Hemodynamic Assessment Of Patients Research Articles

Invasive testing leads to significantly altered (surgical) management strategy in coronary anomalies with interarterial course: 3 year interim analysis of MuSCAT

Abstract Introduction Diagnostic work-up of patients with an anomalous aortic origin of a coronary artery (AAOCA) includes an anatomical and functional assessment. The approach to functional evaluation currently varies widely and mainly includes noninvasive assessment. Intracoronary hemodynamic assessment can potentially enhance risk assessment for myocardial ischemia and sudden cardiac death and guide management of AAOCA patients. Hence, this study aims to evaluate invasive detection of ischemia on top of the standard of care diagnostic work-up for interarterial or intraseptal AAOCA and the impact on patient management. We report the first clinical outcomes. Methods In this multicenter prospective cohort study on AAOCA, all consecutive patients of 16 years and older with AAOCA with a newly diagnosed interarterial or intraseptal course in whom diagnostic work-up according to the protocol of the MuSCAT trial was performed between January 2021 and January 2024, were included for analysis. Exclusion comprised incomplete diagnostic evaluation, hemodynamically significant concomitant congenital heart disease or obstructive coronary artery disease in the AAOCA effluence. The work-up included invasive ischemia testing using fractional flow reserve (FFR) and or instantaneous wave-free ratio (iFR)/resting full-cycle ratio (RFR) at baseline and during pharmacological stress using adenosine, adrenaline and dobutamine. Results Fifty-eight patients (50% female, median age at AAOCA diagnosis 51.5 years (IQR 44.0-59.0)) were included, Table 1. The right coronary artery was anomalous in 88%, 93% patients had an interarterial and 69% an intramural course. Non-invasive ischemia detection was positive in 12%, negative in 84% and inconclusive in 4%. Invasive hemodynamic assessment was positive for ischemia in 22%, negative in 74% and inconclusive in 3%. Class of recommendation for surgery based on ESC guidelines was I or IIa in 28% patients and IIb, III or unclassified in 72%. Invasive hemodynamic assessment changed the treatment decision in 24% of the patients; 50% with initially recommended surgical treatment and 14% with initially a conservative treatment adjudication, Figure 1. Median follow-up after initial diagnosis was 20 [IQR 10-28] months and in 56% of all patients who completed 6 months follow-up the initial symptoms alleviated. One (2%) patient underwent a percutaneous re-intervention of the operated AAOCA. Conclusions This national prospective study of invasive hemodynamic assessment in patients with AAOCA showed clinically significant impact on the adjustment of initial management strategy in 24% of the patients. No cardiac death of myocardial infarction in the AAOCA supply area occurred during follow-up. Analysis of the complete follow-up of the MuSCAT trial can further substantiate the role of additional invasive functional imaging in AAOCA.

Automated intracranial vessel segmentation of 4D flow MRI data in patients with atherosclerotic stenosis using a convolutional neural network.

Intracranial 4D flow MRI enables quantitative assessment of hemodynamics in patients with intracranial atherosclerotic disease (ICAD). However, quantitative assessments are still challenging due to the time-consuming vessel segmentation, especially in the presence of stenoses, which can often result in user variability. To improve the reproducibility and robustness as well as to accelerate data analysis, we developed an accurate, fully automated segmentation for stenosed intracranial vessels using deep learning. 154 dual-VENC 4D flow MRI scans (68 ICAD patients with stenosis, 86 healthy controls) were retrospectively selected. Manual segmentations were used as ground truth for training. For automated segmentation, deep learning was performed using a 3D U-Net. 20 randomly selected cases (10 controls, 10 patients) were separated and solely used for testing. Cross-sectional areas and flow parameters were determined in the Circle of Willis (CoW) and the sinuses. Furthermore, the flow conservation error was calculated. For statistical comparisons, Dice scores (DS), Hausdorff distance (HD), average symmetrical surface distance (ASSD), Bland-Altman analyses, and interclass correlations were computed using the manual segmentations from two independent observers as reference. Finally, three stenosis cases were analyzed in more detail by comparing the 4D flow-based segmentations with segmentations from black blood vessel wall imaging (VWI). Training of the network took approximately 10 h and the average automated segmentation time was 2.2 ± 1.0 s. No significant differences in segmentation performance relative to two independent observers were observed. For the controls, mean DS was 0.85 ± 0.03 for the CoW and 0.86 ± 0.06 for the sinuses. Mean HD was 7.2 ± 1.5 mm (CoW) and 6.6 ± 3.7 mm (sinuses). Mean ASSD was 0.15 ± 0.04 mm (CoW) and 0.22 ± 0.17 mm (sinuses). For the patients, the mean DS was 0.85 ± 0.04 (CoW) and 0.82 ± 0.07 (sinuses), the HD was 8.4 ± 3.1 mm (CoW) and 5.7 ± 1.9 mm (sinuses) and the mean ASSD was 0.22 ± 0.10 mm (CoW) and 0.22 ± 0.11 mm (sinuses). Small bias and limits of agreement were observed in both cohorts for the flow parameters. The assessment of the cross-sectional lumen areas in stenosed vessels revealed very good agreement (ICC: 0.93) with the VWI segmentation but a consistent overestimation (bias ± LOA: 28.1 ± 13.9%). Deep learning was successfully applied for fully automated segmentation of stenosed intracranial vasculatures using 4D flow MRI data. The statistical analysis of segmentation and flow metrics demonstrated very good agreement between the CNN and manual segmentation and good performance in stenosed vessels. To further improve the performance and generalization, more ICAD segmentations as well as other intracranial vascular pathologies will be considered in the future.

