A stent is a small, expandable mesh tube permanently placed inside a narrowed or blocked artery. It acts as a scaffold, holding the vessel open to ensure sufficient blood flow to the heart muscle, a procedure often used to treat coronary artery disease. The decision to implant this medical device is a multi-step process, beginning with recognizing physical indicators and concluding with a medical evaluation that confirms the location and severity of the blockage.
Early Warning Signs of Coronary Artery Narrowing
The first indication that a stent might be necessary often comes in the form of physical sensations signaling that the heart is not receiving adequate oxygenated blood, a condition known as ischemia. The most recognized symptom is angina, which manifests as chest discomfort, pressure, or a feeling of squeezing, typically in the center or left side of the chest. This sensation is usually brought on by physical exertion or emotional stress when the heart’s demand for blood exceeds what the narrowed coronary arteries can supply.
Chest discomfort is differentiated as either stable or unstable angina. Stable angina is predictable, occurring only during activity and resolving quickly with rest or medication. Unstable angina is a medical concern because it is unexpected, occurring even at rest, or it may be a sudden worsening of a previously stable pattern, suggesting an acute change in the blockage.
Insufficient blood flow can trigger other, less specific symptoms, particularly in women or older adults. These atypical signs include sudden, unexplained shortness of breath, profound fatigue, or discomfort that radiates to the neck, jaw, arm, or upper back. Digestive-like feelings such as nausea or indigestion, along with unexplained sweating or lightheadedness, should prompt a medical consultation.
Tests Used to Locate and Measure Blockages
Once symptoms suggest coronary artery narrowing, physicians use diagnostic tests to precisely locate and quantify the extent of the disease. Initial assessments often begin with a resting Electrocardiogram (ECG), which records the heart’s electrical activity and can reveal patterns of reduced blood flow. Because blockages may only affect the heart during periods of stress, the next step is often a stress test.
A standard exercise stress test requires the patient to walk on a treadmill while monitoring the ECG, heart rate, and blood pressure to observe the heart’s response to increased demand. For individuals unable to exercise, a pharmacologic stress test uses medication to simulate exertion. Imaging, such as an echocardiogram or nuclear imaging, is then used to detect muscle areas not receiving enough blood supply. These non-invasive tests indicate the likelihood of a significant blockage but cannot definitively pinpoint its exact location or severity.
The definitive step in determining the need for a stent is a coronary angiography, often referred to as a cardiac catheterization. This invasive procedure involves inserting a catheter into an artery, usually in the wrist or groin, and guiding it to the coronary arteries. A contrast dye is injected, allowing the arteries to be visualized in real-time under X-ray, which provides an exact roadmap of the blockages and reveals the degree of narrowing. During this procedure, Fractional Flow Reserve (FFR) may be measured using a specialized wire to assess the blood pressure difference across the blockage. This physiological measurement determines the functional significance of a blockage, showing whether it restricts blood flow enough to cause ischemia.
Medical Factors Determining the Need for a Stent
The decision to place a stent is based on evaluating the anatomical blockage, its functional impact, and the patient’s overall clinical presentation. Anatomically, the general threshold for stenting to relieve symptoms is a blockage causing 70% or more narrowing in a major coronary artery. If the blockage is in the Left Main Coronary Artery, which supplies blood to a large portion of the heart muscle, the threshold for intervention is lower, typically 50% or more narrowing.
Stenoses that appear moderate (between 50% and 70%) are often assessed using the FFR measurement. If the FFR value is 0.80 or less, the blockage is functionally significant, meaning it causes a measurable reduction in blood flow, and stenting is often warranted to improve symptoms. This physiological assessment ensures that only blockages truly restricting blood flow are treated with a stent, rather than relying solely on a visual estimate from the angiogram.
The location and number of diseased vessels influence the choice between stenting, medical management, or Coronary Artery Bypass Grafting (CABG). For complex disease involving multiple vessels or blockages in high-risk locations like the left main artery, CABG may be the preferred method for improving long-term survival. Stenting is generally recommended for patients with single or double-vessel disease and for those presenting with an acute heart attack, where immediate restoration of blood flow is paramount. The final decision hinges on whether the blockage is causing unacceptable symptoms despite medication or represents an acute threat to the heart muscle.