Exercise Testing in Asymptomatic Aortic Stenosis

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.

Asymptomatic Patients with Severe Aortic Stenosis and the Impact of Intervention

Objectives the exact timing of aortic valve replacement (AVR) in asymptomatic patients with severe aortic stenosis (AS) remains a matter of debate. Therefore, we described the natural history of asymptomatic patients with severe AS, and the effect of AVR on long-term survival. Methods: Asymptomatic patients who were found to have severe AS between June 2006 and May 2009 were included. Severe aortic stenosis was defined as peak aortic jet velocity Vmax ≥ 4.0 m/s or aortic valve area (AVA) ≤ 1 cm². Development of symptoms, the incidence of AVR, and all-cause mortality were assessed. Results: A total of 59 asymptomatic patients with severe AS were followed, with a mean follow-up of 8.9 ± 0.4 years. A total of 51 (86.4%) patients developed AS related symptoms, and subsequently 46 patients underwent AVR. The mean 1-year, 2-year, 5-year, and 10-year overall survival rates were higher in patients receiving AVR compared to those who did not undergo AVR during follow-up (100%, 93.5%, 89.1%, and 69.4%, versus 92.3%, 84.6%, 65.8%, and 28.2%, respectively; p < 0.001). Asymptomatic patients with severe AS receiving AVR during follow-up showed an incremental benefit in survival of up to 31.9 months compared to conservatively managed patients (p = 0.002). Conclusions: The majority of asymptomatic patients turn symptomatic during follow-up. AVR during follow-up is associated with better survival in asymptomatic severe AS patients.

Asymptomatic Severe Aortic Valve Stenosis-When to Intervene: a Review of the Literature, Current Trials, and Guidelines

PURPOSE OF REVIEW

The optimal treatment for asymptomatic patients with severe aortic valve stenosis (AS) is not clearly known. Here, we review the available data on the management of such patients.

RECENT FINDINGS

Half of patients with severe AS are asymptomatic at the time of diagnosis, and are at risk for adverse events, including sudden cardiac death. A significant proportion of these patients develop AS-related symptoms within 1 or 2 years. Clinical and echocardiographic characteristics are predictors of poor outcomes and can guide treatment decisions. Several non-randomized studies and meta-analyses have suggested benefit from early AVR for asymptomatic severe AS, including improved all-cause, cardiovascular, and valve-related mortality. Based on the available information, current guidelines suggest aortic valve replacement in the presence of specific characteristic, including left ventricular dysfunction and very severe AS with significantly elevated gradients. Although the available data suggests early AVR improves the clinical outcomes of these patients, most patients in current practice are managed conservatively. Six randomized trials are ongoing to better elucidate the ideal management of asymptomatic severe AS patients.

Outcomes in Asymptomatic Severe Aortic Stenosis With Preserved Ejection Fraction Undergoing Rest and Treadmill Stress Echocardiography

Background

In asymptomatic patients with severe aortic stenosis and preserved left ventricular ejection fraction, we sought to assess the incremental prognostic value of resting valvuloarterial impedence (Zva) and left ventricular global longitudinal strain (LV‐GLS) to treadmill stress echocardiography.

Methods and Results

We studied 504 such patients (66±12 years, 78% men, 32% with coronary artery disease who underwent treadmill stress echocardiography between 2001 and 2012. Clinical and exercise variables (% of age‐sex predicted metabolic equivalents [%AGP‐METs]) were recorded. Resting Zva ([systolic arterial pressure+mean aortic valve gradient]/[LV‐stroke volume index]) and LV‐GLS (measured offline using Velocity Vector Imaging, Siemens) were obtained from the baseline resting echocardiogram. Death was the primary outcome. There were no major adverse cardiac events during treadmill stress echocardiography. Indexed aortic valve area, Zva, and LV‐GLS were 0.46±0.1 cm²/m², 4.5±0.9 mm Hg/mL per m² and −16±4%, respectively; only 50% achieved >100% AGP‐METs. Sixty‐four percent underwent aortic valve replacement. Death occurred in 164 (33%) patients over 8.9±3.6 years (2 within 30 days of aortic valve replacement). On multivariable Cox survival analysis, higher Society of Thoracic Surgeons score (hazard ratio or HR 1.06), lower % AGP‐METS (HR 1.16), higher Zva (HR 1.25) and lower LV‐GLS (HR 1.12) were associated with higher longer‐term mortality, while aortic valve replacement (HR 0.45) was associated with improved survival (all P<0.01). Sequential addition of ZVa and LV‐GLS to clinical model (Society of Thoracic Surgeons score and %AGP‐METs) increased the c‐statistic from 0.65 to 0.69 and 0.75, respectively, both P<0.001); findings were similar in the subgroup of patients who underwent aortic valve replacement.

