American Heart Journal
Volume 147, Issue 6 , Pages 950-952, June 2004

Which elderly patients with cardiogenic shock should be treated with percutaneous coronary intervention?

  • John K French, MB, PhD, FACC

      Affiliations

    • Green Lane Hospital, Auckland, New Zealand
    • Corresponding Author InformationReprint requests: John French, MB, PhD, Department of Cardiology, Liverpool Health Service, Locked Bag 7103, Liverpool NSW 1871, Australia.

Article Outline

 

See related article on page 1066.

Since the advent of coronary revascularization procedures, their use in elderly patients has been limited to carefully selected patients. For instance, coronary artery bypass grafting (CABG) was initially performed only rarely in patients ≥75 years of age.1 Since the 1960s, the life expectancy of individuals of both sexes has increased by at least 5 years in most countries with developed healthcare systems,2 and thus the number of elderly patients who may be candidates for coronary revascularization procedures has increased dramatically.3, 4

Longitudinal data collected since the 1970s from Worcester, Mass, suggest that patients aged ≥75 years now account for 40% of all admissions with acute myocardial infarction (AMI)5 and that most deaths in this age group are caused by left ventricular (pump) failure, including cardiogenic shock.5 Thus, if trial data were to support early use of revascularization procedures in elderly patients with cardiogenic shock, a significant proportion of patients with AMI who are ≥75 years old might become candidates for these procedures. The largest clinical trial addressing this issue, the Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock (SHOCK) trial,6 which enrolled patients from 1993 to 1998, included a pre-specified analysis of the effect of age on mortality after emergency revascularization as compared with initial medical stabilization. Only 56 patients aged ≥75 years were enrolled, and of the 28 patients who were randomized to undergo emergency revascularization, only 12 underwent percutaneous coronary intervention (PCI). Because of these small numbers, no conclusions could be drawn about the possible benefit of emergency PCI in this age group.

In this issue of the Journal, Prasad et al7 describe 60 patients with AMI who were aged ≥75 years and had cardiogenic shock who were treated with PCI at the Mayo Clinic in Rochester, Minn, between 1991 and 2000. The 30-day mortality rate in this group was 47%. These data are likely to represent the results of highly selected patient referrals from the total number of elderly patients presenting with AMI to various hospitals in the surrounding counties. It is likely that many other patients had comorbidities that their physicians judged would preclude transfer. The proportion of these patients is not known. However, in the Trial of Invasive Versus Medical Therapy in Elderly Patients (TIME),3 which randomized elderly patients (mean age, 80 years) with symptomatic coronary artery disease, 20% of patients had peripheral vascular disease, 12% had renal insufficiency, and 28% had other comorbidities.

Prasad et al report a procedural success rate (defined as <50% stenosis) of 91% in all treated arteries, and Thrombolysis in Myocardial Infarction (TIMI) grade 2 or 3 flow was achieved in 84%. The success rates for the presumed culprit artery are not detailed. Glycoprotein IIb/IIIa receptor antagonists were used in 43% of interventions, and stents were deployed in 48%.7 These treatments are known to improve procedural and late outcomes8 and are now used more routinely than they were when the study began; thus, one would expect procedural success rates in current practice to be even higher. The overall rate of intra-aortic balloon pump (IABP) deployment was relatively low, 39%. Whether routine IABP deployment improves survival rates in this elderly patient population is not known. There has only been 1 randomized trial of early IABP deployment in patients with AMI in “pre-shock” or cardiogenic shock who were treated with fibrinolysis.9 This trial was terminated early because of lack of recruitment, but the interim results did show that the mortality rate was reduced (39% vs 80%, P = .05) in patients with shock who were randomized to receive IABPs.9

The 47% mortality rate reported from the Mayo Clinic database7 is similar to the 45% inhospital mortality rate of elderly patients with AMI who underwent revascularization procedures in the SHOCK trial registry.10 The procedural success rate in the SHOCK trial registry was 86%, although only 81% of patients achieved TIMI grade 2 or 3 flow in the culprit artery.

To date, the largest published cohort of elderly patients with AMI undergoing PCI for cardiogenic shock has come from the Arbeitsgemeinschaft Leitende Kardiologische Krankenhausärzte (ALKK) primary PCI registry for the period from 1994 to 2000.11 In that series, patients aged >75 years (n = 260) had an inhospital mortality rate of 63%, whereas the overall mortality rate of the entire cohort was 46%. The reasons why the mortality rate in the ALKK registry11 was approximately 15% higher than that in the contemporary SHOCK trial registry10 and Mayo Clinic database7 may include differences in patient selection, differences in the numbers of patients with serious comorbidities, and possible international differences in the use of various medical therapies.

