I initially set out to write a straightforward blog post explaining what it means when a doctor says you have a 50% coronary artery blockage. It’s a topic that often confuses patients and clinicians, and I thought a clear explanation would be helpful.
But as I began drafting, I realized that listing percentages and medical jargon felt dry and disconnected. It lacked the human element—the real-life experiences behind those numbers.
So, I decided to take a different approach. Instead of a clinical breakdown, I’m sharing a story. A story that brings those percentages to life, illustrating what they mean in the context of a person’s journey. Through this narrative, I hope to shed light on the complexities of coronary artery narrowing in an informative and relatable way.
The Confusing Comfort of Percentages
She wasn’t expecting the shortness of breath.
It had started two months earlier—subtle at first. She chalked it up to winter, stress, or maybe the extra weight she’d been carrying since her last birthday. But when she found herself winded after two flights of stairs, she did something uncharacteristic.
She made an appointment.
Her name was Sofia Cardona. At fifty-seven, she had weathered life’s storms with a blend of resilience and wit. A former smoker who now practiced yoga sporadically, she ran a modest graphic design business from her home in Valoria. Her kitchen bore the marks of her culinary adventures—a testament to her belief that the right olive oil could elevate any dish.
A few days later, Sofia was lying beneath the quiet whir of a CT scanner, eyes closed, heart tapping a steady rhythm as contrast dye moved through her bloodstream. She was undergoing CT Coronary Angiography (CCTA), a noninvasive test used to visualize the coronary arteries and detect plaque or narrowing.
The results came back quickly.
Her cardiologist, a man named Dr. Alaric Duvall—kind eyes, quiet hands—leaned back in his chair and said, “There’s a 50% narrowing in your left anterior descending artery.”
Sofia blinked. “Fifty percent?”
“It’s moderate,” he said. “Nothing we need to treat with a stent. No need for anything invasive at this point.”
She nodded slowly. She was good at nodding when she didn’t understand. Half blocked. That didn’t sound so bad. Still usable. Like a road with one lane closed.
But later that evening, sitting at her kitchen table, the phrase kept circling in her mind.
Fifty percent of what?
She opened her laptop.
And so it began.
Measuring the Squeeze
By the time Sofia reached page six of her Google search, she realized something unsettling: she didn’t actually understand what 50% stenosis meant.
Every article seemed to say something slightly different. Some mentioned blood flow. Others talked about diameter. A few threw around terms like “non-obstructive” and “intermediate lesion” as if everyone casually used those over breakfast.
She closed her laptop with a sigh and picked up her phone.
“Alexa,” she said. “You’ve got a smart heart. What does 50% blockage mean?”
Her best friend answered on the second ring. “Great. I’m your personal cardiology assistant now”.
They laughed. Sofia quickly explained—the scan, the number, the doctor’s calm tone that somehow left her more confused than reassured.
Alexa was a seasoned cath lab nurse with years of experience assisting in cardiac catheterizations and interpreting angiographic findings.
“Look,” she said, “in the cath lab, we often see varying degrees of narrowing in coronary arteries. A 50% stenosis is generally considered moderate and typically isn’t enough to cause significant problems because it’s not flow-limiting. Blood can usually get through without much issue.”
Sofia paused. “So, it’s not that serious?”
“Not necessarily. It’s important to consider the whole picture. A 70% narrowing might start to impede blood flow, especially during exertion, and a 90% blockage is almost certainly flow-limiting and more concerning. But these numbers are part of a broader context. We also look at the patient’s symptoms, the specific artery involved, and other factors.”
Sofia’s eyebrows rose. “So, the percentage alone doesn’t tell the whole story?”
“Exactly,” Alexa replied. “That’s why cardiologists often use additional tests, like stress tests or fractional flow reserve measurements, to determine if a blockage is actually affecting blood flow. It’s not just about the percentage; it’s about how that narrowing impacts the heart’s function.”
Sofia nodded slowly. “That makes sense. Thanks for breaking it down.”
Where Do These Numbers Even Come From?
