Killer Workouts - The Adult Athlete
A CardioAdvocate Phenotype
Case Presentation: The Tragedy of Jim Fixx
The death of Jim Fixx (JAMES F. FIXX DIES JOGGING; AUTHOR ON RUNNING WAS 52 — The New York Times) is probably the example most cited by our patients, but many of us athletes have either personally witnessed or been told of an athlete dropping dead in the middle of a race or event. Leading up to such an event, this author was interviewed by a news outlet in an effort to promote awareness and screening. Despite these efforts, there was a follow up interview the day after the race, discussing the ultimate tragedy - sudden cardiac death just after the finish line. How could this be?
While this article is generally focused on the cardiometabolic manifestations related to exercise, there are several examples of less common, but critically important congenital conditions that deserve to be at least mentioned when discussing exercise and the risk of sudden cardiac death. Particularly since exercise, to include weight lifting, is such an important and recommended component of heart healthy living.
A thorough review of all causes of SCD related to exercise is beyond the scope of this article, but some notable examples are worth touching on.
For example, getting deployed overseas is a great time to focus on health and fitness and come home shredded. Events such as deadlift competitions, however, can produce extremely high intrathoracic and arterial pressures (Aortic dissection type I in a weightlifter with hypertension: A case report). Acute aortic dissection and death (personal knowledge) have been reported in weightlifters during such extreme activities. Such cases are rare, but appropriate screening and knowledge of family history may have prevented these tragic events. Intense isometric exercise is contraindicated (inadvisable) in individuals with predisposition for aortic aneurysm or aortic rupture.
Flying Under the Radar
The "Healthy Athlete Bias"
Ironically, some of the fittest people, despite a sometimes consuming attention to healthy lifestyle behaviors fail to screen themselves appropriately for the most lethal disease in our society.
Healthy athletes often fall short on screening for heart disease due to a "healthy athlete bias" whereupon they and their clinicians place too much emphasis on what are called "modifiable risk factors." These are risk factors one has control over such as diet, exercise and smoking. Disproportionately less emphasis is "non-modifiable risk factors" which are risk factors one has no control over, such as genetics. As we often like to say "you cannot pick your parents, nor run away from your genetics." This bias negatively impacts the athlete, who tragically gets less attention from the healthcare system.
Reinforcement of this bias is not hard to find. For instance, while watching a sporting event on television, one commercial from a local healthcare system contends that up to 80% of heart disease can be prevented through proper diet and lifestyle choices. It then cuts away to show healthy appearing people jogging on a trail and doing pushups. An athletic individual watching at home may resemble these actors and have the impression that they are somehow protected.
The reality is nearly ¾ of young patients (Men < 55 and women < 65 years of age) presenting to the hospital with their first heart attack, would've never qualified for a statin based upon conventional risk calculators. This demonstrates the difficulty in conventional screening calculators in the apparently healthy and particularly younger patient.
CardioAdvocate Checklist: The Adult Athlete
Foundation: Family History
- Genetic Testing is available if indicated:
Pre-Exercise Evaluation
- MESA 10-Year CHD Risk with Coronary Artery Calcification
- ASCVD Risk Estimator +
- SCORE2 and SCORE2-OP calculators
Laboratory Screening
- Lp(a) is another atherogenic lipoprotein causal to atherosclerosis
- > 125 nmol/L (50 mg/dL - less preferred assay) - associated with heightened risk of premature ASCVD, often presenting as heart attack or stroke
Imaging Screening
- Most exercise related cardiac arrest in those over 45 are due to coronary artery disease
- Calcium Scores can detect the presence of occult coronary artery disease in 1 in 5 "middle aged sportsmen" > 45
- Evidence to screen at age > 35
Action and Follow-Up
- Review testing
- Discuss any additional testing or treatments as dictated by screening
Deep Dive: Understanding Exercise and Cardiac Risk
The Jim Fixx Story: A Cautionary Tale
Jim Fixx was not exactly the healthiest of athletes at baseline. He was 35 when he took up running (Running, Heart Disease, and the Ironic Death of Jim Fixx | Cardiology in Review). He had numerous risk factors, to include smoking 2 packs per day, being overweight at 220 lbs, a strong family history of premature coronary artery disease - his father suffered his first heart attack at age 35 and died after a second heart attack at age 43, high stress as editor of a magazine and 2 divorces.
Jim Fixx wrote a best-selling book about running. He was among other running authors of that era who encouraged readers to "listen to their bodies, instead of doctors". But in yet another twist of irony, he did neither. He ran through his chest pain. Autopsy revealed severe obstructive 3-vessel coronary artery disease with 95%, 85% and 70% blockages as well as multiple infarcts in multiple stages of healing.
