Dr Larry Creswell
In my column today at the Endurance Corner website, I share part 2 in a series about endurance athletes and heart rate variability (HRV). Today, I talk about measuring HRV and how athletes might use HRV to help guide their training. Stay tuned for part 3, where I’ll talk about the available hardware and software options and summarize my thoughts on the subject.
NFL Broncos head coach, John Fox, will reportedly undergo aortic valve replacement (AVR) this week. I’ve gotten some inquiries over the weekend about his situation and I thought I’d take a few minutes to write about aortic valve problems and aortic valve replacement.
This story is reminiscent of Atlanta Falcons coach, Dan Reeves, who had urgent coronary artery bypass surgery in 1998, late in his team’s 14-2 season. For reference, Reeves made an excellent recovery, rejoined the team just 3 weeks after surgery, and went on to coach for another 5 seasons.
Aortic Valve Disease
The aortic valve is the valve that lets blood out of the heart. The left ventricle of the heart pumps blood out through this valve into the aorta with each heart beat. At rest, this might amount to about 5 liters per minute. The valve ordinarily has 3 tissue thin leaflets, but some individuals are born with just 2, a condition known as bicuspid aortic valve (BAV).
There are 2 different problems with the aortic valve. The valve can become narrowed or it can leak. Either situation produces trouble for the heart, which then must do extra work. When the valve is narrowed, we call the condition aortic stenosis. When the valve leaks, we call the condition aortic regurgitation. When there is severe aortic stenosis or regurgitation, aortic valve replacement is often the only available curative treatment.
In this country the most common cause of aortic stenosis in adult patients, by far, is build-up of calcium in the valve leaflets over many years’ time. This progressive calcification causes the valve leaflets to become thickened. As a result, they don’t open or close easily and eventually they become immobile. Severe aortic stenosis most often manifests in patients 60+ years old. In individuals with BAV, this process occurs much earlier in life, and the condition often manifests in patients in their 40’s and 50’s. Rheumatic fever is probably the next most common cause. The normal aortic valve opening is about the size of a half dollar. But with severe aortic stenosis, the opening can be reduced to the size of a drinking straw.
Aortic regurgitation may occur for a variety of reasons such as: infection (that we call endocarditis) that destroys the valve leaflets; enlargement of the aorta that stretches the leaflets apart; rheumatic fever; or trauma.
Patients with severe aortic stenosis have symptoms of shortness of breath with exertion, chest pain/discomfort, or light-headedness or blacking out (that we call syncope). Patients with aortic regurgitation most often have symptoms of shortness of breath with exertion. Either condition can be revealed by listening to the heart with a stethoscope because either condition produces turbulent blood flow that can be heard as a heart murmur. The diagnosis is confirmed using ultrasound, in a test known as an echocardiogram.
Once there are symptoms, patients with severe aortic stenosis need operation. Once the heart function suffers because of aortic regurgitation, operation is needed. In either case, we usually plan for operation at the earliest, convenient opportunity. Emergency operations for aortic valve problems are unusual.
In John Fox’s case, we know from reporting that he was in Charlotte, North Carolina to visit his doctor(s) about a known aortic valve problem–one that was being monitored and for which aortic valve replacement was being planned once this year’s football season was complete. The initial news reports spoke about the possibility of a heart attack, but he apparently became light-headed while playing golf. It’s not clear if he passed out completely. He was taken to the hospital where additional testing was completed. The Broncos then made the announcement that Fox would undergo surgery this coming week.
Aortic Valve Surgery
Aortic valve replacement is a very common heart operation today. And while there are new technologies that allow for valve replacement in high-risk patients without conventional operation, the vast majority of patients undergo typical open heart surgery to replace the valve.
The patient has general anesthesia with use of a breathing tube to provide ventilation while asleep. Access to the heart is gained by dividing all or part of the sternum and using a retractor to spread the rib cage open. The first main part of the operation involves connecting the patient to a heart-lung bypass machine that sits at the side of the operating table and takes over the job of the patient’s own heart and lungs for a period of time. This allows the patient’s heart to be still and empty of blood.
The next main part involves replacing the valve. An opening is made in the aorta, the large blood vessel that carries blood away from the heart. This allows the surgeon to look in and see the diseased valve. In the most straightforward operation, the patient’s aortic valve is removed using scissors and any calcium-related debris is also removed. A measuring tool is used to determine the correct size for a substitute valve which is then taken from the shelf. Sutures are used to sew the substitute valve into the opening left behind where the patient’s valve was removed. The opening in the aorta is then closed with sutures.
