Diovan is Novartis's proprietary name for Valsartan, which is an angiotensin II receptor antagonist (more commonly called an "ARB", which stands for Angiotensin Receptor Blocker).
Whether Angiotensin II Receptor Blockers may or may not increase the risk of myocardial infarction [MI] was announced in the BMJ and was more recently debated in the medical journal of the American Heart Association. To date, there is no consensus on whether ARBs have a tendency to increase MI, but there is also no substantive evidence to indicate that ARBs are able to reduce MI.
Of a Diovan combination drug, Wikipedia notes
Diovan HCT contains a combination of Valsartan and hydrochlorothiazide but, unlike Diovan, is only indicated for hypertension, not for CHF or post-MI.