There’s no organ as incredible as the human heart. It pulses at roughly 80 beats per minute. And if you do the math, most people will experience under four billion total heartbeats over their lifespan. As the engine powers blood circulation, the heart enables life itself. So when something goes wrong with this vital muscle, medical imaging is of the essence for proper diagnosis and treatment.
Thankfully, cardiac imaging provides doctors with non-invasive ways to see inside the beating heart and flowing blood vessels to assess overall cardiovascular health. There are several techniques available, from cutting-edge MRI scans to routine echocardiograms. Each technique has its own strengths to benefit patients depending on the clinical need. Understanding how these cardiac tests work empowers patients to better partner in their own heart care.
Here’s each of them explained:
Cardiac MRI scans
An MRI scan takes detailed pictures inside your body without radiation, surgery, or pain. It uses magnets and radio waves to see your organs clearly. Plus, MRI scans can focus on different body parts, making them extremely useful for many health issues. But it especially excels at imaging the heart. Special MRI methods can even show heart structure, function, tissue health, blood flow, and more.
So, what makes this type of cardiac imaging excellent? It gives crisp, clear images of your beating heart without any shots or procedures needed. Also, the image quality isn’t as limited by body size or other factors as ultrasound tests. This scan tracks tiny heart motions precisely, measuring pumping in each area and calculating volumes accurately.
Advanced MRI techniques can also check heart muscle health after silent events like small heart attacks. They pinpoint areas with reduced blood supply. Knowing if heart tissue is stunned but can recover versus permanently damaged greatly impacts treatment options.
Besides examining anatomy, cardiac MRI also evaluates blood flow dynamics. It detects turbulent jets from narrowed valves and maps out regions getting low flow.
How does MRI create moving pictures inside your pulsating heart without surgery? It uses hydrogen atoms found abundantly in water and fat to form images. You’ll lie comfortably on a table inside a large magnet that organizes the atoms. Brief radio pulses then disturb the atoms, making them emit faint rotating signals the scanner detects.
Additional features ensure unique signals from each body area that the MRI machine identifies by location and tissue type. These signals get processed into diagnostic pictures.
To further enhance images, you may receive an injected contrast solution to highlight blood vessels.
Capturing moving heart structures requires fast, precisely timed MRI sequences synchronized to your heartbeat. You may also briefly hold your breath during certain sequences. This momentary pause helps sharpen the images by reducing motion artifacts.
CT coronary angiography
A CT scan uses rotating X-ray beams to quickly obtain multiple image slices through your body. Advanced computers turn these images into cross-sectional pictures inside you.
CT is great at showing dense structures like bones and blood vessels clearly as they block more X-rays than soft tissues. An injected contrast dye makes vessels stand out even more. And as this dye flows through your arteries, they light up compared to surrounding tissues. CT combines direct cross-sectional views, tissue differentiation, and contrast enhancement to give excellent 3D pictures.
Faster multi-detector CT scanners allowed the development of CT coronary angiography (CTCA). This non-invasively evaluates coronary arteries without inserting a catheter like traditional angiography. Avoiding catheterization removes procedural artery injury risks and lowers cost and recovery time.
CTCA offers an attractive option for evaluating low-risk chest pain in emergency rooms. It also suits screening selected patients for early coronary disease before symptoms using risk factors.
So how does CTCA work? You’ll get medications to slow your heartbeat below 65 beats per minute for best images. Pills or IV drips help reach these target rates. You’ll lie on a moving scanner table advancing through the CT ring around your chest. Contrast dye is then injected through the IV, precisely timed with scanning to light up the coronary arteries.
During the scan, advanced software makes a 3D model from the many 2D slices. Radiologists can then scrutinize the CTCA images slice-by-slice and manipulate a 3D rendering of the full coronary tree, looking for abnormal narrowing of the heart.
Unlike MRI, CT does involve low X-ray radiation with current scanners. So, risks like dye reactions and kidney issues warrant weighing CTCA benefits for each patient. Another limitation is lower accuracy seeing tiny distal vessels and branches versus traditional angiography.
Irregular heart rhythms or difficulty sustaining a slower heartbeat also reduce CTCA imaging quality. In a study of two groups with different heart rates during CTCA imaging, it was observed that 76% of cases from the first group, which consisted of people with normal heart rates, delivered good to excellent image quality. Meanwhile, the second group, consisting of people with higher heart rates, only had 49% of valuable images.
Nevertheless, continuing technology progress expands CTCA applications for non-invasive coronary assessment.
Echocardiography
An echocardiogram uses ultrasound waves like those that create baby pictures during pregnancy. High-frequency sound waves aimed at your chest get reflected back by heart parts and blood cells differently. High-technology computers turn the signals into moving heart images. This versatile, low-cost test has become the most used imaging for managing heart patients.
The ultrasound shows heart anatomy and pumping ability without surgery or injections. It easily tells thin chamber walls from thick muscle walls. Watching valve and tendon motion inside the left pump chamber displays the intricate coordination needed.
Moreover, this painless test can quantify blood filling your heart’s pump chambers with each beat. It tracks changes over time in heart failure patients to optimize medications for ideal fluid levels.
The ultrasound peeks at the beating heart through spaces between ribs, like looking through windows from different viewpoints. Getting pictures from various angles finds subtle wall thickening or motion delays—clues to past silent heart attack damage.
Colorful maps also display the speed and direction of blood flow through narrowed or leaky valves, estimating pressure differences causing turbulence.
A major plus is real-time imaging, capturing quick motions impossible to see otherwise. Velocity waveforms display the spectrum of blood speeds at structures. Classic black-and-white images provide more valuable dynamic details than stethoscope assessments ever could.
However, no test is perfect. Like pregnancy ultrasounds, body size impacts image quality. For example, obese patients and those with lungs blocking views may have technically limited studies. Operator skill also strongly affects accuracy.
