Sunday, March 3, 2019

A Spoonful of Medicine Helps the Sugar Go Down


Diabetes mellitus is one of the most common chronic conditions in the world and a significant risk factor for heart disease.  It is a major contributor to global morbidity and mortality. What is diabetes and how can it be controlled to reduce the burden of heart disease and cardiac death? Diabetes is a disease characterized by high blood sugar.  Type I diabetes starts at an early age and occurs because the body does not produce enough insulin (insulin is a hormone secreted by the pancreas and is responsible for regulating the sugar in the body). Type II diabetes occurs in adults, accounts for 90% of the cases of diabetes, and is the result of the body resisting the effects of insulin.  The prevalence of Type II diabetes keeps rising, paralleling the obesity epidemic. It has been estimated that 13% of all U.S. adults have diabetes.  Diabetes is diagnosed by a single blood draw, looking at two tests, glucose (blood sugar) and hemoglobin A1C (a three-month average of the blood sugar). Diabetes is present if hemoglobin A1C is greater than 6.5% or the fasting blood sugar is greater than 126 mg/dl or the nonfasting blood sugar is greater than 200 mg/dl.

Heart disease is the main cause of death among patients with diabetes. Diabetics have a twofold to fourfold increased risk for blockage in the heart arteries, a heart attack or cardiac death and a twofold to fivefold increased risk for congestive heart failure (fluid in the lungs). In addition, diabetic patients are at increased risk for stroke and blockage in the leg arteries.   Therefore the treatment goals for the diabetic patient include lowering the blood sugar, reducing the risk for complications of diabetes (for example kidney disease and blindness) and especially reducing the risk for heart disease.

Cardiovascular risk factor management in Type II diabetes starts with diet.  Patients are often referred to specialized dieticians to help with monitoring caloric intake and carbohydrate consumption. A Mediterranean-style diet can greatly reduce blood sugar.  The goal is to lower the hemoglobin A1C to < 7%. Overweight and obese patients are counseled about weight loss; even a modest reduction in weight of 3-5% can make a big difference.  For severely obese patients, weight loss surgery (for example, gastric sleeve) is often recommended. With significant weight loss, diabetic medications can be weaned down and in many cases stopped.  Diabetic patients with elevated blood pressure should be placed on medication, with a blood pressure goal between 120 and 140.  Diabetics whose LDL cholesterol is high should be prescribed a statin, with an LDL goal < 70 mg/dl. Achieving these aims is not easy.  In a large recent study of 73,000 diabetic patients, 73% met the hemoglobin A1C target, 69% met the blood pressure goal and 48% hit the LDL number. Unfortunately, however, only 21% met all three goals.

Recently, the medical management of the patient with Type II diabetes underwent a revolution.  There are twelve classes of medications (including insulin) and at least 36 individual drugs approved for the treatment of diabetes.  Picking the right drug or the right combination of drugs can be difficult. It is generally agreed that treatment start with metformin, which has been shown to lower hemoglobin A1C and reduce cardiac events.  Picking the right target for treatment is just as difficult. For the past 20 years, the medical therapy of diabetes focused on intensive control of blood sugar. However, this approach did not reduce cardiovascular events and may have increased them.  Then in 2008 the Food and Drug Administration mandated that any new diabetes drug must prove its cardiovascular safety before being approved for use.  This resulted in the discovery of new drugs which did just that; they were shown to lower the risk for major heart events and reduce cardiac deaths. This has led to a fundamental shift in diabetes management, away from lowering blood sugar and toward reducing cardiac risk.  In fact, for the first time ever, the American Diabetes Association and the American College of Cardiology have aligned their medication recommendations for treating Type II diabetes.  

The new agents fall into two classes of diabetes medications: sodium-glucose cotransporter-2 (SGLT2) inhibitors and glucagon-like peptide-1 receptor (GLP-1) agonists.  Both classes of agents substantially reduce the risk for heart attack, stroke and cardiac death. Both reduce blood pressure and promote weight loss. The best-studied SGLT2 inhibitor is empagliflozin (Jardiance), a once a day oral medication. The classic GLP-1 agonist is liraglutide (Victoza), a once weekly injection. It is felt that SGLT2 inhibitors are better for CHF patients while the GLP-1 agonists are better at reducing heart attack and stroke. 

