Coronary flow analysis during autoperfusion angioplasty

BACKGROUND: Autoperfusion balloons are available for the protection of the myocardium during balloon angioplasty. The aortic pressure is the driving force that delivers blood to the distal vessel during balloon inflation. Autoperfusion balloons can achieve sufficient flow rates in vitro. The use of these devices is recommended in high-risk patients in danger of haemodynamic collapse during balloon inflation. The quantity of the distal blood flow during balloon inflation in vivo is still unknown. OBJECTIVES: To measure distal coronary perfusion using Doppler guidewires during percutaneous transluminal coronary angioplasty (PTCA) with autoperfusion balloons. METHODS: Coronary flow velocity was measured with 0.014-inch Doppler guidewires bypassing the autoperfusion balloon in eight patients undergoing elective PTCA (degree of stenosis 74 +/- 7.2%). We used balloons with diameters of 3.0 and 3.5 mm. The coronary diameter at the location of the flow measurements was obtained by quantitative angiography in two planes. Coronary blood flow was calculated as the luminal area multiplied by the average peak flow velocity of the Doppler wire divided by 2. Coronary flow velocity reserve was measured before and after angioplasty by intracoronary injection of adenosine. RESULTS: Coronary blood flow was 35 +/- 11.6 ml/min before PTCA. During average inflation times of 4.6 +/- 0.9 min, coronary blood flow was 19 +/- 3.8 ml/min (P = 0.002) after withdrawing the guidewire in the autoperfusion balloon. Five minutes after angioplasty it increased to 42 +/- 13.5 ml/min (P < 0.001). Four patients had electrocardiographic changes during balloon inflation; three patients reported chest pain. One patient required a stent because of a local dissection. To achieve satisfactory angiographic results (residual stenosis 11 +/- 8.5%), we performed 2.1 +/- 0.78 inflations on average with a cumulative inflation time of 8.8 +/- 3.35 min. Coronary flow velocity reserve increased from 1.3 +/- 0.20 to 2.2 +/- 0.22 (P < 0.001). CONCLUSIONS: Using the autoperfusion balloon we measured a coronary blood flow during angioplasty of 56 +/- 10.3% of the distal perfusion before PTCA. In high-risk patients dependent on adequate coronary perfusion, autoperfusion balloons are not able to provide sufficient distal coronary blood flow during balloon inflation. In these patients active coronary or circulatory support devices are recommended.     

Experimental basis of determining maximum coronary, myocardial, and collateral blood flow by pressure measurements for assessing functional stenosis severity before and after percutaneous transluminal coronary angioplasty

BACKGROUND: Severity of coronary artery stenosis has been defined in terms of geometric dimensions, pressure gradient-flow relations, resistance to flow and coronary flow reserve, or maximum flow capacity after maximum arteriolar vasodilation. A direct relation between coronary pressure and flow, however, may only be presumed if the resistances in the coronary circulation are constant (and minimal) as theoretically is the case during maximum arteriolar vasodilation. In that case, pressure measurements theoretically can be used to predict maximum flow and assess functional stenosis severity. METHODS AND RESULTS: A theoretical model was developed for the different components of the coronary circulation, and a set of equations was derived by which the relative maximum flow or fractional flow reserve in both the stenotic epicardial artery and the myocardial vascular bed and the proportional contribution of coronary arterial and collateral flow to myocardial blood flow are calculated from measurements of arterial, distal coronary, and central venous pressures during maximum arteriolar vasodilation. To test this model, five dogs were acutely instrumented with an epicardial, coronary Doppler flow velocity transducer. Distal coronary pressures were measured by an ultrathin pressure-monitoring guide wire (0.015 in.) with minimal influence on transstenotic pressure gradient. Fractional flow reserve was calculated from the pressure measurements and compared with relative maximum coronary artery flow measured directly by the Doppler flowmeter at three different levels of arterial pressure for each of 12 different severities of stenosis at each pressure level. Relative maximum blood flow through the stenotic artery (Qs) measured directly by the Doppler flowmeter showed an excellent correlation with the pressure-derived values of Qs (r = 0.98 +/- 0.01, intercept = 0.02 +/- 0.03, slope = 0.98 +/- 0.04), of the relative maximum myocardial flow (r = 0.98 +/- 0.02, intercept = 0.26 +/- 0.07, slope = 0.73 +/- 0.08), and of the collateral blood flow (r = 0.96 +/- 0.04, intercept = 0.24 +/- 0.07, slope = -0.24 +/- 0.06). Moreover, the theoretically predicted constant relation between mean arterial pressure and coronary wedge pressure, both corrected for venous pressure, was confirmed experimentally (r = 0.97 +/- 0.03, intercept = 9.5 +/- 13.3, slope = 4.4 +/- 1.2). CONCLUSIONS: These results provide the experimental basis for determining relative maximum flow or fractional flow reserve of both the epicardial coronary artery and the myocardium, including collateral flow, from pressure measurements during maximum arteriolar vasodilation. With a suitable guide wire for reliably measuring distal coronary pressure clinically, this method may have potential applications during percutaneous transluminal coronary angioplasty for assessing changes in the functional severity of coronary artery stenoses and for estimating collateral flow achievable during occlusion of the coronary artery.     

