Electrocardiogram: Blog illustrates value of old, but still vital cardiac test

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Photo by Public Domain Pictures

Stephen Smith, MD, an emergency medicine physician at Hennepin County Medical Center in Minnesota, is passionate about using electrocardiograms to save lives. He even writes a popular blog called Dr. Smith’s ECG Blog to train others to more accurately interpret them.

If you’re one of the 735,000 Americans that had a heart attack in the last year, you almost certainly had your heart evaluated with an electrocardiogram, or ECG for short, as soon as you were brought into the emergency room. The heart produces small electrical impulses with each beat, which cause the heart muscle to contract and pump blood throughout your body. The ECG records this electrical activity using electrodes placed on the skin, allowing physicians to detect abnormal heart rhythms and heart muscle damage.

On the surface, an ECG just produces a simple line graph based on technology that was invented over a century ago. So why does it still play such a vital role in the clinic? And how can a physician diagnose a heart condition from a little blip on the line? I recently spoke with Smith, who is also a professor affiliated with the University of Minnesota Twin Cities, about the importance and subtleties of interpreting ECGs.

How do you use ECGs in your medical practice?

“I work full time as an emergency medicine physician and see thousands of patients per year. In the emergency room, the ECG is the first test that we use on everyone with chest pain because it’s the easiest, most non-invasive and cheapest cardiac test. Most of the time when someone is having a big heart attack (myocardial infarction), the ECG will show it. So this is all about patient care. It’s a really amazing diagnostic tool.”

Why did you start your ECG blog?

“Every day I use ECGs to improve the care of my patients, but the purpose of my blog is to help other people do so. I write it for cardiologists, cardiologist fellows, emergency medicine physicians, internal medicine physicians and paramedics — anyone who has to record and interpret ECGs — in order to improve their training and expertise. It’s easy to interpret a completely normal ECG, but many physicians fail to look at all aspects of the ECG together and many abnormalities go unrecognized. Reading ECGs correctly requires a lot of training.

For instance, one of my most popular blog posts presented the case of a 37-year-old woman with chest pain after a stressful interpersonal conflict. She was a non-smoker, with no hyperlipidemia and no family history of coronary artery disease. Her ECG showed an unequivocal, but extremely subtle, sign of a devastating myocardial infarction due to a complete closure of the artery supplying blood oxygen to the front wall of the heart. Her blood testing for a heart attack didn’t detect it, so she was discharged and died at home within 12 hours. It was a terrible outcome, but it demonstrates how training caregivers to recognize these subtle findings on the ECG can mean the difference between life and death.

I get very excited when I see an unusual ECG, and I see several every day. In 2008, I started posting these subtle ECG cases online and, to my surprise, people all over the world became interested in my blog. In July, I had 280,000 visits to my blog and about 90,000 visits to my Facebook page. People from 190 countries are viewing and learning from my posts. And I get messages from all over the world saying how nice it is to have free access to such a high-quality educational tool. I spend about eight hours per week seeking out interesting ECG cases, writing them up and answering questions on my blog, Facebook and Twitter.”

Will ECGs ever be obsolete?

“I don’t think ECGs will ever be outdated, because there is so much information that can be gleaned from them. We’re also improving how to interpret them. The main limitation is having good data on the underlying physiology for each ECG, which can be fed into an artificial intelligence computer algorithm. An AI could learn many patterns that we don’t recognize today.

Right now I’m working with a startup company in France. They’re a bunch of genius programmers who are creating neural network artificial intelligence software. We’re basically training the computer to read ECGs better. We need many, many good data sets to train the AI. I’ve already provided the company with over 100,000 ECGs along with their associated cardiologist or emergency medicine physician interpretations. We’re in the process of testing the AI against experts and against other computer algorithms.

My only role is to help direct the research. I receive no money from the company and have no financial interests. But I do have an interest in making better ECG algorithms for better.”

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.

Stanford Identifies Drug that May Improve Cardiac Stents

Stent in human coronary artery. (Wikimedia, Blausen gallery 2014)
Stent in human coronary artery. (Wikimedia, Blausen gallery 2014)

Researchers from Stanford University School of Medicine believe they’ve found a drug for cardiac stents that can more effectively prevent stent complications.

Over a million people in the U.S. each year undergo angioplasty heart surgery using a drug-coated stent to treat blocked arteries, according to the American Heart Association. A stent is a tiny wire mesh tube that is permanently implanted into the artery at the blockage point, creating a scaffold that props open the artery to reduce the chance of a heart attack. However, placement of bare metal stents can themselves damage the artery lining, causing scar tissue to grow and narrow the artery. Known as in-stent stenosis, this typically occurs 3-6 months after the surgical procedure and can lead to chest pain and even heart attacks.

To help prevent in-stent stenosis, doctors use stents coated with drugs that inhibit tissue regrowth to help prevent the blood vessels from reclosing. Unfortunately, these drugs can also inhibit beneficial regrowth of the vessel’s blood lining (endothelium) that aids the healing process. So patients still need to take blood-thinners for up to a year to reduce the risk of a blood clot developing in the stent and blocking the artery. This need for blood thinners is a serious problem for many people with other health issues; for instance, it means they can’t have surgery while taking the medication.

