Impact of global hemodynamic load on exercise capacity in aortic stenosis

Clinical significance and prognostic value of ST segment depression on ECG during exercise treadmill test in asymptomatic patients with moderate or severe aortic stenosis

Objectives. In patients with asymptomatic moderate or severe aortic stenosis (AS), exercise testing is used for evaluating the need for aortic valve intervention. Expert opinions about the clinical significance and prognostic value of ST segment depression on electrocardiography (ECG) during exercise testing in AS is conflicting and there are no large studies exploring this issue. We aimed to explore the association of ST segment depression >5 mm during exercise treadmill test (ETT) with all-cause mortality, aortic valve replacement (AVR) or cardiac-related hospitalization. Design. We performed a retrospective analysis of prospectively collected data of a total of 315 patients (mean age 65 ± 12 years, 67% men) with asymptomatic moderate (n = 209; 66%) or severe (n = 106; 34%) AS. All patients underwent clinical evaluation, echocardiography and ETT. Results. During a mean follow-up of 34.9 ± 34.6 months, 29 (9%) patients died and 235 (74%) underwent AVR. The prevalence of ST segment depression (>5 mm) was 13% (n = 41) in the total study population and was comparable in patients with revealed symptoms (17.6%, n = 16) versus without revealed symptoms (11.3%, n = 25; p = .132). ST segment depression on ETT was strongly associated with aortic valve area. In univariate Cox regression analysis, ST segment depression was not associated with cardiac related hospitalizations (HR 1.65; 95% CI 0.89-3.10, p = .113), all-cause mortality (HR 1.37; 95% CI 0.47-3.98, p = .564) or AVR (HR 1.30; 95% CI 0.89-1.91, p = .170). Conclusion. In patients with moderate or severe AS, ST segment depression during ETT is non-specific, carries no prognostic risk and should be used with caution in the clinical interpretation of exercise test.

Exercise Testing in Aortic Stenosis: Safety, Tolerability, Clinical Benefits and Prognostic Value

Background: Routine exercise testing in asymptomatic patients with valvular heart disease (VHD) better classifies the hemodynamic severity of valve stenosis or regurgitation, and describes the symptomatic status and functional capacity of the patient. This is crucial for planned surveillance and optimal timing of surgery, particularly for aortic stenosis (AS), because once symptoms occur, there is a sharp increase in the risk of sudden death unless valve intervention is performed. Purpose: To conduct a focused clinical review on the benefits of exercise testing in patients with AS. Methods: The electronic database PubMed was systematically searched for relevant retrospective and prospective cohort studies reporting on the safety, feasibility and tolerability of exercise testing in VHD, with a special focus on AS. Results and conclusions: In patients with significant AS, exercise testing is safe, feasible and reveals symptoms in a significant proportion of patients. In addition, serial testing has incremental prognostic value over a baseline test alone. Exercise testing in patients with AS is underused and should be performed routinely to refine the hemodynamic severity of AS.

Left Ventricular Remodeling in Degenerative Aortic Valve Stenosis

Aortic stenosis was once considered a pure isolated valve obstacle challenging left ventricle driving force of contraction and flow generation. Left ventricular (LV) adaptation was merely interpreted as a uniform hypertrophic response to increased afterload. However, in these last 2 decades cardiac imaging research and some histopathology correlation studies brought insight towards the complex interaction between the vasculature, the valve and the myocardium. Verily, LV remodeling in this setting is a complex multidetermined process that goes further beyond myocardial hypertrophy. Ultrastructural changes involving both diffuse and replacement fibrosis of the myocardium take part and might explain the transition of clinical phenotypes with distinct prognosis, from compensated hypertrophy to LV maladaptive dysfunction and heart failure. Presently, the combined appropriate use of echocardiography and cardiac magnetic resonance may better assess the global LV afterload, hypertrophy and geometric remodeling, global and regional LV function, beyond ejection fraction, and structural changes that include the fibrotic burden of the myocardium. As a whole these may not only better stratify individual risk of disease progression but also identify patients benefiting from earlier valve intervention. In this paper, we review the maladaptive response of the LV to chronic pressure overload, describing the different signaling pathways and mechanisms that underly both hypertrophy and remodeling. Histomorphology changes in this setting are described and we try to make sense of the use of new imaging tools for LV characterization.

