocclusive coronary artery ischemia, but whether coronary branches of different diameters can be similarly assessed using hyperemic microvascular resistance index (hMVRI) calculated from average peak velocity (APV) remains unclear. We investigated the relationship between coronary arteries of different diameters and hMVRI.MethodsThirty patients with suspected angina pectoris and nonobstructive coronary stenosis with fractional flow reserve &gt;0.8 underwent evaluation of all coronary arteries using a Doppler velocity and pressure‐equipped guidewire. Quantitative coronary angiography (QCA) was used to analyze vessel diameter (DQCA). Coronary blood flow (CBFQCA) was calculated as πDQCA2/4 (0.5 × APV) and hMVRIQCA as distal coronary pressure divided by CBFQCA during maximal hyperemia.ResultsThe hMVRI was significantly higher for the right coronary artery than for the left anterior descending artery, but no significant differences between arteries were seen for CBFQCA and hMVRIQCA. Although the correlation between CBFQCA and APV was weak, CBFQCA divided into three groups according to DQCA showed very strong correlations with APV. Slopes of the straight line between APV and CBFQCA for small‐, middle‐, and large‐diameter groups were 0.48, 0.30, and 0.21, respectively, with slope decreasing as diameter increased.ConclusionsComparative evaluation of MR in coronary branches with varying vessel diameters requires vessel diameter to be accounted for.

Angiography-based coronary microvascular assessment with and without intracoronary pressure measurements: a systematic review.

In recent years, several indices have been proposed for quantifying coronary microvascular resistance. We intended to conduct a comprehensive review that systematically evaluates indices of microvascular resistance derived from angiography. The objective of this study was to identify and analyze angiography-derived indices of microvascular resistance that have been validated against an invasive reference method. We aimed to compare their limits of agreement with their reference methods and explore their advantages and inherent limitations. We searched PubMed from inception until 2022 for studies on different techniques for quantifying microvascular resistance. Seven studies met the inclusion criteria. Five studies included techniques that applied calculations based solely on invasive angiography, and were validated against invasively measured thermodilution-derived index of microvascular resistance. The remaining two studies combined angiography with invasively measured intracoronary pressure data, and were validated against invasive Doppler measurements. We converted the ± 1.96 standard deviation limits of agreement with the reference method from the seven studies into percentages relative to the cut-off value of the reference method. The lower limits of agreement for angiography-based methods ranged from - 122 to - 60%, while the upper limits ranged from 74 to 135%. The range of the limits of agreement was considerably lower for the two combined angiography- and pressure-based methods, standing at - 52 to 60% and - 25 to 27%. Our findings suggest that combined angiography- and pressure-based methods provide a more reliable assessment of microvascular resistance compared to methods relying solely on angiography. Central illustration. Comparative assessment of image-based methods quantifying microvascular resistance with and without intracoronary pressure measurements. Angiography-based methods rely on angiography alone to calculate the microvascular resistance by utilizing angiographic frame counting to extrapolate coronary flow (Q) and subsequently deriving distal coronary pressure using fluid dynamic equations. Combined angiography- and pressure-based methods utilize invasive intracoronary pressure gradients measured during rest and maximal vasodilation to determine coronary flow in their calculation of microvascular resistance. The combined methods showed more acceptable levels of agreement with their reference methods compared to angiography-based methods alone.

Gender-related differences in absolute coronary flow and microvascular resistance in patients with angina and non-obstructed coronary arteries (ANOCA)

