Cardiogenic Shock: Symptoms, Causes & Treatment

Cardiogenic shock definition

Cardiogenic shock, also known as cardiac shock, is a life-threatening medical emergency in which the heart suddenly fails to pump enough blood to meet the body’s needs. As a result, vital organs such as the brain, kidneys, and liver do not receive enough oxygen and nutrients. It mostly occurs as a severe complication of a large heart attack, but it can also result from advanced heart failure, severe heart muscle damage, serious heart rhythm disturbances, or mechanical problems of the heart valves or walls.

Cardiogenic shock can be identified by persistently low blood pressure (usually systolic blood pressure below 90 mmHg), signs of poor organ perfusion (such as cold, clammy skin; confusion; reduced urine output), and evidence of reduced cardiac output despite adequate fluid levels. Symptoms may include chest pain, severe shortness of breath, rapid or weak pulse, extreme fatigue, dizziness, altered mental status, and fainting.

Major causes include acute myocardial infarction (heart attack), severe cardiomyopathy, myocarditis, life-threatening arrhythmias, valvular heart disease, and complications such as ventricular septal rupture or papillary muscle rupture. Complications can involve multi-organ failure, kidney injury, respiratory failure, metabolic acidosis, abnormal heart rhythms, and death if not treated urgently.

A cardiologist or critical care specialist can accurately diagnose and provide emergency treatment for cardiogenic shock.

Incidence of cardiogenic shock Worldwide

Around the world, cardiogenic shock most often happens after a major heart attack and affects about 5–10% of patients admitted with acute myocardial infarction. In high-income countries, it occurs in about 30–50 people per 100,000 each year, and the numbers have slightly increased due to better diagnosis and an aging population. Even with modern treatment, the death rate remains high at about 30–50%.

Indian registry data show that cardiogenic shock occurs in approximately 3% to 10% of patients hospitalized with acute myocardial infarction (AMI). Large national datasets such as the National Interventional Council registry (2018) report cardiogenic shock in about 3.3% of PCI cases, while regional STEMI registries like the CSI–Kerala registry report rates around 3–5%.

Cardiogenic shock can be classified in different ways depending on the cause of pump failure and which ventricle is involved. These classifications help doctors identify the underlying problem and decide on the most appropriate emergency treatment. The cardiogenic shock classifications are as follows:

Based on cause (etiology)

• Myocardial causes (myocardial cardiogenic shock)
• Mechanical causes
• Arrhythmic causes

Based on the ventricle involved

• Left ventricular shock (most common)
• Right ventricular shock
• Biventricular shock

Myocardial causes: Myocardial cardiogenic shock happens when the heart muscle is severely damaged, most commonly due to a large heart attack. The weakened muscle cannot pump enough blood, leading to low blood pressure and poor blood supply to vital organs.

Mechanical causes: Mechanical cardiogenic shock is caused by rapid structural injury to the heart, such as valve or septal rupture, or cardiac tamponade. Although the heart muscle can contract, the structural abnormality hinders effective blood flow, resulting in a dramatic reduction in cardiac output and blood pressure.

Arrhythmic causes: Arrhythmic cardiogenic shock occurs due to severe abnormal heart rhythms. Very fast or very slow heart rates reduce effective blood pumping, leading to decreased cardiac output and signs of shock, even if the heart muscle is structurally normal.

Left ventricular shock: Left ventricular cardiogenic shock occurs when the left side of the heart is unable to adequately pump blood, usually as a result of a massive heart attack. This causes blood to back up in the lungs, resulting in shortness of breath and fluid accumulation. At the same time, diminished blood flow to the body causes low blood pressure, inadequate organ perfusion, and shock. 

Right ventricular shock: Right ventricular cardiogenic shock occurs when the right side of the heart fails to properly pump blood, which is frequently caused by a right-sided heart attack or excessive lung pressure. This lowers blood flow to the left heart, resulting in lower overall cardiac output. As a result, blood pressure lowers, causing shock. 

Biventricular shock: Biventricular cardiogenic shock occurs when both the left and right ventricles fail simultaneously. This may happen in extensive heart damage, advanced heart failure, or severe cardiomyopathy. This leads to severe hypotension, widespread congestion, and a high risk of organ failure, making it a more critical and complex form of cardiogenic shock.