Optimal hemodynamic parameters for risk stratification in acute pulmonary embolism patients.

Hemodynamic assessment of patients with pulmonary embolism (PE) remains a fundamental component of early risk stratification that in turn, influences subsequent monitoring and therapeutic strategies. The current body of literature and international evidence-based clinical practice guidelines focus mainly on the use of systolic blood pressure (SBP). The accuracy of this single hemodynamic parameter, however, and its optimal values for the identification of hemodynamic instability have been recently questioned by clinicians. For example, abnormal SBP or shock index may be a late indicator of adverse outcomes, signaling a patient in whom the cascade of hemodynamic compromise is already well underway. The aim of the present article is to review the current evidence supporting the use of SBP and analyze the potential integration of other parameters to assess the hemodynamic stability, impending clinical deterioration, and guide the reperfusion treatment in patients with PE, as well as to suggest potential strategies to further investigate this issue.

Combined evaluation of blood flow and tissue perfusion in diabetic feet by intra-arterial dynamic 4DCT imaging

Critical limb ischemia is associated with high mortality and major amputations. Intra-arterial digital subtraction angiography (IADSA) has been the reference standard but has some shortcomings including the two-dimensional projection and the lack of tissue perfusion information. The aim of this exploratory study is to examine four-dimensional computed tomography (4DCT) angiography and perfusion imaging using low-volume intra-arterial contrast injections for an improved anatomic and hemodynamic assessment in patients with foot ulcers. Three patients underwent a low-volume (2 mL) intra-arterial contrast-enhanced 4DCT examination combined with a diagnostic IADSA. An automated assessment of blood flow and tissue perfusion from the 4DCT data was performed. Vascular structures and corresponding blood flows were successfully assessed and correlated well with the IADSA results. Perfusion values of the affected tissue were significantly higher compared to the unaffected tissue. The proposed 4DCT protocol combined with the minimal usage of contrast agent (2 mL) provides superior images compared to IADSA as three phases (arterial, perfusion, and venous) are captured. The obtained parameters could allow for an improved diagnosis of critical limb ischemia as both the proximal vasculature and the extent of the perfusion deficit in the microvasculature can be assessed.Relevance statementIntra-arterial 4DCT allows for assessing three phases (arterial, perfusion and venous) using minimal contrast (2 mL). This method could lead to an improved diagnosis of critical limb ischemia as both proximal vasculature and the extent of the perfusion deficit are assessed.Trial registrationISRCTN, ISRCTN95737449. Registered 14 March 2023—retrospectively registered, https://www.isrctn.com/ISRCTN95737449Key points• Three phases (arterial, perfusion, and venous) are obtained from 2 mL intra-arterial 4DCT.• The obtained hemodynamic parameters correlated well with the IADSA findings.• 4DCT surpassed IADSA in terms of assessment of venous blood flow and inflammatory hyperperfusion.• The assessment of tissue perfusion could lead to optimizing the revascularization strategy.Graphical

C-22 | Translesional Assessment of Hemodynamics in Patients Undergoing Endovascular Therapy for Lower Extremity Peripheral Arterial Disease

C-22 | Translesional Assessment of Hemodynamics in Patients Undergoing Endovascular Therapy for Lower Extremity Peripheral Arterial Disease

Peculiarities of hemodynamic assessment in patients with centrifugal circulatory assist system

Peculiarities of hemodynamic assessment in patients with centrifugal circulatory assist system

Invasive Cardiopulmonary Hemodynamic Assessment in Patients with Advanced Heart Failure: How to Interpret?