Abstract Background Women with angina more often have non-obstructive coronary artery disease (ANOCA) compared to males. Coronary microvascular dysfunction (CMD) is responsible for angina in a sizable proportion of ANOCA patients. Intracoronary continuous thermodilution allows direct quantification of absolute coronary flow (Q) and microvascular resistance (Rµ). Purpose To evaluate gender-related differences in the prevalence and pattern of CMD assessed with intracoronary continuous thermodilution in ANOCA patients. Specifically, we assessed resting and hyperemic Q (Qrest and Qhyper), R (Rµ,rest and Rµ,hyper), coronary flow reverse (CFR), and microvascular resistance reserve (MRR) in ANOCA patients stratified by gender. Methods Single-center, prospective study of patients with ANOCA. CMD was invasively assessed by intracoronary continuous thermodilution in the left anterior descending artery (LAD) and defined as CFR&amp;lt;2.5. Results A total of 118 patients (n=49 females and n= 69 males) were enrolled. The mean patient age was 65 years. The mean fractional flow reserve (FFR) was 0.85±0.04, with no difference between the 2 genders. There was no difference in Rµ,rest, Qrest and Qhyper between the two genders. However, Rµ,hyper were higher in females compared to males (p=0.003). Among patients with ANOCA, CMD was more prevalent in females (28% vs 22%, p=0.014). Yet, in both females and males with CMD, a higher Qrest was observed compared to patients without CMD. In male patients, also Qhyper was lower in CMD patients versus those without CMD. Conclusion Among patients with ANOCA and investigated with intracoronary continuous thermodilution, CMD appeared more prevalent in females compared to males. Females had higher microvascular Rµ,hyper compared to males. In both genders, CMD was characterized by higher Qrest, suggestive of functional rather than structural CMD.

Endotypes of coronary microvascular dysfunction in patients with and without Diabetes Mellitus

Abstract Background Coronary microvascular dysfunction (CMD) is an early feature of diabetic cardiomyopathy, which usually precedes the onset of ventricular dysfunction. Continuous intracoronary thermodilution allows an accurate and reproducible assessment of absolute coronary blood flow and microvascular resistance thus allowing the evaluation of coronary flow reserve (CFR) and Microvascular Resistance Reserve (MRR). Recently, two different endotypes of CMD, structural and functional were identified, based on CFR and minimal resistance (Rm-hyp) values. Purpose To compare the patterns of CMD among patients with and without diabetes mellitus by continuous intracoronary thermodilution. Methods Consecutive patients with angina and non-obstructive coronary artery disease undergoing absolute flow measurement with continuous intracoronary thermodilution between 2020 and 2022 were included. Considering a CFR threshold of 2.5, patients were divided into 4 groups, CMD with and without diabetes (DM-CMD and NDM-CMD respectively), and two control groups with and without diabetes (DM-Control and NDM-Control group, respectively). Rm-hyp threshold of 390 (median value) was used to divide structural and functional endotypes (Rm-hyp above or below the threshold respectively). Results 204 patients were included (NDM-CMD=62 vs NDM-Control=77 and dm-CMD=38 vs dm-Control=27). The prevalence of CMD among diabetic patients was 58%. Both CFR and MRR were significantly reduced in both CMD groups compared to the control groups. DM-CMD and NDM-CMD patients had both lower Rm-hyp and higher Rm-rest as compared to the control groups. Among patients with CMD, DM-CMD had higher Rm-hyp compared to NDM-CM patients (480±163 vs 420±124 WU, respectively, p=0.04) and had a higher prevalence of structural endotype (78% vs 58%), p=0.03) which was higher among patients with insulin-dependent diabetes than in those without. Conclusions In patients with DM structural microvascular dysfunction is the most prevalent endotype. Functional endotype is more frequent among those with non-insuline dependent DM. Therefore, CMD in diabetic patients appears to be a continuum, evolving from a functional pattern to a structural one as the disease progresses.

Diseases of the Coronary Microcirculation: Diagnosis and Treatment.