Stanford researchers have now identified a drug to coat cardiac stents that helps prevent in-stent stenosis without affecting the healing of the blood vessel lining. Their new research is described in a paper published this month in the Journal of Clinical Investigation. Dr. Euan Ashley, associate professor of cardiovascular medicine and genetics at Stanford University Medical Center, led the research team.

The researchers first sought to more fully understand the genetic pathways of coronary artery disease using a “big data” computational biology approach. Using data from previous studies, they analyzed large datasets of coronary artery tissue samples and genome information from patients who had developed in-stent stenosis after undergoing angioplasty and stenting. Based on network analyses, the researchers hypothesized that there is an increased risk of in-stent stenosis due to the interplay of two genes, GPX1 and ROS1.

GPX1 deficiency is known to be independently associated with coronary artery disease in humans. However, ROS1 expression is mostly known for its role in highly malignant cancers, such as lung cancers.

“We didn’t know anything about ROS1,” said Ashley in a press release. “It hadn’t been studied in cardiovascular disease. We knew it was an important gene in cancer. We thought, that’s odd, since the growth caused by stents is almost like a tumor.”

They confirmed their theory by performing an extensive series of laboratory experiments using human tissue samples and genetically engineered knockout mice. Some of these studies involved surgically implanting drug-coated stents in mice with clogged arteries. The researchers inhibited the ROS1 genes by coating these stents with crizotinib – a chemotherapy drug used to treat certain ROS1-positive lung cancers. They found that crizotinib inhibited in-stent stenosis without affecting the lining of the blood vessels.

“The major finding of the study is that artery stent disease acts surprisingly like a tumor in the blood vessel wall,” said Ashley in the press release. “Inhibiting it with nonspecific pharmaceutical agents, as we do now, leads to heart attacks from clots caused by lack of endothelial lining on the stent. Whereas, targeting it with the drug we use here, crizotinib, acts much more specifically and inhibits the disease without affecting the endothelium.”

A tiny mouse-sized stent used by Stanford researchers in their mice studies. (Courtesy of Euan Ashley)
A tiny mouse-sized stent used by Stanford researchers in their mice studies. (Courtesy of Euan Ashley)

Stanford researchers still have a lot more work to do before crizotinib-coated stents will be clinically available. However, this research should translate to the clinic more quickly since crizotinib is already an FDA approved drug.

This is a repost of my KQED Science blog.

New Imaging Method to Detect Heart Attack Risk

Image courtesy of NIH / Wikimedia Commons
Image courtesy of NIH / Wikimedia Commons

785,000 people have an initial heart attack and another 470,000 people have a recurrent heart attack every year in the United States, according to the American Heart Association. This means that an American has a heart attack every 34 seconds and one dies from heart disease every minute. A new imaging technique may help identify who is at high risk.

The primary cause of heart attacks is clogged arteries. Arteries are blood vessels that carry oxygen-rich blood throughout the body. Blood flows easily in healthy arteries with smooth walls. But blood flow is reduced or blocked completely in clogged arteries, when a substance called plaque builds up on the inner walls of the arteries.

Artery-clogging plaque is made up of fat, calcium, cholesterol and other substances found in the blood. Over time, this plaque can harden and rupture. If it breaks apart, a blood clot can form on its surface and completely block the artery, preventing blood from reaching the heart muscle and causing a heart attack. If the blood flow isn’t quickly restored, the portion of the heart fed by the artery begins to die.

Coronary angiography is the “gold standard” way to identify these plaque blockages in the heart, but it’s an invasive surgical procedure. During a coronary angiography, a thin flexible tube called a catheter is put into a blood vessel in your arm, groin or neck and threaded into your coronary arteries. Then a special die is released through the tube, making your coronary arteries visible on X-rays pictures taken as the die flows through them.

New study results, recently published in The Lancet medical journal, show that these high-risk plaque blockages can also be identified using a non-invasive imaging technique. The study was carried out by Dr. Nik Joshi and his research team from the University of Edinburgh, the Royal Infirmary of Edinburgh and the University of Cambridge.

The study involved 40 people who had recently suffered a heart attack and 40 additional people who had stable chest pain (angina). The patients were given a standard coronary angiography and a non-invasive imaging PET-CT scan.

A PET-CT scan measures metabolic activity using positron emission tomography (PET) and anatomical structure using X-ray computed tomography (CT). A trace amount of radioactive drug is injected into the patient’s vein and used to produce 3D images. Joshi and his research team used a radioactive drug called sodium fluoride (NaF).

The study aimed to show how well a PET-CT scan using sodium fluoride detected plaques that had already ruptured or were at high risk of rupturing. The coronary angiography was used as a gold standard to identify the culprit plaque deposits that blocked the arteries.

