Category Archives: Cardiac Tests

Searching for Subclinical Atherosclerosis: Vascular Screening

I reviewed in a previous post  the importance of detecting sublinical atherosclerosis when trying to assess someone’s risk of heart attack and of dying suddenly.  Subclinical atherosclerosis refers to the build-up of plaque in the lining of our arteries which occurs long before any symptoms of atherosclerosis occur.

Since the process tends to be diffuse, occurring in all the large arteries of the body, it makes sense that if we can easily visualize one artery this will give us a window into what is happening in other arteries (including the coronary arteries supplying blood to the heart muscle).

Vascular Screening

The vascular screening I offer in my office uses high frequency ultrasound to image the large artery, the carotid artery, that supplies blood to the brain.

normalimtNormally the lining of that artery is smooth and thin as in the example to the left. As the process of atherosclerosis works its damage on the artery lining it becomes thicker and plaque begins to develop. High frequency ultrasound is an excellent tool for identifying these early, subclinical stages of atherosclerosis because it is painless, harmless, inexpensive, and quick. 

Identifying Higher Risk Patients

Mr. M is  a 60 year old man who I was seeing for an abnormal heart rhythm. Using the ACC risk estimator I calculated his 10 year risk of atherosclerotic cardiovascular disease (ASCVD) as <7.5%. However, he had a brother who had cardiac stents placed in his coronary arteries (indicating coronary artery disease (CAD)). His carotid artery screening (shown below) shows a large, soft plaque

Large, relatively echo lucent (soft) plaque found in the internal carotid artery of Mr. M.

This indicates that although his known risk factors for atherosclerosis were not tremendously high, the combination of known and unknown factors (likely genetic, given his brother’s premature CAD) were damaging the lining of his arteries leaving him at a  high risk for stroke and heart attack.

 

A patient like Mr. M I consider to have documented atherosclerotic cardiovascular disease (ASCVD)and I  will strongly recommend statin therapy along with a baby aspirin

Several studies have shown in those patients who are reluctant to start statin therapy, documenting subclinical atherosclerosis serves as a strong motivational factor for lifestyle change or compliance with medications.

Identifying Lower Risk Patients

Equally important as identifying advanced subclinical atherosclerosis, imaging the carotid artery can identify those patients who are at lower risk and save them from a lifetime of unnecessary treatment.

Ms N is 64 years old whom I see h for high blood pressure and supra ventricular tachycardia (an abnormal heart rhythm). She has a total cholesterol of 219, HDL(or good) cholesterol of 74, systolic blood pressure of 130 and the ACC risk estimator gives her an 8.4% risk of ASCVD over the next 10 years. She greatly dislikes taking medications, but her mother died in her early fifties from  a “massive heart attack” .

huelsingHer carotid exam shows the carotid thickness as less than average for her age and gender, equivalent to that of a 58 year old. There is no plaque anywhere in her carotid system. I feel comfortable not recommending statins to this type of patient. In many cases, I often  stop cholesterol treatment in patients with no evidence for subclinical atherosclerosis who have marginal cholesterol levels and intermediate risk.

What vascular screening allows me is the ability to see if my patients do or do not have the disease that we are trying to prevent or mitigate: atherosclerosis.

As the skeptical cardiologist I must point out that national guidelines do not endorse vascular screening primarily because there are no randomized controlled trials showing that it influences outcomes. I’ll talk more about potential pitfalls of vascular screening when done by for profit ventures in a subsequent post  and we’ll discuss the other good way of assessing for subclinical atherosclerosis: coronary calcium.

 

Searching for Subclinical Atherosclerosis: Am I about to drop dead?

Nearly every day I see a patient in the office who has just experienced a friend or relative suddenly “dropping dead.”  Understandably, they are very concerned about this and want to know “Is this going to happen to me?”

There is very good reason to be concerned. Cardiac disease is the leading cause of death in America. Despite considerable progress, regrettably 50% of deaths occur suddenly, without any previous symptoms which would have suggested a cardiac problem. It doesn’t just hit the overweight or the smoker. It not uncommonly strikes the very fit and seemingly healthy, as in the case of the St. Louis Cardinal pitcher, Daryl Kile, who was found dead in his hotel room at the age of 34. This question of who is going to suddenly drop dead (sudden cardiac death or SCD) is one of the fundamental unsolved mysteries in current cardiology.