Sex-differences in aortic stenosis: Effect on functional capacity and prognosis

BACKGROUND

The patterns of left ventricular (LV) remodeling in aortic stenosis (AS) are different in men and women. We aimed to assess whether there were also sex differences in measurements obtained on exercise testing.

METHODS

Echocardiography and ETT (modified Bruce) were performed at presentation in 316 patients with moderate or severe AS. An early rapid rise in heart rate (RR-HR) during ETT was defined as achieving at least 85% of target heart rate or ≥50% increase from baseline within the first 6 min.

RESULTS

Mean age was 66 ± 12 years in men (n = 212) and 65 ± 12 years in women (n = 104) (p = NS). Men walked longer than women on the treadmill (10.4 ± 4.3 vs. 8.2 ± 4.2 min, p < 0.001) and achieved higher METs (9.2 ± 4.5 vs. 7.6 ± 4.3, p < 0.001), but both sexes achieved similar levels of peak heart rate and blood pressure. During a mean follow up of 34.9 ± 34.6 months, 29 deaths occurred (20 in men and 9 in women, p = 0.821). Age and body mass index were strong determinants of lower METs in men, but not in women, while Zva was a determinant in women but not in men. RR-HR was a strong determinant of lower METs in both sexes. Event-free survival was significantly lower in men with RR-HR but not in women.

CONCLUSION

Exercise capacity was lower in women than men, and the determinants of exercise capacity differed. An RR-HR was a strong determinant of lower METs in both sexes, but predicted all-cause mortality only in men.

The importance of contractile reserve in predicting exercise tolerance in asymptomatic patients with severe aortic stenosis

BACKGROUND

Mortality dramatically rises with the onset of symptoms in patients with severe aortic stenosis (AS). Surgery is indicated when symptoms become apparent or when there is ventricular decompensation. Cardiopulmonary exercise testing (CPET) in combination with exercise echocardiography can unmask symptoms and provides valuable information regarding contractile reserve. The aim of the present study was to determine the prevalence of reduced exercise tolerance and the parameters predicting adverse cardiovascular events.

METHODS

Thirty-two patients with asymptomatic severe AS were included in this study. Patients were followed up as part of an enhanced surveillance clinic.

RESULTS

Age was 69 ± 15.7 years, 75% of patients were male. Patients had a raised NT-ProBNP of 301 pg/mL. VO2peak was 19.5 ± 6.2 mL/kg/min. Forty-one percent of patients had a reduced %VO2peak and this predicted unplanned cardiac hospitalisation (P = 0.005). Exercise systolic longitudinal velocity (S') and age were the strongest independent predictors for VO2peak (R 2 = 0.76; P < 0.0001). Exercise S' was the strongest independent predictor for NT-ProBNP (R 2 = 0.48; P = 0.001).

CONCLUSION

A large proportion of patients had a lower than predicted VO2peak. The major determinant of exercise and NT-ProBNP is the ability of the left ventricle (LV) to augment S' on exercise rather than the severity of aortic valve obstruction or resting structural remodelling of the LV. Reduced exercise tolerance and more adverse remodelling, rather than valve obstruction predicted unplanned hospitalisation. This study demonstrates that for those patients, in whom a watchful waiting is an agreed strategy, a detailed assessment should be undertaken including CPET, exercise echocardiography and biomarkers to ensure those with exercise limitation and risk of decompensation are detected early and treated appropriately.

The effect of minimally invasive surgical aortic valve replacement on postoperative pulmonary and skeletal muscle function

NEW FINDINGS

What is the central question of this study? How does surgical aortic valve replacement affect cardiopulmonary and muscle function during exercise? What is the main finding and its importance? Early after the surgical replacement of the aortic valve a significant decline in pulmonary function was observed, which was followed by a decline in skeletal muscle function in the subsequent weeks of recovery. These date reiterate, despite restoration of aortic valve function, the need for a tailored rehabilitation programme for the respiratory and peripheral muscular system.

