Marathoning with mitral valve prolapse.
The mitral valve is one of the four valves of the heart, and it is located between the left atrium (where the blood flows from) and the left ventricle (where the blood flows to). It is the only valve with two small flaps, known as cusps; it is therefore sometimes called the bicuspid valve.
The mitral valve normally stops blood from flowing back into the atrium. A mitral valve prolapse (MVP) occurs when one or both of the flaps stick out back into the atrium during the normal ventricular narrowing that is designed to push blood into the aorta. When a flap sticks out, the valve fails to close properly and blood flows back into the atrium.
Most patients with MVP are asymptomatic. Some patients feel chest pain, irregular heart rate, weakness, or breathing difficulty. In severe prolapse cases, the leaky valve forces the heart to work harder. Over time damage can occur, including a swelling of the left side of the heart, known as valvular heart disease (VHD).
Mitral regurgitation (MR) is often but not always the result of MVP. It is considered an independent entity medically and can be a more severe condition that involves a lesion of the mitral valve, often from a birth defect. It too means that blood is leaking back into the atrium; the primary difference is the severity of the leak. MR is associated with definitive symptoms of breathing discomfort, irregular heart rate, and fatigue. Treatment depends on the dangerousness of the condition, and can include valve repair surgery in some cases where congestive heart failure may be occurring.
Unforeseen Athlete Deaths
On October 7, 35-year-old Michigan resident Chad Schieber collapsed and died during the Chicago Marathon. He was physically fit. His sister-in-law told reporters that he helped train police officers to become bicycle patrolmen. An autopsy revealed that Chad had MVP. This incident reminded many of another Chicago Marathon death: On October 13, 2003, Rachael Townsend, 29, also of Michigan, collapsed and died after a 3:40 finish in that race. Townsend taught physical education and coached soccer for six years. She was often spotted doing laps around the school's track and jogging around town. She, too, had MVP.
Unlike Jim Fixx or Danny Towns, the 45-year-old Oklahoma man who collapsed a few miles from his Chicago finish, these runners were not reformed smokers or previously overweight. Like Jim Fixx, Towns' autopsy revealed coronary arteriosclerosis.
So what is occurring here? What are the recommendations for people with MVP? How can they make intelligent decisions about fitness activity, and why does there sometimes seem to be a conflict between those recommendations and how things play out on race day?
First, be sure that the risk of sudden cardiac death in athletes, even those with underlying cardiovascular disease, is extremely low. Of the 10 to 15 million athletes of all ages who participate in organized sports each year in the United States, fewer than 300 die of cardiovascular-related causes. However, sudden cardiac deaths in competitive athletes are highly visible events. Sudden deaths have occurred in athletes of both sexes, in minorities, and in a wide range of ages and sports (most commonly basketball and football in the United States).
The American College of Cardiology (ACC), in conjunction with the American Heart Association (AHA), releases guidelines from time to time to assist doctors and the general public in their assessment of appropriate physical activity for people with cardiovascular abnormalities.
"Ventricular arrythmias" refer to a set of conditions associated with abnormal functioning of the walls within the heart cavities, relating to contraction and wall motion. Of these, ventricular fibrillation is the most serious. It is marked by a very fast, very uneven heart beat during which blood pressure falls to zero, the patient goes unconscious, and death may result within four minutes, unless defibrillation and ventilation are initiated immediately. Ventricular tachycardia refers to a fast heart beat that usually originates in a specific network of muscle fibers spread throughout the heart known as the Purkinje system. Ventricular tachycardias are faster than 100 beats per minute by definition.
In a 2006 publication focused on reducing incidents of sudden cardiac death in athletes with ventricular arrhythmias, the ACC/AHA stated that there is insufficient data demonstrating reduction in ventricular arrhythmias as a result of mitral valve repair or replacement in most patients with valvular disease (including severe MVP, severe MR, or serious ventricular arrhythmias). For these reasons, patients with VHD and ventricular arrhythmias should be evaluated and treated following current recommendations for each disorder. Those recommendations in turn state that:
"In most patients, the MVP syndrome is associated with a benign prognosis. The age-adjusted survival rate for both men and women with MVP is similar to that of individuals without this entity. Sudden death is a rare complication of MVP, occurring in fewer than 2% of known cases during long-term follow-up, with annual mortality rates less than 1% per year. The likely cause is a ventricular tachyarrhythmia ... a normal lifestyle and regular exercise are encouraged for most patients with MVP, especially those who are asymptomatic."
