*Coronary Artery Bypass Grafting in High-Risk Patients: On-Pump Beating-Heart CABG DOI: http://dx.doi.org/10.5772/intechopen.115054*

anastomosis are quite different. The OPBHC could lead to a proximal anastomosis in a "softer" aortic lateral clamping due to rapid on-demand hypotension achieved by CPB, while in off-pump CABG, the same procedure leads to a more traumatic side-clamping.

Also, considering short-term outcomes, recent studies are pointing out that a reduced risk of mortality of OPBHC is performed in selected patients (with high preoperative risk) [7, 25], while previous findings in unselected patients might have diluted the benefits [26].

Based on these results, OPBHC was shown to be associated with reduced postoperative mortality and complications (mainly driven by reduced stroke and reduced myocardial infarction) than conventional revascularization and might be suggested as a valid alternative in high-risk patients. However, considering the significant differences in inclusion criteria, future work should focus on registries and multicenter RCTs to definitely assess the benefits of OPBHC.

### **4. Gaps in evidence**

Although several studies have been done on the OPBHC, there are still several aspects to be analyzed in order to have a clear overview of the benefits and implications of using it.

One aspect that would need to be further investigated is the optimal level of perfusion pressure during OPBHC. A low level of perfusion pressure might increase the risk of hypoperfusion in the distal and subendocardial territories, as low perfusion pressure might lead to flow competition and insufficient native coronary artery blood flow. Evidence from metanalysis [1, 6, 7, 24] suggests that a mean pressure between 70 and 80 mmHg could be an optimal level but due to few observations within the sample, more studies should be performed on this topic.

Another risk for patients undergoing an OPBHC is manipulation-induced aortic insufficiency. In fact, the hemodynamic stability of the patient could be affected by an excessive acute aortic regurgitation when the blood flow comes from the aortic cannula. Further investigations on this risk are needed to better assess the OPBHC technique.

In emergency situations, surgeons usually prefer to use vein grafts rather than arterial conduits as this procedure is faster and less complex. However, the use of vein grafts could affect the long-term outcomes of CABG. Hence, more studies should evaluate if long-term outcomes are affected by the type of graft conduits used (vein or arterial) in the OPBHC setting, as several published researches have been conducted for conventional on-pump CABG.

Another aspect to be further investigated is the level of surgeons' experience, as this might weigh on the overall valuation of the OPBHC technique. For example, emergency conversion to CPB is usually followed by a higher risk of mortality. The use of OPBHC could reduce this risk if it is combined with a well-trained surgeon and anesthesiologic team.

Finally, further investigations should evaluate the risk associated with the use of OPBHC or PCI for the revascularization of left ventricular. In fact, OPBHC surgeries are associated with a high level of risk for patients but with good graft patency over time. On the other hand, PCI techniques require more advanced and difficult procedures to guarantee complete revascularization without avoiding subsequent myocardial injuries.

*Coronary Artery Bypass Grafting in High-Risk Patients: On-Pump Beating-Heart CABG DOI: http://dx.doi.org/10.5772/intechopen.115054*