Conclusions

In asymptomatic patients with severe aortic stenosis undergoing treadmill stress echocardiography, LV‐GLS and ZVa offer incremental prognostic value.

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.

Prognostic Value of Exercise-Stress Echocardiography in Asymptomatic Patients With Aortic Valve Stenosis

OBJECTIVES

This study sought to evaluate the prognostic value of mean pressure gradient (MPG) increase and peak systolic pulmonary artery pressure (SPAP) measured during exercise stress echocardiography in asymptomatic patients with aortic stenosis (AS).

BACKGROUND

Exercise testing is recommended in asymptomatic AS patients, but the additional value of exercise-stress echocardiography, especially the prognostic value of MPG increase and peak SPAP, is still debated.

METHODS

We enrolled all consecutive patients with pure, isolated, asymptomatic AS and preserved ejection fraction ≥50% and normal SPAP (<50 mm Hg) who underwent symptom-limited exercise echocardiography at our institution. Occurrence of AS-related events (symptoms or congestive heart failure) or occurrence of aortic valve replacement was recorded.

RESULTS

We enrolled 148 patients (66 ± 15 years of age; 74% males; MPG: 47 ± 13 mm Hg; SPAP: 34 ± 6 mm Hg). No complications were observed. Thirty-six patients (24%) had an abnormal exercise test result (occurrence of symptoms, fall in blood pressure, and/or ST-segment depression) and were referred for surgery. Among the 112 patients with a normal exercise test result, 38 patients (34%) had abnormal exercise echocardiography scores (MPG increase >20 mm Hg and/or SPAP at peak exercise >60 mm Hg). These 112 patients were managed conservatively. During a mean follow-up of 14 ± 8 months, an AS-related event occurred in 30 patients, and 25 patients underwent surgery. Neither MPG increase >20 mm Hg nor peak SPAP >60 mm Hg was predictive of occurrence of AS-related events or aortic valve replacement (all p > 0.20). In contrast, baseline AS severity was an important prognostic factor (all p < 0.01).

CONCLUSIONS

In this observational study including 148 patients with asymptomatic AS, we confirmed and extended the importance of exercise testing for unveiling functional limitation. More importantly, neither the increase in MPG nor in SPAP at peak exercise was predictive of outcome. Our results do not support the use of these parameters in risk-stratification and clinical management of asymptomatic AS patients.

Predictors of Long-Term Outcomes in Asymptomatic Patients With Severe Aortic Stenosis and Preserved Left Ventricular Systolic Function Undergoing Exercise Echocardiography

Background—

In asymptomatic patients with severe aortic stenosis and preserved left ventricular ejection fraction, we sought to assess incremental prognostic utility of exercise stress echocardiography.

Methods and Results—

We studied 533 such patients (age, 66±13 years; 78% men; 31% with coronary artery disease) who underwent exercise stress echocardiography between 2001 and 2012. Clinical, echocardiographic, and exercise variables (metabolic equivalents [METs], % of age–sex–predicted METs and heart rate recovery at first minute post exercise) were recorded. The end point was all-cause mortality. The Society of Thoracic Surgeons score, left ventricular ejection fraction, mean resting aortic valve (AV) gradient, indexed AV area, METs, and heart rate recovery were 2.9±3%, 58±4%, 35±11 mm Hg, 0.47±0.1 cm 2 /m 2 , 7.8±3, and 26±12 bpm, respectively. Only 50% achieved >100%, whereas 26% achieved <85% age–sex–predicted METs. There were no major exercise stress echocardiography-related complications. Over 6.9±3 years, 341 (64%) underwent AV replacement (54% isolated), and there were 104 (20%) deaths. On multivariable Cox proportional hazard survival analysis, a higher Society of Thoracic Surgeons score (hazard ratio, 1.21), lower % age–sex–predicted METs (hazard ratio 1.15), and slower heart rate recovery (hazard ratio, 1.22) were associated with higher longer-term mortality, whereas AV replacement (time-dependent covariate, hazard ratio, 0.26) was associated with improved survival. The addition of % age–sex–predicted METs to the Society of Thoracic Surgeons score resulted in significant reclassification of longer-term mortality risk (integrated discrimination index, 0.07 [0.03–0.11; P <0.001).

Conclusions—

In asymptomatic patients with severe aortic stenosis and preserved left ventricular ejection fraction undergoing exercise stress echocardiography, a lower % of age–sex–predicted METs and slower heart rate recovery were associated with longer-term mortality, whereas AV replacement was associated with improved survival.

