Mechanisms of coronary microcirculatory dysfunction in patients with aortic stenosis and angiographically normal coronary arteries

Relationship of Subendocardial Perfusion to Myocardial Injury, Cardiac Structure, and Clinical Outcomes Among Patients With Hypertension

BACKGROUND

Coronary microvascular dysfunction has been implicated in the development of hypertensive heart disease and heart failure, with subendocardial ischemia identified as a driver of sustained myocardial injury and fibrosis. We aimed to evaluate the relationships of subendocardial perfusion with cardiac injury, structure, and a composite of major adverse cardiac and cerebrovascular events consisting of death, heart failure hospitalization, myocardial infarction, and stroke.

METHODS

Layer-specific blood flow and myocardial flow reserve (MFR; stress/rest myocardial blood flow) were assessed by 13N-ammonia perfusion positron emission tomography in consecutive patients with hypertension without flow-limiting coronary artery disease (summed stress score <3) imaged at Brigham and Women's Hospital (Boston, MA) from 2015 to 2021. In this post hoc observational study, biomarkers, echocardiographic parameters, and longitudinal clinical outcomes were compared by tertiles of subendocardial MFR (MFRsubendo).

RESULTS

Among 358 patients, the mean age was 70.6±12.0 years, and 53.4% were male. The median MFRsubendo was 2.57 (interquartile range, 2.08-3.10), and lower MFRsubendo was associated with older age, diabetes, lower renal function, greater coronary calcium burden, and higher systolic blood pressure (P<0.05 for all). In cross-sectional multivariable regression analyses, the lowest tertile of MFRsubendo was associated with myocardial injury and with greater left ventricular wall thickness and volumes compared with the highest tertile. Relative to the highest tertile, low MFRsubendo was independently associated with an increased rate of major adverse cardiac and cerebrovascular events (adjusted hazard ratio, 2.99 [95% CI, 1.39-6.44]; P=0.005) and heart failure hospitalization (adjusted hazard ratio, 2.76 [95% CI, 1.04-7.32; P=0.042) over 1.1 (interquartile range, 0.6-2.8) years median follow-up.

CONCLUSIONS

Among patients with hypertension without flow-limiting coronary artery disease, impaired MFRsubendo was associated with cardiovascular risk factors, elevated cardiac biomarkers, cardiac structure, and clinical events.

Effect of aortic valve replacement on myocardial perfusion and exercise capacity in patients with severe aortic stenosis

Aortic valve replacement (AVR) leads to reverse cardiac remodeling in patients with aortic stenosis (AS). The aim of this secondary pooled analysis was to assess the degree and determinants of changes in myocardial perfusion post AVR, and its link with exercise capacity, in patients with severe AS. A total of 68 patients underwent same-day echocardiography and cardiac magnetic resonance imaging with adenosine stress pre and 6-12 months post-AVR. Of these, 50 had matched perfusion data available (age 67 ± 8 years, 86% male, aortic valve peak velocity 4.38 ± 0.63 m/s, aortic valve area index 0.45 ± 0.13cm2/m2). A subgroup of 34 patients underwent a symptom-limited cardiopulmonary exercise test (CPET) to assess maximal exercise capacity (peak VO2). Baseline and post-AVR parameters were compared and linear regression was used to determine associations between baseline variables and change in myocardial perfusion and exercise capacity. Following AVR, stress myocardial blood flow (MBF) increased from 1.56 ± 0.52 mL/min/g to 1.80 ± 0.62 mL/min/g (p < 0.001), with a corresponding 15% increase in myocardial perfusion reserve (MPR) (2.04 ± 0.57 to 2.34 ± 0.68; p = 0.004). Increasing severity of AS, presence of late gadolinium enhancement, lower baseline stress MBF and MPR were associated with a greater improvement in MPR post-AVR. On multivariable analysis low baseline MPR was independently associated with increased MPR post-AVR. There was no significant change in peak VO2 post-AVR, but a significant increase in exercise duration. Change in MPR was associated with change in peak VO2 post AVR (r = 0.346, p = 0.045). Those with the most impaired stress MBF and MPR at baseline demonstrate the greatest improvements in these parameters following AVR and the magnitude of change in MPR correlated with improvement in peak VO2, the gold standard measure of aerobic exercise capacity.

Reducing Left Ventricular Wall Stress through Aortic Valve Enlargement via Transcatheter Aortic Valve Implantation in Severe Aortic Stenosis

Background: In aortic stenosis, the left ventricle exerts additional force to pump blood through the narrowed aortic valve into the downstream arterial vasculature. Adaptive hypertrophy helps to maintain wall stress homeostasis but at the expense of impaired compliance. Advanced ventricular deformation impacts the extent of functional recovery benefits achieved through transcatheter aortic valve implantation. Methods and Results: Subgroups were stratified based on output, with low-flow severe aortic stenosis defined as stroke volume index <35 mL· m-2. Before intervention, the low-flow subgroup exhibited worse effective orifice area index and arterial and global impedance, along with thinner wall thickness and larger chamber volume marginally. LV performance, including stroke volume index, ventricular elastance, and ventricular-arterial coupling, were notably inferior, consistent with worse adverse remodeling. Although the effective orifice area index was similarly augmented after TAVI, inferior recovery benefits were noted. Persistently higher wall stress and energy consumption were observed, along with poorer ventricular-arterial coupling. These changes in wall stress showed an inverse relationship with alterations in wall thickness and were proportional to changes in dimension and volume. Additionally, they were proportional to changes in left ventricular end-systolic pressure, pressure-volume area, and ventricular-arterial coupling but inversely related to ventricular end-systolic elastance. Conclusions: The study revealed that aortic valve enlargement through transcatheter aortic valve implantation reduces left ventricular wall stress in severe aortic stenosis. The reduced recovery benefits in the low-flow subgroup were evident. Wall stress could serve as a marker of mechanical benefit after the intervention.

Coronary microvascular dysfunction in childhood: An emerging pathological entity and its clinical implications

Coronary microvascular dysfunction (CMD) encompasses a spectrum of structural and functional alterations in coronary microvasculature resulting in impaired coronary blood flow and consequent myocardial ischemia without obstruction in epicardial coronary artery. The pathogenesis of CMD is complex involving both functional and structural alteration in the coronary microcirculation. In adults, CMD is predominantly discussed in context with anginal chest pain or existing ischemic heart disease and its risk factors. The presence of CMD suggests increased risk of adverse cardiovascular events independent of coronary atherosclerosis. Coronary microvascular dysfunction is also known in children but is rarely recognized due to paucity of concommitent coronary artery disease. Thus, its clinical presentation, underlying mechanism of impaired microcirculation, and prognostic significance are poorly understood. In this review article, we will overview variable CMD reported in children and delineate its emerging clinical significance.

Evaluation of Left Ventricular Function in Patients With Severe Aortic Stenosis Utilizing Automated Cardiac Motion Quantitation Techniques

OBJECTIVE

The objective of this study is to explore the patterns of alteration in left ventricular systolic function among patients with severe aortic stenosis (SAS) through the application of automatic myocardial motion quantification (aCMQ) techniques. Furthermore, we seek to ascertain dependable quantitative markers for the assessment of impaired left ventricular function in patients with SAS and an ejection fraction (EF) ≥ 60%.

