ISR Vs Stent Thrombosis: Know the Differences

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Difference Between ISR vs Stent Thrombosis: Stent Thrombosis and In-Stent Restenosis (ISR) are two major problems associated with coronary artery stenting. ISR causes repeated symptoms like chest pain by gradually narrowing the artery after stenting as a result of cell proliferation inside the arterial wall. On the other hand, Stent Thrombosis is an abrupt and serious occurrence in which a blood clot develops inside the stent, preventing blood flow and perhaps leading to a heart attack or even sudden cardiac death if treatment is delayed. While Stent Thrombosis presents as an immediate emergency and ISR develops gradually, both problems are related to stenting, but they differ in their onset, development, and clinical severity.

Stent Thrombosis 

  • One serious side effect of coronary stenting is thrombosis in the stent.
  • Blood flow is obstructed by the formation of a blood clot inside the stent.
  • May result in an abrupt heart attack or perhaps death.
  • Medication non-compliance and underlying cardiac disease are risk factors. 

In-Stent Restenosis (ISR) 

  • Refers to a coronary artery's re-narrowing following the implantation of a stent.
  • It happens as a result of the arterial wall's cells proliferating and narrowing.
  • Angina or chest pain are recurrent symptoms that might be brought on by ISR.
  • Among the risk factors for ISR are smoking, diabetes, and specific stent types. 

Difference between Stent thrombosis and In Stent Restenosis (ISR)

Stent Thrombosis is the sudden blockage of a coronary stent as a result of the creation of a blood clot, whereas In-Stent Restenosis (ISR) is the progressive narrowing of the stented artery as a result of tissue growth. The table below shows the differences between difference Stent Thrombosis and In-Stent Restenosis (ISR)


Stent Thrombosis

In-Stent Restenosis (ISR)


Formation of blood clot within the stent, blocking blood flow

Re-narrowing of the coronary artery post-stent placement due to cell proliferation





Can occur suddenly, leading to a heart attack or death

Develops over time, with recurrent symptoms

Clinical Presentation

Sudden onset of symptoms such as chest pain or shortness of breath

Recurrent symptoms of angina or chest pain

Risk Factors

Premature discontinuation of antiplatelet medication, stent malapposition, underlying heart disease

Diabetes, smoking, certain stent types


Urgent medical intervention required (e.g., antiplatelet therapy, thrombectomy)

Medication adjustments, balloon angioplasty, additional stenting

Prevention Strategies

Adherence to antiplatelet therapy, proper stent deployment, managing risk factors

Use of drug-eluting stents, lifestyle modifications (e.g., smoking cessation)

What is Stent Thrombosis?

A blood clot (thrombus) within a coronary stent, a tiny metal mesh tube used to treat restricted or obstructed coronary arteries, is the hallmark of the medical illness known as stent thrombosis. This clot blocks the stented artery's blood flow, causing a sharp drop in the amount of blood that reaches the heart muscle. If left untreated, this can cause a heart attack or possibly sudden cardiac death.

Features of Stent Thrombosis

  • Blood Clot Formation: This condition is characterized by the accumulation of blood within the coronary stent, which obstructs blood flow through the artery and may result in myocardial infarction or ischemia.
  • Medical Emergency: Because Stent Thrombosis can result in myocardial infarction (heart attack) or rapid cardiac death if left untreated, it is regarded as a medical emergency.
  • Symptoms: Shortness of breath, perspiration, nausea, palpitations, and intense chest pain (angina), especially at rest or with little effort, are common symptoms.
  • Risk Variables: Premature antiplatelet medication termination or non-compliance, stent malapposition, underlying coronary artery disease, and patient-related variables like smoking, diabetes, and obesity are risk factors for stent thrombosis.

Causes of Stent Thrombosis

  • Stent Malapposition: When a stent is improperly deployed into a coronary artery, it can leave gaps between the stent and the arterial wall, which can allow blood clots to form.
  • Underlying Coronary Artery Disease: Because of the existence of atherosclerotic plaques and aberrant blood flow dynamics inside the arteries, patients with underlying coronary artery disease are more likely to experience stent thrombosis.
  • Smoking: One of the main risk factors for stent thrombosis is smoking. It increases the risk of endothelial dysfunction and inflammation, which makes the stent more vulnerable to clot formation.
  • Diabetes: Diabetes mellitus raises the risk of stent thrombosis due to its association with endothelial dysfunction, hypercoagulability, and decreased platelet function.
  • Obesity: Obesity is associated with problems in metabolism and chronic inflammation, both of which can exacerbate the risk of thrombosis.