The last major part of the operation involves letting the patient’s own heart and lungs take back over again, and gradually reducing the amount of help that the heart-lung machine provides. Once the patient’s heart is beating again, the sternum is re-approximated with wires and the overlying tissues and skin are re-approximated using sutures. The entire operation usually takes about 3 hours.
There are several options for substitute valves. Mechanical valves are made out of space-age materials and are designed to last forever, but patients must take blood thinning medications to prevent blood clots from forming on the prosthetic valve. Tissue valves (eg, aortic valve “borrowed” from a pig) don’t require anticoagulants, but the valves don’t last forever. The modern tissue valves can be expected to last 10-15 years in adult patients and then some will deteriorate; re-replacement of the valve may sometimes be needed. In special circumstances, other more exotic options may be appropriate, but we won’t consider those options today.
Recovery from Operation
The typical patient wakes up soon after the operation. The breathing tube and ventilator are withdrawn once the patient is wide awake and breathing on his/her own. Most patients will spend a night in the intensive care unit and then several more days recovering in a regular hospital room. A typical stay would be about 5-7 days. We work hard to have patients up and walking on the first day after operation and most are walking laps around our hospital ward by the time they go home.
Many patients with AVR notice even in just the first couple days after operation that they no longer have the symptoms that led to discovery of their problem. Particularly for aortic stenosis, the calcification of the valve happens so gradually that patient’s aren’t always aware of how much of a decrement there’s been in their exercise tolerance.
As the sternum heals, we ask that patients avoid physical activities that place stress on the sternum and shoulders (eg, pushing, pulling, reaching, etc.) for 1 month after the operation. The sternum regains about 75% of its strength in about 1 month. In my practice we also restrict driving for that same month. Most any other activity is allowed and we encourage lots of walking as the preferred type of exercise.
Each patient’s situation with return-to-work is different, not only because each patient’s recovery is different but also because each patient’s job situation is different. In Fox’s case, if all goes well, I wouldn’t be surprised to see him back at work, at least in some capacity, very quickly.
Best wishes to John Fox!
Last week I got an inquiry from a reader about the prescription drug Adderall, asking in particular about the heart risks for athletes who might be taking the drug.
Although we’ll be talking about Adderall in particular, much of the information here will apply to other stimulants as well.
My quick take….
Like any drug, there’s both good and bad with Adderall. For athletes who legitimately need the drug, though, the heart risks appear to be small provided that the athlete doesn’t have any serious underlying heart problems. The drug can probably be used safely if both athlete and physician are aware of the potential risks.
What is Adderall?
Adderall is the brand name for a central nervous system stimulant composed of a 3:1 mixture of the salts of d-amphetamine and l-amphetamine. The U.S. Food and Drug Administration (FDA) has approved its use for the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy.
The drug is available in immediate release and extended release forms (Adderall XR) in dosages of 5-30 mg. Generic formulations are also available.
The U.S. Drug Enforcement Agency (DEA) has placed Adderall on its Schedule 2 list of drugs–those with a high potential for abuse, with the potential for leading to severe psychological or physical dependence. There are both federal and state regulations that apply to prescriptions for Schedule 2 drugs. In my home state of Mississippi, a handwritten prescription is required, refills are not permitted, and the prescription must be filled by a pharmacy within 90 days. There are stiff penalties for trafficking in Schedule 2 drugs.
In the United States, the prevalence of ADHD in children age 4-17 is nearly 10% and the prevalence in adults is nearly 5%. About two thirds of affected children are treated with prescription drugs.
Adderall and the Athlete
For athletes, there seem to be 3 relevant questions:
The Rules
For NCAA athletes, all stimulants are banned. There is a policy which allows for medical exceptions for banned substances that are used for legitimate medical purposes. In the case of Adderall, pre-approval from the NCAA is not needed for use, but the athlete must maintain documentation from his/her physician in the on-campus medical record that includes the diagnosis, course of treatment, and current prescription. If such an athlete is tested positive for the stimulant, the documentation is then used, after the fact, to obtain an exception from penalty.
All stimulants are included in the World Anti-Doping Agency’s list of substances that are banned in-competition. The WADA banned substance list has been adopted by all sports federations of the Olympic movement and many others as well. A complete list of signatories can be found at the WADA website. Athletes with a legitimate medical need for a banned substance can apply for a therapeutic use exemption (TUE). Information about the process for obtaining a TUE is posted at the WADA website. WADA recommends reassessment for the need for continued treatment every 3-4 months.