ABSTRACT

Suboptimal post-operative improvements in functional capacity are often observed after minimally invasive aortic valve replacement (mini-AVR). It remains to be studied how AVR affects the cardiopulmonary and skeletal muscle function during exercise to explain these clinical observations and to provide a basis for improved/tailored post-operative rehabilitation. Twenty-two patients with severe aortic stenosis (AS) (aortic valve area (AVA) <1.0 cm²) were pre-operatively compared to 22 healthy controls during submaximal constant-workload endurance-type exercise for oxygen uptake ( V ̇ O 2 ), carbon dioxide output ( V ̇ C O 2 ), respiratory gas exchange ratio, expiratory volume ( V ̇ E ), ventilatory equivalents for O₂ ( V ̇ E / V ̇ O 2 ) and CO₂ ( V ̇ E / V ̇ C O 2 ), respiratory rate (RR), tidal volume (V_t ), heart rate (HR), oxygen pulse ( V ̇ O 2 /HR), blood lactate, Borg ratings of perceived exertion (RPE) and exercise-onset V ̇ O 2 kinetics. These exercise tests were repeated at 5 and 21 days after AVR surgery (n = 14), along with echocardiographic examinations. Respiratory exchange ratio and ventilatory equivalents ( V ̇ E / V ̇ O 2 and V ̇ E / V ̇ C O 2 ) were significantly elevated, V ̇ O 2 and V ̇ O 2 /HR were significantly lowered, and exercise-onset V ̇ O 2 kinetics were significantly slower in AS patients vs. healthy controls (P < 0.05). Although the AVA was restored by mini-AVR in AS patients, V ̇ E / V ̇ O 2 and V ̇ E / V ̇ C O 2 further worsened significantly within 5 days after surgery, accompanied by elevations in Borg RPE, V ̇ E and RR, and lowered V_t . At 21 days after mini-AVR, exercise-onset V ̇ O 2 kinetics further slowed significantly (P < 0.05). A decline in pulmonary function was observed early after mini-AVR surgery, which was followed by a decline in skeletal muscle function in the subsequent weeks of recovery. Therefore, a tailored rehabilitation programme should include training modalities for the respiratory and peripheral muscular system.

Is left ventricular hypertrophy a friend or foe of patients with aortic stenosis?

Left ventricular hypertrophy (LVH) is traditionally considered a physiological compensatory response to LV pressure overload, such as hypertension and aortic stenosis (AS), in an effort to maintain LV systolic function in the face of an increased afterload. According to the Laplace law, LV wall thickening lowers LV wall stress, which in turn would be helpful to preserve LV systolic performance. However, numerous studies have challenged the notion of LVH as a putative beneficial adaptive mechanism. In fact, the magnitude of LVH is associated with higher cardiovascular morbidity and mortality, especially when LVH is disproportionate to LV afterload. We have briefly reviewed: first, the importance of non-valvular factors, beyond AS severity, for total LV afterload and symptomatic status in AS patients; second, associations of excessive LVH with LV dysfunction and adverse outcome in AS; third, prognostic relevance of the presence or absence of pre-operative LVH in patients referred for aortic valve surgery; fourth, time course, determinants and prognostic implications of LVH regression and LV function recovery after surgical valve replacement and transcatheter aortic valve implantation (TAVI) with a focus on TAVI-specific effects; fifth, the potential of medical therapy to modulate LVH before and after surgical or interventional treatment for severe AS, a condition perceived as a relative contraindication to renin-angiotensin system blockade.

Stress Testing in Asymptomatic Aortic Stenosis

Aortic stenosis is 1 of the most common heart valve diseases among adults. When symptoms develop, prognosis is poor, and current guidelines recommend prompt aortic valve replacement. Depending of the severity of the aortic stenosis and the presence of concomitant heart disease and medical comorbidities, stress testing represents a reasonable strategy to help better risk stratify asymptomatic patients. The present report provides a comprehensive review of the current available data on stress testing in aortic stenosis and subsequently summarizes its potential for guiding the optimal timing of aortic valve replacement.

