Cardiogenic Shock

For how to recognize the warning signs and what to do before help arrives, see signs of cardiogenic shock.

What happens in cardiogenic shock

Normally the heart pumps about 5 liters of blood a minute. When a large part of the heart muscle stops working, the amount pumped (cardiac output) falls. Blood pressure drops, and the coronary arteries, which fill during each heartbeat, receive less blood. That starves the heart muscle further, which weakens it more. This downward spiral is why cardiogenic shock can worsen so quickly.

Meanwhile, blood backs up behind the failing left ventricle into the lungs, causing pulmonary edema and severe breathlessness. The body releases adrenaline and tightens blood vessels to maintain pressure, causing cold, clammy skin and a fast heart rate. Over hours, the kidneys, liver, gut and brain begin to fail.

Doctors define cardiogenic shock as a systolic blood pressure below 90 mmHg for 30 minutes or more (or needing medicines to keep it above that), plus signs of poor organ blood flow such as cold limbs, confusion, low urine output or a raised blood lactate.

Causes

Heart attack

A heart attack is the classic and most common single cause. Cardiogenic shock occurs in about 5 to 10 percent of heart attacks, usually large ones with ST elevation. Mechanical complications in the days after a heart attack can also cause sudden shock:

• rupture of the muscle holding the mitral valve (acute mitral regurgitation)
• a hole in the wall between the ventricles (ventricular septal rupture)
• rupture of the outer heart wall, causing bleeding around the heart
• right ventricle infarction

Other causes

• Advanced heart failure and cardiomyopathy that suddenly decompensate
• Myocarditis, including fulminant forms after viral infections
• Stress cardiomyopathy (takotsubo), triggered by intense emotional or physical stress
• Arrhythmias: sustained ventricular tachycardia, very fast atrial fibrillation or complete heart block
• Severe valve disease: critical aortic stenosis or acute valve failure from endocarditis
• Drug toxicity: overdoses of beta blockers or calcium channel blockers
• After heart surgery

Massive pulmonary embolism and cardiac tamponade cause a similar picture called obstructive shock.

Risk factors

Older age, female sex, diabetes, previous heart attack or heart failure, and a large area of damaged heart muscle increase the risk after a heart attack. Delays in seeking help raise it further.

Stages of cardiogenic shock

The SCAI classification groups patients by severity, which guides treatment:

Diagnosis

• ECG: shows a heart attack or arrhythmia.
• Echocardiogram: shows how well the heart pumps, valve problems, ruptures and fluid around the heart.
• Blood tests: troponin (heart damage), lactate (oxygen starvation of tissues), kidney and liver function, blood gases.
• Chest X-ray: fluid in the lungs.
• Coronary angiography: dye in the heart arteries shows blockages and allows immediate treatment.
• Pulmonary artery catheter: measures pressures and cardiac output directly to fine-tune treatment.

Treatment

Reopening the blocked artery

For shock caused by a heart attack, the single most important treatment is emergency revascularization, usually percutaneous coronary intervention (stenting) of the culprit artery as fast as possible. Landmark trial evidence showed this improves long-term survival. Bypass surgery is used in some cases.

Medicines

• Vasopressors such as norepinephrine raise blood pressure.
• Inotropes such as dobutamine or milrinone strengthen heart contractions.
• Oxygen and breathing support, including mechanical ventilation if needed.
• Diuretics once blood pressure allows, to clear lung fluid.
• Antiplatelets and anticoagulants for heart attack.

Mechanical circulatory support

Devices can take over part of the heart's work while it recovers or until longer-term options are possible:

• Microaxial flow pumps (such as Impella) placed across the aortic valve. A 2024 trial in heart attack shock showed improved survival with one such device in selected patients.
• VA-ECMO: a heart-lung machine for the most severe cases.
• Intra-aortic balloon pump: once widely used, now reserved for specific situations because trials showed no survival benefit in routine use.

Ruptures and valve failures need emergency surgery. Patients who do not recover may be considered for a left ventricular assist device or heart transplant.

Complications

• acute kidney injury, sometimes needing dialysis
• liver injury and gut ischemia
• brain injury from low blood flow or cardiac arrest
• arrhythmias and cardiac arrest
• bleeding and limb problems from devices
• long-term heart failure

Outlook

Cardiogenic shock remains one of the most dangerous heart emergencies. Hospital death rates are roughly 30 to 50 percent and depend heavily on the stage when treatment starts, age, and the cause. Survivors often have heart failure and benefit from cardiac rehabilitation, heart failure medicines and close follow-up. Many return to independent living.

The best way to lower the risk is prompt treatment of heart attacks: call 911 immediately for chest pain, rather than waiting or driving yourself.

Frequently asked questions

What is cardiogenic shock?

Cardiogenic shock is a life-threatening state in which the heart pumps so weakly that blood pressure falls and organs do not receive enough oxygen. It most often follows a large heart attack and needs emergency intensive care.

What is the most common cause of cardiogenic shock?

An acute heart attack that damages a large area of the left ventricle causes most cases. Other causes include worsening heart failure, myocarditis, severe valve problems, dangerous arrhythmias and mechanical complications of a heart attack such as a ruptured valve muscle.

How is cardiogenic shock treated?

Treatment combines urgent reopening of blocked coronary arteries, medicines that raise blood pressure and strengthen the heartbeat, breathing support, and in severe cases mechanical pumps such as a microaxial flow pump or ECMO. Surgery repairs ruptures or valve failure.

What is the survival rate of cardiogenic shock?

Roughly 50 to 70 percent of patients survive to leave hospital, depending on the cause, severity and how quickly treatment starts. Earlier stages have much better outcomes than shock that has progressed to cardiac arrest or multi-organ failure.

Can the heart recover after cardiogenic shock?

Often partly, and sometimes fully. Heart muscle that was stunned but not destroyed can recover over weeks once blood flow is restored, and myocarditis or stress cardiomyopathy often recover well. Permanent damage leads to heart failure that is managed long term.