The report goes on to say that whether exercise-induced ischemia develops in some patients with MVP remains controversial. Restriction from competitive sports is recommended when moderate left ventricle enlargement or dysfunction is noted. Also, uncontrolled tachyarrhythmias, prior resuscitation from cardiac arrest, or aortic root enlargement "is present individually or in combination."
The above recommendations come from a 2006 publication focused on management of patients with VHD and developed by the ACC/AHA in collaboration with the Society of Cardiovascular Anesthesiologists, and endorsed by both the Society for Cardiovascular Angiography and Interventions and the Society of Thoracic Surgeons.
Similarly, the 2005 ACC/AHA task force report on eligibility for competitive athletes with cardiovascular abnormalities recommended that "athletes with MVP--but without high risk features--can engage in all competitive sports." Those features include prior fainting spells, thought to be due to a rhythm disturbance, family history of MVP-related sudden death, severe MR, abnormal left ventricular pump function, a prior stroke, or repetitive, complex heart rhythm disturbances.
So now let's look at these marathon-related deaths in Chicago further.
The 2007 race saw the highest temperatures not only in Chicago Marathon history, but, at 88 degrees, record temperatures were recorded for October 7 in general. Race officials cancelled the race, also for the first time in the Chicago Marathon's history, after just three and a half hours. Some 315 runners were taken from the course by ambulance with heat-related conditions. Five people remained hospitalized in serious or critical condition that Sunday night. Runners described chaotic scenes of racers throwing up, passing out or being carted away on stretchers. Of the 35,867 runners who started the race, just 24,933 finished.
And here is what the newspaper had to say in 2003: "With a high of 71 degrees, Sunday ranked among the warmest Chicago marathons ever ... Dr. Greg Ewert, the Chicago race's medical director, said the warmer weather made the medical tents at the finish line busier than usual ... Many of those treated in the tent after the race had heat exhaustion and up to 104-degree body temperatures, typified by symptoms of fatigue, nausea, cramping and disorientation. Others had heat stroke, with temperatures above 104." The medical director went on to report that those who felt sick were sicker than usual. This statement speaks to the heart of the matter.
Physicians almost universally agree that MVP in and of itself is not the cause of these athlete sudden deaths; there are almost always other causes involved. The heart problem blamed in the death of Chad Schieber is rarely dangerous and people who have it shouldn't stop exercising. As cardiologist Phillip Watkins, MD, puts it, "People are not dying in the streets because they have mitral valve prolapse." Watkins works in a Birmingham, Alabama, center that specializes in treating the problem.
Experts make a distinction between MVP and severe MVP. If the condition is mild, it requires no treatment. If it is severe, an operation can be done with low risk. The Chief Medical Examiner in Cook County reported that Schieber had "significant mitral valve prolapse." And while an autopsy found the death was not related to heat stress, the high temperatures that day undoubtedly contributed to Schieber's demise. Dehydration could have been a factor. The victim's family said Schieber encountered at least one water station that had no water.
Running a marathon even on a hot, humid day wouldn't be extraordinarily dangerous for most people with MVP, assuming they trained and stayed hydrated during the race. But athletes with any type of heart condition can be more susceptible to heat and dehydration.
Rarely, MVP can cause a sudden rupture in the fibrous tissue connecting the valve to the heart muscle, leading to severe leakage of blood into the lungs. Robert Bonow, MD, who is chief of cardiology at Northwestern University's Feinberg School of Medicine, says, "That can be fatal, especially under extreme circumstances, such as exertion or hot weather."
Significant mitral regurgitation can be caused directly by MVP. If severe enough, MR can lead to enlargement of the cardiac chambers, weakening of the heart muscle, and ultimately, to heart failure. Fortunately, MVP tends not to cause significant MR. Only about 5% of patients with true MVP develop it in their lifetimes.