METHODS

Seventy patients who underwent echocardiography and received a diagnosis of severe aortic stenosis (SAS) in the hospital from November 2021 to August 2022 were selected for the SAS group and categorized into three subgroups based on ejection fraction (EF)-SAS group with EF ≥ 60%, SAS group with EF ranging from 50% to 59%, and SAS group with EF < 50%. Concurrently, 30 healthy individuals were recruited at the hospital during the same timeframe to serve as the control group. Participants from both groups underwent standard transthoracic echocardiography to assess conventional echocardiographic parameters. Dynamic images were examined using automatic myocardial motion quantification (aCMQ) software to derive longitudinal peak strain (LPS) parameters, which were then subjected to statistical analysis.

RESULTS

In comparison to the control group participants, the measurements of ascending aorta diameter (AoD), left atrium diameter (LAD), interventricular septal end diastolic thickness (IVSd), left ventricular posterior wall end diastolic thickness (LVPWd), peak systolic velocity (Vmax), and mean pressure gradient (MPG) were significantly higher in the SAS groups (p < 0.05). When compared to participants in the SAS group with an EF ≥ 60%, the values of IVSd, LVPWd, Vmax, and MPG in the SAS group with EF ranging from 50% to 59% were significantly elevated (p < 0.05). Similarly, left ventricular end-diastolic diameter (LVEDD), the ratio of early diastolic mitral inflow velocity to early diastolic mitral annular velocity (E/e'), and the ratio of early to late diastolic mitral inflow velocities (E/A) in the SAS group with EF < 50% were significantly elevated (p < 0.05). The absolute values of longitudinal peak strain (LPS) in the SAS groups were significantly lower in comparison to those in the control group (p < 0.05). Furthermore, all measurements of left ventricular global longitudinal systolic peak strain (GLPS) showed a positive correlation with MPG, a moderate negative correlation with aortic valve area index (AVAI), and a moderate positive correlation with E/A.

CONCLUSIONS

Patients with SAS and an EF < 50% exhibited the most profound impairment in left ventricular myocardial function. Utilizing the aCMQ technique enables the precise and quantitative evaluation of the severity of impaired left ventricular systolic function in patients within the SAS group with an EF ≥ 60%.

Left ventricular strain-volume loops in bicuspid aortic valve disease: new insights in cardiomechanics

Aims

By combining temporal changes in left ventricular (LV) global longitudinal strain (GLS) with LV volume, LV strain-volume loops can assess cardiac function across the cardiac cycle. This study compared LV strain-volume loops between bicuspid aortic valve (BAV) patients and controls, and investigated the loop's prognostic value for clinical events.

Methods and results

From a prospective cohort of congenital heart disease patients, BAV patients were selected and compared with healthy volunteers, who were matched for age and sex at group level. GLS analysis from apical views was used to construct strain-volume loops. Associations with clinical events, i.e. a composite of all-cause mortality, heart failure, arrhythmias, and aortic valve replacement, were assessed by Cox regression. A total of 113 BAV patients were included (median age 32 years, 40% female). BAV patients demonstrated lower Sslope (0.21%/mL, [Q1-Q3: 0.17-0.28] vs. 0.27%/mL [0.24-0.34], P < 0.001) and ESslope (0.19%/mL [0.12-0.25] vs. 0.29%/mL [0.21-0.43], P < 0.001) compared with controls, but also greater uncoupling during early (0.48 ± 1.29 vs. 0.05 ± 1.21, P = 0.04) and late diastole (0.66 ± 1.02 vs. -0.07 ± 1.07, P < 0.001). Median follow-up duration was 9.9 [9.3-10.4] years. Peak aortic jet velocity (HR 1.22, P = 0.03), enlarged left atrium (HR 3.16, P = 0.003), E/e' ratio (HR 1.17, P = 0.002), GLS (HR 1.16, P = 0.008), and ESslope (HR 0.66, P = 0.04) were associated with the occurrence of clinical events.

Conclusion

Greater uncoupling and lower systolic and diastolic slopes were observed in BAV patients compared with healthy controls, suggesting presence of altered LV cardiomechanics. Moreover, lower ESslope was associated with clinical events, highlighting the strain-volume loop's potential as prognostic marker.

Detecting aortic valve stenosis based on the non-invasive blood pressure waveform-a proof of concept study

The incidence of aortic valve stenosis (AoS) increases with age, and once diagnosed, symptomatic severe AoS has a yearly mortality rate of 25%. AoS is diagnosed with transthoracic echocardiography (TTE), however, this gold standard is time consuming and operator and acoustic window dependent. As AoS affects the arterial blood pressure waveform, AoS-specific waveform features might serve as a diagnostic tool. Aim of the present study was to develop a novel, non-invasive, AoS detection model based on blood pressures waveforms. This cross-sectional study included patients with AoS undergoing elective transcatheter or surgical aortic valve replacement. AoS was determined using TTE, and patients with no or mild AoS were labelled as patients without AoS, while patients with moderate or severe AoS were labelled as patients with AoS. Non-invasive blood pressure measurements were performed in awake patients. Ten minutes of consecutive data was collected. Several blood pressure-based features were derived, and the median, interquartile range, variance, and the 1st and 9th decile of the change of these features were calculated. The primary outcome was the development of a machine-learning model for AoS detection, investigating multiple classifiers and training on the area under the receiver-operating curve (AUROC). In total, 101 patients with AoS and 48 patients without AoS were included. Patients with AoS showed an increase in left ventricular ejection time (0.02 s, p = 0.001), a delayed maximum upstroke in the systolic phase (0.015 s, p < 0.001), and a delayed maximal systolic pressure (0.03 s, p < 0.001) compared to patients without AoS. With the logistic regression model, a sensitivity of 0.81, specificity of 0.67, and AUROC of 0.79 were found. The majority of the population without AoS was male (85%), whereas in the population with AoS this was evenly distributed (54% males). Age was significantly (5 years, p < 0.001) higher in the population with AoS. In the present study, we developed a novel model able to distinguish no to mild AoS from moderate to severe AoS, based on blood pressure features with high accuracy. Clinical registration number: The study entailing patients with TAVR treatment was registered at ClinicalTrials.gov (NCT03088787, https://clinicaltrials.gov/ct2/show/NCT03088787 ). The study with elective cardiac surgery patients was registered with the Netherland Trial Register (NL7810, https://trialsearch.who.int/Trial2.aspx?TrialID=NL7810 ).

Characterisation of coronary microvascular dysfunction in patients with severe aortic stenosis undergoing TAVI

BACKGROUND

Microvascular resistance reserve (MRR) is a validated measure of coronary microvascular function independent of epicardial resistances.

AIMS

We sought to assess whether MRR is associated with adverse cardiac remodelling, a low-flow phenotype and extravalvular cardiac damage (EVCD) in patients with severe aortic stenosis (AS) undergoing transcatheter aortic valve implantation (TAVI).

METHODS

Invasive thermodilution-based assessment of the coronary microvascular function of the left anterior descending artery was performed in a prospective, multicentre cohort of patients undergoing TAVI. Coronary microvascular dysfunction (CMD) was defined as the lowest MRR tertile of the study cohort. Haemodynamic measurements were performed at baseline and then repeated immediately after TAVI. EVCD and markers of a low-flow phenotype were assessed with echocardiography.

