Effect of graft adaptation of the internal mammary artery on longitudinal phasic blood flow velocity characteristics after surgery
ABSTRACT Left internal mammary artery (LIMA) bypass conduits undergo gradual longitudinal flow transition from the proximal to distal segments, and the diastolic/systolic (D/S) ratios of the flow indices can diagnose graft patency. However, the influence of graft adaptation on this has not been studied. We examined 46 patients with LIMA graft to the left anterior descending artery using a Doppler-tipped guidewire in the proximal, middle, and distal segments; 34 had patent LIMAs (group A: new LIMAs; <1 month postoperatively; n = 22 and group B: old LIMAs; ≥1 month postoperatively; n = 12), and 12 had new LIMAs with distal stenosis (group C). In diastole, the time-averaged peak velocities, maximum peak velocities, and velocity-time integrals in each segment were significantly greater in group A than in groups B or C; however, in systole, they did not differ significantly among the three groups. The D/S ratios of the indices in all segments in group A were significantly greater than those in groups B or C; however, they did not differ between groups B and C in any of the segments. Graft adaptation of a patent LIMA, itself, affects the longitudinal flow transition pattern. The D/S ratio of the three indices in the patent old LIMAs did not differ from those in the LIMAs with distal stenosis early after surgery. The timing of LIMA flow assessment must be considered during assessment of the graft patency from the flow velocity patterns.
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ABSTRACT: Severely decreased ejection-fraction is an established risk-factor for worse outcome after cardiac surgery. We compare outcomes of off-pump coronary artery bypass grafting (OPCAB) and on-pump CABG (ONCABG) in patients with severely compromised EF. From 2004 to 2009, 478 patients with a decreased EF ≤35% underwent myocardial-revascularization. Patients received either OPCAB (n = 256) or ONCABG (n = 222). Propensity score (PS), including 50 preoperative risk-factors, was used to balance characteristics between groups. PS adjusted logistic regression analysis was performed to assess mortality and major adverse cardiac and cerebrovascular events (MACCE). A composite endpoint for major non-cardiac complications such as respiratory failure, renal failure, rethoracotomy was applied. Complete revascularization (CR) was assumed when the number of distal anastomoses was larger than that of diseased vessels. There was no difference for mortality (2.3 vs. 4.1%; PS-adjusted odds ratio (PS-OR) = 1.05; p = 0.93) and MACCE (13.7 vs. 17.6%; PS-OR = 1.22; p = 0.50) including myocardial-infarction (1.4 vs. 4.9%; PS-OR = 0.39; p = 0.26), low cardiac output (2.3 vs. 4.7%; PS-OR = 0.75; p = 0.72) and stroke (2.3 vs. 2.7%; PS-OR = 0.69; p = 0.66). OPCAB patients presented with a trend to less frequent occurrence of the non-cardiac composite (12.1 vs. 22.1%; PS-OR = 0.54; p = 0.059) including renal dysfunction (PAOR = 0.77; 95% CI 0.31-1.9; p = 0.57), bleeding (PAOR = 0.42; 95% CI 0.14-1.20; p = 0.10) and respiratory failure (PAOR = 0.39; 95% CI 0.05-3.29; p = 0.39). The rate of complete revascularization was similar (92.2 vs. 92.8%; PS-OR = 0.75; p = 0.50). OPCAB in patients with severely decreased EF is safe and feasible. It may even benefit these patients in regard to non-cardiac complications and does not come at cost of less complete revascularization.Heart and Vessels 05/2011; 27(3):258-64. DOI:10.1007/s00380-011-0146-0 · 2.11 Impact Factor
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ABSTRACT: The aim of this study was to demonstrate an assessment of left internal mammary artery (LIMA) patency and anatomy by standard left ventriculography, and to define a proposal for predicting LIMA function according to left ventriculography outcome. A total of 335 patients with an indication of coronary angiography were included. Standard coronary angiography and left ventriculography were performed initially. Visualization of LIMA occurred in the late phase of ventriculography and the LIMA visualization frame rate was counted for each patient. Then selective LIMA angiography was performed and LIMA diameter, LIMA course and anatomy, and subclavian artery anatomy were noted. Finally, the results of left ventriculography and LIMA angiography were compared by statistical analysis. During left ventriculography, LIMA was visualized in 96.4% of the patients. The mean LIMA visualization frame rate was 53.8 ± 17.7 and the mean LIMA diameter was 2.60 ± 0.36 mm. There was a strong correlation between LIMA visualization frame rate and LIMA diameter, LIMA course, and also asymptomatic subclavian artery disease (P < 0.001). Regression analysis showed that LIMA visualization frame rate is the major independent determinant for LIMA diameter prediction (P < 0.001); LIMA diameter, LIMA course, proximal LIMA side branch, and subclavian artery disease are the major predictors of LIMA visualization on left ventriculography (P < 0.001). LIMA patency and anatomy can be evaluated accurately with a simple method using left ventriculography. Besides direct visualization of LIMA, the visualization frame rate may constitute a reliable parameter for assessing LIMA function. A LIMA visualization frame rate of less than 50 is associated with a healthy and well-sized LIMA.Heart and Vessels 09/2011; 27(6). DOI:10.1007/s00380-011-0188-3 · 2.11 Impact Factor
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ABSTRACT: Pressure applied during harvesting of the saphenous vein (SV) graft in coronary artery bypass surgery might change its mechanical properties and thereby decrease the patency. This study was performed to assess the mechanical properties of the SV graft distended manually with different levels of pressure and to determine the pressure level that induces changes in its structure and mechanics. Saphenous vein graft segments, collected from 36 patients undergoing coronary artery bypass surgery, were distended with pressures of either 50-60, 75-100, or 130-150 mmHg. Grafts were tested for the stress-strain relationship; the Young's moduli at the low- and high-strain regions were calculated, and their structures were examined by light and electron microscopy. Pressures of 50-60 mmHg did not influence the mechanics of the vein graft, whereas pressures of 75-100 mmHg elevated the elastic modulus of the vein at the low-strain region while pressures above 130 mmHg increased the elastic moduli at both low- and high-strain regions. There was a prominent loss of microfibrils at all distending pressure levels. The mechanical results suggest that distending pressures above 75 mmHg might play a role in graft failure. Furthermore, the absence of microfibrils surrounding elastin suggests that application of distending pressures, even as low as 50 mmHg, can cause degeneration of the elastic fibers following implantation, increasing the stiffness of the graft and thus impairing the graft's function under its new hemodynamic conditions.Heart and Vessels 03/2012; 28(2). DOI:10.1007/s00380-012-0245-6 · 2.11 Impact Factor