Many elderly patients have 3-vessel coronary artery disease or left main stenosis, and in these cases, CABG is usually the most suitable treatment option. It has not yet been determined whether a strategy of culprit-vessel angioplasty followed by CABG is appropriate in elderly patients with AMI who have cardiogenic shock, and there are no reliable estimates of the mortality rate associated with CABG in these circumstances.

It has been shown that the blood levels of several circulating markers of inflammation become elevated during AMI, particularly when it is accompanied by cardiogenic shock.12 Although myocardial inflammation is a normal part of the repair process, deleterious effects such as oxygen radical damage, and elevation in myocyte cytosolic calcium levels may occur. Some of these deleterious inflammatory effects may be ameliorated by the use of cardioprotective agents such as adenosine, the nitric oxide synthase inhibitor, NG-monomethyl L-arginine (L-NMMA); both of these agents increase circulating nitric oxide levels.

The use of L-NMMA for cardioprotection in patients with persistent cardiogenic shock after PCI was evaluated by Cotter et al in a small study (n = 30) with no age restriction.13 Patients randomized to receive L-NMMA had a 30-day mortality rate of 27%, compared with 67% in control patients receiving supportive care alone (P = .03).13 L-NMMA is currently being evaluated in a larger group of patients in the pilot study for the proposed SHOCK-2 trial.

In the report by Prasad et al, only 12% of patients received fibrinolytic therapy before PCI. On the basis of the improvement in 1-year survival rate seen in all patients randomized in the SHOCK trial, 56% of whom received fibrinolytic therapy, the treatment strategy currently preferred in patients with AMI who have cardiogenic shock is emergency angiography (when available) followed by PCI or surgery.6 It has not yet been determined how best to treat patients (including the elderly) when emergency PCI is not available. For instance, some clinical trials (conducted at hospitals without onsite PCI capacity) comparing fibrinolysis with interhospital transfer for PCI have reported very low rates of PCI (including rescue PCI) in patients randomized to undergo fibrinolysis.14, 15, 16 Other trials have reported very short “door-to-balloon” times in patients randomized to undergo primary PCI,17, 18 whereas door-to-balloon times in routine practice can often exceed 90 minutes.19 In the Comparison of Angioplasty and Prehospital Thrombolysis in Acute Myocardial Infarction (CAPTIM) trial,17 there was a trend toward a better clinical outcome in patients with AMI who came to the hospital within the first few hours after symptom onset and received pre-hospital fibrinolysis followed by high rates of rescue PCI and revascularization procedures during their initial hospital admission. Indeed, patients randomized to undergo prehospital fibrinolysis had a lower incidence of cardiogenic shock than patients randomized to undergo primary PCI (1.3% vs 5.2%, P = .032). In patients randomized to undergo initial medical stabilization in the SHOCK trial, patients who received (nonrandomized) fibrinolysis had a higher 1-year survival rate than patients who did not (adjusted mortality hazard ratio, 0.62; 95% CI, 0.41–0.93; P = .02).20 Thus, in AMI patients (including the elderly) with cardiogenic shock, fibrinolysis should be considered when PCI is not immediately available. The best choice of fibrinolytic agent for this age group has not been demonstrated by adequately powered clinical trials, although there are concerns about higher rates of bleeding with more fibrin-specific drugs as compared with streptokinase.21, 22, 23

In conclusion, the use of early PCI in selected elderly patients with AMI who have cardiogenic shock is supported by the Mayo Clinic database7 and the SHOCK trial registry,10 both of which have reported 30-day mortality rates <50% in such patients. Pharmacological treatment regimens are continually being refined for use in elderly patients, including those in combination with mechanical treatment strategies. However, the under-representation of elderly patients in clinical trials means that there is currently a paucity of data (especially with mortality end points) on which to base recommendations for their treatment. Because of the high mortality rate in this age group, it is important that future trials are adequately powered to address these issues. Furthermore, because there are no firm guidelines on the selection of elderly patients for revascularization procedures—and because of the high mortality rate observed after primary PCI in the ALKK registry—one must exercise caution in predicting the likely risk or benefit of PCI in less selected elderly patients with AMI who have cardiogenic shock coming in particular to community hospitals, but also directly to tertiary cardiac referral centers.

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PII: S0002-8703(04)00020-1

doi:10.1016/j.ahj.2003.12.026

American Heart Journal
Volume 147, Issue 6 , Pages 950-952, June 2004

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