RESULTS

A total of 134 patients were included in this study. Patients with low MRR were more frequently females, had a lower estimated glomerular filtration rate and a higher rate of atrial fibrillation. MRR was significantly lower in patients with advanced EVCD (median 1.80 [1.26-3.30] vs 2.50 [1.87-3.41]; p=0.038) and in low-flow, low-gradient AS (LF LG-AS) (median 1.85 [1.20-3.04] vs 2.50 [1.87-3.40]; p=0.008). Overall, coronary microvascular function tended to improve after TAVI and, in particular, MRR increased significantly after TAVI in the subgroup with low MRR at baseline. However, MRR was significantly impaired in 38 (28.4%) patients immediately after TAVI. Advanced EVCD (adjusted odds ratio 3.08 [1.22-7.76]; p=0.017) and a low-flow phenotype (adjusted odds ratio 3.36 [1.08-10.47]; p=0.036) were significant predictors of CMD.

CONCLUSIONS

In this observational, hypothesis-generating study, CMD was associated with extravalvular cardiac damage and a low-flow phenotype in patients with severe AS undergoing TAVI.

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

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

Prognostic value of high-sensitive troponin T in patients with severe aortic stenosis undergoing valve replacement surgery

Background

Aortic stenosis (AS) is a well-known cause of mortality. We aimed to assess the prognostic value of high-sensitive troponin T (hs-TnT) in symptomatic patients with severe AS and preserved left ventricular ejection fraction (LVEF) after surgical aortic valve replacement (AVR).

Patients and methods

The study recruited patients with severe symptomatic AS fulfilling the inclusion criteria in the period between April 2020 and February 2022. Comprehensive echocardiography was done. The following parameters were assessed: AS severity, LV mass index (LVMI), left atrium volume index (LAVI), and LVEF. E/e' and LVEF were calculated using the biplane method of Simpsons. Global longitudinal strain (GLS) was assessed by speckle tracking echocardiography. Peripheral blood samples were collected for hs-TnT measurement. All patients underwent surgical AVR. The patients were followed for the following 6 months for major adverse cardiovascular events (MACE). MACE was defined as cardiac death, re-admission for congestive heart failure (CHF) and fatal arrhythmia.

Results

One hundred and eight patients (mean age = 58.7 ± 7.68 years) with severe AS were recruited. Seventeen patients presented with MACE including 8 cardiac deaths. We divided the patients into two groups based on the normal hs-TnT values. The Kaplan-Meier curve revealed a statistically significant difference in MACE rate among troponin groups (log-rank test = 5.06, p = 0.025). There was significant difference between both groups regarding GLS with smaller GLS in negative hs-TnT group. In multivariate analysis, GLS and hs-TnT were significantly associated with MACE (p = 0.022 and < 0.01 respectively). The cutoff value of hs-TnT of 238.25 had a sensitivity of 70% and a specificity of 81% for predicting future MACE. There was a significant correlation between GLS and troponin (p < 0.001).

Conclusions

hs-TnT is associated with bad short-term prognosis after AVR. hs-TnT and GLS could be significant predictors for future MACE in patients with severe symptomatic AS and preserved LVEF who underwent AVR. Elevated hs-TnT and impaired GLS could set an indication of early intervention in asymptomatic severe AS.

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.

Practical Application of Coronary Physiologic Assessment: Asia-Pacific Expert Consensus Document: Part 2

Coronary physiologic assessment is performed to measure coronary pressure, flow, and resistance or their surrogates to enable the selection of appropriate management strategy and its optimization for patients with coronary artery disease. The value of physiologic assessment is supported by a large body of clinical data that has led to major recommendations in all practice guidelines. This expert consensus document aims to convey practical and balanced recommendations and future perspectives for coronary physiologic assessment for physicians and patients in the Asia-Pacific region, based on updated information in the field that includes both wire- and image-based physiologic assessment. This is Part 2 of the whole consensus document, which provides theoretical and practical information on physiologic indexes for specific clinical conditions and patient statuses.

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.

Role of nuclear cardiology in diagnosis and risk stratification of coronary microvascular disease

Coronary flow reserve (CFR) with positron emission tomography/computed tomography (PET/CT) has an important role in the diagnosis of coronary microvascular disease (CMD), aids risk stratification and may be useful in monitoring therapy. CMD contributes to symptoms and a worse prognosis in patients with coronary artery disease (CAD), nonischemic cardiomyopathies, and heart failure. CFR measurements may improve our understanding of the role of CMD in symptoms and prognosis in CAD and other cardiovascular diseases. The clinical presentation of CAD has changed. The prevalence of nonobstructive CAD has increased to about 50% of patients with angina undergoing angiography. Ischemia with nonobstructive arteries (INOCA) is recognized as an important cause of symptoms and has an adverse prognosis. Patients with INOCA may have ischemia due to CMD, epicardial vasospasm or diffuse nonobstructive CAD. Reduced CFR in patients with INOCA identifies a high-risk group that may benefit from management strategies specific for CMD. Although measurement of CFR by PET/CT has excellent accuracy and repeatability, use is limited by cost and availability. CFR measurement with single-photon emission tomography (SPECT) is feasible, validated, and would increase availability and use of CFR. Patients with CMD can be identified by reduced CFR and selected for specific therapies.

Management of coronary artery disease in patients with aortic stenosis in the era of transcatheter aortic valve replacement

Aortic stenosis (AS) is a common valve disorder among the elderly, and these patients frequently have concomitant coronary artery disease (CAD). Risk factors for calcific AS are similar to those for CAD. Historically, the treatment of these conditions involved simultaneous surgical replacement of the aortic valve (AV) with coronary artery bypass grafting. Since the advancement of transcatheter AV therapies, there have been tremendous advancements in the safety, efficacy, and feasibility of this procedure with expanding indications. This has led to a paradigm shift in our approach to the patient with AS and concomitant CAD. Data regarding the management of CAD in patients with AS are largely limited to single-center studies or retrospective analyses. This article aims to review available literature around the management of CAD in patients with AS and assist in the current understanding in approaches toward management.

Association between coronary flow and aortic stenosis during transcatheter aortic valve implantation

AIMS

In patients with aortic stenosis (AS), the coronary flow reserve decreases even in the absence of epicardial coronary artery stenosis. Systolic coronary flow reversal (SFR) reflecting reduced coronary microcirculation, often seen in patients with severe AS, has a potential negative impact on the pathogenesis of cardiac dysfunction. However, there are limited data on the relationship between the severity of AS and SFR, as well as on the benefits of transcatheter aortic valve implantation (TAVI). The aim of this study was to evaluate the relationship between the severity of AS and efficacy of TAVI in improving SFR.

METHODS AND RESULTS

Consecutive patients with AS who had undergone TAVI using transoesophageal echocardiography (TEE) from November 2020 to February 2022 were prospectively enrolled. Coronary flow in the left anterior descending artery as well as the aortic valve peak velocities, and the mean aortic valve pressure gradients (AVPGs), indicating the severity of AS, were measured using intraprocedural TEE before and after TAVI. The following parameters were measured as coronary flow: systolic and diastolic peak velocity (cm/s) and systolic and diastolic velocity-time integral (VTI) (cm). SFR was defined as the presence of a reversal coronary flow component in systole. The enrolled patients were classified into two groups according to the presence or absence of SFR before TAVI. A total of 25 patients were included: 13 had SFR and 12 who had no SFR, before TAVI. Patients with SFR had significantly higher aortic valve peak velocities (451.1 ± 45.9 vs. 372.1 ± 52.1 cm/s; P < 0.001) and mean AVPGs (49.2 ± 14.5 vs. 30.3 ± 11.6 mmHg; P = 0.002) than those without. The optimal binary cut-off aortic valve peak velocity values and the mean AVPG associated with the presence of SFR before TAVI were >410.0 cm/s (specificity, 75.0%; sensitivity, 92.3%) and >37.4 mmHg (specificity, 83.3%; sensitivity, 92.3%), respectively. After TAVI, SFR immediately disappeared in 11 of 13 patients with SFR (84.6%). Overall, the systolic coronary VTI significantly increased after TAVI (2.0 ± 4.7 vs. 6.4 ± 3.2 cm, P < 0.001), and this increase was greater in patients with SFR than in those without SFR before TAVI (interaction P = 0.035).

