Cardiogenic shock is based upon an inadequate circulation of blood due to primary failure
of the ventricles of the heart to function effectively.
As this is a type of circulatory shock there is insufficient perfusion of tissue to meet
the required demands for oxygen and nutrients.
Cardiogenic shock is a largely irreversible condition and as such is more often fatal
than not.
The condition involves increasingly more pervasive cell death from oxygen starvation and nutrient
starvation.
Because of this it may lead to cardiac arrest which is an acute cessation of cardiac pump
function.
Cardiogenic shock is defined by sustained hypotension with tissue hypoperfusion despite
adequate left ventricular filling pressure.
Signs of tissue hypoperfusion include oliguria, cool extremities, and altered level of consciousness.
Signs and symptoms Anxiety, restlessness, altered mental state
due to decreased cerebral perfusion and subsequent hypoxia.
Hypotension due to decrease in cardiac output.
A rapid, weak, thready pulse due to decreased circulation combined with tachycardia.
Cool, clammy, and mottled skin, due to vasoconstriction and subsequent hypoperfusion of the skin.
Distended jugular veins due to increased jugular venous pressure.
Oliguria due to insufficient renal perfusion if condition persists.
Rapid and deeper respirations due to sympathetic nervous system stimulation and acidosis.
Fatigue due to hyperventilation and hypoxia.
Absent pulse in tachyarrhythmia.
Pulmonary edema, involving fluid back-up in the lungs due to insufficient pumping of the
heart.
Causes Cardiogenic shock is caused by the failure
of the heart to pump effectively.
It can be due to damage to the heart muscle, most often from a large myocardial infarction.
Other causes include arrhythmia, cardiomyopathy, cardiac valve problems, ventricular outflow
obstruction in hypertrophic cardiomyopathy) or ventriculoseptal defects.
It can also be caused by a sudden decompressurization, where air bubbles are released into the bloodstream,
causing heartfailure.
Diagnosis Electrocardiogram
An electrocardiogram helps establishing the exact diagnosis and guides treatment, it may
reveal: Cardiac arrhythmias
myocardial infarction Signs of cardiomyopathy
Ultrasound Echocardiography may show poor ventricular
function, signs of PED, ventricular septal rupture, an obstructed outflow tract or cardiomyopathy.
Swan-ganz catheter The Swan-ganz catheter or pulmonary artery
catheter may assist in the diagnosis by providing information on the hemodynamics.
Biopsy In case of suspected cardiomyopathy a biopsy
of heart muscle may be needed to make a definite diagnosis.
but biopsy should only be done when third space is suspected
Treatment In cardiogenic shock, depending on the type
of myocardial infarction, treatment involves infusion of fluids, or in shock refractory
to fluids, inotropic medications.
In case of cardiac arrhythmia several anti-arrhythmic agents may be administered, i.e. adenosine,
verapamil, amiodarone, β-blocker or glucagon.
Positive inotropic agents, which enhance the heart's pumping capabilities, are used to
improve the contractility and correct the hypotension.
Should that not suffice an intra-aortic balloon pump can be considered or a left ventricular
assist device.
Finally, as a last resort, if the patient can be made stable enough and otherwise qualifies,
cardiac transplantation can be performed.
These invasive measures are important tools- more than 50% of patients who do not die immediately
due to cardiac arrest from a lethal arrthythmia and live to reach the hospital, die within
the first 24 hours.
The mortality rate for those still living at time of admission who suffer complications
from cardiogenic shock is even worse around 85%, especially without drastic measures such
as ventricular assist devices or transplantation.
Cardiogenic shock may be treated with intravenous dobutamine, which acts on β1 receptors of
the heart leading to increased contractility and heart rate.
References
External links Cardiogenic Shock by eMedicine