Understanding the pathophysiology is important because it explains how initial heart damage progresses to low blood pressure, poor organ perfusion, and life-threatening complications. The condition follows a series of interconnected mechanisms that create a worsening cycle of pump failure and reduced circulation. Below are the mechanism involving on pathogenesis of cardiogenic shock:

Primary cardiac pump failure

Cardiogenic shock typically begins with substantial heart muscle injury, which is usually caused by a severe heart attack, myocarditis, or progressive heart failure. When a large section of the heart muscle is weakened, it is unable to contract properly, reducing heart contractility and limiting the heart from pumping enough blood forward to nourish the body's organs.

Reduced cardiac output and systemic hypoperfusion

Because the heart’s pumping ability decreases, cardiac output falls. As a result, blood pressure drops and vital organs such as the brain, kidneys, and liver receive less oxygen and nutrients. This poor circulation (hypoperfusion) leads to symptoms such as confusion, low urine output, cold skin, and fatigue. If continued, it causes tissue hypoxia and buildup of lactic acid.

Compensatory neurohormonal activation 

To compensate for low blood pressure, the body engages its stress systems. These mechanisms raise the heart rate, constrict the blood arteries, and retain salt and water to keep blood pressure stable. This raises the heart's strain and oxygen demand, weakening the injured cardiac muscle and exacerbating the shock. 

Pulmonary congestion and the vicious cycle of organ failure

When the left side of the heart cannot pump blood forward, blood backs up into the lungs, increasing pressure and causing fluid accumulation. This leads to severe breathlessness and reduced oxygen levels. Meanwhile, low blood flow to the heart itself further reduces coronary circulation, causing additional heart damage. This creates a vicious cycle of worsening pump failure, falling blood pressure, and progressive multiorgan dysfunction if not treated urgently.

Cardiogenic shock occurs when the heart cannot pump enough blood to meet the body's needs, resulting in poor circulation and organ dysfunction. Early recognition of symptoms is important, as this is a medical emergency. Common signs and symptoms of cardiogenic shock are:

• Hypotension (low blood pressure)
• Rapid, weak pulse (tachycardia and thready pulse)
• Cold, clammy, pale skin 
• Shortness of breath and rapid breathing
• Chest pain or discomfort
• Decreased urine output
• Confusion, dizziness, or altered mental status 
• Fatigue and extreme weakness

Hypotension (low blood pressure): In cardiogenic shock, the heart is unable to pump blood effectively, leading to a drop in blood pressure. This insufficient pressure means organs like the brain, kidneys, and liver do not receive enough blood and oxygen, which can cause dizziness, fainting, and, if untreated, organ damage.

Rapid, weak pulse (tachycardia with thready pulse): When the heart cannot pump strongly, the body tries to compensate by increasing the heart rate. However, even though the heart beats faster, each beat is weak because of poor pumping ability. As a result, the pulse feels rapid but faint or thready when checked at the wrist or neck.

Cold, clammy, pale skin: When the heart cannot circulate blood properly, the body redirects blood to vital organs like the brain and heart. This reduces blood flow to the skin, causing it to feel cold, appear pale, and become sweaty. These changes are visible signs of reduced circulation.

Shortness of breath and rapid breathing: If blood backs up into the lungs due to poor pumping, fluid can accumulate in the lungs, making it hard to breathe. The body responds by breathing faster to try to get more oxygen, which may also cause a feeling of breathlessness.

Chest pain or discomfort: Chest pain is caused by a heart attack or severe heart injury. It occurs because parts of the heart muscle are not receiving enough blood, which can damage heart tissue and worsen heart function.

Decreased urine output: The kidneys depend on sufficient blood flow to filter waste and produce urine. In cardiogenic shock, reduced circulation limits kidney function, which may result in lower urine output. 

Confusion, dizziness, or altered mental status: In cardiogenic shock, inadequate circulation can cause confusion, dizziness, difficulty concentrating, or even fainting. These neurological changes are an important sign that the body is not receiving enough oxygen.

