AMSTERDAM –
In the NITRATE-CIN Study, non-ST segment elevation myocardial infarction acute coronary syndrome (ACS) patients at risk of renal injury from coronary angiography who received dietary inorganic nitrates had a 70% reduction in CIN compared with those given placebo.
The nitrate group also showed an impressive reduction in periprocedural myocardial infarction (MI) and improved renal function at 3 months, as well as a halving of major adverse cardiovascular events and major adverse kidney events at 1 year.
The trial was presented by Dan Jones, MD, Barts Health NHS Trust, London, at the annual congress of the European Society of Cardiology.
“Currently, aside from intravenous hydration, there is no proven treatment that reduces contrast-induced nephropathy. We feel that dietary inorganic nitrate shows huge promise in this study, and these findings could have important implications in reducing this serious complication of coronary angiography,” Dr. Jones concluded.
He explained that the product used was a formulation of dietary inorganic nitrates given as potassium nitrate capsules, which the study investigators produced specifically for this trial.
At this point, “the only way to get inorganic nitrate is in the diet – specifically by consuming beetroot juice or green leafy vegetables such as spinach and rocket. From a clinician perspective, while these results suggest this is an effective therapy and has great potential, it is not currently possible to prescribe the medication we used in our study, although we are working on producing a commercial product,” he said in an interview.
However, Dr. Jones noted that it is possible to buy beetroot shots, which contain 7 mmol of potassium nitrate in each shot, from health food shops and websites, and two such shots per day for 5 days would give a dose similar to that used in this study, starting the day before angiography.
“While we need a larger multicenter study to confirm these results, studies so far suggest no signal at all that there is any harm in this approach, and there could be a great deal of benefit in taking a couple of beetroot shots prior to and for a few days after an angiogram,” he said.
Dietary nitrates “make sense”
Designated discussant of the NITRATE-CIN trial at the ESC Hotline session, Roxanna Mehran, MD, Icahn School of Medicine at Mount Sinai, New York, said the study was well designed, and the “interesting and plausible” hypothesis to raise nitric oxide levels by dietary nitrates “makes sense.”
On the main findings of a major significant 50% reduction in acute kidney injury, Dr. Mehran said, “It is difficult to imagine such a reduction is possible.”
She pointed out that the large reduction in major adverse cardiac events and major adverse kidney events at 1 year also suggests that there is a sustained benefit in protecting the kidney.
“We’re all going to get on beet juice after this,” she quipped.
Still, Dr. Mehran questioned whether the results were “too good to be true,” adding that a larger trial actually powered for longer term outcome events is needed, as well as a better understanding of whether CIN has a causative role in mortality.
Responding to questions about whether such a large effect could actually be achieved with dietary nitrates, Dr. Jones said he thought there would definitely be some benefits, but maybe not quite as large as those seen in this study.
“From our pilot data we thought nitrate may be effective in preventing CIN,” he said in an interview. “We recruited a higher risk group than we thought, which is why the control event rates were higher than we expected, but the acute kidney injury reduction is roughly what we had estimated, and makes sense biologically.”
Dr. Jones acknowledged that the large reductions in long-term major adverse cardiovascular and kidney events were unexpected.
“The trial was not powered to see reductions in these outcomes, so we need to see if those event reductions can be replicated in larger multicenter trials,” he said. “But this was a double-blind placebo-controlled trial so in this trial the effects are real, and I think the effect size in this trial is too large for there not to be a beneficial effect.
“But I’m not so sure that we would see the same magnitude of effect when we have a larger study with tighter confidence intervals but perhaps a 20%-25% reduction in cardiovascular and kidney may be more realistic, which would still be amazing for such an easy and cost-effective intervention,” Dr. Jones added.
A larger trial is now being planned.
The researchers are also working on the development of a commercial form of dietary inorganic nitrate that would be needed for larger multicenter studies and would then be generally available. “We want this to be a low-cost product that would be available to all,” Dr. Jones said.
He noted that other studies have shown that dietary inorganic nitrates in the form of beetroot juice lower blood pressure; there are suggestions it may also lower cholesterol and prevent stent restenosis, and athletes sometimes take it to increase their aerobic capacity.
“There appears to be many benefits of dietary nitrates, and the one thing we can do at this time is to encourage people to increase their dietary nitrate consumption by eating large quantities of green leafy vegetables and beetroot,” Dr. Jones said.