Assessment of aortic valve disease - a clinician oriented review

Aortic valve disease [aortic stenosis (AS) and aortic regurgitation (AR)] represents an important global health problem; when severe, aortic valve disease carries poor prognosis. For AS, aortic valve replacement, either surgical or interventional, may provide definite treatment in carefully selected patients. For AR, valve surgery (either replacement or - in selected cases - aortic valve repair) remains the gold standard of care. To properly identify those patients who are candidates for surgery, the clinician has to carefully assess the severity of valve disease with an understanding of the potential pitfalls involved in these assessments. This review focuses on the practical issues concerning the evaluation of patients with AS and AR from a general cardiologist’s perspective. The most important issues regarding the documentation of the severity of AS and AR are summarized. More specific issues, such as the role of stress echocardiography, other imaging techniques and details regarding the treatment options (medical, surgical, or interventional), are mentioned briefly.

Noninvasive Coronary Flow Reserve Predicts Response to Exercise in Asymptomatic Severe Aortic Stenosis

BACKGROUND

In patients with asymptomatic aortic stenosis (AS), exercise stress echocardiography (ESE) provides additional prognostic information beyond baseline. The coronary flow velocity reserve (CFVR) is impaired in AS, but its link with exertion is unknown in this setting. The aim of this study was to test the hypothesis that CFVR could predict exercise capacity and abnormal exercise test results in AS.

METHODS

Noninvasive CFVR and symptom-limited semisupine ESE were prospectively performed the same day in 43 patients with asymptomatic isolated severe AS (mean age, 68.5 ± 11 years; 26% women; mean aortic valve area, 0.8 ± 0.16 cm²; mean left ventricular ejection fraction, 70 ± 7%). CFVR was performed in the distal part of the left anterior descending coronary artery using intravenous adenosine infusion (140 μg/kg/min over 2 min), and ESE was performed at an initial workload of 25 W with a 20- to 25-W increase at 2-min intervals. An abnormal result on ESE was defined as onset of symptoms at <75% of maximum predicted workload, electrocardiographic ST-segment depression ≥2 mm during exercise, increase of systolic blood pressure < 20 mm Hg or decrease in blood pressure, and complex ventricular arrhythmia. Seventeen patients with isolated severe asymptomatic AS, unable to exercise because of extracardiac conditions, served as a comparative group.

RESULTS

Resting, hyperemic left anterior descending coronary artery flow velocity and CFVR (2.45 ± 0.8 vs 2.4 ± 0.8) were similar between the group unable to perform ESE and the ESE group (P = NS for all). Compared with patients with normal results on ESE, those with abnormal results on ESE (n = 22) were older, had higher E/e' ratios, had higher resting left anterior descending coronary artery flow velocities (39 ± 12 vs 31 ± 8 cm/sec), and had lower CFVR (2.01 ± 0.3 vs 2.85 ± 0.7; P < .01 for all). Furthermore, CFVR was significantly correlated with age, changes in transvalvular pressure gradient and left ventricular ejection fraction with exercise, workload (in watts), and exercise duration (P < .05 for all). After adjusting for other variables, CFVR remained independently correlated with exercise duration, workload, and abnormal results on ESE (P < .01 for all). On receiver operating characteristic curve analysis, CFVR < 2.3 was the best cutoff to predict abnormal results on ESE (area under the curve = 0.88 ± 0.06, P < .01).

CONCLUSIONS

In patients with asymptomatic severe AS, noninvasive CFVR is correlated with exercise duration and workload, and low CFVR predicts abnormal results on ESE with good accuracy.