Symptoms of Stent Thrombosis

  • Chest Discomfort (Angina): A heart attack or Stent Thrombosis can both cause severe chest discomfort. The pain may travel to the neck, jaw, arms, shoulders, or back and feel tight, pressing, or squeezing in the chest.
  • Dyspnea: Breathing Difficulties or dyspnea may result from both illnesses because the heart muscle receives less oxygen, which can cause respiratory distress.
  • Palpitations: As the heart tries to make up for reduced blood flow, irregular or fast heartbeats, or palpitations, can happen in both heart attacks and Stent Thrombosis.
  • Vomiting and Nausea: Some people who are having a heart attack or Stent Thrombosis may vomit or feel queasy. 
  • Sweating: In both cases, chest pain may be accompanied by excessive sweating, especially in the cold, which is the body's physiological reaction to stress and a reduction in cardiac output.
  • Weakness or Exhaustion: Because there is less oxygen getting to the body's tissues, both Stent Thrombosis and heart attacks can cause widespread weakness or exhaustion.
  • Dizziness or Lightheadedness: Because there is less blood flowing to the brain in these illnesses, some people may feel dizzy or lightheaded. 

What is In-Stent Restenosis (ISR)?

In-Stent Restenosis (ISR) is the re-narrowing of a coronary artery that has previously been treated with stent insertion. ISR happens when the coronary artery narrows again over time following the implantation of a stent to expand a constricted or blocked coronary artery and restore blood flow to the heart muscle. Usually, the accumulation of scar tissue at the stent site and the growth of cells within the artery wall cause this constriction. 

Features of In-Stent Restenosis (ISR)

  • Clinical Presentation: Individuals with ISR may exhibit recurrent angina symptoms, such as tiredness, dyspnea, or chest pain or discomfort. In mild situations, these symptoms may also manifest at rest, although they usually happen during physical activity. If ISR causes severe myocardial ischemia, certain patients may have myocardial infarction symptoms.
  • Timing: ISR usually happens a few months to years following the first stent implantation, while it occasionally happens sooner. Depending on the type of stent, the patient's features, and procedural circumstances, the timing of the onset of ISR may change.
  • Pathophysiology: Endothelial damage, inflammation, smooth muscle cell proliferation, and extracellular matrix deposition are some of the intricately intertwined cellular and molecular processes that contribute to the pathophysiology of ISR.
  • Risk Factors: Diabetes mellitus, hypertension, hyperlipidemia, smoking, genetic predisposition, insufficient antiplatelet medication, stent type, size, and deployment technique are among the patient- and procedure-related factors that raise the risk of ISR. To stop ISR, these risk factors must be recognised and changed.
  • Management: Optimal medical therapy, such as antiplatelet agents and lipid-lowering medications, lifestyle changes, and contemplation of repeat PCI with balloon angioplasty, drug-eluting balloon angioplasty, or repeat stent implantation are some of the management techniques for ISR. 

Causes of In-Stent Restenosis (ISR)

  • Stent Malapposition: Inadequate apposition to the artery wall or incomplete expansion of the stent can leave spaces or turbulence where neointimal hyperplasia can develop, which can result in ISR.
  • Underlying Coronary Artery Disease: Because of the existence of aberrant vascular remodeling and atherosclerotic plaques, patients with pre-existing coronary artery disease are more likely to experience an ISR event.
  • Individual Factors: A patient's genetic predisposition, diabetes mellitus, obesity, hypertension, hyperlipidemia, smoking, and other habits can all affect their chance of developing ISR.
  • Neointimal Hyperplasia: The most frequent reason for ISR is this condition. It is caused by the smooth muscle cells in the artery wall at the stent site proliferating excessively. The arterial lumen narrows as a result of tissue overgrowth.
  • Inflammatory Response: ISR may be exacerbated by inflammation at the stent site. Restenosis can result from several factors, including immunological responses, inflammatory mediators, and endothelial damage following stent implantation. These factors can encourage the growth of new cells and the development of scar tissue.
  • Stent Design and Composition: A Stent's size, composition, and kind (bare metal vs. drug-eluting) can all have an impact on the risk of ischemic stroke. 

