Image-guided quantification of cardioplegia delivery during cardiac surgery

Mitigating cardiac dysfunction by TOE-guided cardioplegia and mitral valve repair

Based on current guidelines, 15% to 20% of patients undergoing mitral valve repair for regurgitation develop left ventricular dysfunction (ejection fraction < 50%-55%) despite a normal baseline. Two schools of thought have been debated: preexisting myocardial disease or suboptimal intraoperative myocardial protection. In our view, they could be reconciled. It is well recognized that left ventricular ejection fraction with a standard cut off at 50%-55% has limited sensitivity in detecting early systolic impairment in mitral regurgitation patients. Mitral regurgitation also leads to mitochondrial oxidative stress, thus rendering the myocardium more susceptible to ischemia-reperfusion injury and precipitating postoperative cardiac dysfunction. The fall in left ventricular ejection fraction early after mitral valve repair was shown to be caused by the reduction in both myocardial contractility and left ventricular stroke volume. To mitigate the risk to myocardial reperfusion injury, appropriate cardioplegia volume and distribution and well-defined surgical repair processes are equally important. We use transesophageal echocardiography-guided cardioplegia delivery, imaging the intramyocardial flow and ensuring adequate protection of the subendocardium during mitral valve repair. Mild aortic regurgitation on a beating heart often leads to left ventricular dilatation with diminished cardioplegia flow in the myocardium, thus requiring direct ostia cardioplegia. Systematic transesophageal echocardiography assessment before surgery is essential for establishing the mitral regurgitation mechanisms and translating them into precise surgical repair strategies. The benefits of transesophageal echocardiography-guided cardioplegia delivery warrant further clinical trials in order to evolve into part of a high surgical standard.

Cardio-Protective Effects of Multiport Antegrade Cold Blood Cardioplegia Versus Antegrade Cold Blood Cardioplegia in Patients With Left Ventricular Systolic Dysfunction Undergoing Conventional Coronary Artery Bypass Grafting

Introduction

The aim of this study was to compare the in-hospital outcomes of multiport antegrade cold blood cardioplegia through vein grafts versus conventional antegrade cold blood cardioplegia in patients with left ventricle systolic dysfunction who underwent coronary artery bypass grafting (CABG).

Methods

This prospective, randomized clinical study was comprised of patients undergoing on-pump CABG at the Ch. Pervaiz Elahi Institute of Cardiology in Multan, Pakistan from November 18, 2018 to December 17, 2019. Patients with multivessel coronary artery disease and left ventricular systolic dysfunction (ejection fraction < 50%) were included. In Group A (N = 73), multiport antegrade cold blood vein graft cardioplegia was given after every distal anastomosis completed for myocardial preservation. In Group B (N = 73), conventional antegrade cold blood cardioplegia was given for myocardial preservation.

Results

Spontaneous rhythm (without defibrillation applied) after cross-clamp removal was higher in Group A than in Group B (93.3% vs. 85.2%, p < 0.05). Duration of support, ventilation time, and hospital stay were also significantly lower in Group A than in Group B with p = 0.00001, p = 0.03, and p = 0.002, respectively. Intra-aortic balloon pump insertion (4.1% vs. 23.0%, p = 0.02) and operative mortality (0.5% vs. 4.0%, p = 0.35) were also lower in Group A than in Group B. Postoperative left ventricular ejection fraction (LVEF) increased more in Group A than in Group B, and the postoperative LVEF mean value was 44.68% in Group A versus 41.26% in Group B (p = 0.02).

Conclusion

Multiport vein graft blood cardioplegia provides superior myocardial protection in patients with left ventricular systolic dysfunction who underwent CABG. It is also easy to administer, so this technique can be adopted as a routine method for myocardial protection in patients with left ventricular dysfunction planned for on-pump CABG.

Multimodal use of indocyanine green endoscopy in neurosurgery: a single-center experience and review of the literature

