Medical & Biological Engineering & Computing, 1994
A mathematical model combining the coronary flow in the epicardial arterial tree and the intramyo... more A mathematical model combining the coronary flow in the epicardial arterial tree and the intramyocardial circulation is presented. The epicardial arterial tree is represented by a resistive capacitive network based on its realistic anatomy. The intramyocardial flow is affected by the pump action of the contracting myocardium through the extravascular compressive pressure (ECP), which, in turn, affects the dynamic resistance
The decision for revascularization in patients with intermediate coronary lesions remains a chall... more The decision for revascularization in patients with intermediate coronary lesions remains a challenging topic, particularly when objective data of reversible ischemia are lacking. In some of the patients, coronary revascularization is performed or deferred without definitive evidence on the clinical significance of the coronary stenosis. We investigated the usefulness of coronary flow reserve (CFR) measurements in 28 patients with intermediate coronary lesions. We compared 20 patients who underwent angioplasty based on Doppler-wire-derived CFR with 8 patients for whom angioplasty was deferred (diameter stenosis of 50.7 +/- 2.0% versus 46.5 +/- 3.1%, P < 0.0001 and CFR of 1.80 +/- 0.32 versus 2.65 +/- 0.11, P = 0.002, respectively). Angioplasty resulted in normalization of the CFR to 2.57 +/- 0.53 (P < 0.0001, versus the baseline value). During a follow-up period of 58.1 weeks (range 23-149 weeks), eight patients in the revascularization group were readmitted to the hospital, one of them with a myocardial infarction in the territory of the target vessel, compared with only one admission in the deferred group. Target-vessel revascularization was performed in three patients (a fourth patient declined it) in the former group, compared with only one in the latter. Symptomatic improvement or no change in clinical status was observed in the majority of patients in both groups (90% in the revascularization group and 87.5% in the deferred group). We conclude that in a selected group of patients with intermediate coronary lesions, measurement of CFR may be a useful tool in determining the need for revascularization based on its physiologic significance. Importantly, deferring PTCA in patients with intermediate lesions and normal CFR values seems to be safe.
BackgroundTransient hyperglycemia is common during acute myocardial infarction in non-diabetic pa... more BackgroundTransient hyperglycemia is common during acute myocardial infarction in non-diabetic patients and is associated with a worse outcome. There is limited data on the outcome of patients who undergo primary percutaneous coronary intervention and have transient hyperglycemia.
The development of ischemic mitral regurgitation (MR) after myocardial infarction may impose hemo... more The development of ischemic mitral regurgitation (MR) after myocardial infarction may impose hemodynamic load during a period of active left ventricular remodeling and promote heart failure (HF). However, few data are available on the relationship between ischemic MR and the long-term risk for HF. We prospectively studied 1190 patients admitted for acute myocardial infarction. Mitral regurgitation was assessed by echocardiography and was considered mild, moderate, and severe when the regurgitant jet area occupied less than 20%, 20% to 40%, and greater than 40% of the left atrial area, respectively. The median duration of follow-up was 24 months (range, 6-48 months). Mild and moderate or severe ischemic MR was present in 39.7% and 6.3% of patients, respectively. After adjusting for ejection fraction and clinical variables (age, sex, Killip class, previous infarction, hypertension, diabetes mellitus, anterior infarction, ST-elevation infarction, and coronary revascularization), compared with patients without MR, the hazard ratios for HF were 2.8 (95% confidence interval [CI], 1.8-4.2; P<.001) and 3.6 (95% CI, 2.0-6.4; P<.001) in patients with mild and moderate or severe ischemic MR, respectively. The adjusted hazard ratios for death were 1.2 (95% CI, 0.8-1.8; P = .43) and 2.0 (95% CI, 1.2-3.4; P = .02) in patients with mild and moderate or severe MR, respectively. There is a graded independent association between the severity of ischemic MR and the development of HF after myocardial infarction. Even mild ischemic MR is associated with an increase in the risk of HF.