Atherosclerosis and Dropping Dead

Most SCD in individuals over the age of 35 is related  to the development of fatty plaques (atherosclerosis) in the arteries that supply blood to the heart (coronary arteries) and the subsequent sudden rupture of these plaques (thrombosis).hrtatk-07 The result of this rupture is the complete blockage of the artery and the total cessation of blood flow to a portion of the heart muscle. When that heart muscle portion becomes starved for oxygen, the muscle cells start dying and a myocardial infarction (MI) or heart attack occurs. You can view an animation of this process here With any MI, the dying muscle cells can become electrically irritable and initiate an abnormal heart rhythm called ventricular tachycardia (VT) or ventricular fibrillation (VF). This abnormal rhythm is what causes people to “drop dead” suddenly. Basically, the heart cannot pump blood efficiently in VT or VF; thus, there is no blood flowing to the brain and other vital organs. This is a long, complicated chain of events, but basically it begins with the development of fatty plaques or atherosclerosis. It makes sense that we can stop people dropping dead from MI by stopping the development and progression of atherosclerosis. Atherosclerosis develops long before any clinical signs or symptoms of disease. You can feel totally fine and have a huge build up of plaque in all of the arteries of your body. This is termed subclinical atherosclerosis. It makes sense, and it has been scientifically proven, that those with a huge buildup of plaque (high plaque burden) are at higher risk for MI and death than those with low or no plaque burden. It also makes sense that treating those patients with high plaque burden will be most beneficial.

How Do you know if you have atherosclerosis

I discussed the standard recommended method for determining risk of MI/SCD in my last post on statins. Basically, this is simply adding up the factors we know contribute to atherosclerosis: diabetes, cigarette smoking, hypertension, age, gender and cholesterol levels. However, most heart attacks and strokes occur in people who are classified by traditional risk factor scoring as low or intermediate risk. Conversely, others are misclassified as high risk and mistakenly advised to take drugs to reduce their risk factors for the rest of their lives.

How Can We Detect Subclinical Atherosclerosis?

In my office practice I offer patients two tests which directly detect and quantify subclinical atherosclerosis. One looks for plaque  and thickening in the larger arteries of the neck, the carotid arteries, and one looks for calcium in the coronary arteries. I’ll go into detail about both of these in subsequent posts. For now, I will just say that the carotid screening technique uses harmless ultrasound while the coronary calcium technique uses ionizing radiation from a CT scan. Neither test is covered by insurance or Medicare. Both tests have been shown to improve our ability to identify those at risk for MI and stroke.

These tests are helpful in two general areas:

*The first scenario is the patient who appears to be at low or intermediate risk for atherosclerosis based on the risk estimator, but who has a strong family history of MI, sudden death or stroke. If we identify significant subclinical atherosclerosis in this patient, statin therapy is more likely to be beneficial.

*The second scenario is the patient who has been put on statins for primary prevention based on standard risk estimator but has no family history of ASCVD and is questioning the need for treatment. In this patient if we find no subclinical atherosclerosis, a strong argument can be made to stop the statin drug.

SHAPE Guidelines II Slide_Page_38
Proposed method for utilizing carotid vascular and coronary calcium tests for better identification of subclinical atherosclerosis and more appropriate utilization of treatment in order to prevent heart attacks and sudden cardiac death

There is an organization dedicated to promoting the detection of SA by these tests and an algorithm for treatment called SHAPE  (Society for Heart Attack Prevention and Education). Interestingly, after a female Texas state representative suffered an MI, in 2009, Texas Governor Ricky Perry signed off on the Texas Heart Attack Prevention Bill mandating health-benefit plans to cover screening tests for SA. No other state to my knowledge has such a law.

How to Stop Sudden Cardiac Death

The two tests I mentioned are a good second step towards identifying the individual at risk for MI and SCD but we still don’t know who among those with advanced subclinical atherosclerosis is going to experience a sudden rupture of plaque, have an MI and drop dead.

We need a way to identify those patients with vulnerable plaque (one that is about to rupture) and aggressively treat those patients. This is an area of intense research focus. You can view a fascinating video (accompanied by weirdly cool music) created by SHAPE here and another (featuring a gun shooting a heart) here emphasizing the importance of the vulnerable plaque.

