Myocardial ischemia in aortic stenosis: insights from arterial pulse-wave dynamics after percutaneous aortic valve replacement

The impact of moderate aortic stenosis in acute myocardial infarction: A multicenter retrospective study

BACKGROUND

Aortic stenosis (AS) is associated with myocardial ischemia through different mechanisms and may impair coronary arterial flow. However, data on the impact of moderate AS in patients with acute myocardial infarction (MI) is limited.

AIMS

This study aimed to investigate the impact of moderate AS in patients presenting with acute myocardial infarction (MI).

METHODS

We conducted a retrospective analysis of all patients who presented with acute MI to all Mayo Clinic hospitals, using the Enterprise Mayo PCI Database from 2005 to 2016. Patients were stratified into two groups: moderate AS and mild/no AS. The primary outcome was all cause mortality.

RESULTS

The moderate AS group included 183 (13.3%) patients, and the mild/no AS group included 1190 (86.7%) patients. During hospitalization, there was no difference between both groups in mortality. Patients with moderate AS had higher in-hospital congestive heart failure (CHF) (8.2% vs. 4.4%, p = 0.025) compared with mild/no AS patients. At 1-year follow-up, patients with moderate AS had higher mortality (23.9% vs. 8.1%, p < 0.001) and higher CHF hospitalization (8.3% vs. 3.7%, p = 0.028). In multivariate analysis, moderate AS was associated with higher mortality at 1-year (odds ratio 2.4, 95% confidence interval [1.4-4.1], p = 0.002). In subgroup analyses, moderate AS increased all-cause mortality in STEMI and NSTEMI patients.

CONCLUSION

The presence of moderate AS in acute MI patients was associated with worse clinical outcomes during hospitalization and at 1-year follow-up. These unfavorable outcomes highlight the need for a close follow-up of these patients and for timely therapeutic strategies to best manage these coexisting conditions.

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.

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.

Long-Term Effects of Transcatheter Aortic Valve Implantation on Coronary Hemodynamics in Patients With Concomitant Coronary Artery Disease and Severe Aortic Stenosis

Background As younger patients are being considered for transcatheter aortic valve implantation (TAVI), the assessment and treatment of concomitant coronary artery disease is taking on increased importance. Methods and Results Thirteen contemporary lower-risk patients with TAVI with severe aortic stenosis (AS) and moderate-severe coronary lesions were included. Patients underwent assessment of coronary hemodynamics in the presence of severe AS (pre-TAVI), in the absence of severe AS (immediately post-TAVI), and at longer-term follow-up (6 months post-TAVI). Fractional flow reserve decreased from 0.85 (0.76-0.88) pre-TAVI to 0.79 (0.74-0.83) post-TAVI, and then to 0.71 (0.65-0.77) at 6-month follow-up (P<0.001 for all comparisons). Conversely, instantaneous wave-free ratio was not significantly different: 0.82 (0.80-0.90) pre-TAVI, 0.83 (0.77-0.88) post-TAVI, and 0.83 (0.73-0.89) at 6 months (P=0.735). These changes are explained by the underlying coronary flow. Hyperemic whole-cycle coronary flow (fractional flow reserve flow) increased from 26.36 cm/s (23.82-31.82 cm/s) pre-TAVI to 30.78 cm/s (29.70-34.68 cm/s) post-TAVI (P=0.012), to 40.20 cm/s (32.14-50.00 cm/s) at 6-month follow-up (P<0.001 for both comparisons). Resting flow during the wave-free period of diastole was not significantly different: 25.48 cm/s (21.12-33.65 cm/s) pre-TAVI, 24.54 cm/s (20.74-27.88 cm/s) post-TAVI, and 25.89 cm/s (22.57-28.96 cm/s) at 6 months (P=0.500). Conclusions TAVI acutely improves whole-cycle hyperemic coronary flow, with ongoing sustained improvements at longer-term follow-up. This enhanced response to hyperemic stimuli appears to make fractional flow reserve assessment less suitable for patients with severe AS. Conversely, resting diastolic flow is not significantly influenced by the presence of severe AS. Resting indices of coronary stenosis severity, therefore, appear to be more appropriate for this patient population, although large-scale prospective randomized trials will be required to determine the role of coronary physiology in patients with severe AS.

