Continuous Thermodilution Research Articles

Impact of vessel volume on thermodilution measurements in patients with coronary microvascular dysfunction.

Two invasive methods are available to estimate microvascular resistance: bolus and continuous thermodilution. Comparative studies have revealed a lack of concordance between measurements of microvascular resistance obtained through these techniques. This study aimed to examine the influence of vessel volume on bolus thermodilution measurements. We prospectively included patients with angina with non-obstructive coronary arteries (ANOCA) undergoing bolus and continuous thermodilution assessments. All patients underwent coronary CT angiographyto extract vessel volume. Coronary microvascular dysfunction was defined as coronary flow reserve (CFR) < 2.0. Measurements of absolute microvascular resistance (in Woods units) and index of microvascular resistance (IMR) were compared before and after volumetric adjustment. Overall, 94 patients with ANOCA were included in this study. The mean age was 64.7 ± 10.8 years, 48% were female, and 19% had diabetes. The prevalence of CMD was 16% based on bolus thermodilution, while continuous thermodilution yielded a prevalence of 27% (Cohen's Kappa 0.44, 95% CI 0.23-0.65). There was no correlation in microvascular resistance between techniques (r = 0.17, 95% CI -0.04 to 0.36, p = 0.104). The adjustment of IMR by vessel volume significantly increased the agreement with absolute microvascular resistance derived from continuous thermodilution (r = 0.48, 95% CI 0.31-0.63, p < 0.001). In patients with ANOCA, invasive methods based on coronary thermodilution yielded conflicting results for the assessment of CMD. Adjusting IMR with vessel volume improved the agreement with continuous thermodilution for the assessment of microvascular resistance. These findings strongly suggest the importance of considering vessel volume when interpreting bolus thermodilution assessment.

Assessing the Impact of Prolonged Averaging of Coronary Continuous Thermodilution Traces

Continuous Thermodilution is a novel method of quantifying coronary flow (Q) in mL/min. To account for variability of Q within the cardiac cycle, the trace is smoothened with a 2 s moving average filter. This can sometimes be ineffective due to significant heart rate variability, ventricular extrasystoles, and deep inspiration, resulting in a fluctuating temperature trace and ambiguity in the location of the “steady state”. This study aims to assess whether a longer moving average filter would smoothen any fluctuations within the continuous thermodilution traces resulting in improved interpretability and reproducibility on a test–retest basis. Patients with ANOCA underwent repeat continuous thermodilution measurements. Analysis of traces were performed at averages of 10, 15, and 20 s to determine the maximum acceptable average. The maximum acceptable average was subsequently applied as a moving average filter and the traces were re-analysed to assess the practical consequences of a longer moving average. Reproducibility was then assessed and compared to a 2 s moving average. Of the averages tested, only 10 s met the criteria for acceptance. When the data was reanalysed with a 10 s moving average filter, there was no significant improvement in reproducibility, however, it resulted in a 12% diagnostic mismatch. Applying a longer moving average filter to continuous thermodilution data does not improve reproducibility. Furthermore, it results in a loss of fidelity on the traces, and a 12% diagnostic mismatch. Overall, current practice should be maintained.

Coronary Flow Reserve and Myocardial Resistance Reserve Changes After Transcatheter Aortic Valve Implantation in Aortic Stenosis

Aortic valve stenosis (AS) induces an alteration in hemodynamic conditions that are responsible for coronary microvasculature impairment. Relief of AS by transcatheter aortic valve implantation (TAVI) is expected to improve the coronary artery hemodynamic. We aimed to assess the midterm effects of TAVI in coronary flow reserve (CFR) and myocardial resistance reserve (MRR) by a continuous intracoronary thermodilution technique. At-rest and hyperemic coronary flow was measured by a continuous thermodilution technique in 23 patients with AS and compared with that in 17 matched controls, and repeated 6 ± 3 months after TAVI in 11 of the patients with AS. In patients with AS, absolute coronary flow at rest was significantly greater, and absolute resistance at rest was significantly less, than in controls (p <0.01 for both), causing less CFR and MRR (1.73 ± 0.4 vs 2.85 ± 1.1, p <0.01 and 1.95 ± 0.4 vs 3.22 ± 1.4, p <0.01, respectively). TAVI implantation yielded a significant 35% increase in CFR (p >0.01) and a 39% increase in MRR (p <0.01) driven by absolute coronary flow at rest reduction (p = 0.03). In patients with AS, CFR and MRR determined by continuous thermodilution are significantly impaired. At 6-month follow-up, TAVI improves these indexes and partially relieves the pathophysiologic alterations, leading to a partial restoration of CFR and MRR.

