Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Role of Hemodynamic Stress Testing in Mitral Stenosis
Acknowledgments
We thank Kathleen Stergiopoulos, MD, PhD, and Fabio Lima, MPH, for their contributions to the previous edition of this chapter.
Mitral valve (MV) stenosis causes a fixed obstruction in the left ventricular (LV) inflow and decreases the LV preload, thus leading to decreased cardiac output (CO). When severe enough, it can result in elevated pulmonary artery pressures (PAP) and right ventricular (RV) failure. The severity of clinical symptoms directly correlates with the pressure gradient across the MV and left atrial (LA) pressure. Percutaneous mitral balloon commissurotomy or MV surgery is a class I recommendation for patients with severe symptomatic mitral stenosis (MS) (American College of Cardiology [ACC]/American Heart Association [AHA] 2014 and European Society of Cardiology [ESC]/European Association for Cardio-Thoracic Surgery [EACTS] 2017 guidelines). , Echocardiography has a pivotal role in diagnosis and grading of the severity of MS as well as assessment of potential hemodynamic consequences.
Most patients with severe MS present with clinical symptoms of exertional shortness of breath. However, some individuals may complain of nonspecific and equivocal symptoms or may completely be unaware of their symptoms and subjectively feel asymptomatic. This could be because of the insidious rate of progression of MS leading to a sedentary lifestyle from limited functional capacity with no evident symptoms. Echocardiographic assessment of mean mitral gradients and systolic PAP during hemodynamic stress testing can help differentiate this high risk group who would benefit from MV intervention from truly asymptomatic individuals with MS. On the other hand, patients with apparently less severe MS may present with significant exertional symptoms that are not proportional to the severity of MS, as assessed by echocardiography at rest. In this clinical scenario, hemodynamic stress testing is indicated to assess the changes in pulmonary pressures with exercise as a possible cause of the exertional symptoms. In asymptomatic patients with severe MS, the atrioventricular compliance dictates which patients will develop elevated mean mitral gradients and systolic PAP with stress testing.
During the echocardiography examination, the mean mitral gradient can be accurately and reproducibly measured using a continuous-wave (CW) Doppler interrogation across the MV in an apical four-chamber view during supine exercise or immediately post-treadmill exercise. Color Doppler can be used to direct the CW signal to avoid underestimation of the mean gradient. Atrial fibrillation is common in patients with MS, and in these patients, hemodynamic variables should be averaged over 5 to 10 cardiac cycles. Examples of mean pressure gradient across the MV at rest and postexercise are seen in Figs. 93.1 and 93.2 . Similarly, the systolic PAP, estimated based on the tricuspid regurgitation jet velocity at rest and postexercise, are demonstrated in Figs. 93.3 and 93.4 .
Resting mitral valve mean gradient. This 38-year-old woman with no prior medical history originally from South America presented with exertional dyspnea. Baseline transthoracic echocardiography demonstrates a rheumatic mitral valve with mild mitral regurgitation and moderate mitral stenosis, with no other abnormalities. Exercise stress echocardiography is performed. CW, Continuous wave; MV, mitral valve; PG, peak gradient; Vmax, maximal (peak) velocity; Vmean, mean velocity; VTI, velocity time integral.
Postexercise mean transmitral gradient. She exercised for 11 minutes and 10 seconds of a modified Bruce protocol, achieving 7 METs. Peak heart rate was 132 beats/min (77% of predicted), and peak blood pressure during stress was 120/60 mmHg, from a baseline of 92/56 mmHg. The study was terminated secondary to severe dyspnea. No electrocardiographic changes or wall motion abnormalities were noted with stress. The patient remained in sinus rhythm. Her mean forward flow gradient rose to 26 mmHg. CW, Continuous wave; MV, mitral valve; PG, peak gradient; Vmax, maximal (peak) velocity; Vmean, mean velocity; VTI, velocity time integral.
Resting pulmonary artery systolic pressure measurement. CW, Continuous wave; MV, mitral valve; PG, peak gradient; RA, right atrial; RVSP, right ventricular systolic pressure; TR, tricuspid regurgitation; Vmax, maximal (peak) velocity.
Postexercise pulmonary artery systolic pressure measurement. A marked increase in pulmonary artery pressure is noted with exercise. CW, Continuous wave; PG, peak gradient; RVSP, right ventricular systolic pressure; TR, tricuspid regurgitation; Vmax, maximal (peak) velocity.
Indications for hemodynamic stress testing in mitral stenosis according to the most recent guidelines:
The 2014 AHA/ACC Guideline for the Management of Patients with Valvular Heart Disease, recommends exercise stress echocardiography (ESE) with Doppler or invasive hemodynamic assessment to evaluate the response of the mean mitral gradient and systolic PAP in patients with MS when there is a discrepancy between resting Doppler echocardiographic findings and clinical symptoms or signs (class I; level of evidence: C).
This is supported by the American College of Cardiology Appropriate Use Criteria Task Force/American Association for Thoracic Surgery/American Heart Association/American Society of Echocardiography/European Association for Cardio-Thoracic Surgery/Heart Valve Society/Society of Cardiovascular Anesthesiologists/Society for Cardiovascular Angiography and Interventions/Society of Cardiovascular Computed Tomography/Society for Cardiovascular Magnetic Resonance/Society of Thoracic Surgeons (ACC/AATS/AHA/ASE/EACTS/HVS/SCA /SCAI/SCCT/SCMR/STS) 2017 Appropriate Use Criteria for Multimodality Imaging in Valvular Heart Disease. According to this document, ESE is deemed appropriate to “evaluate mean mitral gradient and PAP, in case of discrepancy between resting Doppler echocardiographic findings and clinical symptoms or signs.”
According to 2017 ESC/EACTS guidelines for the management of valvular heart disease, asymptomatic patients with significant MV stenosis, defined as mitral valve area (MVA)1.5 cm 2 or less who are not identified as high risk for embolism or hemodynamic decompensation, should undergo stress testing for further risk stratification. MV intervention, including surgical valve replacement or percutaneous mitral balloon commissurotomy, is indicated when the stress test is positive with symptoms. High-risk features for thromboembolism risk include a history of systemic embolism, dense spontaneous echo contrast in the left atrium, or new-onset atrial fibrillation. High-risk characteristics for hemodynamic compromise includes those with systolic PAP greater than 50 mmHg, need for major noncardiac surgery or patients desire for pregnancy. All asymptomatic patients with these high-risk features should directly undergo evaluation for MV intervention without the need for stress testing.
You're Reading a Preview
Become a Clinical Tree membership for Full access and enjoy Unlimited articles
If you are a member. Log in here