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Cardiogenic shock

Cardiogenic shock

Cardiogenic shock is a medical emergency resulting from inadequate blood flow due to the dysfunction of the ventricles of the heart. [1][2][3][4][5]

There are different types of shock--cardiogenic, hypovolemia, septic, to mention a few. However, none of these are exclusive. Patients can have combined types of shock as well. Shock by definition is inadequate blood circulation to the rest of the body, which causes organ damage. Organs do not have enough oxygen delivery, and cannot adequately maintain their cellular metabolism. Cardiogenic shock is a distinct type because the etiology is from heart dysfunction despite adequate filling pressures. Moreover, there are subsets of cardiogenic shock as well--cardiomyopathic, arrhythmic, mechanical. Cause of CS is diverse, but these are the most common etiologies. CS is most commonly precipitated by acute myocardial infarction. [6]

If allowed to persist, CS can lead to cardiac arrest and ultimately death. That's why it's very important to identify the underlying cause and treat accordingly in a timely fashion. The initial goals of medical therapy is to return blood flow to the body. This can done in a number of ways--fluid resuscitation, blood transfusions, vasopressors, and ionotropes. Selection of therapy depends upon again underlying cause and patient's response to therapy. [7].

Treatment of cardiogenic shock depends on the cause. If cardiogenic shock is due to a heart attack, attempts to open the heart's arteries may help. An intra-aortic balloon pump or left ventricular assist device may improve matters until this can be done. Medications that improve the heart's ability to contract (positive inotropes) may help; however, it is unclear which is best. Norepinephrine may be better if the blood pressure is very low whereas dopamine or dobutamine may be more useful if only slightly low.[8] Cardiogenic shock is a condition that is difficult to fully reverse even with an early diagnosis. With that being said, early initiation of mechanical circulatory support, early percutaneous coronary intervention, inotropes, and heart transplantation may improve outcomes.[9][10][11][12][13]

Presentation of CS often differ from patient to patient. Signs of inadequate blood flow to the body's organs include low urine production (<30 mL/hour), cool arms and legs, and altered level of consciousness. Patient's may also present with severely low blood pressure and heart rate. But the most important markers are used to assess the function of other organs, like the kidney or liver for example. Multi-organ failure is associated with higher rates of mortality. Nonetheless, the mortality rates have been decreasing in the United States. This is likely due to the rapid identification and treatment of the CS. Some studies have suggested that this possibly related to the increased use of coronary reperfusion strategies, like heart stents. Nonetheless, the mortality rates remain high. [14]


Signs and symptoms

  • Anxiety, restlessness, altered mental state due to decreased blood flow to the brain and subsequent hypoxia.
  • Low blood pressure due to decrease in cardiac output.
  • A rapid, weak, thready pulse due to decreased circulation combined with tachycardia.
  • Cool, clammy, and mottled skin (cutis marmorata) due to vasoconstriction and subsequent hypoperfusion of the skin.
  • Distended jugular veins due to increased jugular venous pressure.
  • Oliguria (low urine output) due to inadequate blood flow to the kidneys if the condition persists.
  • Rapid and deeper respirations (hyperventilation) due to sympathetic nervous system stimulation and acidosis.
  • Fatigue due to hyperventilation and hypoxia.
  • Absent pulse in fast and abnormal heart rhythms.
  • 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 abnormal heart rhythms, cardiomyopathy, heart valve problems, ventricular outflow obstruction (i.e. aortic valve stenosis, aortic dissection, cardiac tamponade, constrictive pericarditis, systolic anterior motion (SAM) in hypertrophic cardiomyopathy), or ventriculoseptal defects. It can also be caused by a sudden decompressurization (e.g. in an aircraft), where air bubbles are released into the bloodstream (Henry's law), causing heart failure.[1][2][3][4][5][15][16]

Diagnosis

Electrocardiogram

An electrocardiogram helps establishing the exact diagnosis and guides treatment, it may reveal:

  • Abnormal heart rhythms, such as bradycardia (slowed heart rate)
  • myocardial infarction (ST-elevation MI, STEMI, is usually more dangerous than non-STEMIs; MIs that affect the ventricles are usually more dangerous than those that affect the atria; those affecting the left side of the heart, especially the left ventricle, are usually more dangerous than those affecting the right side, unless that side is severely compromised)
  • Signs of cardiomyopathy

Echocardiography

Echocardiography may show poor ventricular function, signs of PED, rupture of the interventricular septum, 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

When cardiomyopathy is suspected as the cause of cardiogenic shock, a biopsy of heart muscle may be needed to make a definite diagnosis.

Treatment

Depending on the type of cardiogenic shock, treatment involves infusion of fluids, or in shock refractory to fluids, inotropic medications. In case of an abnormal heart rhythm several anti-arrhythmic agents may be administered, e.g. adenosine.