Standard ultrasound also relies on shape assumptions, and this can lead to erroneous estimation of true pumping volumes and performance. Seeing hidden structures remains challenging despite recent gains. For specific issues like tissue strain, cardiac MRI gives superior numbers versus standard echocardiography. Still, with expanding abilities and advancing technology, echocardiography remains a versatile and trustworthy tool for checking cardiac structure and function.
In a recent study in Japan comparing in-hospital mortality rates related to heart failures prior to and after the integration of echocardiography, patients with echocardiography have a lower in-hospital mortality rate of 6%. This is a major difference from the former 12.2% in-hospital mortality rate prior to echocardiography application. No wonder cardiologists consider echocardiograms essential for managing heart disease!
What happens before, during, and after your heart test?
You’ve got to know how to prepare for your particular heart scan and what happens during and after the actual test so you can set realistic expectations and ease your anxiety beforehand. Here are some pointers you must remember:
Cardiac MRI scan
For such a complex, high-tech scan, the preparation is actually quite straightforward!
When scheduling, ask your doctor how long the full MRI appointment will take. The testing itself normally lasts from 30 to 90 minutes. But you also need to factor in check-in, changing into a hospital gown, set up time in the scanner room, and post-scan monitoring. So you’ll want to count on two to three hours total or even longer for cardiac studies.
It’s important not to bring any metal into the MRI room as the powerful magnets will yank objects right out of your pockets, damage items like jewelry or watches, and even disrupt medical devices like pacemakers. To prevent such situations and any hazardous accidents, the technician will conduct a double safety check before you enter.
But despite this scan being simple, challenges may take place. Claustrophobia, for one. This is a common concern for people undergoing MRI scans. When inside the scanner, your entire body is enclosed in a tight tunnel just inches from your face. This confinement can trigger anxiety over small, dark spaces. Such distress may jeopardize imaging by making it challenging to lie sufficiently still, resulting in blurred scans.
Therefore, if you have even just the slightest unease with enclosed areas, never hesitate discussing sedative medication with your provider to ease any tension. Additional relaxation techniques like listening to music and closing your eyes also prove beneficial. These measures redirect focus away from the tight space and make the procedure more tolerable.
Now, the actual scan itself just involves lying quietly on a narrow sliding table without moving and breathing normally for most sequences. However, for better-quality cardiac imaging, you may be asked to hold your breath briefly for up to 20 seconds multiple times. So, it’s best to practice some long breath holds prior to the actual test to gauge your natural limit.
CT scan
For cardiac CT studies specifically, an important priority is regulating heart rate, ideally below 65 beats per minute. Fast, irregular heartbeats blur the scans. So, your doctor will prescribe a beta blocker medication to take the evening before and in the morning of your test to slow your pace.
Starting a full eight hours beforehand, you also must not eat any solid foods or milk products, only clear liquids like juice, tea, plain gelatin, and broth. Fasting prevents food particles and gases from obscuring imaging. However, stay well-hydrated, drinking extra clear fluids right up until your appointment time.
When you check-in, an IV is inserted, usually in the hand or arm, both to inject the dye and administer additional medication to lower your heart rate if your levels are still too rapid. So, it helps to point out the best sites for you based on prior IV access difficulties.
Once settled on the scanner table, electrodes will be placed on your chest to monitor your heart rhythm. When perfectly still, the actual scan only lasts less than 30 seconds! However, with cardiac timing protocols, imaging repeats over various points in your cycle, meaning you slide in and out of the scanner ring multiple times.
Many people report warmth spreading through their bodies after the contrast bolus, sometimes even a metallic taste in their mouth. This flushed reaction is entirely normal and resolves within minutes after the scan finishes.
Finally, because the iodine dye gets filtered out by your kidneys with preexisting kidney dysfunction, your doctor may request blood work a day or two later to ensure no lasting impact on function.
Echocardiogram
Echocardiograms harness ultrasound technology like the one used to view developing babies in utero. But in this case, sound waves directed at your rib cage bounce signals off your heart structures to create moving images of valves and pumping chambers.
The great news about echo tests is they don’t require advance preparation. You simply arrive at your designated appointment time in comfortable clothing with open buttons or a zippered top, allowing clear access to the chest area.
Technicians need bare skin contact to position the ultrasound transducer that captures the images best. So, females should wear a separate top rather than a dress, avoiding the need to fully disrobe.
Since ultrasound waves pass straight through, there’s no radiation used nor injectable contrast agents involved. Even patients already eating food or those unable to lie flat can still successfully complete echoes. Cases involving significant wounds, bandages, or sensitive skin may necessitate an alternative choice like MRI or CT instead.
During the 30-60 minutes of scanning, you lie semi-reclined on an exam table, either flat or tilted slightly leftwards. Warm ultrasonic gel gets smoothed over your chest as the technician presses and glides the transducer to different locations to optimize cardiac visualization through rib space windows. The odd sweeping pressure can feel mildly uncomfortable but poses no actual harm.
As images form on the display screen, take an active interest in your own heart structures! The technician may even point out moving valves, pumping motions, and blood flow patterns in real time for you to watch.
In closing
Learning about heart imaging options empowers patients like you. MRI, CT, and ultrasound each uniquely spotlight issues to diagnose problems and offer the best care. Discuss everything with your doctor so you can pick the optimal test that fits your medical needs. Isn’t it a great thing that advancing technology continues providing ever better ways to see this small but mighty organ that keeps you ticking?
Hi, I’m the Founder and Developer of Paramedics World, a blog truly devoted to Paramedics. I am a Medical Lab Tech, a Web Developer and Bibliophiliac. My greatest hobby is to teach and motivate other peoples to do whatever they wanna do in life.