Only a few studies have investigated the potential effect of broccoli or its phytochemicals on cardiovascular health. One study conducted by Christiansen and co-workers at Copenhagen University Hospital Daily could not demonstrate a protective effect of the ingestion of 10 g dried broccoli sprouts on endothelial function in humans suffering from essential hypertension . Their study involved 40 hypertensive subjects without diabetes and with normal levels of cholesterol, which were randomized either to ingest 10 g dried broccoli sprouts or to continue their ordinary diet. The broccoli group showed a non-significant improvement of endothelial function measured by flow mediated dilation. There were also no significant in blood pressure.
Akhlaghi and Bandy at the Shiraz University of Medical Sciences investigated the effect of dietary intake of broccoli sprouts by rats on ischemic-reperfused heart  . They found that the intake of broccoli inhibited markers of necrosis and apoptosis, decreased markers of oxidative stress. They also observed that glutathione and activities of the phase 2 enzymes increased. Although the researchers do understand the extact mechanism, they concluded that the obtained results show that a short dietary treatment with broccoli sprouts can strongly protect the heart against oxidative stress and cell death caused by ischemia-reperfusion.
The consumption of broccoli could triggers cardioprotection by generating a survival signal through the activation of several survival proteins and by redox cycling of thioredoxins. That
was the conclusion of researchers at the University of Connecticut School of Medicine after testing the effects of force-feeding to rats with broccoli . Their results showed significant cardioprotection with broccoli as indicated by improved postischemic ventricular function, reduced myocardial infarct size and decreased cardiomyocyte apoptosis.
 Ingestion of broccoli sprouts does not improve endothelial function in humans with hypertension. PLoS One. 2010 Aug 27;5(8):e12461.
 Dietary broccoli sprouts protect against myocardial oxidative damage and cell death during ischemia-reperfusion. Plant Foods Hum Nutr. 2010 Sep;65(3):193-9.
 Broccoli: a unique vegetable that protects mammalian hearts through the redox cycling of the thioredoxin superfamily. J Agric Food Chem. 2008 Jan 23;56(2):609-17. Epub 2007 Dec 29.