Definition, etiology, pathogenesis Top
Cardiogenic shock is shock due to a dysfunction of the heart (see Acute Heart Failure) that leads to reduced cardiac output. Causes:
1) Myocardial injury: Acute systolic heart failure caused by acute coronary syndrome (ACS) (most commonly myocardial infarction [MI], usually ST-elevation myocardial infarction with >40% decrease in left ventricular [LV] function) and its complications (acute mitral insufficiency, free wall rupture, ventricular septal defect), myocarditis, cardiac injury (trauma), cardiomyopathies, exacerbation of or end-stage chronic heart failure.
2) Cardiac arrhythmias: Bradycardia, tachyarrhythmias (particularly ventricular tachycardia and atrial fibrillation).
3) Acute valvular heart disease (acute mitral or aortic regurgitation), prosthetic valve dysfunction.
Traditionally, the term “cardiogenic shock” has denoted a shock caused by impaired cardiac contractility (pump function).
Clinical features and diagnosis Top
Symptoms of shock and of the underlying disease are seen.
The use of the following methods of treatment depends on the specific underlying pathophysiology.
1. Discontinue beta-blockers, angiotensin-converting enzyme inhibitors, and other drugs that may lower blood pressures unless used specifically to counteract the mechanism of shock (for example, a beta-blocker with mitral stenosis and very rapid atrial fibrillation).
2. In the case of ventricular tachycardia, atrial fibrillation, or atrial flutter (or other supraventricular tachycardia causing shock), perform cardioversion. Consider subsequent administration of medications to prevent or treat arrhythmia recurrence (see Cardiac Arrhythmias).
3. In patients with bradycardia, consider atropine (see Figure 3.8-2), chronotropic agents (such as epinephrine 2-10 microg/min in a continuous IV infusion; alternatively isoproterenol [INN isoprenaline] 5 microg/min or dopamine), or cardiac pacing (see Cardiac Arrest).
4. In patients without symptoms of volume overload and pulmonary congestion, initiate fluid resuscitation to achieve optimal LV filling (this is particularly important in right ventricular dysfunction). Start with 250 mL of a crystalloid over 10 to 15 minutes, continue fluid resuscitation, and make adjustments based on the response to treatment and appearance of the volume overload. In patients with volume overload (pulmonary congestion) and patients without volume overload who do not respond to fluid therapy, consider one of the treatment interventions discussed below.
5. In patients with documented myocardial dysfunction, an inotropic agent may be beneficial. For most patients, starting with norepinephrine is reasonableEvidence 1Strong recommendation (benefits clearly outweigh downsides; right action for all or almost all patients). High Quality of Evidence (high confidence that we know true effects of intervention). De Backer D, Aldecoa C, Njimi H, Vincent JL. Dopamine versus norepinephrine in the treatment of septic shock: a meta-analysis*. Crit Care Med. 2012 Mar;40(3):725-30. doi: 10.1097/CCM.0b013e31823778ee. PubMed PMID: 22036860. Levy B, Perez P, Perny J, Thivilier C, Gerard A. Comparison of norepinephrine-dobutamine to epinephrine for hemodynamics, lactate metabolism, and organ function variables in cardiogenic shock. A prospective, randomized pilot study. Crit Care Med. 2011 Mar;39(3):450-5. doi: 10.1097/CCM.0b013e3181ffe0eb. PubMed PMID: 21037469. De Backer D, Biston P, Devriendt J, et al; SOAP II Investigators. Comparison of dopamine and norepinephrine in the treatment of shock. N Engl J Med. 2010 Mar 4;362(9):779-89. doi: 10.1056/NEJMoa0907118. PubMed PMID: 20200382. as its pharmacologic effects include not only vasoconstriction but also some inotropy (via beta2 stimulation). In patients with ongoing signs of shock despite initial therapy, dopamine or dobutamine can be administered via a continuous IV infusion. In case of unsatisfactory response or issues with significant arrhythmias, consider the use of milrinone, enoximone, or levosimendan (dosage: see Acute Heart Failure; all of these drugs may have serious adverse effects and their use is controversial).
6. In patients with pulmonary congestion in whom blood pressure has been raised to a physiologically adequate level (usually at least 90 mm Hg) without catecholamine support, you may consider a loop diuretic (see Acute Heart Failure). In patients in whom the diuretic treatment is ineffective, consider ultrafiltration. In patients with renal failure, consider hemodialysis.
7. In patients with pulmonary congestion and SBP >110 mm Hg, consider a vasodilator, usually nitroglycerin (dosage: see Acute Heart Failure; these should not be used in isolated right ventricular failure).
8. Treatment of the underlying condition. In the case of ACS, refer the patient for urgent invasive revascularization (see Acute Coronary Syndromes). In the case of mechanical complications of MI, acute valvular disease, or prosthetic valve dysfunction, refer the patient for cardiac surgery.
9. If the cause of shock is reversible (ACS, myocarditis), specialized centers may consider intra-aortic counterpulsation (after excluding contraindications: aortic regurgitation, aortic dissection) or ventricular support devices as interim measures (until surgery or recovery).
10. Other management steps (including oxygen therapy): As in the other forms of shock.