Evaluation of successful PTCA by transstenotic flow velocity ratios

Doppler probes mounted on the tip of a guidewire allow the measurement of coronary blood flow velocities, not only proximal but also distal to stenoses eligible for percutaneous transluminal coronary angioplasty (PTCA). The objective of this study was to determine the improvement of transstenotic Doppler flow velocity ratios following PTCA and to investigate the possible impact on restenosis during follow-up control angiography three months later. Doppler flow velocity measurements were performed in 29 patients with 29 stenoses eligible for PTCA. Results of PTCA were morphologically evaluated by computer-assisted quantitative coronary angiography (QCA) and measured hemodynamically by determining transstenotic Doppler flow velocity ratios. Successful PTCA according to QCA was present in all cases with a reduction of mean diameter stenosis from 66 +/- 8% to 35 +/- 7%. Resting spectral peak velocities and velocity integrals were markedly reduced distal to lesions (all P < 0.001), resulting in mean transstenotic flow velocity and velocity integral ratios of less than 0.60 prior to PTCA. Owing to endoluminal enlargement, significant improvement of transstenotic Doppler ratios was observed in mean ratios greater than 0.90 (all P < 0.0001). In patients with restenosis, transstenotic ratios following PTCA demonstrated a tendency to be smaller than in patients without restenosis. Transstenotic Doppler flow velocity ratios are diminished in severe coronary stenoses. Improvement of these ratios provides information on hemodynamic success of interventional procedures. Thus, the determination of intracoronary Doppler flow velocity ratios contributes, in addition to angiographic estimation, to the evaluation of stenoses severity and success of interventional procedures.     

Comparison of magnetic resonance volume flow rates, angiography, and carotid Dopplers. Preliminary results

BACKGROUND AND PURPOSE: We compared the results of conventional angiography, carotid Doppler, and magnetic resonance angiography volume flow rates to determine the clinical utility of volume flow rate assessment of blood flow to the anterior circulation in patients with carotid occlusive disease. METHODS: From 11 symptomatic patients, a total of 22 extracranial carotid arteries were studied with all three techniques. The studies were independently read, and regression analysis was used to compare the measurements. RESULTS: Carotid Doppler measurements of the distal extracranial carotid arteries were proportional to the inverse of the extracranial carotid volume flow rate (r = .53, R2 = 29%, P < .01), volume flow rates were proportional to the inverse of measured percent stenosis on angiography (r = .84, R2 = 71%, P < .01), and Dopplers were proportional to angiography (r = .94, R2 = 90%, P < .01). Symptomatic Doppler systolic velocity was significantly higher (P < .002), symptomatic measured stenosis was significantly higher (P < .002), and symptomatic volume flow rate was significantly lower (P < .01) than their respective asymptomatic-side values. These preliminary observations, however, may well change once a large data set, especially one in which more patients with high-grade carotid stenosis are included, is studied. CONCLUSIONS: Assessment of carotid volume flow rates by magnetic resonance angiography quantifies flow reduction secondary to atherosclerotic occlusive disease. The easily obtained flow data add both documentation of arterial flow characteristics related to internal carotid stenosis and information regarding the adequacy of collateral pathways.     

