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Question:
Based on the results of my echo and nuclear stress test, do I have a problem?
I am 63 years old. I did an echo and nuclear stress test. The echo turned out normal but the stress test chart observed abnormality. I did a 64 slice CT instead of a cath and found out no significant blockage. The CT scan indicated my calcium score is 24 and it is below 25th percentile for men at my age. Does that mean I am better than 25% of men at my age??? And my ejection fraction is 71% (norm is 55-70) with a cardiac output of 4.8 L/min (norm 5-6 L/min). My heart beat during the scan was 52 (norm 60-80). It seems to me all the above results are outside the normal range. Does that indicate any problem ?? Or it means that my heart is better than the normal people?
submitted by Michael from Pasadena, on 9/10/09
Answer:
by Texas Heart Institute cardiologist, Christopher M. Frank, MD
CT scans of the heart provide three basic types of information. First is the calcium score, which is an overall measurement of the amount of calcification in the wall of the coronary arteries (a process that happens with atherosclerosis as well as other heart diseases). In general terms, a calcium score of zero indicates an extremely low risk of significant atherosclerosis (blockages of the arteries of the heart), and the higher the number the "worse." Most physicians consider a score over 100 to represent established coronary artery disease and justify medical treatment with aspirin and cholesterol medications; some would argue that a patient with a score over 400 should undergo a stress test to make sure that the coronary disease has not produced significant blockages, even in the absence of symptoms. (The range from 10-100 is something of a grey zone.) The number can also be reported as a percentile; for example, a score that places a patient in the 25th percentile means that 25% of age and sex matched patients have less disease and 75% have more disease, which can be helpful in understanding whether a given amount of disease is "normal for age" or not.
Second, a CT scan with intravenous contrast dye and 3D reconstruction ("CT coronary angiography") is a reliable way of seeing three dimensional pictures of the coronary arteries without having to perform an invasive test. It's extremely good at ruling out significant coronary artery blockages in the proximal coronary arteries and evaluating congenital abnormalities of the coronaries; it can also see blockages but has acquired something of a reputation for overstating the severity of blockages.
Third, some CT labs report the ejection fraction, which is the amount of blood ejected on each beat and is the most common measure of heart function. Ejection fraction can be measured via CT, MRI, echocardiography, nuclear studies, or invasive ventriculography, and all of those ways of measuring it have their own advantages and disadvantages. It can change slightly between measurement techniques, from day to day, and even from beat to beat, so it is often reported as a range (i.e., "55-60%") that indicates that we shouldn't take tiny changes in the computer-generated numbers to mean any significant change in heart function. Ejection fractions under 50% are clearly abnormal and should be investigated; ejection fractions over the normal range of 70% don't have any specific meaning and in some cases simply reflect artifacts of the measurement technique, and measurements of cardiac output are really just estimates.
Finally, about heart rate, which was reported as 52. The reason this is important is that CT scans require a slow heart rate for accuracy, and patients are often given medicines to accomplish that. Even if that wasn't done in this particular case, the "normal" range of heart rate is somewhat wider than the commonly reported 60-100 beats per minute, and in the absence of symptoms a heart rate that's a few beats per minute lower than that should not be a cause for concern.
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Updated September 2009