Historical Context: SCD in Athletes
While smoking certainly confounds the death of Jim Fixx, the death of an apparently healthy athlete is a perplexing and frightening event. But it is not new. Indeed, Pheidippides died shortly after running a marathon from Marathon to Athens in 490 B.C. Today, Sudden Cardiac Death (SCD) during sports occurs in 5-6% in the general public. There is a 9:1 male to female ratio in those > 35 years age, considered the "older athlete".
Sudden cardiac death risk for runners has been reported as 0.8 to 2 per 100,000 marathon runners. 54% are over age 35. 57% are male.
While that may not seem like a lot, when you consider there are approximately 20 million athletes (and growing) participating in foot races in the US annually, with a running craze that is attracting a more aging population, you are bound to hear about it in your community. For instance, a popular community race in Spokane, WA called "Bloomsday" brings about 45,000 runners participating in a 7.4 mile run. In 2018 there was 1 death near the finish line and reportedly 7 or 8 collapses that day. There was an aborted Sudden Cardiac Death in 2017 thanks to the quick action of nearby healthcare workers. This shocked the community and was well covered by the local news stations.
Does Exercise TRIGGER the Heart Attack?
There is relatively sparse information on this question. There is evidence that suggests long term exercise is protective against atherosclerosis.
However other data suggests exercise CAN trigger a heart attack. But the above study suggests that the more sedentary an individual is, the more likely it is that HEAVY physical exertion will provoke an MI. Habitual and moderate to high intensity exercise appears to reduce this risk (Triggering of Sudden Death from Cardiac Causes by Vigorous Exertion, Leisure-time physical activity and the risk of primary cardiac arrest).
What's the Mechanism?
Not entirely clear. Possible mechanisms are sympathetic activity, ischemia, activation of hemostatic system, hemodynamic effects on vulnerable plaque, electrolyte and metabolic factors with prolonged exercise. Indeed, the length of the activity appears to be a factor. The majority of SCD occurs in the last ¼ of a marathon. There are more SCD events during marathons than ½ marathons.
Higher Coronary Artery Calcification in Athletes
Progressive or premature coronary artery calcification has been associated with chronic intense exercise as well. It is unclear whether such athletes have the same risk as nonathletes with similar high CAC scores.
More research is needed on this important topic.
The Verdict: Is Heavy Exercise Dangerous?
Exercise is medicine. Movement is medicine.
When tragedy strikes, it's usually the "older" athlete (> 45 years of age) and usually due to coronary artery disease. Appropriate screening, particularly with Coronary Artery Calcium CT scans, can detect coronary artery disease in such patients. We have the tools to treat this. It's not hard.
Can Too Much Exercise Cause Other Cardiac Issues?
The Exercise Dose Question
There can potentially be pathologic changes related to the ongoing effects from intense exercise. It's debatable whether there exists a "J-shaped" curve when it comes to exercise intensity and volume. What this means is that as one begins to exercise, a small to intermediate amount of exercise intensity and volume offers protection, or an advantage over those who don't, when it comes to death or cardiac death and other cardiac related problems. But as exercise intensity becomes more extreme, it may begin to negatively impact the risk for death, cardiac death or other bad cardiac problems. In other words, is there an appropriate "dose" of exercise that is ideal? Like Goldilocks. Not too little, not too much.
Based upon the Copenhagen Male Study, there appears to be a "dose-dependent" increase in lifespan with higher cardio fitness. Meaning, NO J-shaped curve.
Exercise and Existing CAD
For those with known CAD, we have evidence that participating in cardiac rehab results in a 27% reduction in TOTAL MORTALITY!
The Heidelberg Regression Studies demonstrated some evidence of regression by angiography among other findings (improved myocardial O2, measures of ischemia, well being, work capacity). Plaque regression was seen, but only in those spending 5-6 hours/week in leisure time.
Atrial Fibrillation in Endurance Athletes
Atrial fibrillation is 8 times more likely to occur in endurance athletes, likely due to both mechanical and electrical remodeling of the left atrium in the setting of increased flow.
Screening Recommendations for Athletes
Pre-Participation Screening Controversy
There is considerable controversy over preparticipation sports screening with EKGs and or echocardiograms due to the likelihood of false positive studies. The problem is that many athletes have "abnormal" EKGs due to normal or benign variants produced by cardiac "remodeling" in the setting of "athletic heart." This includes eccentric left ventricular hypertrophy, right ventricular enlargement, atrial enlargement and various heart rhythm or conduction abnormalities, generally due to high vagal tone in athletes (generally a sign of optimal conditioning) such as marked sinus bradycardia, first degree AV block, ectopic atrial rhythm, junctional rhythm, incomplete right bundle branch block, right bundle branch block and more.
