If you’re like me, the last thing you want to hear is that you have to delay, or worse – skip – your morning cup(s) of coffee.
This is, unfortunately, a fairly frequent necessity in medicine. Whether you’re about to get blood work drawn, have a coronary artery calcium score CT scan, or undergo surgery, you likely have to fast or avoid caffeine prior to your procedure.
While you don’t have to fast before a coronary calcium scan, you do have to avoid caffeine since caffeine consumption can negatively impact the quality of your coronary calcium scan.
Why? Because caffeine is a stimulant that can increase your heart rate (how fast your heart beats) and a CT scanner is essentially a camera taking pictures of the heart.
If your heart beats too fast, the CT scanner won’t be able to take quality pictures to see (and count) the calcium deposits on the coronary arteries. This frequently results in motion artifacts (such as blurring or doubling in the image), which can lead to a nondiagnostic exam or an inaccurate score with over- or underestimation of the true amount of coronary artery calcification.
An inaccurate calcium score can erroneously place a person into the wrong risk category and give a false risk assessment for coronary heart disease.
For more background information and a deeper dive into a coronary calcium scan, coronary artery disease, and the meaning of a coronary calcium score, keep reading 🙂
What are the Coronary Arteries?
Coronary arteries are the blood vessels that supply nutrient and oxygen-filled blood to the heart.
The heart is a large muscle that pumps blood throughout the body. Arteries deliver blood from the heart to our organs and veins bring blood back to the heart. Our arteries are essentially long tubes or pipes lined with smooth muscle cells that help “push” blood into our organs, allowing our organs to extract nutrients and oxygen from the blood.
What is Coronary Artery Calcium?
Coronary artery calcium consists of calcium deposits within the wall of the coronary arteries, typically within fat and cholesterol that builds up within the walls (known as atherosclerotic plaque). Atherosclerotic plaque with calcium deposits can occur in essentially any artery.
When coronary artery calcium builds up, it can have a negative effect on a coronary artery’s ability to send blood to the heart.
For more on the importance and impact of coronary artery calcium, we need to talk about coronary artery disease.
What is Coronary Artery Disease?
Coronary artery disease occurs when atherosclerotic plaque builds up in the coronary arteries. This atherosclerotic plaque can be “soft” plaque, which is noncalcified, or “hard” plaque, which is calcified.
I like to think of arteries as elastic or expandable pipes that deliver nutrient-rich blood to your organs. When your organs need more blood (e.g., muscles during exercise, digestive organs following a meal), your arteries can expand (dilate) to allow more blood to travel to whatever organ is in need of extra blood.
For another analogy, you can think of the body like a car. When you want to accelerate, you need more energy. To accomplish this, the carburetor delivers more fuel to the engine, allowing the engine to extract more energy so the car can move faster. Similarly, when the body needs more fuel (blood), the heart can pump more quickly and the arteries can expand to increase blood flow.
As a coronary artery becomes diseased (with build-up of significant atherosclerosis) and calcifies, the artery gradually loses its ability to expand and loses its elasticity. It turns from an elastic pipe into a lead pipe. The calcium deposits cause the arteries to harden and become rigid. To make things worse, the pipes (arteries) can narrow on the inside, decreasing the amount of blood that can flow through them.
Sometimes, the pipes can even become completely blocked and completely restrict blood flow to the heart, which, as one would expect, is very bad and typically leads to a heart attack. The heart muscle no longer receives blood and the muscle cells starve from lack of nutrients. Without rapid intervention with placement of coronary artery stents or bypass surgery, the heart muscle cells can die.
What Can You Do to Protect Yourself?
For starters, you can figure out if you’re at increased risk of heart disease, particularly coronary artery disease.
While it’s good to practice healthy living at baseline, knowing if you’re at increased risk for heart disease, particularly coronary artery disease, and taking action to minimize your risk of experiencing a heart attack in the future is essential.