Invasive Cardiopulmonary Hemodynamic Assessment in Patients with Advanced Heart Failure: How to Interpret?

Hemodynamic assessment in patients with preterm premature rupture of the membranes (pPROM)

ObjectiveThe aim of this study was to assess the hemodynamic differences in women with pPROM versus physiological pregnancies. Study designThis was a prospective case control study of 15 patients with pPROM and 45 controls. Patients and controls were submitted at enrollment to a non-invasive hemodynamic evaluation with UltraSonic Cardiac Output Monitor (USCOM), and to blood tests to check white blood cells count and C-reactive protein (CRP) levels. We followed pPROM patients until delivery noting fetal/neonatal and maternal unfavorable outcomes (maternal fever, APGAR 1′ and 5′< 7, stillbirth). ResultsPatients with pPROM showed higher values of cardiac output (9.1 ± 2.3 vs 7.1 ± 0.85, p < 0.01), lower systemic vascular resistances (792.1 ± 162 vs 1006.2 ± 110.7, p < 0.01), higher minute distance (32.3 ± 7.8 vs 25 ± 2.8, p < 0.01), lower Potential to Kinetic Energy Ratio (16.5 ± 5.3 vs 22.4 ± 6.8, p < 0.01), higher heart rate (97.5 ± 15.4 vs 82.4 ± 12, p < 0.01) and higher oxygen delivery (1313.2 ± 325.8 vs 1080.7 ± 151.8, p < 0.01) vs. controls. Six out of 15 pPROM patients had an unfavorable outcome. There were no significant differences in CRP levels and WBC count at admission in the two pPROM subgroups, whereas maternal hemodynamics was characterized by lower SVR (718 ± 72 vs 863 ± 123, p = 0.02) in subsequently complicated patients. ConclusionsMaternal hemodynamics is altered in pPROM patients, with a lower Systemic Vascular Resistance and higher Cardiac Output vs. controls. This hyperdynamic circulation appears to anticipates the changes of serum markers of inflammation (CRP, WBC count) and seems to be more pronounced at admission in pPROM patients developing unfavorable outcomes.

Invasive hemodynamic assessment of patients with cardiomyopathies

Invasive hemodynamic assessment of cardiac diseases has become an important diagnostic tool in recent decades. Non-invasive methods are the main techniques used to assess cardiac function, due to their wider availability. Cardiac catheterization is useful when there are diagnostic problems that cannot be solved with routine methods. Cardiac catheterization should be individualized according to the specific problems of the patient and based on the results from non-invasive methods. Invasive diagnostics is used in the assessment of patients with various cardiovascular diseases, including cardiomyopathies. In this review, we consider the role of cardiac catheterization, its advantages and disadvantages as part of the overall assessment of patients with cardiomyopathies. &amp;nbsp;

Graphical User Interface for Calculating Wave Intensity from Cardiac Catheterization Measurements.

Wave intensity analysis (WIA) as a framework to assess cardiovascular hemodynamics has been successfully used in many clinical applications. Typically, wave intensity calculations require the simultaneous acquisition of blood velocity and blood pressure at the same vascular site. Unfortunately, many hemodynamic parameters that are used to monitor pre-operative patient hemodynamic state use both invasively acquired blood pressure measurements in catheterization laboratory and non-invasively acquired blood velocity measurements. To utilize wave intensity analysis to assess patients undergoing cardiac interventional procedures, we have developed a graphical user interface (GUI) that uses standard clinical measurements which include invasive blood pressure waveforms and Doppler echocardiography images to calculate wave intensity parameters. The GUI consists of three main subroutines that allow clinicians to import raw data and extract and analyze the blood pressure and blood velocity signals separately. Using the electrocardiogram signals as an alignment marker, the re-formatted signals are aligned, and wave intensity is calculated. Wave intensity features such as forward compression wave (FCW), forward expansion wave (FEW) and wave speed are calculated and output in a table for statistical analysis. The GUI represents the first attempt to create a program that encourages clinicians to use WIA for hemodynamic assessment in patients undergoing cardiac catheterization procedures with the data they have already procured.