Exercise Testing and Stress Imaging in Aortic Valve Disease

OPINION STATEMENT

Aortic valve disease and especially aortic stenosis (AS) is a growing cardiac pathology. Aortic valve replacement (AVR) is still the only treatment with proven benefit on survival in symptomatic patients and in patients with a left ventricular ejection fraction (LVEF) <50%. The benefit of prophylactic AVR in asymptomatic patients is still unproven. Once symptoms develop, the prognosis worsens. Exercise testing has emerged as a tool to unmask the "pseudo-asymptomatic" patients with AS (those without self-reporting symptoms), to link "exercise induced dyspnea" more confidently and more objectively to aortic valve disease and to allow for a safe "watchful waiting strategy" in "pseudo-symptomatic" patients (those with dyspnea unrelated to aortic valve disease). In cases in which exercise testing is unable to link dyspnea to aortic valve disease, exercise stress echocardiography and cardiopulmonary exercise testing may be helpful. Whatever the results of exercise testing with regard to symptom development, an increase in mean aortic valve pressure gradient >18-20 mmHg was associated with an increased risk of cardiac related events in severe AS patients (class IIb indication for AVR in the ESC guidelines). The decrease in LVEF during exercise as well as the development of exercise induced pulmonary hypertension, as revealed by exercise stress echocardiography, may be also useful in the risk stratification of these asymptomatic patients with severe AS. Data on the role of exercise echocardiography in asymptomatic severe aortic regurgitation patients is still scarce and further studies are needed. It seems that an exercise induced decrease in LVEF by 5% may be a better predictor of LV systolic dysfunction after AVR in asymptomatic patients or in patients with minimal symptoms. Exercise testing and exercise echocardiography are safe in the asymptomatic patients with aortic disease, provide useful clinical information that may help in risk assessment of these complicated patients and their use should be encouraged especially in heart valve clinics.

Increased valvulo-arterial impedance differently impacts left ventricular longitudinal, circumferential, and radial function in patients with aortic stenosis: A speckle tracking echocardiography study

BACKGROUND

In aortic stenosis (AS), the left ventricle (LV) should face an increased afterload that is due to both the stenotic aortic valve and the peripheral vascular resistance (PVR). Valvulo-arterial impedance (ZV_a ) is a recently introduced parameter, which permits the evaluation of global LV afterload in AS. Aim of this study was to assess the influence of increasing ZV_a on the longitudinal, circumferential, and radial components of LV mechanics.

METHODS

A total of 126 patients (mean age: 80.1±12.0 years, males: 47%) with severe AS (aortic surface <1 cm² or <0.6 cm² /m² ) underwent standard echocardiography to characterize aortic valve gradients, LV function, and ZV_a . 2D speckle tracking echocardiography was used to estimate global longitudinal (GLS), circumferential (GCS), and radial (GRS) LV strain.

RESULTS

The population was divided into four groups according to ZV_a quartiles: Q1 (ZV_a ≤3.43 mm Hg/mL/m² ), Q2 (3.43<ZV_a ≤4.1 mm Hg/mL/m² ), Q3 (4.1<ZV_a ≤5.1 mm Hg/mL/m² ), ad Q4 (ZV_a >5.1 mm Hg/mL/m² ). ZV_a increase from Q1 to Q4 was associated with a progressive reduction in GLS and GCS (ANOVA, both P<.0001). GRS was relatively insensitive to ZV_a increase, a significant reduction of GRS appearing only in Q4 patients with respect to Q1 (29.7±16.4 vs 20.7±13.2%, P=.01).

CONCLUSIONS

Left ventricle myocardial fibers show a different response to afterload increase. Subendocardial fibers function is impaired earlier, whereas mid-wall circumferential fibers remain substantially unaffected, providing interesting insights into the mechanisms of LV dysfunction in AS.

Observed change in peak oxygen consumption after aortic valve replacement and its predictors

Objective

To assess the change in peak oxygen consumption (pVO₂) and determine its outcome predictors after aortic valve replacement (AVR) for aortic stenosis (AS).