Determining the Predominant Lesion in Patients With Severe Aortic Stenosis and Coronary Stenoses: A Multicenter Study Using Intracoronary Pressure and Flow

Patients with severe aortic stenosis (AS) often have coronary artery disease. Both the aortic valve and the coronary disease influence the blood flow to the myocardium and its ability to respond to stress; leading to exertional symptoms. In this study, we aim to quantify the effect of severe AS on the coronary microcirculation and determine if this is influenced by any concomitant coronary disease. We then compare this to the effect of coronary stenoses on the coronary microcirculation.

Late coronary ischemıc syndromes assocıated wıth transcatheter aortıc valve ımplantatıon: A revıew of mechanıstıc and clınıcal aspects

In the past years, transcatheter aortic valve implantation (TAVI) has emerged as a promising option for the treatment of aortic valve pathologies particularly in the the presence of surgically high-risk situations. Importantly, a variety of specific procedural complications including acute coronary osteal occlusion, though very rare, has been reported in major clinical studies. However, little is known about the late impact of TAVI on coronary system at the macro and microvascular levels.

On the other hand, clinical studies as well as real life experiences have shown variable rates of acute coronary syndrome (ACS) readmissions among TAVI recipients in the short and long terms. Within this context, it may be suggested that even though late coronary ischemic events arising after TAVI, to some extent, appears to be spontaneous or attributable to certain stressors, TAVI may also have the potential to directly account for, accelerate or contribute to the evolution of these ischemic events on follow-up. Accordingly, the present review primarily focuses on potential association of TAVI with late coronary ischemic syndromes along with a particular emphasis on its mechanistic basis and clinical implications among TAVI recipients.

Regression of left ventricular hypertrophy provides an additive physiological benefit following treatment of aortic stenosis: Insights from serial coronary wave intensity analysis

AIM

Severe aortic stenosis frequently involves the development of left ventricular hypertrophy (LVH) creating a dichotomous haemodynamic state within the coronary circulation. Whilst the increased force of ventricular contraction enhances its resultant relaxation and thus increases the distal diastolic coronary "suction" force, the presence of LVH has a potentially opposing effect on ventricular-coronary interplay. The aim of this study was to use non-invasive coronary wave intensity analysis (WIA) to separate and measure the sequential effects of outflow tract obstruction relief and then LVH regression following intervention for aortic stenosis.

METHODS

Fifteen patients with unobstructed coronary arteries undergoing aortic valve intervention (11 surgical aortic valve replacement [SAVR], 4 TAVI) were successfully assessed before and after intervention, and at 6 and 12 months post-procedure. Coronary WIA was constructed from simultaneously acquired coronary flow from transthoracic echo and pressure from an oscillometric brachial cuff system.

RESULTS

Immediately following intervention, a decline in the backward decompression wave (BDW) was noted (9.7 ± 5.7 vs 5.1 ± 3.6 × 10³  W/m² /s, P < 0.01). Over 12 months, LV mass index fell from 114 ± 19 to 82 ± 17 kg/m² . Accompanying this, the BDW fraction increased to 32.8 ± 7.2% at 6 months (P = 0.01 vs post-procedure) and 34.7 ± 6.7% at 12 months (P < 0.001 vs post-procedure).

CONCLUSION

In aortic stenosis, both the outflow tract gradient and the presence of LVH impact significantly on coronary haemodynamics that cannot be appreciated by examining resting coronary flow rates alone. An immediate change in coronary wave intensity occurs following intervention with further effects appreciable with hypertrophy regression. The improvement in prognosis with treatment is likely to be attributable to both features.