CASE-TB-02 - Comparison of Quantitative MR Perfusion with Continuous and Bolus Thermodilution to Assess Microvascular Function - Stratified Medical Therapy and Aortic Valve Replacement?

CASE-TB-02 - Comparison of Quantitative MR Perfusion with Continuous and Bolus Thermodilution to Assess Microvascular Function - Stratified Medical Therapy and Aortic Valve Replacement?

Coronary Microvascular Dysfunction in Patients With Heart Failure: Characterization of Patterns in HFrEF Versus HFpEF.

Coronary microvascular dysfunction (CMD) is involved in heart failure (HF) onset and progression, independently of HF phenotype and obstructive coronary artery disease. Invasive assessment of CMD might provide insights into phenotyping and prognosis of patients with HF. We aimed to assess absolute coronary flow, absolute microvascular resistance, myocardial perfusion, coronary flow reserve, and microvascular resistance reserve in patients with HF with preserved ejection fraction and HF with reduced ejection fraction (HFrEF). Single-center, prospective study of 56 consecutive patients with de novo HF with nonobstructive coronary artery disease divided into HF with preserved ejection fraction (n=21) and HFrEF (n=35). CMD was invasively assessed by continuous intracoronary thermodilution and defined as coronary flow reserve <2.5. Left ventricular and left anterior descending artery-related myocardial mass was quantified by echocardiography and coronary computed tomography angiography. Myocardial perfusion (mL/min per g) was calculated as the ratio between absolute coronary flow and left anterior descending artery-related mass. Patients with HFrEF showed a higher left ventricular and left anterior descending artery-related myocardial mass compared with HF with preserved ejection fraction (P<0.010). Overall, 52% of the study population had CMD, with a similar prevalence between the 2 groups. In HFrEF, CMD was characterized by lower absolute microvascular resistance and higher absolute coronary flow at rest (functional CMD; P=0.002). CMD was an independent predictor of a lower rate of left ventricular reverse remodeling at follow-up. In patients with HF with preserved ejection fraction, CMD was mainly due to higher absolute microvascular resistance and lower absolute coronary flow during hyperemia (structural CMD; P≤0.030). Continuous intracoronary thermodilution allows the definition and characterization of patterns with distinct CMD in patients with HF and could identify patients with HFrEF with a higher rate of left ventricular reverse remodeling at follow-up.

In vivo validation of intra-coronary absolute flow measurements and comparison of reliability between different microvascular indices and the microvascular resistance reserve

Abstract Background Coronary microvascular dysfunction plays a major role in patients with cardiac ischemia without flow limiting epicardial coronary stenosis, takotsubo cardiomyopathy, aortic valve stenosis and heart failure with preserved ejection fraction. In clinical practice, the index of microvascular resistance (IMR) and coronary flow reserve (CFR), and more recently the absolute coronary blood flow (ABF), absolute coronary resistance (ACR) and the microvascular resistance reserve (MRR) are used as parameters to measure resistance and flow using continuous coronary thermodilution. Purpose Firstly, to validate ABF measured with continuous coronary thermodilution in vivo against epicardial doppler-measured flow. Secondly, to assess reliability and reproducibility in-vivo of different microvascular indices. Methods For the purpose of this study coronary measurements were conducted in two large animal models and in patients, all with the appropriate ethical committee approval. For the first part of the study, fourteen sheep underwent repeated paired measurements of ABF and ACR (with use of continuous thermodilution) with different saline infusion speeds, as well as IMR, CFR and MRR in multiple coronary vessels. Seven additional sheep underwent these measurements while having simultaneous measurements with epicardial coronary flow probes (gold standard) in an open-chest model. The epicardial flow probes were placed on the proximal left anterior descending and circumflex artery. Maximal hyperemia was induced with adenosine (CFR and IMR) or infusion of saline at a rate of 30ml/min (ABF, ACR and MRR). For the second part of the study, in 41 patients receiving routine microvascular assessment, IMR and CFR measurements were duplicated by a single operator, after re-calibration, to assess the reproducibility of the measurement. The combined animal and human data resulted in the analysis of 408 coronary measurements made in 88 coronary vessels during 65 heart catheterizations. Results In sheep, ABF measured with continuous thermodilution (with saline infusion speeds from 5ml/min to 30ml/min) was accurate when compared with epicardial flow measurements. (Table 1, Fig 1A) Notably, the continuous thermodilution measurement had the tendency to slightly overestimate ABF. (Table 1, Fig 1B) The two methods were equivalent within 15% (Two one-sided test: mean difference: -8.73%; 95% CI: -14.40 to -3.06%, p= 0.016). When comparing test-retest reproducibility between the indices, CFR performed the worst while ACR and MRR performed the best. MRR had a significantly better reproducibility than the IMR. (Table 1, Fig 1C). Conclusion ABF can accurately be determined by continuous coronary thermodilution. MRR and ACR have a significantly superior reliability and reproducibility compared to IMR and CFR. Unlike ACR, MRR is not vessel or territory-size dependent and is therefore the index of choice for future research and clinical assessment of the microcirculation.