The bottom line, according to both diabetes doctors and cardiologists, is that patients with Type II diabetes and established heart disease start treatment with lifestyle management (especially diet and weight loss).  If medication is needed, then metformin is the first line agent.  If a second line agent is necessary, then either an SGLT2 inhibitor or a GLP-1 agonist should be used, depending on patient characteristics.

Sunday, February 10, 2019

Sleeping Tips to Avoid A Wake



We all could use a good night’s sleep. Sleep is an important part of the day but approximately one third of Americans do not get adequate sleep. Not getting a good night’s sleep is a health hazard and can lead to hypertension (high blood pressure), heart artery disease, atrial fibrillation (an irregular heart rhythm) and early death. What can be done to get a good night’s sleep?

First, we should understand a little about the physiology of sleep. The normal sleep cycle consists of four stages. There are three stages of non-REM (rapid eye movement) sleep, each lasting about five to fifteen minutes. Stage 3 of non-REM is the deep sleep stage where the body repairs itself. During this stage, the muscles, the tissues of the body and the brain are refreshed from the stresses of the day. In addition, bone and muscle are built and the immune system is strengthened. During the REM stage, the eyes move rapidly from side to side, the muscles are often paralyzed and the brain is more active than in stage 3. Dreaming occurs during REM sleep and a person can dream 4 to 6 times per night. 

There are a variety of sleep disorders; the most common are insomnia and sleep apnea. Insomnia is difficulty falling asleep and staying asleep. It may be due to psychological stress, excessive mental activity at bedtime, inconsistent bedtimes or caffeine or heavy alcohol intake in the evening. It may be treated through behavioral modifications (for example keeping a regular bedtime), exercise (at any time of the day), and avoiding stimulants in the evening.  Medications can be helpful, including sleeping pills and melatonin. Melatonin is a hormone produced by the pineal gland in the brain and it helps regulate the sleep-wake cycle.  It is also available as an over the counter medication used to shorten the time to sleep.  Nowadays, one of the biggest causes of insomnia is the use of light emitting electronic devices (laptop computers, tablets, cell phones and televisions) near bedtime.  It has been found that the light exposure from these devices affects the normal sleep cycle.  The light emitted suppresses the secretion of melatonin. This causes a later sleep time, increased alertness at bedtime, reduced REM sleep, and increased morning sleepiness.  This effect is especially pronounced in children and adolescents. For a better night of sleep try to avoid using these devices for at least one hour prior to bedtime. 

Sleep apnea is a condition characterized by periods of decreased breathing while sleeping (apnea means absence of breathing). Obstructive sleep apnea occurs when the upper airway collapses, air movement into the lungs ceases causing the oxygen level in the body to fall. This prompts the person to wake up and take deep breaths.  These periods of apnea disrupt the sleep cycle and prevent the person from getting enough time in the deep sleep, restorative stages of sleep.  Because the body does not get enough rest, the person feels “revved up” all the time.  Sleep apnea is often seen in obese patients and is quite common occurring in 34% of men and 17% of women.  It is associated with loud snoring, excessive daytime sleepiness, morning headaches and irritability.  Sleep apnea is also associated with significant heart problems including hypertension (especially hypertension that is difficult to treat), stroke, heart failure, blockage in the heart arteries and atrial fibrillation. It is diagnosed by a sleep study, which counts and measures the periods of apnea and low oxygen. Treatment of sleep apnea primarily involves weight loss and CPAP (continuous positive airway pressure- a mask that keeps the airway open).  Treatment with CPAP is especially useful in lowering blood pressure and preventing recurrent episodes of atrial fibrillation and congestive heart failure.  