The next morning, Sofia emailed the cardiology clinic.
Subject: Follow-up on CT scan
Body: Hi—I’d like a copy of my scan report if possible. Just curious to see the details. Thanks, Sofia Cardona.
She didn’t expect a reply that fast.
By lunchtime, she had it. A neat, three-page PDF. She scrolled past her name, past the legalese and disclaimers, and landed on a phrase that made her squint.
CAD-RADS 3 – Moderate stenosis (50–69%) in proximal LAD.
There it was again. “50 to 69.” Not even a firm number—just a range.
And what was CAD-RADS? It sounded like something NASA would use to describe a satellite malfunction.
Back on Google, she learned it stood for Coronary Artery Disease – Reporting and Data System—a way for radiologists to categorize findings in coronary CT angiography. Like putting arteries into folders: mild, moderate, severe.
CAD-RADS 3 meant her plaque was in the “moderate” zone. It didn’t tell her if it was dangerous. Just that it existed.
And as for that 50% number? That could come from one of two places:
- Sometimes, it was calculated digitally—comparing the narrowest part of the artery to a “normal” section just upstream or downstream.
- But more often—especially in invasive angiography—it was eyeballed. Estimated. Visually guessed by an experienced physician.
Sofia stared at the phrase again. “Estimated visually.”
Her inner designer cringed. She made her living pixel-perfect. Fonts off by 3% made her itch. And now she was learning that something as serious as a coronary narrowing might be called “50-69%” based on someone’s eyeball?
Maybe it was an informed guess. But it still felt… fuzzy.
And yet, that one fuzzy number was now shaping how everyone, including her, thought about her heart.
It’s Not Just the Size—It’s the Location.
| CAD-RADS | Stenosis Severity |
|---|---|
| 0 | No plaque or stenosis |
| 1 | Minimal stenosis (1–24%) |
| 2 | Mild stenosis (25–49%) |
| 3 | Moderate stenosis (50–69%) |
| 4A | Severe stenosis (70–99%) |
| 4B | Left main ≥50% stenosis |
| 5 | Total occlusion (100%) |
V = Vulnerable plaque features (e.g., low attenuation)
S = Presence of coronary stents
G = Coronary artery bypass grafts
N = Non-diagnostic segments
Sofia had a label now—CAD-RADS 3—but the more she read, the more she sensed that “moderate stenosis” wasn’t as simple as it sounded. It depended on where the plaque was, what it was made of, and what it might do next.
It’s Not Just the Percentage – It’s the Location?
Sofia didn’t intend to delve deeper into medical research, but curiosity nudged her forward. Her report mentioned a “50-69% stenosis in the proximal LAD,” and while she now understood that this might not be immediately alarming, the term “proximal LAD” lingered in her mind.
She reached out to Alexa again.
“Hey, Alexa,” Sofia began, “I was reading about the LAD artery. It’s referred to as the ‘widowmaker‘?”
Alexa, drawing from her years as a cath lab nurse, responded, “Yes, the LAD—left anterior descending artery—supplies a significant portion of the heart muscle. A blockage here, especially in the proximal segment, can be particularly concerning.”
Sofia’s heart skipped a beat. “But mine’s only 50% narrowed. That doesn’t sound too bad, right?”
“True,” Alexa reassured her. “A 50% narrowing isn’t typically flow-limiting. However, because it’s in the proximal LAD, we monitor it more closely. The location adds a layer of significance.”
Sofia pondered this. “So, it’s not just about how much the artery is narrowed, but where it’s narrowed?”
“Exactly,” Alexa affirmed. “Think of the coronary arteries like a tree. The left main artery is the trunk, and it branches into the LAD and circumflex arteries, which further branch out. A 60% narrowing in the left main artery is more concerning than a 90% blockage in a small side branch because the left main supplies a larger area of the heart. The area at risk is greater.”
Sofia nodded, absorbing the information. She realized that understanding her condition wasn’t solely about percentages but also about the context—where the blockage was and how it might affect her heart’s function.
The Second Opinion
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