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Efficacy of istaroxime versus placebo (sodium chloride) infusion in patients with cardiogenic shock due to acute heart failure

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What is this trial about?

A plain-language summary of the goals, design and what participants do

The study looks at patients who develop cardiogenic shock as a result of acute heart failure. Cardiogenic shock is a condition where the heart cannot pump enough blood, leading to very low blood pressure and organ problems. Acute heart failure means the heart suddenly stops working well. The investigational drug being tested is istaroxime, given as an intravenous infusion. For comparison, participants may receive a standard saline solution, referred to as placebo. Both groups continue to receive all usual medical care.

The main aim is to see whether adding istaroxime improves short‑term breathing difficulty, called dyspnea, and leads to better overall outcomes such as survival and reduced need for advanced heart‑support devices. Participants will be randomly assigned to one of the two treatments, and neither the participants nor the staff will know which one is given. After the infusion starts, patients are observed for several days in the hospital, with follow‑up visits up to about three months to record any changes in breathing, need for devices like a mechanical circulatory support system or a heart transplant, hospital readmissions, and overall well‑being. The study collects information on how patients feel and how long they stay in the hospital, but does not involve any extra invasive procedures beyond the standard care.

The research process

The trial runs in 9 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Randomization and Assignment

    After giving consent, you are randomly assigned to receive either the study drug istaroxime or a matching placebo solution. The study is double‑blind, meaning neither you nor the clinical team knows which treatment you receive.

  2. Step 2

    Baseline Evaluation

    Before the infusion starts, a series of measurements are taken, including blood pressure, heart function, and a self‑rated breathing difficulty score called a visual analog scale (VAS). You also answer quality‑of‑life questions using the EQ‑VAS questionnaire.

  3. Step 3

    Start of Continuous Intravenous Infusion

    A continuous intravenous infusion is started through a vein. If you are assigned to the active group, the infusion contains istaroxime at a dose of 780 µg per kilogram of body weight. If you are assigned to the placebo group, the infusion contains 48.86 ml of sodium chloride solution. The infusion is administered continuously for up to 24 hours while you receive standard medical care for cardiogenic shock caused by acute heart failure.

  4. Step 4

    Monitoring During Infusion

    Throughout the 24‑hour infusion, your vital signs (such as blood pressure and heart rate) are monitored continuously. You are asked to rate your breathing difficulty on the VAS at regular intervals. Any side effects or complications are recorded by the study staff.

  5. Step 5

    Scheduled Assessments During the First Four Days

    You complete additional VAS ratings at 6, 12, 24, 48, 72 and 96 hours after the infusion begins. Blood pressure measurements are also taken at these times. The EQ‑VAS quality‑of‑life questionnaire is repeated at 48 hours.

  6. Step 6

    End of Infusion and Transition to Standard Care

    After the 24‑hour infusion period, the study drug or placebo is stopped. You continue to receive the usual hospital treatment for cardiogenic shock and acute heart failure, which may include medications, fluids, or devices as needed.

  7. Step 7

    Hospital Stay and Possible Advanced Therapies

    During your hospital stay, the medical team may need to use advanced therapies such as mechanical circulatory support, a durable left ventricular assist device (LVAD), heart transplantation, or invasive mechanical respiratory support. These decisions are part of standard care and are recorded for the study.

  8. Step 8

    Discharge and Follow‑Up Visits

    If you are discharged, follow‑up visits are scheduled on Day 5, Day 30 and Day 90 after the start of the infusion. At each visit you repeat the EQ‑VAS questionnaire, report any new symptoms, and undergo safety assessments for adverse events.

  9. Step 9

    Final Outcome Assessment

    The study collects information on survival, need for mechanical support, rehospitalization for heart failure, blood pressure changes, and quality‑of‑life scores up to 90 days after the infusion began. This data helps determine the effectiveness of istaroxime compared with placebo.

Who can join the trial?

9 criteria

  • Be between 18 and 80 years old at the time you sign the consent form.
  • Have cardiogenic shock caused by acute heart failure and meet all of the following:
    • Feel short of breath (dyspnea) while resting or with only a little activity.
    • Show crackling sounds in the lungs (pulmonary rales) or swelling in the lower legs (lower limb edema) when a doctor examines you.
    • Show signs of fluid buildup in the lungs (pulmonary congestion) on a chest X‑ray, CT scan, or lung ultrasound.
    • Have a low systolic blood pressure (the top number) – either 100 mmHg or less, or between 101 mmHg and 115 mmHg together with at least one sign of poor blood flow (hypoperfusion), such as cool hands or feet, very little urine output (oliguria), high lactate level (greater than 2 mmol/L), worsening kidney function (renal function) because of low blood flow, or measured low heart pumping ability (cardiac output).
    • Be admitted to the hospital for this heart problem no more than 20 hours before being placed in the study.
    • Have a recent test showing a left‑ventricular ejection fraction (LVEF) lower than 40 % (this test measures how well the main pumping chamber of the heart works) either within the past 6 months or during the current hospital stay.
    • Have a blood test that shows either NT‑proBNP higher than 1,500 pg/mL or BNP higher than 400 pg/mL (these substances rise when the heart is under stress).
    • Sign the informed consent form, agreeing to follow all study requirements and restrictions.

Who cannot join the trial?

