Increased Coronary Blood Flow and Cardiac Contractile Efficiency With Intraaortic Balloon Counterpulsation in a Porcine Model of Myocardial Ischemia-Reperfusion Injury

Superior mesenteric and renal flow patterns during intra-aortic counterpulsation

NEW FINDINGS

What is the central question of this study? Visceral ischaemia is one of the most feared complications during use of an intra-aortic balloon pump. Using an animal model, we measured the flows at the abdominal level directly and examined flow patterns to enable investigation of flow patterns during the use of the intra-aortic balloon pump. What is the main finding and its importance? We show that there is a significant balloon-related reduction in superior mesenteric flow in both early and mid-diastole.

ABSTRACT

A number of previous studies have shown that blood flow in the visceral arteries is altered during intra-aortic balloon pump (IABP) treatment. We used a porcine model to analyse the pattern of blood flow into the visceral arteries during IABP use. For this purpose, we measured the superior mesenteric, right renal and left renal flows before and during IABP support, using surgically placed flowmeters surrounding these visceral arteries. The superior mesenteric flow significantly decreased in early diastole (P < 0.001) and in mid-diastole (P = 0.003 versus early diastole), whereas in late diastole it increased again (P < 0.001 versus mid-diastole). During systole, the flow was not significantly increased compared with late diastole (P = 0.51), but it was significantly lower than at baseline (both P < 0.001). Flows did not differ between right and left kidneys. Perfusion of either kidney did not change significantly in early diastole (P > 0.05), whereas it decreased significantly in mid-diastole (P < 0.001), rising dramatically in late diastole (P < 0.001) and with an additional slight increase in systole (P = 0.054). This study provides important insights into abdominal flows during intra-aortic pump counterpulsation. Furthermore, it supports the need to rethink the balloon design to avoid visceral ischaemia during circulatory assistance.

Prophylactic intra-aortic balloon counterpulsation before surgical myocardial revascularization in patients with acute myocardial infarction

Introduction:

Prophylactic intra-aortic balloon counterpulsation (pIABC) is recommended for high-risk patients undergoing coronary artery bypass grafting (CABG) surgery. Criteria for high-risk patients benefiting from pIABC are unclear. This study aimed to specifically describe the effect of pIABC on outcomes of patients with acute myocardial infarction (AMI) undergoing CABG.

Methods:

In 178 of 484 AMI patients (non-ST-segment elevation myocardial infarction [NSTEMI] or ST-segment elevation myocardial infarction [STEMI] ≤5 days before surgery) without cardiogenic shock who underwent CABG between 2008 and 2013, pIABC was initiated preoperatively. After propensity score matching, the outcomes of 400 patients were analyzed (pIABC: 150; Control: 250).

Results:

After propensity score matching, baseline and operative characteristics were balanced between the groups except for a higher rate of patients with a left ventricular ejection fraction (LVEF)≤30% in the pIABC group (26% vs. Control: 13%; p=0.032). Seven point two percent (7.2%) of the control patients received an IABP intraoperatively or postoperatively. Postoperative extracorporeal life support (ECLS) was only needed in the control group (1.2% vs. 0%; p=0.01). Postoperative plasma curves of troponin I, creatine kinase (CK) and creatine kinase isoform MB (CK-MB) levels were reduced in the pIABC group compared with the control group. In-hospital mortality was reduced in the pIABC group (3.3% vs. control: 6.4%; p=0.18). After multivariate adjustment for other preoperative risk factors, pIABC was significantly protective concerning in-hospital mortality (HR 0.56; 95%-CI 0.023-0.74; p=0.021). Mortality (pIABC vs. control) was more affected in patients with preoperative LVEF≤30% (2/36 (5.6%) vs. 6/31 (19%); heart rate (HR) 0.25; 95%-CI 0.046-1.3; p=0.13) compared with LVEF>30% (3/114 (2.6%) vs. 10/219 (4.6%); HR 0.56; 95%-CI 0.15-2.1; p=0.55). Long-term survival did not differ between the groups.

Conclusions:

pIABC in CABG for AMI is associated with reduced perioperative cardiac injury and in-hospital mortality. Long-term survival is not affected.

A New 35-mm Short Intra-aortic Balloon Catheter: A Suitable Option Also for Non-Small-Sized Patients?

OBJECTIVE

Visceral ischemia can be a potentially life-threatening complication of intra-aortic balloon pump (IABP) support. A shorter IABP catheter might lead to a reduction of visceral complications. In this animal study, we evaluate the effects of a 35-mL short catheter in comparison with a 40-mL standard-sized catheter.

