Coronary Microvascular Dysfunction as a Mechanism of Angina in Severe AS: Prospective Adenosine-Stress CMR Study

Changes in microcirculation following transcatheter aortic valve implantation in patients with stable coronary artery disease

BACKGROUND

Few studies have assessed coronary physiology in the setting of coronary artery disease (CAD) with severe aortic stenosis (AS). Fractional flow reserve (FFR) to guide revascularization in such patients is not validated.

AIMS

We describe changes in coronary physiology in this population before and after transcatheter aortic valve implantation (TAVI).

METHODS

Patients with stable CAD and severe AS treated with TAVI were prospectively included during 2020-2023. Coronary physiology was assessed before and immediately after TAVI, and at follow-up (median 5.4 months).

RESULTS

Twenty-nine patients (mean age 81.3 years) were included. Median (95% confidence interval) FFR decreased numerically, from 0.83 (0.79-0.84) pre-TAVI to 0.81 (0.78-0.83) post-TAVI. During hyperaemia, the transit mean time reduced numerically, from 0.27 (0.19-0.35) to 0.20 (0.18-0.27) seconds, reflecting increased coronary flow. Basal microvascular resistance increased numerically, from 24 (21-35) to 32 (23-45), while resistive reserve ratio increased significantly, from 1.8 (1.5-2.3) to 2.6 (2.2-3.1) (P=0.002). Consequently, coronary flow reserve (CFR) improved significantly, from 1.5 (1.2-1.7) to 1.9 (1.5-2.4) (P=0.006). Among 21 patients with follow-up, no significant change in FFR was observed and the significance of the increase in CFR was lost. Only three patients had an index of microvascular resistance>25, indicating microvascular impairment during hyperaemia.

CONCLUSIONS

In stable CAD patients treated with TAVI for severe AS, valve replacement provides an immediate improvement in CFR. FFR shows a minimal decrease after valve implantation, supporting its reproducibility to guide revascularization in such patients.

CLINICAL TRIAL REGISTRATION

.NCT04663334.

Functional assessment of coronary artery disease in patients with severe aortic stenosis: a review

A significant proportion of patients with severe aortic stenosis (AS) undergoing transcatheter aortic valve implantation (TAVI) have concomitant coronary artery disease (CAD). The best way to treat these patients is contentious. Conventional assessments of ischaemia such as fractional flow reserve (FFR) and instantaneous wave-free ratio are not validated in the context of severe AS despite having a Class I European Society of Cardiology indication in patients with isolated coronary disease. A better understanding of how we assess and interpret coronary physiology in these patients is required to optimise treatment pathways. Only one prospective, randomised trial has investigated the routine use of FFR to guide revascularisation in patients undergoing TAVI and several observational cohort studies have measured changes in hyperaemic and resting indices in patients with severe AS as well as before and after TAVI. The purpose of this review article is to provide a summary of the current data regarding the functional assessment of CAD in patients with severe AS and highlight the current best practice in this evolving area.

Coronary Microvascular Dysfunction: Searching the Strongest Imaging Modality in Different Scenarios

Coronary microvascular dysfunction is a clinical condition very diffuse in many different settings. Often the diagnosis can be very tricky, and choosing the proper diagnostic strategy can be fundamental for reaching the goal. The aim of this review is to evaluate the properties and the feasibility of our tests in specific scenarios by looking at the performances of each methodology reported in the literature.

Prognostic value of coronary microvascular dysfunction in patients with aortic stenosis and nonobstructed coronary arteries

BACKGROUND

Patients with aortic valve stenosis have been postulated to have coronary microvascular dysfunction (CMD) contributing to the clinical symptoms and adverse outcomes. The coronary angiography (CAG)-derived index of microcirculatory resistance (caIMR) is proposed as a novel, less invasive and pressure-wire-free index to assess CMD. This study aimed to quantify CMD assessed by caIMR and investigate its prognostic impact in patients with aortic valve stenosis.

METHODS

This study included 77 moderate or severe aortic valve stenosis patients with no obstructive coronary disease (defined as having no stenosis more than 50% in diameter) who underwent caIMR measurement. CMD was defined by caIMR at least 25. Major adverse cardiovascular events (MACE) were the clinical outcomes during the median 40 months of follow-up.

RESULTS

The incidence of CMD was 47.7%. Seventeen MACE occurred during the follow-up duration. CMD was associated with an increased risk of MACE (log-rank P < 0.001) and an independent predictor of clinical outcomes [hazard ratio 5.467, 95% confidence interval (CI) 1.393-21.458; P = 0.015]. The receiver-operating characteristic (ROC) curve analysis demonstrated that caIMR could provide a significant predictive value for MACE in aortic valve stenosis patients (AUC 0.785, 95% CI 0.609-0.961, P < 0.001). In addition, the risk of MACE was higher in CMD patients with severe aortic valve stenosis (log-rank P < 0.001) and no aortic valve replacement (log-rank P = 0.003) than in other groups.

CONCLUSION

Aortic valve stenosis patients demonstrated markedly impaired caIMR. CMD assessed by caIMR increases the risk of MACE and is an independent predictor of adverse outcomes in aortic valve stenosis patients. This finding suggests that using caIMR in the clinical assessment may help identify high-risk groups and stimulate earlier intervention.

Multi-modality imaging in aortic stenosis: an EACVI clinical consensus document

In this EACVI clinical scientific update, we will explore the current use of multi-modality imaging in the diagnosis, risk stratification, and follow-up of patients with aortic stenosis, with a particular focus on recent developments and future directions. Echocardiography is and will likely remain the key method of diagnosis and surveillance of aortic stenosis providing detailed assessments of valve haemodynamics and the cardiac remodelling response. Computed tomography (CT) is already widely used in the planning of transcutaneous aortic valve implantation. We anticipate its increased use as an anatomical adjudicator to clarify disease severity in patients with discordant echocardiographic measurements. CT calcium scoring is currently used for this purpose; however, contrast CT techniques are emerging that allow identification of both calcific and fibrotic valve thickening. Additionally, improved assessments of myocardial decompensation with echocardiography, cardiac magnetic resonance, and CT will become more commonplace in our routine assessment of aortic stenosis. Underpinning all of this will be widespread application of artificial intelligence. In combination, we believe this new era of multi-modality imaging in aortic stenosis will improve the diagnosis, follow-up, and timing of intervention in aortic stenosis as well as potentially accelerate the development of the novel pharmacological treatments required for this disease.