Just as important as sleep is the process of waking up. Being jolted from a deep sleep by an alarm clock is as bad as not getting enough sleep. When one is woken suddenly and too early, there is a prolonged period between the eyes opening and being fully awake. This phenomenon is called sleep inertia, a groggy sensation somewhat like jet lag.  We feel this because we are awake, but our bodies want to keep sleeping. This is because the brain’s arousal system is activated almost immediately but the higher centers of the brain take longer to awaken. If woken abruptly, as with an alarm clock, the sleep inertia is more severe.  Sleep inertia can take anywhere from two to four hours to resolve.  Waking up naturally, by our own internal clock, is much better for us. The mismatch between our biologically optimal wake up time and the alarm clock time takes a toll on our system, leading to obesity, diabetes and heart disease.  On the other hand, in cultures known for their longevity, there are a higher percentage of people who wake naturally. 

This leads to the question, how much sleep is enough sleep? What is the optimal amount of sleep needed for a long and healthy life?  In one study examining patients between 40 and 54 years old and who were free of heart disease, those sleeping less than 6 hours or more than 8 hours per night had higher risk of plaque in the heart arteries than those sleeping 7 to 8 hours. In another study of patients over 60 years old, those who slept less than 6 hours had a 12% increased risk for death and those who slept more than 9 hours had a 30% increased risk of death.  In this population as well, 7 to 8 hours was the optimal amount of sleep time. However, very different results could be found if younger populations are studied.

So start altering those bad nighttime habits and start getting a good night’s sleep.


Sunday, January 13, 2019

The Key to The Heart: Be Nice to Your Spouse


What are the best ways to avoid heart disease and live a long, healthy life?  The answer starts with the four basic characteristics of a healthy lifestyle: get adequate exercise, maintain a healthy weight, avoid smoking and eat a prudent diet.  Essentially following these four pillars is an individual choice: whether to exercise and how much to exercise, whether to avoid smoking and keep the pounds off and what one eats is largely up to each individual. What can be done beyond the individual? Does marital status affect the heart? Does belonging to a larger community and socializing help prevent heart disease?

It turns out that being married is good for the heart. In patients who have heart disease, being married was better than not being married.  In studies it was found that unmarried participants (including divorced, separated, widowed and never-married) had a 52% higher rate of heart attack and death compared to married participants.  Married patients who had open-heart surgery or stent placement were much more likely to be alive and free from heart events than unmarried patients.  Divorce has the highest rates of heart events and cardiac death, presumably due to the stress it invokes. Fortunately, remarriage decreases some of that risk.  The risk for unmarried patients is the same for both men and women but younger patients (aged < 65 years old) had a higher risk than older patients.  Does the same relationship hold true in the general population (in people who don’t already have heart disease)? In this population as well, unmarried participants had higher rates of heart disease, stroke and death. Why is being married so protective? There are many potential reasons. Having a spouse may mean that warning symptoms are detected and acted upon sooner. Unmarried patients typically had longer delays in seeking treatment. Spouses can encourage sticking to a healthy lifestyle including eating better, having someone to walk or exercise with and providing support when quitting smoking. In addition, spouses can encourage adherence to treatment including taking medications as prescribed. Lastly, the loss of a spouse (either due to death or divorce) has detrimental physical and emotional consequences.  Stress can worsen blood pressure, raise cholesterol, worsen diabetes and accelerate the progression of blockage in the heart arteries.  Stress affects emotional well being resulting in a decreased ability to prevent, detect or treat illness.

The research noted above looked at married versus unmarried people, but it can be generalized to living with someone versus living alone. Can this be broadened further to mean that social isolation is bad for the heart? Is it better to be part of a larger community?  Studies have shown that those with few social contacts (or who are socially isolated) have about 30% higher risk for heart disease and stroke.  In addition, those with poor social connections had a 50% higher risk for death than those with better social integration. This makes the effect of social isolation as detrimental as a sedentary lifestyle or being obese.  Depth and quality of the social connections matter as well.  Having one friend beats being alone, but having a larger network is better and having true friends (as opposed to acquaintances) who can provide emotional support is better still.  Social networks can help when someone is ill, for example by helping to prepare meals or drive to a doctor’s appointment. A connected, supportive network is an antidote to the stress of daily life by providing emotional support and lowering the release of stress hormones. People who are socially isolated tend to engage in negative health behaviors such as smoking, drinking excess alcohol and not exercising or eating correctly. Social isolation also can affect the body by increasing inflammation, decreasing immune function and increasing blood pressure. Lastly, there is no down side to developing a strong social network.  

