Coronary artery flow velocity is related to lumen area and regional left ventricular mass

Transthoracic ultrasound localization microscopy of myocardial vasculature in patients

Myocardial microvasculature and haemodynamics are indicative of potential microvascular diseases for patients with symptoms of coronary heart disease in the absence of obstructive coronary arteries. However, imaging microvascular structure and flow within the myocardium is challenging owing to the small size of the vessels and the constant movement of the patient's heart. Here we show the feasibility of transthoracic ultrasound localization microscopy for imaging myocardial microvasculature and haemodynamics in explanted pig hearts and in patients in vivo. Through a customized data-acquisition and processing pipeline with a cardiac phased-array probe, we leveraged motion correction and tracking to reconstruct the dynamics of microcirculation. For four patients, two of whom had impaired myocardial function, we obtained super-resolution images of myocardial vascular structure and flow using data acquired within a breath hold. Myocardial ultrasound localization microscopy may facilitate the understanding of myocardial microcirculation and the management of patients with cardiac microvascular diseases.

High Resting Coronary Flow Velocity by Echocardiography Is Associated With Worse Survival in Patients With Chronic Coronary Syndromes

BACKGROUND

Resting coronary flow velocity (CFV) in the mid-distal left anterior descending coronary artery can be easily assessed with transthoracic echocardiography. In this observational study, the authors sought to assess the relationship between resting CFV, CFV reserve (CFVR), and outcome in patients with chronic coronary syndromes.

METHODS AND RESULTS

In a prospective multicenter study design, the authors retrospectively analyzed 7576 patients (age, 66±11 years; 4312 men) with chronic coronary syndromes and left ventricular ejection fraction ≥50% referred for dipyridamole stress echocardiography. Recruitment (years 2003-2021) involved 7 accredited laboratories, with interobserver variability <10% for CFV measurement at study entry. Baseline peak diastolic CFV was obtained by pulsed-wave Doppler in the mid-distal left anterior descending coronary artery. CFVR (abnormal value ≤2.0) was assessed with dipyridamole. All-cause death was the only end point. The mean CFV of the left anterior descending coronary artery was 31±12 cm/s. The mean CFVR was 2.32±0.60. During a median follow-up of 5.9±4.3 years, 1121 (15%) patients died. At multivariable analysis, resting CFV ≥32 cm/s was identified by a receiver operating curve as the best cutoff and was independently associated with mortality (hazard ratio [HR], 1.24 [95% CI, 1.10-1.40]; P<0.0001) together with CFVR ≤2.0 (HR, 1.78 [95% CI, 1.57-2.02]; P<0.0001), age, diabetes, history of coronary surgery, and left ventricular ejection fraction. When both CFV and CFVR were considered, the mortality rate was highest in patients with resting CFV ≥32 cm/s and CFVR ≤2.0 and lowest in patients with resting CFV <32 cm/s and CFVR >2.0.

CONCLUSIONS

High resting CFV is associated with worse survival in patients with chronic coronary syndromes and left ventricular ejection fraction ≥50%. The value is independent and additive to CFVR. The combination of high resting CFV and low CFVR is associated with the worst survival.

Magnetically assisted soft milli-tools for occluded lumen morphology detection

Methodologies based on intravascular imaging have revolutionized the diagnosis and treatment of endovascular diseases. However, current methods are limited in detecting, i.e., visualizing and crossing, complicated occluded vessels. Therefore, we propose a miniature soft tool comprising a magnet-assisted active deformation segment (ADS) and a fluid drag-driven segment (FDS) to visualize and cross the occlusions with various morphologies. First, via soft-bodied deformation and interaction, the ADS could visualize the structure details of partial occlusions with features as small as 0.5 millimeters. Then, by leveraging the fluidic drag from the pulsatile flow, the FDS could automatically detect an entry point selectively from severe occlusions with complicated microchannels whose diameters are down to 0.2 millimeters. The functions have been validated in both biologically relevant phantoms and organs ex vivo. This soft tool could help enhance the efficacy of minimally invasive medicine for the diagnosis and treatment of occlusions in various circulatory systems.

The mechanisms of arterial signal intensity profile in non-contrast coronary MRA (NC-MRCA): a 3D printed phantom investigation and clinical translations

Signal intensity (SI) drop has been proposed as an indirect stenosis assessment in non-contrast coronary MRA (NC-MRCA) but it uses unproven assumptions. We aimed to clarify the mechanisms that govern the SI in vitro and develop a stenosis detection method in vivo. Flow phantom tubes with/without stenosis were scanned under two spatial resolutions (0.5/1.0 mm³) on a 3.0 T MRI. Thirty-two coronary arteries from 11 volunteers were prospectively scanned with an EKG- and respiratory-gated 3D NC-MRCA with a resolution of 1.0 mm³, with coronary computed tomography angiography (CTA) as reference. The normalized SI along the centerline of the tubes or the coronary arteries was assessed against the distance from the orifice using a linear regression model. Its coefficient (SI decay slope) and goodness-of-fit (R2) were extracted to assess the effect of flow velocity and stenosis on the SI profile curve. The R2 was utilized for the stenosis detection. Phantom study: A slow flow velocity caused a steep SI decay slope. The SI drop revealed only at the inlet and outlet of stenosis due to the flow turbulence/vortex and yielded low R2, in which shape changed by the resolution. Clinical study: The R2 cutoff to detect ≥ 50% stenosis for the left and right coronary arteries were 0.64 and 0.20 with a sensitivity/specificity of 71.5/71.5 and 66.7/100 (%), respectively. The SI drop did not reflect the actual stenosis position and not suitable for the stenosis localization. The R2 cutoff represents an alternative method to detect stenoses on NC-MRCA at vessel level.Trial registration: ClinicalTrials.gov; NCT03768999, registered on December 7, 2018.

M. P. Integrating particle tracking with computational fluid dynamics to assess haemodynamic perturbation by coronary artery stents

AIMS

Coronary artery stents have profound effects on arterial function by altering fluid flow mass transport and wall shear stress. We developed a new integrated methodology to analyse the effects of stents on mass transport and shear stress to inform the design of haemodynamically-favourable stents.

METHODS AND RESULTS

Stents were deployed in model vessels followed by tracking of fluorescent particles under flow. Parallel analyses involved high-resolution micro-computed tomography scanning followed by computational fluid dynamics simulations to assess wall shear stress distribution. Several stent designs were analysed to assess whether the workflow was robust for diverse strut geometries. Stents had striking effects on fluid flow streamlines, flow separation or funnelling, and the accumulation of particles at areas of complex geometry that were tightly coupled to stent shape. CFD analysis revealed that stents had a major influence on wall shear stress magnitude, direction and distribution and this was highly sensitive to geometry.

CONCLUSIONS

Integration of particle tracking with CFD allows assessment of fluid flow and shear stress in stented arteries in unprecedented detail. Deleterious flow perturbations, such as accumulation of particles at struts and non-physiological shear stress, were highly sensitive to individual stent geometry. Novel designs for stents should be tested for mass transport and shear stress which are important effectors of vascular health and repair.

Flush Flow Behaviour Affected by the Morphology of Intravascular Endoscope: A Numerical Simulation and Experimental Study

Background: Whilst intravascular endoscopy can be used to identify lesions and assess the deployment of endovascular devices, it requires temporary blockage of the local blood flow during observation, posing a serious risk of ischaemia. Objective: To aid the design of a novel flow-blockage-free intravascular endoscope, we explored changes in the haemodynamic behaviour of the flush flow with respect to the flow injection speed and the system design. Methods: We first constructed the computational models for three candidate endoscope designs (i.e., Model A, B, and C). Using each of the three endoscopes, flow patterns in the target vessels (straight, bent, and twisted) under three different sets of boundary conditions (i.e., injection speed of the flush flow and the background blood flowrate) were then resolved through use of computational fluid dynamics and in vitro flow experiments. The design of endoscope and its optimal operating condition were evaluated in terms of the volume fraction within the vascular segment of interest, as well as the percentage of high-volume-fraction area (PHVFA) corresponding to three cross-sectional planes distal to the microcatheter tip. Results: With a mild narrowing at the endoscope neck, Model B exhibited the highest PHVFA, irrespective of location of the cross-sectional plane, compared with Models A and C which, respectively, had no narrowing and a moderate narrowing. The greatest difference in the PHVFA between the three models was observed on the cross-sectional plane 2 mm distal to the tip of the microcatheter (Model B: 33% vs. Model A: 18%). The background blood flowrate was found to have a strong impact on the resulting volume fraction of the flush flow close to the vascular wall, with the greatest difference being 44% (Model A). Conclusion: We found that the haemodynamic performance of endoscope Model B outperformed that of Models A and C, as it generated a flush flow that occupied the largest volume within the vascular segment of interest, suggesting that the endoscope design with a diameter narrowing of 30% at the endoscope neck might yield images of a better quality.