Natural History, Diagnostic Approaches, and Therapeutic Strategies for Patients With Asymptomatic Severe Aortic Stenosis

Aortic stenosis (AS) is one of the most common valvular diseases encountered in clinical practice. Current guidelines recommend aortic valve replacement (AVR) when the aortic valve is severely stenotic and the patient is symptomatic; however, a substantial proportion of patients with severe AS are asymptomatic at the time of first diagnosis. Although specific morphological valve features, exercise testing, stress imaging, and biomarkers can help to identify patients with asymptomatic severe AS who may benefit from early AVR, the optimal management of these patients remains uncertain and controversial. The current report presents a comprehensive review of the natural history and the diagnostic evaluation of asymptomatic patients with severe AS, and is followed by a meta-analysis from reported studies comparing an early AVR strategy to active surveillance, with an emphasis on the level of evidence substantiating the current guideline recommendations. Finally, perspectives on directions for future investigation are discussed.

Echo Doppler Estimation of Pulmonary Capillary Wedge Pressure in Patients with Severe Aortic Stenosis

BACKGROUND

Transcatheter aortic valve replacement (TAVR) has become a treatment option for patients with severe aortic stenosis (AS) and high surgical risk. Assessment of symptoms in these patients is challenging because of advanced age, comorbidities, and limited physical activity. Noninvasive quantification of pulmonary capillary wedge pressure (PCWP) in candidates for TAVR may be helpful for risk stratification. The objective of the study was to create a model for estimation of PCWP by echo Doppler in patients with severe AS.

METHODS AND RESULTS

Data from 80 patients with severe AS referred for TAVR were used to develop an echo Doppler model for predicting PCWP. Its performance was evaluated in the test cohort of 33 patients who had invasive and noninvasive evaluation. No single echo Doppler parameter estimated PCWP accurately. In the retrospective analysis, the multilinear regression provided an accurate estimate of PCWP (r(2) = 0.74). The model included, in order of importance (all P < 0.05), the ratio of early transmitral velocity (E) to annular velocity (E'), the left ventricular ejection fraction, and the velocity time integral of tricuspid regurgitation signal. In the prospective cohort of patients with severe AS, the model demonstrated good predictive ability of PCWP (r = 0.77, P < 0.01).

CONCLUSION

In patients with severe AS, noninvasive estimation of PCWP is possible by integration of two-dimensional, spectral, and tissue Doppler variables.

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.

Safety of symptom-limited cardiopulmonary exercise testing in patients with aortic stenosis

BACKGROUND

There are no published data on the safety of cardiopulmonary exercise testing in patients with aortic stenosis.

METHODS

In this retrospective descriptive study, we examined 347 consecutive patients with aortic stenosis who underwent cardiopulmonary exercise testing at a tertiary referral center. We recorded major events including death, nonfatal major events (cardiac arrest, symptomatic or sustained ventricular or supraventricular tachycardia, myocardial infarction, and syncope), and minor events such as hypotension, nonsustained supraventricular and ventricular arrhythmias, positive electrocardiographic changes, and angina.

RESULTS

Of 347 patients, 65 (19%) had mild, 145 (42%) had moderate, and 137 (40%) had severe aortic stenosis by echocardiographic criteria. No major events occurred during the tests. Minor events occurred in a total of 97 patients (28%), including 10 patients who developed supraventricular arrhythmias without hypotension; and one who had asymptomatic nonsustained ventricular tachycardia.

CONCLUSION

Symptom-limited cardiopulmonary exercise testing in cardiology-referred patients with aortic stenosis with preserved systolic function appears to be associated with very low risk of major adverse cardiovascular events during testing.

Meta-analysis of prognostic value of stress testing in patients with asymptomatic severe aortic stenosis

The management strategy in asymptomatic patients with severe aortic stenosis (AS) is controversial. Aortic valve replacement has significant morbidity and mortality, while there is a risk for sudden cardiac death with conservative management. There is no consensus on the prognostic value of stress testing to stratify management. A pooled analysis of studies in patients with severe AS was performed to assess the prognostic value of stress testing for adverse events, including angina, dyspnea, acute heart failure, sudden death, and symptoms requiring aortic valve replacement. A search of published research was performed using the terms "stress test" and "asymptomatic aortic stenosis." A random-effects model was used to calculate pooled odds ratios and 95% confidence intervals. Data from 7 studies were included (491 patients with asymptomatic severe AS). None of the patients experienced any complications during or after stress testing. There were no sudden deaths in the patients with normal stress test results after 1 year of follow-up, while 5% with abnormal stress test results had sudden cardiac death. Overall, 52 of 253 patients (21%) with normal stress test results had adverse cardiac events, compared with 156 of 238 (66%) with abnormal stress test results (odds ratio 0.12, 95% confidence interval 0.07 to 0.21, p <0.001). In conclusion, stress testing in asymptomatic patients with severe AS is safe and identifies patients at risk for adverse cardiac events and sudden cardiac death. These data suggest that stress tests can be used for risk stratification and for deciding on the timing of aortic valve replacement in asymptomatic patients with severe AS.