Intracoronary Pressure Gradient Measurement in Acute Myocardial Infarction Patients With the No-Reflow Phenomenon During Primary Percutaneous Coronary Intervention

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Intracoronary Pressure Gradient Measurement in Acute Myocardial Infarction Patients With the No-Reflow Phenomenon During Primary Percutaneous Coronary Intervention

Every year, millions of people survive a heart attack thanks to life-saving procedures like primary percutaneous coronary intervention (pPCI)—a treatment that opens blocked coronary arteries and restores blood flow to the heart. But for some patients, even after the main artery is unblocked, blood fails to reach the heart muscle. This dangerous condition, called the no-reflow phenomenon, can lead to more heart damage, worse recovery, and higher risk of death. Now, a study from Tianjin Chest Hospital in China sheds light on why no-reflow happens and how to fix it—by looking at blood pressure changes in the coronary arteries.

What Is the No-Reflow Phenomenon?

No-reflow occurs when the heart muscle doesn’t get blood flow even after the main blocked artery (infarct-related artery, IRA) is opened. It’s caused by tiny clots (microembolisms), swollen blood vessels (edema), overactive immune cells, or tightened small blood vessels (microvasculature). For patients, this means the heart can’t heal properly—even after a successful pPCI.

How the Study Worked

Researchers led by Dr. Yin Liu from the Department of Coronary Care Unit at Tianjin Chest Hospital wanted to answer a simple question: Does abnormal blood pressure in the coronary arteries cause no-reflow?

They hypothesized that in no-reflow arteries, the pressure in the far (distal) part of the artery might be higher than the near (proximal) part—opposite to normal blood flow, which moves from high to low pressure. To test this, they studied 59 patients who underwent pPCI between September 2018 and June 2019:

  • 33 patients with no-reflow (TIMI flow grade 0–1, meaning little to no blood flow after stenting).
  • 26 control patients with normal blood flow (TIMI grade 3).

Using an aspiration catheter (a thin tube used to remove blood clots), the team measured blood pressure continuously from the distal to proximal segments of the coronary artery. They recorded at least 12 cardiac cycles (heartbeats) for each patient and calculated the forward pressure gradient—the difference between proximal (near) and distal (far) pressure. A positive gradient means blood flows normally (high to low pressure); a negative gradient means flow is reversed (low to high pressure).

All patients gave informed consent, and the study was approved by the Tianjin Chest Hospital Ethics Committee.

Key Findings: Abnormal Pressure Gradients Drive No-Reflow

The results were clear:

  1. No-reflow patients had negative pressure gradients—meaning distal pressure was higher than proximal.

    • Systolic (heart contraction) gradient: -1.3 mmHg (vs. +3.8 mmHg in control patients).
    • Diastolic (heart relaxation) gradient: -1.0 mmHg (vs. +4.6 mmHg in control patients).
      These differences were highly statistically significant (P < 0.001), confirming the team’s hypothesis.

  2. Distal nicorandil fixed the gradient—When the researchers gave nicorandil (a vasodilator that relaxes blood vessels) directly into the distal artery via the aspiration catheter, the pressure gradients flipped to positive:

    • Systolic gradient: +3.0 mmHg (from -1.3 mmHg).
    • Diastolic gradient: +4.2 mmHg (from -1.0 mmHg).
      This meant blood flow returned to normal—with pressure higher in the proximal segment (near the heart) than the distal segment (farther out).

Why This Matters for Treatment

The study’s biggest takeaway is simple: No-reflow is linked to abnormal pressure gradients in the coronary arteries.

Ordinarily, vasodilators like nicorandil are given through a guiding catheter (which sits in the main artery) or an IV. But this study shows that delivering the drug directly to the distal artery—using the same aspiration catheter used to measure pressure—works better. Why? Because it targets the tiny blood vessels (microcirculation) where no-reflow starts.

As Dr. Liu’s team explains: “If you give vasodilators through a guiding catheter, most of the drug might not reach the distal vessels. But using the aspiration catheter to deliver nicorandil right where it’s needed relaxes the microvasculature, lowers distal pressure, and restores the normal pressure gradient.”

Limitations and Next Steps

The study is a promising first step, but it has limitations:

  • Small sample size: Only 59 patients were included.
  • Single-center: Results need to be confirmed in larger, multi-center studies.
  • No repeat measurements: The team couldn’t measure pressure at multiple points in the artery, which might provide more detail.

Still, the findings offer a new way to treat no-reflow—one that’s simpler than fancy devices and uses existing tools (aspiration catheters) already used in pPCI.

Conclusion

For patients with acute myocardial infarction (heart attack), no-reflow is a life-threatening complication. This study from Tianjin Chest Hospital shows that abnormal pressure gradients in the coronary arteries are a key driver of the condition—and that distal nicorandil delivery via an aspiration catheter can fix those gradients and restore blood flow.

For doctors, this means a new tool in the fight against no-reflow. For patients, it means a better chance of full recovery after a heart attack.

This study was published in the Chinese Medical Journal in 2020 by Ming-Dong Gao, En-Yuan Zhang, Yuan-Ying Liu, Xiao-Wei Li, Jian-Yong Xiao, Gen-Yi Sun, and Yin Liu. The full study is available at doi.org/10.1097/CM9.0000000000000709

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