Coronary Flow Assessment Using Accelerated 4D Flow MRI With Respiratory Motion Correction

Magnetic resonance imaging (MRI) can potentially be used for non-invasive screening of patients with stable angina pectoris to identify probable obstructive coronary artery disease. MRI-based coronary blood flow quantification has to date only been performed in a 2D fashion, limiting its clinical applicability. In this study, we propose a framework for coronary blood flow quantification using accelerated 4D flow MRI with respiratory motion correction and compressed sensing image reconstruction. We investigate its feasibility and repeatability in healthy subjects at rest. Fourteen healthy subjects received 8 times-accelerated 4D flow MRI covering the left coronary artery (LCA) with an isotropic spatial resolution of 1.0 mm³. Respiratory motion correction was performed based on 1) lung-liver navigator signal, 2) real-time monitoring of foot-head motion of the liver and LCA by a separate acquisition, and 3) rigid image registration to correct for anterior-posterior motion. Time-averaged diastolic LCA flow was determined, as well as time-averaged diastolic maximal velocity (V_MAX) and diastolic peak velocity (V_PEAK). 2D flow MRI scans of the LCA were acquired for reference. Scan-rescan repeatability and agreement between 4D flow MRI and 2D flow MRI were assessed in terms of concordance correlation coefficient (CCC) and coefficient of variation (CV). The protocol resulted in good visibility of the LCA in 11 out of 14 subjects (six female, five male, aged 28 ± 4 years). The other 3 subjects were excluded from analysis. Time-averaged diastolic LCA flow measured by 4D flow MRI was 1.30 ± 0.39 ml/s and demonstrated good scan-rescan repeatability (CCC/CV = 0.79/20.4%). Time-averaged diastolic V_MAX (17.2 ± 3.0 cm/s) and diastolic V_PEAK (24.4 ± 6.5 cm/s) demonstrated moderate repeatability (CCC/CV = 0.52/19.0% and 0.68/23.0%, respectively). 4D flow- and 2D flow-based diastolic LCA flow agreed well (CCC/CV = 0.75/20.1%). Agreement between 4D flow MRI and 2D flow MRI was moderate for both diastolic V_MAX and V_PEAK (CCC/CV = 0.68/20.3% and 0.53/27.0%, respectively). In conclusion, the proposed framework of accelerated 4D flow MRI equipped with respiratory motion correction and compressed sensing image reconstruction enables repeatable diastolic LCA flow quantification that agrees well with 2D flow MRI.

Branch flow distribution approach and its application in the calculation of fractional flow reserve in stenotic coronary artery

OBJECTIVE

To calculate fractional flow reserve (FFR) based on computed tomography angiography (i.e., FFRCT) by considering the branch flow distribution in the coronary arteries.

BACKGROUND

FFR is the gold standard to diagnose myocardial ischemia caused by coronary stenosis. An accurate and noninvasive method for obtaining total coronary blood flow is needed for the calculation of FFRCT.

METHODS

A mathematical model for estimating the coronary blood flow rate and two approaches for setting the patient-specific flow boundary condition were proposed. Coronary branch flow distribution methods based on a volume-flow approach and a diameter-flow approach were employed for the numerical simulation of FFRCT. The values of simulated FFRCT for 16 patients were compared with their clinically measured FFR.

RESULTS

The ratio of total coronary blood flow to cardiac output and the myocardial blood flow under the condition of hyperemia were 16.97% and 4.07 mL/min/g, respectively. The errors of FFRCT compared with clinical data under the volume-flow approach and diameter-flow approach were 10.47% and 11.76%, respectively, the diagnostic accuracies of FFRCT were 65% and 85%, and the consistencies were 95% and 90%.

CONCLUSIONS

The mathematical model for estimating the coronary blood flow rate and the coronary branch flow distribution method can be applied to calculate the value of clinical noninvasive FFRCT.

Numerical computation of blood hemodynamic through constricted human left coronary artery: Pulsatile simulations

BACKGROUND AND OBJECTIVE

The accumulation of plaque in the coronary artery of the human heart restricts the path of blood flow in that region and leads to Coronary Artery Disease. This study's goal is to present the pulsatile blood flow conduct through four different levels of constrictions, i.e., healthy, 25%, 50%, and 75% in human left coronary arteries.

METHODS

Using CT scan data of a healthy person, the two-dimensional coronary model is constructed. A non-Newtonian Carreau model is used to study the maximum flow velocity, streamline effect, and maximum Wall Shear Stress at the respective constricted areas over the entire cardiac cycle. Finite Volume Method is executed for solving the governing equations. The fluctuating Wall Shear Stress (WSS) at different levels was assessed using Computational Fluid Dynamics (CFD).

RESULTS

The comparative study of the diseased arteries showcases that at the systolic phase, the 75% blocked artery attains the maximum velocity of 0.14 m/s and 0.53 m/s at t=0.005 s and t=0.115 s, respectively. While the maximum velocity takes a significant drop at t=0.23 s and t=0.345 s, this marks the diastolic phase. The streamline contour showcased the blood flow conduct at different phases of the cardiac cycle. At the peak systolic phase, a dense flow separation was observed near the blocked regions. It highlights the disturbed flow in that particular region. The most severely diseased artery acquires the maximum WSS of 18.81 Pa at the peak systolic phase, i.e., at t=0.115 s.

CONCLUSIONS

The computational study of the hemodynamic parameters can aid in the early anticipation of the degree of the severity of the diseased arteries. This study, in a way, could benefit doctors/surgeons to plan an early treatment/surgery on the grounds of the severity of the disease. Thus, a before time prognosis could restrain the number of deaths caused due to Coronary Artery Disease.

Coronary vasomotion and exercise-induced adaptations in coronary artery disease patients: A systematic review and meta-analysis

Background:

Exercise can improve coronary blood flow in a healthy heart, but the vascular response of patients with coronary artery disease (CAD) is different. The aim of this study was to systematically review the chronic effects of exercise on coronary arterial function in CAD patients.

Materials and Methods:

Six electronic databases (PubMed, ScienceDirect, “Scopus,” Web of Science, EMBASE, and Google Scholar) covering publications from 1986 to 2019 were systematically searched with related keywords. Studies were included if they investigated changes in blood flow and coronary artery diameter in response to chronic exercise training in patients with CAD. A total of 5421 studies were assessed for quality and outcomes, and finally five studies met criteria for inclusion. For metaanalysis, the results of the studies were pooled using the randomeffects model. The heterogeneity between the studies was checked using I² index.

Results:

The total sample population consisted of 108 CAD patients. According to the findings of this study, coronary artery function in adaptation with exercise showed that a period of exercise leads to statistically significant improvement in coronary flow velocity reserve (z = 3.15, P = 0.002; standardized mean difference [SMD] =2.33, 95% confidence interval [CI]: 0.88–3.78) (containing six trials). In addition, vasodilatory response of coronary arteries in response to endothelium-independent vasodilator nitroglycerin was investigated in three studies (containing four trials). A meta-analysis showed that performing chronic aerobic exercises did not make a significant change in the endothelium-independent vasodilator (z = 0.83, P = 0.40; SMD = −0.36, 95% CI: −1.21–0.49).

Conclusion:

Based on the results of the present study, aerobic exercises improve the endothelial function of coronary arteries and thereby the vascular vasomotion function, while the results of this meta-analysis showed no change in arterial smooth muscle's function by chronic aerobic exercises. This study reflects the lack of high- and medium-quality reports about the chronic effects of anaerobic and resistance exercises and the various methods of aerobic exercise on cardiovascular function.

Impairment of coronary flow velocity reserve and global longitudinal strain in women with cardiac syndrome X and slow coronary flow

BACKGROUND

Microvascular dysfunction (MVD) is associated with adverse prognosis and may account for abnormal stress tests and angina symptoms in women with cardiac syndrome X (CSX). The aim of our study was to assess MVD by coronary flow velocity reserve (CFVR) and left ventricular (LV) contractile function by LV global longitudinal strain (LVGLS) in CSX patients with respect to presence of slow coronary flow (SCF). It was of additional importance to evaluate clinical status of CSX patients using Seattle Angina Questionnaire.

METHODS AND RESULTS

Study population included 70 women with CSX (mean age 61 ± 7 years) and 34 age-matched controls. CSX group was stratified into two subgroups depending on SCF presence: CSX-Thrombolysis In Myocardial Infarction (TIMI) 3- normal flow subgroup (n = 38) and CSX-TIMI 2- SCF subgroup (n = 32) as defined by coronary angiography. LVGLS measurements and CFVR of left anterior descending (LAD) and posterior descending (PD) artery were performed. CFVR-LAD and PD were markedly impaired in CSX group compared to controls (2.34 ± 0.25 vs 3.05 ± 0.21, p < 0.001; 2.32 ± 0.24 vs 3.01 ± 0.13, p < 0.001), and furthermore decreased in CSX-TIMI 2 patients. Resting, peak, and ΔLVGLS were all significantly impaired in CSX group compared to controls (for all p < 0.001), and furthermore reduced in CSX-TIMI 2 subgroup. Strongest correlation was found between peak LVGLS and CFVR LAD (r = -0.784, p < 0.001) and PD (r = -0.772, p < 0.001). CSX-TIMI 2 subgroup had more frequent angina symptoms and more impaired quality of life.

CONCLUSIONS

MVD in CSX patients is demonstrated by reduction in CFVR and LVGLS values. SCF implies more profound impairment of microvascular and LV systolic function along with worse clinical presentation.