Summary A method which characterizes the contraction of the left ventricle (LV) by changes in the... more Summary A method which characterizes the contraction of the left ventricle (LV) by changes in the LV endocardial contour curvatures is presented. A normalized curvature difference function (NCDF) is defined by the difference between the (normalized) curvature functions of end diastolic (ED) and end systolic (ES) contours. Unlike wall-motion based procedures, NCDF is independent of any reference system and of
To prospectively evaluate the sensitivity of myocardial early perfusion defects (EDs) and late en... more To prospectively evaluate the sensitivity of myocardial early perfusion defects (EDs) and late enhancement (LE) at multidetector computed tomography (CT) following acute myocardial infarction (AMI) to predict segment myocardial dysfunction and myocardial functional recovery (MFR), by using echocardiography as the reference standard. Institutional review board approval and informed consent were obtained. Twenty-six patients (25 men, one woman; mean age, 53 years+/-9 [standard deviation]), underwent baseline multidetector CT, coronary angiography, and echocardiography within a week of AMI and a follow-up echocardiography at 3 months. ED, LE, and late hypoattenuation were compared with regional left ventricular function and MFR. A logistic regression model and generalized estimating equation analysis were applied to estimate the predictive effect of ED and LE. Differences between groups were evaluated by using nonpaired Student t tests. All EDs and LE corresponded with AMI location determined by using angiography and echocardiography. For occluded arteries (n=5), no relationship was found between the presence of ED or LE and MFR. For patent arteries (n=21), presence of LE had a respective sensitivity and specificity of 73% and 85% for predicting follow-up segment dysfunction, compared with 57% and 90% for ED. In abnormal baseline segments, nonrecovery was clearly related to the presence and size of segment defect area for both ED (odds ratio: 1.95 [95% confidence interval: 0.9, 4.1] per square centimeter) and LE (odds ratio: 1.85 [95% confidence interval: 1.2, 2.9] per square centimeter). Segments that recovered had significantly lower prevalence of ED and LE, and if present, were significantly smaller than in segments remaining abnormal (P<.05). The presence and size of ED and LE at multidetector CT is closely related to follow-up segment myocardial dysfunction and MFR.
Intraoperative thermographic imaging in open-chest conditions can provide the surgeon with import... more Intraoperative thermographic imaging in open-chest conditions can provide the surgeon with important qualitative information regarding coronary flow by utilizing heat transfer analysis following injection of cold saline into the aortic root. The heat transfer model is based on the assumption that the epicardial temperature changes are mainly due to convection of heat by the blood flow, which may, therefore, be estimated by measuring the temperature variations. Hearts of eight dogs were exposed and imaged by a thermographic camera. Flow in the left arterial descending (LAD) coronary branch was measured by a transit-time flowmeter. 20 ml of cold saline were injected into the aortic root (just after the aortic valve) and the epicardial temperature images were recorded at end-diastole, for 20-30 s. Different flow rates were achieved by 1 min occlusion of the LAD, which affected a reactive hyperemic response. The dynamics of the temperature in the arterial coronary tree was obtained by averaging the temperature over an edge-detected arterial segment for each frame. The heat transfer equation was curve-fitted, and the flow-dependent heat transfer index was correlated with the experimentally determined coronary flow (r = 0.69, p < 0.001). In summary: a method for quantitative estimation of coronary blood flow by thermography and heat transfer analysis was developed and tested in animal experiments. This method can provide important information regarding coronary blood flow during open-chest surgical procedures.
Journal of the American College of Cardiology, 2007
The purpose of this study was to assess the physiologic significance of coronary artery lesions w... more The purpose of this study was to assess the physiologic significance of coronary artery lesions with an integrated single-photon emission computed tomography (SPECT) and computed tomography coronary angiography (CTCA) device. Myocardial perfusion imaging (MPI) with SPECT is of value for assessing the physiologic significance of coronary lesions. Computed tomography coronary angiography is a new technique to noninvasively detect coronary stenosis, with high sensitivity and negative predictive value (NPV) but lower specificity and positive predictive value (PPV). The experimental SPECT/CTCA hybrid imaging device (Infinia gamma camera and LightSpeed16 CT, General Electric, Milwaukee, Wisconsin) enables concurrent assessment of coronary anatomy and myocardial perfusion. Fifty-six patients with angina pectoris underwent single-session SPECT-MPI and CTCA with the hybrid device and coronary angiography (CA) within 4 weeks. The ability of fused SPECT/CTCA images to diagnose physiologically significant lesions showing >50% stenosis and reversible perfusion defects in the same territory was determined and compared with CTCA stand-alone. Of a total of 224 coronary segments in 56 patients, 12 patients and 54 segments (23%) were excluded from further analysis of CTCA. Overall, 170 coronary segments were evaluated. The sensitivity, specificity, PPV, and NPV of CTCA were 96%, 63%, 31%, and 99%, respectively, as compared with 96%, 95%, 77%, and 99%, respectively, for SPECT/CTCA. Hybrid SPECT/CTCA imaging results in improved specificity and PPV to detect hemodynamically significant coronary lesions in patients with chest pain. Single-photon emission computed tomography/CTCA might play a potentially important role in the noninvasive diagnosis of coronary artery disease and introduce an objective decision-making tool for assessing the need for interventions in each occluded vessel.