Coronary microvascular dysfunction (CMD) comprises a variety of pathogenic mechanisms that impair the microcirculation of the heart. Clinical studies have shown that 30-50% of patients suffering from myocardial ischemia without significant coronary artery stenosis have CMD. The disease is associated with elevated mortality and poor quality of life. Whenever a patient presents with symptoms of angina pectoris and no underlying disease is detected by the usual methods, CMD should be considered a possible cause. This review is based on publications retrieved by a selective search in PubMed and on current international guidelines and recommendations of specialty societies. The diagnosis of CMD is based on objective evidence of a microvascular origin of symptoms. The guidelines contain a class IIa recommendation for invasive coronary flow reserve and microvascular resistance measurements. Noninvasive tests such as positron emission tomography and cardiac magnetic resonance imaging are less accurate and are given a class IIb recommendation. No high-quality therapeutic trials are available to date, and the treatment of CMD is thus based on that of chronic coronary syndrome. Lifestyle modification is performed to reduce risk factors. Patients with an abnormal coronary flow reserve or elevated microvascular resistance can be treated with an ACE inhibitor or angiotensin receptor blocker. Beta-blockers and calcium channel antagonists can relieve angina pectoris. Statins lower the LDL level and have positive pleiotropic effects. First-line treatment can be supplemented with further medications. Approximately 25% of patients with CMD have symptoms that do not respond to intensive treatment with the currently available modalities. New treatments, including interventional therapies, are being studied. Their long-term benefit remains to be assessed and compared to that of the existing methods.

Impact of age on the outcomes of Takotsubo syndrome

BackgroundThe impact on age on the short-term and long-term prognosis in patients with Takotsubo syndrome (TTS) is unclear. We aimed to evaluate whether age has prognostic implications during hospital stay and long-term follow-up of TTS patients. Methods688 consecutive patients were admitted for TTS in 7 tertiary centers from January-2008 to June-2021. We divided our cohort into two groups (patients <75 years and ≥75 years). Clinical, analytical, and hemodynamic variables as well as in-hospital management were registered and compared between groups. Mortality rates during hospital stay and follow-up were assessed. Adverse cardiovascular events (ACE) were defined as the composite of cardiovascular death, heart failure event, acute myocardial infarction, stroke and symptomatic arrhythmia. ResultsMedian age was 74.7 years and 49.4 % were ≥75 years. 86.9 % were women and 22.3 % were secondary forms of TTS. In-hospital mortality was 3.6 % (1.5 % cardiovascular). Median clinical follow-up was 4.3 years. Mortality during the follow-up period was 23 % (5.0 % cardiovascular) while ACE were 22.5 %, mainly due to heart failure events. Kaplan-Meier curves showed both higher rates of mortality and ACE in ≥75 years group (30.2 % vs 15.8 %; p < 0.001 and 28.3 % vs 16.7 %; p < 0.001). Age was independently associated with higher rates of overall mortality and ACE in patients with TTS. Hypertension, absence of sinus rhythm, Killip class > I and a more impaired coronary microvascular resistance were also associated to ACE in TTS patients. ConclusionsAdvanced age was associated with higher rate of overall mortality and ACE during long-term follow-up in TTS patients.

Continuous vs Bolus Thermodilution to Assess Microvascular Resistance Reserve.

Coronary flow reserve (CFR) and microvascular resistance reserve (MRR) can, in principle, be derived by any method assessing coronary flow. The aim of this study was to compare CFR and MRR as derived by continuous (CFRcont and MRRcont) and bolus thermodilution (CFRbolus and MRRbolus). A total of 175 patients with chest pain and nonobstructive coronary artery disease were studied. Bolus and continuous thermodilution measurements were performed in the left anterior descending coronary artery. MRR was calculated as the ratio of CFR to fractional flow reserve and corrected for changes in systemic pressure. In 102 patients, bolus and continuous thermodilution measurements were performed in duplicate to assess test-retest reliability. Mean CFRbolus was higher than CFRcont (3.47 ± 1.42 and 2.67 ± 0.81 [P< 0.001], mean difference 0.80, upper limit of agreement 3.92, lower limit of agreement-2.32). Mean MRRbolus was also higher than MRRcont (4.40 ± 1.99 and 3.22 ± 1.02 [P< 0.001], mean difference 1.2, upper limit of agreement 5.08, lower limit of agreement-2.71). The correlation between CFR and MRR values obtained using both methods was significant but weak (CFR, r=0.28 [95%CI: 0.14-0.41]; MRR, r=0.26 [95%CI: 0.16-0.39]; P< 0.001 for both). The precision of both CFR and MRR was higher when assessed using continuous thermodilution compared with bolus thermodilution (repeatability coefficients of 0.89 and 2.79 for CFRcont and CFRbolus, respectively, and 1.01 and 3.05 for MRRcont and MRRbolus, respectively). Compared with bolus thermodilution, continuous thermodilution yields lower values of CFR and MRR accompanied by an almost 3-fold reduction of the variability in the measured results.