Improved velocity-selective labeling pulses for myocardial ASL

PURPOSE

To develop and evaluate an improved velocity-selective (VS) labeling pulse for myocardial arterial spin labeling (ASL) perfusion imaging that addresses two limitations of current pulses: (1) spurious labeling of moving myocardium and (2) low labeling efficiency.

METHODS

The proposed myocardial VSASL labeling pulse is designed using a Fourier Transform based Velocity-Selective labeling pulse train. The pulse utilizes bipolar velocity-encoding gradients, a 9-tap velocity-encoding envelope, and double-refocusing pulses with Malcolm Levitt phase cycling. Amplitudes of the velocity-encoding envelope were optimized to minimize the labeling of myocardial velocities during stable diastole (±2-3 cm/s) and maximize the labeling of coronary velocities (10-130 cm/s during rest/stress or 10-70 cm/s during rest). Myocardial ASL experiments were performed in seven healthy subjects using the previously developed VS-ASL protocol by Jao et al with the two proposed VS pulses and original VS pulse. Myocardial ASL experiments were also performed using FAIR ASL. Myocardial perfusion and physiological noise (PN) were evaluated and compared.

RESULTS

Bloch simulations of the first and second proposed pulses show <2% labeling over ±3 cm/s and ±2 cm/s, respectively. Bloch simulations also show the mean labeling efficiency of arterial blood is 1.23 over the relevant coronary arterial ranges. In-vivo VSASL experiments show the proposed pulses provided comparable measurements to FAIR ASL and reduced TSNR in 5 of 7 subjects compared to the original VS pulse.

CONCLUSION

We demonstrate an improved VS labeling pulse specifically for myocardial ASL perfusion imaging to reduce spurious labeling of moving myocardium and PN.

Quantification of Myocardial Mass Subtended by a Coronary Stenosis Using Intracoronary Physiology

Background:

In patients with stable coronary artery disease, the amount of myocardium subtended by coronary stenoses constitutes a major determinant of prognosis, as well as of the benefit of coronary revascularization. We devised a novel method to estimate partial myocardial mass (PMM; ie, the amount of myocardium subtended by a stenosis) during physiological stenosis interrogation. Subsequently, we validated the index against equivalent PMM values derived from applying the Voronoi algorithm on coronary computed tomography angiography.

Methods:

Based on the myocardial metabolic demand and blood supply, PMM was calculated as follows: PMM (g)=APV×D 2 ×π/(1.24×10 − 3 ×HR×sBP+1.6), where APV indicates average peak blood flow velocity; D, vessel diameter; HR, heart rate; and sBP, systolic blood pressure. We calculated PMM to 43 coronary vessels (32 patients) interrogated with pressure and Doppler guidewires, and compared it with computed tomography–based PMM.

Results:

Median PMM was 15.8 g (Q1, Q3: 11.7, 28.4 g) for physiology-based PMM, and 17.0 g (Q1, Q3: 12.5, 25.9 g) for computed tomography–based PMM ( P =0.84). Spearman rank correlation coefficient was 0.916 ( P <0.001), and Passing-Bablok analysis revealed absence of both constant and proportional differences (coefficient A: −0.9; 95% CI, −4.5 to 0.9; and coefficient B, 1.00; 95% CI, 0.91 to 1.25]. Bland-Altman analysis documented a mean bias of 0.5 g (limit of agreement: −9.1 to 10.2 g).

Conclusions:

Physiology-based calculation of PMM in the catheterization laboratory is feasible and can be accurately performed as part of functional stenosis assessment.

Vasoconstrictor component of atherothrombotic culprit lesions in ST-segment elevation myocardial infarction

OBJECTIVE

The vasoconstrictor component of atherothrombotic culprit lesions in ST-elevation myocardial infarction (STEMI) patients has not been fully investigated. This study was aimed at assessing the vasoconstrictor component of atherothrombotic culprit lesions in patients with STEMI receiving primary percutaneous coronary intervention (PCI).

METHODS

A group of 100 patients with STEMI were enrolled prospectively. Baseline coronary angiography achieving normal antegrade flow was followed by 200 μg of intracoronary nitroglycerin (NTG) injection and repeat coronary angiography at the same projection view for culprit lesions was performed. End points were the changes in lesion length, reference vessel diameter, minimal lumen diameter, and diameter stenosis by quantitative coronary analysis before and after NTG injection.

RESULTS

Reference vessel diameter (2.7 ± 0.5 mm vs. 2.9 ± 0.5 mm, p < 0.001) and minimal lumen diameter (0.9 ± 0.4 mm vs. 1.2 ± 0.5 mm, p < 0.001) increased after NTG injection, whereas lesion length (24.1 ± 7.4 mm vs. 23.4 ± 7.6 mm, p = 0.001) and diameter stenosis (66.6 ± 14.8% vs. 58.3 ± 16.1%, p < 0.001) decreased. The median percentage change of diameter stenosis was -4.0% (Interquartile range: -13.8% to -1.0%), which was used as the cut-off value to divide the cohort into NTG responder or nonresponder groups accordingly. Total stent length was significantly shorter in the responder group compared with the nonresponder group (27.4 ± 11.6 mm vs. 33.7 ± 16.8 mm, p = 0.042).

CONCLUSION

This study showed the presence of a vasoconstrictor component in atherothrombotic culprit lesions in STEMI patients receiving primary PCI. Vasodilating effort by NTG may decrease stent length used for culprit lesions.

Regional Left Ventricular Myocardial Dysfunction After Cardiac Surgery Characterized by 3-Dimensional Strain

BACKGROUND

Three-dimensional (3D) strain is an echocardiographic modality that can characterize left ventricular (LV) function with greater accuracy than ejection fraction. While decreases in global strain have been used to predict outcomes after cardiac surgery, changes in regional 3D longitudinal, circumferential, radial, and area strain have not been well described. The primary aim of this study was to define differential patterns in regional LV dysfunction after cardiac surgery using 3D speckle tracking strain imaging. Our secondary aim was to investigate whether changes in regional strain can predict postoperative outcomes, including length of intensive care unit stay and 1-year event-free survival.

METHODS

In this prospective clinical study, demographic, operative, echocardiographic, and clinical outcome data were collected on 182 patients undergoing aortic valve replacement, mitral valve repair or replacement, coronary artery bypass graft, and combined cardiac surgery. Three-dimensional transthoracic echocardiograms were performed preoperatively and on the second to fourth postoperative day. Blinded analysis was performed for LV regional longitudinal, circumferential, radial, and area strain in the 17-segment model.

RESULTS

Regional 3D longitudinal, circumferential, radial, and area strains were associated with differential patterns of myocardial dysfunction, depending on the surgical procedure performed and strain measure. Patients undergoing mitral valve repair or replacement had reduced function in the majority of myocardial segments, followed by coronary artery bypass graft, while patients undergoing aortic valve replacement had reduced function localized only to apical segments. After all types of cardiac surgery, segmental function in apical segments was reduced to a greater extent as compared to basal segments. Greater decrements in regional function were seen in circumferential and area strain, while smaller decrements were observed in longitudinal strain in all surgical patients. Both preoperative regional strain and change in regional strain preoperatively to postoperatively were correlated with reduced 1-year event-free survival, while postoperative strain was not predictive of outcomes. Only preoperative strain values were predictive of intensive care unit length of stay.

CONCLUSIONS

Changes in regional myocardial function, measured by 3D strain, varied by surgical procedure and strain type. Differences in regional LV function, from presurgery to postsurgery, were associated with worsened 1-year event-free survival. These findings suggest that postoperative changes in myocardial function are heterogeneous in nature, depending on the surgical procedure, and that these changes may have long-term impacts on outcome. Therefore, 3D regional strain may be used to identify patients at risk for worsened postoperative outcomes, allowing early interventions to mitigate risk.

Impact of Subtended Myocardial Mass Assessed by Coronary Computed Tomographic Angiography-Based Myocardial Segmentation

Although decision-making for revascularization is based on the extent of ischemic myocardium, the prognostic implication of supplying myocardial territories has not yet been studied. To evaluate the clinical impact of the coronary artery-based myocardial segmentation (CAMS)-derived myocardial volume subtended to the poststenotic segment, and to determine clinically relevant coronary lesions, coronary computed tomography angiography, invasive coronary angiography, and preprocedure fractional flow reserve (FFR) data were analyzed in 664 deferred lesions (in 577 patients) and 401 treated lesions (in 369 patients) with drug-eluting stent implantation, respectively. Using CAMS method, the myocardial volume subtended to a stenotic coronary segment (V_sub) was assessed. The primary composites included target vessel-related major adverse cardiac event (MACE) including cardiac death, myocardial infarction, and target vessel revascularization over 3 years. Independent predictors of 3-year MACE in deferred lesions were V_sub (adjusted hazard ratio [HR] 1.02), FFR (adjusted HR per 0.1 = 0.60), and distal reference luminal diameter (adjusted HR 2.04, all p < 0.05). A V_sub ≥ 36.2cc was predictive of MACE in deferred lesions with a sensitivity 72% and a specificity 67% (area under curve 0.71, 95% confidence interval 0.67 to 0.74, p < 0.001). V_sub was not associated with target vessel-related MACE. For the prediction of FFR < 0.80, the area under curve of V_sub/MLD⁴ > 6.3 was greater than those of angiographic diameter stenosis (0.78 vs 0.69) and minimal luminal diameter (0.78 vs 0.71), (all p < 0.05). CAMS-derived V_sub predicted 3-year clinical outcomes in untreated coronary lesions, and improved the diagnostic performance of angiography-derived parameters to identify ischemia-producing lesions.