Methods

Patients with AS and preserved left ventricular ejection fraction who were referred for single AVR had cardiopulmonary exercise testing prior to and 9 months post-AVR. Predictors of outcome for pVO₂ were determined by multivariate linear and logistic regression analyses. A significant change in pVO₂ was defined as a relative change that was more than twice the coefficient of repeatability by test–retest (>10%).

Results

The pre-AVR characteristics of the 37 study patients included the following: median age (range) 72 (46–83) years, aortic valve area index (AVAI) 0.41 (SD 0.11) cm²/m², mean gradient (MG) 49.1 (SD 15.3) mm Hg and New York Heart Association (NYHA)≥II 27 (73%). Pre-AVR and post-AVR mean pVO₂ was 18.5 and 18.4 mL/kg/m² (87% of the predicted), respectively, but the change from pre-AVR was heterogeneous. The relative change in pVO₂ was positively associated with the preoperative MG (β=0.50, p=0.001) and negatively associated with brain natriuretic peptide > upper level of normal according to age and gender (β=−0.40, p=0.009). A relative increase in pVO₂ exceeding 10% was found in 9 (24%), predicted by lower pre-AVR AVAI (OR 0.18; 95% CI 0.04 to 0.82, p=0.027) and lower peak O₂ pulse (OR 0.94; 95% CI 0.88 to 0.99, p=0.045). Decreases in pVO₂ exceeding 10% were found in 11 (30%) and predicted by lower MG (OR 0.93; 95% CI 0.86 to 0.99, p=0.033).

Conclusions

Change in pVO₂ was heterogeneous. Predictors of favourable and unfavourable outcomes for pVO₂ were identified.

Left ventricular regional function and maximal exercise capacity in aortic stenosis

AIMS

The objective assessment of maximal exercise capacity (MEC) using peak oxygen consumption (VO2) measurement may be helpful in the management of asymptomatic aortic stenosis (AS) patients. However, the relationship between left ventricular (LV) function and MEC has been relatively unexplored. We aimed to identify which echocardiographic parameters of LV systolic function can predict MEC in asymptomatic AS.

METHODS AND RESULTS

Asymptomatic patients with moderate to severe AS (n = 44, aortic valve area <1.5 cm(2), 66 ± 13 years, 75% of men) and preserved LV ejection fraction (LVEF > 50%) were prospectively referred for resting echocardiography and cardiopulmonary exercise test. LV longitudinal strain (LS) of each myocardial segment was measured by speckle tracking echocardiography (STE) from the apical (aLS) 4-, 2-, and 3-chamber views. An average value of the LS of the analysable segments was provided for each myocardial region: basal (bLS), mid (mLS), and aLS. LV circumferential and radial strains were measured from short-axis views. Peak VO2 was 20.1 ± 5.8 mL/kg/min (median 20.7 mL/kg/min; range 7.2-32.3 mL/kg/min). According to the median of peak VO2, patients with reduced MEC were significantly older (P < 0.001) and more frequently females (P = 0.05). There were significant correlations between peak VO2 and age (r = -0.44), LV end-diastolic volume (r = 0.35), LV stroke volume (r = 0.37), indexed stroke volume (r = 0.32), and E/e' ratio (r = -0.37, all P < 0.04). Parameters of AS severity and LVEF did not correlate with peak VO2 (P = NS for all). Among LV deformation parameters, bLS and mLS were significantly associated with peakVO2 (r = 0.43, P = 0.005, and r = 0.32, P = 0.04, respectively). With multivariable analysis, female gender (β = 4.9; P = 0.008) and bLS (β = 0.50; P = 0.03) were the only independent determinants (r(2) = 0.423) of peak VO2.

CONCLUSION

In asymptomatic AS, impaired LV myocardial longitudinal function determines reduced MEC. Basal LS was the only parameter of LV regional function independently associated with MEC.

[Asymptomatic severe aortic stenosis with preserved left ventricular ejection fraction. Evaluation by exercise test: which results and which decision?]