Fatigue and extreme weakness: With poor blood flow and oxygen delivery to muscles and organs, patients feel unusually tired and weak. Even simple activities may become exhausting, reflecting the body’s struggle to maintain essential functions.

Cardiogenic shock occurs when the heart suddenly fails to pump enough blood to meet the body’s needs. The following are common cardiogenic shock etiology conditions that can directly impair the heart’s pumping ability:

• Acute myocardial ischemia 
• Mechanical defect
• Contractility defect
• Massive pulmonary embolus
• Ventricular failure 
• Aortic dissection 
• Certain cardiotoxic drugs
• Arrhythmias or endocarditis 

Acute myocardial ischemia: A sudden blockage of a coronary artery reduces blood flow to the heart muscle, causing oxygen deprivation and weakened contraction. This reduces the heart's ability to pump, resulting in low blood pressure and insufficient blood supply to the organs. If not treated promptly, it might lead to cardiac arrest.

Mechanical defect: This is structural damage to the heart that happens quickly, usually following a major heart attack. Examples include rupture of the ventricular septum, papillary muscle rupture causing severe mitral regurgitation, or free wall rupture. These structural abnormalities interfere with normal blood flow within the heart, impair effective pumping, and rapidly produce decreased cardiac output, resulting in cardiac shock.

Contractility defect: This refers to the inability of the heart muscle to contract with adequate strength. This may occur due to prior heart damage, inflammation, or metabolic disturbances. When the heart cannot generate sufficient force to pump blood effectively, cardiac output decreases, resulting in poor tissue perfusion and signs of cardiogenic shock.

Massive pulmonary embolus: It is a blood clot that blocks one of the pulmonary arteries in the lungs. This blockage increases resistance to blood flow from the right side of the heart, causing sudden strain and possible right ventricular failure. When the right ventricle cannot pump blood forward, overall cardiac output decreases, which may lead to shock.

Ventricular failure: Left ventricular failure is the most common direct cause of cardiogenic shock. When the left ventricle cannot pump blood effectively into the systemic circulation, blood pressure drops, and organs receive inadequate oxygen. In severe cases, both ventricles may fail (biventricular failure), worsening circulatory collapse and leading to shock.

Aortic dissection: Aortic dissection is a life-threatening condition in which there is a tear in the inner layer of the aorta. If the dissection affects the coronary arteries or causes severe aortic valve leakage, it might reduce blood supply to the heart muscle. This reduces cardiac output and may rapidly lead to cardiogenic shock.

Certain cardiotoxic drugs: Certain cardiotoxic drugs, such as some chemotherapy agents or overdose of certain medications (beta-blockers or calcium channel blockers), can directly damage heart muscle cells. This damage weakens the heart’s contractility and may cause acute heart failure. When the heart cannot pump sufficient blood due to drug-induced injury, cardiogenic shock may develop.

Arrhythmias or endocarditis: Severe arrhythmias (such as ventricular tachycardia and total heart block) or infective endocarditis interfere with heart pumping by disrupting rhythm or damaging valves, reducing cardiac output and increasing the risk of cardiogenic shock.

Cardiogenic shock usually develops as a serious complication of acute heart problems, especially after a major heart attack. Certain patient-related and clinical factors increase the likelihood of severe cardiac dysfunction, making the heart more vulnerable to pump failure. The following are important risk factors of cardiogenic shock and how they contribute to its development:

• Advanced age
• Female gender
• Previous heart conditions
• Underlying medical condition
• Being obese
• Recent heart surgery
• Lifestyles factors

Advanced age: Older individuals have a higher risk because the heart muscle and blood vessels naturally lose strength and elasticity with age. Elder patients are more likely to have extensive coronary artery disease and reduced cardiac reserve. When a heart attack or acute cardiac event occurs, the weakened heart may not tolerate the stress, increasing the risk of cardiogenic shock.

Female gender: Women, particularly older women, may present with atypical symptoms of a heart attack, leading to delayed diagnosis and treatment. Studies shown that women have smaller coronary arteries and may experience more complications following myocardial infarction. These factors can increase the severity of cardiac injury and the risk of shock.

Previous heart conditions: A history of coronary artery disease, previous myocardial infarction, heart failure, cardiomyopathy, or valve disease significantly increases cardiogenic shock risk. If the heart is already weakened or scarred, it has less ability to compensate during an acute event.

