Assessment of the relative distribution of myocardial flow with myocardial perfusion imaging （MPI） is meth- odologically limited to predict the presence or absence of flow-limited coronary artery disease （CAD）. Th...Assessment of the relative distribution of myocardial flow with myocardial perfusion imaging （MPI） is meth- odologically limited to predict the presence or absence of flow-limited coronary artery disease （CAD）. This limi- tation may often occur, when obstructive lesions involve multiple epicardial coronary arteries or disease-related disturbances of the coronary circulation coexist at the microvascular level. Non-invasive assessment of myocar- dial blood flow in absolute units with position emission tomography （PET） has been positioned as the solution to improve CAD diagnosis and prediction of patient outcomes associated with risks for cardiac events. This article reviews technical and clinical aspects of myocardial blood flow quantitation with PET and discusses the practical consideration of this approach toward worldwide clinical utilization.展开更多
Objectives Nitroglycerine (NTG) enhances coronary blood flow to compromised myocardium is important in relieving ischemia. However, the mechanism for this increase in myocardial blood flow (MBF) is not well defined. I...Objectives Nitroglycerine (NTG) enhances coronary blood flow to compromised myocardium is important in relieving ischemia. However, the mechanism for this increase in myocardial blood flow (MBF) is not well defined. In small vessels and capillaries, relative blood viscosity plays a very important role in determining myocardial vascular resistance (MVR). MVR reduce is due partly to the increase in negative charge of erythrocyte surface. We therefore hypothesized that the enhancement of nutrient blood flow to zones of myocardial ischemia during NTG is partly secondary to reduced MVR and blood flow viscosity. The latter is affected by the negative charge of erythrocyte surface. Methods 6 dogs with LAD flow-limiting stenosis (group 1) and 6 dogs with LAD flow-limiting stenosis and LCx occmusion (group 2) were studied. At baseline and during intracoronary infusions of NTG (0.3-0.6 μg·kg-1·min-1), hemodynamics, MBF (mL·min-1·g-1), whole blood viscosity (WBη, mPa. S), elongation index (EI), eletrophoretic mobility of erythocytes (EME, [μ.s-1)/(V.cm-1)]) and percent wall thickening (%WT) were determined. MVR was calculated using driving pressure/MBF. Results As compared to baseline, no changes in hemodynamics were seen during NTG. MBF increased and MVR decreased significantly in normal bed, the central 25% and the entire of stenosed bed (P<0.05), with a decrease in WBη in both group 1 and group 2 dogs (18.6±9.7 % and 19.2±14.5 %, respectively). However, the % decrease in WBη was proportioned to the % increase in MBF or the % decrease in MVR only in the central 25% of stenosed bed (r=0.87, P<0.001), but not in the entire stenosed bed and normal bed. EI did not show statistically significant differences between during NTG and at baseline, but EME did increase. And the % decrease in WBη during NTG was related to the % increase in EME (r=0.83, P=0.01). Conclusions NTG reduced myocardial vascular resistance and blood viscosity due to the change of negative charge of erythrocyte surface may, in part, be the mechanism of the enhancement of nutrient blood flow to zones of myocardial ischemia. These results provide additional insights into the complex anti-ischemic effects of NTG.展开更多
