Cardiogenic Shock

Cardiogenic shock is the result of substantial loss of myocardial function (>40% of left ventricular mass) in 80%, or the development of mechanical complications in 20% of those in whom it occurs (93,94). Historically, cardiogenic shock was associated with an exceedingly poor prognosis, with mortality averaging 70% (94-96). Temporizing measures, such as intra-aortic counterpulsation and inotropic support do not affect survival in the absence of reperfusion. Overall, fibrinolytic agents have not favorably affected the survival in these patients, probably because of poor delivery of the drug to the infarct site. Patients with cardiogenic shock were infrequently enrolled in fibrinolytic trials. In GISSI I (7), 146 and 134 patients with cardiogenic shock (Killip class 4) were randomized to streptokinase and placebo, respectively. The mortality at 21 d was 70% in both groups. In contrast, two other placebo-controlled studies documented a modest mortality reduction in patients assigned to fibrinolysis, as compared to placebo (97,98). In the GISSI II International Study (99) the in-hospital mortality of patients with cardiogenic shock assigned to tPA (80 patients, 100 mg over 3 h) or streptokinase (93 patients) was 78 and 65% (p = 0.04), respectively. In GUSTO I, 315 patients presented in cardiogenic shock and were evenly distributed among the four lytic regimens (100). Patients assigned to streptokinase-based regimens tended to have a lower mortality than those assigned to tPA (51 vs 57%, respectively). In selected patients who underwent rescue angioplasty, the survival was improved (43%) compared to those who did not undergo revascularization (77%). Obviously, patients who did not undergo emergency angiography and revascularization were more likely to be critically ill, than those referred for intervention.

Mechanical reperfusion for patients with cardiogenic shock has been studied extensively in observational series. Among 539 patients in 16 studies (7-81 patients each) (93), the average mortality was 50%. When reperfusion was successful, the fatality rate was only 35%, while failure to restore flow was associated with a mortality of 84%. None of these studies had an adequate control or alternative therapy arm. An international registry (94) prospectively followed 251 patients with cardiogenic shock (8% due to mechanical complications). Among those selected on clinical grounds for emergency angiography and revascularization, the mortality was 51% as compared to 85% in those treated conservatively.

The Should We Emergently Revascularize Occluded Coronaries for Cardiogenc Shock (SHOCK) trial was a randomized trial dedicated to examine the role of immediate revascularization in patients with cardiogenic shock (101). Among 302 patients enrolled, those allocated to early revascularization (angioplasty performed within 1 h of diagnosis in 50%) had a significantly higher survival at 6 mo than those stabilized medically (65 vs 54%, p = 0.04), which was maintained at 1 yr (Fig. 22). Particular benefit was observed among those younger than 75 yr.

Thus, because of the generally unsatisfactory results of fibrinolytic therapy and the potential for improved outcome with mechanical reperfusion, this subset of patients represents an important target for primary angioplasty.

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