Prevalence of microvascular dysfunction and association with clinical outcomes in heart failure with preserved ejection fraction

Abstract Introduction Heart failure with preserved ejection fraction (HFpEF) accounts for approximately 50% of symptomatic heart failure. A recently proposed paradigm for the pathophysiology of HFpEF postulates a central inflammatory aetiology with coronary microvascular function at its core. However, the pathophysiological and clinical significance of microvascular dysfunction in HFpEF remains uncertain. Purpose Utilising cardiovascular magnetic resonance (CMR), we sought to (1) quantify coronary microvascular function, (2) evaluate the impact of microvascular dysfunction and fibrosis on long-term clinical outcomes and (3) examine the relationship between myocardial perfusion and fibrosis. Methods In a prospective, observational study, 147 subjects (104 HFpEF without a prior history or CMR evidence of coronary artery disease, and 43 asymptomatic controls) underwent multiparametric CMR, comprising left ventricular volumetric assessment, absolute quantitation of myocardial blood flow [MBF] during adenosine stress (140mcg/kg/min) and at rest, and evaluation of diffuse myocardial fibrosis (extracellular volume [ECV]). The primary endpoint was the composite of death or hospitalisation with heart failure. Results 104 HFpEF patients (mean age 73±9 years, mean ejection fraction 56%) and 43 controls (mean age 73±5 years, mean ejection fraction 58%) were studied. There was no significant difference in resting MBF (1.10±0.42ml/min/g in HFpEF subjects vs 1.00±0.38 ml/min/g in controls, p=0.23), though hyperaemic MBF was lower in HFpEF subjects (1.66±0.68 ml/min/g vs 1.97±0.59 ml/min/g, p=0.01). Myocardial perfusion reserve [MPR] was also lower in HFpEF subjects (1.73±0.75 vs 2.22±0.76; p<0.01). Microvascular dysfunction (defined as MPR<2.0) was present in 70% of HFpEF patients (versus 33% of controls, p<0.01). During median follow-up of 3.4 years, there were 46 composite events. MPR was predictive of clinical outcome (one unit increase – hazard ratio [HR] 0.57; 95% CI 0.35–0.92; p=0.02), as was ECV (one standard deviation [SD] increase – HR 1.65; 95% CI 1.14–2.39; p=0.01). However, there was no significant linear correlation between MPR and diffuse fibrosis (r<0.01, p=0.99). Conclusion Microvascular dysfunction is highly prevalent in HFpEF and is associated with adverse clinical outcomes. The lack of correlation between abnormal myocardial perfusion and fibrosis challenges the assertion of a direct causal link between these entities. Funding Acknowledgement Type of funding source: Public Institution(s). Main funding source(s): NIHR, BHF