Background— Obesity and diabetes mellitus are important metabolic risk factors and frequent comorbidities in heart failure with preserved ejection fraction. They contribute to myocardial diastolic dysfunction (DD) through collagen deposition or titin modification. The relative importance for myocardial DD of collagen deposition and titin modification was investigated in obese, diabetic ZSF1 rats after heart failure with preserved ejection fraction development at 20 weeks. Methods and Results— Four groups of rats (Wistar-Kyoto, n=11; lean ZSF1, n=11; obese ZSF1, n=11, and obese ZSF1 with high-fat diet, n=11) were followed up for 20 weeks with repeat metabolic, renal, and echocardiographic evaluations and hemodynamically assessed at euthanization. Myocardial collagen, collagen cross-linking, titin isoforms, and phosphorylation were also determined. Resting tension (F passive )–sarcomere length relations were obtained in small muscle strips before and after KCl–KI treatment, which unanchors titin and allows contributions of titin and extracellular matrix to F passive to be discerned. At 20 weeks, the lean ZSF1 group was hypertensive, whereas both obese ZSF1 groups were hypertensive and diabetic. Only the obese ZSF1 groups had developed heart failure with preserved ejection fraction, which was evident from increased lung weight, preserved left ventricular ejection fraction, and left ventricular DD. The underlying myocardial DD was obvious from high muscle strip stiffness, which was largely (±80%) attributable to titin hypophosphorylation. The latter occurred specifically at the S3991 site of the elastic N2Bus segment and at the S12884 site of the PEVK segment. Conclusions— Obese ZSF1 rats developed heart failure with preserved ejection fraction during a 20-week time span. Titin hypophosphorylation importantly contributed to the underlying myocardial DD.

To test whether remote ischaemic conditioning (RIC) as adjuvant to standard of care (SOC) would prevent progression towards heart failure (HF) after ST-elevation myocardial infarction (STEMI). Single-centre parallel 1:1 randomized trial (computerized block-randomization, concealed allocation) to assess superiority of RIC (3 cycles of intermittent 5 min lower limb ischaemia) over SOC in consecutive STEMI patients (NCT02313961, clinical trials.gov). From 258 patients randomized to RIC or SOC, 9 and 4% were excluded because of unconfirmed diagnosis and previously unrecognized exclusion criteria, respectively. Combined primary outcome of cardiac mortality and hospitalization for HF was reduced in RIC compared with SOC (n = 231 and 217, respectively; HR = 0.35, 95% CI 0.15-0.78) as well as each outcome in isolation. No difference was found in serum troponin I levels between groups. Median and maximum follow-up time were 2.1 and 3.7 years, respectively. In-hospital HF (RR = 0.68, 95% CI 0.47-0.98), need for diuretics (RR = 0.68, 95% CI 0.48-0.97) and inotropes and/or intra-aortic balloon pump (RR = 0.17, 95% CI 0.04-0.76) were decreased in RIC. On planned 12 months follow-up echocardiography (n = 193 and 173 in RIC and SOC, respectively) ejection fraction (EF) recovery was enhanced in patients presenting with impaired left ventricular (LV) function (10% absolute difference in median EF compared with SOC; P < 0.001). In addition to previously reported improved myocardial salvage index and reduced infarct size RIC was shown beneficial in a combined hard clinical endpoint of cardiac mortality and hospitalization for HF. Improved EF recovery was also documented in patients with impaired LV function.

Heart failure with preserved ejection fraction (HFpEF) constitutes a clinical syndrome in which the diagnostic criteria of heart failure are not accompanied by gross disturbances of systolic function, as assessed by ejection fraction. In turn, under most circumstances, diastolic function is impaired. Although it now represents over 50 % of all patients with heart failure, the mechanisms of HFpEF remain understood, precluding effective therapy. Understanding the pathophysiology of HFpEF has been restricted by both limited access to human myocardial biopsies and by the lack of animal models that fully mimic human pathology. Animal models are valuable research tools to clarify subcellular and molecular mechanisms under conditions where the comorbidities and other confounding factors can be precisely controlled. Although most of the heart failure animal models currently available represent heart failure with reduced ejection fraction, several HFpEF animal models have been proposed. However, few of these fulfil all the features present in human disease. In this review we will provide an overview of the currently available models to study HFpEF from rodents to large animals as well as present advantages and disadvantages of these models.

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