Comprehensive physiological evaluation of epicardial and microvascular coronary domains using vascular conductance and zero flow pressure

AIMS

Assessment of the coronary circulation has been based largely on pressure ratios (epicardial) and resistance (micro-vessels). Simultaneous assessment of epicardial (CEPI) and microvascular conductance (CMICRO) provides an intuitive approach using the same units for both coronary domains and expressing the actual deliverability of blood. The aim of this study was to develop a novel integral method for assessing the functional severity of epicardial and microvascular disease.

METHODS AND RESULTS

We performed intracoronary pressure and Doppler flow velocity measurements in 403 vessels in 261 patients with stable coronary artery disease. Hyperaemic mid-to-late diastolic pressure and flow velocity (PV) relationships were calculated. The slope of the aortic PV indicates the overall conductance and the slope of the distal PV relationship represents CMICRO. The intercept with the x-axis represents zero-flow pressure (Pzf). CEPI was derived from microvascular and overall conductance. Median CEPI was higher compared to CMICRO (4.2 [2.1-8.0] versus 1.3 [1.0-1.7] cm/s/mmHg, p<0.001). CMICRO was independent of stenosis severity (1.3 [1.0-1.7] in FFR ≤0.80 versus 1.4 [1.0-1.8] in FFR >0.8, p=0.797). ROC curves (using FFR and HSR concordant vessels as standard) demonstrated an excellent ability of CEPI to characterise significant stenoses (AUC 0.93). When CEPI<CMICRO, a decrease in flow velocity and coronary pressure (optimal cut-off value 0.97, AUC 0.90) was demonstrated.

CONCLUSIONS

A comprehensive assessment of separate CEPI and CMICRO was feasible. CEPI has a remarkable diagnostic efficiency to detect a clinically relevant stenosis. When CEPI<CMICRO, distal flow and pressure decrease steeply, indicating myocardial ischaemia. CMICRO can be used to explore the severity of microvascular disease.

Machine learning assessment of myocardial ischemia using angiography: Development and retrospective validation

BACKGROUND

Invasive fractional flow reserve (FFR) is a standard tool for identifying ischemia-producing coronary stenosis. However, in clinical practice, over 70% of treatment decisions still rely on visual estimation of angiographic stenosis, which has limited accuracy (about 60%-65%) for the prediction of FFR < 0.80. One of the reasons for the visual-functional mismatch is that myocardial ischemia can be affected by the supplied myocardial size, which is not always evident by coronary angiography. The aims of this study were to develop an angiography-based machine learning (ML) algorithm for predicting the supplied myocardial volume for a stenosis, as measured using coronary computed tomography angiography (CCTA), and then to build an angiography-based classifier for the lesions with an FFR < 0.80 versus ≥ 0.80.

METHODS AND FINDINGS

A retrospective study was conducted using data from 1,132 stable and unstable angina patients with 1,132 intermediate lesions who underwent invasive coronary angiography, FFR, and CCTA at the Asan Medical Center, Seoul, Korea, between 1 May 2012 and 30 November 2015. The mean age was 63 ± 10 years, 76% were men, and 72% of the patients presented with stable angina. Of these, 932 patients (assessed before 31 January 2015) constituted the training set for the algorithm, and 200 patients (assessed after 1 February 2015) served as a test cohort to validate its diagnostic performance. Additionally, external validation with 79 patients from two centers (CHA University, Seongnam, Korea, and Ajou University, Suwon, Korea) was conducted. After automatic contour calibration using the caliber of guiding catheter, quantitative coronary angiography was performed using the edge-detection algorithms (CAAS-5, Pie-Medical). Clinical information was provided by the Asan BiomedicaL Research Environment (ABLE) system. The CCTA-based myocardial segmentation (CAMS)-derived myocardial volume supplied by each vessel (right coronary artery [RCA], left anterior descending [LAD], left circumflex [LCX]) and the myocardial volume subtended to a stenotic segment (CAMS-%Vsub) were measured for labeling. The ML for (1) predicting vessel territories (CAMS-%LAD, CAMS-%LCX, and CAMS-%RCA) and CAMS-%Vsub and (2) identifying the lesions with an FFR < 0.80 was constructed. Angiography-based ML, employing a light gradient boosting machine (GBM), showed mean absolute errors (MAEs) of 5.42%, 8.57%, and 4.54% for predicting CAMS-%LAD, CAMS-%LCX, and CAMS-%RCA, respectively. The percent myocardial volumes predicted by ML were used to predict the CAMS-%Vsub. With 5-fold cross validation, the MAEs between ML-predicted percent myocardial volume subtended to a stenotic segment (ML-%Vsub) and CAMS-%Vsub were minimized by the elastic net (6.26% ± 0.55% for LAD, 5.79% ± 0.68% for LCX, and 2.95% ± 0.14% for RCA lesions). Using all attributes (age, sex, involved vessel segment, and angiographic features affecting the myocardial territory and stenosis degree), the ML classifiers (L2 penalized logistic regression, support vector machine, and random forest) predicted an FFR < 0.80 with an accuracy of approximately 80% (area under the curve [AUC] = 0.84-0.87, 95% confidence intervals 0.71-0.94) in the test set, which was greater than that of diameter stenosis (DS) > 53% (66%, AUC = 0.71, 95% confidence intervals 0.65-0.78). The external validation showed 84% accuracy (AUC = 0.89, 95% confidence intervals 0.83-0.95). The retrospective design, single ethnicity, and the lack of clinical outcomes may limit this prediction model's generalized application.

CONCLUSION

We found that angiography-based ML is useful to predict subtended myocardial territories and ischemia-producing lesions by mitigating the visual-functional mismatch between angiographic and FFR. Assessment of clinical utility requires further validation in a large, prospective cohort study.

Impact of left ventricular remodelling patterns on outcomes in patients with aortic stenosis

Aims

The objective of this study was to examine the association between the different patterns of left ventricular (LV) remodelling/hypertrophy on all-cause and cardiovascular mortality in patients with aortic stenosis (AS).

Methods and results

In total, 747 consecutive patients (69 ± 14 years, 57% men) with AS and preserved LV ejection fraction were included in this study. According to LV mass index and relative wall thickness, patients were classified into four LV patterns: normal, concentric remodelling (CR), concentric hypertrophy (CH), and eccentric hypertrophy (EH). One hundred and sixteen patients (15%) had normal pattern, 66 (9%) had EH, 169 (23%) had CR, and 396 (53%) had CH. During a median follow-up of 6.4 years, 339 patients died (242 from cardiovascular causes). CH was associated with higher risk of all-cause mortality compared with the three other LV patterns (all P < 0.05). After multivariable adjustment, CH remained associated with higher risk of mortality (HR = 1.27, 95% CI 1.01-1.61, P = 0.046). There was a significant interaction (P < 0.05) between sex and CH with regards to the impact on mortality: CH was associated with worse outcome in women (P = 0.0001) but not in men (P = 0.22). In multivariable analysis, CH remained associated with higher risk of worse outcome in women (HR = 1.56, 95% CI 1.08-2.24, P = 0.018).

Conclusions

This study shows that CH was independently associated with increased risk of mortality in AS patients with preserved ejection fraction. This association was observed in women but not in men. The pattern of LV remodelling/hypertrophy should be integrated in the risk stratification process in patients with AS.

Non-invasive coronary physiology based on computational analysis of intracoronary transluminal attenuation gradient

Invasive procedure is a prerequisite for studying coronary physiology. We established the measurement of non-invasive physiological parameters including coronary blood flow (CBF), flow velocity, and microvascular resistance using coronary computed tomography angiography (CCTA). Vessel-specific CBF was derived from transluminal attenuation flow encoding (TAFE) and then tested using three separate datasets consisted of computational simulation, human perfusion CT, and human CCTA. TAFE-derived CBF correlated well with measured vessel-specific myocardial blood flow and CBF. TAFE-derived CBF per myocardial mass consistently decreased with the progressive severity of stenosis, and it was found to better to detect significant stenosis than transluminal attenuation gradient (TAG). With the addition of vessel anatomy, TAFE-derived CBF could calculate flow velocity and microvascular resistance. The results of non-invasively acquired parameters according to the severity of stenosis were similar to those obtained through invasive physiology studies. Our study demonstrated that non-invasive comprehensive coronary physiology parameters can be derived from CCTA without any pre-specified condition or performing complex heavy computational processes. Our findings are expected to expand the clinical coverage of CCTA and coronary physiology.

Demonstration of velocity selective myocardial arterial spin labeling perfusion imaging in humans

PURPOSE

Transit delay is a potential source of error in cardiac arterial spin-labeled (ASL) in heart failure or with collateral circulation. This study demonstrates the feasibility of using transit delay insensitive velocity selective ASL and compares its performance with flow-sensitive alternating inversion recovery (FAIR) ASL.