Coronary Hemodynamics in Patients With Severe Aortic Stenosis and Coronary Artery Disease Undergoing Transcatheter Aortic Valve Replacement: Implications for Clinical Indices of Coronary Stenosis Severity

OBJECTIVES

In this study, a systematic analysis was conducted of phasic intracoronary pressure and flow velocity in patients with severe aortic stenosis (AS) and coronary artery disease, undergoing transcatheter aortic valve replacement (TAVR), to determine how AS affects: 1) phasic coronary flow; 2) hyperemic coronary flow; and 3) the most common clinically used indices of coronary stenosis severity, instantaneous wave-free ratio and fractional flow reserve.

BACKGROUND

A significant proportion of patients with severe aortic stenosis (AS) have concomitant coronary artery disease. The effect of the valve on coronary pressure, flow, and the established invasive clinical indices of stenosis severity have not been studied.

METHODS

Twenty-eight patients (30 lesions, 50.0% men, mean age 82.1 ± 6.5 years) with severe AS and coronary artery disease were included. Intracoronary pressure and flow assessments were performed at rest and during hyperemia immediately before and after TAVR.

RESULTS

Flow during the wave-free period of diastole did not change post-TAVR (29.78 ± 14.9 cm/s vs. 30.81 ± 19.6 cm/s; p = 0.64). Whole-cycle hyperemic flow increased significantly post-TAVR (33.44 ± 13.4 cm/s pre-TAVR vs. 40.33 ± 17.4 cm/s post-TAVR; p = 0.006); this was secondary to significant increases in systolic hyperemic flow post-TAVR (27.67 ± 12.1 cm/s pre-TAVR vs. 34.15 ± 17.5 cm/s post-TAVR; p = 0.02). Instantaneous wave-free ratio values did not change post-TAVR (0.88 ± 0.09 pre-TAVR vs. 0.88 ± 0.09 post-TAVR; p = 0.73), whereas fractional flow reserve decreased significantly post-TAVR (0.87 ± 0.08 pre-TAVR vs. 0.85 ± 0.09 post-TAVR; p = 0.001).

CONCLUSIONS

Systolic and hyperemic coronary flow increased significantly post-TAVR; consequently, hyperemic indices that include systole underestimated coronary stenosis severity in patients with severe AS. Flow during the wave-free period of diastole did not change post-TAVR, suggesting that indices calculated during this period are not vulnerable to the confounding effect of the stenotic aortic valve.

Alpha-Melanocyte-stimulating Hormone Induces Vasodilation and Exerts Cardioprotection Through the Heme-Oxygenase Pathway in Rat Hearts

Alpha–melanocyte-stimulating hormone (α-MSH) is a protein with known capacity for protection against cardiovascular ischemia–reperfusion (I/R) injury. This investigation evaluates the capacity of α-MSH to mitigate I/R effects in an isolated working rat heart model and determine the dependency of these alterations on the activity of heme oxygenase-1 (HO-1, hsp-32), a heat shock protein that functions as a major antioxidant defense molecule. Healthy male Sprague Dawley rats were used for all experiments. After treatment with selected doses of α-MSH, echocardiographic examinations were performed on live, anesthetized animals. Hearts were harvested from anesthetized rats pretreated with α-MSH and/or the HO-1 inhibitor SnPP, followed by cardiac function assessment on isolated working hearts, which were prepared using the Langendorff protocol. Induction of global ischemia was performed, followed by during reperfusion assessment of cardiac functions. Determination of incidence of cardiac arrhythmias was made by electrocardiogram. Major outcomes include echocardiographic data, suggesting that α-MSH has mild effects on systolic parameters, along with potent antiarrhythmic effects. Of particular significance was the specificity of dilatative effects on coronary vasculature, and similar outcomes of aortic ring experiments, which potentially allow different doses of the compound to be used to selectively target various portions of the vasculature for dilation.

