Mi And Stroke: What's The Link?

Myocardial infarction (MI) is a leading cause of mortality and can be complicated by stroke, which is one of the most feared complications. The incidence of stroke in acute MI is higher than in the overall population, with the risk of stroke increasing with the number of risk markers. The risk of stroke is highest in the first four weeks after MI, but remains heightened for up to 12 weeks. The incidence of stroke following acute MI is anywhere between 0.7% and 2.2%, with short-term and 1-year mortalities of 30.1% and 36.5%, respectively. The risk factors for stroke following MI include older age, history of stroke, hypertension, diabetes, atrial fibrillation, and no aspirin on discharge. The management of stroke in acute MI is best handled by a team of specialists, including a cardiologist and neurologist.

Incidence of stroke in MI

The risk of stroke after a myocardial infarction (MI) is significantly higher than in the general population. The incidence of stroke post-MI has been found to be anywhere between 0.7 and 2.4%, with older age, history of stroke, and hypertension being independent predictors. The incidence of stroke in the acute phase following an MI varies considerably between studies, with rates mostly in the range of 0.8% to 3.2%.

Pre-Thrombolytic Era

In the pre-thrombolytic era, the incidence of stroke post-MI was 1.7 to 2.4% with a mortality rate of up to 60%.

Thrombolytic Therapy

The introduction of thrombolytic therapy has decreased the incidence of ischemic strokes while increasing the risk of hemorrhagic stroke. The incidence of stroke in the first 30 days post-MI was found to be 44 times higher than in the general population, with a sharp decline in the incidence of stroke in the following year.

Primary PCI

The preferred reperfusion strategy in ST-elevation MI (STEMI) is primary percutaneous coronary intervention (PPCI), which has been found to be superior to thrombolysis in reducing short-term and long-term mortalities. However, delays in PCI can result in an increased risk of stroke.

Pharmacoinvasive Approach

The pharmacoinvasive approach, which involves immediate thrombolysis followed by PCI within 2 to 24 hours, has been found to have a slightly higher risk of stroke compared to PPCI.

Risk Factors

The risk of stroke following an MI varies with age, with older patients being at a higher risk. Prior history of stroke, hypertension, diabetes, atrial fibrillation, and no aspirin on discharge are independent predictors of an ischemic stroke. For hemorrhagic stroke, the risk factors include older age, history of hypertension, acute hypertension, thrombolysis, and prior history of stroke.

Management

The management of stroke in patients with acute MI is complex and requires a multidisciplinary approach. The type of stroke should be identified through intracranial imaging, and general supportive management should be instituted. The systolic and diastolic blood pressure should be maintained below certain thresholds, and blood sugar levels should be controlled. The appropriate time to restart antiplatelet therapy following an intracerebral hemorrhage in the setting of acute MI is debatable and requires a multidisciplinary approach.

Risk factors for stroke in acute MI

Acute myocardial infarction (MI) is a leading cause of death globally. While advancements in pharmacotherapy and revascularization techniques have improved survival rates, the mortality rate from stroke following acute MI remains high. The risk of stroke is higher in patients with acute MI than in the general population. The risk factors for stroke in acute MI patients include older age, history of stroke, hypertension, diabetes, atrial fibrillation, and no aspirin on discharge. The pathophysiology of stroke in acute MI involves increased catecholamine release, which aggravates platelet aggregation and thrombosis, leading to ischemic stroke. Additionally, embolization during revascularization, atrial fibrillation, and blood stasis in patients with left ventricular dysfunction can also cause ischemic stroke. Hemorrhagic stroke, while less frequent, carries a higher mortality rate. The management of stroke in acute MI patients requires a multidisciplinary approach involving a cardiologist, neurologist, anesthesiologist, and neurosurgeon. Urgent intracranial imaging is necessary to determine the type of stroke and guide management. The prognosis for patients with stroke and acute MI is poor, with higher in-hospital and long-term mortalities compared to stroke alone.

Pathogenesis of stroke in acute MI

Stroke is a neurological disorder characterised by blockage of blood vessels. Clots form in the brain and interrupt blood flow, clogging arteries and causing blood vessels to break, leading to bleeding. The rupture of the arteries leading to the brain during stroke results in the sudden death of brain cells due to a lack of oxygen.

The pathophysiology of stroke in acute MI is complex and involves a multitude of factors. The risk of stroke in patients with acute MI is heightened due to the increased catecholamine release, which aggravates platelet aggregation and thrombosis. MI itself can also result in ischemic stroke through embolisation, either during revascularisation, due to atrial fibrillation in association with MI, or from blood stasis in patients with left ventricular dysfunction.

The risk of stroke is also influenced by the reperfusion therapy and revascularisation procedures used to treat acute MI. The use of dual antiplatelet and glycoprotein IIb/IIIa inhibitors increases the risk of hemorrhagic stroke, especially in elderly patients.

The pathogenesis of stroke in acute MI is further complicated by the development of new-onset atrial fibrillation, which increases the risk of ischemic stroke and transient ischemic attacks.

