Label-free Evaluation of Myocardial Infarct in Surgically Excised Ventricular Myocardium by Raman Spectroscopy

Understanding the viability of the ischemic myocardial tissue is a critical issue in determining the appropriate surgical procedure for patients with chronic heart failure after myocardial infarction (MI). Conventional MI evaluation methods are; however, preoperatively performed and/or give an indirect information of myocardial viability such as shape, color, and blood flow. In this study, we realize the evaluation of MI in patients undergoing cardiac surgery by Raman spectroscopy under label-free conditions, which is based on intrinsic molecular constituents related to myocardial viability. We identify key signatures of Raman spectra for the evaluation of myocardial viability by evaluating the infarct border zone myocardium that were excised from five patients under surgical ventricular restoration. We also obtain a prediction model to differentiate the infarcted myocardium from the non-infarcted myocardium by applying partial least squares regression-discriminant analysis (PLS-DA) to the Raman spectra. Our prediction model enables identification of the infarcted tissues and the non-infarcted tissues with sensitivities of 99.98% and 99.92%, respectively. Furthermore, the prediction model of the Raman images of the infarct border zone enabled us to visualize boundaries between these distinct regions. Our novel application of Raman spectroscopy to the human heart would be a useful means for the detection of myocardial viability during surgery

Label-free detection of myocardial ischaemia in the perfused rat heart by spontaneous Raman spectroscopy

Raman spectroscopy, which identifies intrinsic molecular constituents, has a potential for determining myocardial viability under label-free conditions. However, its suitability for evaluating myocardial ischaemia is undetermined. Focusing on cytochromes, i.e., representative molecules reflecting mitochondrial activity, we tested whether Raman spectroscopy is applicable for evaluating myocardial ischaemia especially during early ischaemic phase. We obtained spontaneous Raman spectra of the subepicardial myocardium in the Langendorff-perfused rat heart upon 532-nm excitation before and during the “stopped-flow,” global ischaemia. Semi-quantitative values of the peak intensities at 750 and 1127 cm−1, which reflect reduced cytochromes c and b, increased immediately and progressively after induction of the stopped flow, indicating progressive reduction of the mitochondrial respiration. Such spectral changes emerged before the loss of 1) mitochondrial membrane potentials measured by the fluorescence intensity of tetramethyl rhodamine ethyl ester or 2) staining of the triphenyl tetrazolium chloride dye in the myocardium. The progressive increases in the Raman peaks by stopped flow were significantly retarded by ischaemic preconditioning. Sequential measurements of the peak intensities at 750 and 1127 cm−1 enabled early detection of the myocardial ischaemia based on the mitochondrial functions. These data suggest that Raman spectroscopy offers the potential to evaluate acute ischaemic heart under label-free conditions

Choice of Hemodynamic Support During Coronary Artery Bypass Surgery for Prevention of Stroke

The objective of this study was to evaluate a protocol involving cerebrovascular accident (CVA) risk evaluation and choose adequate hemodynamic support that prevents major CVA. For evaluation of CVA risk, we undertook head computed tomography (CT), magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), chest CT, carotid artery Doppler echo, carotid artery MRA, and echo scanning of ascending aorta during surgery. Cerebrovascular specialists did the physical examinations and reading of images. Hemodynamic support (chemical arrest on pump, on-pump beating, or off pump) was chosen according to the result of risk evaluation. We retrospectively studied 92 cases before (group A; 1997 October to 1998 November) and 91 after (group B; 1998 November to 2001 January) starting protocol. We also studied urgent cases (group C; 9 cases; 1997 October to 2001 January) in which we did not use the protocol. When adequate hemodynamic support was chosen, major CVA (modified Rankin scale grades 3, 4, and 5) incidence decreased from 6.6% (six case; group A) to 0% (p < .05; group B). There were three major CVA cases in group C (p < .05 vs. group B), in which the ascending aorta was clamped. Our protocol eliminated major CVA associated with elective coronary surgery. We need simpler evaluation, however, when we undertake urgent surgery

Development of an in vivo tissue-engineered, autologous heart valve (the biovalve) : preparation of a prototype model

Objective: This study aimed to develop an autologous heart valve without using traditional in vitro tissue-engineering methods, which necessitate complicated cell management protocols under exceptionally clean laboratory facilities. Methods: An autologous heart valve construct composed of trileaflets was prepared using a specially designed mold. The mold was prepared by covering a silicone rod with a crown-shaped tubular polyurethane scaffold containing 3 horns. The mold was implanted in the dorsal subcutaneous space in Japan White rabbits for 4 weeks. After harvesting, the implanted trileaflet valve-shaped structure with an internal diameter of either 5 or 20 mm was obtained by trimming the membranous tissue formed between the horns located around the silicone rod. The valve substitute was examined both macroscopically and histologically. The tensile strength of the leaflets was measured to rupture. The degree of regurgitation in valve function was evaluated using a flow circuit by calculating the ratio of the regurgitation volume to the forward flow volume. Results: After implantation, the mold was completely covered with connective tissue consisting mostly of collagen and fibroblasts. Harvesting of the mold was straightforward, because there was little adhesion between the formed tissue and the native skin tissue. The trileaflet heart valve construct was obtained after withdrawing the inserted rods and trimming the membranous tissues formed between the horns of the scaffold. It was firmly attached to the scaffold, the interstices and surface of which revealed connective tissues composed of components similar to those of the leaflet tissue. Although the mechanical properties of the leaflet tissue were less efficient than those of the native porcine aortic valve leaflets, satisfactory valvular functions were demonstrated under pulsatile conditions using a flow circuit. No regurgitation was observed under retrograde hydrostatic pressures of up to 60 mm Hg, the physiologic pressure acting on the aortic valves during retrograde aortic flow. Conclusions: The biovalve, an autologous, in vivo tissue-engineered, trileaflet, valve-shaped construct, was developed using our novel in-body tissue architecture technology. The biovalve has the potential to be an ideal prosthetic heart valve, with excellent biocompatibility to the growth of the recipient’s heart