A Feline HFpEF Model with Pulmonary Hypertension and Compromised Pulmonary Function

Figures

• 

  Figure 1. Echocardiographic Phenotyping. Banded cats showed left ventricular hypertrophy (a), preserved global systolic function (b), LA enlargement (c) and dysfunction (d), and impaired diastolic function (i–k). Representative short (e–f) and long (g–h) axis b-mode images at 4-months post-banding/sham procedure. E/A ratio (l–n) and corresponding tissue Doppler-derived peak velocities (l′–n′). *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 between sham and banded animals. †p < 0.05, †††p < 0.001, ††††p < 0.0001 vs BL. Ao = aorta, BL = baseline, E and A = peak early- and late diastolic transmitral velocities, e′ and a′ = spectral tissue Doppler-derived peak early- and late diastolic velocities, FS = fractional shortening, IQR = interquartile range, LA = left atrium, LA EF = left atrial ejection fraction, LAVES = left atrial end-systolic volume, LV = left ventricle.

• 

  Figure 2. Hemodynamics before and after dobutamine stress testing. ( a) LVPmax was higher in banded cats. (b) CO was similar between groups. (c) Dp/dtmax was attenuated in banded animals after dobutamine. Banded animals showed elevated LVEDP (d) and mPAP (e). τ was prolonged (f), t-dia/ τ (g) and dP/dtmin (h) were reduced after aortic banding, indicative of impaired relaxation. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 between groups. †p < 0.05, ††p < 0.01, †††p < 0.001, ††††p < 0.0001 vs BL. BL = baseline, CO = cardiac output, dP/dtmax = maximum rate of pressure rise, dP/dtmin = maximum rate of pressure decay, LVEDP = left ventricular end-diastolic pressure, LVPmax = maximum left ventricular pressure, mPAP = mean arterial pulmonary pressure, τ = isovolumic relaxation constant, t-dia = diastolic time interval.

• 

  Figure 3. LV hypertrophy. HW/BW ratio (a), CM cross-sectional area (b), and ACTA1 expression levels measured by Real-Time PCR (c), were increased in banded vs sham cats. Confocal micrographs of LV tissue section stained for WGA (green) and DAPI (blue) show increased CM size and extracellular matrix deposition in banded cats (e–f) compared to sham (d). Scale bars = 50 µm. *p < 0.05, ***p < 0.001 between groups. ACTA1 = skeletal muscle actin, BW = body weight, CM = cardiomyocyte, HW = heart weight.

• 

  Figure 4. LV fibrosis and NT-proBNP. (a,b) Bright-field micrographs of LV tissue section stained with Masson’s trichrome indicating an increase in blue-stained fibrotic area in banded (b) vs sham (a) cats. Scale bars from left to right: 5 mm, 250 µm, and 50 µm. (c) Quantification of fibrotic area in septal wall and lateral wall revealed an increase in banded vs sham cats. (d) LV fibrosis was more pronounced in subendocardial layers and decreased moving outwards to the subepicardial layers in banded cats. ( e ) Banded cats had elevated NT-proBNP plasma levels at 4-months post-banding compared to sham cats. (f) Correlation between LAVES and NT-proBNP. *p < 0.05, **p < 0.01 between groups. ††p < 0.01 vs BL. #p < 0.05 vs subendocardial. BL = baseline, LAVES = left atrial end-systolic volume, NT-proBNP = N-terminal pro-brain natriuretic peptide.

• 

  Figure 5. Lung mechanics and gas exchange. (a) Respiratory compliance was decreased in banded vs sham cats. (b–d) Impaired oxygenation in banded vs sham cats was reflected by decreased PaO2/FIO2 ratio, increased A-aDO2 and increased intrapulmonary shunt. FIO2 = 1. *p < 0.05, **p < 0.01 between groups. A-aDO2 = alveolar-arterial oxygen difference, PaO2 = partial pressure of oxygen in arterial blood.

• 

  Figure 6. Morphological lung changes. ( a,b) Increased wet/dry lung weight ratio and protein content in banded vs sham cats is suggestive of endothelial leaking. (c) Alveolar-capillary wall thickness was increased in banded vs sham cats. Alveolar area (d) and expansion index (e), the ratio of volume of gas exchange to parenchymal space, were decreased in banded vs sham cats. (f) Ratio of cuff/vessel area of extra-alveolar vessels was increased in banded vs sham cats. (g,h) Bright-field micrographs of H&E-stained lung sections. * = bronchioles, † = extra-alveolar vessel, arrow = fluid cuff around extra-alveolar vessels. Scale bars = 250 µm. *p < 0.05, **p < 0.01, ***p < 0.001 between groups.

• 

  Figure 7. Concept of pathobiological and functional abnormalities due to elevated left-sided filling pressures. Slow-progressive pressure overload induces LV hypertrophy and interstitial fibrosis which subsequently causes impaired relaxation (prolongation of τ, decreased dP/dtmin) and impairment in systolic reserve function. LV remodeling and dysfunction results in elevated LV filling pressures (LVEDP), LA enlargement and LA dysfunction. Passive backward transmission of elevated pressures causes an increase in hydrostatic venous pressure and leads to pulmonary arterial hypertension, which promotes endothelial disruption with protein and fluid loss into the interstitium and alveoli (alveolar-capillary stress failure). Interestingly, not only capillaries are affected, but extra-alveolar vessels also show distinct perivascular fluid cuff formation. These cardiopulmonary abnormalities result in decreased respiratory compliance and impaired oxygenation. A-aDO2 = alveolar-arterial oxygen difference, Ao banding = aortic banding, LA = left atrium, LVH = left ventricular hypertrophy, mPAP = mean pulmonary arterial pressure, PaO2 = partial pressure of oxygen in arterial blood. Red boxes = structural…