Assessment of blood flow distal to coronary artery stenoses. Correlations between myocardial positron emission tomography and poststenotic intracoronary Doppler flow reserve

BACKGROUND: Previous studies have correlated quantitative coronary angiographic stenosis severity with positron emission tomography (PET) myocardial perfusion and proximal measurements of intracoronary flow velocities in normal and diseased coronary arteries. The aim of this study was to correlate regional myocardial blood flow (RMBF) derived from [15O]H2O PET with directly measured poststenotic intracoronary Doppler flow velocity data acquired under basal conditions and dipyridamole-induced hyperemia. METHODS AND RESULTS: Eleven consecutive patients 53 +/- 13 years old with ischemic chest pain and isolated proximal left coronary artery stenoses (left anterior descending, 9; left circumflex, 2; mean, 59 +/- 23% diameter stenosis) underwent [15O]H2O myocardial PET and intracoronary Doppler flow velocity studies within 1 week. PET RMBF (mL.g-1.min-1) and myocardial perfusion reserve (MPR) were calculated in poststenotic and normal reference vascular beds. Poststenotic Doppler average peak flow velocities (APV; cm/s) and coronary flow velocity reserve (CFR) were compared with corresponding PET data and quantitative angiographic lesional parameters. PET RMBF and Doppler APV were linearly correlated (r = .60; P < .001), as were poststenotic PET MPR and Doppler CFR (r = .76; P < .0002). Relative coronary flow velocity and MPR ratios between poststenotic and angiographically normal vascular beds were comparably reduced (0.83 +/- 0.25 versus 0.86 +/- 0.21, respectively; P = NS). CONCLUSIONS: Intracoronary Doppler flow velocities acquired distal to isolated left coronary artery stenoses correlated with [15O]H2O PET regional myocardial perfusion and are useful for assessment of the physiological significance of coronary stenoses in humans.     

Effects of intraaortic balloon pumping on septal arterial blood flow velocity waveform during severe left main coronary artery stenosis

OBJECTIVES: We sought to evaluate the effect of intraaortic balloon pumping on the phasic blood velocity waveform into myocardium with severe coronary artery stenosis. BACKGROUND: In the presence of severe coronary artery stenosis, it is not clear whether intraaortic balloon pumping augments intramyocardial inflow during diastole or changes systolic retrograde blood flow from the myocardium to the extramural coronary arteries. METHODS: Using anesthetized open chest dogs (n=7), we introduced severe stenosis in the left main coronary artery to reduce the poststenotic pressure to approximately 60 mm Hg (>90% diameter stenosis). Septal arterial blood flow velocities were measured with a 20-MHz, 80-channel ultrasound pulsed Doppler velocimeter. Left anterior descending arterial flow, aortic pressure and poststenotic distal coronary pressure were measured simultaneously. The diastolic anterograde flow integral and systolic retrograde flow integral were compared in the presence and absence of intraaortic balloon pumping. RESULTS: Although intraaortic balloon pumping augmented diastolic aortic pressure, this pressure increase was not effectively transmitted through stenosis. Septal arterial diastolic flow velocity was not augmented, and left anterior descending arterial flow was unchanged during intraaortic balloon pumping. CONCLUSIONS: In the presence of severe coronary artery stenosis, intraaortic balloon pumping failed to increase diastolic inflow in the myocardium and did not enhance systolic retrograde flow from the myocardium to the extramural coronary artery. Thus, the major effect of intraaortic balloon pumping on the ischemic heart with severe coronary artery stenosis may be achieved by reducing oxygen demand by systolic unloading.     

