Comparison of exercise testing and CMR measured myocardial perfusion reserve for predicting outcome in asymptomatic aortic stenosis: the PRognostic Importance of MIcrovascular Dysfunction in Aortic Stenosis (PRIMID AS) Study

Abstract

MPR was associated with symptom-onset in initially asymptomatic patients with AS, but with moderate accuracy and was not superior to symptom-limited exercise testing. ClinicalTrials.gov (NCT01658345).

Coronary microvascular reserve and outcome in aortic stenosis: Pathophysiological significance vs. clinical relevance

“…In their study, Singh et al have also specifically addressed, for the first time, the question regarding the use of lategadolinium enhancement (the degree of focal fibrosis corresponding to replacement fibrosis) and extracellular volume (diffuse fibrosis corresponding to reactive interstitial fibrosis) measurements, both obtainable in the same examination session as MPR. 11 Although fibrosis is thought to play an important role in the pathophysiology of AS, the current study showed that both measurements were not predictive of the outcome in asymptomatic AS. Only a very small difference in extracellular volume (1%) between those with and without an outcome was observed.…”

“…The higher number of females reaching the primary outcome in the study of Singh et al also highlights the gender specificities regarding the LV remodelling process, smaller cardiac volumes and more concentric LV geometry, different coronary flow reserve with higher resting and hyperaemic myocardial blood flow than men, and distinctive responses to ischaemia and exercise (a more inconclusive test). 4,11,14 In practice, the present data pointed out that no single test enables accurate stratification of asymptomatic patients with severe AS, which calls for multiparametric strategies exploring distinct pathways in the future. However, the use of MPR may still be considered as an alternative to exercise testing, because of several advantages over ETT, including notably a lower rate of inconclusive examinations, and an objective quantification of the microvascular dysfunction as well as LV function and remodelling.…”

“…11 Such an investigation is highly relevant, as the occurrence of typical symptoms during exercise testing is the sole robust class I indication for AVR in AS patients who claimed to be asymptomatic. 2,3 The way in which this observational study has been conducted is exemplary, as this prospective, multicentre investigation has placed special emphases on carefully mitigating some heterogeneity bias (i.e.…”

Stroke volume index in mild-moderate aortic stenosis: more than a barometer of systolic function?

“…However, SVI is dependent on multiple factors, including LV volume, contractility, filling pressures and afterload, and not just valvular obstruction, and therefore will be influenced by other common comorbidities such as coronary artery disease and hypertension. Indeed, SVI was not associated with outcome in our cohort of asymptomatic patients with moderate to severe AS in the recently published PRIMID-AS study 7. Symptom status remains the most important indication for intervention at present, and while low flow may help guide intervention in those with borderline severe AS, its role in those with asymptomatic mild to moderate disease remains questionable in routine clinical practice, especially given the limitations in its measurement on echocardiography.…”

Cardiac magnetic resonance imaging for the assessment of aortic stenosis

“…In the absence of significant epicardial coronary artery disease, a reduction in MPR suggests the presence of microvascular dysfunction,41 which occurs because of the increased metabolic demands of the hypertrophied myocardium, with a relatively reduced capillary density and increased vasodilation at rest to maintain rest perfusion. CMR measured MPR has been shown to be an independent predictor of exercise capacity (peak oxygen consumption) in severe AS,42 as well as a predictor of symptom onset in asymptomatic AS 43. Although qualitative perfusion imaging is widely used in coronary artery disease assessment, its quantification has been limited by complex postprocessing and MBF analysis.…”