Adderall and other stimulants are banned by the National Football League (NFL), Major League Baseball, National Basketball Association (NBA), Major League Soccer, but athletes can obtain a therapeutic use exemption. Interestingly, nearly 10% of Major League Baseball players have obtained such an exemption. The drug is banned completely in the National Hockey League (NHL).
Competitive Advantage?
When used to treat ADHD, particularly as part of an comprehensive treatment plan that includes psychological, educational, and social measures, Adderall can be effective in reducing the inattentive or hyperactive-impulsive symptoms that are characteristic of the disorder.
In individuals without ADHD, the effects of Adderall are not characterized as completely. Nonetheless, there is reportedly increasing use of Adderall in this situation, particularly among college students and various athlete groups. In the college setting, students take stimulants like Adderall to increase their attentiveness and reduce their fatigue, especially in situations such as studying for exams or completing end-of-term projects.
There is also ample reason to believe that stimulants such as Adderall might provide a competitive advantage for athletes. From my vantage point, this issue doesn’t seem to be very well studied (in large part because of the bans), but there is at least some evidence to show that these drugs can produce increases in both strength and endurance, better concentration, and improve reaction time, especially when fatigued.
The Risks
For Adderall, like any prescription drug, information about the known risks can be found in the drug’s package insert.
Let me quote the entire black box warning:
Amphetamines have a high potential for abuse. Administration of amphetamines for prolonged periods of time may lead to drug dependence and must be avoided. Particular attention should be paid to the possibility of subjects obtaining amphetamines for non-therapeutic use or distribution to others, and the drugs should be prescribed or dispensed sparingly. Misuse of amphetamine may cause sudden death and serious cardiovascular adverse events.
A variety of side effects are mentioned in the package insert, including emergence of new psychotic or manic symptoms, aggression, long-term suppression of growth, seizures, and visual disturbances. Mention is also made that the effects of long-term usage are not well studied and that the usefulness of the drug for any particular patient should be carefully assessed periodically.
The package insert goes on to discuss cardiovascular warnings.
In children and adolescents, sudden death has been reported in patients treated with Adderall who also have heart problems like structural heart abnormalities, cardiomyopathy, or heart rhythm abnormalities. Patients with any of these heart problems are advised NOT to take Adderall.
In adults, sudden death, stroke, and heart attack have all been reported in patients taking Adderall at typical prescription dosages. It is recommended that patients with structural heart abnormalities, cardiomyopathy, serious heart rhythm abnormalities, or coronary artery disease should NOT take Adderall.
For any patient with high blood pressure, special precaution is advised when prescribing Adderall. Because Adderall is known to increase both the heart rate and blood pressure, special caution and careful follow-up is recommended.
Recommendations are offered for the cardiac evaluation of patients who are being considered for treatment with Adderall. Attention should be devoted to a careful medical history, family history (with particular attention to sudden death, ventricular arrhythmias), and physical exam that focuses on heart and vascular health. Additional investigation with EKG and echocardiogram may be indicated depending on the findings. Finally, patients treated with Adderall who develop any serious warning signs of heart disease (eg, exertional chest pain/discomfort, syncope or blacking out) should be re-evaluated.
Summary
In summary, Adderall is a stimulant that is effective for the treatment of patients with ADHD. Although prescription use of the drug is tightly controlled, there is ample prescription mis-use of the drug among individuals without ADHD or other medical reason for its use. For athletes, the drug is performance-enhancing and is banned by many sports organizations. Whatever its use, Adderall carries a small but real risk of serious cardiovascular side effects, especially among users with underlying heart conditions, whether known or unknown. Athletes and their doctors should be aware of these risks and consider cardiovascular screening and careful cardiovascular follow-up when this drug is used.
Related Posts:
1. Heart Medications, WADA, and the Athlete
Last weekend’s ESPN Outside the Lines show devoted to triathlon race safety is now available on podcast.
The show included a video report from ESPN reporter, T.J. Quinn and then a panel discussion that I joined along with Dr. John Mandrola and ESPN reporter Bonnie Ford.
If you missed the television broadcast, the podcast would be good listening for any triathlete.
I’ve talked here at the blog on many occasions about the health benefits of exercise. Once again, I’ll point out that those many benefits are undeniable.
Over the years, many studies have been devoted to questions like:
How little exercise is needed to produce those benefits?