METHODS

Velocity selective labeling was achieved using an adiabatic BIR8 preparation. FAIR and velocity-selective ASL (VSASL) with various velocity cutoffs (V_C  = 10-40 cm/s) and labeling directions (anterior-posterior X, lateral-septal Y, and apical-basal Z) were carried out in 10 healthy volunteers (1F/9M age 23-30 y). Myocardial blood flow (MBF) and temporal signal-to-noise (TSNR) were measured.

RESULTS

VSASL sensitivity to perfusion decreased with increasing V_C . At low V_C (<5 cm/s), spurious labeling of myocardium occurs and overestimates MBF. MBF measured with FAIR (1.12 ± 0.26 ml/g/min) and VASL (1.26 ± 0.27 ml/g/min) at V_C of 10 cm/s in Z were comparable (TOST with difference of 0.30 ml/g/min, P = 0.049). TSNR was 2.8 times larger using FAIR (13.62 ± 5.25) than in VSASL (4.87 ± 1.58). VSASL was insensitive to perfusion in the Y direction. X and Z performed similarly with TSNR of 4.17 ± 2.32 and 3.97 ± 0.56, respectively.

CONCLUSION

VSASL is a promising alternative to FAIR ASL in the heart and is well suited for scenarios when transit delays are long. Magn Reson Med 80:272-278, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Outcomes after a left anterior descending artery endarterectomy in advanced coronary artery disease

BACKGROUND

Coronary endarterectomy albeit infrequently utilized remains a pivotal treatment modality for advanced atherosclerotic heart disease. Benefits of coronary endarterectomy are explored in terms of better mid-term survival, freedom of major adverse cardiac and cerebrovascular events and improved left ventricular ejection fraction.

METHODS

50 patients with coronary artery disease including extensive diffuse LAD disease underwent a left anterior descending artery endarterectomy with coronary by-pass grafting and left internal mammary artery as conduit between 2006 and 2014. Prospective evaluation was performed on an outpatient basis with physical examination, echo recordings of ejection fraction and LAD flow reserve for 24 up to 60months.

RESULTS

Study group was constituted by a male to female ratio 4:1 and mean age 62.4years old. Pre-operative characteristics included patients with age<60years old and gensini score>60 in 42.1% while patients with age>60years old had gensini score (21-60) in 63.4%. Furthermore, males were affected more severely by atherosclerosis than females. Postoperative anterior wall contractility of left ventricle was improved (56% pre-op vs. 66% post-op) and hypokinesis reduced (34% pre-op vs. 24% post-op). No deaths were recorded for a mean follow-up of 48months. Also, MACCE were recorded in 8% patients. Post-operative LAD flow reserve was normal in 66% and reduced in 33% of cases. Finally, gensini score preoperatively affects mid-term flow reserve postoperatively (p<0.05).

CONCLUSION

Coronary endarterectomy presents a viable modality that preserves myocardial function and restores LAD flow in patients with diffuse atherosclerotic LAD. Also postoperative adverse effects were minimal while mid-term flow reserve was affected by preoperative factors.

The Romhilt-Estes electrocardiographic score predicts sudden cardiac arrest independent of left ventricular mass and ejection fraction

BACKGROUND

The Romhilt-Estes point score system (RE) is an established ECG criterion for diagnosing left ventricular hypertrophy (LVH). In this study, we assessed for the first time, whether RE and its components are predictive of sudden cardiac arrest (SCA) independent of left ventricular (LV) mass.

METHODS

Sudden cardiac arrest (SCA) cases occurring between 2002 and 2014 in a Northwestern US metro region (catchment area approx. 1 million) were compared to geographic controls. ECGs and echocardiograms performed prior to the SCA and those of controls were acquired from the medical records and evaluated for the ECG criteria established in the RE score and for LV mass.

RESULTS

Two hundred forty-seven SCA cases (age 68.3 ± 14.6, male 64.4%) and 330 controls (age 67.4 ± 11.5, male 63.6) were included in the analysis. RE scores were greater in cases than controls (2.5 ± 2.1 vs. 1.9 ± 1.7, p < .001), and SCA cases were more likely to meet definite LVH criteria (18.6% vs. 7.9%, p < .001). In a multivariable model including echocardiographic LVH and LV function, definite LVH remained independently predictive of SCA (OR 2.04, 95% CI 1.16-3.59, p = .013). The model was replicated with the individual ECG criteria, and only SV_1.2  ≥ 30 mm and delayed intrinsicoid deflection remained significant predictors of SCA.

CONCLUSION

Left ventricular hypertrophy (LVH) as defined by the RE point score system is associated with SCA independent of echocardiographic LVH and reduced LV ejection fraction. These findings support an independent role for purely electrical LVH, in the genesis of lethal ventricular arrhythmias.

Effects of nitroglycerine on coronary flow velocity before and during adenosine provocation

BACKGROUND

Transthoracic echocardiography-assessed coronary flow velocity reserve (CFVR) evaluates coronary microvascular arterial function. Coronary flow velocity measurements at baseline and during hyperemia are used to calculate CFVR. Adenosine infusion induces hyperemia but it is not known if it causes a maximal response. We hypothesized that pre-treatment with nitroglycerine before adenosine provocation enhances hyperemia.

METHODS

Twenty-three healthy study subjects (mean age 27.5 ± 5.5, 35% women) underwent CFVR measurements before and after pretreatment with sublingual nitroglycerine (0.5 mg). Hyperemia was induced by adenosine infusion (140 μg/kg/min). In addition, the effect of nitroglycerin on left main coronary artery diameter was assessed.

RESULTS

Pretreatment with nitroglycerine increased median CFVR from 3.6 (range 2.8-4.3) to 5.0 (4.1-6.0), p = 0.002. The increase was caused by a marked reduction in baseline coronary flow velocity 17 (15-24) vs 27 (19-31) cm/s, p < 0.0001) while hyperemic velocity remained unchanged (90 (68-116) vs 93 (75-105) cm/s, p = 0.48). Nitroglycerin significantly dilated the left main coronary artery (from median 3.1 (2.7-3.6) mm to 3.8 (3.1-4.3) mm, p = 0.018).

CONCLUSION

Pretreatment with nitroglycerine dilates coronary arteries and increases coronary flow velocity reserve indicating that adenosine alone causes a submaximal hyperemia.

Overcoming spatio-temporal limitations using dynamically scaled in vitro PC-MRI - A flow field comparison to true-scale computer simulations of idealized, stented and patient-specific left main bifurcations

The majority of patients with angina or heart failure have coronary artery disease. Left main bifurcations are particularly susceptible to pathological narrowing. Flow is a major factor of atheroma development, but limitations in imaging technology such as spatio-temporal resolution, signal-to-noise ratio (SNRv), and imaging artefacts prevent in vivo investigations. Computational fluid dynamics (CFD) modelling is a common numerical approach to study flow, but it requires a cautious and rigorous application for meaningful results. Left main bifurcation angles of 40°, 80° and 110° were found to represent the spread of an atlas based 100 computed tomography angiograms. Three left mains with these bifurcation angles were reconstructed with 1) idealized, 2) stented, and 3) patient-specific geometry. These were then approximately 7× scaled-up and 3D printing as large phantoms. Their flow was reproduced using a blood-analogous, dynamically scaled steady flow circuit, enabling in vitro phase-contrast magnetic resonance (PC-MRI) measurements. After threshold segmentation the image data was registered to true-scale CFD of the same coronary geometry using a coherent point drift algorithm, yielding a small covariance error (σ² <;5.8×10^-4). Natural-neighbour interpolation of the CFD data onto the PC-MRI grid enabled direct flow field comparison, showing very good agreement in magnitude (error 2-12%) and directional changes (r² 0.87-0.91), and stent induced flow alternations were measureable for the first time. PC-MRI over-estimated velocities close to the wall, possibly due to partial voluming. Bifurcation shape determined the development of slow flow regions, which created lower SNRv regions and increased discrepancies. These can likely be minimised in future by testing different similarity parameters to reduce acquisition error and improve correlation further. It was demonstrated that in vitro large phantom acquisition correlates to true-scale coronary flow simulations when dynamically scaled, and thus can overcome current PC-MRI's spatio-temporal limitations. This novel method enables experimental assessment of stent induced flow alternations, and in future may elevate CFD coronary flow simulations by providing sophisticated boundary conditions, and enable investigations of stenosis phantoms.