METHODS

Eighteen healthy swine underwent 120-minute ligation of the left anterior descending coronary artery followed by 6 hours of reperfusion being supported by either a short IABP catheter (short group) (n = 6) or a long IABP catheter (long group) (n = 6) or with no assistance (controls) (n = 6). Hemodynamics, visceral and coronary flows, as well as biochemical markers were evaluated throughout the different phases of the protocol.

RESULTS

Mesenteric flows increased significantly at reperfusion (P < 0.001 both) remaining constant afterward (all, P > 0.05) in the short group, while remaining significantly lower in the long group at the start of reperfusion, remaining constantly lower than the short group and controls (P < 0.001 vs short, P < 0.003 vs controls). In both long and short groups, catheters improved renal flows at reperfusion (P < 0.001 both) without any further variation (P > 0.05). In the short group, the flows were higher during the whole of reperfusion (all, P < 0.05). Intra-aortic balloon pump support improved hemodynamic indices and coronary blood flows during reperfusion to a similar extent in both the small and the long group (P > 0.05).

CONCLUSIONS

The short IABP catheter proved to be as effective as the standard-sized catheter in supporting hemodynamics and coronary circulation. Furthermore, it even improves visceral flows in comparison with conventional IABP catheters.

Is visceral flow during intra-aortic balloon pumping size or volume dependent?

AIM

We evaluated the influence of intra-aortic balloon size and volume on mesenteric and renal flows.

METHODS

Thirty healthy swine underwent 120-minute ligation of the left anterior descending coronary artery followed by 6 hours of reperfusion. Then, they were randomly assigned to the following five groups of animals, with six animals in each group: no intra-aortic balloon pump (IABP), a short 35-mL IABP, a short 40-mL IABP, a long 35-mL IABP and a long 40-mL IABP. Superior mesenteric artery (SMA) and renal flows were measured at baseline (t₀), at 2-hour ischemia (t₁) and every hour thereafter until 6 hours of reperfusion (from t_R1 to t_R6).

RESULTS

SMA flows increased significantly at t_R1 only in the two short IABP groups (p<0.001) and balloon volume did not appear to affect flows which, at any experimental time-point, were comparable using 35 mL or 40 mL balloons (p>0.05). Renal flows appeared to be influenced by balloon length, but not by volume. Indeed, flows in the renal arteries rose during IABP treatment; the increase was significantly higher in the short balloon groups and throughout the whole reperfusion (all, p<0.001).

CONCLUSIONS

Changes in visceral perfusion during IABP assistance were significantly related to balloon length, but not to its volume. This could be relevant for the evolution of balloon engineering design in order to reduce the incidence of mesenteric ischemia following IABP. Further research is necessary to confirm these findings.

Comparing short versus standard-length balloon for intra-aortic counterpulsation: results from a porcine model of myocardial ischaemia-reperfusion

OBJECTIVES

We compare a short and a standard-size balloon with same filling volumes to verify the differences in terms of visceral flow, coronary circulation and haemodynamic performance during aortic counterpulsation in an animal model of myocardial ischaemia-reperfusion injury.

METHODS

Eighteen healthy pigs underwent 120-min ligation of the left anterior descending coronary artery followed by 6 h of reperfusion, and they were randomly assigned to have intra-aortic balloon counterpulsation (IABP) with a 40-ml short-balloon (n = 6) or a 40-ml standard-length balloon (n = 6), or to undergo no IABP implantation (controls, n = 6). Haemodynamics and visceral and coronary flows were measured at baseline (t0), at 2 h of ischaemia (t1) and every hour thereafter until 6 h of reperfusion (from tR1 to tR6), respectively.

RESULTS

Mesenteric flows increased significantly at tR1 only in the short-balloon group (P < 0.001) and it was constantly higher than in the standard-balloon group regardless of mean arterial pressure, systemic vascular resistance and cardiac output (CO; all, P < 0.001). Renal blood flows were significantly increased during IABP treatment with values constantly and significantly higher in short balloons at any following experimental step (all, P < 0.05). IABP improved CO and coronary blood flow, and reduced afterload, myocardial resistances and myocardial oxygen consumption without differences between the short and the standard-length balloon (all, P > 0.05).

CONCLUSIONS

The short balloon prevents visceral ischaemia and, compared with the standard-size balloon, it does not lose IABP beneficial cardiac and coronary-related effects. Further studies are warranted to confirm our findings.