Cardiogenic shock as the most serious complication of MI. How to improve patients’ prognosis?

Cardiogenic shock is usually associated with an extensive damage of the left ventricle connected with myocardial infarction. Frequency of cardiogenic shock in MI ranges from 5% to 10%, but it can also occur as a complication of right ventricular infarction (3% of cases). There are, however, other causes of the shock: valvular dysfunction (12%) or impaired blood flow in e.g. cardiac tamponade.

Shock is a clinical condition of hypoperfusion with significant hypotension (systolic pressure is lower than 90 mmHg) and raised wedge pressure (>20 mmHg) or decreased cardiac index (< 1,8 l/min/m2 ).

Despite the haemodynamic deterioration, state of hypoperfusion results in cold skin, cyanosis, anxiety and oliguria. A diagnosis should be made after excluding other causes of hypotension (hypovolaemia, electrolyte disturbances, vasovagal reaction, influence of medicaments and arrhythmia).

Two-dimensional Doppler echocardiography is the best tool in diagnosing the cardiogenic shock, also the use of the Swan – Ganz catheter can be very helpful. Laboratory tests can show changed parameters.

Shock treatment should be concentrated on decreasing the central filling pressure at least to 15 mmHg and increasing the cardiac index to more than 2l/min/m2. Haemodynamic stabilization can be accomplished by inotropic medications: dopamine in doses higher than 3µg/kg/min and dobutamine (5-20µg/kg/min). Mechanical ventilation and oxygen supply are necessary and should be implemented early.

There is no doubt that the most important for patients survival is causal treatment. Surgery or PCI should be considered in the initial stage of the shock. If it is not possible to perform one of this procedures or if it takes to long to implement it, it is required to include fibrynolytic treatment. The Intra-aortic balloon pump (IABP) is recommended in therapy with LV assist devices.

Cardiogenic shock is almost always a death sentence, especially for patients with MI. 40 to 60% of them will die within 30 days since the shock beginning. Only a third of those patients presents any symptoms of the shock on the admission, while most of them develops the shock state after 6-10 hours. Nevertheless, patients with already developed shock are in the highest risk of death.

Shock appearance is highly probable among patients after myocardial infarction, who are elderly, diabetic, have extensive infarct, haemodynamic disturbances or with a recent history of previous MI. A part of them can be helped by performing PCI revascularization. As results of the Shock Trial Registry show, PCI treatment helps to reduce inhospital mortality from 78% (after symptomatic treatment) to 39% (after PCI). It is also illustrated in data from National Registry of Myocardial Infarction. It is been proved that the mortality among patients with shock is lower in hospitals, where the PCI is a primary method to treat MI. This correlation, however, does not refer to patients at the age of 75 and more. ACC/AHA guidelines recommend, that patients with MI complicated by a shock, ought to be transported to places with an opportunity to perform a revascularization (Class I, Level of Evidence: A). These recommendations concern people under age of 75 and with a shock lasting maximum 18 hours. It should be also taken under consideration when a patient is 75 or elder (Class IIa, Level of Evidence: B).

It is claimed that patients with cardiogenic shock need to be directly reffered to catheterization lab, skipping the emergency ward. As it is shown in Ortolani’s and co. observations, the mortality among patients with shock may be diminished to 60% if they are directly admitted for revascularization without previous visit in community hospital or casualty department. But what if there is no chance to perform revascularization immediately or fast transport to another hospital is impossible? Basing on the WEST evidences (Which Early ST-elevation myocardial infarction therapy) early fibrynolytic therapy with angiographic control and potential angioplasty in the first 24 hours of the shock is comparably effective as primary revascularization.

There are very promising results of the Tayara W. and co. work, who used ECMO and other invasive methods supporting the LV function in treating the shock. These helped to decrease the mortality from 63% to 35%!

Despite the fact that primary revascularization improves patients survival, mortality in the shock state is still very high. It might be caused by intense inflammatory response. People, after MI, with a shock show high level of interleukin 6 concentration on the admission. IL-6 concentration as a factor determining the low effectiveness of classical therapy is not out of question. Considering that fact, treatment with the use of pexelizumab (a monoclonal antibody against component 5 of the complement) could be helpful (COMMA program). During the observation, it was noticed that 90-days mortality in patients after MI, who were administered the highest dose of pexelizumab, drops off.

Most recent reports about the optimal therapy for cardiogenic shock are promising. Patients, who now have 50% chance of survival, may soon see better prospects.

Written by: Kinga Korzonkiewicz

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7.Ortolani P, Marzocchi A, Marrozzini C, et al. Clinical impact of direct referral to primary percutaneous coronary intervention following pre-hospital diagnosis of ST-elevation myocardial infarction. Eur Heart J 2006; 27 (13): 1550-7

Would You like to know more? Watch on Hemodynamic Disorders, Thromboembolic Disease and Shock

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