As the New Year dawns and resolutions are made to follow a healthy lifestyle, don’t forget to include a promise to be part of a healthy community as well. This can be done by joining a walking group, being part of a religious organization or playing on a sports team.  For heart patients, the individual and the community are nicely tied together in the Ornish Lifestyle Medicine Program, which has been shown to reverse the progression of heart disease. The program entails a cohort of ten people who exercise together, eat a heart healthy diet together, and learn how to reduce stress. These patients have similar heart problems so there is a strong component of socialization and social support in the group. Similarly, in cultures known for their longevity, food, exercise and socializing are tied together.  Entire towns are out walking before or after the evening meal. Both the walking and the meal are shared with others in the community. So, grab your spouse or a friend, go for a walk, meet others for dinner, catch a show or a movie and have a wonderful date night. 

Sunday, December 9, 2018

How the Cardiologist Stole Holiday Treats


The holidays bring visions of sugar plum fairies dancing and tables filled with fruitcake, sugar cookies, gingerbread, red velvet cake, macaroons and chocolate yule log. These delectable holiday treats are as much a staple of the holidays as family gatherings and celebrations. Unfortunately, these sugary delights are not quite part of a heart healthy diet and can wreak havoc with cholesterol levels.  As we head into the peak holiday and treat-eating season, it’s a good time to review what is new in cholesterol management.

Who should be treated with a statin for high cholesterol in 2019? In 2013, the American Heart Association and the American College of Cardiology published a guideline to address this topic.  This guideline was just updated in November 2018, adding more nuance to the original. The guideline focuses primarily on LDL cholesterol (low density lipoprotein, “the bad cholesterol”). In general, there are four categories of patients for whom a statin should be prescribed: 
1) secondary prevention (trying to prevent a second event in patients who have already had a heart attack or stroke), 
2) diabetic patients (a high risk group) whose LDL is greater than 70 mg/dl, 
3) patients with an LDL greater than 190 mg/dl (severe familial high cholesterol).  For these three groups, especially secondary prevention, the medical literature is quite consistent in showing the benefit of statin therapy. The data for statins is less robust in the fourth group, primary prevention (trying to prevent a heart attack or stroke in a patient who has not had an event).  The 2013 guideline used a risk calculator (which can be found at: cvriskcalculator.com) to identify high-risk patients for primary prevention.  This was a controversial issue at the time and many cardiologists felt that the calculator overestimated the risk, thus exposing more people to statin therapy.  The updated guideline attempts to clarify who should be on a statin by adding risk enhancers and using coronary calcium score. If the calculator places the patient at high risk for a cardiac event over the next ten years with a score of 20% or greater, then a statin should be given.  If the patient is at low risk (a score of 5% or less), then no statin is necessary.  If the patient is at intermediate risk (a score between 5% and 20%), then risk enhancers are used.  These risk enhancers are: 
LDL > 160 mg/dl,
high-sensitivity C reactive protein level (a measure of inflammation) > 2.0 mg/L, 
triglycerides > 175 mg/dl, 
apoliprotein B level > 130 mg/dl, 
lipoprotein (a) level > 50 mg/dl, 
peripheral arterial disease, 
chronic kidney disease, 
chronic inflammatory disease (rheumatoid arthritis, psoriasis, or lupus), 
metabolic syndrome (hypertension, diabetes, high triglycerides, obesity- especially a large waist circumference), 
family history of premature heart disease, or 
premature menopause. 
With an intermediate risk score and the presence of one or more risk enhancers, a statin should be prescribed. If the patient and the doctor still are uncertain about starting a statin, then a coronary calcium score can be used. A CT scan of the heart measures the calcium score. Calcium is found in plaque in the heart arteries. The higher the amount of calcium, the more plaque is present in the heart arteries. A coronary calcium score of zero means there is no plaque and a statin can be withheld.  However, if the calcium score is 100 or more, then a statin is indicated. 