Since approximately half of heart disease-related deaths occur in people without prior symptoms or a known history of heart disease (such as coronary artery disease), it’s crucial to detect this silent killer while protective measures can still be taken.
The first step is to learn what cardiovascular risk factors are and if you have any risk factors that would predispose you to heart disease and risk of future heart attack. Gaining awareness of your potential cardiovascular risk factors empowers you to take heart-protective actions, such as lifestyle modification (diet, exercise, etc.) and start heart-protective medications when appropriate.
Cardiovascular Risk Factors
It’s hard to know if you’re at risk without knowing what the risk factors are. Below is a list of some traditional risk factors responsible for increasing a person’s risk of developing heart disease. If you have any of these risk factors, inform your primary care provider (PCP) and work together to determine what you can do to maximize your heart health.
- Age (risk increases with age, particularly >40)
- Gender (male gender)
- Blood Pressure
- Smoking Status
- History of Diabetes
- Body Mass Index (BMI)
- Family History
If you are over 40, asymptomatic (without symptoms), and at borderline to intermediate risk of heart disease, you can consider undergoing a coronary calcium scan to add another data point in your risk assessment to help classify your cardiac risk.
Despite the proven benefit of a coronary calcium scan and the inclusion of a coronary calcium scan in multiple medical guidelines, most insurance payors have yet to start covering this useful examination.
What is a Calcium Score?
Coronary calcium scoring consists of a standardized system that determines the amount of calcium on a person’s coronaries. Calcium deposits are identified by obtaining an ECG-gated CT scan (a CT scan that takes pictures during a specific portion of your heartbeat) to minimize artifacts, such as blurring, related to heart motion and detect calcium deposits. Applying a density threshold makes the calcium deposits stand out for scoring.
A radiologist or trained CT technologist reviews the images and personally selects all areas of coronary calcium using special software, assigning each calcium deposit to a specific coronary artery (left main, left anterior descending, left circumflex, right main, and sometimes posterior descending).
When a CT technologist performs the calcium scoring, the scoring accuracy is reviewed by a radiologist who interprets the examination.
All of the scored calcium deposits are aggregated into one overall score, referred to as an Agatston score (named after the physician who pioneered this method). Each person’s score is compared to a standardized database based on age, gender, and ethnicity (several exist, such as the MESA and Hoff databases) and a percentile is given to the person’s calcium score relative to other people with similar background demographics.
Why Does Calcium Score Accuracy Matter?
Coronary artery calcium score accuracy is important. The calcium score is used to help gauge a person’s future risk of major cardiac events related to coronary heart disease. An accurate calcium score will place a person into the appropriate risk category, which is used to help decide if someone would benefit from taking medication (a cholesterol-lowering statin).
Importance of Avoiding Caffeine Prior to a Calcium Score CT Scan
Since coronary calcium score accuracy matters, radiology imaging centers create protocols to maximize the chance of having a high-quality CT scan.
There are two primary ways imaging centers achieve this: (1) through ECG-gating and (2) by taking efforts to optimize heart rate at the time of scan.
ECG-gating limits heart-related motion artifacts by taking heart motion into account during a heartbeat and only scanning during a specific portion of each heartbeat. However, even with ECG-gating, a rapid heartbeat can result in too much motion, usually when the heart rate is over 80 beats per minute on a typical CT scanner.
Prepping for a heart rate less than 80 is therefore crucial for obtaining a high-quality exam and efforts are taken to optimize the heart rate before a scan. There are several ways to accomplish this, such as avoiding stimulants such as caffeine (discussed below) and occasionally having a patient take a beta-blocker (a medication that slows the heart rate) prior to the examination.
Caffeine is the most commonly encountered stimulant and is widely consumed in the form of coffee and, to a lesser degree, energy drinks. Since stimulants can increase heart rate, cardiac calcium score protocols recommend avoiding caffeine on the day of the examination.