Microvascular Resistance Reserve assessed by bolus and continuous thermodilution

Abstract Aim The main limitation of Coronary flow reserve (CFR) as an index to assess coronary microvascular function, is that it is influenced by epicardial resistance. Microvascular Resistance Reserve (MRR) has been recently introduced as a metric that is truly specific for the coronary microcirculation. MRR can, in principle, be derived from any tool that measure flow and pressure. The aim of the present study was to compare CFR and MRR as derived by bolus (CFRbolus and MRRbolus, respectively) and continuous thermodilution (CFRcont and MRRcont, respectively). Methods and Results A total of 175 patients were studied. Bolus and continuous thermodilution measurements were performed in the LAD in all patients. The MRR was derived as a function of the coronary flow reserve (CFR) divided by the fractional flow reserve (FFR) and corrected for driving pressures. Coefficient of variation was calculated to assess the precision of both methods. Mean CFRbolus was higher than the corresponding value of CFRcont (3.47±1.42 and 2.67±0.81, respectively, p&amp;lt;0.001, mean bias 0.80). Also mean MRRbolus was higher than the corresponding value of MRRcont (4.40±1.99 vs 3.22±1.02, respectively p&amp;lt;0.001, mean bias 1.2) The correlation between CFR and MRR values obtained by both approaches was weak (R= 0.28 (0.14 to 0.41) for CFR; R=0.26 (0.16 to 0.39) for MRR; p&amp;lt;0.001 for both). Continuous thermodilution had a smaller dispersion of data for both CFR (CoV= 30.2% vs 46.6% respectively, p&amp;lt;0.001) and MRR (CoV= 31.7 % vs 45.2% vs, respectively, p&amp;lt;0.001). Conclusion Bolus thermodilution significantly overestimates continuous thermodilution-derived CFR and MRR and shows a larger scatter of the data. Therefore, bolus thermodilution seems a less appropriate method to assess microvascular function than is continuous thermodilution.

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.

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.

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.

Comprehensive invasive evaluation of coronary microcirculation in patients with Takotsubo syndrome

Background and aimsThe etiology and pathophysiology of Takotsubo syndrome (TTS) remain a matter of debate. In murine models of coronary microvascular dysfunction (CMD), abnormalities in myocardial perfusion led to the development of TTS. Importantly, TTS was reversible when normal perfusion was restored. However, in clinical practice, the assessment of coronary microcirculation in patients with TTS has primarily relied on non-invasive or indirect, angiography-derived methods. Methods and ResultsFor the first time, we performed invasive microcirculatory assessment, by both validated techniques currently available in the catheterization laboratory, namely intracoronary bolus and continuous thermodilution, in patients with TTS, upon hospital admission and at short term follow-up. Our findings demonstrate that CMD was consistently present in all patients upon hospital admission, as assessed by both techniques. At a median follow-up of 3 months, after the recovery of left ventricular ejection fraction, two third of patients no longer exhibited CMD. ConclusionsThese findings support the hypothesis that an acute and transient worsening in coronary microvascular function plays a pivotal role in the pathophysiology of TTS.