CONCLUSIONS

SFR was found to be associated with the severity of AS and with a greater increase in systolic coronary flow immediately after TAVI.

Comparison of vessel fractional flow reserve with invasive resting full-cycle ratio in patients with intermediate coronary lesions

BACKGROUND

Vessel fractional flow reserve (vFFR) is a novel angiography-derived index for the assessment of myocardial ischemia without the need for pressure wires and hyperemic agents. vFFR has demonstrated very good diagnostic performance compared with the hyperemic index fractional flow reserve (FFR). The aim of this study was to compare vFFR to the non-hyperemic pressure ratio resting full-cycle ratio (RFR).

METHODS

This was a retrospective, observational, single-center study of an all-comer cohort undergoing RFR assessment. Invasive coronary angiography was obtained without a dedicated vFFR acquisition protocol, and vFFR calculation was attempted in all vessels interrogated by RFR (1483 lesions of 1030 patients).

RESULTS

vFFR could be analyzed in 986 lesions from 705 patients. Median diameter stenosis was 37% (interquartile range (IQR): 30.0-44.0%), vFFR 0.86 (IQR: 0.81-0.91) and RFR 0.94 (IQR: (0.90-0.97). The correlation between vFFR and RFR was strong (r = 0.70, 95% confidence interval (CI): 0.66-0.74, p < 0.001). Using RFR ≤0.89 as reference, the sensitivity, specificity, positive predictive value, negative predictive value, and overall diagnostic accuracy for vFFR were 77%, 93%, 77%, and 92% and 89%. vFFR yielded a high area under the curve (AUC) of 0.92 (95% CI: 0.90-0.94). The good diagnostic performance of vFFR was confirmed among subgroups of patients with diabetes, severe aortic stenosis, female gender and lesions located in the left anterior descending artery.

CONCLUSION

vFFR has a high diagnostic performance taking RFR as the reference standard for evaluating the functional significance of coronary stenoses.

Heart failure and excess mortality after aortic valve replacement in aortic stenosis

INTRODUCTION

In aortic stenosis (AS), the heart transitions from adaptive compensation to an AS cardiomyopathy and eventually leads to decompensation with heart failure. Better understanding of the underpinning pathophysiological mechanisms is required in order to inform strategies to prevent decompensation.

AREAS COVERED

In this review, we therefore aim to appraise the current pathophysiological understanding of adaptive and maladaptive processes in AS, appraise potential avenues of adjunctive therapy before or after AVR and highlight areas of further research in the management of heart failure post AVR.

EXPERT OPINION

Tailored strategies for the timing of intervention accounting for individual patient's response to the afterload insult are underway, and promise to guide better management in the future. Further clinical trials of adjunctive pharmacological and device therapy to either cardioprotect prior to intervention or promote reverse remodeling and recovery after intervention are needed to mitigate the risk of heart failure and excess mortality.

Impact of coronary disease patterns, anatomical factors, micro-vascular disease and non-coronary cardiac factors on invasive coronary physiology

Invasive coronary physiology has been applied by interventional cardiologists to guide the management of coronary artery disease (CAD), with well-defined thresholds applied to determine whether CAD should be managed with optimal medical therapy (OMT) alone or OMT and percutaneous coronary intervention (PCI). There are multiple modalities in clinical use, including hyperaemic and non-hyperaemic indices. Despite endorsement in the major guidelines, there are various factors which impact and confound the readings of invasive coronary physiology, both within the coronary tree and beyond. This review article aims to summarise the mechanisms by which these factors impact invasive coronary physiology, and distinguish factors that contribute to ischaemia from confounding factors. The potential for mis-classification of ischaemic status is highlighted. Lastly, the authors identify targets for future research to improve the precision of physiology-guided management of CAD.

Long-term changes in coronary physiology after aortic valve replacement

BACKGROUND

The detrimental effects of long-standing severe aortic stenosis (AS) often include left ventricular hypertrophy (LVH) and exhaustion of coronary flow reserve (CFR), the reversibility of which is unclear after valve replacement.

AIMS

Our aims were to 1) investigate whether CFR in the left anterior descending artery (LAD) would improve following valve replacement, and if the change was related to changes in hyperaemic coronary flow (QLAD) and minimal microvascular resistance (Rμ,LAD); and 2) investigate the relationship between changes in CFR and changes in left ventricular mass (LVM) and stroke work (LVSW).

METHODS

We measured intracoronary bolus thermodilution-derived CFR, and continuous thermodilution-derived QLAD and Rμ,LAD before and 6 months after aortic valve replacement. Cardiac magnetic resonance imaging was used to quantify left ventricular anatomy and function for the calculation of LVM and LVSW.  Results: Thirty-four patients were included (17 patients had transcatheter aortic valve implantation; 14 had surgical valve replacement with a bioprosthesis and 3 with a mechanical prosthesis) who underwent invasive assessment in the LAD. CFR increased from 2.5 (interquartile range [IQR] 1.5-3.3) at baseline to 3.1 (IQR 2.2-5.1) at follow-up (p=0.005), despite no significant change in QLAD (230±106 mL/min to 250±101 mL/min; p=0.26) or Rμ,LAD (347 [IQR 247-463] to 287 [IQR 230-456]; p=0.20). When indexed for LVM, QLAD was 39% (IQR 8-98%) higher at follow-up compared with baseline (p<0.001). The improvement in CFR was correlated with ΔLVSW, r= -0.39; p=0.047.   Conclusions: CFR in the LAD increased significantly at follow-up although global hyperaemic flow and minimal microvascular resistance remained unchanged. Thus, a decrease in resting flow was the cause of CFR improvement. CFR improvement was associated with reduction in LVSW.

Incremental value of left ventricular global longitudinal strain in moderate aortic stenosis and reduced left ventricular ejection fraction

BACKGROUND

Moderate aortic stenosis (AS) often coexists with left ventricular (LV) systolic dysfunction and may affect survival through afterload mismatch. Because outcomes are ultimately driven by the condition of the LV, accurate assessment of LV performance is crucial to improve risk stratification. This study investigated the prognostic value of LV global longitudinal strain (GLS) in patients with moderate AS and reduced LV systolic dysfunction.

METHODS

Patients with moderate AS (aortic valve area 1.0-1.5 cm²) and reduced LV ejection fraction (EF) (<50%) were identified. LVGLS was evaluated with speckle-tracking echocardiography. Patients were divided into 2 groups according to an LVGLS value of 11%, based on spline curve analysis. The primary endpoint was all-cause mortality.

RESULTS

A total of 166 patients (mean age 73 ± 11 years, 71% male) were included. The cumulative 1- and 5-year mortality rates were higher in patients with LVGLS <11% (25% and 60%) versus LVGLS ≥11% (10% and 27%) (p < 0.001). On multivariable analysis, LVGLS as a continuous variable (HR 0.753; 95% CI 0.673-0.843; p < 0.001) and as a categorical variable (<11%) (HR 3.028; 95% CI 1.623-5.648; p < 0.001) were independently associated with outcomes, whereas LVEF was not. LVGLS provided additional prognostic information in patients with/without coronary artery disease and with mildly versus severely reduced LVEF. In addition, LVGLS had incremental prognostic value over established risk factors, including LVEF.

