Inclusion Criteria:

• Adults between the ages of 18 and 85, inclusive
• Symptoms consistent with acute ischemic stroke, with a measurable neurological deficit at presentation
• Ability to initiate external counterpulsation within 48 hours of stroke onset
• No evidence of hemorrhage on CT scan
• MCA distribution stroke: a total or partial anterior circulation infarct (TACI or PACI by Oxfordshire criteria) consistent with MCA distribution ischemia, or a lacunar stroke felt by the investigator to possibly involve a deep perforating branch in the MCA territory (LACI by Oxfordshire criteria)

Exclusion Criteria:

• Rapidly resolving stroke symptoms consistent with a transient ischemic attack
• Severe stroke defined as an NIHSS > 22, or a minor stroke defined as an NIHSS < 5
• Intracranial hemorrhage (SAH, EDH, SDH, IPH, hemorrhagic conversion) on CT scan
• Brain tumor or brain abscess on CT scan
• Presentation consistent with subarachnoid hemorrhage (such as a sudden, severe thunderclap headache, or an associated third nerve palsy)
• History of cerebral aneurysm, AVM, or hemorrhagic stroke
• Either treatment or planned treatment of current stroke with standard thrombolytic therapy (intravenous or intra-arterial) or neurothrombectomy
• History of lower limb amputation above the ankle
• History of untreated aortic dissection
• History or suspicion of thoracic or abdominal aortic aneurysm
• Known significant anomaly of the heart, aorta, or great vessels that would be complicated by elevated diastolic pressures.
• BP > 180/100 that remains so after minimal treatment (such as one or two doses of an antihypertensive agent, or as determined by the investigator)
• History of non-trivial aortic regurgitation, or any symptomatic valvular heart disease determined by the investigator to be at risk of worsening on ECP
• Significant symptomatic congestive heart failure (orthopnea, CHF-related dyspnea, or rales and jugular venous distention on exam) or a left ventricular ejection fraction known to be <30%
• Diagnosis of significant lower extremity peripheral vascular occlusive disease (PVOD), or symptomatic PVOD as determined by the investigator (especially symptoms of claudication)
• Phlebitis, stasis ulcer, severe varicosities
• Diagnosis of DVT within the past month, or current symptoms strongly suggestive of new DVT, such as asymmetric calf or leg swelling, discomfort, or erythema (to be evaluated by screening duplex)
• Pacemaker or automated implanted defibrillator (AICD)
• A cardiac dysrhythmia (such as atrial fibrillation or atrial flutter, or frequent premature ventricular contractions (PVCs) or premature atrial contractions (PACs) as determined by the investigator) that would interfere with ECP triggering
• Pregnancy (as determined by a urine pregnancy test in females of child-bearing age)
• Known coagulopathy, thrombocytopenia with platelet count < 100,000, or taking warfarin with an INR > 2.0.
• History positive for chronic low back pain, radiculopathy suggestive of herniated lumbar disc, or related surgery
• Known collagen vascular disease
• Obesity to a degree (as determined by the investigator) that would prevent proper placement and/or activation of counterpulsation cuffs
• Any psychological, social, or legal condition that would interfere with the ability of the patient or his or her surrogate to give Informed Consent and/or his or her capacity to comply with all study requirements, including the necessary time commitment
• An inadequate temporal window for TCD insonation.
• Currently involved or have been involved in a clinical trial within the last 30 days.