Aortic stenosis is the most common valvular heart disease in Europe and North America and it is a real public health problem. Its prevalence increases with population aging. Symptomatic patients require surgery (class I, level of evidence B). In asymptomatic patients, a stress test with or without imaging is recommended to unmask the false asymptomatic patients and refine risk stratification of occurrence of major events. This support remains difficult and makes the optimal timing for surgery controversial in the absence of prospective data on the determinants of aortic stenosis progression, multicenter studies on risk stratification or randomized studies on patient management. The complexity of care arises from the balance between the spontaneous disease risk (risk of sudden death and irreversible left ventricular dysfunction) and the risk of surgery and prosthetic complications. It is therefore crucial to identify subgroups of patients at risk of pejorative progression in whom prophylactic surgery may be considered. This article focuses on evaluating during exercise asymptomatic patients with severe aortic stenosis and preserved left ventricular ejection fraction. We will explain how to perform the test, determine which echocardiographic measurements should be obtained, focusing on the diagnostic and prognostic value of these measurements and discuss indications for surgery according to new practice guidelines.

Depressed Systemic Arterial Compliance is Associated with the Severity of Heart Failure Symptoms in Moderate-to-Severe Aortic Stenosis: a Cross-Sectional Retrospective Study

BACKGROUND

Patients with aortic stenosis (AS) may develop heart failure even in the absence of severe valve stenosis. Our aim was to assess the contribution of systemic arterial properties and the global left ventricular afterload to graded heart failure symptoms in AS.

METHODS

We retrospectively reviewed medical records of 157 consecutive subjects (mean age, 71±10 years; 79 women and 78 men) hospitalized owing to moderate-to-severe degenerative AS. Exclusion criteria included more than mild aortic insufficiency or disease of another valve, atrial fibrillation, coronary artery disease, severe respiratory disease or anemia. Heart failure symptoms were graded by NYHA class at admission. Systemic arterial compliance (SAC) and valvulo-arterial impedance (Zva) were derived from routine echocardiography and blood pressure.

RESULTS

Sixty-one patients were asymptomatic, 49 presented mild (NYHA II) and 47 moderate-to-severe (NYHA III-IV) heart failure symptoms. Mild symptoms were associated with lower SAC and transvalvular gradients, while more severe exercise intolerance coincided with older age, lower systolic blood pressure, smaller aortic valve area and depressed ejection fraction. By multiple ordinal logistic regression, the severity of heart failure symptoms was related to older age, depressed ejection fraction and lower SAC. Each decrease in SAC by 0.1 ml/m² per mmHg was associated with an increased adjusted odds ratio (OR) of a patient being in one higher category of heart failure symptoms graded as no symptoms, mild exercise intolerance and advanced exercise intolerance (OR: 1.16 [95% CI, 1.01-1.35], P=0.045).

CONCLUSIONS

Depressed SAC may enhance exercise intolerance irrespective of stenosis severity or left ventricular systolic function in moderate-to-severe AS. This finding supports the importance of non-valvular factors for symptomatic status in AS.

Exercise testing in asymptomatic severe aortic stenosis

The management and the clinical decision making in asymptomatic patients with aortic stenosis are challenging. An "aggressive" management, including early aortic valve replacement, is debated in these patients. However, the optimal timing for surgery remains controversial due to the lack of prospective data on the determinants of aortic stenosis progression, multicenter studies on risk stratification, and randomized studies on patient management. Exercise stress testing with or without imaging is strictly contraindicated in symptomatic patients with severe aortic stenosis. Exercise stress test is now recommended by current guidelines in asymptomatic patients and may provide incremental prognostic value. Indeed, the development of symptoms during exercise or an abnormal blood pressure response are associated with poor outcome and should be considered as an indication for surgery, as suggested by the most recently updated European Society of Cardiology 2012 guidelines. Exercise stress echocardiography may also improve the risk stratification and identify asymptomatic patients at higher risk of a cardiac event. When the test is combined with imaging, echocardiography during exercise should be recommended rather than post-exercise echocardiography. During exercise, an increase >18 to 20 mm Hg in mean pressure gradient, absence of improvement in left ventricular ejection fraction (i.e., absence of contractile reserve), and/or a systolic pulmonary arterial pressure >60 mm Hg (i.e., exercise pulmonary hypertension) are suggestive signs of advanced stages of the disease and impaired prognosis. Hence, exercise stress test may identify resting asymptomatic patients who develop exercise abnormalities and in whom surgery is recommended according to current guidelines. Exercise stress echocardiography may further unmask a subset of asymptomatic patients (i.e., without exercise stress test abnormalities) who are at high risk of reduced cardiac event free survival. In these patients, early surgery could be beneficial, whereas regular follow-up seems more appropriate in patients without echocardiographic abnormalities during exercise.