CONCLUSION

The combination of moderate AS and reduced LV systolic dysfunction is associated with a high mortality risk. LVGLS, but not LVEF, is independently associated with mortality and provides incremental prognostic value over established risk factors in patients with moderate AS and reduced LVEF.

Subendocardial and Transmural Myocardial Ischemia: Clinical Characteristics, Prevalence, and Outcomes With and Without Revascularization

BACKGROUND

Subendocardial ischemia is commonly diagnosed but not quantified by imaging.

OBJECTIVES

This study sought to define size and severity of subendocardial and transmural stress perfusion deficits, clinical associations, and outcomes.

METHODS

Regional rest-stress perfusion in mL/min/g, coronary flow reserve, coronary flow capacity (CFC), relative stress flow, subendocardial stress-to-rest ratio and stress subendocardial-to-subepicardial ratio as percentage of left ventricle were measured by positron emission tomography (PET) with rubidium Rb 82 and dipyridamole stress in serial 6,331 diagnostic PETs with prospective 10-year follow-up for major adverse cardiac events with and without revascularization.

RESULTS

Of 6,331 diagnostic PETs, 1,316 (20.7%) had severely reduced CFC with 41.4% having angina or ST-segment depression (STΔ) >1 mm during hyperemic stress, increasing with size. For 5,015 PETs with no severe CFC abnormality, 402 (8%) had angina or STΔ during stress, and 82% had abnormal subendocardial perfusion with 8.7% having angina or STΔ >1 mm during dipyridamole stress. Of 947 cases with stress-induced angina or STΔ >1 mm, 945 (99.8%) had reduced transmural or subendocardial perfusion reflecting sufficient microvascular function to increase coronary blood flow and reduce intracoronary pressure, causing reduced subendocardial perfusion; only 2 (0.2%) had normal subendocardial perfusion, suggesting microvascular disease as the cause of the angina. Over 10-year follow-up (mean 5 years), severely reduced CFC associated with major adverse cardiac events of 44.4% compared to 8.8% for no severe CFC (unadjusted P < 0.00001) and mortality of 15.2% without and 6.9% with revascularization (P < 0.00002) confirmed by multivariable Cox regression modeling. For no severe CFC, mortality was 3% with and without revascularization (P = 0.90).

CONCLUSIONS

Reduced subendocardial perfusion on dipyridamole PET without regional stress perfusion defects is common without angina, has low risk of major adverse cardiac events, reflecting asymptomatic nonobstructive diffuse coronary artery disease, or angina without stenosis. Severely reduced CFC causes angina in fewer than one-half of cases but incurs high mortality risk that is significantly reduced after revascularization.

Multimodality imaging in aortic stenosis: new diagnostic and therapeutic frontiers

The advent of transcatheter aortic valve implantation has revolutionized the treatment of calcific aortic valve stenosis. Elderly patients who were previously considered inoperable have currently an efficacious and safe therapy that provides better survival. In addition, current practice guidelines tend to recommend earlier intervention to avoid the irreversible consequences of long-lasting pressure overload caused by the stenotic aortic valve. Appropriate timing of the intervention relies significantly on imaging techniques that provide information on the severity of the aortic stenosis as well as on the hemodynamic consequences and cardiac remodeling. While left ventricular ejection fraction remains one of the main functional parameters for risk stratification in patients with severe aortic stenosis, advances in imaging techniques have provided new structural and functional parameters that allow the identification of patients who will benefit from intervention before the occurrence of symptoms or irreversible cardiac damage. Furthermore, ongoing research aiming to identify the medical therapies that can effectively halt the progression of aortic stenosis relies heavily on imaging endpoints, and new imaging techniques that characterize the metabolic activity of calcific aortic stenosis have been proposed to monitor the effects of these therapies. The present review provides an up-to-date overview of the imaging advances that characterizes the pathophysiology and that have changed the management paradigm of aortic stenosis.

Transcatheter Aortic Valve Replacement vs. Surgical Aortic Valve Replacement for Long-Term Mortality Due to Stroke and Myocardial Infarction: A Meta-Analysis during the COVID-19 Pandemic

Background and objectives: One of the leading causes of mortality and morbidity in people over the age of 50 is stroke. The acceptance of transcatheter aortic valve replacement (TAVR) as a treatment option for severe symptomatic aortic stenosis (AS) has increased as a result of numerous randomized clinical trials comparing surgical aortic valve replacement (SAVR) and TAVR in high- and intermediate-risk patients, showing comparable clinical outcomes and valve hemodynamics. Materials and Methods: An electronic search of Medline, Google Scholar and Cochrane Central was carried out from their inception to 28 September 2022 without any language restrictions. Results: Our meta-analysis demonstrated that, as compared with SAVR, TAVR was not linked with a lower stroke ratio or stroke mortality. It is clear from this that the SAVR intervention techniques applied in the six studies were successful in reducing cardiogenic consequences over time. Conclusions: A significantly decreased rate of mortality from cardiogenic causes was associated with SAVR. Additionally, when TAVR and SAVR were compared for stroke mortality, the results were nonsignificant with a p value of 0.57, indicating that none of these procedures could decrease stroke-related mortality.

Absolute coronary flow and microvascular resistance reserve in patients with severe aortic stenosis

BACKGROUND

Development of left ventricle (LV) hypertrophy in aortic stenosis (AS) is accompanied by adaptive coronary flow regulation. We aimed to assess absolute coronary flow, microvascular resistance, coronary flow reverse (CFR) and microvascular resistance reserve (MRR) in patients with and without AS.

METHODS

Absolute coronary flow and microvascular resistance were measured by continuous thermodilution in 29 patients with AS and 29 controls, without AS, matched for age, gender, diabetes and functional severity of epicardial coronary lesions. Myocardial work, total myocardial mass and left anterior descending artery (LAD)-specific mass were quantified by echocardiography and cardiac-CT.

RESULTS

Patients with AS presented a significantly positive LV remodelling with lower global longitudinal strain and global work efficacy compared with controls. Total LV myocardial mass and LAD-specific myocardial mass were significantly higher in patients with AS (p=0.001). Compared with matched controls, absolute resting flow in the LAD was significantly higher in the AS cohort (p=0.009), resulting into lower CFR and MRR in the AS cohort compared with controls (p<0.005 for both). No differences were found in hyperaemic flow and resting and hyperaemic resistances. Hyperaemic myocardial perfusion (calculated as the ratio between the absolute coronary flow subtended to the LAD, expressed in mL/min/g), but not resting, was significantly lower in the AS group (p=0.035).

CONCLUSIONS

In patients with severe AS and non-obstructive coronary artery disease, with the progression of LV hypertrophy, the compensatory mechanism of increased resting flow maintains adequate perfusion at rest, but not during hyperaemia. As a consequence, both CFR and MRR are significantly impaired.

