Monday, July 13, 2015
There is a joy to be found in numbers and many sports fans have translated their appreciation of statistics to the level of passion because of fantasy sport leagues. The concept is simple. Managers and coaches devise on-field strategy based on their expectation of how the past might predict the future, and bettors rely on the same thought process. As it turns out, medicine works the same way, but the stakes may be a little higher.
A good example might be the approach to the patient with chest pain. While appreciating that there are many serious diseases and illnesses that can cause chest pain, pressure or tightness, most people and doctors worry about heart disease. The heart is a muscle and like any other muscle in the body, requires arteries to deliver oxygen and nutrients. If plaque and calcium narrow those arteries, a patient might experience symptoms during exercise or work or even walking upstairs. This is called angina and it may not be pain, but could be pressure or tightness of indigestion or perhaps nothing more than n indigestion or mild shortness of breath. If a plaque ruptures and a blood clot forms to completely block the artery, the section of heart muscle that it supplies will die if the blood flow is not re-established quickly. This is called a myocardial infarction or heart attack.
When a patient presents with chest pain to the ER, as protocol, the nursing staff may do an EKG, even before a doctor sees the patient. That EKG may diagnose the acute heart attack and the patient will head off to the cath lab to have a cardiologist open the blocked artery. But if the EKG isn’t exciting, it’s up to the doctor to decide whether to proceed down the “is it the heart?” pathway. Sometimes, clinical judgment says that the pain is coming from the esophagus, or lung or chest wall and no further heart testing is needed; but if the symptoms are suspicious and risk factors are present (smoking, high blood pressure, high cholesterol, diabetes and family history), more needs to be done.
Heart muscle that is irritated can leak a chemical, called troponin that can be measured in the blood. It takes a couple of hours or more for that test to turn positive, so an initial normal troponin is heartening but not necessarily conclusive. It means that no heart damage has yet been uncovered but a repeat test may be worthwhile.
A normal EKG and normal blood test means looking back in time that no heart damage has occurred, but does that mean that the heart arteries aren’t partially blocked? Is there a possibility of a heart attack in the near future? What do the statistics say about predicting the future and how low does the risk have to be before the patient and the doctor are happy?
The American Heart Association recommends that patients with chest pain, who are found not to have heart damage, should have their heart imaged in some way, within 72 hours of their visit. That imaging could be a stress test while walking on a treadmill, a radioactive dye injected to show blood flow to the heart, an echocardiogram (ultrasound of the heart), a cardiac CT or the gold standard and most invasive test, a cardiac catheterization. Each has its indications and place in the risk stratification of the patient, but the decision as to which test to order has some art mixed in with the science. All these tests are not cheap and requires a fair amount of technology, and may not readily be available.
Or the patient can assume some risk. There have been research and studies that have tried to put a number to that risk. In one group of patients who wee followed whose chest pain story was slightly or not suspicious for heart disease, who were younger and also had normal EKG and blood tests, the chance of having a major adverse heart issue within six weeks, was 1.7%. This number could drop to below 1%, if the patient were watched for a longer time frame and more blood tests done, but theirs never became zero.
Many patients and their families would accept a risk of less than 2%, meaning that more than 98 times out of 100, their heart was healthy. But the numbers also need to be looked at from the doctor and hospital perspective. A busy hospital ER might see a hundred or more chest pain patients each week. That less than 2% risk could add up to hundreds of missed heart attacks a year… not very acceptable numbers. While the Heart Association guidelines may be too strict, others may be too lenient and that is where clinical judgment, practical experience and common sense come into play.
Statistics may help drive strategy, but a manager’s gut feeling or game savvy may suggest a road less travelled when shifting fielder or changing pitchers. The art of medicine uses the same intuition to help guide the doctor and the patient to decide which plan of action is appropriate for one particular situation at one particular time. In medicine, statistics are fine for the general population, but when a complication happens, it happens 100% of the time to that patient. The goal of medicine is to maximize care, minimize risk and use resources wisely… and for that reason, doctors could learn a thing or two from managers, coaches and fantasy draft junkies.This entry was tagged CT, fantasy baseball, heart attack, statistics, troponin