To evaluate cerebral hemodynamics before and after carotid angioplasty and stenting (CAS) using t... more To evaluate cerebral hemodynamics before and after carotid angioplasty and stenting (CAS) using transcranial Doppler (TCD). Sixty-eight patients (52 men; mean age 69+/-9.5 years) with severe carotid stenosis (83.4%+/-10.2%) were examined by TCD before and 2 months after CAS. Thirty-two (47%) patients had primary carotid stenosis and 36 (53%) had restenosis after carotid endarterectomy (CEA). A broad TCD protocol was employed to estimate cerebral hemodynamics, including assessment of velocities (V) and asymmetry of cerebral blood flow velocity (CBFV) in the middle cerebral artery, (MCA) anterior cerebral artery (ACA), and basilar artery (BA); the pulsatility indexes; and flow acceleration. Ipsilateral MCA mean velocities before stenting were 46.3+/-12.6 cm/s in the primary stenosis group and 47.1+/-12.3 cm/s in restenosis group; after stenting, the velocities were 53.8+/-12.1 and 52.7+/-9.6 cm/s, respectively (p<0.005 for both groups). MCA asymmetry by Vmean before CAS was higher in the primary stenosis group (27.6%+/-2.4% versus 19.8%+/-2.3%, p<0.05). After stenting, this index was significantly lower in both groups: 16.4%+/-2.4% and 12.3%+/-2.3%, respectively (p<0.0001 for each group). All other TCD parameters improved significantly in both groups after CAS as well (p<0.05), showing the strong hemodynamic effect of this procedure. CAS effectively improves cerebral hemodynamics in patients with severe primary and restenosis of the internal carotid artery.
Microembolization to cerebral arteries during percutaneous transluminal carotid angioplasty (PTCA... more Microembolization to cerebral arteries during percutaneous transluminal carotid angioplasty (PTCA) and stenting is well described, as well as different mural pathology in primary versus post–carotid endarterectomy (CEA) restenosis lesions. The purpose of this study is to investigate possible different patterns of embolization in regards to number and distribution of microembolic signals (high-intensity transient signals (HITS)) in patients with primary carotid
Medical & Biological Engineering & Computing, 1994
A mathematical model combining the coronary flow in the epicardial arterial tree and the intramyo... more A mathematical model combining the coronary flow in the epicardial arterial tree and the intramyocardial circulation is presented. The epicardial arterial tree is represented by a resistive capacitive network based on its realistic anatomy. The intramyocardial flow is affected by the pump action of the contracting myocardium through the extravascular compressive pressure (ECP), which, in turn, affects the dynamic resistance
The decision for revascularization in patients with intermediate coronary lesions remains a chall... more The decision for revascularization in patients with intermediate coronary lesions remains a challenging topic, particularly when objective data of reversible ischemia are lacking. In some of the patients, coronary revascularization is performed or deferred without definitive evidence on the clinical significance of the coronary stenosis. We investigated the usefulness of coronary flow reserve (CFR) measurements in 28 patients with intermediate coronary lesions. We compared 20 patients who underwent angioplasty based on Doppler-wire-derived CFR with 8 patients for whom angioplasty was deferred (diameter stenosis of 50.7 +/- 2.0% versus 46.5 +/- 3.1%, P < 0.0001 and CFR of 1.80 +/- 0.32 versus 2.65 +/- 0.11, P = 0.002, respectively). Angioplasty resulted in normalization of the CFR to 2.57 +/- 0.53 (P < 0.0001, versus the baseline value). During a follow-up period of 58.1 weeks (range 23-149 weeks), eight patients in the revascularization group were readmitted to the hospital, one of them with a myocardial infarction in the territory of the target vessel, compared with only one admission in the deferred group. Target-vessel revascularization was performed in three patients (a fourth patient declined it) in the former group, compared with only one in the latter. Symptomatic improvement or no change in clinical status was observed in the majority of patients in both groups (90% in the revascularization group and 87.5% in the deferred group). We conclude that in a selected group of patients with intermediate coronary lesions, measurement of CFR may be a useful tool in determining the need for revascularization based on its physiologic significance. Importantly, deferring PTCA in patients with intermediate lesions and normal CFR values seems to be safe.
BackgroundTransient hyperglycemia is common during acute myocardial infarction in non-diabetic pa... more BackgroundTransient hyperglycemia is common during acute myocardial infarction in non-diabetic patients and is associated with a worse outcome. There is limited data on the outcome of patients who undergo primary percutaneous coronary intervention and have transient hyperglycemia.