Near-infrared spectroscopy-intravascular ultrasound to improve assessment of coronary artery disease severity in patients referred for transcatheter aortic valve implantation (The IMPACTavi registry): Design and rationale

BACKGROUND

Transcatheter aortic valve implantation (TAVI) was established as a standard treatment for high-operative risk patients with severe aortic stenosis (AS). Although coronary artery disease (CAD) often coexists with AS, clinical and angiographic evaluations of stenosis severity are unreliable in this specific setting. To provide precise risk stratification of coronary lesions, combined near-infrared spectroscopy and intravascular ultrasound (NIRS-IVUS) was developed to integrate morphological and molecular information on plaque composition. However, there is a lack of evidence on the association between NIRS-IVUS derived findings such as maximum 4mm lipid core burden index (maxLCBI4mm) and clinical outcomes in AS patients undergoing TAVI. This registry aims to assess feasibility and safety of NIRS-IVUS imaging in the setting of routine pre-TAVI coronary angiography to improve assessment of CAD severity.

METHODS

The registry is designed as a non-randomized, prospective, observational, multicenter cohort registry. Patients referred for TAVI with angiographic evidence of CAD receive NIRS-IVUS imaging and are followed up to 24 months. Enrolled patients are classified as NIRS-IVUS positive and NIRS-IVUS negative, respectively, based on their maxLCBI4mm to compare their clinical outcomes. The primary endpoint of the registry is major adverse cardiovascular events over a 24-month follow-up period.

CONCLUSIONS

Identification of patients likely or unlikely to benefit from revascularization prior to TAVI represents an important unmet clinical need. This registry is designed to investigate whether NIRS-IVUS-derived atherosclerotic plaque characteristics can identify patients and lesions at risk for future adverse cardiovascular events after TAVI, in order to refine interventional decision-making in this challenging patient population.

Invasive Functional Assessment of Coronary Artery Disease in Patients with Severe Aortic Stenosis in the TAVI Era

Coronary artery disease (CAD) is a common finding in patients suffering from aortic valve stenosis (AS), with a prevalence of over 50% in patients 70 years of age or older. Transcatheter aortic valve intervention (TAVI) is the standard treatment option for patients with severe AS and at least 75 years of age. Current guidelines recommend percutaneous coronary intervention (PCI) in patients planned for TAVI with stenoses of >70% in the proximal segments of non-left main coronary arteries and in >50% of left main stenoses. While the guidelines on myocardial revascularization clearly recommend functional assessment of coronary artery stenoses of less than 90% in the absence of non-invasive ischemia testing, a statement regarding invasive functional testing in AS patients with concomitant CAD is lacking in the recently published guideline on the management of valvular heart disease. This review aims to provide an overview of the hemodynamic background in AS patients, discusses and summarizes the current evidence of invasive functional testing in patients with severe AS, and gives a future perspective on the ongoing trials on that topic.

Safety of Stress Cardiac Magnetic Resonance in Patients With Moderate to Severe Aortic Valve Stenosis

BACKGROUND

Dobutamine and adenosine stress cardiac magnetic resonance (CMR) imaging is relatively contraindicated in patients with moderate to severe aortic valve stenosis (AS). We aimed to determine the safety of dobutamine and adenosine stress CMR in patients with moderate to severe AS.

METHODS

In this retrospective study patients with AS who underwent either dobutamine or adenosine stress CMR for exclusion of obstructive coronary artery disease were enrolled. We recorded clinical data, CMR and echocardiography findings, and complications as well as minor symptoms. Patients with AS were compared to matched individuals without AS.

RESULTS

A total of 187 patients with AS were identified and compared to age-, gender- and body mass index-matched 187 patients without AS. No severe complications were reported in the study nor the control group. The reported frequency of non-severe complications and minor symptoms were similar between the study and the control groups. Nineteen patients with AS experienced non-severe complications or minor symptoms during dobutamine stress CMR compared to eighteen patients without AS (p = 0.855). One patient with AS and two patients without AS undergoing adenosine stress CMR experienced minor symptoms (p = 0.562). Four examinations were aborted because of chest pain, paroxysmal atrial fibrillation and third-degree atrioventricular block. Inducible ischaemia, prior coronary artery bypass grafting, prior stroke and age were associated with a higher incidence of complications and minor symptoms.

CONCLUSIONS

Moderate to severe AS was not associated with complications during CMR stress test. The incidence of non-severe complications and minor symptoms was greater with dobutamine.

The spectrum and systemic associations of microvascular dysfunction in the heart and other organs

Microvascular dysfunction (MVD) contributes to several conditions that increase morbidity and mortality, including ischemic heart disease, heart failure, dementia, chronic kidney disease and hypertension. Consequently, MVD imposes a substantial burden on healthcare systems worldwide. In comparison to macrovascular dysfunction, MVD has been incompletely investigated, and it remains uncertain whether MVD in an organ constitutes a distinct pathology or a manifestation of a systemic disorder. Here, we summarize and appraise the techniques that are used to diagnose MVD. We review the disorders of the heart, brain and kidneys in which the role of MVD has been highlighted and summarize evidence hinting at a systemic or multi-organ nature of MVD. Finally, we discuss the benefits and limitations of implementing MVD testing in clinical practice with a focus on new interventions that are beginning to emerge.