Mathematically Derived Criteria for Detecting Functionally Significant Stenoses Using Coronary Computed Tomographic Angiography-Based Myocardial Segmentation and Intravascular Ultrasound-Measured Minimal Lumen Area

The lack of practical method for quantifying myocardial territories has made it difficult to link anatomic lesion morphology to the hemodynamic significance of coronary artery stenosis. The aim of this study was to develop and validate mathematically derived morphologic criteria for predicting fractional flow reserve (FFR) <0.80 using intravascular ultrasound (IVUS) parameters and a coronary artery-based myocardial segmentation (CAMS) of the affected myocardial territory. Coronary computed tomography angiography, IVUS, and FFR data were analyzed in 103 non-left main intermediate coronary artery lesions (30% to 80% of angiographic stenosis). Using CAMS method, the total left ventricular myocardial volume and the myocardial volume subtended by a stenotic coronary segment (Vsub) were assessed. The morphologic criteria for detecting an FFR <0.80 using the IVUS and CAMS parameters were mathematically derived. Overall, an IVUS-measured minimal lumen area (MLA) <2.79 mm(2) predicted an FFR <0.80 with sensitivity of 76%, specificity of 78%, positive predictive value of 71%, and negative predictive value of 82%. A Vsub/MLA(2) >4.04 best predicted an FFR <0.80 (sensitivity 88%, specificity 90%, positive predictive value 86%, and negative predictive value 92%, area under curve = 0.944). There was a significant difference in the areas under the curves between IVUS-MLA versus Vsub/MLA(2) (difference = 0.068, p = 0.005). Conversely, adjusting for body or vessel size did not improve the diagnostic accuracy.

Vasotonic Angina as a Cause of Myocardial Ischemia in Women

The frequency, presentation, prognosis, and treatment of myocardial ischemia differ in men and women. A large proportion of women who have "normal" coronary arteries on angiography without any significant evidence of flow-limiting disease also have biochemical or imaging evidence of myocardial ischemia. In these women it is believed to be a dysfunction of coronary microcirculation and/or macrocirculation, or vasotonic angina (VA), that leads to abnormal vasoconstriction, and potentially to myocardial infarction, ventricular arrhythmias, and sudden death. Despite having a "normal" or near normal coronary angiography, these women should therefore undergo additional testing with acetylcholine to assess endothelial function. Long-term survival is believed to be relatively good. Predictors of poorer prognosis include documentation of severe endothelial dysfunction and presence of concurrent angiographycally visible coronary atherosclerosis. Because atherosclerosis is common in patients with VA, medical and lifestyle interventions for preventing or treating atherosclerosis should be implemented when appropriate. Angiotensin converting enzyme inhibitors are the mainstays of medical therapy for VA. Other agents have been tried with variable success, including beta-blockers. There are no available data on any specific treatment of VA in women (versus men).

Dynamically scaled phantom phase contrast MRI compared to true-scale computational modeling of coronary artery flow

PURPOSE

To examine the feasibility of combining computational fluid dynamics (CFD) and dynamically scaled phantom phase-contrast magnetic resonance imaging (PC-MRI) for coronary flow assessment.

MATERIALS AND METHODS

Left main coronary bifurcations segmented from computed tomography with bifurcation angles of 33°, 68°, and 117° were scaled-up ∼7× and 3D printed. Steady coronary flow was reproduced in these phantoms using the principle of dynamic similarity to preserve the true-scale Reynolds number, using blood analog fluid and a pump circuit in a 3T MRI scanner. After PC-MRI acquisition, the data were segmented and coregistered to CFD simulations of identical, but true-scale geometries. Velocities at the inlet region were extracted from the PC-MRI to define the CFD inlet boundary condition.

RESULTS

The PC-MRI and CFD flow data agreed well, and comparison showed: 1) small velocity magnitude discrepancies (2-8%); 2) with a Spearman's rank correlation ≥0.72; and 3) a velocity vector correlation (including direction) of r(2) ≥ 0.82. The highest agreement was achieved for high velocity regions with discrepancies being located in slow or recirculating zones with low MRI signal-to-noise ratio (SNRv ) in tortuous segments and large bifurcating vessels.

CONCLUSION

Characterization of coronary flow using a dynamically scaled PC-MRI phantom flow is feasible and provides higher resolution than current in vivo or true-scale in vitro methods, and may be used to provide boundary conditions for true-scale CFD simulations. J. MAGN. RESON. IMAGING 2016;44:983-992.

Left ventricular hypertrophy with strain and aortic stenosis

BACKGROUND

ECG left ventricular hypertrophy with strain is associated with an adverse prognosis in aortic stenosis. We investigated the mechanisms and outcomes associated with ECG strain.

METHODS AND RESULTS

One hundred and two patients (age, 70 years [range, 63-75 years]; male, 66%; aortic valve area, 0.9 cm(2) [range, 0.7-1.2 cm(2)]) underwent ECG, echocardiography, and cardiovascular magnetic resonance. They made up the mechanism cohort. Myocardial fibrosis was determined with late gadolinium enhancement (replacement fibrosis) and T1 mapping (diffuse fibrosis). The relationship between ECG strain and cardiovascular magnetic resonance was then assessed in an external validation cohort (n=64). The outcome cohort was made up of 140 patients from the Scottish Aortic Stenosis and Lipid Lowering Trial Impact on Regression (SALTIRE) study and was followed up for 10.6 years (1254 patient-years). Compared with those without left ventricular hypertrophy (n=51) and left ventricular hypertrophy without ECG strain (n=30), patients with ECG strain (n=21) had more severe aortic stenosis, increased left ventricular mass index, more myocardial injury (high-sensitivity plasma cardiac troponin I concentration, 4.3 ng/L [interquartile range, 2.5-7.3 ng/L] versus 7.3 ng/L [interquartile range, 3.2-20.8 ng/L] versus 18.6 ng/L [interquartile range, 9.0-45.2 ng/L], respectively; P<0.001) and increased diffuse fibrosis (extracellular volume fraction, 27.4±2.2% versus 27.2±2.9% versus 30.9±1.9%, respectively; P<0.001). All patients with ECG strain had midwall late gadolinium enhancement (positive and negative predictive values of 100% and 86%, respectively). Indeed, late gadolinium enhancement was independently associated with ECG strain (odds ratio, 1.73; 95% confidence interval, 1.08-2.77; P=0.02), a finding confirmed in the validation cohort. In the outcome cohort, ECG strain was an independent predictor of aortic valve replacement or cardiovascular death (hazard ratio, 2.67; 95% confidence interval, 1.35-5.27; P<0.01).

CONCLUSION

ECG strain is a specific marker of midwall myocardial fibrosis and predicts adverse clinical outcomes in aortic stenosis.

A framework for personalization of coronary flow computations during rest and hyperemia

We introduce a Computational Fluid Dynamics (CFD) based method for performing patient-specific coronary hemodynamic computations under two conditions: at rest and during drug-induced hyperemia. The proposed method is based on a novel estimation procedure for determining the boundary conditions from non-invasively acquired patient data at rest. A multi-variable feedback control framework ensures that the computed mean arterial pressure and the flow distribution matches the estimated values for an individual patient during the rest state. The boundary conditions at hyperemia are derived from the respective rest-state values via a transfer function that models the vasodilation phenomenon. Simulations are performed on a coronary tree where a 65% diameter stenosis is introduced in the left anterior descending (LAD) artery, with the boundary conditions estimated using the proposed method. The results demonstrate that the estimation of the hyperemic resistances is crucial in order to obtain accurate values for pressure and flow rates. Results from an exhaustive sensitivity analysis have been presented for analyzing the variability of trans-stenotic pressure drop and Fractional Flow Reserve (FFR) values with respect to various measurements and assumptions.

Relation of distribution of coronary blood flow volume to coronary artery dominance

Coronary artery dominance influences the amount and anatomic location of myocardium that is perfused by the left or right coronary circulation. However, it is unknown whether coronary artery dominance also influences the distribution of coronary blood flow volume. The aim of this study was to evaluate volumetric coronary blood flow in 1,322 vessels from 496 patients in the Prediction of Progression of Coronary Artery Disease and Clinical Outcomes Using Vascular Profiling of Endothelial Shear Stress and Arterial Wall Morphology (PREDICTION) study. Patients were divided into 2 groups (right-dominant and left-dominant or balanced circulation). Coronary blood flow volume was calculated by coronary segment volume measurement using angiography and intravascular ultrasound and the contrast transit time through the segment. Coronary blood flow in the left circumflex coronary artery was significantly higher in left-dominant or balanced circulation than in right-dominant circulation (113 ± 43 vs 72 ± 37 ml/min, p <0.001), whereas flow in the right coronary artery was significantly lower in left-dominant or balanced circulation than in right-dominant circulation (56 ± 40 vs 113 ± 49 ml/min, p = 0.003). There was no significant difference in the left anterior descending coronary artery. In conclusion, coronary artery dominance has an impact on coronary blood flow volume in the left circumflex and right coronary arteries but not in the left anterior descending coronary artery. These findings suggest that the extent of myocardial perfusion area is associated with coronary blood flow volume.

Impaired coronary flow reserve after a recent myocardial infarction: correlation with infarct size and extent of microvascular obstruction

BACKGROUND

The exact relationship between the coronary flow reserve (CFR) and infarct size remains unknown. In this prospective study the relationship between the CFR both in the infarcted and remote myocardium and infarct size was investigated. Furthermore, the diagnostic value of the CFR to predict the extent of microvascular obstruction (MO) was evaluated.

METHODS

In thirty patients the CFR was measured with a Doppler guide wire 6 ± 3 days after a first myocardial infarction (MI) in the infarct related and in a reference coronary artery. MO and infarct size were determined with magnetic resonance imaging.