Background Myocardial blood flow(MBF) can be quantified with myocardial contrast echocardiography (MCE) during a venous infusion of microbubble. A minimal MBF is required to maintain cell membrane integrity and myocar...Background Myocardial blood flow(MBF) can be quantified with myocardial contrast echocardiography (MCE) during a venous infusion of microbubble. A minimal MBF is required to maintain cell membrane integrity and myocardial viability in ischemic condition. Thus, we hypothesized that MCE could be used to assess myocardial viability by the determination of MBF. Methods and ResultsMCE was performed at 4 hours after ligation of proximal left anterior descending coronary artery in 7 dogs with constant venous infusions of microbubbles. The video intensity versus pulsing interval plots derived from each myocardial pixel were fitted to an exponential function: y=A(1-e-βt), where y is Ⅵ at pulsing interval t, A reflects microvascular cross - sectional area (or myocardial blood volume), and βreflects mean myocardial microbubble velocity. The product of A·β represents MBF. MBF was also obtained by ra-diolabeled microsphere method servered as reference. MBF derived by radiolabeled microsphere - method in the regions of normal, ischemia and infarction was 1.5+0.3, 0.7+0.3, 0. 3+0. 2 mL @ min-1@ g-1 respectively. The product of A·β obtained by MCE in those regions was 52. 46±15. 09, 24. 36±3. 89, 3. 74 ±3. 80 respectively. There was good correlation between normalized MBF and the normalized A·β ( r = 0. 81, P=0. 001). Conclusions MCE has an ability to determine myocardial viability in myocardial infarction canine model.展开更多
Background Reportedly, patients with persistent refractory angina due to end-stage coronary artery disease （CAD） not amenable to traditional revascularization techniques have experienced symptomatic relief following...Background Reportedly, patients with persistent refractory angina due to end-stage coronary artery disease （CAD） not amenable to traditional revascularization techniques have experienced symptomatic relief following laser revascularization, either surgical transmyocardial revascularization （TMR） or percutaneous myocardial revascularization （PMR）. In spite of several hypotheses （i.e., channel patency, placebo effect, denervation, neoangiogenesis）, the mechanism of action and the benefit remains controversial. Methods A prospective trial utilizing positron emission tomography （PET） was conducted as an attempt to correlate quantified myocardial blood flow （MBF） to clinical improvement following PMR. Thirteen consecutive patients with angina class 〉11 in spite of maximal medical treatment underwent PMR with a holmium：yttrium-aluminum-garnet （Ho：YAG） laser. MBF at rest and under hyperemia was assessed by [13N]ammonia PET at baseline, 3 and 6 months following PMR. Results Mean angina class and exercise tolerance time improved at 6 months compared with baseline （P 〈0.001）. The clinical results were accompanied with an improvement in hyperemic MBF （P=-0.05） and a reduction in minimal coronary resistance （MCR; P 〈0.05） in PMR-treated segments. Opposite effects, reduced hyperemic MBF and increased MCR, were observed in nontreated segments. The increase in MCR in nontreated segments revealed the favorable therapeutic impact achieved in PMR-treated segments. Conclusion The results of this trial utilizing a quantitative technique to quantify myocardial perfusion link clinical improvement post-PMR to neoangiogenesis and consistently improved microcirculation.展开更多
文摘Assessment of the relative distribution of myocardial flow with myocardial perfusion imaging （MPI） is meth- odologically limited to predict the presence or absence of flow-limited coronary artery disease （CAD）. This limi- tation may often occur, when obstructive lesions involve multiple epicardial coronary arteries or disease-related disturbances of the coronary circulation coexist at the microvascular level. Non-invasive assessment of myocar- dial blood flow in absolute units with position emission tomography （PET） has been positioned as the solution to improve CAD diagnosis and prediction of patient outcomes associated with risks for cardiac events. This article reviews technical and clinical aspects of myocardial blood flow quantitation with PET and discusses the practical consideration of this approach toward worldwide clinical utilization.
