Citations

Background: Reduced left atrial (LA) compliance (LAC) contributes to pulmonary venous hypertension in heart failure with preserved ejection fraction (HFpEF); however the underlying mechanisms are poorly defined. We hypothesized that microvascular inflammation with rarefaction and impaired nitric oxide (NO) signaling, LA titin hypophosphorylation and fibrosis may each contribute to reduced LAC in HFpEF. Methods: Invasive LA pressure-volume (PV) analyses (open-chest; pericardiotomy; admittance catheter) were performed in 9 aged dogs with experimental hypertension (bilateral renal wrap + DOCA; HFpEF) compared to 13 sham-operated young adult dogs (control). LAC was measured at end-LA reservoir during acute preload reduction (cava occlusion). LA tissue and LA microvascular function were analyzed. Results: Compared to controls, the curvilinear end-LA reservoir PV relationship ( Fig A ) was shifted upward/leftward in HFpEF (LA diastolic stiffness constant 0.08 vs 0.16 mmHg/mL in controls, p=0.005). LA microvascular density (MVD; CD31 stain) tended to be lower in HFpEF than controls (2154±578 vs 2650±523 vessels/mm 2 , p=0.07) and LA MVD negatively correlated with the LA diastolic stiffness constant (r=-0.66, p=0.006). LA microvessels from HFpEF dogs showed impaired endothelium-dependent shear stress-mediated dilation compared to controls, consistent with impaired NO signaling ( Fig B ). Titin isoform expression was similar between groups, but isoform N2B (stiffer) was (p=0.03) and N2BA (compliant) tended to be (p=0.09) hypophosphorylated in HFpEF LA appendage (LAA) tissue. Fibrosis (Picrosirius Red) was similar between groups in the LA free wall and LAA, but increased in areas adjacent to the pulmonary veins in HFpEF (27±12% vs controls 15±8%, p=0.01). Conclusion: In experimental HFpEF, LAC was reduced in association with evidence of LA microvascular rarefaction and impaired NO signaling, titin hypophosphorylation and regional increases in LA fibrosis.

Background— Left atrial (LA) compliance and contractility influence left ventricular stroke volume. We hypothesized that diminished LA compliance and contractile function occur early during the development of heart failure with preserved ejection fraction (HFpEF) and impair overall cardiac performance. Methods and Results— Cardiac magnetic resonance imaging, echocardiography, left ventricular and LA pressure-volume studies, and tissue analyses were performed in a model of early HFpEF (elderly dogs, renal wrap-induced hypertension, exogenous aldosterone; n=9) and young control dogs (sham surgery; n=13). Early HFpEF was associated with LA enlargement, cardiomyocyte hypertrophy, and enhanced LA contractile function (median active emptying fraction 16% [95% confidence interval, 13–24]% versus 12 [10–14]%, P =0.008; end-systolic pressure-volume relationship slope 2.4 [1.9–3.2]mm Hg/mL HFpEF versus 1.5 [1.2–2.2]mm Hg/mL controls, P =0.01). However, atrioventricular coupling was impaired and the curvilinear LA end-reservoir pressure-volume relationship was shifted upward/leftward in HFpEF (LA stiffness constant [β LA ] 0.16 [0.11–0.18]mm Hg/mL versus 0.06 [0.04–0.10]mm Hg/mL controls; P =0.002), indicating reduced LA compliance. Impaired atrioventricular coupling and lower LA compliance correlated with lower left ventricular stroke volume. Total fibrosis and titin isoform composition were similar between groups; however, titin was hyperphosphorylated in HFpEF and correlated with β LA . LA microvascular reactivity was diminished in HFpEF versus controls. LA microvascular density tended to be lower in HFpEF and inversely correlated with β LA . Conclusions— In early-stage hypertensive HFpEF, LA cardiomyocyte hypertrophy, titin hyperphosphorylation, and microvascular dysfunction occur in association with increased systolic and diastolic LA chamber stiffness, impaired atrioventricular coupling, and decreased left ventricular stroke volume. These data indicate that maladaptive LA remodeling occurs early during HFpEF development, supporting a concept of global myocardial remodeling.

Background— Characterization of myocardial structural changes in heart failure with preserved ejection fraction (HFpEF) has been hindered by the limited availability of human cardiac tissue. Cardiac hypertrophy, coronary artery disease (CAD), coronary microvascular rarefaction, and myocardial fibrosis may contribute to HFpEF pathophysiology. Methods and Results— We identified HFpEF patients (n=124) and age-appropriate control subjects (noncardiac death, no heart failure diagnosis; n=104) who underwent autopsy. Heart weight and CAD severity were obtained from the autopsy reports. With the use of whole-field digital microscopy and automated analysis algorithms in full-thickness left ventricular sections, microvascular density (MVD), myocardial fibrosis, and their relationship were quantified. Subjects with HFpEF had heavier hearts (median, 538 g; 169% of age-, sex-, and body size–expected heart weight versus 335 g; 112% in controls), more severe CAD (65% with ≥1 vessel with >50% diameter stenosis in HFpEF versus 13% in controls), more left ventricular fibrosis (median % area fibrosis, 9.6 versus 7.1) and lower MVD (median 961 versus 1316 vessels/mm 2 ) than control ( P <0.0001 for all). Myocardial fibrosis increased with decreasing MVD in controls ( r =–0.28, P =0.004) and HFpEF ( r =–0.26, P =0.004). Adjusting for MVD attenuated the group differences in fibrosis. Heart weight, fibrosis, and MVD were similar in HFpEF patients with CAD versus without CAD. Conclusions— In this study, patients with HFpEF had more cardiac hypertrophy, epicardial CAD, coronary microvascular rarefaction, and myocardial fibrosis than controls. Each of these findings may contribute to the left ventricular diastolic dysfunction and cardiac reserve function impairment characteristic of HFpEF.