Towards refining of the proposed ECG-based index of coronary microvascular resistance (ECGMVR).

Assessment of the coronary microcirculation via noninvasive indices of coronary microvascular resistance (MVR), based on coronary angiography (AngioMVR) is currently implemented in patients undergoing coronary angiography, and it is employed by many laboratories. Recently, a proposal has been presented of a new index of MVR, based on the duration of the transient electrocardiogram repolarization and depolarization changes emerging during coronary angiography (ECGMVR). It is paramount that the ECGMVR, which does not require any special expertise, new equipment, additional personnel and costs, or prolongation of the catheterization procedure, undergoes correlation with currently utilized indices of AngioMVR, the TIMI frame count index, and the invasive indices assessing the coronary epicardial and microvasculature states, for its validation. Some additional insights are also included in the present communication for the refinement of ECGMVR implementation.

Sex differences in coronary microvascular resistance measured by a computational fluid dynamics model.

Increased coronary microvascular resistance (CMVR) is associated with coronary microvascular dysfunction (CMD). Although CMD is more common in women, sex-specific differences in CMVR have not been demonstrated previously. To compare CMVR between men and women being investigated for chest pain. We used a computational fluid dynamics (CFD) model of human coronary physiology to calculate absolute CMVR based on invasive coronary angiographic images and pressures in 203 coronary arteries from 144 individual patients. CMVR was significantly higher in women than men (860 [650-1,205] vs. 680 [520-865] WU, Z = -2.24, p = 0.025). None of the other major subgroup comparisons yielded any differences in CMVR. CMVR was significantly higher in women compared with men. These sex-specific differences may help to explain the increased prevalence of CMD in women.

Quantitative Microvascular Resistance (QMR) Derived From Functional Coronary Angiography is Associated With Doppler-Derived Coronary Microvascular Resistance

Quantitative Microvascular Resistance (QMR) Derived From Functional Coronary Angiography is Associated With Doppler-Derived Coronary Microvascular Resistance

Effects of ticagrelor and prasugrel on coronary microcirculation in elective percutaneous coronary intervention

ObjectiveTo compare the effects of ticagrelor and prasugrel on absolute coronary blood flow (Q) and microvascular resistance (R) in patients with stable coronary artery disease (CAD) treated with elective percutaneous...

Coronary Physiology: Modern Concepts for the Guidance of Percutaneous Coronary Interventions and Medical Therapy.

Recent evidence on ischemia, rather than coronary artery disease (CAD), representing a major determinant of outcomes, has led to a progressive shift in the management of patients with ischemic heart disease. According to most recent guidelines, myocardial revascularization strategies based on anatomical findings should be progressively abandoned in favor of functional criteria for the guidance of PCI. Thus, emerging importance has been assigned to the assessment of coronary physiology in order to determine the ischemic significance of coronary stenoses. However, despite several indexes and tools that have been developed so far, the existence of technical and clinical conditions potentially biasing the functional evaluation of the coronary tree still cause debates regarding the strategy of choice. The present review provides an overview of the available methods and the most recent acquirements for the invasive assessment of ischemia, focusing on the most widely available indexes, fractional flow reserve (FFR) and instant-wave free ratio (iFR), in addition to emerging examples, as new approaches to coronary flow reserve (CFR) and microvascular resistance, aiming at promoting the knowledge and application of those "full physiology" principles, which are generally advocated to allow a tailored treatment and the achievement of the largest prognostic benefits.