The Role of Perfusion Computed Tomography of the Liver in the Assessment of Hemodynamics in Patients with Compensated Cirrhosis of the Liver and the Presence of Type 2 Diabetes Mellitus. Pilot Study

Currently the relationship between liver diseases and glucose metabolism disorders is being studied. To characterize the negative impact of the mechanisms of insulin resistance on the liver parenchyma altered due to cirrhosis, we can use CT-perfusion of the liver — a method that allows us to assess hemodynamic disorders in the liver tissue. During the pilot study, it was found that the values of arterial perfusion and hepatic perfusion index in patients with compensated cirrhosis of the liver in the presence of type 2 diabetes mellitus were statistically significantly higher than in the absence of this pathology (p = 0,007 and p = 0,009 respectively). The values of portal and total perfusion in patients with compensated cirrhosis of the liver in the presence of type 2 diabetes mellitus were significantly lower than in the absence of this pathology (p &lt; 0,001 and p = 0,007 respectively). CT-perfusion of the liver can be used in patients with compensated cirrhosis and the presence of type 2 diabetes mellitus in the anamnesis as a non-invasive method of instrumental diagnosis of hemodynamic changes, including in assessing the progression of portal hypertension and the subsequent detection of concomitant complications.

Determination of the dominant arch by computational fluid dynamics analysis using computed tomography images in double aortic arch.

Computational fluid dynamics (CFD) analysis using computed tomography images can reveal the details of the blood flow in cardiovascular disease. In double aortic arch, it is difficult to assess the hemodynamics because of the strong influence of various anatomical features, such as the angle of the aortic bifurcation. In the present study, we reported that CFD analysis is a valuable method for hemodynamic assessment in patients with double aortic arch.

Assessment of hemodynamics in patients with hypertension using dry carbon dioxide baths and ozone therapy

BACKGROUND: Despite the wide prevalence of arterial hypertension in modern society, including in the Russian population, patients sometimes do not suspect the presence of the disease, and among patients with an established diagnosis, drug therapy has low effectiveness.&#x0D; AIMS: Of the study was to study the effect of dry carbon dioxide baths and ozone therapy on heart rate variability and reocardiography in patients with hypertension.&#x0D; MATERIALS AND METHODS: We observed 71 patients with stage I hypertension and grade 12 arterial hypertension. Patients were randomly selected into three groups: in the control group (n=18), patients received complex spa treatment, including diet, physical therapy, massage of the collar area and aromatherapy; in the comparison group (n=20) basic spa therapy and dry carbon dioxide baths; in the main group (n=33) basic spa therapy, ozone therapy and dry carbon dioxide baths.&#x0D; RESULTS: The combined use of dry carbon dioxide baths and ozone therapy in the complex treatment of patients with hypertension in sanatorium conditions is accompanied by a significant improvement in heart rate variability and central hemodynamics.&#x0D; CONCLUSION: Complex spa treatment of patients with hypertension with the additional appointment of dry carbon dioxide baths and ozone therapy helps to reduce the tension of the central mechanisms of regulation of the cardiovascular system, restore vegetative balance and vascular tone.

Abstract 16026: Invasive Hemodynamic Assessment of Patients With Heart Failure With Preserved Ejection Fraction With Anemia and Iron Deficiency