Positive inotropic agents (such as dobutamine or milrinone), which enhance the heart's pumping capabilities, are used to improve the contractility and correct the low blood pressure. Should that not suffice an intra-aortic balloon pump (which reduces workload for the heart, and improves perfusion of the coronary arteries) or a left ventricular assist device (which augments the pump-function of the heart) can be considered.[1][2][3] Finally, as a last resort, if the person is stable enough and otherwise qualifies, heart transplantation, or if not eligible an artificial heart, can be placed. These invasive measures are important tools—more than 50% of patients who do not die immediately due to cardiac arrest from a lethal abnormal heart rhythm and live to reach the hospital (who have usually suffered a severe acute myocardial infarction, which in itself still has a relatively high mortality rate), die within the first 24 hours. The mortality rate for those still living at time of admission who suffer complications (among others, cardiac arrest or further abnormal heart rhythms, heart failure, cardiac tamponade, a ruptured or dissecting aneurysm, or another heart attack) 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.[18]

References

  1. ^ a b c Rippe, James M.; Irwin, Richard S. (2003). Irwin and Rippe's intensive care medicine. Philadelphia: Lippincott Williams & Wilkins. ISBN 978-0-7817-3548-3. OCLC 53868338. [page needed]
  2. ^ a b c Marino, Paul L. (1998). The ICU book. Baltimore: Williams & Wilkins. ISBN 978-0-683-05565-8. OCLC 300112092. [page needed]
  3. ^ a b c Society of Critical Care Medicine. (2001). Fundamental Critical Care Support. Society of Critical Care Medicine. ISBN 978-0-936145-02-0. OCLC 48632566. [page needed]
  4. ^ a b Textbooks of Internal Medicine Harrison's Principles of Internal Medicine 16th Edition, The McGraw-Hill Companies, ISBN 0-07-140235-7Cecil Textbook of Medicine by Lee Goldman, Dennis Ausiello, 22nd Edition (2003), W. B. Saunders Company, ISBN 0-7216-9652-XThe Oxford Textbook of Medicine Edited by David A. Warrell, Timothy M. Cox and John D. Firth with Edward J. Benz, Fourth Edition (2003), Oxford University Press, ISBN 0-19-262922-0
  5. ^ a b Shock: An Overview PDF by Michael L. Cheatham, MD, Ernest F.J. Block, MD, Howard G. Smith, MD, John T. Promes, MD, Surgical Critical Care Service, Department of Surgical Education, Orlando Regional Medical Center Orlando, Florida
  6. ^ [www.uptodate.com]
  7. ^ [mksap17.acponline.org]
  8. ^ Kanter, Joe; Deblieux, Peter (2014). "Pressors and Inotropes". Emergency Medicine Clinics of North America. 32 (4): 823–34. doi:10.1016/j.emc.2014.07.006. PMID 25441037. 
  9. ^ Kataja, Anu; Tarvasmäki, Tuukka; Lassus, Johan; Cardoso, Jose; Mebazaa, Alexandre; Køber, Lars; Sionis, Alessandro; Spinar, Jindrich; Carubelli, Valentina; Banaszewski, Marek; Marino, Rossella; Parissis, John; Nieminen, Markku S.; Harjola, Veli-Pekka (2017). "The association of admission blood glucose level with the clinical picture and prognosis in cardiogenic shock – Results from the Card Shock Study". International Journal of Cardiology. 226: 48–52. doi:10.1016/j.ijcard.2016.10.033. PMID 27788389. 
  10. ^ Basir, Mir B.; Schreiber, Theodore L.; Grines, Cindy L.; Dixon, Simon R.; Moses, Jeffrey W.; Maini, Brijeshwar S.; Khandelwal, Akshay K.; Ohman, E. Magnus; O'Neill, William W. (2017). "Effect of Early Initiation of Mechanical Circulatory Support on Survival in Cardiogenic Shock". The American Journal of Cardiology. 119 (6): 845–851. doi:10.1016/j.amjcard.2016.11.037. PMID 28040188. 
  11. ^ Bagate, François; Lellouche, Nicolas; Lim, Pascal; Moutereau, Stephane; Razazi, Keyvan; Carteaux, Guillaume; De Prost, Nicolas; Dubois-Randé, Jean-Luc; Brun-Buisson, Christian; Mekontso Dessap, Armand (2017). "Prognostic Value of Relative Adrenal Insufficiency During Cardiogenic Shock". SHOCK. 47 (1): 86–92. doi:10.1097/SHK.0000000000000710. PMID 27984534. 
  12. ^ Vergara, Ruben; Valenti, Renato; Migliorini, Angela; Cerisano, Giampaolo; Carrabba, Nazario; Giurlani, Letizia; Antoniucci, David (2017). "A New Risk Score to Predict Long-Term Cardiac Mortality in Patients with Acute Myocardial Infarction Complicated by Cardiogenic Shock and Treated with Primary Percutaneous Intervention". The American Journal of Cardiology. 119 (3): 351–354. doi:10.1016/j.amjcard.2016.10.034. PMID 27884422. 
  13. ^ Sarswat, Nitasha; Hollenberg, Steven M. (2015). "Cardiogenic Shock". Hospital Practice. 38 (1): 74–83. doi:10.3810/hp.2010.02.281. PMID 20469627. 
  14. ^ [www.uptodate.com]
  15. ^ Cardiogenic shock Department of Anaesthesia and Intensive Care of The Chinese University of Hong Kong
  16. ^ Introduction to management of shock for junior ICU trainees and medical students Department of Anaesthesia and Intensive Care of The Chinese University of Hong Kong
  17. ^ a b c "UOTW #7 - Ultrasound of the Week". Ultrasound of the Week. 30 June 2014. Retrieved 27 May 2017. 
  18. ^ Rang and Dale's Pharmacology, H. P. Rang, M. M. Dale, J. M. Ritter, R. J. Flower, Churchhill Livingstone, Elsevier, 6th Edition[page needed]

External links

Classification
External resources