Underlying medical conditions: Chronic conditions like diabetes, hypertension, chronic kidney disease, and chronic lung disease contribute to vascular damage and cardiac strain over time. These disorders increase the severity of coronary artery disease and reduce the heart’s functional reserve, making cardiogenic shock more likely during acute cardiac stress.

Being obese: Obesity is associated with hypertension, diabetes, dyslipidemia, and coronary artery disease. Excess body mass index (BMI) increases the workload of the heart and contributes to structural and functional heart changes.

Recent heart surgery: Cardiac surgeries, including bypass or valve replacement procedures, temporarily stress the heart. Postoperative complications such as myocardial injury, arrhythmias, bleeding, or infection may impair cardiac output. In high-risk patients, these complications can progress to cardiogenic shock.

Lifestyle factors: Lifestyle habits like smoking, excessive alcohol intake, physical inactivity, and an unhealthy diet contribute to coronary artery disease and heart failure. These behaviours accelerate atherosclerosis and weaken cardiac function over time. When a major cardiac event occurs, individuals with these risk factors are more likely to develop severe pump failure leading to cardiogenic shock.

Frequently Asked Questions (FAQs) on Cardiogenic Shock

Early symptoms of cardiogenic shock include:

• Low blood pressure (hypotension)
• Rapid and weak pulse
• Cold, clammy skin
• Dyspnea (shortness of breath)
• Chest discomfort or pain
• Dizziness or lightheadedness
• Confusion or altered mental status
• Extreme weakness or fatigue
• Oliguria (decreased urine output)

Blood pressure depends on how effectively the heart pumps blood and how well blood vessels maintain tone. In cardiogenic shock, the heart’s pumping power is severely reduced due to muscle damage or dysfunction. As cardiac output falls, less blood is pushed into circulation, causing a drop in blood pressure. Although the body attempts to compensate by narrowing blood vessels and increasing heart rate, these measures are often insufficient, leading to persistent low blood pressure and poor organ perfusion.

Cardiogenic shock can recur, particularly in patients with severe underlying heart disease. Recurrent heart attacks, ongoing heart failure, serious rhythm disturbances, or untreated coronary artery disease increase the risk. Proper treatment of the initial cause, long-term heart medications, lifestyle changes, and close follow-up care significantly reduce the risk of recurrence.

Cardiogenic shock occurs when the heart cannot pump enough blood to vital organs. If not treated quickly, it can lead to multi-organ failure, including kidney failure, liver damage, and brain injury due to poor blood supply. Life-threatening irregular heartbeats and cardiac arrest may occur. Reduced oxygen delivery can also cause confusion, coma, or permanent neurological damage. Despite modern treatment, mortality remains high in severe cases when associated with large heart attacks.

Cardiogenic shock is uncommon in the general population but is a serious complication of acute myocardial infarction (heart attack). In India, about 5–10% of patients hospitalized with a heart attack develop cardiogenic shock. It often occurs at a younger age (around 58 years) compared to Western countries, frequently due to risk factors such as diabetes, smoking, hypertension, and delays in receiving timely medical care. Mortality remains high (35–50%), particularly when treatment is delayed or access to advanced cardiac care is limited. Early interventions like percutaneous coronary intervention (stents), thrombolysis, or mechanical support devices have improved survival rates.

Consult a doctor for cardiogenic shock immediately if there are symptoms suggesting a severe heart problem or reduced blood circulation. Cardiogenic shock is a medical emergency and requires urgent hospital care. Signs that indicate the need for immediate medical attention include:

• Severe or persistent chest pain
• Sudden shortness of breath or rapid breathing
• Cold, clammy, or pale skin
• Rapid, weak pulse
• Confusion, dizziness, or fainting
• Very low blood pressure or extreme weakness

If these symptoms appear, it is best to see a cardiogenic shock doctor for an accurate diagnosis and treatment. People with known heart disease should seek urgent evaluation if symptoms suddenly worsen. Immediate care from a cardiologist or emergency physician can provide the right cardiogenic shock treatment to manage symptoms and reduce long-term risks.