The Proportion of Circulating CD45RO+CD8+ T Cells is Associated with the Coronary Slow Flow.

Circulating memory CD8+ T cells have been shown to be a crucial mediator of chronic inflammation. This study investigated whether the baseline proportion of circulating CD45RO+CD8+ T cells was associated with the coronary slow flow (CSF) phenomenon. A total of 160 consecutive patients [mean (standard deviation (SD)) age, 67.86 (9.55) years; 51.25% male] who were admitted to our hospital between August 2020 and October 2020 for chest pain and underwent coronary angiography with the absence of coronary stenosis were enrolled in this cross-sectional analysis. The patients' admission CD45RO+ CD8+ T cell plasma levels were measured using flow cytometry. Angiographic CSF was defined as thrombolysis in myocardial infarction (TIMI) flow of ≤ 2 without coronary stenosis, and non-CSF was defined as coronary arteries (< 50% stenosis) with TIMI 3 flow. The incidence of angiographic CSF was 22.5%. Patients with angiographic CSF had higher levels of CD45RO+CD8+ T cells than those without CSF [56.18 (13.93) vs. 45.26 (16.45); p < 0.001]. After multivariable adjustment, the risk of incident CSF was 2.41 [95% confidence interval (CI) 1.46-3.97] per SD change in CD45RO+ CD8+ T cells. Further, coronary microvascular resistance was significantly higher in patients with CSF than in those without CSF. A positive linear relationship between CD45RO+CD8+ T cells and coronary microvascular resistance was observed. The proportion of circulating CD45RO+CD8+ T cells is an independent indicator of CSF. This observation may provide insights into the pathophysiological mechanism of CSF.

Randomized, crossover, controlled trial on the modulation of cardiac coronary sinus hemodynamics to develop a new treatment for microvascular disease: Protocol of the MACCUS trial.

Microvascular angina (MVA) is a frequent condition for which our understanding of the disease pathophysiology and therapeutic perspectives remain unsatisfactory. The current study is designed to test whether an improvement in microvascular resistances could be achieved by elevating backward pressure in the coronary venous system, based on the hypothesis that an increase in hydrostatic pressure could cause a dilatation of the myocardial arterioles, resulting in a reduction of vascular resistances. This approach might have potential clinical implications, as it might suggest that interventions aimed at increasing coronary sinus (CS) pressure might result in a decrease in angina in this subset of patients. The aim of our single-center, sham-controlled, crossover randomized trial is to investigate the effect of an acute increase in CS pressure on a number of parameters of coronary physiology, including parameters of coronary microvascular resistance and conductance. A total of 20 consecutive patients with angina pectoris and coronary microvascular dysfunction (CMD) will be enrolled in the study. Hemodynamic parameters including aortic and distal coronary pressure, CS and right atrial pressure, and the coronary microvascular resistance index will be measured at rest and during hyperemia in a randomized crossover design during incomplete balloon occlusion ("balloon") and with the deflated balloon in the right atrium ("sham"). The primary end point of the study is the change in index of microvascular resistances (IMR) after acute modulation of CS pressure, while key secondary end points include changes in the other parameters. The aim of the study is to investigate whether occlusion of the CS is associated with a decrease in IMR. The results will provide mechanistic evidence for the development of a treatment for patients with MVA. https://clinicaltrials.gov/, identifier NCT05034224.

A proposal of a new index of coronary microvascular resistance based on the duration of the transient ECG repolarization changes during coronary angiography.

Coronary microvascular dysfunction is present in the majority of patients with acute coronary syndromes, myocardial infarction with nonobstructive coronary arteries, and takotsubo syndrome. Assessment of the coronary microcirculation via a noninvasive index of coronary microvascular resistance (CMVR) based on coronary angiography is currently employed by many laboratories (AngioMVR). A proposal is presented herein of a new index of CMVR, based on the duration of the transient ECG repolarization changes during coronary angiography (ECGMVR), well known to occur in patients with and without coronary artery disease, and specific for the left and right coronary artery contrast injections, which have been widely documented, starting 60 years ago. It will be imperative for the index of ECGMVR to be correlated with the currently implemented AngioMVR and the TIMI frame count index, for the validation of the ECGMVR.