Noninvasive assessment of significant left anterior descending coronary artery stenosis by coronary flow velocity reserve with transthoracic color Doppler echocardiography

BACKGROUND: Coronary flow reserve has been considered an important diagnostic index of the functional significance of coronary artery stenosis. With Doppler technique, it has been assessed as the ratio of hyperemic to basal coronary flow velocity (coronary flow velocity reserve [CFVR]) by invasive or semiinvasive methods with a Doppler catheter, a Doppler guide wire, and a transesophageal Doppler echocardiographic probe. Recent technological advancement in transthoracic Doppler echocardiography (TTDE) provides measurement of coronary flow velocity in the distal portion of the left anterior descending coronary artery (LAD) and may be useful in the noninvasive CFVR measurement. The purpose of this study was to evaluate the value of CFVR determined by TTDE for the assessment of significant LAD stenosis. METHODS AND RESULTS: We studied 36 patients who underwent coronary angiography for the assessment of coronary artery disease. The study population consisted of 12 patients with significant LAD stenosis (group A) and 24 patients without significant LAD stenosis (group B). With TTDE, coronary flow velocities in the distal LAD were recorded at rest and during hyperemia induced by intravenous infusion of adenosine (0.14 mg x kg(-1) x min(-1)) under the guidance of color Doppler flow mapping. Adequate spectral Doppler recordings of coronary flow in the distal LAD for the assessment of CFVR were obtained in 34 of 36 study patients (94%). The peak and mean diastolic coronary flow velocities at baseline did not differ between groups A and B (23.6+/-10.3 versus 22.9+/-6.6 cm/s and 16.4+/-8.6 versus 14.5+/-4.0 cm/s, respectively). However, the peak and mean coronary flow velocities during hyperemia in group A were significantly smaller than those in group B (35.6+/-16.3 versus 54.2+/-16.3 cm/s and 24.7+/-13.1 versus 37.9+/-13.0 cm/s, respectively; P<.01). There were significant differences in CFVR obtained from peak and mean diastolic velocity between groups A and B (1.5+/-0.2 versus 2.4+/-0.4 and 1.5+/-0.2 versus 2.6+/-0.4, respectively; P<.001). A CFVR from peak diastolic velocity <2.0 had a sensitivity of 92% and a specificity of 82% for the presence of significant LAD stenosis. A CFVR from mean diastolic velocity <2.0 had a sensitivity of 92% and a specificity of 86% for the presence of significant LAD stenosis. CONCLUSIONS: CFVR determined by TTDE is useful in the noninvasive assessment of significant stenotic lesion in the LAD.     

Noninvasive assessment of coronary flow velocity and coronary flow velocity reserve in the left anterior descending coronary artery by Doppler echocardiography: comparison with invasive technique

OBJECTIVES: The purpose of this study was to evaluate whether transthoracic Doppler echocardiography (TTDE) can reliably measure coronary flow velocity (CFV) and coronary flow velocity reserve (CFVR) in the left anterior descending coronary artery (LAD) in the clinical setting. BACKGROUND: Coronary flow velocity measurement has provided useful clinical and physiologic information. Advancement in TTDE provides noninvasive measurement of CFV and CFVR in the distal LAD. METHODS: In 23 patients, CFV in the distal LAD was measured by TTDE (5 or 3.5 MHz) under the guidance of color Doppler flow mapping at the time of Doppler guide wire (DGW) examination. Coronary flow velocity in the distal LAD were measured at baseline and hyperemic conditions (intravenous administration of adenosine 0.14 mg/kg/min) by both TTDE and DGW techniques. Coronary flow velocity reserve was defined as the ratio of peak hyperemic to basal averaged peak velocity in the distal LAD. RESULTS: Clear envelopes of basal and hyperemic CFV in the distal LAD were obtained in 18 (78%) of 23 study patients by TTDE. There were excellent correlations between TTDE and DGW methods for the measurements of CFV (averaged peak velocity: r=0.97, y=0.94x + 0.40; averaged diastolic peak velocity: r=0.97, y=0.94x + 0.69; systolic peak velocities: r=0.97, y=0.91x + 0.87; diastolic peak velocity: r=0.98, y=0.95x + 1.10). Coronary flow velocity reserve from TTDE correlated highly with those from DGW examinations (r=0.94, y=0.95x + 0.21). CONCLUSIONS: Noninvasive measurement of CFV and CFVR in the distal LAD using TTDE accurately reflects invasive measurement of CFV and CFVR by DGW method.     