The development of ischemic mitral regurgitation (MR) after myocardial infarction may impose hemo... more The development of ischemic mitral regurgitation (MR) after myocardial infarction may impose hemodynamic load during a period of active left ventricular remodeling and promote heart failure (HF). However, few data are available on the relationship between ischemic MR and the long-term risk for HF. We prospectively studied 1190 patients admitted for acute myocardial infarction. Mitral regurgitation was assessed by echocardiography and was considered mild, moderate, and severe when the regurgitant jet area occupied less than 20%, 20% to 40%, and greater than 40% of the left atrial area, respectively. The median duration of follow-up was 24 months (range, 6-48 months). Mild and moderate or severe ischemic MR was present in 39.7% and 6.3% of patients, respectively. After adjusting for ejection fraction and clinical variables (age, sex, Killip class, previous infarction, hypertension, diabetes mellitus, anterior infarction, ST-elevation infarction, and coronary revascularization), compared with patients without MR, the hazard ratios for HF were 2.8 (95% confidence interval [CI], 1.8-4.2; P<.001) and 3.6 (95% CI, 2.0-6.4; P<.001) in patients with mild and moderate or severe ischemic MR, respectively. The adjusted hazard ratios for death were 1.2 (95% CI, 0.8-1.8; P = .43) and 2.0 (95% CI, 1.2-3.4; P = .02) in patients with mild and moderate or severe MR, respectively. There is a graded independent association between the severity of ischemic MR and the development of HF after myocardial infarction. Even mild ischemic MR is associated with an increase in the risk of HF.
Summary A method which characterizes the contraction of the left ventricle (LV) by changes in the... more Summary A method which characterizes the contraction of the left ventricle (LV) by changes in the LV endocardial contour curvatures is presented. A normalized curvature difference function (NCDF) is defined by the difference between the (normalized) curvature functions of end diastolic (ED) and end systolic (ES) contours. Unlike wall-motion based procedures, NCDF is independent of any reference system and of
To prospectively evaluate the sensitivity of myocardial early perfusion defects (EDs) and late en... more To prospectively evaluate the sensitivity of myocardial early perfusion defects (EDs) and late enhancement (LE) at multidetector computed tomography (CT) following acute myocardial infarction (AMI) to predict segment myocardial dysfunction and myocardial functional recovery (MFR), by using echocardiography as the reference standard. Institutional review board approval and informed consent were obtained. Twenty-six patients (25 men, one woman; mean age, 53 years+/-9 [standard deviation]), underwent baseline multidetector CT, coronary angiography, and echocardiography within a week of AMI and a follow-up echocardiography at 3 months. ED, LE, and late hypoattenuation were compared with regional left ventricular function and MFR. A logistic regression model and generalized estimating equation analysis were applied to estimate the predictive effect of ED and LE. Differences between groups were evaluated by using nonpaired Student t tests. All EDs and LE corresponded with AMI location determined by using angiography and echocardiography. For occluded arteries (n=5), no relationship was found between the presence of ED or LE and MFR. For patent arteries (n=21), presence of LE had a respective sensitivity and specificity of 73% and 85% for predicting follow-up segment dysfunction, compared with 57% and 90% for ED. In abnormal baseline segments, nonrecovery was clearly related to the presence and size of segment defect area for both ED (odds ratio: 1.95 [95% confidence interval: 0.9, 4.1] per square centimeter) and LE (odds ratio: 1.85 [95% confidence interval: 1.2, 2.9] per square centimeter). Segments that recovered had significantly lower prevalence of ED and LE, and if present, were significantly smaller than in segments remaining abnormal (P<.05). The presence and size of ED and LE at multidetector CT is closely related to follow-up segment myocardial dysfunction and MFR.
Intraoperative thermographic imaging in open-chest conditions can provide the surgeon with import... more Intraoperative thermographic imaging in open-chest conditions can provide the surgeon with important qualitative information regarding coronary flow by utilizing heat transfer analysis following injection of cold saline into the aortic root. The heat transfer model is based on the assumption that the epicardial temperature changes are mainly due to convection of heat by the blood flow, which may, therefore, be estimated by measuring the temperature variations. Hearts of eight dogs were exposed and imaged by a thermographic camera. Flow in the left arterial descending (LAD) coronary branch was measured by a transit-time flowmeter. 20 ml of cold saline were injected into the aortic root (just after the aortic valve) and the epicardial temperature images were recorded at end-diastole, for 20-30 s. Different flow rates were achieved by 1 min occlusion of the LAD, which affected a reactive hyperemic response. The dynamics of the temperature in the arterial coronary tree was obtained by averaging the temperature over an edge-detected arterial segment for each frame. The heat transfer equation was curve-fitted, and the flow-dependent heat transfer index was correlated with the experimentally determined coronary flow (r = 0.69, p < 0.001). In summary: a method for quantitative estimation of coronary blood flow by thermography and heat transfer analysis was developed and tested in animal experiments. This method can provide important information regarding coronary blood flow during open-chest surgical procedures.
