**EP270: Talking Salt, The Heart, and Antibiotic Prophylaxis**
**Dr. Auric Bishop:** Welcome, my name is Dr. Auric Bishop. I'm a cardiologist, an author, and a keynote speaker. I'm the CEO of the Healthy Heart Network. I'm all about trying to help people live as well as possible for as long as possible. Heart disease is huge in Australia. Every 20 minutes, someone suffers a heart attack. Most of these could probably have been avoided if only we knew what to do. This podcast is all about helping you understand blood pressure, weight, and cholesterol for better health. If you enjoy this podcast, I would be honoured by a five-star review. You can share it with your family and friends. It may well save someone you love.
**Dr. Rick Bishop:** Hi, my name is Dr. Rick Bishop, and today I'd like to talk about salt and the heart. Look, this comes up a lot, and I think many of us think about it as we shake a bit of salt onto our chips at dinner time. So where are we with our understanding about salt and the heart, and what should we be doing? Well, it is important. There's no question that raised salt intake, particularly in some individuals, but broadly across the community, will raise blood pressure. We know that raising blood pressure is one of the most significant drivers of the risk of stroke and heart attack. So salt will impact individuals. There will be individuals who are particularly sensitive, but also broadly across the community, salt intake has an impact on raising blood pressure. It's really important to bear that in mind.
To a large degree, keeping that salt level down is pretty sensible. The Heart Foundation of Australia and the American Heart Foundation recommend the amount of salt taken in per day to be approximately three grams or less, unless you have cardiac failure, in which case they're recommending less than about 1.5 grams per day. What does that mean? A nice and easy rough guide would be that 10 olives in brine is about two grams of salt. So if you enjoy a big handful of olives—maybe two handfuls if you've got small hands—basically, 10 olives that have been preserved in brine is pretty well your two grams for the day, and you've pretty well gone close to your limit for the recommended daily intake of salt.
I'll refer to salt as sodium chloride in this situation because that's really the salt agent that we most commonly use. The reason why I make that specific distinction is because an Australian researcher called Bruce Neal, who is an absolute leader in the field and one of the most recognized medical scientists in the world, has been involved with a study called the Salt Substitute Stroke Study. What he did with his colleagues was look at the introduction of a salt substitute. They used potassium rather than sodium salt, and the outcome was dramatic. They demonstrated significant blood pressure lowering at a community level by simple salt substitution.
Now, I don't have the specifics, but this study really reflected a significant magnitude—a statistically significant magnitude of cardiovascular events as a consequence of lower blood pressure across the world if it was implemented. It was very cost-effective in terms of a salt substitute being much cheaper than looking after heart attacks, strokes, and cardiac failure. So let me invite you to think about salt substitution—potassium-based salts instead of sodium-based salts—to try and lower that intake. For individuals, particularly those who are sensitive to salt intake or have raised blood pressure, lowering salt is worthwhile. Also, across the community, we know it can have a substantial impact. So, salt substitution for the general population—have a think.
The other area where salt is really quite topical is in cardiac failure. This is where the heart may lead, through its failure of normal function, to altered physiological responses that then drive sodium retention and, therefore, water retention. It makes perfect sense that if we reduce sodium intake, we may well reduce some of that sodium retention, some of that fluid retention, and therefore less fluid on board, less strain on the heart, and potentially a better outcome.
Well, there was a large trial that was literally released in the last months called the Sodium HF trial—sodium for sodium chloride, HF for heart failure. This particular study looked at 100 millimoles of sodium per day, or less than 1.5 grams per day, versus usual care for patients with cardiac failure. There was a lot of optimism about this because there was a real sense that altering salt in this situation could well make a difference to readmission rates, particularly hospitalisation and length of hospitalisation. Unfortunately, the Sodium HF trial drew a blank. For this group of patients—individuals with known cardiac failure who probably are already on a number of drugs that will mitigate some of the impact of sodium—there was no clear benefit in putting them on a very restricted reduced sodium diet.
So the recommendation these days is just to keep the sodium down. Don't go silly with it. Three grams per day or less is probably a reasonable objective, and not to get too stringent or focused beyond that. So across the population, for people with blood pressure, limit your salt. It's just not adding a great deal other than flavor to your health. And think long and hard about potentially using salt substitutes. They really work. Bruce Neal, through the Salt Substitute Stroke Study, demonstrated that on a population scale. So give those a thought.