Myocardial Perfusion and Coronary Physiology Assessment of Microvascular Dysfunction in Patients Undergoing Transcatheter Aortic Valve Implantation-Rationale and Design

The prevalence of coronary artery disease (CAD) in patients with severe aortic stenosis (AS) is 30-68%. Nevertheless, there is still not enough evidence to use invasive assessment of lesion severity, because the hemodynamic milieu of AS may impact the fractional flow reserve (FFR) and non-hyperemic indices. Therefore, the aim of the study is two-fold. First, to measure acute and long-term changes of FFR, index of microvascular resistance (IMR), and coronary flow reserve (CFR) in patients undergoing TAVI procedure. Second, to compare the diagnostic accuracy of intracoronary indices with myocardial perfusion measured by cadmium-zinc-telluride single-photon emission tomography (CZT-SPECT) and find cut-off values defining significant stenosis. We plan to enroll 40 patients eligible for TAVI with intermediate stenosis (30-70%) in the left anterior descending (LAD) coronary artery. In each patient FFR, CFR, and IMR will be measured in addition to myocardial blood flow calculated by CZT-SPECT before and either immediately after TAVI (acute cohort) or in 6 months (late cohort) after the procedure. FFR, CFR, and IMR will be matched with the results of myocardial perfusion measured by CZT-SPECT in the area of LAD. As a result, cut-off values of FFR, CFR, and IMR defining the decreased blood flow will be found.

Association between periprocedural myocardial injury and long-term all-cause mortality in patients undergoing transcatheter aortic valve replacement: a systematic review and meta-analysis

Objective. The purpose of this meta-analysis was to investigate the effect of periprocedural myocardial injury (PPMI) on long-term all-cause mortality in patients undergoing transcatheter aortic valve replacement (TAVR) and to explore potential factors associated with mortality risk. Design. The PubMed, Embase, and Cochrane Library databases were searched up to April 2022. Studies reporting the effect of PPMI on the risk of long-term all-cause mortality were included. The summary odds ratio (OR) was calculated using a random effects model. Additionally, meta-regression and subgroup analyses were conducted according to specific research characteristics to explore sources of heterogeneity. Results. Fourteen studies involving 6,415 patients who underwent TAVR showed that the occurrence of PPMI was associated with a higher risk of long-term mortality. Subgroup analysis showed that in the group of aged ≥82 years, men accounted for less than 50%, coronary artery disease patients accounted for more than 50%, and the proportion of patients with chronic kidney disease accounted for more than 60%, the proportion of patients with atria fibrillation accounted for less than 30%, and the Society of Thoracic Surgeons predicted risk of mortality score was >8 points, patients with PPMI had higher long-term all-cause mortality than those without PPMI. Conclusions. Among the patients who underwent TAVR, those who developed PPMI had higher long-term all-cause mortality.

Prognostic value of myocardial flow reserve obtained by 82-rubidium positron emission tomography in long-term follow-up after heart transplantation

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a leading cause of death following heart transplantation (HTx) and non-invasive prognostic methods in long-term CAV surveillance are needed. We evaluated the prognostic value of myocardial flow reserve (MFR) obtained by 82-rubidium (82Rb) positron emission tomography (PET).

METHODS

Recipients undergoing dynamic rest-stress 82Rb PET between April 2013 and June 2017 were retrospectively evaluated in a single-center study. Evaluation by PET included quantitative myocardial blood flow and semiquantitative myocardial perfusion imaging. Patients were grouped by MFR (MFR ≤ 2.0 vs MFR > 2.0) and the primary outcome was all-cause mortality.

RESULTS

A total of 50 patients (68% men, median age 57 [IQR: 43 to 68]) were included. Median time from HTx to PET was 10.0 (6.7 to 16.0) years. In 58% of patients CAV was documented prior to PET. During a median follow-up of 3.6 (2.3 to 4.3) years 12 events occurred. Survival probability by Kaplan-Meier method was significantly higher in the high-MFR group (log-rank P = .02). Revascularization (n = 1), new CAV diagnosis (n = 1), and graft failure (n = 4) were more frequent in low-MFR patients. No retransplantation occurred.

CONCLUSIONS

Myocardial flow reserve appears to offer prognostic value in selected long-term HTx recipients and holds promise as a non-invasive method for CAV surveillance possibly guiding management strategy.

Acute Decompensated Aortic Stenosis: State of the Art Review

Aortic stenosis (AS) is a progressive disease that carries a poor prognosis. Patients are managed conservatively until satisfying an indication for transcatheter aortic valve implantation (TAVI) or surgical aortic valve replacement (SAVR) based on AS severity and the presence of symptoms or adverse impact on the myocardium. Up to 1 in 3 TAVIs are performed for patients with acute symptoms of dyspnoea at rest, angina, and/or syncope - termed acute decompensated aortic stenosis (ADAS) and require urgent aortic valve replacement. These patients have longer hospital length of stay, undergo physical deconditioning, have a higher rate of acute kidney injury and mortality compared to stable patients with less severe symptoms. There is an urgent need to prevent ADAS and to deliver pathways to manage and improve ADAS-related outcomes. We provide here a contemporary review on epidemiological and pathophysiological aspects of ADAS, with a focus on the impact of ADAS from clinical and economic perspectives. We will offer also a global overview of the available evidence for treatment of ADAS and with priorities suggested for addressing current gaps in the literature and unmet clinical needs to improve outcomes for AS patients.

Subendocardial Infarction in Severe Bicuspid Aortic Stenosis Without Coronary Stenosis Confirmed by Contrast-enhanced Computed Tomography and Autopsy

A 59-year-old man with aortic stenosis (AS) showed cardiopulmonary arrest requiring extracorporeal circulation. Although coronary angiography did not show coronary artery stenosis, he had an elevated creatine kinase-myocardial band value of 1,298 U/L. Echocardiography revealed severe AS and global hypokinesia of the thickened myocardium. Contrast-enhanced computed tomography (CT) detected a circumferential subendocardial perfusion defect of the left ventricular myocardium. Eventually, the patient died from brain anoxia. Autopsy revealed circumferential subendocardial infarction of the left ventricular myocardium. This is the first case of circumferential subendocardial defect on CT corresponding to circumferential subendocardial infarction on autopsy in severe AS without coronary stenosis.

Sex differences in aortic stenosis: Identification of knowledge gaps for sex-specific personalized medicine

Objectives

This review summarizes sex-based differences in aortic stenosis (AS) and identifies knowledge gaps that should be addressed by future studies.

Background

AS is the most common valvular heart disease in developed countries. Sex-specific differences have not been fully appreciated, as a result of widespread under diagnosis of AS in women.

Summary

Studies including sex-stratified analyses have shown differences in pathophysiology with less calcification and more fibrosis in women's aortic valve. Women have impaired myocardial perfusion reserve and different compensatory response of the left ventricle (LV) to pressure overload, with concentric remodeling and more diffuse fibrosis, in contrast to men with more focal fibrosis and more dilated/eccentrically remodeled LV. There is sex difference in clinical presentation and anatomical characteristics, with women having more paradoxical low-flow/low-gradient AS, under-diagnosis and severity underestimated, with less referral to aortic valve replacement (AVR) compared to men. The response to therapies is also different: women have more adverse events with surgical AVR and greater survival benefit with transcatheter AVR. After AVR, women would have more favorable LV remodeling, but sex-related differences in changes in myocardial reserve flow need future research.

Conclusions

Investigation into these described sex-related differences in AS offers potential utility for improving prevention and treatment of AS in women and men. To better understand sex-based differences in pathophysiology, clinical presentation, and response to therapies, sex-specific critical knowledge gaps should be addressed in future research for sex-specific personalized medicine.

Quantitative flow ratio for evaluation of borderline coronary lesions in patients with severe aortic stenosis

INTRODUCTION AND OBJECTIVES

Quantitative flow ratio (QFR) is a novel noninvasive method for evaluating coronary physiology. However, data on the QFR in patients with aortic stenosis (AS) and coronary artery disease are scarce. Thus, we compared the diagnostic performance of the QFR with that of the resting distal to aortic coronary pressure (Pd/Pa) ratio, fractional flow reserve (FFR), and instantaneous wave-free ratio (iFR), as well as angiographic indices.