Introduction: Anemia is associated with increased mortality, cardiovascular events, and decreased quality of life in patients with heart failure with preserved ejection fraction (HFpEF). Iron deficiency may contribute to disease severity independent of effects on red cell mass. The hemodynamic consequences of anemia and iron deficiency in HFpEF remain unclear. Methods: We analyzed a cohort of 313 consecutive subjects with HFpEF diagnosed by invasive hemodynamic assessment, and compared echocardiographic and hemodynamic characteristics of anemic versus non-anemic subjects. Anemia was defined as hemoglobin &lt;13 g/dL in men and &lt;12 g/dL in women. Iron deficiency was defined as ferritin &lt;100 ug/L. Results: Compared to patients without anemia, HFpEF patients with anemia displayed higher NT-proBNP, elevated pulmonary artery (PA) pressures at rest and at peak exercise, and lower oxygen consumption at peak exercise (Table). There was no difference in pulmonary capillary wedge pressure (PCWP). Patients with iron deficiency were more likely to be women. At rest, patients with iron deficiency displayed lower left ventricular (LV) mass, higher resting SVRI and lower cardiac index (CI), but there were not significant differences with exercise. Conclusions: Anemia in HFpEF is associated with greater evidence of congestion and more severe pulmonary hypertension, contributing to reduced exercise capacity. Iron deficiency in HFpEF is more common in women and associated with lower cardiac output at rest, but hemodynamics are otherwise similar. Further study is required to understand the mechanisms by which anemia and iron deficiency influence cardiac function and outcomes in HFpEF.

Transthoracic Echocardiographic Hemodynamic Assessment in Patients under Spinal Anesthesia in Lower Limb Surgery

Background: Spinal anesthesia is often associated with significant hypotension due to a sympathetic blockand can increase the risk of perioperative cardiac complications. Transthoracic echocardiography (TTE) is widely used throughout medicine as a clinical, diagnostic and research tool. Portability, accuracy, ease of use and a variety of training courses have encouraged its use. Aim: The present study was designed to evaluate the hemodynamic changes of spinal anesthesia by Transthoracic Echocardiography and test its efficacy as a monitoring tool in lower limb surgery. Methods: The study included50 patients, who were scheduled for lower limb surgery under spinal anesthesia. Two serial TTE studies were performed. One immediately before spinal anesthesia after giving the preload, then at 10 mins after spinal anesthesia. Changes of heart rate (HR), mean arterial blood pressure (MAP), the total doses of ephedrine and atropine, and data regarding highest sensory level and bromage scale were recorded. Results: Echocardiographic monitoring the heart variables have showed marked decrease when MAP was < 70% of basal values. Conclusion: Transthoracic echocardiography has proved its efficacy as a monitoring tool in assessment and guiding the management of hemodynamic changes after spinal anesthesia.

VP48.01: The role of non‐invasive hemodynamic assessment in patients with preterm premature rupture of the membranes

VP48.01: The role of non‐invasive hemodynamic assessment in patients with preterm premature rupture of the membranes

The haemodynamic assessment of patients with pulmonary arterial hypertension.

[No abstract. Showing first paragraph of article]Right heart catheterization (RHC) has a crucial role in the management of patients with pulmonary hypertension (PH). Firstly, it is mandatory in subjects with the suspicion of PH to confirm the diagnosis. Secondly, it is strongly recommended in the follow-up of patients with confirmed pulmonary arterial hypertension (PAH) to evaluate drug efficacy and in case of clinical deterioration.In order to always perform a complete and correct RHC, clinicians carrying out the examination must be guided not only by technical recommendations, but also by the accurate knowledge of the different clinical issues which have to be addressed in these different situations.

Study of common carotid and brachial artery hemodynamic variations in periodontal disease in Central India-a clinical study

Background and aimThe linkage between periodontal and systemic diseases although well researched in the scientific area is not universally cognizant among the clinicians. It is critical to bring about the awareness of this inter-relationship as oral health is suggestive of systemic health. The aim of this study was a thorough hemodynamic assessment in patients having periodontal disease. Settings and designThis is an observational cross sectional study. The patients were selected from Outpatient Department of Cardiology and Periodontology in a tertiary care hospital in urban setting in Nagpur, India. MethodsThe study was conducted on 45 patients aged between 35 and 65 years. Echo-Doppler examination for internal diameter (ID), intima-media thickness (IMT) and blood flow velocity (PSV) measurements was executed in the right and left common carotid artery (CCA) and brachial artery (BA). Periodontal disease status was determined using parameters like Gingival Index, Plaque Index, probing pocket depth (PPD) and clinical attachment level (CAL). Statistical analysisDue to multiple comparison groups one-way Analysis of variance (ANOVA) with Bonferroni multiple comparison tests have been performed to conduct all possible pair-wise comparisons of means. ResultsThe present study showed that Carotid IMT and ID were high in the patients having cardiovascular disease (CVD) and periodontitis as compared to CVD alone, showing the additional effect caused by the presence of periodontal disease. ConclusionThe study findings support the proposition that periodontal disease may be associated with endothelial dysfunction which leads to atherosclerosis or hardening of arteries indicating increased cardiovascular risk.