Challenges in Diagnosis and Functional Assessment of Coronary Artery Disease in Patients With Severe Aortic Stenosis

More than half of patients with severe aortic stenosis (AS) over 70 years old have coronary artery disease (CAD). Exertional angina is often present in AS-patients, even in the absence of significant CAD, as a result of oxygen supply/demand mismatch and exercise-induced myocardial ischemia. Moreover, persistent myocardial ischemia leads to extensive myocardial fibrosis and subsequent coronary microvascular dysfunction (CMD) which is defined as reduced coronary vasodilatory capacity below ischemic threshold. Therefore, angina, as well as noninvasive stress tests, have a low specificity and positive predictive value (PPV) for the assessment of epicardial coronary stenosis severity in AS-patients. Moreover, in symptomatic patients with severe AS exercise testing is even contraindicated. Given the limitations of noninvasive stress tests, coronary angiography remains the standard examination for determining the presence and severity of CAD in AS-patients, although angiography alone has poor accuracy in the evaluation of its functional severity. To overcome this limitation, the well-established invasive indices for the assessment of coronary stenosis severity, such as fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR), are now in focus, especially in the contemporary era with the rapid increment of transcatheter aortic valve replacement (TAVR) for the treatment of AS-patients. TAVR induces an immediate decrease in hyperemic microcirculatory resistance and a concomitant increase in hyperemic flow velocity, whereas resting coronary hemodynamics remain unaltered. These findings suggest that FFR may underestimate coronary stenosis severity in AS-patients, whereas iFR as the non-hyperemic index is independent of the AS severity. However, because resting coronary hemodynamics do not improve immediately after TAVR, the coronary vasodilatory capacity in AS-patients treated by TAVR remain impaired, and thus the iFR may overestimate coronary stenosis severity in these patients. The optimal method for evaluating myocardial ischemia in patients with AS and co-existing CAD has not yet been fully established, and this important issue is under further investigation. This review is focused on challenges, limitations, and future perspectives in the functional assessment of coronary stenosis severity in these patients, bearing in mind the complexity of coronary physiology in the presence of this valvular heart disease.

2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

This clinical practice guideline for the evaluation and diagnosis of chest pain provides recommendations and algorithms for clinicians to assess and diagnose chest pain in adult patients.

METHODS

A comprehensive literature search was conducted from November 11, 2017, to May 1, 2020, encompassing randomized and nonrandomized trials, observational studies, registries, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Collaboration, Agency for Healthcare Research and Quality reports, and other relevant databases. Additional relevant studies, published through April 2021, were also considered.

STRUCTURE

Chest pain is a frequent cause for emergency department visits in the United States. The "2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain" provides recommendations based on contemporary evidence on the assessment and evaluation of chest pain. This guideline presents an evidence-based approach to risk stratification and the diagnostic workup for the evaluation of chest pain. Cost-value considerations in diagnostic testing have been incorporated, and shared decision-making with patients is recommended.

Coronary microvascular dysfunction as a chronic inflammatory state: Is there a role for omega-3 fatty acid treatment?

Coronary microvascular dysfunction is a ubiquitous pathologic process that is operational in ischemia with no obstructive coronary artery disease and other cardiovascular disorders including heart failure with preserved ejection fraction. It may, in fact, be a manifestation of a multi-systemic condition of small vessel dysfunction that also affects the brain and kidneys. While the pathophysiology driving coronary microvascular dysfunction is multifactorial, chronic inflammation plays an important role. Resolution of inflammation is an active process mediated, in part, by a family of locally active mediators biosynthesized from omega-3 fatty acids, collectively referred to as specialized pro-resolving mediators. Omega-3 fatty acid treatment modulates inflammation and is associated with improved cardiovascular outcomes and attenuation of plaque progression on cardiovascular imaging. Whether omega-3 fatty acid treatment attenuates coronary microvascular dysfunction is unknown.

The coronary and microcirculatory measurements in patients with aortic valve stenosis study: rationale and design

Although concomitant coronary artery disease (CAD) is frequent in patients with severe aortic stenosis (AS), hemodynamic assessment of CAD severity in patients undergoing valve replacement for severe AS is challenging. Myocardial hypertrophic remodeling interferes with coronary blood flow and may influence the values of fractional flow reserve (FFR) and nonhyperemic pressure ratios (NHPRs). The aim of the current study is to investigate the effect of the AS and its treatment on current indices used for evaluation of CAD. We will compare intracoronary hemodynamics before, immediately after, and 6 mo after aortic valve replacement (AVR) when it is expected that microvascular function has improved. Furthermore, we will compare FFR and resting full-cycle ratio (RFR) with myocardial perfusion single-photon emission-computed tomography (SPECT) as indicators of myocardial ischemia in patients with AS and CAD. One-hundred consecutive patients with AS and intermediate CAD will be prospectively included. Patients will undergo pre-AVR SPECT and intracoronary hemodynamic assessment at baseline, immediately after valve replacement [if transcatheter AVR (TAVR) is chosen], and 6 mo after AVR. The primary end point is the change in FFR 6 mo after AVR. Secondary end points include the acute change of FFR after TAVR, the diagnostic accuracy of FFR versus RFR compared with SPECT for the assessment of ischemia, changes in microvascular function as assessed by the index of microcirculatory resistance (IMR), and the effect of these changes on FFR. The present study will evaluate intracoronary hemodynamic parameters before, immediately after, and 6 mo after AVR in patients with AS and intermediate coronary stenosis. The understanding of the impact of AVR on the assessment of FFR, NHPR, and microvascular function may help guide the need for revascularization in patients with AS and CAD planned for AVR.

2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

This clinical practice guideline for the evaluation and diagnosis of chest pain provides recommendations and algorithms for clinicians to assess and diagnose chest pain in adult patients.

METHODS

A comprehensive literature search was conducted from November 11, 2017, to May 1, 2020, encompassing randomized and nonrandomized trials, observational studies, registries, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Collaboration, Agency for Healthcare Research and Quality reports, and other relevant databases. Additional relevant studies, published through April 2021, were also considered.

STRUCTURE

Chest pain is a frequent cause for emergency department visits in the United States. The "2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain" provides recommendations based on contemporary evidence on the assessment and evaluation of chest pain. This guideline presents an evidence-based approach to risk stratification and the diagnostic workup for the evaluation of chest pain. Cost-value considerations in diagnostic testing have been incorporated, and shared decision-making with patients is recommended.