What about the other test on the standard lipid panel, triglycerides?  It is well known that patients who have heart disease and good LDL levels on statin but have elevated triglycerides are still at risk for cardiac events. It is thought that reducing triglycerides can provide an additional benefit beyond lowering the LDL. Unfortunately, this hypothesis has never been proven, until recently.  Medications that reduce triglycerides such as niacin or fenofibrate, taken with a statin, did not show a reduction in cardiac events. Omega-3 fatty acids (fish oil) are present in fatty fish and in populations with high fish intake, there is a lower risk for heart disease.  Formulations of omega-3 fatty acids contain either eicosapentaenoic aicd (EPA) alone or a combination of EPA with docosahexaenoic acid (DHA). These medications are prescribed to treat elevated triglycerides but neither the combination nor low dose EPA have been shown to reduce the risk for heart disease. More recently, a high dose, pure form of EPA was tested in patients with heart disease, statin controlled LDL levels and high triglycerides.  For the first time, the pure form EPA was shown to reduce the risk for heart attack, stroke and cardiac death by 25%.  The triglycerides were lower in patients on the medication, but it is thought that other mechanisms, such as an anti-inflammatory effect of the EPA, may also have contributed.  The results of this trial have changed the way cardiologists view and treat triglycerides in their patients with heart artery disease. Is fish oil beneficial for the primary prevention of heart disease? Two recent trials tested patients without heart disease by using a combination of EPA and DHA. Neither showed a reduction in heart attack, stroke or cardiac death. Therefore, low doses of fish oil are not beneficial for primary prevention but prescription high dose EPA is now being used for secondary prevention of heart disease. 

So, enjoy the holidays with friends and family. Have a holiday treat or two. If you want some heart healthy choices (including treats), try the recipes at heart.kumu.org. Then in the New Year, tackle those high cholesterol and triglyceride numbers.

Monday, November 5, 2018

The Gray Lady of the Medicine Cabinet


Aspirin is the gray lady of the medicine cabinet.  Aspirin, the medication that has been in use for over one hundred years, is tried, true and reliable. Aspirin has been prescribed for a variety of ailments including fever, aches and pains. Aspirin is the standard of care in the treatment of heart disease and stroke. Judging by its longevity and the extent of its use, it would seem that we know all there is to know about aspirin. That assumption would be wrong.

Aspirin’s anti-inflammatory and blood thinning properties are ideally suited for treating an acute heart attack or stroke. Aspirin is usually the first medication given in the ambulance to a patient who is having a heart attack. In addition, there is data going back decades showing that aspirin can prevent a second heart attack or stroke in patients who have already had an event. This is called secondary prevention and aspirin’s role is not controversial and well established.  What about primary prevention, trying to prevent a heart attack or stroke in a patient who has not had an event? Here aspirin’s role is much murkier and the data not as solid. A few primary prevention trials of aspirin were done many years ago and showed a small cardiovascular benefit for aspirin, even though the risk for bleeding increases with aspirin use. In 2016 the US Preventive Services Task Force recommended a low dose (81 mg) aspirin for adults aged 50 to 59 years old, who are at high risk for cardiovascular disease. What about patients who are 70 years of age or older, a population known to be at higher risk for cardiac events? Should an aspirin a day be prescribed?

Several large, well done primary prevention trials have recently been published and have added clarity. In a trial of 15,000 patients with diabetes (average age of 63), aspirin lowered the rate of cardiovascular events but increased the risk for major bleeding. There was no reduction in the death rate.  The next trial included 12,000 nondiabetic patients with the men over age 55 and the women over the age of 60.  These were patients felt to be at low risk for cardiovascular disease. Again, aspirin did not reduce mortality. There was no cardiovascular benefit for taking aspirin and the risk of bleeding was twice as high. The last trial included 17,000 patients all older than 70 years old and without cardiovascular disease. Once again, aspirin gave no benefit with respect to death, cardiovascular events, dementia or physical disability.  The risk for bleeding on aspirin was higher.  Overall these trials were consistent in showing that aspirin provided minimal benefit and significant bleeding risks. On the scale of benefit versus risk, the risk of aspirin outweighed any benefit in primary prevention.  What changed compared to previous primary prevention trials? The difference seems to be that the prevention of heart disease is much better now than in the past. Smoking is less common and the treatment of high blood pressure, high cholesterol and diabetes is better and more aggressive.