Young Athletes (< 35 years)
Proponents of screening wish to rule out less common but potentially catastrophic congenital abnormalities (see below) more likely seen in the "younger athlete," defined as < 35 years of age. In North America, for the young athlete, a history and physical exam (H&P) is recommended. Use of EKGs, Echocardiograms and stress testing are not recommended.
Older/Master Athletes (> 35-40 years)
For the "Master Athlete" (Age > 40 years) an EKG is also recommended by the AHA. In the US, for those with moderate to high risk (Anyone over age 65 or Men > 40 years old, Women > 50 years old with 1 risk factor such as hypertension, hyperlipidemia, diabetes, smoking, premature MI/SCD in 1st degree relative) an exercise stress test is recommended.
European Screening Guidelines
In Europe, it is recommended to use routine H&P and an EKG to rule out HCM and channelopathies. There is a higher prevalence of ARVC amongst Italians, for instance.
For the Master Athlete in Europe, it is a bit more comprehensive (Cardiovascular evaluation of middle-aged/ senior individuals engaged in leisure-time sport activities: position stand):
- H&P, ECG
- Assess baseline physical activity and anticipated exercise intensity
- Baseline risk profile: SCORE2 and SCORE2-OP calculators
- If not low risk: exercise ECG
- If borderline or abnormal stress ECG, then proceed with Stress Echocardiogram or Nuclear stress test
- If stress echocardiogram or Nuclear stress test is positive, proceed with Cardiac CT Angiogram or diagnostic heart catheterization (conventional coronary angiography)
Less Common but Critically Important Conditions
A thorough review of all causes of Sudden Cardiac Death is beyond the scope of this article. A brief description of the more common and serious conditions are listed below.
Marfan Syndrome
Marfan syndrome is a connective tissues disorder which can lead aortic dilatation and carries a much higher risk of aortic rupture or aortic dissection as well as mitral valve prolapse and other cardiomyopathy.
Exercise guidelines for patients with Marfan Syndrome can be found here: Physical Activity Guidelines - Marfan Foundation
Hypertrophic Cardiomyopathy (HCM)
Hypertrophic Cardiomyopathy is a genetic condition afflicting the heart muscle of the left ventricle, causing it to thicken and often obstruct blood flow leaving the left ventricle. The tissue itself shows signs of chronic and progressive low grade inflammation. It carries a higher risk of heart failure and sudden cardiac death due to arrhythmias and/or obstruction of blood flow and pump failure.
Anomalous Coronary Arteries
#1 cause of sudden cardiac death in military recruits, largely because this anomaly evades routine health screening in recruits, since it cannot be found by physical exam or EKG.
There are various forms of anomalous coronary arteries. Some are benign and some are better described as normal "variants" of anatomy. But there are others that are deadly, particularly when the left main coronary artery arises from the right coronary cusp and must make its way to its intended destination by traveling between the Pulmonary Artery and the Aorta.
Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia (ARVC or ARVD)
ARVC/D is a genetic condition characterized by fatty infiltration of the right ventricle (and sometimes into the left ventricle), leading to right ventricular dysfunction and a risk of SCD from ventricular arrhythmias. It tends to be seen more commonly in young competitive athletes. Higher intensity exercise is associated with younger presentation of symptoms and greater likelihood of arrhythmias.
A review of exercise can be found here: Physical Exercise and Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia: An Overview.
This review provides the following about exercise recommendations: "Recreational sport or low-to-moderate intensity exercise may not be detrimental and ARVC/D individuals should not be completely deprived of the benefits of exercise. Exercise restriction advice is an integral part of management for both individuals with established disease and those who carry gene mutations."
Catecholamine Polymorphic Ventricular Tachycardia
In this condition, ventricular tachycardia with possible degeneration to ventricular fibrillation and sudden cardiac death can occur due to adrenergic (adrenaline) stimulation from exercise. Onset generally occurs in children and adolescents. Avoidance of strenuous exercise and very stressful environments is recommended.
Long QT Syndrome
Congenital Long QT is an inherited ion channelopathy which causes a prolongation of the QT segment on an EKG, which represents a particularly vulnerable part of the heart cycle for dangerous arrhythmias to occur. Older guidelines have restricted competitive sports, feeling this could precipitate more dangerous arrhythmias, leading to sudden cardiac death. More recent guidelines have been less restrictive. An informative review can be found here: Long-QT Syndrome and Competitive Sports.