2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

This clinical practice guideline for the evaluation and diagnosis of chest pain provides recommendations and algorithms for clinicians to assess and diagnose chest pain in adult patients.

METHODS

A comprehensive literature search was conducted from November 11, 2017, to May 1, 2020, encompassing randomized and nonrandomized trials, observational studies, registries, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Collaboration, Agency for Healthcare Research and Quality reports, and other relevant databases. Additional relevant studies, published through April 2021, were also considered. Structure: Chest pain is a frequent cause for emergency department visits in the United States. The "2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain" provides recommendations based on contemporary evidence on the assessment and evaluation of chest pain. This guideline presents an evidence-based approach to risk stratification and the diagnostic workup for the evaluation of chest pain. Cost-value considerations in diagnostic testing have been incorporated, and shared decision-making with patients is recommended.

Coronary Revascularization in Patients Undergoing Aortic Valve Replacement for Severe Aortic Stenosis

Aortic stenosis (AS) and coronary artery disease (CAD) frequently coexist, with up to two thirds of patients with AS having significant CAD. Given the challenges when both disease states are present, these patients require a tailored approach diagnostically and therapeutically. In this review the authors address the impact of AS and aortic valve replacement (AVR) on coronary hemodynamic status and discuss the assessment of CAD and the role of revascularization in patients with concomitant AS and CAD. Remodeling in AS increases the susceptibility of myocardial ischemia, which can be compounded by concomitant CAD. AVR can improve coronary hemodynamic status and reduce ischemia. Assessment of the significance of coexisting CAD can be done using noninvasive and invasive metrics. Revascularization in patients undergoing AVR can benefit certain patients in whom CAD is either prognostically or symptomatically important. Identifying this cohort of patients is challenging and as yet incomplete. Patients with dual pathology present a diagnostic and therapeutic challenge; both AS and CAD affect coronary hemodynamic status, they provoke similar symptoms, and their respective treatments can have an impact on both diseases. Decisions regarding coronary revascularization should be based on understanding this complex relationship, using appropriate coronary assessment and consensus within a multidisciplinary team.

A New Method for Aortic Valve Planimetry with High-Resolution 3-Dimensional MRI and Its Comparison with Conventional Cine MRI and Echocardiography for Assessing the Severity of Aortic Valvular Stenosis

OBJECTIVE

We aimed to compare the aortic valve area (AVA) calculated using fast high-resolution three-dimensional (3D) magnetic resonance (MR) image acquisition with that of the conventional two-dimensional (2D) cine MR technique.

MATERIALS AND METHODS

We included 139 consecutive patients (mean age ± standard deviation [SD], 68.5 ± 9.4 years) with aortic valvular stenosis (AS) and 21 asymptomatic controls (52.3 ± 14.2 years). High-resolution T2-prepared 3D steady-state free precession (SSFP) images (2.0 mm slice thickness, 10 contiguous slices) for 3D planimetry (3DP) were acquired with a single breath hold during mid-systole. 2D SSFP cine MR images (6.0 mm slice thickness) for 2D planimetry (2DP) were also obtained at three aortic valve levels. The calculations for the effective AVA based on the MR images were compared with the transthoracic echocardiographic (TTE) measurements using the continuity equation.

RESULTS

The mean AVA ± SD derived by 3DP, 2DP, and TTE in the AS group were 0.81 ± 0.26 cm², 0.82 ± 0.34 cm², and 0.80 ± 0.26 cm², respectively (p = 0.366). The intra-observer agreement was higher for 3DP than 2DP in one observer: intraclass correlation coefficient (ICC) of 0.95 (95% confidence interval [CI], 0.94-0.97) and 0.87 (95% CI, 0.82-0.91), respectively, for observer 1 and 0.97 (95% CI, 0.96-0.98) and 0.98 (95% CI, 0.97-0.99), respectively, for observer 2. Inter-observer agreement was similar between 3DP and 2DP, with the ICC of 0.92 (95% CI, 0.89-0.94) and 0.91 (95% CI, 0.88-0.93), respectively. 3DP-derived AVA showed a slightly higher agreement with AVA measured by TTE than the 2DP-derived AVA, with the ICC of 0.87 (95% CI, 0.82-0.91) vs. 0.85 (95% CI, 0.79-0.89).

CONCLUSION

High-resolution 3D MR image acquisition, with single-breath-hold SSFP sequences, gave AVA measurement with low observer variability that correlated highly with those obtained by TTE.

Coronary Assessment and Revascularization Before Transcutaneous Aortic Valve Implantation: An Update on Current Knowledge

Transcutaneous aortic valve implantation (TAVI) has led to a paradigm shift in the treatment of severe aortic stenosis (AS) in the elderly and is expanding to still younger and lower-risk patients with severe AS as an alternative to surgical aortic valve replacement (SAVR). While the role of coronary artery bypass grafting with SAVR is well-documented, the analog of percutaneous coronary intervention with TAVI is less so. The aim of this review is to provide an overview of the important challenges in treating severe AS and co-existing coronary artery disease in patients planned for TAVI.

Aortic Valve Disease and Associated Complex CAD: The Interventional Approach

Coronary artery disease (CAD) is highly prevalent in patients with severe aortic stenosis (AS). The management of CAD is a central aspect of the work-up of patients undergoing transcatheter aortic valve implantation (TAVI), but few data are available on this field and the best percutaneous coronary intervention (PCI) practice is yet to be determined. A major challenge is the ability to elucidate the severity of bystander coronary stenosis independently of the severity of aortic valve stenosis and subsequent impact on blood flow. The prognostic role of CAD in patients undergoing TAVI is being still debated and the benefits and the best timing of PCI in this context are currently under evaluation. Additionally, PCI in the setting of advanced AS poses some technical challenges, due to the complex anatomy, risk of hemodynamic instability, and the increased risk of bleeding complications. This review aims to provide a comprehensive synthesis of the available literature on myocardial revascularization in patients with severe AS undergoing TAVI. This work can assist the Heart Team in individualizing decisions about myocardial revascularization, taking into account available diagnostic tools as well as the risks and benefits.