30 criteria

  • Body weight less than 40 kg or 150 kg or more at screening.
  • Severe valvular stenosis (narrow heart valve) that has not been fixed by surgery, or moderate to severe leaking of the aortic valve.
  • Obstructive hypertrophic cardiomyopathy, restrictive cardiomyopathy, constrictive pericarditis, cardiac tamponade, heart muscle disease caused by infiltration (such as amyloidosis), iron overload (hemochromatosis), Fabry disease, myocardial dysplasia, stress‑related heart muscle problems, or acute inflammation of the heart muscle (myocarditis).
  • Sustained fast heart rhythm (ventricular tachycardia) or chaotic rhythm (ventricular fibrillation) within 30 days before screening.
  • Very slow heart rate (bradycardia, less than 50 beats per minute) or second‑ or third‑degree atrioventricular block, unless the person has a permanent pacemaker.
  • Type 1 acute coronary syndrome or heart attack (myocardial infarction) within 30 days before screening, including the current hospital stay.
  • Heart procedures such as percutaneous coronary angiography, coronary artery bypass grafting, implantation of an ICD or CRT, or other major heart surgery within one month before screening, or expected need for re‑vascularization within three months after screening.
  • Use of mechanical circulatory support devices, or need for sedation and a breathing machine (mechanical ventilation) at screening or randomization.
  • Expected need for heart transplantation or a left ventricular assist device during the study.
  • Diagnosis of a malignant tumor within one year before signing consent or at screening (except certain fully treated skin, cervical, localized prostate, or ductal breast cancers), or receiving cancer treatment at screening.
  • Any disease that the investigator believes could cause death within 90 days after randomization.
  • Rapidly worsening cardiogenic shock that requires increasing support.
  • Severe mental or psychological disorders, major cognitive impairment, or a history of serious mental illness (depression is allowed if the person can consent).
  • Known severe allergy to drugs, foods, or specifically to istaroxime or its ingredients (including lactose).
  • Pregnancy, breastfeeding, or planning to become pregnant.
  • Inability to use effective birth control from signing consent until 30 days after the last dose of study drug, or planning to donate sperm/eggs during that time.
  • Childbearing potential without a negative highly sensitive serum pregnancy test within 24 hours before the first dose.
  • Participation in another clinical study or receipt of another investigational drug/device within 30 days before signing consent, or still in follow‑up of another study.
  • Inability to follow all study requirements.
  • Any other situation the investigator feels makes participation unsuitable.
  • Systolic blood pressure (top number) greater than 130 mmHg within 2 hours before randomization.
  • Use of vasodilators such as nitroglycerin, nitrates, or recombinant human brain natriuretic peptide within 6 hours before screening.
  • Use of digoxin (a heart medication) within 7 days before randomization.
  • Taking a medication that is a CYP2C19 substrate (a type of drug‑metabolism pathway).
  • Severe lung disease that requires oral steroids, immune‑suppressing therapy, or home oxygen; respiratory failure; or severe high blood pressure in the lungs (pulmonary hypertension).
  • Recent stroke (acute ischemic or hemorrhagic cerebral infarction) or mini‑stroke (transient ischemic attack) within 30 days before screening.
  • Abnormal laboratory findings at screening:
    • Renal impairment: estimated glomerular filtration rate (eGFR) less than 25 ml/min/1.73 m² or need for long‑term dialysis.
    • Severe electrolyte imbalance: sodium less than 120 mmol/L or more than 160 mmol/L, and/or potassium less than 3.2 mmol/L or more than 5.5 mmol/L.
    • Liver function impairment: ALT or AST more than three times the normal limit, or bilirubin more than 1.5 times normal.
    • Low hemoglobin: less than 9 g/dL.
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Investigated drugs

Istaroxime is a medication given through an IV drip that is being tested to see if it can help patients who are in early cardiogenic shock caused by acute heart failure. In the study, patients receive a continuous infusion of istaroxime along with the usual treatments doctors normally give for this condition. The goal is to find out whether istaroxime can reduce short‑term breathing difficulty, lower the risk of death, decrease the need for more invasive heart procedures, improve overall health, and enhance quality of life compared with the standard care alone.

What is already known about the treatment

  • Istaroxime

    Istaroxime is supplied as a sterile powder that is mixed with liquid and given continuously by intravenous infusion. It is still an investigational drug, currently in phase 2b/3 clinical trials and not yet approved for routine medical use. The medication is being tested for patients with cardiogenic shock caused by acute heart failure to help the heart pump more strongly. It works by gently blocking a cell pump that controls sodium and by improving calcium movement in heart cells, placing it in the class of cardiac inotropic agents.

  • Sodium chloride

    Sodium chloride is provided as a clear solution that is infused directly into a vein (IV saline). It is an approved and widely used electrolyte fluid that restores fluid and salt balance but has no specific therapeutic effect for cardiogenic shock, serving as the placebo in this study. The solution simply supplies sodium and water to the bloodstream and is classified as an isotonic crystalloid intravenous fluid. It is used in the trial to match the administration method of the test drug.

Investigated diseases

  • Cardiogenic shock

    This condition occurs when the heart cannot pump enough blood, causing low blood pressure and reduced blood flow to organs. It usually develops quickly in people with severe heart dysfunction. Common signs include rapid breathing, cool skin, and little urine output. As circulation remains insufficient, organs receive less oxygen, which can further weaken heart performance. The shock may continue unless the heart’s pumping ability improves or is supported.

  • Acute heart failure

    This is a sudden worsening of the heart’s ability to move blood, leading to fluid buildup and shortness of breath. It can be triggered by a heart attack, uncontrolled high blood pressure, or problems with heart valves. The pressure increase in the lungs causes breathing difficulty and coughing. Fluid may also collect in the legs and abdomen, causing swelling. If the heart’s function keeps declining, symptoms become more pronounced and can lead to shock.

Trial detailsLast updated 12 Nov 2026
Age18+ yearsPhasePhase IVTrial ID2026-527261-29-00Protocol codeSeismic-ista-001Estimated enrolment545 patientsSponsorSeismic Pharmaceuticals Operations LLC

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