TCT-757 Accuracy of Pressure-Derived Coronary Flow Reserve Compared With Continuous Thermodilution in Patients With Coronary Microvascular Dysfunction

TCT-757 Accuracy of Pressure-Derived Coronary Flow Reserve Compared With Continuous Thermodilution in Patients With Coronary Microvascular Dysfunction

TCT-23 Comparison of Reliability Between Current Indices for Microvascular Assessment and the New Microvascular Resistance Reserve Using Continuous Coronary Thermodilution

TCT-23 Comparison of Reliability Between Current Indices for Microvascular Assessment and the New Microvascular Resistance Reserve Using Continuous Coronary Thermodilution

At the Right Place, at the Right Time. Reply to Vetrugno et al. Comparison between FlowTrac and Pulmonary Arterial Catheter in Off-Pump Cardiac Surgery Patients: "Why Did We Miss Our Appointment?". Comment on "Oh et al. Comparison between Fourth-Generation FloTrac/Vigileo System and Continuous Thermodilution Technique for Cardiac Output Estimation after Time Adjustment during Off-Pump Coronary Artery Bypass Graft Surgery: A

We thank Vetrugno et al. for their interest and comments [...].

Coronary Flow Reserve Assessed by Continuous Thermodilution Method

Coronary Flow Reserve Assessed by Continuous Thermodilution Method

Coronary Vascular (DYS) Function and Invasive Physiology Assessment: Insights into Bolus and Continuous Thermodilution Methods.

A considerable number of patients with angina or myocardial ischemia have no significant coronary artery disease on invasive angiography. In recent years, several steps towards a better comprehension of the pathophysiology of these conditions, angina or ischemia with non-obstructive coronary arteries (ANOCA/INOCA), have been made. Nevertheless, several gaps in knowledge still remain. This review is intended to provide a comprehensive overview of ANOCA and INOCA, with a particular focus on pathophysiology, recent diagnostic innovations, gaps in knowledge and treatment modalities.

Agreement between cardiac output estimation with a wireless, wearable pulse decomposition analysis device and continuous thermodilution in post cardiac surgery intensive care unit patients.

Pulse Decomposition Analysis (PDA) uses integration of the systolic area of a distally transmitted aortic pulse as well as arterial stiffness estimates to compute cardiac output. We sought to assess agreement of cardiac output (CO) estimation between continuous pulmonary artery catheter (PAC) guided thermodilution (CO-CCO) and a wireless, wearable noninvasive device, (Vitalstream, Caretaker Medical, Charlottesville, VA), that utilizes the Pulse Decomposition Analysis (CO-PDA) method in postoperative cardiac surgery patients in the intensive care unit. CO-CCO measurements were compared with post processed CO-PDA measurements in prospectively enrolled adult cardiac surgical intensive care unit patients. Uncalibrated CO-PDA values were compared for accuracy with CO-CCO via a Bland-Altman analysis considering repeated measurements and a concordance analysis with a 10% exclusion zone. 259.7h of monitoring data from 41 patients matching 15,583 data points were analyzed. Mean CO-CCO was 5.55L/min, while mean values for the CO-PDA were 5.73L/min (mean of differences +- SD 0.79 ± 1.11L/min; limits of agreement - 1.43 to 3.01L/min), with a percentage error of 37.5%. CO-CCO correlation with CO-PDA was moderate (0.54) and concordance was 0.83. Compared with the CO-CCO Swan-Ganz, cardiac output measurements obtained using the CO-PDA were not interchangeable when using a 30% threshold. These preliminary results were within the 45% limits for minimally invasive devices, and pending further robust trials, the CO-PDA offers a noninvasive, wireless solution to complement and extend hemodynamic monitoring within and outside the ICU.

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...

The quest for accurate tools to open the black box of the microcirculation: continuous thermodilution and MRR.

The quest for accurate tools to open the black box of the microcirculation: continuous thermodilution and MRR.

Comparison between FlowTrac and Pulmonary Arterial Catheter in Off-Pump Cardiac Surgery Patients: “Why Did We Miss Our Appointment?”. Comment on Oh et al. Comparison between Fourth-Generation FloTrac/Vigileo System and Continuous Thermodilution Technique for Cardiac Output Estimation after Time Adjustment during Off-Pump Coronary Artery Bypass Graft Surgery: A Retrospective Cohort Study. J. Clin. Med. 2022, 11, 6093

We read with great interest the study by Chahyun Oh et al., which compared estimates of cardiac output (CO) provided by the FloTrac system (CO-FloTrac) with those obtained with continuous thermodilution (COcont) after time adjustments using continuous recordings of intraoperative physiological datal [...].