Coronary Microcirculation in Aortic Stenosis: Pathophysiology, Invasive Assessment, and Future Directions

With the increasing prevalence of aortic stenosis (AS) due to a growing elderly population, a proper understanding of its physiology is paramount to guide therapy and define severity. A better understanding of the microvasculature in AS could improve clinical care by predicting left ventricular remodeling or anticipate the interplay between epicardial stenosis and myocardial dysfunction. In this review, we combine five decades of literature regarding microvascular, coronary, and aortic valve physiology with emerging insights from newly developed invasive tools for quantifying microcirculatory function. Furthermore, we describe the coupling between microcirculation and epicardial stenosis, which is currently under investigation in several randomized trials enrolling subjects with concomitant AS and coronary disease. To clarify the physiology explained previously, we present two instructive cases with invasive pressure measurements quantifying coexisting valve and coronary stenoses. Finally, we pose open clinical and research questions whose answers would further expand our knowledge of microvascular dysfunction in AS. These trials were registered with NCT03042104, NCT03094143, and NCT02436655.

Pathophysiology, classification, and MRI parallels in microvascular disease of the heart and brain

Diagnostic imaging technology in vascular disease has long focused on large vessels and the pathologic processes that impact them. With improved diagnostic techniques, investigators are now able to uncover many underlying mechanisms and prognostic factors for microvascular disease. In the heart and brain, these pathologic entities include coronary microvascular disease and cerebral small vessel disease, both of which have significant impact on patients, causing angina, myocardial infarction, heart failure, stroke, and dementia. In the current paper, we will discuss parallels in pathophysiology, classification, and diagnostic modalities, with a focus on the role of magnetic resonance imaging in microvascular disease of the heart and brain. Novel approaches for streamlined imaging of the cardiac and central nervous systems including the use of intravascular contrast agents such as ferumoxytol are presented, and unmet research gaps in diagnostics are summarized.

Remote Ischemic Preconditioning Acutely Improves Coronary Microcirculatory Function

Background Remote ischemic preconditioning (RIPC) attenuates myocardial damage during elective and primary percutaneous coronary intervention. Recent studies suggest that coronary microcirculatory function is an important determinant of clinical outcome. The aim of this study was to assess the effect of RIPC on markers of microcirculatory function. Methods and Results Patients referred for cardiac catheterization and fractional flow reserve measurement were randomized to RIPC or sham. Operators and patients were blinded to treatment allocation. Comprehensive physiological assessments were performed before and after RIPC/sham including the index of microcirculatory resistance and coronary flow reserve after intracoronary glyceryl trinitrate and during the infusion of intravenous adenosine. Thirty patients were included (87% male; mean age: 63.1±10.0 years). RIPC and sham groups were similar with respect to baseline characteristics. RIPC decreased the calculated index of microcirculatory resistance (median, before RIPC: 22.6 [interquartile range [IQR]: 17.9-25.6]; after RIPC: 17.5 [IQR: 14.5-21.3]; P=0.007) and increased coronary flow reserve (2.6±0.9 versus 3.8±1.7, P=0.001). These RIPC-mediated changes were associated with a reduction in hyperemic transit time (median: 0.33 [IQR: 0.26-0.40] versus 0.25 [IQR: 0.20-0.30]; P=0.010). RIPC resulted in a significant decrease in the calculated index of microcirculatory resistance compared with sham (relative change with treatment [mean±SD] was -18.1±24.8% versus +6.1±37.5; P=0.047) and a significant increase in coronary flow reserve (+41.2% [IQR: 20.0-61.7] versus -7.8% [IQR: -19.1 to 10.3]; P<0.001). Conclusions The index of microcirculatory resistance and coronary flow reserve are acutely improved by remote ischemic preconditioning. This raises the possibility that RIPC confers cardioprotection during percutaneous coronary intervention as a result of an improvement in coronary microcirculatory function. Clinical Trial Registration URL: www.anzctr.org.au/ . Unique identifier: CTRN12616000486426.

Multimodality Imaging for the Assessment of Severe Aortic Stenosis

Aortic stenosis is the most common type of valvular heart disease. Aortic stenosis is characterized both by progressive valve narrowing and the left ventricular remodeling response that ensues. In aortic stenosis, therapeutic decision essentially depends on symptomatic status, stenosis severity, and status of left ventricular systolic function. Imaging is fundamental for the initial diagnostic work-up, follow-up, and selection of the optimal timing and type of intervention. Noninvasive imaging has played a pivotal role in enhancing our understanding of the complex pathophysiology underlying aortic stenosis, as well as disease progression in both the valve and myocardium. The present review provides the application of multimodality imaging in aortic stenosis.

Myocardial Scar and Mortality in Severe Aortic Stenosis

Supplemental Digital Content is available in the text.

Background:

Aortic valve replacement (AVR) for aortic stenosis is timed primarily on the development of symptoms, but late surgery can result in irreversible myocardial dysfunction and additional risk. The aim of this study was to determine whether the presence of focal myocardial scar preoperatively was associated with long-term mortality.

Methods:

In a longitudinal observational outcome study, survival analysis was performed in patients with severe aortic stenosis listed for valve intervention at 6 UK cardiothoracic centers. Patients underwent preprocedural echocardiography (for valve severity assessment) and cardiovascular magnetic resonance for ventricular volumes, function and scar quantification between January 2003 and May 2015. Myocardial scar was categorized into 3 patterns (none, infarct, or noninfarct patterns) and quantified with the full width at half-maximum method as percentage of the left ventricle. All-cause mortality and cardiovascular mortality were tracked for a minimum of 2 years.