METHODS

A total of 221 AS patients with 416 vessels undergoing FFR/iFR measurements were enrolled in the study.

RESULTS

The mean percent diameter stenosis (%DS) was 58.6%±13.4% and the mean Pd/Pa ratio, FFR, iFR, and QFR were 0.95±0.03, 0.85±0.07, 0.90±0.04, and 0.84±0.07, respectively. A FFR ≤ 0.80 was noted in 26.0% of interrogated vessels, as well as an iFR ≤ 0.89 in 33.2% and QFR ≤ 0.80 in 31.7%. The QFR had better agreement with FFR (intraclass correlation coefficient [ICC], 0.96; 95% confidence interval [95%CI], 0.95-0.96) than with the iFR (ICC, 0.79; 95%CI, 0.75-0.82) and Pd/Pa ratio (ICC, 0.52; 95%CI, 0.44-0.58). In addition, the QFR showed better diagnostic accuracy (98.6% vs 94.2%; P <.001) and discriminant function (area under the curve=0.996 vs 0.988; P <.001) when the iFR was used as the reference instead of FFR.

CONCLUSIONS

In patients with AS, the QFR has good agreement with both FFR and iFR. However, the agreement appears to be even better when the iFR is used as the reference, presumably due to the complex nature of the coronary physiology in the assessment of coronary artery disease in patients with severe AS.

Microcirculatory Function in Nonhypertrophic and Hypertrophic Myocardium in Patients With Aortic Valve Stenosis

Background Left ventricular hypertrophy (LVH) has often been supposed to be associated with abnormal myocardial blood flow and resistance. The aim of this study was to evaluate and quantify the physiological and pathological changes in myocardial blood flow and microcirculatory resistance in patients with and without LVH attributable to severe aortic stenosis. Methods and Results Absolute coronary blood flow and microvascular resistance were measured using a novel technique with continuous thermodilution and infusion of saline. In addition, myocardial mass was assessed with cardiac magnetic resonance imaging. Fifty-three patients with aortic valve stenosis were enrolled in the study. In 32 patients with LVH, hyperemic blood flow per gram of tissue was significantly decreased compared with 21 patients without LVH (1.26±0.48 versus 1.66±0.65 mL·min^-1·g^-1; P=0.018), whereas minimal resistance indexed for left ventricular mass was significantly increased in patients with LVH (63 [47-82] versus 43 [35-63] Wood Units·kg; P=0.014). Conclusions Patients with LVH attributable to severe aortic stenosis had lower hyperemic blood flow per gram of myocardium and higher minimal myocardial resistance compared with patients without LVH.

Feasibility and Comparison of Resting Full-Cycle Ratio and Computed Tomography Fractional Flow Reserve in Patients with Severe Aortic Valve Stenosis

Background: Computed tomography derived Fractional Flow Reserve (CT-FFR) has been shown to decrease the referral rate for invasive coronary angiography (ICA). The purpose of the study was to evaluate the diagnostic performance of CT-FFR compared to hyperemia-free index Resting Full-cycle Ratio (RFR) in patients with relevant aortic stenosis (AS) and intermediate coronary stenosis. Methods: 41 patients with 46 coronary lesions underwent ICA with quantitative coronary angiography (QCA), pressure wire assessment and routine pre-transcatheter aortic valve replacement (TAVR) computed tomography (CT). CT-FFR analysis was performed using prototype on-site software. Results: RFR showed a significant correlation with CT-FFR (Pearson’s correlation, r = 0.632, p < 0.001). On a per-lesion basis, diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of CT-FFR were 82.6% (95% CI 68.6−92.2), 69.6% (95% CI 47.1−86.8), 95.7% (95% CI  78.1−99.9), 94.1% (95% CI 69.8−99.1), and 75.9% (95% CI 62.7−85.4), respectively. The optimal cutoff value of the CT-FFR for RFR ≤ 0.89 prediction was 0.815. The area under the receiver curve showed a larger area under the curve for CT-FFR (0.87; 95% CI 0.75−0.98) compared with CTA stenosis of ≥50% (0.54, 95% CI 0.38−0.71), CTA ≥ 70% (0.72, 95% CI 0.57−0.87) and QCA ≥ 50% (0.67, 95% CI 0.52−0.83). Conclusions: CT-FFR assessed by routine pre-TAVR CT is safe and feasible and shows a significant correlation with RFR in patients with AS. CT-FFR is superior to QCA ≥ 50%, CT ≥ 50% and CT ≥ 70% in assessing the hemodynamic relevance of intermediate coronary lesions. Thus, CT-FFR has the potential to guide revascularization in patients with AS.

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.

Left ventricular function assessment after aortic and renal intervention in Takayasu arteritis by speckle tracking echocardiography: a pilot study

Background

Overt left ventricular (LV) dysfunction and congestive heart failure are known entities in Takayasu arteritis (TA). Subclinical LV dysfunction may develop in these patients despite normal LV ejection fraction (LVEF). Moreover, effect of treatment of aortic or renal artery narrowing in such patients is unknown.

Methods

This study included 15 angiographically confirmed TA patients undergoing aortic and/or renal intervention. A comprehensive clinical, biochemical and echocardiographic (2-dimensional, speckle tracking and tissue doppler imaging) evaluation were done at baseline, 72 h, and six months post intervention.

Results

Six patients (40%) had reduced LVEF (<50%) at baseline while rest 9 (60%) patients had reduced global longitudinal strain (GLS) but normal EF. Diastolic filling pattern was abnormal in all the patients. In patients with baseline reduced EF, mean EF improved from 24.62 ± 12.14% to 45.6 ± 9.45% (p = 0.001), E/e’ ratio decreased from 15.15 ± 3.19 to 10.8 ± 2.56 (p = 0.005) and median NT pro BNP decreased from 1673 pg/ml (970–2401 pg/ml) to 80 pg/ml (40–354 pg/ml) (p = 0.001) at 6 months after interventional procedure. In patients with baseline normal EF, median NT pro BNP decreased from 512 pg/ml (80–898.5 pg/ml) to 34 pg/ml (29–70.8 pg/ml) (p < 0.01), mean GLS improved from −8.80 ± 0.77% to −16.3 ± 0.78% (p < 0.001) and mean E/e’ decreased from 12.93 ± 2.63 to 7.8 ± 2.73 (p = 0.005) at 6 months follow up.

Conclusion

LV dysfunction is common in patients with TA and obstructive lesions in aorta or renal arteries. GLS can be used to assess subclinical systolic dysfunction in these patients. Timely intervention can improve LV dysfunction and can even reverse the subclinical changes.

