Multifactorial approach necessary in treating cardiogenic shock
Effective treatment of cardiogenic shock requires a multifactorial approach, according to an expert at the recent ASEAN Federation of Cardiology Congress (AFCC 2018).
There are several areas for treatment of cardiogenic shock which are dependent on patient factors, said Professor Tan Huay Cheem from the National University of Singapore. For instance, for a patient with left ventricular dysfunction, inotropes may be suitable, while patients with coronary occlusion will benefit from revascularization.
Revascularization as primary treatment
“There is only one treatment that really makes a difference to the patient’s outcome and that is revascularization. Early revascularization is the primary therapeutic goal,” said Tan.
In the SHOCK trial which involved patients with shock caused by left ventricular failure complicating myocardial infarction (MI) who received either emergency revascularization (≤6 hours) or initial medical stabilization, all-cause mortality at 30 days was comparable between groups (46.7 percent vs 56.0 percent; p=0.11). However, patients who underwent revascularization had a significantly lower mortality rate at 6 months post-procedure compared with those who received medical therapy (50.3 percent vs 63.1 percent; p=0.027). [N Engl J Med 1999;341:625-634]
The SHOCK trial also demonstrated the likelihood of poor prognosis among patients aged ≥75 years, regardless of therapy received. Revascularization conferred significant mortality benefit to patients aged <75 years compared with medical therapy (41.4 percent vs 56.8 percent; p=0.02 and 44.9 percent vs 65.0 percent; p=0.02 at 30 days and 6 months, respectively), said Tan. In contrast, patients ≥75 years who underwent revascularization had higher mortality rates than those who received medical therapy, though the findings were not significant (75.0 percent vs 53.1 percent; p=0.16 and 79.2 percent vs 56.3 percent; p=0.09 at 30 days and 6 months, respectively).
In the CULPRIT-SHOCK trial, emergency percutaneous coronary intervention (PCI) of the culprit lesion only in patients with multivessel disease, acute MI, and cardiogenic shock led to lower 30-day mortality risk compared with patients who underwent multivessel PCI (relative risk, 0.84; p=0.03). [N Engl J Med 2017;377:2419-2432]
According to Tan, in-hospital mortality was not affected by a reduction in door-to-balloon time among patients with cardiogenic shock undergoing primary PCI for ST-segment elevation MI (STEMI). [N Engl J Med 2013;369:901-909]
“What I think is more important is the ischaemia-to-balloon time for patients with cardiogenic shock,” he said.
The role of inotropes
The SOAP II study showed that patients who received first-line dopamine or norepinephrine had similar outcomes with regard to 28-day mortality (52.5 percent vs 48.5 percent; p=0.10), although a higher rate of arrhythmic events occurred among patients who received dopamine (24.1 percent vs 12.4 percent; p<0.001). [N Engl J Med 2010;362:779-789]
With regard to inotropes in patients with cardiogenic shock, the more inotropes you use, the higher the mortality, said Tan. [J Card Surg 1999;14:288-293]
The haemodynamic benefits conferred by inotropes are counteracted by adverse effects which include an increase in myocardial oxygen demand when there is tachycardia, impairment of coronary artery microcirculation, and increased arrhythmogenicity, he said.
The pros and cons of mechanical support devices
There are four mechanical circulatory support (MCS) systems currently available – the intra-aortic balloon pump (IABP), the Impella and TandemHeart devices, and the veno-arterial extra-corporeal membrane oxygenation (VA-ECMO) system, said Tan.
In the IABP-SHOCK II trial, patients who received IABP had comparable survival as those who did not receive IABP at 30 days (39.7 percent vs 41.3 percent; p=0.69) and at 12 months (52 percent vs 51 percent; p=0.91). [N Engl J Med 2012;367:1287-1296; Lancet 2013;382:1638-1645]
The use of IABP did not change haemodynamics, survival, or arterial lactate, said Tan. However, the ACC/AHA* guidelines state that IABP can still be useful for patients with cardiogenic shock after STEMI who do not quickly stabilize following pharmacological therapy.
The Impella device seems to be a suitable option from a haemodynamic perspective, said Tan. [J Am Coll Cardiol 2008;52:1584-1588] However, 30-day survival was comparable between Impella and IABP (46 percent vs 50 percent; p=0.92). [J Am Coll Cardiol 2017;69:278-287]
A trial comparing short-term active MCS (Impella and TandemHeart) vs IABP in cardiogenic shock demonstrated an increase in mean arterial pressure and a decrease in arterial lactate, as well as an increased risk of bleeding among patients on MCS. [Eur Heart J 2017;38:3523-3531]
The increased afterload which occurs with VA-ECMO presents a problem, with the increase in coronary flow offset by the increase in wall tension. The result is a device that is good for systemic flow but provides a poor environment for heart recovery, said Tan. Therefore, VA-ECMO must be combined with an afterload reductor.
According to Tan, selection of the appropriate device may depend on shock stage. In the pre-shock stage, IABP could work well. Once the patient is in shock, the Impella device is necessary, and in severe shock, the combination of ECMO and an afterload reductor will be necessary.
“The potential benefits of MCS devices should be balanced by the potential risks of complications and high cost,” he said. “Randomized controlled trials assessing the efficacy and safety of MCS in cardiogenic shock complicating acute MI are needed.”
“Cardiogenic shock remains a major cause of death following acute MI … the reason why we’re not saving 100 percent of our patients with STEMI is because of cardiogenic shock,” said Tan. It affects approximately 7–10 percent of patients with acute MI and is associated with poor prognosis, with a mortality rate of about 50 percent, about half of which occur within 48 hours of presentation.
Treatment of cardiogenic shock must include rapid identification and triage, early consultation with an interventional cardiologist, initiation of mechanical support, optimal PCI of the culprit lesion, systematic use of right heart catheterization, use of haemodynamics to de-escalate vasopressor and inotrope use and maintain or escalate MCS levels, involvement of a multidisciplinary heart team, and optimal care in the cardiac intensive care unit, concluded Tan.