Results:

Six hundred seventy-four patients with severe aortic stenosis (age, 75±14 years; 63% male; aortic valve area, 0.38±0.14 cm²/m²; mean gradient, 46±18 mm Hg; left ventricular ejection fraction, 61.0±16.7%) were included. Scar was present in 51% (18% infarct pattern, 33% noninfarct). Management was surgical AVR (n=399) or transcatheter AVR (n=275). During follow-up (median, 3.6 years), 145 patients (21.5%) died (52 after surgical AVR, 93 after transcatheter AVR). In multivariable analysis, the factors independently associated with all-cause mortality were age (hazard ratio [HR], 1.50; 95% CI, 1.11–2.04; P=0.009, scaled by epochs of 10 years), Society of Thoracic Surgeons score (HR, 1.12; 95% CI, 1.03–1.22; P=0.007), and scar presence (HR, 2.39; 95% CI, 1.40–4.05; P=0.001). Scar independently predicted all-cause (26.4% versus 12.9%; P<0.001) and cardiovascular (15.0% versus 4.8%; P<0.001) mortality, regardless of intervention (transcatheter AVR, P=0.002; surgical AVR, P=0.026 [all-cause mortality]). Every 1% increase in left ventricular myocardial scar burden was associated with 11% higher all-cause mortality hazard (HR, 1.11; 95% CI, 1.05–1.17; P<0.001) and 8% higher cardiovascular mortality hazard (HR, 1.08; 95% CI, 1.01–1.17; P<0.001).

Conclusions:

In patients with severe aortic stenosis, late gadolinium enhancement on cardiovascular magnetic resonance was independently associated with mortality; its presence was associated with a 2-fold higher late mortality.

Pathophysiological coronary and microcirculatory flow alterations in aortic stenosis

Regulation of coronary blood flow is maintained through a delicate balance of ventriculoarterial and neurohumoral mechanisms. The aortic valve is integral to the functions of these systems, and disease states that compromise aortic valve integrity have the potential to seriously disrupt coronary blood flow. Aortic stenosis (AS) is the most common cause of valvular heart disease requiring medical intervention, and the prevalence and associated socio-economic burden of AS are set to increase with population ageing. Valvular stenosis precipitates a cascade of structural, microcirculatory, and neurohumoral changes, which all lead to impairment of coronary flow reserve and myocardial ischaemia even in the absence of notable coronary stenosis. Coronary physiology can potentially be normalized through interventions that relieve severe AS, but normality is often not immediately achievable and probably requires continued adaptation. Finally, the physiological assessment of coronary artery disease in patients with AS represents an ongoing challenge, as the invasive physiological measures used in current cardiology practice are yet to be validated in this population. This Review discusses the key concepts of coronary pathophysiology in patients with AS through presentation of contemporary basic science and data from animal and human studies.

Coronary Microcirculation in Aortic Stenosis

Aortic stenosis is a heterogeneous disorder. Variations in the pathological and physiological responses to pressure overload are incompletely understood and generate a range of flow and pressure gradient patterns, which ultimately cause varying microvascular effects. The impact of cardiac-coronary coupling depends on these pressure and flow effects. In this article, we explore important concepts concerning cardiac physiology and the coronary microcirculation in aortic stenosis and their impact on myocardial remodeling, aortic valve flow patterns, and clinical progression.

How to Diagnose and Manage Angina Without Obstructive Coronary Artery Disease: Lessons from the British Heart Foundation CorMicA Trial

Patients with symptoms and/or signs of ischaemia but no obstructive coronary artery disease (INOCA) present a diagnostic and therapeutic challenge. Microvascular and/or vasospastic angina are the two most common causes of INOCA; however, invasive coronary angiography lacks the sensitivity to diagnose these functional coronary disorders. In this article, the authors summarise the rationale for invasive testing in the absence of obstructive coronary disease, namely that correct treatment for angina patients starts with the correct diagnosis. They provide insights from the CORonary MICrovascular Angina (CorMicA) study, where an interventional diagnostic procedure was performed with linked medical therapy to improve patient health. Identification of these distinct disorders (microvascular angina, vasospastic angina or non-cardiac chest pain) is key for stratifying INOCA patients, allowing prognostic insights and better patient care with linked therapy based on contemporary guidelines. Finally, they propose a framework to diagnose and manage patients in this common clinical scenario.

Impact of residual coronary atherosclerosis on transfemoral transcatheter aortic valve replacement

OBJECTIVES

This study reports on the clinical effects of complete vs incompletely revascularized coronary artery disease on transcatheter aortic valve replacement (TAVR).

BACKGROUND

There is a high prevalence of active coronary artery disease (CAD) in patients undergoing TAVR but preemptive revascularization remains controversial.

METHODS

Patients were categorized into three cohorts: complete revascularization (CR), incomplete revascularization of a major epicardial artery (IR Major), and incomplete revascularization of a minor epicardial artery only (IR Minor). When feasible, SYNTAX scoring was performed for exploratory analysis. Analyses were performed using Cox proportional hazard models and Kaplan-Meier method.

RESULTS

A total of 323 patients with active CAD were included. Adjusted outcomes showed that patients with IR Major had increased incidence of acute myocardial infarction (AMI) or revascularization compared with those in the CR cohort (HR 3.72, P = 0.048). No difference was noted in all-cause mortality or all-cause readmission rates. Exploratory secondary analysis with residual SYNTAX scores showed a significant interaction between disease burden and AMI/revascularization, as well as all-cause readmission. All-cause mortality remained unaffected based on residual SYNTAX scores.

CONCLUSIONS

This is a retrospective single-center study reporting on pre-TAVR revascularization outcomes in patients with active CAD. In this analysis, we found that patients undergoing TAVR benefited from achieving complete revascularization to abate future incidence of AMI/revascularization. Despite this finding, all-cause mortality remained unaffected. Future efforts should focus on the role of functional assessment of the coronaries, as well as the long-term effects of complete revascularization in a larger patient cohort.

Value of adenosine stress cardiovascular magnetic resonance in the evaluation of vessels supplying previously infarcted territories

BACKGROUND

The diagnostic performance of adenosine stress cardiovascular magnetic resonance (CMR) for the detection of significant stenosis in infarct-related arteries is widely unknown. Two different types of perfusion defects can be observed: (a) larger than or (b) equal size as scar.We hypothesized that: (a) defect>scar predicts significant coronary stenosis, and (b) defect=scar predicts an unobstructed infarct-related artery, and (c) angina symptoms might be of additional value in stratification.

