Assessment of cardiovascular function by combining clinical data with a computational model of the cardiovascular system

ObjectiveA sufficient understanding of patients’ cardiovascular status is necessary for doctors to make the best decisions with regard to the treatment of cardiovascular disease; however, it is often not available because of the limitation of clinical measurements. The objective of this study was to examine whether cardiovascular function can be assessed quantitatively and for specific patients by combining clinical data with a computational model of the cardiovascular system.MethodsSeven consecutive patients undergoing off-pump coronary artery bypass grafting were enrolled in this study. The clinical data were collected both during the preoperative diagnosis and during the operation. Sensitivity analysis was performed to select the major model parameters most relevant to the measured data. The major model parameters were then estimated through a data-fitting procedure, enabling a patient-specific quantitative assessment of various aspects of cardiovascular function.ResultsThe results revealed the prevalence of left ventricular diastolic dysfunction in the patients, although the severity of dysfunction exhibits significant interpatient variability (the estimated left ventricular passive elastance varies from 194% to 540% of its reference value). Moreover, 4 of the 7 patients studied had impaired left ventricular systolic function.ConclusionsThe current study demonstrates the feasibility of assessing cardiovascular function quantitatively by combining clinical data with a cardiovascular model. In particular, the assessment utilizes the measurements already in use or available in clinical settings, enhancing the clinical potential of the proposed method

Design study of ultrahigh-speed microwave simulator engine

A design study of microwave simulator engine is presented in this paper. Taking note the simplicity and duality of data flow in finite-difference time-domain (FDTD) scheme, conceptual and hardware designs of the engine are shown for two-dimensional wave phenomena. To store field values in individual SRAMs, efficient use of digital hardware resources is achieved and the engine is constructed by very small size hardware. Based on the design study, a prototype hardware is made and basic operation is confirmed

Off-pump waffle procedure using an ultrasonic scalpel for constrictive pericarditis †

Abstract Radical pericardiectomy alone is not effective in patients with constrictive pericarditis accompanied by epicardial constriction. However, a waffle procedure is very effective in these patients, as we demonstrate in this paper. Firstly, we performed a radical pericardiectomy via a median sternotomy. We used an ultrasonic scalpel for this procedure, and an apical suction device was useful for lifting the heart. This technique is similar to that used in off-pump coronary artery bypass grafting. After the whole heart was dissected from the markedly thickened parietal pericardium, a waffle procedure was performed on the left ventricle first. Multiple longitudinal and transverse incisions were made on the thickened epicardium using an ultrasonic scalpel. After the left ventricle was fully relieved of constriction, the same procedure was performed on the right ventricle. Thereafter, a remarkable improvement of our patient's haemodynamic status was obtained. The whole procedure can be done without cardiopulmonary bypass. We describe tips for performing the waffle procedure without cardiopulmonary bypass using an ultrasonic scalpel and apical suction device, as well as pitfalls to avoid

Comparison of coronary hemodynamics in patients with internal mammary artery and saphenous vein coronary artery bypass grafts: A noninvasive approach using combined two-dimensional and Doppler echocardiography

AbstractBlood flow in bypass grafts and recipient left anterior descending coronary arteries was evaluated with combined two-dimensional and Doppler echocardiography in 15 patients with an internal mammary artery graft and in 24 patients with a saphenous vein graft. Comparative studies of coronary hemodynamics were also performed regarding these two different grafting techniques.The graft vessel was detected in 11 (79%) of 14 patients with an internal mammary artery graft and in 20 (87%) of 23 with a saphenous vein graft. The recipient left anterior descending coronary artery was detected in 10 (67%) of the former group and 17 (71%) of the latter. The blood flow patterns obtained were generally biphasic, consisting of systolic and diastolic phases with higher velocity during diastole. The maximal diastolic flow velocity in internal mammary artery grafts was much higher than that in saphenous vein grafts. In patients with an internal mammary artery graft, the flow pattern characteristics within the recipient coronary artery were quite similar to those within the arterial graft, and flow velocities within the recipient coronary artery and the arterial graft were quantitatively almost identical. This outcome may contribute to the long-term patency seen in internal mammary artery grafts.On the other hand, the flow velocity in saphenous vein grafts was fairly low throughout the cardiac cycle. Flow velocity in the recipient coronary artery in patients with a saphenous vein graft was accelerated only in early diastole. As a result, the recipient coronary artery flow pattern and velocity differed substantially from those in the saphenous vein graft. Internal mammary artery and saphenous vein grafts showed average diastolic peak flow velocity of 57.7 ± 9.9 and 28.0 ± 8.9 cm/s, respectively, compared with 55.1 ± 7.2 and 93.5 ± 14.7 cm/s, respectively, in the recipient coronary arteries with artery grafts and vein grafts.Thus, the Doppler method allowed us to evaluate not only the direct effects of bypass grafting on the coronary circulation, but also the differences in effects between these two different grafting techniques