During the last 10 years, microscope-integrated indocyanine green fluorescence (m-ICG) has been widely used for assessing real-time blood flow during aneurysm surgery. More recently, an endoscope-integrated indocyanine green fluorescence (e-ICG) has been adopted as a versatile tool during different endoscopic neurosurgical procedures. The purpose of the present report is to evaluate multimodal applications of e-ICG during different endonasal, intraventricular, aneurysm and brain tumor surgeries and provide technical nuances. In addition, we reviewed the literature and identified and compare several overlapping case series of patients treated via an endoscopic integrated indocyanine green fluorescence technique. A total of 40 patients were retrospectively evaluated. Patients were divided into four main groups: (1) endoscopic endonasal approaches (n = 14); (2) ventricular endoscopic approach including patients undergoing third ventriculostomy (n = 8) and tumor biopsy (n = 1); (3) aneurysms surgery (n = 9); and (4) brain parenchymal tumors (n = 8). All patients were successfully treated using the e-ICG dynamic endoscopic visualization, and there were no perioperative complications. Such unique features open up a promising field of applications beyond the use of m-ICG in different surgical field due to the longer duration of e-ICG fluorescence up to 35 ± 7 min. E-ICG represents a new and effective technique for longer real-time visualization of vascular structures preserving normal tissues and functions during different transcranial and endonasal approaches. As the technology and e-ICG resolution improves, the technique has the potential to become a critical tool for different applications in neurosurgery.

Designing protein-based biomaterials for medical applications

Biomaterials produced by nature have been honed through billions of years, evolving exquisitely precise structure-function relationships that scientists strive to emulate. Advances in genetic engineering have facilitated extensive investigations to determine how changes in even a single peptide within a protein sequence can produce biomaterials with unique thermal, mechanical and biological properties. Elastin, a naturally occurring protein polymer, serves as a model protein to determine the relationship between specific structural elements and desirable material characteristics. The modular, repetitive nature of the protein facilitates the formation of well-defined secondary structures with the ability to self-assemble into complex three-dimensional architectures on a variety of length scales. Furthermore, many opportunities exist to incorporate other protein-based motifs and inorganic materials into recombinant protein-based materials, extending the range and usefulness of these materials in potential biomedical applications. Elastin-like polypeptides (ELPs) can be assembled into 3-D architectures with precise control over payload encapsulation, mechanical and thermal properties, as well as unique functionalization opportunities through both genetic and enzymatic means. An overview of current protein-based materials, their properties and uses in biomedicine will be provided, with a focus on the advantages of ELPs. Applications of these biomaterials as imaging and therapeutic delivery agents will be discussed. Finally, broader implications and future directions of these materials as diagnostic and therapeutic systems will be explored.

Laser fluorescence angiography reveals perfusion defects in retrograde cardioplegia

BACKGROUND

Adequate perfusion of the right ventricle with retrograde cardioplegia has always been questioned. However, clinical studies suggested sufficient protection and, up to now, intraoperative assessment of cardioplegia distribution has been difficult.

METHODS

As a pilot study in 14 patients, we used indocyanine green laser fluorescence angiography (ICGLA) to assess vascular and myocardial perfusion of different areas of the right anterior ventricular wall. Regions of interest were analyzed quantitatively using a new software package.

RESULTS

ICGLA allowed rapid and reliable visualization of cardioplegic flow and distribution. Retrograde cardioplegia revealed perfusion defects in the territory of the right anterior cardiac veins when compared to antegrade delivery and to areas close to the left anterior descending vein(s), confirmed by quantitative analyses of maximal fluorescence intensity. Five patients were excluded from quantitative analyses. The learning curve, pitfalls, limitations and special image details are described.

CONCLUSION

A larger study is necessary to examine the relevance of perfusion defects to metabolic changes in affected myocytes and to global right ventricular function.

Image-guided surgery using invisible near-infrared light: fundamentals of clinical translation

The field of biomedical optics has matured rapidly over the last decade and is poised to make a significant impact on patient care. In particular, wide-field (typically > 5 cm), planar, near-infrared (NIR) fluorescence imaging has the potential to revolutionize human surgery by providing real-time image guidance to surgeons for tissue that needs to be resected, such as tumors, and tissue that needs to be avoided, such as blood vessels and nerves. However, to become a clinical reality, optimized imaging systems and NIR fluorescent contrast agents will be needed. In this review, we introduce the principles of NIR fluorescence imaging, analyze existing NIR fluorescence imaging systems, and discuss the key parameters that guide contrast agent development. We also introduce the complexities surrounding clinical translation using our experience with the Fluorescence-Assisted Resection and Exploration (FLARE™) imaging system as an example. Finally, we introduce state-of-the-art optical imaging techniques that might someday improve image-guided surgery even further.

Real-time assessment of cardiac perfusion, coronary angiography, and acute intravascular thrombi using dual-channel near-infrared fluorescence imaging

OBJECTIVES

We have developed an image-guided surgical system based on invisible near-infrared fluorescent light. Presently, the only clinically available near-infrared fluorophore is indocyanine green, which fluoresces at approximately 800 nm and is used for coronary angiography. Our objective was to determine whether methylene blue, already US Food and Drug Administration approved for other indications, has useful near-infrared fluorescence properties for image-guided cardiac surgery.