851 REPEATABILITY OF BOLUS AND CONTINUOUS THERMODILUTION FOR ASSESSING CORONARY MICROVASCULAR FUNCTION

Abstract Introduction The bolus thermodilution-derived index of microcirculatory resistance (IMR) has emerged over years as the standard of reference to invasively define coronary microvascular dysfunction (CMD). However, the technique still presents some limitations, mainly related to the fact that manual injection of saline bolus accounts for some variance in the measurements. Continuous intracoronary thermodilution has been recently introduced as a tool to directly quantify absolute coronary flow and microvascular resistance both at rest and during hyperemia and has shown to be safe and operator independent. Microvascular resistance reserve (MRR), derived from continuous thermodilution, has been validated as novel index specific for microcirculation and independent from myocardial mass. Purpose To compare head-to-head the intra-observer repeatability of bolus and continuous thermodilution for assessing microvascular function. Methods Patients undergoing coronary angiography in the absence of obstructive coronary artery disease were prospectively enrolled. Bolus and continuous intracoronary thermodilution measurements were performed in duplicates in the left anterior descending artery (LAD). Patients were randomly assigned in a 1:1 ratio to undergo first bolus thermodilution or first continuous thermodilution assessment. Results A total of 102 patients were enrolled. Average FFR was 0.86±0.06. Coronary Flow Reserve (CFR) calculated with continuous thermodilution (CFRthermo) was significantly lower than bolus thermodilution-derived CFR (CFRbolus) (2.63±0.65 and 3.29±1.17, respectively, p&amp;lt;0.001). CFRthermo showed a lower variability and a higher agreement than CFRbolus (variability 12.74 ± 10.41% vs 31.26±24.85%, respectively, p&amp;lt;0.001; ICC= 0.78 (0.70-0.85) and 0.48 (0.32-0.62), respectively, p&amp;lt;0.001, Figure 1). Both MRR and IMR showed a good agreement (ICC 0.81 (0.74-0.87) and 0.80 (0.71-0.86)) but the variability of the MRR was significantly lower (12.44 ± 10.06% vs 24.24±19.27, respectively, p&amp;lt;0.001, figure 1). Reproducibility data of all indices derived from duplicated measurements of bolus and continuous thermodilution are reported in Figure 2. Conclusion Continuous intracoronary thermodilution has a higher repeatability than bolus thermodilution in the assessment of CMD.

Assessment of absolute coronary flow and microvascular resistance reserve in patients with severe aortic stenosis

Abstract Introduction The development of left ventricular hypertrophy in patients with severe aortic stenosis (AS) is accompanied by adaptive coronary flow regulation, both in epicardial and microvascular compartment, which ultimately lead to a chronic ischemic insult even in the absence of obstructive coronary artery disease. Intracoronary continuous thermodilution of saline through a dedicated infusion catheter is a novel tool that allows to measure absolute coronary flow and microvascular resistance at rest and during hyperemia and to calculate both coronary flow reserve (CFR) and Microvascular Resistance Reserve (MRR) Purpose We aimed to assess absolute coronary flow, microvascular resistance, CFR and MRR in patients with AS, by continuous intracoronary thermodilution, comparing these hemodynamic findings with a propensity-score matched contemporary cohort of patients without AS. Methods Absolute coronary blood flow and microvascular resistance were measured by continuous thermodilution in 29 patients with AS and compared to 15 controls matched for age, gender, diabetes mellitus and functional severity of epicardial coronary lesions. Myocardial work, total myocardial mass and LAD-specific mass were quantified by echocardiography and cardiac-CT. Results Patients with AS presented a significantly positive LV remodeling with lower global longitudinal strain and higher global work index compared to controls (p&amp;lt;0.02). Total LV myocardial mass and LAD-specific myocardial mass were significantly higher in patients with AS. Compared to matched controls, absolute resting flow in the LAD was significantly higher in the AS cohort (86 [66–107] ml/min vs 68 [52–75] ml/min, p=0.036), resulting, in lower CFR (2.30±0.69 vs 2.89±0.77, p=0.005) and MRR (2.73±0.74 vs 3.53±0.95, p=0.005) in the AS cohort compared to controls (Figure 1). No differences were found in hyperemic flow and resting and hyperemic resistances. Interestingly, hyperemic myocardial perfusion (calculated as the ratio between the absolute coronary flow in the LAD and the mass subtended by the vessel, expressed in mL/min/g), but not resting, was significantly lower in the AS group (1.9 [1.5–2.5] ml/min/g vs 2.3 [2–3.1] ml/min/g p=0.036). Conclusions In patients with severe aortic stenosis and non-obstructive coronary artery disease, with the progression of LVH, the compensatory mechanism of increased resting flow maintains an adequate perfusion at rest, but not during hyperemia (Figure 2). As consequence, both CFR and MRR are significantly impaired. Funding Acknowledgement Type of funding sources: None.