PATIENTS AND METHODS

Patients with previous myocardial infarction referred for work-up of myocardial ischemia undergoing adenosine stress CMR were included if they had coronary angiography within 4 weeks of CMR.

RESULTS

Two hundred patients with a mean age of 66±11 years, ischemic scars (subendocardial/transmural), and a mean left ventricular ejection fraction of 53% were included. In patients with defect>scar, the positive predictive value was excellent (88%) and typical angina was reported only in the stenosis group (P=0.002). However, patients with defect=scar (with 50% showing subendocardial scar) had a prevalence of 37% for stenosis, yielding a low negative predictive value of 63%. In this group, symptoms of typical angina were independent of stenosis (P=1.0).

CONCLUSION

A perfusion defect larger than scar is highly predictive for significant stenosis in infarct-related arteries. However, more than a third of the patients with perfusion defect of equal size as scar also showed significant coronary stenosis. As half of these patients showed still viable (subendocardial) scars, there is a high-risk of reinfarction. The addition of angina symptoms seems to increase diagnostic accuracy only in patients with perfusion defects larger than scar.

Association of cardiovascular risk factors on myocardial perfusion and fibrosis in asymptomatic individuals: cardiac magnetic resonance study

Background Myocardial perfusion reserve index (MPRI) and extracellular volume fraction (ECV) on cardiac magnetic resonance (CMR) are known to quantify coronary microvascular dysfunction and myocardial fibrosis, respectively. Purpose To demonstrate that cardiovascular risk factors such as hypertension, diabetes, hyperlipidemia, and smoking are correlated with MPRI and ECV on CMR in asymptomatic individuals. Material and Methods Between October 2013 and July 2014, 196 individuals underwent CMR. After excluding those with chest pain, arrhythmia, and obstructive coronary artery disease, participants were divided into five groups: those without risk factor (n = 26) and those with one (n = 43), two (n = 35), three (n = 24), or four (n = 6) risk factors. MPRI and ECV were obtained on perfusion CMR and pre- and post-T1 mapping, respectively. Results A total of 134 asymptomatic individuals (109 men, 25 women; mean age = 54.4 ± 7.08 years; body mass index [BMI] = 24.96 ± 2.76 kg/m²; Framingham risk score [FRS] = 7.71 ± 5.21) were included. The Jonckheere-Terpstra test demonstrated trends of increasing BMI, FRS, and left ventricular mass index (all P values < 0.001), but decreasing MPRI ( P = 0.001) with increasing numbers of risk factors. Stepwise multiple linear regression demonstrated that an increasing number of cardiovascular risk factors was an independent predictor of MPRI ( P = 0.001). However, there was no significant association between the number of risk factors and ECV ( P = 0.99). Conclusion We demonstrated that an increasing number of cardiovascular risk factors is significantly associated with reduced MPRI, but not with ECV on CMR.

CMR First-Pass Perfusion for Suspected Inducible Myocardial Ischemia

Cardiovascular magnetic resonance (CMR) has evolved from a pioneering research tool to an established noninvasive imaging method for detecting inducible myocardial perfusion deficits. In this consensus document, experts of different imaging techniques summarize the existing body of evidence regarding CMR perfusion as a viable complement to other established noninvasive tools for the assessment of perfusion and discuss the advantages and pitfalls of the technique. A rapid, standardized CMR perfusion protocol is described, which is safe, clinically feasible, and cost-effective for centers with contemporary magnetic resonance equipment. CMR perfusion can be recommended as a routine diagnostic tool to identify inducible myocardial ischemia.

Assessment of reverse remodeling predicted by myocardial deformation on tissue tracking in patients with severe aortic stenosis: a cardiovascular magnetic resonance imaging study

BACKGROUND

The technique of tissue tracking with balanced steady-state free precession cine sequences was introduced, and allowed myocardial strain to be derived directly, offering advantages over traditional myocardial tagging. The aim of this study was to evaluate the correlation between reverse remodeling as an outcome and left ventricular strain using cardiovascular magnetic resonance imaging (CMR) tissue tracking, and to evaluate prediction of reverse remodeling by myocardial deformation in patients with severe aortic stenosis (AS).

METHODS

We enrolled 63 patients with severe AS and normal left ventricular (LV) systolic function (ejection fraction > 60%), who underwent both CMR and transthoracic echocardiography (Echo) before surgical aortic valve replacement (AVR). CMR at 1.5 T, including non and post-contrast T1 mapping for extracellular volume (ECV), was carried out to define the amount of myocardial fibrosis. Cardiac Performance Analysis software was used to derive myocardial deformation as strain parameters from three short-axis cine views (basal, mid and apical levels) and apical 2, 3, and 4 chamber views. The primary outcome was reverse remodeling, as evaluated by regression of left ventricular mass index (LVMI).

RESULTS

Median follow-up was 28.8 months (interquartile range 11.3-38.3 months). As evaluated by LVMI between baseline and follow-up, mass regression was significantly improved after AVR (baseline 145.9 ± 37.0 [g/m2] vs. follow-up 97.7 ± 22.2[g/m2], p < 0.001). Statistically significant Pearson's correlations with LVMI regression were observed for longitudinal global strain (r = -0.461, p < 0.001), radial strain (r = 0.391, p = 0.002), and circumferential strain (r = -0.334, p = 0.009). A simple linear regression analysis showed that all strain parameters could predict the amount of LVMI regression (P < 0.05), as well as non-contrast T1 value (beta = -0.314, p < 0.001) and ECV (beta = -2.546, p = 0.038). However, ECV had the lowest predictive power (multiple r2 = 0.071). Multiple regression analysis showed strain could independently predict the amount of LVMI regression and the longitudinal global strain (beta = -3.335, p < 0.001).