Exercise impedance cardiography reveals impaired hemodynamic responses to exercise in hypertensives with dyspnea.

Patients with arterial hypertension (AH), especially women, often report exercise intolerance and dyspnea. However, these symptoms are not frequently reflected in standard assessments. The aim of the study was to evaluate the clinical value of impedance cardiography (ICG) in the hemodynamic assessment of patients with AH during exercise, particularly the differences between subgroups based on sex and the presence of dyspnea. Ninety-eight patients with AH (52 women; 54.5 ± 8.2 years of age) were evaluated for levels of N-terminal pro-B-type brain natriuretic peptide (NT-proBNP), exercise capacity (cardiopulmonary exercise testing (CPET) and the 6-min walk test (6MWT)), and exercise ICG. Patients with AH were stratified into the following four subgroups: males without dyspnea (MnD, n = 38); males with dyspnea (MD, n = 8); females without dyspnea (FnD, n = 27); and females with dyspnea (FD, n = 25). In comparison with the MnD subgroup, the FnD subgroup demonstrated significantly higher NT-proBNP levels; lower exercise capacity (shorter 6MWT distance, lower peak oxygen uptake (VO2), lower O2 pulse); higher peak stroke volume index (SVI); and higher SVI at the anaerobic threshold (AT). In comparison with the other subgroups, the FD subgroup walked a shorter distance during the 6MWT distance; had a steeper VE/VCO2 slope; had lower values of peak stroke volume (SV) and peak cardiac output (CO); and had a smaller change in CO from rest to peak. However, no other differences were identified (NT-proBNP, left ventricular diastolic dysfunction, or CPET parameters). Exercise impedance cardiography revealed an impaired hemodynamic response to exercise in hypertensive females with dyspnea. In patients with unexplained exercise intolerance, impedance cardiography may complement traditional exercise tests.

Echocardiographic Predictors of Hemodynamics in Patients Supported With Left Ventricular Assist Devices

The assessment of hemodynamics in patients supported with left ventricular assist devices (LVADs) is often challenging. Physical examination maneuvers correlate poorly with true hemodynamics. We assessed the value of novel transthoracic echocardiography (TTE)-derived variables to reliably predict hemodynamics in patients supported with LVAD. A total of 102 Doppler-TTE images of the LVAD outflow cannula were obtained during simultaneous invasive right heart catheterization (RHC) in 30 patients supported with continuous-flow LVADs (22 HMII, 8 HVAD) either during routine RHC or during invasive ramp testing. Properties of the Doppler signal though the outflow cannula were measured at each ramp stage (RS), including the systolic slope (SS), diastolic slope (DS), and velocity time integral (VTI). Hemodynamic variables were concurrently recorded, including Doppler opening pressure (MAP), heart rate (HR), right atrial pressure, pulmonary artery pressure, pulmonary capillary wedge pressure (PCWP), Fick cardiac output (CO) and systemic vascular resistance (SVR). Univariate and multivariate regression analyses were used to explore the dependence of PCWP, CO, and SVR on DS, SS, VTI, MAP, HR, and RS. Multivariate linear regression analysis revealed significant contributions of DS on PCWP (PCWPpred = 0.164DS + 4.959; R = 0.68). Receiver operating characteristic (ROC) curve analysis revealed that PCWPpred could predict an elevated PCWP ≥18 mm Hg with a sensitivity (Sn) of 94% and specificity (Sp) of 85% (area under the ROC curve 0.88). CO could be predicted by RS, VTI, and HR (COpred = 0.017VTI + 0.016HR + 0.12RS + 2.042; R = 0.61). COpred could predict CO ≤4.5 L/min with Sn 73% and Sp 79% (AUC 0.81). SVR could be predicted by MAP, VTI, and HR (SVRpred = 15.44MAP - 5.453VTI - 6.349HR + 856.15; R = 0.84) with Sn 84% and Sp 79% (AUC 0.91) to predict SVR ≥1200 dyn-s/cm5. Doppler-TTE variables derived from the LVAD outflow cannula can reliably predict PCWP, CO, and SVR in patients supported with LVADs and may mitigate the need for invasive testing.