Approximately half of hypertensive patients have diastolic dysfunction and diastolic dysfunction is associated with development of congestive heart failure and increased mortality. The Framingham study reported that 51% of patients with HF have a preserved left ventricular (LV) ejection fraction and hypertension is the strongest risk factor for HF with preserved ejection fraction, also termed diastolic heart failure. The rates of death and morbidity in these patients are as high as in patients with HF and a low LV ejection fraction. Hypertensive patients are at increased risk of developing LV hypertrophy and myocardial fibrosis, which cause relaxation abnormality and decreased compliance of LV with a rise in the LV diastolic pressure. Although HF associated with hypertension is a clinically significant problem, few clinical trials have been conducted and there is no proven pharmacological therapy to improve outcomes.

Because the activation of rennin-angiotensin-aldosterone system (RAAS) has been shown to induce LV hypertrophy and myocardial fibrosis, the RAAS may play a central role in the pathogenic process from hypertension to diastolic HF. Inhibitors of RAAS have been considered as a treatment option for these patients, and the angiotensin receptor blockers (ARB) have been of interest because they antagonize the effects of angiotensin II more completely. The largest clinical trial, the Irbesartan in Heart Failure with Preserved Systolic Function (I-PRESERVE), recently reported that treatment with irbesartan did not reduce the risk of death or hospitalization for cardiovascular causes among 4,128 patients who had HF with a preserved LV ejection fraction. The negative result observed in the I-PRESERVE trial may have been the consequence of the following possible factors. First, this trial may have targeted patients in whom the disease process was too advanced for ARBs to be effective. Second, irbesartan may not be an appropriate ARB for a HF trial, because ARBs are not all the same in terms of clinical outcome data in patients with HF. Irbesartan did not have outcome data on reducing HF hospitalization in high-risk hypertensive patients and telmisartan showed no benefits compared to placebo in these patients, although candesartan and valsartan significantly reduced endpoint in placebo-controlled trials. Telmisartan and irbesartan have PPARγ activity and this activity might neutralize the beneficial effects of ARB on HF, because it is well known that PPARγ agonist, rosiglitazone, increases the incidences of HF significantly.

Evaluating the effect of treatments on diastolic dysfunction has been limited by difficulties in non-invasive measure of LV diastolic pressure, but recent advances in echocardiography have made it possible to assess diastolic dysfunction accurately and reproducibly. Thus, additional clinical studies with the other ARBs are needed in hypertensive patients with diastolic dysfunction and assessment of diastolic function by echocardiography will be helpful to determine whether addition of ARB to standard therapy is beneficial to hypertensive patients with diastolic dysfunction. Fimasartan is the first ARB developed in Korea, and was felt to be particularly appropriate for examining the hypothesis that the ARB can improve diastolic dysfunction associated with hypertension, because fimasartan is a potent and well-tolerated ARB. To the best of our knowledge, there has been no randomized trial to demonstrate that an antihypertensive drug improves diastolic function in hypertensive patients with diastolic dysfunction. We hypothesize that fimasartan added to standard therapy will be superior to placebo in improving diastolic dysfunction in mildly symptomatic patients with hypertension and diastolic dysfunction, and try to examine this hypothesis in a double-blind, randomized comparison study using echocardiography.