What is the correct dosage of aspirin? Even after all of these years, we still do not know for certain. Guidelines recommend a full dose (325 mg) of aspirin for at least one month after a heart attack, a cardiac stent, bypass surgery or a stroke. Then the recommendation is to lower the dose to 81 mg, with the idea that the lower dose confers the same benefit as the higher dose, but with less risk for bleeding. Now a new study questions the efficacy of 81 mg of aspirin.  It was found that low doses of aspirin, such as the 81 mg dose, were only effective in protecting against cardiovascular effects in patients weighing less than 150 pounds and had no benefit for those weighing more than 150 pounds.  This issue certainly will require further study.

All of these studies were reported in the news accompanied by headlines such as, “Aspirin Flops Big Time in Heart Study. Is it R.I.P for Aspirin?” This caused a lot of confusion among patients as to whether they should be on aspirin. To clarify, if you are having a heart attack or stroke, take an aspirin and call for help. If you have a history of heart attack, cardiac stent, bypass surgery, stroke, significant plaque in the neck (carotid) arteries, aorta or leg arteries, congestive heart failure or atrial fibrillation then the benefits of aspirin outweigh the bleeding risks.  If you do not have any of these conditions, then you should not take aspirin for primary prevention of cardiovascular disease. Instead, you should refrain from smoking, exercise regularly and take a statin and/or blood pressure medication as indicated.  Of course if there are any questions, talk over the risks and benefits of aspirin with your doctor.

Sunday, September 16, 2018

Even One Cigarette is Two Too Many


“Doc, I’m down to one cigarette a day”. That’s great, but you have to stop altogether. “I don’t want to gain weight if I quit. What do you think about e-cigarettes?”

Over the past several years, the number of people who smoke has dropped to an all time low. About 13% of US adults smoke, but that still represents about 37 million active smokers. The risks of smoking are well known. Heart attack, stroke, lung disease and cancer all increase with more smoking: the greater the number of cigarettes smoked and the longer a person smokes, the higher the risk for problems. Many people believe that cutting from smoking 20 to 25 cigarettes per day to only one or two per day will cut their risk. The idea is that a cigarette a day can’t be harmful. What is the data?  Researchers examined 5.6 million people and found that cutting the number of cigarettes from 20 per day to one per day reduced the risk for cancer, but the risk for heart disease persisted.  Compared to a nonsmoker, smoking 20 cigarettes per day increased the risk for heart disease in men by 100% (doubling the risk) and by 184% in women. Compared to those who never smoked, smoking only one cigarette per day increased the risk for heart disease by 50% in both men and women.  In addition, there is an excess risk for stroke with only one cigarette a day. The conclusion was that even one cigarette per day puts a person at significant risk for a heart attack or stroke. The goal must be zero cigarettes.

One of the barriers to quitting is that smokers don’t want to gain weight when they stop smoking. Given the fact that both smoking and obesity put people at risk for heart disease, which is worse, smoking or weight gain? Weight gain in quitters is the result of an increased appetite and lower energy levels.  The amount of weight gained after quitting is usually less than 10 pounds, but can be as high as 30 pounds. Weight goes up for about 5 years after smoking cessation and then slowly comes down.  In a recent study, it was found that stopping smoking reduced the risk for cardiac deaths regardless of weight gain.  This reduction occurred in those who gained weight and those who didn’t gain weight; the weight gain didn’t offset the benefits of smoking cessation on the death rate. The patients who gained weight also had more diabetes than those who didn’t gain weight. Even with weight gain and diabetes, there were less cardiac deaths. This data shows that smoking is worse than weight gain. 