RESULTS

The CFR was inversely related to infarct size in the infarcted and remote myocardium (respectively, r=-0.60, p<0.01 and r=-0.62, p<0.01). In the infarcted myocardium the extent of MO was strongly related to the infarct size and was in a multivariate analysis the single significant determinant of the CFR and the hyperaemic flow. In the remote myocardium no relationship was present between infarct size and hyperaemic flow, but the baseline flow increased as the infarct size became larger (r=0.58, p<0.01). In a receiver operator characteristic (ROC) analysis, a CFR value ≤ 2 in the infarct related coronary artery offered the best sensitivity (65%) and specificity (71%) to detect the presence of MO (p<0.05).

CONCLUSIONS

After MI, the CFR both in the infarcted and remote myocardium is inversely related to infarct size. In the infarcted myocardium, a CFR value ≤ 2 predicts the presence of MO with moderate sensitivity and specificity.

Clinical implications of electrocardiographic left ventricular strain and hypertrophy in asymptomatic patients with aortic stenosis: the Simvastatin and Ezetimibe in Aortic Stenosis study

BACKGROUND

The prognostic impact of ECG left ventricular strain and left ventricular hypertrophy (LVH) in asymptomatic aortic stenosis is not well described.

METHODS AND RESULTS

Data were obtained in asymptomatic patients randomized to simvastatin/ezetimibe combination versus placebo in the Simvastatin and Ezetimibe in Aortic Stenosis (SEAS) study. Primary end point was the first of myocardial infarction, nonhemorrhagic stroke, heart failure, aortic valve replacement, or cardiovascular death. The predictive value of ECG left ventricular strain (defined as T-wave inversion in leads V(4) through V(6)) and LVH, assessed by Sokolow-Lyon voltage criteria (R(V5-6)+S(V1) ≥35 mV) and Cornell voltage-duration criteria {[RaVL+S(V3)+(6 mV in women)]×QRS duration ≥2440 mV · ms}, was evaluated by adjustment for other prognostic covariates. A total of 1533 patients were followed for 4.3±0.8 years (6592 patient-years of follow-up), and 627 cardiovascular events occurred. ECG strain was present in 340 patients (23.6%), with LVH by Sokolow-Lyon voltage in 260 (17.1%) and by Cornell voltage-duration product in 220 (14.6%). In multivariable analyses, ECG left ventricular strain was associated with 3.1-fold higher risk of in-study myocardial infarction (95% confidence interval, 1.4-6.8; P=0.004). Similarly, ECG LVH by both criteria predicted, compared with no ECG LVH, 5.8-fold higher risk of heart failure (95% confidence interval, 2.0-16.8), 2.0-fold higher risk of aortic valve replacement (95% confidence interval, 1.3-3.1; both P=0.001), and 2.5-fold higher risk of a combined end point of myocardial infarction, heart failure, or cardiovascular death (95% confidence interval, 1.3-4.9; P=0.008).

CONCLUSIONS

ECG left ventricular strain and LVH were independently predictive of poor prognosis in patients with asymptomatic aortic stenosis.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov. Unique identifier: NCT00092677.

Ischemic heart disease in women: a review for primary care physicians

Ischemic heart disease (IHD) is the leading cause of death among women in the Western world, and its prevalence is growing. The pathophysiology of heart disease in women differs from that in men. Women with chest pain and abnormal stress tests are less likely than men to have critical stenosis of coronary arteries, a phenomenon attributed to endothelial dysfunction. Hypertension, intimal injury, and cholesterol are among the various factors that contribute to endothelial dysfunction. The presenting symptoms of IHD also differ in women. Women are more likely to describe neck and throat pain and to characterize the pain as intense, sharp, or burning. A history of coronary or other vascular disease, diabetes, or chronic kidney disease places patients at high risk for IHD. Risk factor modification can be tailored based on each patient's risk. Hormone replacement therapy, antioxidants, folic acid, and aspirin in healthy women under 65 years of age have recently been shown to be ineffective in the prevention of IHD.

Nonobstructive coronary artery disease as detected by 64-detector row cardiac computed tomographic angiography is associated with increased left ventricular mass

BACKGROUND

Cardiac computed tomographic angiography (CCTA) permits simultaneous assessment of coronary artery disease (CAD) and left ventricular mass (LVM). While increased LVM predicts mortality and is associated with obstructive CAD, the relationship of LVM with non-obstructive CAD is unknown.

METHODS

We evaluated 212 consecutive patients undergoing 64-detector row CCTA at 2 sites without evident cardiovascular disease or obstructive (≥70%) CAD by CCTA. LVM was measured by CCTA using Simpson's method of disks and indexed to body surface area (LVMI) and height to the allometric power of 2.7(LVM/ht2.7). CCTAs were evaluated by scoring a modified AHA 16-segment coronary artery model for none = 0 (0% stenosis), mild = 1 (1-49% stenosis) or moderate = 2 (50-69% stenosis). Overall CAD plaque burden was estimated by summing scores across all segments for a segment stenosis score (SSS, max = 32).

RESULTS

The mean age was 53.3 ± 12.8 with 52% female, 48% hypertensive, and 7.4% diabetic. The mean LVM was 109 ± 32.5 g; 58.5% had any coronary artery plaque. In multivariable linear regression, SSS was significantly associated with increased LVM, LVMI and LVM/ht2.7. LVM increased by 2.0 g for every 1-point increase in SSS (95% CI 0.06-3.4, p = 0.006). Agatston scores provided no additional predictive value for increased LVM above and beyond SSS.

CONCLUSION

Non-obstructive CAD visualized by CCTA is associated with increased LVM independent of effects of clinical risk factors and calcium scoring. Whether addition of LVM to stenosis assessment in patients undergoing CCTA enhances risk prediction of future CAD events warrants investigation.

Electrocardiographic strain pattern in children with left ventricular hypertrophy: a marker of ventricular dysfunction

The objective of this study was to assess the relation between strain pattern on electrocardiogram (ECG-strain) and echocardiographic indices of left ventricular (LV) structure and function in children with LV hypertrophy (LVH). ECG-strain is a marker of LVH and is associated with adverse cardiovascular prognosis in adults. The significance of ECG-strain and its relation to LV structure and function has not been studied in children. We retrospectively analyzed electrocardiograms (ECGs) and echocardiograms of 101 children enrolled in this study. Subjects were divided into three groups: group I (n = 21) comprised children with LVH confirmed by echocardiography (LVH(echo)) with ECG-strain pattern; group II (n = 54) comprised children with LVH(echo) without ECG-strain pattern; and group III (n = 26) comprised children without LVH (control group). ECG-strain was defined as a down-sloping convex ST-segment depression (> or = 0.1 mV) with an inverted asymmetrical T-wave opposite to the QRS axis in leads V5 and/or V6. LV structure and function was measured using conventional and tissue Doppler echocardiography. ECG-strain was associated with greater interventricular septal thickness, posterior wall thickness, and LV mass index (LVMI) compared with those without ECG-strain (P < 0.0001 for each variable). Concentric LVH was more common in those with ECG-strain (16 of 21 vs. 9 of 54 patients; P = < 0.0001). ECG-strain was associated with systolic, diastolic, and combined systolic-diastolic dysfunction in children with LVH(echo). Among children with LVH, ECG-strain is associated with higher LVMI, concentric pattern of LVH, and LV systolic and diastolic dysfunction. Whether this has similar adverse prognostic implications as it does in adults remains to be determined.

Assessment of microcirculatory remodeling with intracoronary flow velocity and pressure measurements: validation with endomyocardial sampling in cardiac allografts

BACKGROUND

Intracoronary physiology techniques have been validated extensively for the assessment of epicardial stenoses but not for the lone study of coronary microcirculation. We performed a comparison between 4 intracoronary physiological indices with the actual structural microcirculatory changes documented in transplanted hearts.

METHODS AND RESULTS

In 17 cardiac allograft patients without coronary stenoses, ECG, intracoronary Doppler flow velocity, and aortic pressure were digitally recorded before and during maximal hyperemia with a dedicated system. Postprocessing of data yielded 4 indices of microcirculatory status: coronary flow velocity reserve (2.13+/-0.59), instantaneous hyperemic diastolic velocity pressure slope (2.33+/-1.25 cm x s x (-1)mm Hg(-1)), coronary resistance index (1.65+/-0.88 mm Hg x cm(-1) x s(-1)), and coronary resistance reserve (2.36+/-0.65). Quantitative morphometry was performed in endomyocardial biopsies during the same hospital intake; arteriolar obliteration (76.57+/-6.95%) and density (2.00+/-1.22 arterioles per 1 mm(2)) and capillary density (645+/-179 capillaries per 1 mm(2)) were measured. Univariate regression analysis between intracoronary measurements and histological findings revealed that instantaneous hyperemic diastolic velocity-pressure slope correlated with arteriolar obliteration (r=0.58, P=0.014) and capillary density (r=0.60, P=0.012). Statistical adjustment revealed an independent contribution of arteriolar obliteration (beta=0.61, P=0.0009) and capillary density (beta=-0.60, P=0.0008) to instantaneous hyperemic diastolic velocity-pressure slope values, resulting in an excellent predictive model (r=0.84, P=0.0002). Coronary resistance index correlated only with capillary density (r=0.70, P=0.019). Relative indices (coronary flow velocity reserve and coronary resistance reserve) did not correlate significantly with arteriolar obliteration, capillary density, or arteriolar density.