Prognostic value of intracoronary flow velocity and diameter stenosis in assessing the short- and long-term outcomes of coronary balloon angioplasty: the DEBATE Study (Doppler Endpoints Balloon Angioplasty Trial Europe)

BACKGROUND: The aim of this prospective, multicenter study was the identification of Doppler flow velocity measurements predictive of clinical outcome of patients undergoing single-vessel balloon angioplasty with no previous Q-wave myocardial infarction. METHODS AND RESULTS: In 297 patients, a Doppler guidewire was used to measure basal and maximal hyperemic flow velocities proximal and distal to the stenosis before and after angioplasty. In 225 patients with an angiographically successful percutaneous transluminal coronary angioplasty (PTCA), postprocedural distal coronary flow reserve (CFR) and percent diameter stenosis (DS%) were correlated with symptoms and/or ischemia at 1 and 6 months, with the need for target lesion revascularization, and with angiographic restenosis (defined as DS > or = 50% at follow-up). Logistic regression and receiver operator characteristic curve analyses were applied to determine the prognostic cutoff value of CFR and DS separately and in combination. Optimal cutoff criteria for predictors of these clinical events were DS, 35%; CFR, 2.5. A distal CFR after angioplasty > 2.5 with a residual DS < or = 35% identified lesions with a low incidence of recurrence of symptoms at 1 month (10% versus 19%, P=.149) and at 6 months (23% versus 47%, P=.005), a low need for reintervention (16% versus 34%, P=.024), and a low restenosis rate (16% versus 41%, P=.002) compared with patients who did not meet these criteria. CONCLUSIONS: Measurements of distal CFR after PTCA, in combination with DS%, have a predictive value, albeit modest for the short- and long-term outcomes after PTCA, and thus may be used to identify patients who will or will not benefit from additional therapy such as stent implantation.     

In vitro evaluation of the intravasal Doppler guide wire: determination of hemodynamic effects of stenoses in a flow model

PURPOSE: In a pulsatile hydraulic model, haemodynamic changes caused by stenoses were assessed using an intravascular Doppler guide wire. MATERIAL AND METHODS: In defined stenoses (25, 50, 75 and 87.5% diameter ratio), and with and without collateral flow, a 0.018 inch (0.46 mm) 12 MHz Doppler guide wire was assessed. Flow velocity measurements were taken 20 mm proximal, in, and 20 mm distal to the stenoses. Average peak velocity (APV) and ratios of pre-/poststenotic velocities and pre-/intrastenotic velocities of APV were compared with the grade of stenosis. The degree of the stenosis calculated by the ratio of the cross-sectional area, using the pre- and intrastenotic APV, was correlated with the actual stenosis. RESULTS: The intrastenotic APV increased significantly (APV proximal to the stenosis 15.15 +/- 4.5 cm/s, intrastenotic APV 134.8 +/- 130.9, p < 0.01, Wilcoxon-Mann-Whitney test). The difference between APV pre- and poststenotic was not significant (p > 0.5). Concerning the grade of stenosis the ratio APV pre-/intrastenotic and the consecutively calculated cross-sectional area stenoses was the best predictor (correlation with the known cross-sectional area stenosis r = 0.94 Pearson). CONCLUSION: Using the Doppler guide wire, APV measurements pre- and intrastenotic enable a reliable quantification of the grade of stenosis. The stenosis calculated via the cross-sectional area correlates significantly with the actual stenosis.     

Arteriovenous fistulas aggravate the hemodynamic effect of vein bypass stenoses: an in vitro study

