Percutaneous mechanical circulatory support versus intra-aortic balloon pump in cardiogenic shock after acute myocardial infarction
Selected in the Journal of the American College of Cardiology by D. Milasinovic
Ouweneel DM, Eriksen E, Sjauw KD, van Dongen IM, Hirsch A, Packer EJ, Vis MM, Wykrzykowska JJ, Koch KT, Baan J, de Winter RJ, Piek JJ, Lagrand WK, de Mol BA, Tijssen JG, Henriques JP
J Am Coll Cardiol. 2017 Jan 24;69(3):278-287
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What is known
Severe cardiogenic shock has been associated with survival rates <50%, in patients with ST-segment myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI). While previous randomized data have not showed mortality benefit of percutaneous circulatory support by intra-aortic balloon counterpulsation (IABP-SHOCK II trial), the Impella platform may open a new window of opportunity, based on direct left ventricular (LV) unloading and cardiac output (CO) augmentation.
Does percutaneously placed Impella CP device reduce mortality over IABP in primary PCI-treated ST-segment elevation MI (STEMI) patients with severe cardiogenic shock?
- 48 patients were randomized to either IABP (n=24) or percutaneous mechanical circulatory support with Impella CP device (n=24), that may increase antegrade flow up to 3.7 l/min.
- Two key inclusion criteria were:
- Severe cardiogenic shock, defined as systolic blood pressure (BP) < 90 mmHg for > 30 minutes or the need for inotropes / vasopressors to maintain systolic BP > 90 mmHg
- Only mechanically ventilated patients were enrolled
- Primary endpoint was 30-day all-cause mortality
- Circulatory support was initiated after revascularization in most patients (except for post-PCI device placement in 3 patients in the IABP and 5 patients in the Impella group) and maintained for median of 48h (IABP) and 49h (Impella).
- Mortality was similar for patients treated with IABP vs. Impella, at both 30 days (50% vs. 46%, p=0.92) and 6 months (50% in both groups).
- Mortality was most frequently attributed to brain damage (46% of the deceased patients) and refractory cardiogenic shock (29%), with similar distribution in patients treated with IABP or Impella.
- Major bleeding was more frequent in patients receiving Impella compared with IABP (33% vs. 8%, respectively).
This randomized study showed no mortality difference between treatment with Impella CP or IABP, in mechanically ventilated STEMI patients with cardiogenic shock, albeit the results should be considered exploratory, due to sample size calculation based on the assumed 30-day mortality reduction from 95% to 60%, which proved to be well above the actually observed 50% mortality rate, thus rendering the analysis underpowered.
There appear to be, however, at least two important sets of findings that may be relevant for the evaluation of mechanical circulatory support in STEMI complicated with cardiogenic shock. First, almost a half of deaths, in the present study, was attributed to brain injury after resuscitation from cardiac arrest, highlighting the limited impact of circulatory support on survival of these patients. In addition, shorter time to return of spontaneous circulation and lower baseline lactate levels were associated with significantly better prognosis, irrespective of the type of circulatory support. Therefore, identification of an appropriate target population may be imperative, in whom the risk of death due to acute heart failure outweighs the risks of post-anoxic brain damage, and who consequently could benefit from acute increase in CO and LV unloading.
Second, although limited by the small sample size, the present study showed numerically lower mortality rates if mechanical circulatory support was started before, rather than after, primary PCI. While the optimal timing of initiating circulatory support remains undefined, early initiation may be important considering potential further heart function deterioration due to reperfusion injury after reopening of the infarct-related artery.
In summary, future trials, advancing mechanical circulatory support in the clinical arena, may have to take into consideration pre-defining an appropriate patient subset and timing of device insertion, in order to build on early observations of increased cardiac index with Impella, as compared with IABP (ISAR-SHOCK trial).
What is the protocol in your institution for the management of primary PCI-treated STEMI patients who develop severe cardiogenic shock?