The researchers measured the sodium fluoride distribution to determine if the artery-clogging plaques took up a significant amount of the drug. In 93% (37/40) of the people who had had a heart attack, significant sodium fluoride uptake was seen in the plaque responsible for the heart attack. The average drug uptake in these culprit plaque deposits was 34% higher than anywhere else in the heart.

In 45% (18/40) of the people with stable chest pain, culprit plaque deposits also took up significant amounts of the sodium fluoride drug. For both sets of patients, the culprit plaque deposits identified by PET-CT imaging were confirmed by histology or intravascular ultrasound to have high-risk characteristics such as calcification and a dead tissue core.

Further research studies with a broad range of patients are now needed before PET-CT sodium fluoride imaging is accepted as a standard clinical technique. These studies are likely to take several years to complete. If they confirm the initial promising results, the technique could then move immediately into clinics since it is already approved and commonly used for other applications.

“If the results are confirmatory then this technique has the potential to fundamentally alter the way we treat coronary artery disease,” concluded the investigators. “It could, for example, permit the identification of the vulnerable patient with single or multiple high-risk or silently ruptured plaques, providing an opportunity to treat and modify their risk to prevent future adverse cardiovascular events.”

This is a repost of my KQED Science blog.

Controversy Over Calcium Tablets

Photograph courtesy of Kham Tran via Wikimedia Commons.
Photograph courtesy of Kham Tran via Wikimedia Commons.

You’ve probably seen the “got milk?” commercials featuring celebrities with milk mustaches, which advertise the nutritional benefit of drinking calcium-rich milk. Your body needs calcium to maintain strong bones and perform other important functions like moving your muscles. If you don’t get enough calcium by eating foods like milk or supplements, then your body pulls calcium from bone.

Your bones are alive. Your body constantly removes old bone and replaces it with new. But as you get older, you often lose bone faster than you can grow it so bones can become weak and break easily. Osteoporosis and low bone mass affect about 52 million people in the United States and result in a fracture every 3 seconds worldwide.

To help prevent Osteoporosis, the use of calcium supplements is common – 43% of U.S. adults and almost 70% of postmenopausal women regularly take calcium supplements. But are these effective and safe? Recent research studies have reported inconsistent results on the benefits and risks of taking calcium supplements.

Calcium supplements commonly cause indigestion and minor constipation, and they infrequently cause kidney stones. Several recent studies suggest that they also increase the risk of heart attacks, but other recent studies disagree.

At the center of the controversy is a 2010 study published in the British Medical Journal. The study analyzed data from 15 randomized, placebo controlled studies of calcium-only supplements. The authors conclude that calcium supplements are associated with a modest increased risk of having a heart attack. Due to the wide use of these supplements, this could affect a large portion of the population. They advise, “A reassessment of the role of calcium supplements in the management of osteoporosis is warranted.”

The authors speculate that taking a calcium supplement causes a dramatic increase in the amount of calcium in your blood, unlike when you gradually get calcium from eating dairy products. This may cause calcifications in your blood vessels and heart, leading to an increased likelihood of having a heart attack. High levels of calcium in the blood may also increase blood clotting and stiffen arteries, both known to cause heart problems.

Although several studies agree with the 2010 British Medical Journal study, they have been criticized by other scientists. The criticisms focus on their patient selection, the number of patients who didn’t take the supplements for the entire study, the methods of statistical analysis, and not monitoring the intake of other dietary nutrients that might alter calcium effects.

In addition, several other research studies recently found no risk of heart problems due to calcium supplement use. For instance, the 2010 Women’s Health Initiative trial analyzed data from over 36,000 women taking calcium and vitamin D supplements and it showed no significant increase in heart problems.

Further research is needed to sort out these inconsistent research findings. But experts seem to agree that it is best to get your recommended daily calcium by eating calcium-rich foods. “A reasonable approach is to preferentially encourage dietary calcium intake and discourage the routine use of calcium supplements,” advises Dr. Douglas Bauer, a professor at the UCSF Medical Center.

How much calcium you need depends on your age. The Institute of Medicine recommends healthy adults to eat foods containing 1000 to 1200 mg of calcium per day. But more calcium isn’t always better. They also recommend avoiding a calcium intake above 2000 to 2500 mg per day to reduce risk of health problems like kidney stones.

In order to meet these recommendations, a useful first step can be to track what you eat during a typical week using a food diary. After calculating how much calcium you usually eat each day, you may need to change your diet to include more calcium-rich foods.

The top calcium-rich foods are yogurt, cheese, milk, sardines, dark leafy greens (collard greens, kale, bok choy, and spinach), fortified cereals, fortified orange juice, and soybeans. For example, you can get the recommended daily 1000 mg of calcium by eating 1 packet of fortified oatmeal (100 mg), 1 cup of 1% milk (305 mg), 8 ounces of nonfat plain yogurt (452 mg) and ½ cup of cooked spinach (146 mg).

“If it is not possible to consume enough calcium from the diet, the use of calcium supplements is most likely safe and not associated with cardiovascular outcomes,” said Dr. Douglas Bauer in a recent press release. But he advises against exceeding the Institute of Medicine guidelines.

This is a repost of my KQED Science blog.