PURPOSE: The purpose of this study was to assess the impact of arteriovenous fistulas combined with varying degrees of stenosis on distal bypass hemodynamics and Doppler spectral parameters. METHODS: In an in vitro flow model bypass stenoses causing 30%, 55%, and 70% diameter reduction were induced 10 cm upstream of a fistula with low outflow resistance. Flow and intraluminal pressure were measured proximal to the stenosis and downstream of the fistula. The waveform parameters peak systolic velocity, end-diastolic velocity, pulsatility index, and pulse rise time were determined from midstream Doppler spectra obtained 10 cm downstream of the fistula. All measurements were carried out with open and clamped fistula. RESULTS: At 30% diameter reducing stenosis opening of the fistula induced a 12% systolic pressure drop across the stenosis but had no adverse effect on the Doppler waveform parameters. At 55% stenosis the pressure drop increased from 16% to 31% after fistula opening. This increased pressure drop was associated with a further reduction in peak systolic velocity, a decrease in pulsatility index, and an enhanced pulse rise time prolongation. Fistula opening at 70% stenosis increased the systolic pressure drop from 31% to 48% and had significant impact on all waveform parameters. CONCLUSIONS: Distal arteriovenous fistulas enhance pressure loss across stenoses and affect downstream velocity waveform configuration. The presence of a combined fistula and a stenosis mimics the distal hemodynamic conditions of a more severe stenosis. Assessment of the hemodynamic impact of fistulas must be undertaken in the evaluation of in situ vein bypass stenoses.     

Immediate and long-term effect of balloon angioplasty or stent implantation on the absolute and relative coronary blood flow velocity reserve

BACKGROUND: There is controversy regarding the immediate and long-term effects of PTCA on the coronary flow reserve. METHODS AND RESULTS: A total of 54 patients with 1-vessel disease and normal left ventricular function were studied after balloon angioplasty (n=34) or stent implantation (n=20). Distal coronary blood flow velocity reserve (CFR) was defined as the ratio of adenosine-induced hyperemic versus baseline blood flow velocity with a 0.014-in Doppler guidewire. The relative CFR was defined as the ratio of the distal CFR and the reference CFR measured in the normal adjacent coronary artery. Hemodynamic and angiographic measurements were performed before and directly after balloon angioplasty or stent implantation and at 6-month follow-up. CFR after PTCA 相似文献   

Objective markers of condom failure

RATIONALE AND OBJECTIVES: The authors compare the magnetic resonance (MR) phase contrast flow velocity measurements in varying concentric stenoses with invasive measurements obtained with a Doppler guidewire. METHODS: Flow velocity measurements were obtained using a calibrated 0.018 inch 12 MHz Doppler guidewire and a 1.0 T MR imaging system in a pulsatile hydraulic model with variable arterial stenoses. Velocity measurements were performed proximal, intrastenotic, and distal to the stenoses. The cross-sectional area of stenosis was calculated from the data of both methods. For MR imaging measurements, fast low-angle shot two-dimensional phase contrast sequences with different velocity encodings were used. RESULTS: Phase contrast flow measurements correlated well (r = 0.95, Pearson) with Doppler guidewire-based flow velocity data. Generally, flow velocities obtained with MR imaging were lower when compared with the Doppler-based data (P < or = 0.001, Wilcoxon matched pairs test). However, the ratios and the calculated cross-sectional area of stenoses showed a high correlation (r = 0.96) with the predefined area of stenoses. CONCLUSIONS: The assessment of flow alterations in vitro due to variable stenoses using MR phase contrast flow measurements is very well correlated with the Doppler guidewire. Consequently, these results required in vivo measurements of atherosclerotic lesions to evaluate the clinical impact.     

Simultaneous measurement of pulmonary venous flow by intravascular catheter Doppler velocimetry and transesophageal Doppler echocardiography: relation to left atrial pressure and left atrial and left ventricular function

