Author + information
- Published online August 16, 2017.
- Thomas Dahlslett, MD∗ (, )
- Sigve Karlsen, MD,
- Bjørnar Grenne, MD, PhD,
- Benthe Sjøli, MD, PhD,
- Bjørn Bendz, MD, PhD,
- Helge Skulstad, MD, PhD,
- Otto A. Smiseth, MD, PhD,
- Thor Edvardsen, MD, PhD and
- Harald Brunvand, MD, PhD
- ↵∗Department of Medicine, Sørlandet Hospital Arendal, Postbox 783, Stoa, 4809 Arendal, Norway
The intra-aortic balloon pump (IABP) has been the most widely used mechanical device for hemodynamic support in patients with cardiogenic shock complicating acute myocardial infarction (AMI) for more than 40 years. Recently, the use of IABP has been questioned due to limited evidence of clinical value (1). However, selected patients may benefit from IABP and improved methods for patient selection are warranted (2). The cardiomechanical effect of IABP on myocardial function and hemodynamics are mostly studied in experimental and animal models (3,4), but are lacking in humans with cardiogenic shock after AMI. Our aim was to investigate the cardiomechanical and hemodynamic effects of IABP as measured by echocardiographic strain on left ventricular (LV) function in patients with cardiogenic shock after AMI, in order to identify patients who may respond to IABP treatment.
In this 2-center study, 45 patients with cardiogenic shock complicating AMI treated with IABP were included. Echocardiography was performed during IABP counterpulsation (IABP on) and repeated after 5 min of standby position of the IABP (IABP off), with synchronized intra-aortic pressure recordings. Peak systolic strain was measured using speckle-tracking echocardiography. Global longitudinal strain (GLS) and circumferential strain were calculated as average peak systolic strain in a 16-segment LV model. Left ventricular end-diastolic volume, end-systolic volume, stroke volume (SV), and ejection fraction (EF) were calculated using the Simpson biplane method. Patients were classified as IABP-responders if GLS improved (lower values) during IABP counterpulsation compared with during standby. Exclusion criteria were aortic aneurism and/or dissection, severe valvular heart disease, intracardiac shunts as cause of cardiogenic shock, and pregnancy. The study was designed by the authors and approved by the regional ethics committee. A single observer blinded to patient data and state of IABP analyzed the echocardiographic recordings.
The average age was 63 ± 8 years. Culprit artery was the left anterior descending in 33 patients, circumflex in 8 patients, and right coronary artery in 4 patients. Nineteen patients suffered cardiac arrest prior to IABP insertion. Hemodynamic and cardiomechanic data are given in Table 1.
With IABP on, systolic aortic pressures decreased and diastolic aortic pressures increased, but mean aortic pressure did not change significantly. LV volumes decreased during counterpulsation and probably reflect a combined effect of reduced LV afterload due to reduced systolic aortic pressure and improved coronary perfusion due to higher diastolic aortic pressure. GLS, global circumferential strain, and LVEF significantly improved during IABP on, however SV, derived from the Simpson biplane method, did not change significantly. Cardiac output measured as the product of SV (derived from biplane measures) and heart rate was marginally higher during IABP off, mainly driven by a small, but statistically significant change in heart rate.
Analysis of segmental strain demonstrated less systolic longitudinal passive stretch in ischemic segments and improved systolic circumferential strain in nonischemic segments during IABP on.
Thirty patients were classified as IABP-responders and 15 as IABP-non-responders, based on change in GLS. The average baseline LV volumes were significantly smaller among the IABP-responders compared with non-responders, end-diastolic volume 136 ml versus 178 ml and end-systolic volume 90 ml versus 124 ml, p < 0.05 for both. The average change in mean aortic diastolic pressure during IABP counterpulsation was significantly larger among IABP-responders (10 mm Hg) than among nonresponders (5 mm Hg), p < 0.05. There were no significant differences between responders and nonresponders with respect to baseline LVEF, change in SV, mean aortic pressure, or mean aortic systolic pressure, peak augmentation pressure, or balloon size.
To conclude, in patients with cardiogenic shock complicating AMI, IABP reduced LV volumes and improved global LV function by reducing passive myocardial stretch and by increasing circumferential contraction in nonischemic segments. These cardiomechanical responses to IABP can be monitored bedside by use of strain echocardiography and may be a useful method to verify positive cardiomechanical response to IABP with potential clinical benefit. The results are consistent with earlier studies from animal models and suggest a small, but favorable cardiomechanical response to treatment with IABP counterpulastion in selected patients with cardiogenic shock complicating AMI (3,4).
Please note: This study was funded by Norwegian Health Association, South-Eastern Norway Regional Health Authority, and Sørlandet Hospital, Arendal, Norway. The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2017 American College of Cardiology Foundation
- Zeymer U.,
- Thiele H.
- Kerber R.E.,
- Marcus M.L.,
- Ehrhardt J.,
- Abboud F.M.