What intensity is needed to enjoy those benefits?
Answers to those questions have guided the development of the various consensus guidelines about exercise as a part of healthy living. Check out the guidelines from the American Heart Association, World Health Organization, or the U.S. Centers for Disease Control.
Recently, though, there’s been increased attention paid to the potential issue of harm that might come to the heart because of too much exercise. The surprising–and rather serendipitous–finding of unusual scarring, or fibrosis, in the hearts of long-time marathoners has raised many important questions. In clinical practice, we usually associate such findings with serious heart problems. Yet the affected athletes may have gone a lifetime without any indication of a heart problem.
At least a couple working hypotheses have emerged:
1, Repeated episodes of seemingly routine, but intense exercise produces the harm, or
2. Increased inflammation from each episode, or a prolonged inflammatory state, produces the harm.
For now, let’s focus on the first hypothesis. And let’s consider the possibility that with even just a short period of intense exercise, a small amount of harm, or damage might come to the heart….and that little by little this damage accumulates over the years.
In today’s blog post, we’ll lay the necessary foundation for our discussion by developing some of the vocabulary we’ll need. In my next two posts, I’ll talk about what’s known regarding acute heart injury after running and after triathlon, specifically.
Skeletal Muscle and CPK
It’s long been known that periods of exercise can lead to skeletal muscle injury. In the early 1970s it was recognized that this injury was associated with release of proteins from the muscle cells into the bloodstream where they could be detected and quantified. The primary example is creatine phosphokinase (CPK), an enzyme that catalyzes the reversible reaction between creatine and phosphocreatine and is central to the muscle’s energy metabolism. When CPK is measured in the bloodstream as an indicator of muscle injury, we call the CPK a biomarker for muscle injury.
By the late 1970s enough investigation had been completed to know that elevation of the CPK could be mild in the case of recreational exercise or quite severe after efforts such as marathon running.
Heart Muscle and CPK-MB
It turns out that there are actually 3 different forms, or isoenzymes, of CPK. One of those forms, the CPK-MB is found almost exclusively in heart muscle. More than 98% of the body’s CPK-MB is found in the heart, while the remaining 2% is found in skeletal muscle. As a result, the CPK-MB can be used as a specific biomarker for heart muscle injury.
In clinical practice, a blood test showing elevation of the CPK-MB was used for many years as our way of confirming the diagnosis of acute myocardial infarction (MI), the condition that results from sudden, complete blockage of one of the coronary arteries. In the case of acute MI, there is a very characteristic pattern to the CPK-MB elevation found in the blood, with a rise in level very soon after the coronary artery becomes blocked, a peak level about 24 hours later, then a slow return to normal over several days’ time.
Exercise and the Cardiac Biomarkers
Around the time of the 1979 Boston Marathon, Dr. Arthur Siegel from Boston was interested in the newly available CPK-MB biomarker and enlisted 15 male marathoners to serve as subjects for a study. In their training leading up to the race, these runners were found to have borderline or slightly elevated blood levels of CPK-MB despite being completely healthy from a heart standpoint.
When their CPK-MB levels were checked 24 hours after the Marathon, there were elevations of up to 21 times normal, again without any other overt sign of a heart problem.
This was the first of many, many studies on cardiac biomarkers and exercise. We’ll talk about the results of these studies in more complete detail in my next two blog posts.
Today, the CPK-MB is seldom used clinically for the purpose of identifying cardiac injury. Instead, we measure cardiac troponin (cTn) which is even more specific for cardiac injury than the CPK-MB. But this newer biomarker works much the same way: with acute MI, there is a steady rise in the cTn to a peak level about 24 hours later, then a slow, gradual return to normal over several days’ time.
Exercise and Cardiac Structure and Function
In modern cardiology practice, we have many different diagnostic tests that help us define the heart’s structure and to asses its function. For the purpose of our discussion here, the important options are the echocardiogram (using ultrasound), the CT scan (using x-rays), and the MRI (using a powerful magnet).
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| Echocardiogram |
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| Cardiac CT |
In recent years, investigators have used these imaging tests to study the structure and function of the heart immediately after periods of intense exercise like marathon running or long-distance triathlon. The findings are intriguing.
Stay tuned for my next blog post devoted to acute heart injury–biomarkers and imaging tests–specifically after running events.
Related Posts:
1. Short-term and long-term injury to the heart with exercise
2. Can too much exercise harm the heart?
3. Don’t stop running yet!