However, systematic training in endurance sports may trigger physiologic adaptations and structural remodeling of the heart, including increased left ventricle wall thickness, cardiac mass, and cavity dimensions. This is often referred to as "athlete's heart". Other potential adaptations include a variety of abnormal ECG patterns, which can mimic those of cardiac disease. These adaptations are seen in some 40 percent of elite athletes. Frequent or complex ventricular tachyarrhythmias are not uncommon in athletes and also are similar to symptoms of cardiac disease.
Furthermore, running a marathon injures muscle tissue, triggering an inflammatory response that makes the blood more prone to form clots that can cause heart attacks. Arthur Siegel, MD, of McLean Hospital in Massachusetts took blood samples from 80 Boston Marathon runners before and after the race. The morning after, he found elevated levels of inflammatory and clotting factors in the runners' blood.
These ambiguities in the relationship between intense physical activity and heart health contribute to the public's misperception of MVP and marathoning as a dangerous mix. Another complicating issue may be that race officials do not want to be held responsible for athlete deaths in extreme temperatures, and so can be tempted to blame a person's well-documented, lifelong medical condition to explain the death, at least to the media.
What to Conclude?
Remember that training demands vary considerably even within the same sport. The demands of competitive sports may place athletes with certain cardiovascular abnormalities in extreme or unpredictable environmental conditions. These can be associated with alterations in blood volume and in hydration and electrolyte levels, circumstances which could enhance the risk of potentially lethal arrhythmias.
However, because MVP is common, it has been associated with a myriad of conditions that probably do not have anything to do with the MVP itself. While it is commonly believed that MVP causes chest pain and heart palpitations, most individuals with MVP do not experience them.
It is not at all clear that mild MVP is in any way associated with sudden death, let alone a cause of it. A small number of patients with MVP will eventually develop significant MR, which in turn can produce heart muscle weakness--and these patients do have an increased risk of life threatening arrhythmias. This is why it is vital to distinguish MVP from MR, even if the one can occasionally cause the other. Patients with severe mitral regurgitation--from any cause--have an increased risk of stroke and sudden death, but the vast majority of patients with MVP have never been shown to have any higher risk of sudden death than the general population, and the recent tragedies in Chicago should not cause undue concern.
If you do have MVP, make sure you understand from your physician the degree of MR that you have. It's also important that your doctor has a schedule for outlining and monitoring this degree over time. If you have chest pain or palpitations, these symptoms ought to be evaluated as separate entities.
"Eligibility Recommendations for Competitive Athletes with Cardiovascular Abnormalities," J Am Coll Cardiol, 2005, Vol. 45, No. 8, pp. 1318-1321, http://content.onlinejacc.org/cgi/content/full/45/8/1318;
"Guidelines for Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death," J Am Coll Cardiol, 2006, Vol. 48, No. 5, pp. 1064-1108, http://content.onlinejacc.org/cgi/content/full/48/5/1064;
"Guidelines for the Management of Patients with Valvular Heart Disease," J Am Coll Cardiol, 2006; Vol. 48, No. 3, pp. el-e148, http://content.onlinejacc.org/cgi/content/full/48/3/el;
Mosby Medical Encyclopedia, revised ed., 1992, Plume, pp. 510, 818;
American Family Physician, 2005, http://findarticles.com/p/articles/mi_m3225/is_3_72/ai_n14888498; "Does Mitral Valve Prolapse Cause Sudden Death?" by Richard N. Fogoros, MD, About.com, October 9, 2007, http://heartdisease.about.com/b/a/254777.htm, http://heartdisease.about.com/cs/mvp/a/MVP.htm;
The Texas Arrhythmia Institute, http://www.txai.org/edu/irregular/ventricular_tachyarrhythmias.htm; "Runner's Death Still a Mystery," Chicago Tribune, October 15, 2003;
"Man Dies in Heat-shortened Marathon," by Josh Noel, Andrew L. Wang, and Carlos Sadov, Chicago Tribune, October 7, 2007;
"How Marathons Can Kill You," by Jim Ritter, Chicago Sun Times, October 6, 2002;
"Runner's Heart Defect Usually Not Fatal," AP, New York Times, October 9, 2007