Non-invasive coronary wave intensity analysis

Wave intensity analysis is calculated from simultaneously acquired measures of pressure and flow. Its mathematical computation produces a profile that provides quantitative information on the energy exchange driving blood flow acceleration and deceleration. Within the coronary circulation it has proven most useful in describing the wave that originates from the myocardium and that is responsible for driving the majority of coronary flow, labelled the backward decompression wave. Whilst this wave has demonstrated valuable insights into the pathogenic processes of a number of disease states, its measurement is hampered by its invasive necessity. However, recent work has used transthoracic echocardiography and an established measures of central aortic pressure to produce coronary flow velocity and pressure waveforms respectively. This has allowed a non-invasive measure of coronary wave intensity analysis, and in particular the backward decompression wave, to be calculated. It is anticipated that this will allow this tool to become more applicable and widespread, ultimately moving it from the research to the clinical domain.

Wave intensity analysis and its application to the coronary circulation

Wave intensity analysis (WIA) is a technique developed from the field of gas dynamics that is now being applied to assess cardiovascular physiology. It allows quantification of the forces acting to alter flow and pressure within a fluid system, and as such it is highly insightful in ascribing cause to dynamic blood pressure or velocity changes. When co-incident waves arrive at the same spatial location they exert either counteracting or summative effects on flow and pressure. WIA however allows waves of different origins to be measured uninfluenced by other simultaneously arriving waves. It therefore has found particular applicability within the coronary circulation where both proximal (aortic) and distal (myocardial) ends of the coronary artery can markedly influence blood flow. Using these concepts, a repeating pattern of 6 waves has been consistently identified within the coronary arteries, 3 originating proximally and 3 distally. Each has been associated with a particular part of the cardiac cycle. The most clinically relevant wave to date is the backward decompression wave, which causes the marked increase in coronary flow velocity observed at the start of the diastole. It has been proposed that this wave is generated by the elastic re-expansion of the intra-myocardial blood vessels that are compressed during systolic contraction. Particularly by quantifying this wave, WIA has been used to provide mechanistic and prognostic insight into a number of conditions including aortic stenosis, left ventricular hypertrophy, coronary artery disease and heart failure. It has proven itself to be highly sensitive and as such a number of novel research directions are encouraged where further insights would be beneficial.

Functional Assessment of Coronary Artery Disease in Patients Undergoing Transcatheter Aortic Valve Implantation

Background—

Aortic valve stenosis may influence fractional flow reserve (FFR) of concomitant coronary artery disease by causing hypertrophy and reducing the vasodilatory reserve of the coronary circulation. We sought to investigate whether FFR values might change after valve replacement.

Methods and Results—

The functional relevance of 133 coronary lesions was assessed by FFR in 54 patients with severe aortic valve stenosis before and after transcatheter aortic valve implantation (TAVI) during the same procedure. A linear mixed model was used to verify the interaction of TAVI effect with the FFR values. No significant overall change in FFR values was found before and after the aortic valve stenosis removal (0.89±0.10 versus 0.89±0.13; P =0.73). A different trend in FFR groups (positive if ≤0.8; negative if >0.8) was found after TAVI ( P for interaction <0.001). Positive FFR values worsened after TAVI (0.71±0.11 versus 0.66±0.14). Conversely, negative FFR values improved after TAVI (0.92±0.06 versus 0.93±0.07). Similarly, FFR values in coronary arteries with lesions presenting percent diameter stenosis >50 worsened after TAVI (0.84±0.12 versus 0.82±0.16; P =0.02), whereas FFR values in arteries with mild lesions (percent diameter stenosis <50) tended toward improvement after TAVI (0.90±0.07 versus 0.91±0.09; P =0.69). Functional FFR variations after TAVI changed the indication to treat the coronary stenosis in 8 of 133 (6%) lesions.

Conclusions—

Coronary hemodynamics are influenced by aortic valve stenosis removal. Nevertheless, FFR variations after TAVI are minor and crossed the diagnostic cutoff of 0.8 in a small number of patients after valve replacement. Borderline coronary lesions might become functionally significant after valve replacement, although FFR-guided interventions were infrequent even in patients with angiographically significant lesions.