METHODS

The optical properties of methylene blue were measured after dissolution in 100% serum. Biodistribution and clearance were quantified in organs and tissue after intravenous bolus injection of 2 mg/kg methylene blue in 3 rats. Coronary arteriography and cardiac perfusion were imaged in real time after intravenous bolus injection of 1 mg/kg methylene blue in 5 pigs with coronary obstructions. Coronary angiography and acute thrombi were assessed by using 800-nm fluorophores, indocyanine green, and IR-786-labeled platelets, respectively.

RESULTS

The peak absorbance and emission of methylene blue as a near-infrared fluorophore occur at 667 nm and 686 nm, respectively. After intravenous injection, methylene blue provides highly sensitive coronary angiography. A lipophilic cation, methylene blue is extracted rapidly into tissue, with myocardium displaying unusually high uptake. Methylene blue permits real-time visualization and quantitative assessment of myocardial perfusion. Because of absent spectral overlap, use of 2 independent fluorophores in our imaging system permits simultaneous quantification of perfusion, venous drainage, and/or intravascular thrombi.

CONCLUSIONS

Methylene blue is an effective near-infrared fluorophore that provides direct visualization of coronary arteriography and cardiac perfusion. In conjunction with approximately 800-nm near-infrared fluorophores, important functional assessments during cardiac surgery are also possible.

The FLARE intraoperative near-infrared fluorescence imaging system: a first-in-human clinical trial in breast cancer sentinel lymph node mapping

BACKGROUND

Invisible NIR fluorescent light can provide high sensitivity, high-resolution, and real-time image-guidance during oncologic surgery, but imaging systems that are presently available do not display this invisible light in the context of surgical anatomy. The FLARE imaging system overcomes this major obstacle.

METHODS

Color video was acquired simultaneously, and in real-time, along with two independent channels of NIR fluorescence. Grayscale NIR fluorescence images were converted to visible "pseudo-colors" and overlaid onto the color video image. Yorkshire pigs weighing 35 kg (n = 5) were used for final preclinical validation of the imaging system. A six-patient pilot study was conducted in women undergoing sentinel lymph node (SLN) mapping for breast cancer. Subjects received (99m)Tc-sulfur colloid lymphoscintigraphy. In addition, 12.5 microg of indocyanine green (ICG) diluted in human serum albumin (HSA) was used as an NIR fluorescent lymphatic tracer.

RESULTS

The FLARE system permitted facile positioning in the operating room. NIR light did not change the look of the surgical field. Simultaneous pan-lymphatic and SLN mapping was demonstrated in swine using clinically available NIR fluorophores and the dual NIR capabilities of the system. In the pilot clinical trial, a total of nine SLNs were identified by (99m)Tc- lymphoscintigraphy and nine SLNs were identified by NIR fluorescence, although results differed in two patients. No adverse events were encountered.

CONCLUSIONS

We describe the successful clinical translation of a new NIR fluorescence imaging system for image-guided oncologic surgery.

A low-cost, linear, DC - 35 MHz, high-power LED driver for continuous wave (CW) and fluorescence lifetime imaging (FLIM)

Near-infrared (NIR) fluorescence has the potential to provide surgeons with real-time intraoperative image-guidance. Increasing the signal-to-background ratio of fluorescent agents involves delivering a controllable excitation fluence rate of proper wavelength and/or using complementary imaging techniques such as FLIM. In this study we describe a low-cost linear driver circuit capable of driving Light Emitting Diodes (LEDs) from DC to 35 MHz, at high power, and which permit fluorescence CW and lifetime measurements. The electronic circuit Gerber files described in this article and the list of components are available online at www.frangionilab.org.

A low-cost, universal, and cumulative gating circuit for small and large animal clinical imaging

Image-assisted diagnosis and therapy is becoming more commonplace in medicine. However, most imaging techniques suffer from voluntary or involuntary motion artifacts, especially cardiac and respiratory motions, which degrade image quality. Current software solutions either induce computational overhead or reject out-of-focus images after acquisition. In this study we demonstrate a hardware-only gating circuit that accepts multiple, pseudo-periodic signals and produces a single TTL (0-5 V) imaging window of accurate phase and period. The electronic circuit Gerber files described in this article and the list of components are available online at www.frangionilab.org.