Coffee consumption on the day of the examination, whether moderate coffee consumption or even just a few sips, should be avoided since coffee drinking influences heart rate. Frequent coffee drinkers may need to remind themselves to avoid coffee consumption before their scan. Decaffeinated coffee consumption will not affect the heart rate and can be consumed prior to the cardiac calcium scan.
Some newer CT scanners, particularly those with a larger number of detectors (e.g., a 128-slice scanner), may be able to scan fast enough to accommodate higher heart rates without compromising image quality. These newer scanners are like fancy cameras with a “sports mode” setting, capable of rapidly taking pictures without motion blur. However, these scanners are expensive and may not be widely available, particularly in smaller communities.
Benefits of Coffee Consumption
Outside of getting a cardiac calcium scan, caffeinated coffee has been shown to have numerous health benefits, ranging from decreased risk of developing multiple cancers to reduced risk of developing heart disease. For example, habitual coffee consumption (typically 3-4 cups/day) has been shown to decrease the odds of developing coronary artery calcification among nonsmokers.
So, while you shouldn’t drink coffee prior to your cardiac calcium scan, habitual coffee drinking has many health benefits (and I personally have become a habitual coffee drinker specifically for these health benefits). End of coffee plug :).
How is a Cardiac Calcium Score Used?
Guidelines and coronary calcium scan interpretation vary slightly based on the issuing institution but are overall reasonably similar.
A cardiac calcium score is helpful in two main ways: (1) the overall calcium score number (including the patient-specific percentile) and (2) the number of arteries containing coronary artery calcium.
The overall calcium score is used to risk-stratify people by placing each person into a specific category based on their calcium score (categories listed below). The calcium score is primarily used to reclassify a person’s cardiac risk and help decide if a patient would benefit from a class of cholesterol-lowering medications known as statins.
The number of diseased vessels can also be helpful as the overall risk can be slightly higher when multiple arteries are involved. Scores greater than 1,000 and calcium deposits on the left main coronary artery also provide additional insight into a person’s overall risk.
Calcium Score Categories
Coronary calcium score risk assessment separates people into 4-5 different categories (some include a “1-10” category, included below for completeness).
0 (No Calcium): Very low risk of coronary artery disease or future coronary events (i.e., heart attack)
1-10: Minimal coronary artery calcium; low risk of future coronary events with low probability of myocardial ischemia*
11-100: Mild coronary artery calcium; low risk of future coronary events with low probability of myocardial ischemia*
101-400: Moderate coronary artery calcium; increased risk of future coronary events; consider reclassifying the individual as being at high risk
>400: Severe coronary artery calcium; increased probability of myocardial ischemia*
*Note: Myocardial ischemia is medical jargon for when heart muscle cells don’t receive enough blood to carry out their normal function.
As with all imaging, incidental findings are commonly made, such as incidental lung nodules, enlargement of the aorta or pulmonary arteries, enlarged lymph nodes, cancers, adrenal nodules, fatty infiltration of the liver, etc. Some of these incidental findings may require clinical correlation and/or further medical workup.
Coronary artery calcium can also be detected on a non-coronary calcium scan, such as a routine chest CT scan. Radiologists may take an all or none approach (i.e., coronary calcium present vs. not present) or give a subjective grade (mild, moderate, extensive).
Cardiovascular disease is one of the most common silent killers, but, fortunately, we can identify risk factors to assess a person’s heart disease risk.
Adults over 40 at borderline to intermediate risk of coronary artery disease can undergo a cardiac calcium scoring CT scan to detect coronary artery calcium, which can help classify their cardiovascular disease risk. Moreover, their calcium score can help determine if they would benefit from taking a cholesterol-lowering statin or persuade them to consider lifestyle modification to reduce their cardiac risk.
If you decide to undergo screening with a coronary calcium scan, it is important to avoid coffee consumption to improve your chances of getting a high-quality scan with an accurate calcium score. An accurate calcium score will help put you in the correct risk category and get you started on the steps necessary to help prevent a future heart attack.
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