Diastolic Backward-Traveling Decompression (Suction) Wave Correlates With Simultaneously Acquired Indices of Diastolic Function and Is Reduced in Left Ventricular Stunning

Background—

Wave intensity analysis can distinguish proximal (propulsion) and distal (suction) influences on coronary blood flow and is purported to reflect myocardial performance and microvascular function. Quantifying the amplitude of the peak, backwards expansion wave (BEW) may have clinical utility. However, simultaneously acquired wave intensity analysis and left ventricular (LV) pressure–volume loop data, confirming the origin and effect of myocardial function on the BEW in humans, have not been previously reported.

Methods and Results—

Patients with single-vessel left anterior descending coronary disease and normal ventricular function (n=13) were recruited prospectively. We simultaneously measured LV function with a conductance catheter and derived wave intensity analysis using a pressure–low velocity guidewire at baseline and again 30 minutes after a 1-minute coronary balloon occlusion. The peak BEW correlated with the indices of diastolic LV function: LV dP/dt min ( r s =−0.59; P =0.002) and τ ( r s =−0.59; P =0.002), but not with systolic function. In 12 patients with paired measurements 30 minutes post balloon occlusion, LV dP/dt max decreased from 1437.1±163.9 to 1299.4±152.9 mm Hg/s (median difference, −110.4 [−183.3 to −70.4]; P =0.015) and τ increased from 48.3±7.4 to 52.4±7.9 ms (difference, 4.1 [1.3–6.9]; P =0.01), but basal average peak coronary flow velocity was unchanged, indicating LV stunning post balloon occlusion. However, the peak BEW amplitude decreased from −9.95±5.45 W·m –2 /s 2 ×10 5 to −7.52±5.00 W·m –2 /s 2 ×10 5 (difference 2.43×10 5 [0.20×10 5 to 4.67×10 5 ; P =0.04]).

Conclusions—

Peak BEW assessed by coronary wave intensity analysis correlates with invasive indices of LV diastolic function and mirrors changes in LV diastolic function confirming the origin of the suction wave. This may have implications for physiological lesion assessment after percutaneous coronary intervention.

Clinical Trial Registration—

URL: http://www.isrctn.org . Unique identifier: ISRCTN42864201.

Echocardiographic determinants of LV functional improvement after transcatheter aortic valve replacement

BACKGROUND

Transcatheter aortic valve replacement (TAVR) is an established therapy in high-risk patients with severe aortic stenosis. Among patients with reduced left ventricular ejection fraction (LVEF), it is unclear which patients will derive maximal benefit from TAVR.

METHODS

Clinical and echocardiographic data of patients with severe aortic stenosis and low LVEF (≤50%) who underwent TAVR at a single institution during 2009-2013 were retrospectively analyzed. Patients were divided into 2 groups post-TAVR based on improved LV function (Group A = ΔLVEF ≥ 10%) versus persistent LV dysfunction (Group B = ΔLVEF<10%). Echocardiographic parameters were assessed for their association with LVEF change post-TAVR. Kaplan-Meier analysis was performed to generate survival estimates.

RESULTS

Of 382 patients who underwent TAVR, 60 patients had low LVEF, LV function failed to improve ≥10% in 50% of patients following the procedure (Group B). At baseline echocardiograms, Group B had higher LVEF, stroke volume (SV), SV index; and lower E, E/E', and estimated pulmonary arterial systolic pressure (PASP) compared to Group A. Higher mortality was found in Group B compared to the Group A (p = 0.003) with a significantly shorter survival (Group A = 3.3 ± 0.1 years vs Group B = 2.7 ± 0.2 years, p = 0.003). One-year event free survival was 53.3% in Group B compared to 93.3% in Group A, with a stable trend over ensuing years (5-year survival; 53.3% versus 90.0%, p = 0.003).

CONCLUSIONS

In patients undergoing TAVR with depressed LV function, those who failed to improve were more likely to have relatively higher LVEF, SV, and SVI; and lower E, E/E', and PASP at baseline. Mortality rates were found to be higher in persistent LV dysfunction group. © 2015 Wiley Periodicals, Inc.