文摘Objectives Nitroglycerine (NTG) enhances coronary blood flow to compromised myocardium is important in relieving ischemia. However, the mechanism for this increase in myocardial blood flow (MBF) is not well defined. In small vessels and capillaries, relative blood viscosity plays a very important role in determining myocardial vascular resistance (MVR). MVR reduce is due partly to the increase in negative charge of erythrocyte surface. We therefore hypothesized that the enhancement of nutrient blood flow to zones of myocardial ischemia during NTG is partly secondary to reduced MVR and blood flow viscosity. The latter is affected by the negative charge of erythrocyte surface. Methods 6 dogs with LAD flow-limiting stenosis (group 1) and 6 dogs with LAD flow-limiting stenosis and LCx occmusion (group 2) were studied. At baseline and during intracoronary infusions of NTG (0.3-0.6 μg·kg-1·min-1), hemodynamics, MBF (mL·min-1·g-1), whole blood viscosity (WBη, mPa. S), elongation index (EI), eletrophoretic mobility of erythocytes (EME, [μ.s-1)/(V.cm-1)]) and percent wall thickening (%WT) were determined. MVR was calculated using driving pressure/MBF. Results As compared to baseline, no changes in hemodynamics were seen during NTG. MBF increased and MVR decreased significantly in normal bed, the central 25% and the entire of stenosed bed (P<0.05), with a decrease in WBη in both group 1 and group 2 dogs (18.6±9.7 % and 19.2±14.5 %, respectively). However, the % decrease in WBη was proportioned to the % increase in MBF or the % decrease in MVR only in the central 25% of stenosed bed (r=0.87, P<0.001), but not in the entire stenosed bed and normal bed. EI did not show statistically significant differences between during NTG and at baseline, but EME did increase. And the % decrease in WBη during NTG was related to the % increase in EME (r=0.83, P=0.01). Conclusions NTG reduced myocardial vascular resistance and blood viscosity due to the change of negative charge of erythrocyte surface may, in part, be the mechanism of the enhancement of nutrient blood flow to zones of myocardial ischemia. These results provide additional insights into the complex anti-ischemic effects of NTG.
基金This work was supported in part by grants from thescience and technology foundation of China(39870329).
文摘Background Myocardial blood flow(MBF) can be quantified with myocardial contrast echocardiography (MCE) during a venous infusion of microbubble. A minimal MBF is required to maintain cell membrane integrity and myocardial viability in ischemic condition. Thus, we hypothesized that MCE could be used to assess myocardial viability by the determination of MBF. Methods and ResultsMCE was performed at 4 hours after ligation of proximal left anterior descending coronary artery in 7 dogs with constant venous infusions of microbubbles. The video intensity versus pulsing interval plots derived from each myocardial pixel were fitted to an exponential function: y=A(1-e-βt), where y is Ⅵ at pulsing interval t, A reflects microvascular cross - sectional area (or myocardial blood volume), and βreflects mean myocardial microbubble velocity. The product of A·β represents MBF. MBF was also obtained by ra-diolabeled microsphere method servered as reference. MBF derived by radiolabeled microsphere - method in the regions of normal, ischemia and infarction was 1.5+0.3, 0.7+0.3, 0. 3+0. 2 mL @ min-1@ g-1 respectively. The product of A·β obtained by MCE in those regions was 52. 46±15. 09, 24. 36±3. 89, 3. 74 ±3. 80 respectively. There was good correlation between normalized MBF and the normalized A·β ( r = 0. 81, P=0. 001). Conclusions MCE has an ability to determine myocardial viability in myocardial infarction canine model.
文摘Background Reportedly, patients with persistent refractory angina due to end-stage coronary artery disease （CAD） not amenable to traditional revascularization techniques have experienced symptomatic relief following laser revascularization, either surgical transmyocardial revascularization （TMR） or percutaneous myocardial revascularization （PMR）. In spite of several hypotheses （i.e., channel patency, placebo effect, denervation, neoangiogenesis）, the mechanism of action and the benefit remains controversial. Methods A prospective trial utilizing positron emission tomography （PET） was conducted as an attempt to correlate quantified myocardial blood flow （MBF） to clinical improvement following PMR. Thirteen consecutive patients with angina class 〉11 in spite of maximal medical treatment underwent PMR with a holmium：yttrium-aluminum-garnet （Ho：YAG） laser. MBF at rest and under hyperemia was assessed by [13N]ammonia PET at baseline, 3 and 6 months following PMR. Results Mean angina class and exercise tolerance time improved at 6 months compared with baseline （P 〈0.001）. The clinical results were accompanied with an improvement in hyperemic MBF （P=-0.05） and a reduction in minimal coronary resistance （MCR; P 〈0.05） in PMR-treated segments. Opposite effects, reduced hyperemic MBF and increased MCR, were observed in nontreated segments. The increase in MCR in nontreated segments revealed the favorable therapeutic impact achieved in PMR-treated segments. Conclusion The results of this trial utilizing a quantitative technique to quantify myocardial perfusion link clinical improvement post-PMR to neoangiogenesis and consistently improved microcirculation.
