Cardiac MRI: What Each Sequence Tells You
- Cardiac MRI isn't one picture — it's a stack of different sequences, each answering one question: how does the heart move, what is the muscle made of, and where is it scarred?
- Cine (bright-blood) imaging is the movie: it shows wall motion, chamber size, and ejection fraction — the "is it pumping?" sequence.
- T2-weighted and edema imaging lights up swollen, inflamed, or acutely injured muscle (water = bright).
- Late gadolinium enhancement (LGE) is the scar map: contrast lingers where muscle has been replaced by fibrosis, and the pattern of brightness tells you the cause.
- The superpower of cardiac MRI is tissue characterization — telling you not just the shape of the heart, but what the muscle is actually made of.
If a coronary CT angiogram is a detailed road map of the heart's plumbing, cardiac MRI is the building inspector who walks inside and taps on the walls. It doesn't just show you the shape of the heart — it tells you whether the muscle is healthy, swollen, scarred, or stuffed with something it shouldn't have. The catch is that no single image does all of this. Cardiac MRI is a playlist, and you have to know what each track is for.
Let me walk you through the greatest hits.
Cine imaging: the heart, the movie
The foundation of every cardiac MRI is cine imaging — a stack of short movies, each a thin slice of the heart looping through one heartbeat. Blood is bright and the muscle is gray, so you watch the chambers fill and squeeze in real time. (Under the hood this is usually a balanced steady-state technique, which is the "bright blood, gorgeous contrast" workhorse — but you don't have to love the acronym to love the pictures.)
This is where we measure the things cardiologists actually quote: chamber volumes, wall thickness, and ejection fraction (the fraction of blood squeezed out per beat). MRI is considered the reference standard for these volumes because it measures the chambers directly instead of guessing from a single ultrasound plane. If you've already met the heart's standard imaging planes, cine just sets them in motion.
T2 and edema imaging: finding the swelling
Here's a rule that runs through almost all of MRI, including the T1 and T2 basics: water is bright on T2. Injured, inflamed, or acutely strained muscle holds onto extra water, so it glows on T2-weighted (and related edema-sensitive) images while normal muscle stays dark.
Think of it like a bruise you can't see from the outside. Acute myocarditis, a fresh infarct, or stress-injured muscle all swell, and that swelling lights up. This is the sequence that tells you something is happening right now, as opposed to old, settled damage.
"Bright on T2" means acute and watery — recent injury, inflammation, edema. It's a timing clue as much as a tissue clue: old scar is dry and won't glow here.
Late gadolinium enhancement: the scar map
If I had to keep only one sequence, it would be this one. After injecting a gadolinium contrast agent, we wait several minutes and then image again. In healthy muscle the contrast has already washed out, so it stays dark. But where muscle has been replaced by scar (fibrosis), the contrast gets stuck in the expanded spaces between cells and washes out slowly — so scar shines bright white against black, healthy heart. That's late gadolinium enhancement (LGE).
The genius part isn't just that it's bright — it's where and in what pattern. The distribution is a fingerprint for the underlying disease, which is exactly why LGE is so central to working up the cardiomyopathies.
| LGE pattern | What it suggests |
|---|---|
| Subendocardial or transmural, in a coronary territory | Prior myocardial infarction (damage starts at the inner wall and works outward) |
| Mid-wall (sparing the inner lining) | A non-ischemic process such as some forms of dilated cardiomyopathy |
| Patchy or epicardial | Inflammatory or infiltrative disease (e.g., myocarditis, sarcoid) |
Infarct scar obeys the coronary arteries and always involves the subendocardium (the inner layer dies first). Scar that ignores those rules and floats in the mid-wall or outer layer is your tip-off to a non-ischemic cause.
Mapping: putting numbers on the muscle
Newer parametric mapping sequences (T1, T2, and a derived value called extracellular volume) go a step further: instead of "this looks brighter than that," they assign each pixel an actual number. That lets us catch diffuse disease that's spread evenly through the muscle — the kind that has no sharp edge to point at, so the old "compare bright to dark" trick fails. Exact normal ranges vary by scanner and technique, so labs interpret them against their own reference values rather than one universal cutoff.
Putting it together
The art of cardiac MRI is reading the sequences as a sentence, not separate words. Cine tells you how the heart moves. T2 tells you what's acutely angry. LGE tells you what's permanently scarred, and where. A fresh infarct, for example, is the trifecta: a wall that isn't contracting on cine, bright edema on T2, and subendocardial scar on LGE.
Cardiac MRI lives and dies by timing — the images are stitched together across many heartbeats using the ECG. An irregular rhythm or a patient who can't hold their breath smears the picture into blur. Always check whether the gating held up before you trust a wall-motion or scar finding.
So when a report rattles off cine, T2, and LGE, don't let the alphabet soup scare you. Each one is just answering a plain-English question — does it pump, is it swollen, is it scarred — and together they tell you what the heart muscle is truly made of. That tissue-level story, not the anatomy, is why we reach for MRI in the first place.