CONCLUSIONS

Intracoronary indices derived from pressure and flow, particularly instantaneous hyperemic diastolic velocity-pressure slope, appear to be superior to coronary flow velocity reserve in detecting structural microcirculatory changes. Both arteriolar obliteration and capillary rarefaction seem to influence microcirculatory hemodynamics independently.

Transit-time blood flow measurements in sequential saphenous coronary artery bypass grafts

BACKGROUND

Little information is available on transit-time flow measurements of sequential saphenous vein grafts. The aim of the study was evaluation of mean blood flow and pulsatility index of sequential saphenous vein grafts in a large population of patients operated on with coronary artery bypass grafting.

METHODS

In 581 patients 1,390 grafts were nested into left internal mammary artery to left anterior descending artery, single vein grafts, or double and triple sequential vein grafts, and analyzed.

RESULTS

Within the single vein graft group there were no differences between flow of grafts to different target vessels except for diagonals (diagonal versus obtuse marginal, p < 0.001; versus posterior descending artery, p = 0.035; versus right coronary artery, p = 0.003). Flows measured in single vein grafts were significantly lower than in double (p < 0.001) and triple sequential vein grafts (p < 0.001). Flows were lower in double versus triple sequential vein grafts (p = 0.017) and higher in men versus women (p < 0.001). Mean pulsatility index of vein grafts were lower in the left versus the right coronary system, 2.0 +/- 0.01 and 2.4 +/- 0.06, respectively (p < 0.001). Between sex and groups of vein grafts within each coronary system, mean pulsatility index had similar values.

CONCLUSIONS

Blood flow increases from single to double and up to triple sequential grafts. Single grafts directed to diagonals have the lowest flow. Graft blood flows are higher in male versus female patients. Single, double, and triple saphenous vein grafts have similar pulsatility indexes. Pulsatility index of grafts to the right coronary system is significantly higher than that of grafts to the left coronary system.

Characteristics of the flow velocity-pressure gradient relation in the assessment of stenoses: an in vitro study

OBJECTIVES

The flow velocity-pressure gradient (v-dp) relation is clinically used to assess coronary stenoses. This in vitro study aimed to investigate the ability to determine the impact of each individual stenosis in the setting of two consecutive stenoses, the effect of variable stenosis reference diameters and the impact of one or two wires in a stenosis, on the v-dp relation.

METHODS

The model consisted of a reservoir and different sized tubes and stenoses. Pressure gradient and flow velocity were assessed with a pressure and a Doppler wire. By plotting flow velocity and pressure gradient on an X-Y plot, the v-dp relation was determined.

RESULTS

The v-dp relation of a proximal stenosis was not influenced by a distal stenosis. The diameter of the segment where flow velocity was measured influenced the v-dp relation. This could be corrected by substituting flow velocity with volume flow. The presence of one or two wires in a stenosis made the v-dp relation substantially steeper.

CONCLUSIONS

The v-dp relation can be used to determine the significance of each individual stenosis in arteries with consecutive stenoses, provided that the distance between the stenoses is large enough. The diameter of the segment where flow velocity is measured and the presence of one or two wires substantially affect the v-dp relation. (Neth Heart J 2008;16:156-62.).

Scaling of myocardial mass to flow and morphometry of coronary arteries

There is no doubt that scaling relations exist between myocardial mass and morphometry of coronary vasculature. The purpose of this study is to quantify several morphological (diameter, length, and volume) and functional (flow) parameters of the coronary arterial tree in relation to myocardial mass. Eight normal porcine hearts of 117-244 g (mean of 177.5 +/- 32.7) were used in this study. Various coronary subtrees of the left anterior descending, right coronary, and left circumflex arteries were perfused at pressure of 100 mmHg with different colors of a polymer (Microfil) to obtain rubber casts of arterial trees corresponding to different regions of myocardial mass. Volume, diameter, and cumulative length of coronary arteries were reconstructed from casts to analyze their relationship to the perfused myocardial mass. Volumetric flow was measured in relationship with perfused myocardial mass. Our results show that arterial volume is linearly related to regional myocardial mass, whereas the sum of coronary arterial branch lengths, vessel diameters, and volumetric flow show an approximately 3/4, 3/8, and 3/4 power-law relationship, respectively, in relation to myocardial mass. These scaling laws suggest fundamental design principles underlying the structure-function relationship of the coronary arterial tree that may facilitate diagnosis and management of diffuse coronary artery disease.

Non-invasive assessment of coronary flow and coronary flow reserve by transthoracic Doppler echocardiography: a magic tool for the real world

Transthoracic Doppler echocardiography, introduced in the echo-lab in recent last years, to measure coronary flow and coronary flow reserve, is a very attractive tool, totally non-invasive, and easily available at bedside. This review summarizes the actual possibilities of this tool, its multiple potential clinical applications and diagnostic insights, and its arising prognosis value, in coronary artery disease as in various settings affecting the coronary microcirculation.

Anatomical and physiologic assessments in patients with small coronary artery disease: final results of the Physiologic and Anatomical Evaluation Prior to and After Stent Implantation in Small Coronary Vessels (PHANTOM) trial

BACKGROUND

Patients with small coronary arteries are at high risk for complications after percutaneous coronary intervention (PCI). The objective of our study was to investigate the correlation between angiography, intravascular ultrasound (IVUS), and fractional flow reserve (FFR) in patients with moderate stenoses in small (<2.8 mm) coronary arteries.

METHODS AND RESULTS

Sixty consecutive patients, of 800 scheduled for PCI during the study period, were prospectively enrolled in the study. The FFR was measured after a 2-minute infusion of adenosine. For the preprocedural assessments, 60 patients underwent an FFR measurement, 56 underwent an IVUS, and 60 underwent an angiography; for the postprocedural assessments, 22 patients underwent an FFR measurement, 18 underwent an IVUS, and 22 underwent an angiography. The jeopardy score for the target vessel was calculated. Data were analyzed by an independent core laboratory. Patients with an FFR >0.75 were deferred from PCI. Patients were stratified in 2 groups according to their FFR values (< or =0.75 vs >0.75) and were followed for 1 year. Significant (FFR < or =0.75) coronary stenosis was observed in only 35% of the patients. The mean preprocedural FFR values were 0.79 +/- 0.13 for the overall population, 0.64 +/- 0.08 for the patients with an FFR < or =0.75, and 0.87 +/- 0.06 for the patients with an FFR >0.75. There was no correlation between angiography, IVUS, and FFR. The jeopardy score was inversely correlated with FFR (R = -0.32). Only a third of the patients with optimal stenting defined by IVUS achieved an FFR >0.90. After 1 year, 24% of the patients with an FFR < or =0.75 required a repeat PCI. There was no occurrence of myocardial infarction or death, and only 2.6% of the patients deferred from PCI required revascularization.

CONCLUSION

Anatomical parameters are limited in determining the hemodynamic significance of small coronary disease. Most moderate stenoses in small coronaries could be safely deferred from PCI based on FFR.

Effects of distension of urinary bladder on coronary conduit and resistance vessels in hyperlipidemic patients

BACKGROUND

Distension of the urinary bladder reflexly causes a change of coronary vasomotor response. The effect of such distension on the coronary circulation in hyperlipidemic patients, a condition with impaired endothelial function, remains unknown.

HYPOTHESIS

We tested the hypothesis whether urinary bladder distension caused an exaggerated vasomotor response of epicardial and resistance vasoconstriction in hyperlipidemic patients.

METHODS

Thirty patients with early atherosclerosis (< 50% diameter stenosis) were divided into three groups: Group 1 (n = 10): hyperlipidemia without doxazosin administration; Group 2 (n = 10): hyperlipidemia with pretreatment of alpha1-adrenergic receptor blocker (oral doxazosin 2 mg); and Group 3 (n = 10): normolipidemia. A prospective analysis of the results of quantitative angiograms, intracoronary Doppler flow, and lactate concentrations from aortic root and coronary sinus was performed during distension of urinary bladder.

RESULTS

Bladder distension significantly decreased coronary diameter at the stenotic segments (p = 0.004), coronary blood flow (p = 0.05), and increased coronary resistance (p = 0.006) compared with baseline values, in Group 1 patients. In Group 2 patients during bladder distension, coronary diameter, coronary blood flow, and coronary resistance showed no significant changes compared with baseline values. There were significant differences of stenotic coronary diameter (p = 0.01) between Groups 1 and 3 during bladder distension despite similar changes in rate-pressure product. No significant differences were noted among the groups in the responses of coronary diameter, coronary blood flow, and coronary resistance after nitroglycerin administration.

CONCLUSIONS

The present study showed that urinary bladder distension caused an abnormal vasomotor response of epicardial vasoconstriction and that a concomitant increased coronary resistance involved mechanisms related to alpha1-adrenoceptors. Hyperlipidemia may further impair the response. Pretreated administration of doxazosin had reversed the changes toward baseline. Vasoconstriction during bladder distension can be relieved after nitroglycerin administration, suggesting an unchanged responsiveness of vascular smooth muscle cells to such distension.