Symptoms of In-Stent Restenosis (ISR)

  • Breathing Difficulties: Breathing difficulties or shortness of breath, particularly during physical exercise, can be brought on by a constricted coronary artery, which reduces the oxygen flow to the heart muscle.
  • Weariness: Insufficient oxygenated circulation to the heart muscle can cause generalized weakness or weariness, which lowers endurance and energy levels.
  • Palpitations: Palpitations are sensations of an irregular or fast heartbeat that happen as the heart tries to pump more blood to make up for less blood flow.
  • Dizziness or Lightheadedness: Due to decreased blood supply to the brain, some people with ISR may feel dizzy or lightheaded, especially while moving positions or exerting themselves physically.
  • Sweating: Excessive perspiration, especially during the winter months, can occur in response to chest pain or as a result of the body's stress response to reduced cardiac output.

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Similarities between Stent Thrombosis and In-Stent Restenosis (ISR)

  • Stent-Related: The existence of a stent inside a coronary artery is connected to both illnesses. A blood clot within or around the stent causes Stent Thrombosis, which causes an abrupt blockage of the artery; in contrast, ISR causes the stent to re-narrow as a result of excessive tissue growth within or around the stent.
  • Mechanical Variables: Stent Thrombosis and ISR can arise as a result of mechanical variables such stent placement, size, and design. Both problems can be more likely to occur due to factors like malapposition, insufficient lesion coverage, or under-expansion of the stent.
  • Risk Factors: There is an increased risk of both Stent Thrombosis and ISR due to certain patient-related and procedural variables. These include genetic susceptibility, smoking, diabetes mellitus, renal insufficiency, insufficient antiplatelet treatment, and operative factors such undersized stents or residual stenosis.
  • Clinical Consequences: If left untreated, Stent Thrombosis and ISR can both cause myocardial ischemia and infarction, which can have a substantial negative impact on morbidity and mortality. Similar symptoms, such as dyspnea, chest discomfort, or myocardial infarction symptoms, may appear in them.
  • Therapy Plans: Although the approaches to therapy may vary, intervention is frequently necessary for both disorders in order to restore blood flow and stop future problems. Depending on the clinical situation, treatment options may include antiplatelet therapy, anticoagulation, further stent implantation, repeat PCI with balloon angioplasty, or coronary artery bypass grafting (CABG). 

In conclusion, although both ISR and Stent Thrombosis are side effects of coronary artery stenting, they are not the same in terms of their underlying causes, clinical manifestations, onset times, and treatment approaches. An emergency, potentially fatal event that needs to be treated right away is Stent Thrombosis; on the other hand, ISR is a chronic condition that causes symptoms to recur and gradual arterial narrowing.

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What is Stent Thrombosis?

Stent Thrombosis is a dangerous side effect of coronary artery stenting that is defined by the abrupt thrombus formation inside the stent. This clot can cause an acute blockage of the artery, which increases the risk of a heart attack or sudden cardiac death.

What is ISR, or In-Stent Restenosis?

The term "In-Stent Restenosis" (ISR) describes the re-narrowing of a coronary artery following the implantation of a stent. This occurs usually as a result of the proliferation of cells within the arterial wall and causes repeated symptoms like angina or chest pain.

What are the signs of Stent Thrombosis?

Severe chest discomfort (angina), palpitations, nausea, vomiting, sweating, weakness, and dizziness are some of the symptoms of Stent Thrombosis. It is regarded as a medical emergency that needs to be attended to right away.

What signs of In-Stent Restenosis (ISR) are present?

ISR symptoms can include dizziness, exhaustion, palpitations, shortness of breath, and recurrent angina or chest discomfort. The degree of arterial re-narrowing can affect the frequency and severity of symptoms.

What are the causes of Stent Thrombosis?

Several conditions, including smoking, stent malapposition, underlying coronary artery disease, early termination or noncompliance with antiplatelet drugs, and specific types of stents, might result in Stent Thrombosis

What causes In-Stent Restenosis (ISR)?

Neointimal hyperplasia (excessive tissue development), inflammatory reactions, stent design, underlying coronary artery disease, patient-related factors (diabetes, smoking), medication non-adherence, and procedural factors are some of the factors that might lead to in-stent restenosis.

What is the similarity between Stent Thrombosis and In-Stent Restenosis (ISR)?

Both Stent Thrombosis and In-Stent Restenosis (ISR) are vascular complications of coronary artery stenting that can cause decreased blood flow and adverse cardiovascular events such as myocardial infarction or angina. Although they work in different ways, both emphasize that careful supervision is necessary to maximize stent results and patient safety.

What are the primary differences between Stent Thrombosis and In-Stent Restenosis (ISR)?

A blood clot within the stent causes rapid arterial occlusion In-Stent Thrombosis, whereas In-Stent Restenosis (ISR) gradually narrows the artery as a result of tissue proliferation and eventually presents with recurrent symptoms.