Management of stroke in acute MI

The management of stroke in acute MI is a complex and challenging scenario that requires a multidisciplinary approach involving cardiologists, neurologists, and other specialists. Here are some key considerations and strategies for managing stroke in patients with acute myocardial infarction (MI):

• Early Recognition and Risk Assessment: It is crucial to recognize the signs and symptoms of stroke in patients with acute MI promptly. Risk factors such as older age, history of stroke, hypertension, diabetes, and atrial fibrillation increase the likelihood of stroke in these patients.
• Neurological Assessment and Imaging: Perform a comprehensive neurological examination to evaluate the patient's neurologic status, including motor function, sensory function, speech, and gaze. Obtain urgent intracranial imaging, such as a CT scan or MRI, to determine the type of stroke (ischemic or hemorrhagic) and guide further management.
• Cardiological Assessment: Simultaneously, conduct a cardiological assessment to identify the location and extent of the MI. This may include electrocardiogram (ECG) monitoring, cardiac enzyme measurements, and echocardiography to assess cardiac function and identify any complications.
• Blood Pressure Management: Optimizing blood pressure is critical. Maintain systolic blood pressure below 185 mm Hg and diastolic blood pressure below 110 mm Hg. In patients with relatively low blood pressure, consider interventions to increase blood pressure and improve cerebral perfusion.
• Blood Glucose Control: Closely monitor and control blood glucose levels. Target a glucose level between 140-180 mg/dL to avoid both hyperglycemia and hypoglycemia, which can aggravate neuronal ischemia.
• Thrombolytic Therapy: The decision to use thrombolytic therapy, such as intravenous tissue plasminogen activator (t-PA) or tenecteplase (tNK), depends on the type of stroke and the time window since the onset of symptoms. Thrombolysis can be considered for eligible patients within 3-4.5 hours of symptom onset.
• Intravenous Access and Cardiac Monitoring: Establish intravenous access and initiate cardiac monitoring to manage arrhythmias and other cardiac complications associated with acute MI.
• Airway and Breathing Management: Ensure adequate airway protection and ventilation. Rapid sequence intubation may be necessary for patients with decreased Glasgow Coma Scale scores or inadequate airway protection.
• Intensive Care and Multidisciplinary Approach: Manage patients in a neurology intensive care unit with a multidisciplinary team, including a cardiologist, neurologist, anesthesiologist, and neurosurgeon. Provide general supportive care, such as controlling body temperature and maintaining adequate oxygenation.
• Stroke-Specific Interventions: Depending on the type of stroke, consider additional interventions. For ischemic stroke, mechanical thrombectomy may be beneficial if performed within 6 hours of symptom onset or even up to 24 hours in select cases. For hemorrhagic stroke, focus on controlling bleeding, lowering intracranial pressure, and preventing hematoma expansion.
• Antiplatelet and Anticoagulant Therapy: The use of antiplatelet and anticoagulant therapy requires careful consideration. These agents can increase the risk of bleeding and should be managed in consultation with the neurology team.
• Long-term Management and Rehabilitation: Provide ongoing care and rehabilitation to improve long-term outcomes. This may include physical therapy, occupational therapy, and speech therapy, as well as secondary stroke prevention strategies to reduce the risk of recurrent stroke.

Stroke and MI: a bidirectional Mendelian randomization study

Stroke and Myocardial Infarction: A Bidirectional Mendelian Randomization Study

Stroke and myocardial infarction (MI) are associated with each other, as demonstrated in observational studies. However, it is unclear whether this relationship is causal, and the purpose of this study was to explore the bidirectional causality between stroke and MI.

Methods

Causality between stroke and MI was assessed using two-sample Mendelian randomization (MR). All genetic instruments related to stroke (40,585 cases; 406,111 controls) and MI (43,676 cases; 128,199 controls) were derived from large published genome-wide association studies. The MR analysis was calculated with inverse-variance weighting, MR-Egger, weighted mode, weighted median, and simple mode methods, and sensitivity analyses are used to detect the heterogeneity or pleiotropy.

Results

Genetically predicted large-artery stroke (LAS) was causally related to higher odds of MI (odds ratio [OR] = 1.13, 95% confidence interval [CI]: 1.06-1.20, p = 1.0×10^-4), and the causal effect of LAS on MI was significantly weakened (OR = 1.09, 95% CI: 1.02-1.17, p = 0.017) after excluding the multipotent single-nucleotide polymorphisms (SNPs). MI phenotypes were genetically correlated with all ischemic strokes (OR = 1.15, 95% CI: 1.03-1.28, p = 0.013) and LAS (OR = 1.39, 95% CI: 1.14-1.71, p = 0.001); but a causal effect of MI on all ischemic strokes (OR = 1.00, 95% CI: 0.95-1.28, p = 0.219) and LAS (OR = 1.26, 95% CI: 0.93-1.69, p = 0.130) was not observed after excluding the multipotent SNPs.

This MR analysis provides evidence to support the causal effect of LAS subtype on MI, and some factors act as confiding factors whereas others may act as mediators.

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