Coronary blood flow in heart failure: cause, consequence and bystander

Heart failure is a clinical syndrome where cardiac output is not sufficient to sustain adequate perfusion and normal bodily functions, initially during exercise and in more severe forms also at rest. The two most frequent forms are heart failure of ischemic origin and of non-ischemic origin. In heart failure of ischemic origin, reduced coronary blood flow is causal to cardiac contractile dysfunction, and this is true for stunned and hibernating myocardium, coronary microembolization, myocardial infarction and post-infarct remodeling, possibly also for the takotsubo syndrome. The most frequent form of non-ischemic heart failure is dilated cardiomyopathy, caused by genetic mutations, myocarditis, toxic agents or sustained tachyarrhythmias, where alterations in coronary blood flow result from and contribute to cardiac contractile dysfunction. Hypertrophic cardiomyopathy is caused by genetic mutations but can also result from increased pressure and volume overload (hypertension, valve disease). Heart failure with preserved ejection fraction is characterized by pronounced coronary microvascular dysfunction, the causal contribution of which is however not clear. The present review characterizes the alterations of coronary blood flow which are causes or consequences of heart failure in its different manifestations. Apart from any potentially accompanying coronary atherosclerosis, all heart failure entities share common features of impaired coronary blood flow, but to a different extent: enhanced extravascular compression, impaired nitric oxide-mediated, endothelium-dependent vasodilation and enhanced vasoconstriction to mediators of neurohumoral activation. Impaired coronary blood flow contributes to the progression of heart failure and is thus a valid target for established and novel treatment regimens.

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.

Calcific aortic valve disease: from molecular and cellular mechanisms to medical therapy

Calcific aortic valve disease (CAVD) is a highly prevalent condition that comprises a disease continuum, ranging from microscopic changes to profound fibro-calcific leaflet remodelling, culminating in aortic stenosis, heart failure, and ultimately premature death. Traditional risk factors, such as hypercholesterolaemia and (systolic) hypertension, are shared among atherosclerotic cardiovascular disease and CAVD, yet the molecular and cellular mechanisms differ markedly. Statin-induced low-density lipoprotein cholesterol lowering, a remedy highly effective for secondary prevention of atherosclerotic cardiovascular disease, consistently failed to impact CAVD progression or to improve patient outcomes. However, recently completed phase II trials provide hope that pharmaceutical tactics directed at other targets implicated in CAVD pathogenesis offer an avenue to alter the course of the disease non-invasively. Herein, we delineate key players of CAVD pathobiology, outline mechanisms that entail compromised endothelial barrier function, and promote lipid homing, immune-cell infiltration, and deranged phospho-calcium metabolism that collectively perpetuate a pro-inflammatory/pro-osteogenic milieu in which valvular interstitial cells increasingly adopt myofibro-/osteoblast-like properties, thereby fostering fibro-calcific leaflet remodelling and eventually resulting in left ventricular outflow obstruction. We provide a glimpse into the most promising targets on the horizon, including lipoprotein(a), mineral-binding matrix Gla protein, soluble guanylate cyclase, dipeptidyl peptidase-4 as well as candidates involved in regulating phospho-calcium metabolism and valvular angiotensin II synthesis and ultimately discuss their potential for a future therapy of this insidious disease.

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.

Dynamic Changes in Coronary Flow Pattern During Transcatheter Aortic Valve Replacement in Severe Aortic Stenosis

Coronary flow reserve in patients with severe aortic stenosis decreases even in the absence of coronary stenosis. In this case, the dynamic changes in the coronary flow pattern around transcatheter aortic valve replacement were observed by periprocedural transesophageal echocardiography. (Level of Difficulty: Intermediate.).

Association of Myocardial Blood Flow Reserve With Adverse Left Ventricular Remodeling in Patients With Aortic Stenosis: The Microvascular Disease in Aortic Stenosis (MIDAS) Study

Importance

Impaired myocardial flow reserve (MFR) and stress myocardial blood flow (MBF) on positron emission tomography (PET) myocardial perfusion imaging may identify adverse myocardial characteristics, including myocardial stress and injury in aortic stenosis (AS).

Objective

To investigate whether MFR and stress MBF are associated with LV structure and function derangements, and whether these parameters improve after aortic valve replacement (AVR).

Design, Setting, and Participants

In this single-center prospective observational study in Boston, Massachusetts, from 2018 to 2020, patients with predominantly moderate to severe AS underwent ammonia N13 PET myocardial perfusion imaging for myocardial blood flow (MBF) quantification, resting transthoracic echocardiography (TTE) for assessment of myocardial structure and function, and measurement of circulating biomarkers for myocardial injury and wall stress. Evaluation of health status and functional capacity was also performed. A subset of patients underwent repeated assessment 6 months after AVR. A control group included patients without AS matched for age, sex, and summed stress score who underwent symptom-prompted ammonia N13 PET and TTE within 90 days.

Exposures

MBF and MFR quantified on ammonia N13 PET myocardial perfusion imaging.

Main Outcomes and Measures

LV structure and function parameters, including echocardiographic global longitudinal strain (GLS), circulating high-sensitivity troponin T (hs-cTnT), N-terminal pro-B-type natriuretic peptide (NT-pro BNP), health status, and functional capacity.

Results

There were 34 patients with AS (1 mild, 9 moderate, and 24 severe) and 34 matched control individuals. MFR was independently associated with GLS and LV ejection fraction, (β,-0.31; P = .03; β, 0.41; P = .002, respectively). Stress MBF was associated with hs-cTnT (unadjusted β, -0.48; P = .005) and log NT-pro BNP (unadjusted β, -0.37; P = .045). The combination of low stress MBF and high hs-cTnT was associated with higher interventricular septal thickness in diastole, relative wall thickness, and worse GLS compared with high stress MBF and low hs-cTnT (12.4 mm vs 10.0 mm; P = .008; 0.62 vs 0.46; P = .02; and -13.47 vs -17.11; P = .006, respectively). In 9 patients studied 6 months after AVR, mean (SD) MFR improved from 1.73 (0.57) to 2.11 (0.50) (P = .008).

Conclusions and Relevance

In this study, in AS, MFR and stress MBF were associated with adverse myocardial characteristics, including markers of myocardial injury and wall stress, suggesting that MFR may be an early sensitive marker for myocardial decompensation.

Hyperemic versus non-hyperemic indexes for coronary physiology assessment in patients with severe aortic stenosis

PURPOSE

Recent data suggests that fractional flow reserve (FFR) may underestimate intermediate coronary stenosis in the presence of severe aortic stenosis (AS), whereas instantaneous wave-free ratio (iFR) values may remain similar after treatment of AS, yet the evidence still lacks to use iFR as the reference. We aimed to compare FFR/iFR values in the AS setting.

MATERIALS AND METHODS

The functional significance of 416 coronary lesions in 221 patients with severe AS was investigated with iFR and FFR.

RESULTS

The diagnostic agreement between iFR and FFR has been tested, using the cut-off value of 0.89 for iFR and 0.80 for FFR. The mean diameter stenosis was 58.6 ​± ​13.4% with FFR of 0.85 ​± ​0.07 and iFR of 0.90 ​± ​0.04. FFR ≤0.80 was identified in 26.0% and iFR≤0.89 in 33.2% of interrogated vessels. Good agreement between iFR and FFR was confirmed (Intraclass Correlation Coefficient 0.83 [95%CI 0.79-0.85]). The overall diagnostic accuracy (AUC in ROC analysis) of FFR in detecting iFR≤0.89 was 0.997 (95%CI 0.986 to 1.000; p<0.001) and of iFR in detecting FFR≤0.80 was 0.995 (95%CI 0.983 to 0.999; p<0.001). The optimal cut-off value for FFR to detect iFR≤0.89 was 0.82 with sensitivity, specificity, and accuracy of 97.1%, 98.9%, and 97.7%, respectively, and for IFR to detect FFR≤0.80 was 0.88 with sensitivity, specificity, and accuracy of 99.1%, 95.8%, and 97.4%, respectively.

CONCLUSION

In the presence of AS, FFR has good agreement with iFR. However, the optimal FFR/iFR threshold to identify iFR≤0.89/FFR≤0.80 may be different from the standard thresholds of ischemia.