Journal of the American College of Cardiology, 2007
The purpose of this study was to assess the physiologic significance of coronary artery lesions w... more The purpose of this study was to assess the physiologic significance of coronary artery lesions with an integrated single-photon emission computed tomography (SPECT) and computed tomography coronary angiography (CTCA) device. Myocardial perfusion imaging (MPI) with SPECT is of value for assessing the physiologic significance of coronary lesions. Computed tomography coronary angiography is a new technique to noninvasively detect coronary stenosis, with high sensitivity and negative predictive value (NPV) but lower specificity and positive predictive value (PPV). The experimental SPECT/CTCA hybrid imaging device (Infinia gamma camera and LightSpeed16 CT, General Electric, Milwaukee, Wisconsin) enables concurrent assessment of coronary anatomy and myocardial perfusion. Fifty-six patients with angina pectoris underwent single-session SPECT-MPI and CTCA with the hybrid device and coronary angiography (CA) within 4 weeks. The ability of fused SPECT/CTCA images to diagnose physiologically significant lesions showing >50% stenosis and reversible perfusion defects in the same territory was determined and compared with CTCA stand-alone. Of a total of 224 coronary segments in 56 patients, 12 patients and 54 segments (23%) were excluded from further analysis of CTCA. Overall, 170 coronary segments were evaluated. The sensitivity, specificity, PPV, and NPV of CTCA were 96%, 63%, 31%, and 99%, respectively, as compared with 96%, 95%, 77%, and 99%, respectively, for SPECT/CTCA. Hybrid SPECT/CTCA imaging results in improved specificity and PPV to detect hemodynamically significant coronary lesions in patients with chest pain. Single-photon emission computed tomography/CTCA might play a potentially important role in the noninvasive diagnosis of coronary artery disease and introduce an objective decision-making tool for assessing the need for interventions in each occluded vessel.
To evaluate cerebral hemodynamics before and after carotid angioplasty and stenting (CAS) using t... more To evaluate cerebral hemodynamics before and after carotid angioplasty and stenting (CAS) using transcranial Doppler (TCD). Sixty-eight patients (52 men; mean age 69+/-9.5 years) with severe carotid stenosis (83.4%+/-10.2%) were examined by TCD before and 2 months after CAS. Thirty-two (47%) patients had primary carotid stenosis and 36 (53%) had restenosis after carotid endarterectomy (CEA). A broad TCD protocol was employed to estimate cerebral hemodynamics, including assessment of velocities (V) and asymmetry of cerebral blood flow velocity (CBFV) in the middle cerebral artery, (MCA) anterior cerebral artery (ACA), and basilar artery (BA); the pulsatility indexes; and flow acceleration. Ipsilateral MCA mean velocities before stenting were 46.3+/-12.6 cm/s in the primary stenosis group and 47.1+/-12.3 cm/s in restenosis group; after stenting, the velocities were 53.8+/-12.1 and 52.7+/-9.6 cm/s, respectively (p<0.005 for both groups). MCA asymmetry by Vmean before CAS was higher in the primary stenosis group (27.6%+/-2.4% versus 19.8%+/-2.3%, p<0.05). After stenting, this index was significantly lower in both groups: 16.4%+/-2.4% and 12.3%+/-2.3%, respectively (p<0.0001 for each group). All other TCD parameters improved significantly in both groups after CAS as well (p<0.05), showing the strong hemodynamic effect of this procedure. CAS effectively improves cerebral hemodynamics in patients with severe primary and restenosis of the internal carotid artery.
Microembolization to cerebral arteries during percutaneous transluminal carotid angioplasty (PTCA... more Microembolization to cerebral arteries during percutaneous transluminal carotid angioplasty (PTCA) and stenting is well described, as well as different mural pathology in primary versus post–carotid endarterectomy (CEA) restenosis lesions. The purpose of this study is to investigate possible different patterns of embolization in regards to number and distribution of microembolic signals (high-intensity transient signals (HITS)) in patients with primary carotid
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