Microvascular dysfunction in patients with diabetes mellitus: assessment of absolute coronary flow and microvascular resistance reserve

Abstract Background Coronary microvascular dysfunction (CMD) is an early feature of diabetic cardiomyopathy, which usually precedes the onset of systolic and diastolic dysfunction (DDF). Continuous intracoronary thermodilution allows an accurate and reproducible assessment of absolute coronary blood flow and microvascular resistance thus allowing the evaluation of coronary flow reserve (CFR) and Microvascular Resistance Reserve (MRR), a novel index specific for microvascular function, which is independent from the myocardial mass. In the present study we compared absolute coronary flow and resistance, CFR and MRR assessed by continuous intracoronary thermodilution in diabetic versus non-diabetic patients. Left atrial reservoir strain (LASr), an early marker of DDF was compared between the two groups. Methods In this observational retrospective study, 108 patients with suspected angina and non-obstructive coronary artery disease (NOCAD) consecutively undergoing elective coronary angiography (CAG) from September 2018 to June 2021 were enrolled. The invasive functional assessment of microvascular function was performed in the left anterior descending artery (LAD) with intracoronary continuous thermodilution. Patients were classified according to the presence of DM. Absolute resting and hyperemic coronary flow (in mL/min) and resistance (in WU) were compared between the two cohorts. FFR was measured to assess coronary epicardial lesions, while CFR and MRR were calculated to assess microvascular function. LAS, assessed by speckle tracking echocardiography, was used to detect early myocardial structural changes potentially associated with microvascular dysfunction. Results The median FFR value was 0.83 [0.79–0.87] without any significant difference between the two groups. Absolute resting and hyperemic flow in the left anterior descending coronary were similar between diabetic and non-diabetic patients. Similarly, resting and hyperemic resistances did not change significantly between the two groups. In the DM cohort the CFR and MRR were significantly lower compared to the control group (CFR=2.4±0.6 and 2.9±0.8; MRR=2.8±0.9 and 3.5±1 for diabetic and non-diabetic patients respectively, [p&amp;lt;0.05 for both], Figure 1 and 2). Likewise, diabetic patients had a significantly lower reservoir, contractile and conductive LAS (all p&amp;lt;0.05). Conclusions Compared with non-diabetic patients, CFR and MRR were lower in patients with DM and non-obstructive epicardial coronary arteries, while both resting and hyperemic coronary flow and resistance were similar. LASr was lower in diabetic patients, confirming the presence of a subclinical DDF associated to the microcirculatory impairment. Continuous intracoronary thermodilution-derived indexes provide a reliable and operator-independent assessment of coronary macro- and microvasculature and might potentially facilitate widespread clinical adoption of invasive physiologic assessment of suspected microvascular disease. Funding Acknowledgement Type of funding sources: None.