Cardiopulmonary responses to exercise and its utility in patients with aortic stenosis

Utility of cardiopulmonary exercise test is unknown in patients with aortic stenosis. In this retrospective study, we examined the maximal indexes of cardiopulmonary testing at peak exercise in 155 consecutive patients with aortic valve area of ≤ 1.5 cm(2) who were referred for this test. The patients were passively followed up to assess their effect on the primary end point of all-cause mortality. We found that the absolute peak oxygen consumption (VO2) was significantly reduced in these patients, with age and gender-predicted peak VO2 of 80 ± 23%. Peak VO2 was markedly reduced (<80% of predicted) in 54% of patients. During a follow-up of 5 ± 4 years, a total of 41 patients died, and 72 underwent aortic valve replacement. Survival was significantly better in patients with higher absolute peak VO2 (hazard ratio [HR] 0.87, 95% confidence interval [CI] 0.80 to 0.93, p <0.001) and higher oxygen pulse (HR 0.80, 95% CI 0.74 to 0.9, p <0.001). In 83 patients who did not undergo valve replacement, higher peak VO2 and oxygen pulse were associated with better survival (HR 0.83, 95% CI 0.71 to 0.97, p = 0.024 and HR 0.80, 95% CI 0.66 to 0.96, p = 0.02, respectively). In conclusion, the peak VO2 is significantly reduced in patients with aortic stenosis. Higher peak VO2 is independently associated with better survival in these patients irrespective of whether they undergo valve replacement.

Parallel improvement of left ventricular geometry and filling pressure after transcatheter aortic valve implantation in high risk aortic stenosis: comparison with major prosthetic surgery by standard echo Doppler evaluation

Purpose

The effect of Transcatheter Aortic Valve Implantation (TAVI) on left ventricular (LV) geometry and function was compared to traditional aortic replacement (AVR) by major surgery.

Methods

45 patients with aortic stenosis (AS) undergoing TAVI and 33 AVR were assessed by standard echo Doppler the day before and 2 months after the implantation. 2D echocardiograms were performed to measure left ventricular (LV) mass index (LVMi), relative wall thickness (RWT), ejection fraction (EF) and the ratio between transmitral E velocity and early diastolic velocity of mitral annulus (E/e’ ratio). Valvular-arterial impedance (Zva) was also calculated.

Results

At baseline, the 2 groups were comparable for blood pressure, heart rate, body mass index mean transvalvular gradient and aortic valve area. TAVI patients were older (p<0.0001) and had greater LVMi (p<0.005) than AVR group. After 2 months, both the procedures induced a significant reduction of transvalvular gradient and Zva but the decrease of LVMi and RWT was significant greater after TAVI (both p<0.0001). E/e’ ratio and EF were significantly improved after both the procedure but E/e’ reduction was greater after TAVI (p<0.0001). TAVI exhibited greater percent reduction in mean transvalvular gradient (p<0.05), Zva (p<0.02), LVMi (p<0.0001), RWT (p<0.0001) and E/e’ ratio (p<0.0001) than AVR patients. Reduction of E/e’ ratio was positively related with reduction of RWT (r = 0.46, p<0.002) only in TAVI group, even after adjusting for age and percent reduction of Zva (r =0.43, p<0.005).

Conclusions

TAVI induces a greater improvement of estimated LV filling pressure in comparison with major prosthetic surgery, due to more pronounced recovery of LV geometry, independent on age and changes of hemodynamic load.