CONCLUSION

Longitudinal global strain measured by CMR tissue tracking as a technique was correlated with reverse remodeling as LVMI regression and was predictive of this outcome. As a simple and practical method, tissue tracking is promising to assess strain and predict reverse remodeling in severe AS, especially in patients with suboptimal Echo image quality.

The emerging role of Cardiovascular Magnetic Resonance in the evaluation of hypertensive heart disease

BACKGROUND

Arterial hypertension is the commonest cause of cardiovascular death. It may lead to hypertensive heart disease (HHD), including heart failure (HF), ischemic heart disease (IHD) and left ventricular hypertrophy (LVH).

MAIN BODY

According to the 2007 ESH/ESC guidelines, the recommended imaging technique is echocardiography (echo), when a more sensitive detection of LVH than that provided by ECG, is needed. Cardiovascular Magnetic Resonance (CMR), a non-invasive, non-radiating technique, offers the following advantages, beyond echo: a) more reliable and reproducible measurements of cardiac parameters such as volumes, ejection fraction and cardiac mass b) more accurate differentiation of LVH etiology by providing information about tissue characterisation c) more accurate evaluation of myocardial ischemia, specifically if small vessels disease is present d) technique of choice for diagnosis of renovascular, aortic tree/branches lesions and quantification of aortic valve regurgitation e) technique of choice for treatment evaluation in clinical trials. The superiority of CMR against echocardiography in terms of reproducibility, operator independency, unrestricted field of view and capability of tissue characterization makes the technique ideal for evaluation of heart, quantification of aortic valve regurgitation, aorta and aortic branches.

CONCLUSIONS

CMR has a great potential in early diagnosis, risk stratification and treatment follow up of HHD. However, an international consensus about CMR in HHD, taking under consideration the cost-benefit ratio, expertise and availability, is still warranted.

Determinants and Prognostic Significance of Symptomatic Status in Patients with Moderately Dysfunctional Bicuspid Aortic Valves

Background

We aimed to identify the clinical and echocardiographic determinants of symptoms and their prognostic implications in patients with moderately dysfunctional bicuspid aortic valves (BAVs).

Methods

Among 1,019 subjects in the BAV registry treated in a single tertiary care center, the records of 127 patients (85 men, age 58±13 years) with moderately dysfunctional BAVs were comprehensively reviewed. The patients were divided into two groups based on symptom status: asymptomatic (n = 80) vs. symptomatic (n = 47). The primary end-point was defined as a composite of aortic valve surgery, hospitalization for heart failure, and any cause of death.

Results

The symptomatic group had a higher proportion of females, hypertension, aortic stenosis, and aortopathy than did the asymptomatic group. The symptomatic group showed lower e′ (5.5±1.7 vs. 6.5±2.2 cm/s, p = 0.003), higher E/e′ (13.3 ± 4.9 vs. 10.9±3.7, p = 0.002), and larger left atrial volume index (29.9±11.4 vs. 24.6±9.1 ml/m², p = 0.006) than did the asymptomatic group. In multivariate logistic regression analysis, female gender (odds ratio [OR] 2.84, 95% confidence interval [CI] 1.10–7.36, p = 0.031), hypertension (OR 3.07, 95% CI 1.20–7.82, p = 0.019), moderate aortic stenosis (OR 5.33 5.78, 95% CI 1.99–16.83, p = 0.001), E/e′ >15 (OR 3.82, 95% CI 1.03–11.19, p = 0.015), and aortopathy (OR 2.76, 95% CI 1.07–7.10, p = 0.035) were independently correlated with symptom status. The symptomatic group showed a significantly lower rate of event-free survival during the 8-year follow-up period (54±9% vs. 68±10%, p = 0.001).

Conclusions

In patients with moderately dysfunctional BAVs, the presence of moderate aortic stenosis, aortopathy, and diastolic dysfunction determines symptom status, along with female gender and hypertension. Symptom status was associated with clinical outcomes.

Emerging drugs for the treatment of angina pectoris

INTRODUCTION

Angina pectoris, or symptomatic myocardial ischaemia, reflects an impairment of coronary blood flow, and usually a deficiency of available myocardial energetics. Treatment options vary with the precise cause, which may vary with regards to the roles of increased myocardial oxygen demand versus reduced supply. Traditionally, organic nitrates, β-adrenoceptor antagonists, and non-dihydropyridine calcium antagonists were the only commonly used prophylactic anti-anginal agents. However, many patients failed to respond adequately to such therapy, and/or were unsuitable for their use. Areas covered: A number of 'new' agents have been shown to represent ancillary forms of prophylactic anti-anginal therapy and are particularly useful in patients who are relatively unsuitable for either percutaneous or surgical revascularisation. These include modulators of myocardial metabolic efficiency, such as perhexiline, trimetazidine and ranolazine, as well as high dose allopurinol, nicorandil and ivabradine. The advantages and disadvantages of these various agents are summarized. Expert opinion: 'Optimal' medical treatment of angina pectoris now includes use of agents primarily intended to reduce risk of infarction (e.g. statins, aspirin, ACE inhibitors). In patients whose angina persists despite the use of 'standard' anti-anginal therapy, and who are not ideal for invasive revascularization options, a number of emerging drugs offer prospects of symptomatic relief.

[Measurement of fractional flow reserve in patients with severe aortic stenosis: A valid test?]

A 54-year-old woman was hospitalized for an acute pulmonary oedema revealing a severe aortic stenosis (AS) associated with an aortic aneurysm and a left ventricular hypertrophy (LVH). The coronary angiography found an equivocal left main lesion. Fractional flow reserve (FFR) showed hemodynamic significance (FFR=0.78) and optical coherence tomography confirmed this result with a minimal lumen area of 4.9mm². FFR-guided percutaneous intervention is reported to improve outcome in patients with stable coronary disease. However, only few data are available in cases of AS. In this condition, secondary LVH is associated with microcirculatory dysfunction, which interferes with optimal hyperemia. An elevated right atrial pressure could also modify FFR measurement. This risk of underestimation of a coronary lesion in patients with severe AS has to be taken into consideration in clinical practice.