STEMI - Reperfusion therapy

Question 1

When should a patient be considered a candidate for reperfusion therapy?

Answer 1

• ST-segment elevation of:
  
  • At least 2 mm in two contiguous precordial leads
  • At least 1 mm in two adjacent limb leads

Question 2

Is fibrinolysis beneficial in a patient without ST-segment elevation?

Answer 2

Fibrinolysis is not helpful, and evidence exists suggesting that it may be harmful

Question 3

While the central zone of the infarct contains necrotic tissue that is irretrievably lost, the fate of the surrounding ischemic myocardium (ischemic penumbra) may be improved by:

Answer 3

• Timely restoration of coronary perfusion
• Reduction of myocardial O₂ demands
• Prevention of the accumulation of noxious metabolites, and blunting of the impact of mediators of reperfusion injury (e.g., calcium overload and oxygen-derived free radicals)

Question 4

How many percent of patients with STEMI may achieve spontaneous reperfusion of the infarct-related coronary artery within 24 h and experience improved healing of infarcted tissue?

Answer 4

Up to one-third of patients

Question 5

Value of NSAIDs in STEMI

Answer 5

Glucocorticoids and nonsteroidal anti-inflammatory agents, with the exception of aspirin, should be avoided in patients with STEMI

Question 6

Glucocorticoids and nonsteroidal anti-inflammatory agents, with the exception of aspirin, should be avoided in patients with STEMI. Why?

Answer 6

• Impair infarct healing
• Increase the risk of myocardial rupture
• Use may result in a larger infarct scar
• Increase coronary vascular resistance, thereby potentially reducing flow to ischemic myocardium

Question 7

What is primary PCI?

Answer 7

PCI, usually angioplasty and/or stenting without preceding fibrinolysis

Question 8

Advantages of PCI

Answer 8

• Applicable to patients who have contraindications to fibrinolytic therapy but otherwise are considered appropriate candidates for reperfusion
• More effective than fibrinolysis in opening occluded coronary arteries and, when performed by experienced operators in dedicated medical centers, is associated with better short-term and long-term clinical outcomes

Question 9

Compared with fibrinolysis, primary PCI is generally preferred when:

Answer 9

• Bleeding risk is increased
• Cardiogenic shock is present
• Diagnosis is in doubt
• Symptoms have been present for at least 2–3 h when the clot is more mature and less easily lysed by fibrinolytic drugs

Question 10

If no contraindications are present, fibrinolytic therapy should ideally be initiated within ____ with the principal goal of ____

Answer 10

• 30 min of presentation (i.e., door-toneedle time ≤30 min)
• Prompt restoration of full coronary arterial patency

Question 11

Fibrinolytic agents

• Examples
• Mechanism of action

Answer 11

• Examples
  
  • Tissue plasminogen activator (tPA)
  • Streptokinase
  • Tenecteplase (TNK)
  • Reteplase (rPA)
• Mechanism of action
  
  • Act by promoting the conversion of plasminogen to plasmin, which subsequently lyses fibrin thrombi

Question 12

Less effective fibrinolytic agent

Answer 12

Streptokinase

Question 13

Agents referred to as bolus fibrinolytics and why

Answer 13

• Tenecteplase (TNK)
• Reteplase (rPA)
  
  • Since their administration does not require a prolonged intravenous infusion

Question 14

When assessed angiographically, flow in the culprit coronary artery is described by a simple qualitative scale called the Thrombolysis in Myocardial Infarction (TIMI) grading system. What are the TIMI grades and their interpretation?

Answer 14

• Grade 0
  
  • Complete occlusion of the infarct-related artery
• Grade 1
  
  • Some penetration of the contrast material beyond the point of obstruction, but without perfusion of the distal coronary bed
• Grade 2
  
  • Perfusion of the entire infarct vessel into the distal bed, but with flow that is delayed compared with that of a normal artery
• Grade 3
  
  • Full perfusion of the infarct vessel with normal flow

Question 15

Dosages of fibrinolytics

• Tissue plasminogen activator (tPA)
• Streptokinase
• Tenecteplase (TNK)
• Reteplase (rPA)

Answer 15

• tPA
  
  • 15-mg bolus followed by 50 mg intravenously over the first 30 min, followed by 35 mg over the next 60 min
• Streptokinase
  
  • 1.5 million units (MU) intravenously over 1 h
• TNK
  
  • Single weight-based intravenous bolus of 0.53 mg/kg over 10 s
• rPA
  
  • Double-bolus regimen consisting of a 10-MU bolus given over 2–3 min, followed by a second 10-MU bolus 30 min later

Question 16

Clear contraindications to the use of fibrinolytic agents

Answer 16

• History of CVD hemorrhage at any time
• Nonhemorrhagic stroke or other cerebrovascular event within the past year
• Marked hypertension (a reliably determined systolic arterial pressure >180 mmHg and/or a diastolic pressure >110 mmHg) at any time during the acute presentation
• Suspicion of aortic dissection
• Active internal bleeding (excluding menses)

Question 17

Can you start fibrinolysis in an elderly patient?

Answer 17

• Yes
• While advanced age is associated with an increase in hemorrhagic complications, the benefit of fibrinolytic therapy in the elderly appears to justify its use if no other contraindications are present and the amount of myocardium in jeopardy appears to be substantial