Should You Get a Routine Annual Electrocardiogram (ECG)?

Recently, the skeptical cardiologist  was asked by his  old friend and life coach (OFALCSC) whether he was correct to refuse the annual electrocardiogram (ECG) which his primary care doctor had recommended during an annual physical.

ECG showing atrial fibrillation
ECG showing atrial fibrillation

Most of my patients feel that the ECG has the ability to tell me  quite a bit about their heart. The technique utilizes electrodes on the arms, legs and chest region which  record with precision, the depolarization and repolarization of the upper chambers (atria) and lower chamber (ventricles) of the heart.

The ECG is THE tool for assessing the rhythm of the heart.  If performed and interpreted properly (not always a given) it tells us very precisely whether we are in normal (sinus) rhythm, wherein the atria contract synchronously before the ventricles contract, or in an abnormal rhythm. It is also very good at telling us whether you are having a heart attack.

If you are, however, like the OFALSC, and feel fine (meaning without symptoms or asymptomatic), exercise regularly, have never had heart problems,  and have a pulse between 60 and 90, the value of the routine annual ECG is very questionable. In fact, the United States Preventive Services Task Force (USPFTF)

“recommends against screening with resting or exercise electrocardiography (ECG) for the prediction of coronary heart disease (CHD) events in asymptomatic adults at low risk for CHD events”

(for asymptomatic adults at intermediate or high risk for CHD they deem the evidence insufficient). The USPSTF feels that that the evidence only supports an annual BP screen along with measurement of weight and a PAP smear.

To many, this seems counter-intuitive: how can a totally benign test that has the potential to detect early heart disease or abnormal rhythms not be beneficial?

There is a growing movement calling for restraint and careful analysis of the value of all testing that is done in medicine. Screening tests, in particular are coming under scrutiny.
Even the annual mammogram, considered by most to be an essential tool in the fight against breast cancer, is now being questioned.

My former cardiology partner, Dr. John Mandrola, who writes the excellent blog at http://www.drjohnm.org, has started an excellent discussion of a recent paper that shows no reduction of mortality with the annual mammogram. He looks at the topic in the context of patient/doctor perception that “doing something” is always better than doing nothing, and the problem of “over-testing.”

In my field of cardiology there is much testing done. It ranges from the (seemingly) benign and (relatively) inexpensive electrocardiogram to the invasive and potentially deadly cardiac catheterization. For the most part, if patients don’t have to pay too much, they won’t question the indication for the tests we cardiologists order. After all, they want to do as much as possible to prevent themselves  from dropping dead from a heart attack and they reason that the more testing that is done, the better, in that regard.

The Problem of False Positives and False Negatives

But all testing has the potential for negative consequences because of the problem of false positives and negatives. To give just one example: ECGs in people with totally normal hearts are regularly interpreted as showing a prior heart attack. This is a false positive. The test is positive (abnormal) but the person does not have the disease. At this point, more testing is likely to be ordered; specifically, a stress test. Stress tests in low risk, asymptomatic individuals often result in false positive results. After a false positive stress test, it is highly likely that a catheterization will be ordered. This test carries potential risks of kidney failure, heart attack, stroke and death. It is bad enough that the cascade of testing initiated by an abnormal, false positive,  screening test results in unnecessary radiation, expense and bother but  in some cases it end up killing patients rather than saving lives.

On the other end of the spectrum is the false negative ECG. Most of my patients believe that if their ECG is normal then their heart is OK. Unfortunately the ECG is very insensitive to cardiac problems that are not related to the rhythm of the heart or an acute heart attack.

Patients who have 90% blockage of all 3 of their major coronary arteries and are at high risk for heart attack often have a totally normal ECG. This is a false negative. The patient has the disease (coronary artery disease), but the test is normal. In this situation the patient may be falsely reassured that everything is fine with their heart. The next day when they start experiencing chest pain from an acute heart attack, they may dismiss it as heart burn instead of going to the ER.

More and more, screening tests like the ECG and the mammogram  are rightfully being questioned by patients and payers. For a more extensive discussion about which tests in medicine are appropriate check out the American Board of Internal Medicine’s http://www.choosingwisely.org.

Keep in mind: not uncommonly,  doing more testing can result in worse outcomes than doing less.