What is the best way to stop smoking?  The main determinant is the smoker’s desire to quit. If you don’t really want to stop, then quitting will be nearly impossible. Some people can stop cold turkey. Most, however, need help in some form. Smoking cessation aids (such as nicotine patch, Chantix and Wellbutrin) can help people quit.  How safe are they? The cardiovascular safety of these aids has been tested in the general population of smokers and they do not increase the risk for heart attack and stroke.  The safety in patients with heart disease is not yet known. How effective are they? In a recent large trial only 3% of people using these aids were smoke free at six months. An emerging method of quitting is the use of the electronic cigarette (e-cigarette) or “vaping”.  The e-cigarette is a battery-powered device that heats liquid nicotine and flavorings (such as vanilla or cinnamon) into a vapor cloud that is inhaled. The data on e-cigarettes are still evolving, but preliminary studies show that they are less harmful than traditional cigarettes. Less harmful does not mean safe, however the degree of harm has not yet been defined. By altering the amount of nicotine in the device, smokers can titrate the nicotine down and quit slowly. However, a recent study showed that smoking cessation with e-cigarettes was not any better than other smoking cessation aids. The other major concern with e-cigarettes is their use in the adolescent population. Vaping has exploded amongst teens. Many studies have shown that e-cigarette use in young people doubles the odds of smoking traditional cigarettes. The FDA is now cracking down on e-cigarette manufacturers, trying to stop their advertising and sale of these products to teens.

In summary, the number one priority for any smoker is to stop smoking, using any means (going cold turkey or using smoking cessation aids or e-cigarettes) and then work to lose the weight that is gained. 

Thursday, September 13, 2018

My Apple Watch says that I am in Afib!

Apple just came out with a new watch. In addition to telling time and reading text messages and email, the new watch has electrocardiogram (EKG) capabilities. When the EKG detects an irregular heart beat (atrial fibrillation, Afib) it alerts the wearer. How well will this new technology perform in the real world?

Using Bayes calculation and assuming (a big assumption) that the Apple watch can detect Afib with a sensitivity of 99% and a specificity of 99%, we need to determine the prevalence of Afib in the population. This is not easy and there is scant data. Using Dr John Mandrola’s recent article in JAMAnetwork (“Screening for Atrial Fibrillation Comes with Many Snags”, August 2018), we can get a starting number. A study screening 75 to 76 year old Swedes found new Afib in 0.5% of the screened population.

If we put these numbers into Bayes formula, a pretest probability of 0.5% yields a post-test probability of 33%. In other words, if the chance a person has Afib is 1 in 200 and the watch detects Afib, the posttest probability of Afib is 1 in 3. This is a substantial increase and may be worth additional testing and perhaps treatment.

But…
We don’t know the true sensitivity and specificity. A sensitivity and specificity of 99% is almost never achieved by a diagnostic test, even the best tests come in at 90% to 95%. Testing the sensitivity and specificity of the Apple watch’s ability to detect Afib can be done and it won’t be a difficult undertaking. For example, Apple watches can be given to patients with pacemakers who go in and out of Afib. The watch can then be compared to the pacemaker interrogation to see if it accurately detects Afib and then the sensitivity and specificity can be calculated.  This study would not require too many patients, can be done in a short time and would not be that costly.

The true prevalence of Afib, however, is another story.  This will require a much larger and more extensive study. It would require many thousands of people, monitored for long periods of time (likely years) and would be very costly. In addition, the prevalence noted above is for older patients. The prevalence will be lower in younger unselected patients. If we cut the prevalence in half, to 0.25% or 1 in 400 people, then the posttest probability becomes 20%, still a substantial increase, but less impressive and more likely the watch will have produced a false positive. If the true prevalence is even lower, say by an order of 10 (1 in 2000 people or 0.05%), then the posttest probability is only 5%. It would be much more likely that the result would be a false positive.

The bottom line is that we don't know how accurate the Apple watch will be in detecting Afib. However, even if it's detection rate is nearly perfect, it ability to find Afib is dependent on the prevalence of Afib in the community. If there is a higher prevalence (as would be the case in older patients or heart patients who are hospitalized) then the chance of finding Afib is higher. If the prevalence is low, an irregular heart beat on the watch is more likely a false positive and not Afib. So, if your Apple watch says that you are in Afib, try to keep this in perspective.