Revascularization for stable ischemic heart disease: are there new parallels between percutaneous coronary intervention and coronary artery bypass grafting?

Assessment of Bowel End Perfusion After Mesenteric Division: Eye Versus SPY

BACKGROUND

Anastomotic complications related to tissue ischemia cause morbidity in gastrointestinal (GI) surgery. Surgeons' standard practice to predict bowel perfusion is inspection of mesenteric perfusion before anastomosing bowel ends. Augmenting this assessment with fluorescent imaging is under study. A standardized system to evaluate this imaging has not yet been developed. This study compared the surgeon's intraoperative assessment to a novel GI-specific imaging analysis method.

MATERIALS AND METHODS

Forty-nine consecutive patients undergoing open or laparoscopic-assisted bowel resections were enrolled. After mesenteric division, the surgeon marked the site for bowel transection. Near-infrared fluorescence imaging was performed on the marked bowel ends. Imaging analysis identified theoretical transection sites based on the quantification of arterial and microvascular inflow (Perfusion) and venous outflow (Timing). The primary outcome was the measured disparity between the site marked by the surgeon using current standard of care parameters and the imaging-determined site. No clinical outcomes were assessed.

RESULTS

Seventy-two bowel end segments from 46 patients were analyzed. Disparity was found in 11 of 72 (15%) bowel end segments. In five (7%), the disparity was due to either Perfusion or Timing (single), and in six (8%), due to both Perfusion and Timing (combined). In the single disparity group, the median disparity distance was 2.0 cm by Perfusion and 4.0 cm by Timing, and in the combined group, 3.8 cm by Perfusion and 3.5 cm by Timing. Disparity (either single or combined) was in 25% of colon and 11.5% of small bowel (P = NS). Combined and single disparity had equivalent lengths of disparity distance (P = NS).

CONCLUSIONS

Imaging coupled with this GI-specific analysis provides objective, real-time, and interpretable data of intramural blood supply. A 15% disparity rate from current clinical practice was observed.

Noninvasive Quantification of Blood Flow in Epicardial Coronary Arteries, Coronary Artery Bypass Grafts, and Anastomoses

OBJECTIVE

Direct flow measurement in native epicardial coronary arteries, bypass conduits, and anastomoses is severely limited by the invasiveness and inaccuracy of existing technologies. As a result, less than 25% of patients undergoing coronary artery bypass grafting (CABG) worldwide have any intraoperative evaluation performed. A simple, accurate, and noninvasive technology to directly quantify blood flow and rheology surrounding anastomotic sites is a critical unmet need in CABG.

METHODS

Existing technology limitations drove development of a different technology solution. With an optical physics approach, flow in conduits and tissue can be quantified in real time with nonionizing broad-spectrum imaging as well as temporal and spatial analyses. Cardiac motion, calibration, and combining anatomy + physiology in imaging were challenges requiring solutions.

RESULTS

This patented imaging technology was developed and tested in an established porcine cardiac experimental model and in clinical proof-of-concept studies. Flow velocities and flows in epicardial coronary arteries vary physiologically with the cardiac cycle and with acute ischemia, as predicted by previous studies using traditional technologies. Imaging data are captured from a 30-cm viewing distance, analyzed and displayed in real time as a video. The field of view enables capture of flow in the proximal and distal epicardial coronary, the conduit, at the anastomosis and in the distal myocardium simultaneously.

CONCLUSIONS

Rheologic flow interaction between conduit and native coronary at the anastomosis remains the most poorly understood technical aspect of CABG. A noninvasive, noncontact, no-risk imaging technology as simple as a snapshot can provide this critical physiologic information, validate and document intraoperative quality, and improve even further CABG outcomes.

Physiology of in-situ arterial revascularization in coronary artery bypass grafting: Preoperative, intraoperative and postoperative factors and influences

Surgical revascularization with coronary artery bypass grafting (CABG) has become established as the most effective interventional therapy for patients with moderately severe and severe stable ischemic heart disease (SIHD). This recommendation is based on traditional 5-year outcomes of mortality and avoidance of myocardial infarction leading to reintervention and/or cardiac death. However, these results are confounded in that they challenge the traditional CABG surgical tenets of completeness of anatomic revascularization, the impact of arterial revascularization on late survival, and the lesser impact of secondary prevention following CABG on late outcomes. Moreover, the emergence of physiologic-based revascularization with percutaneous cardiovascular intervention as an alternative strategy for revascularization in SIHD raises the question of whether there are similar physiologic effects in CABG. Finally, the ongoing ISCHEMIA trial is specifically addressing the importance of the physiology of moderate or severe ischemia in optimizing therapeutic interventions in SIHD. So it is time to address the role that physiology plays in surgical revascularization. The long-standing anatomic framework for surgical revascularization is no longer sufficient to explain the mechanisms for short-term and long-term outcomes in CABG. Novel intraoperative imaging technologies have generated important new data on the physiologic blood flow and myocardial perfusion responses to revascularization on an individual graft and global basis. Long-standing assumptions about technical issues such as competitive flow are brought into question by real-time visualization of the physiology of revascularization. Our underestimation of the impact of Guideline Directed Medical Therapy, or Optimal Medical Therapy, on the physiology of preoperative SIHD, and the full impact of secondary prevention on post-intervention SIHD, must be better understood. In this review, these issues are addressed through the perspective of multi-arterial revascularization in CABG, which is emerging (after 30 years) as the “standard of care” for CABG. In fact, it is the physiology of these arterial grafts that is the mechanism for their impact on long-term outcomes in CABG. Moreover, a better understanding of all of these preoperative, intraoperative and postoperative components of the physiology of revascularization that will generate the next, more granular body of knowledge about CABG, and enable surgeons to design and execute a better surgical revascularization procedure for patients in the future.

Improving quality and outcomes of coronary artery bypass grafting procedures

The evolution in the approach, clinical care and outcomes of ischemic heart disease, has been dramatic over the past decade. Optimizing medical therapy initially and throughout the care delivery process has been transformative. The addition of new physiologic data to the traditional anatomic framework for diagnosis and therapy of more extensive stable ischemic heart disease (SIHD) enables quality and outcomes improvements in this patient population overall and in the patient subsets of acute coronary syndrome and SIHD. In patients undergoing coronary artery bypass grafting (CABG), these developments have changed the objective goal of surgical revascularization over this time interval. This review discusses the opportunities for quality and outcomes improvement in CABG, in the context of SIHD overall.