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Dr. Jeff Hersh

Dr. Jeff Hersh: Heart test causes undue alarm

Q: I am only 37, I don’t smoke, I have never had any medical problems and I am very active, but I was at this health fair where they had a free cardiovascular screening, so I did it. My blood pressure was perfect at 116/72, my total cholesterol was on the low-normal side, my good cholesterol was high-normal and my blood sugar was normal; however, my electrocardiogram showed high voltage. They told me to see my doctor, and now I am nervous. What might this mean?

A: Since there may be other confounding factors you have not mentioned, you should see your doctor for consultation. With that said, the cardiovascular calculator at http://cvdrisk.nhlbi.nih.gov/calculator.asp would put your 10-year risk of a heart attack at a very low level.

The recommendation from the U.S. Preventive Services Task Force for asymptomatic adults at low risk for heart disease is that an electrocardiogram should not be done. This is because the potential benefit for these people of identifying a treatable condition and improving their health was determined to be lower than the potential risk of a false positive result.

Consultation with your doctor will hopefully confirm that you are one of those people who have a false positive result and there is nothing you should be worried about.

With this introduction, today’s column will focus on left ventricular hypertrophy, since that is one of the things that can cause high voltage on an ECG. The left ventricle is the most powerful chamber of the heart, responsible for pumping oxygenated blood all over the body. The left ventricle may be “over-exercised” from:

A volume overload condition where the heart is forced to pump excessive amounts of blood, for example because of a leaky aortic or mitral valve causing it to pump enough blood not only to fulfill the body’s needs but also to account for the extra amount of blood that “leaks” back into the left ventricle.

A pressure overload condition where the left ventricle is forced to pump much more forcefully, for example because of a stenotic aortic valve (squeezing the outlet from the left ventricle like putting your thumb over the end of a garden hose) or most commonly from high blood pressure.

This “over-exercise” causes the left ventricle to become “muscle bound,” increasing the thickness of the left ventricle, the size of the left ventricle chamber or both; this is left ventricular hypertrophy.

Just as it takes a while to develop large muscles by working out at the gym, left ventricular hypertrophy develops over weeks, months and years. Left ventricular hypertrophy is of concern because of the complications that may be associated with it, such as sudden cardiac death, heart attacks, abnormal heart rhythms such as atrial fibrillation, heart failure and ischemic heart disease.

The definitive diagnosis of left ventricular hypertrophy is made by imaging the heart (and hence the hypertrophied left ventricle) with an echocardiogram (an ultrasound of the heart). However, when there is hypertrophied heart muscle in the left ventricle the heart’s electrical signals (which are conducted by all heart cells in order to synchronize the heartbeats) are affected, so the EKG (which measures the electrical signals of the heart) may show certain changes.

The extra heart muscle in left ventricular hypertrophy patients often equates to stronger overall electrical activity; this may be noted on the ECG as high voltage (large QRS signals).

However, there are many other causes of this on an ECG, and even the definition of what is “high” voltage is somewhat controversial. Because of this, large QRS signals on an ECG by themselves do not correlate well with actual left ventricular hypertrophy. Instead, scoring systems which weigh high voltage as well as other features of the ECG (such as strain pattern, left axis deviation, left atrial enlargement, ST/T wave changes and other ECG changes) have been developed.

If the underlying cause of the left ventricular hypertrophy is treated, the condition may improve and even resolve. Therefore, surgery to treat heart valve problems, medication to control high blood pressure or other interventions, if they correct the underlying cause of the left ventricular hypertrophy, may effectively treat left ventricular hypertrophy and by doing so lower the risk of complications associated with it.

There are two different take-home messages: Medical tests should only be done when they are indicated; otherwise the results from them may not be interpretable or may even cause harm (such as from an unnecessary cascade of further tests). And people with left ventricular hypertrophy should be evaluated for the underlying cause, and this should be treated to minimize any additional risks from left ventricular hypertrophy.

Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com.

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