Characterization of a novel ovine model of hypertensive heart failure with preserved ejection fraction.

The lack of animal models which accurately represent heart failure with preserved ejection fraction (HFpEF) has been a major barrier to the mechanistic understanding and development of effective therapies for this prevalent and debilitating syndrome characterized by multisystem impairments. Herein, we describe the development and characterization of a novel large animal model of HFpEF in older, female sheep with chronic 2-kidney, 1-clip hypertension. At six weeks post-unilateral renal artery clipping, hypertensive HFpEF sheep had higher mean arterial pressure compared to similarly aged ewes without unilateral renal artery clipping (mean arterial pressure = 112.7±15.9 vs 76.0±10.1 mmHg, P < 0.0001). The hypertensive HFpEF sheep were characterized by (i) echocardiographic evidence of diastolic dysfunction (lateral e' = 0.11±0.02 vs 0.14±0.04 m/s, P = 0.011; lateral E/e' = 4.25±0.77 vs 3.63±0.54, P = 0.028) and concentric left ventricular hypertrophy without overt systolic impairment, (ii) elevated directly measured left ventricular end-diastolic pressure (13±5 vs 0.5±1 mmHg, P = 2.1x10^-6), and (iii) normal directly measured cardiac output. Crucially, these hypertensive HFpEF sheep had impaired exercise capacity as demonstrated by their (i) attenuated cardiac output (P = 0.001), (ii) augmented pulmonary capillary wedge pressure (P = 0.026), and (iii) attenuated hindlimb blood flow (P = 3.4x10^-4) responses, during graded treadmill exercise testing. In addition, exercise renal blood flow responses were also altered. Collectively, our data indicates that this novel ovine model of HFpEF may be a useful translational research tool since it exhibits similar and clinically relevant impairments as that of HFpEF patients.