Today, I'd like to talk about antibiotic prophylaxis. What does that mean? From a cardiological perspective, there are times when we want to reduce the risk of bacterial infection seeding through the bloodstream onto the valves of the heart. This gives rise to a condition called endocarditis—"endo" relating to the heart, "itis" meaning infection. One of the forms of that infection within the heart, which is very sinister, is called subacute bacterial endocarditis (SBE). This is a devastating condition, and up to 50% of individuals who have bacterial endocarditis will die.
So it makes a lot of sense to think about who could be at high risk and who should we be giving antibiotics to when there's a risk of bacteria getting into the bloodstream. That's what I'd like to chat a little bit about today because it really is important. It comes up a fair bit just in clinic, and there are plenty of patients who, over the years, have been told that because they have a murmur, they should be getting antibiotics when they get dental work done. Well, that's a little bit old hat these days, so this could act as a really nice up-to-date refresher for where our feelings and thoughts are about using antibiotics to reduce the risk of bacterial endocarditis.
So, no longer do we recommend that anyone who's got a sticky or leaky valve necessarily needs antibiotic prophylaxis in the setting of dental care. So who does need antibiotic prophylaxis? Very simply, anyone who has a prosthetic cardiac valve in place—anyone who's had valve surgery to put a new valve in, whether that's mechanical or whether it's a tissue valve. Also, anyone who's got any repair material within their heart, such as a Dacron patch, these people, without question, should receive antibiotic prophylaxis before the risk of bacteria getting into the bloodstream.
Someone who's had subacute bacterial endocarditis previously should be considered for antibiotic prophylaxis. Patients with congenital heart disease, particularly if there's an unrepaired cyanotic defect—which means there's a connection between the right and left sides of the heart, so they'll be blue—and also people who have had any sort of patch or grafting done. These individuals have, if you like, prosthetic material in their heart, and without question, they should be considered for antibiotic prophylaxis.
The other group in Australia are the individuals often within the Indigenous population but also within the lower socioeconomic group who may have rheumatic heart fever and significant valvular disease. This group of patients should also be considered for antibiotic prophylaxis in the setting of bacteria getting into the bloodstream.
How does bacteria get into the bloodstream and increase the risk of bacterial endocarditis? Probably the most important ways are through the gums and teeth, so dental hygiene ends up being extremely important. Of course, dental procedures can be related to bacteria being introduced into the bloodstream by manipulation where there's bacteria close to the site of an intervention that the dentist is undertaking. There can be shedding of bacteria into the bloodstream.
So we can then think about the risks of this sort of shedding occurring and the risk then associated with the likelihood of that leading to seeding of bacteria on the valve. Dental extraction and significant periodontal work are high-risk interventions and have a very high likelihood of shedding significant amounts of bacteria into the bloodstream. That would require a high-risk antibiotic regime, as would something like tonsillectomy or adenoidectomy. Also, gastrointestinal and genitourinary situations such as lithotripsy may lead to bacteria getting into the bloodstream, and even draining of an abscess can be considered a high-risk procedure.
Lower-risk procedures include things such as a dental oral exam or a local injection that a dentist might undertake. Endotracheal tube or bronchoscopy without any biopsy are considered lower-risk considerations. When it comes to gastro and genitourinary, insertion of an indwelling urinary catheter is considered low risk. Endoscopy, having a look down the gullet, is considered low risk. Transoesophageal echocardiography—which is what a cardiologist might do to look at the valves that could be at risk—is considered low risk as well.
If we are thinking of covering someone who's one of those individuals who should be considered for antibiotic prophylaxis and they're going through a low-risk procedure, a Moxifloxacin, two grams an hour orally beforehand or immediately before IV, is considered an appropriate therapy. For high-risk patients, clindamycin 600 milligrams, one hour orally prior to the procedure or IV at the time of the procedure. If you're in any doubt, if you're not sure about whether an individual who's coming up for a procedure should receive antibiotic prophylaxis or not, please send them to their regular cardiologist or pick up the phone and talk to their regular cardiologist. This is a really important area, and the consequence of having bacterial endocarditis, which may have been prevented, is significant.
Well, I hope you found that little snippet on antibiotic prophylaxis beneficial and helpful. If you have any queries or questions, please feel free to drop me a note. For now, though, I'm going to wish you the very best. Take care and bye for now.
Did you know that coronary artery disease kills one in four people? So most of us are likely to carry some risk or know someone who does. If you're interested in finding out more about how to evaluate that risk, check out www.virtualheartcheck.com.au. It'll give you information about risk and what else can be done to be even more precise.