OBJECTIVES: The aim of our study was to compare measurements of pulmonary venous flow velocity obtained either by transesophageal Doppler echocardiography or by intravascular catheter Doppler velocimetry. Furthermore, the relation among pulmonary venous flow velocity, left atrial compliance and left atrial pressure was evaluated. BACKGROUND: Data about the relation between left atrial pressure and pulmonary venous flow velocity are controversial. METHODS: A total of 32 patients undergoing elective open heart surgery for coronary artery bypass grafting were included prospectively in the study. Pulmonary venous flow velocity (Doppler catheter) and left atrial pressure (microtip pressure transducer) were recorded simultaneously with recordings of pulmonary venous flow velocity obtained by transesophageal Doppler echocardiography. RESULTS: Agreement between Doppler catheter and Doppler echocardiographic measurements of pulmonary venous flow velocity (n = 18 patients) was analyzed using the Bland-Altmann technique. The 95% limits of agreement were -0.16 to +0.11 m/s for systolic peak velocity, -0.14 to +0.09 m/s for diastolic peak velocity and -0.12 to +0.10 m/s for atrial peak velocity. The closest agreement between both methods was found for the ratio of systolic to diastolic peak velocity, the ratio of systolic to diastolic flow duration and the time from Q deflection on the electrocardiogram to maximal flow velocity. Mean left atrial pressure was strongly correlated with the ratio of systolic to diastolic peak velocity (r = -0.829), systolic velocity-time integral (r = -0.653), time to maximal flow velocity (r = 0.844) and the ratio of systolic to diastolic flow duration (r = -0.556). The ratio of systolic to diastolic peak velocity and the time to maximal flow velocity were identified as strong independent predictors of mean left atrial pressure. Left atrial compliance was not found to be an independent predictor of mean left atrial pressure. CONCLUSIONS: Flow velocity in the left upper pulmonary vein can be reliably recorded by transesophageal pulsed wave Doppler echocardiography. Our data reveal further evidence that mean left atrial pressure can be estimated by the pattern of pulmonary venous flow velocity.     

Evaluation of coronary flow velocity dynamics and flow reserve in patients with Kawasaki disease by means of a Doppler guide wire

OBJECTIVES: To assess the pathophysiologic effects of the coronary sequelae of Kawasaki disease on coronary hemodynamic variables, we regionally evaluated the flow velocity dynamics and flow reserve in coronary vessels with lesions using an intracoronary Doppler flow guide wire. BACKGROUND: The pathophysiologic effects of the coronary sequelae of Kawasaki disease on coronary hemodynamic variables have not been completely clarified, and we previously reported some discrepancies between coronary angiographic findings and exercise stress tests in Kawasaki disease. METHODS: Doppler phasic coronary flow velocity was determined using an 0.018-in. (0.046-cm) intracoronary Doppler flow guide wire at rest and during the adenosine triphosphate-induced hyperemic response in 95 patients (75 male, 20 female, mean age 9.8+/-6.2 years) with Kawasaki disease. RESULTS: In 25 patients with coronary aneurysms in 29 vessels, the average peak velocity and diastolic to systolic velocity ratio were significantly (p < 0.05) decreased in the moderate-sized and large-sized aneurysms. Significantly lower values in coronary flow reserve (CFR) were noted in 3 of 10 vessels with moderate aneurysms and in 4 of 7 vessels with large aneurysms. A significant positive correlation (y = 0.53x + 14.6, r2 = 0.91) was observed between the percent diameter stenosis evaluated by angiography and that calculated from the flow velocity measurement. However, the percent diameter stenosis calculated from the flow velocity measurement was underestimated compared with that determined by angiography in the stenotic lesions of intermediate severity. A reduced CFR was noted in five of seven vessels with intermediate stenosis ranging from 50% to 75%, and also in three vessels with mild stenosis ranging from 30% to 40%. A reduced CFR was also observed in six of the eight angiographically normal vessels associated with the area of reduced perfusion on exercise thallium-201 myocardial scintigraphy. CONCLUSIONS: Abnormalities in flow dynamics and a reduction in flow reserve were revealed in coronary aneurysms of intermediate to large size and in stenotic lesions, even of mild to intermediate severity, in patients with Kawasaki disease. Abnormalities in the coronary microcirculation, as well as epicardial lesions, contribute to the pathophysiologic responses in Kawasaki disease.     

Determinants of collateral development in a canine model with repeated coronary occlusion

It is now accepted that repetitive 2-min coronary occlusion can develop collateral vessels to the area perfused by the occluded coronary artery. However, which factors influence collateral development has yet to be fully elucidated. The goal of the present study was to identify the determinants of the rate of coronary collateral development in dogs undergoing repeated coronary occlusion. The study was conducted in 19 conscious dogs instrumented for measurements of a subendocardial segment length in the area perfused by the left circumflex coronary artery (LCCA), LCCA flow, and left ventricular pressure. An externally inflatable pneumatic occluder was placed around the LCCA. After the recovery from surgery, 2-min LCCA occlusions were conducted eight times daily. Following 141 +/- 61 (SD) LCCA occlusions (20 +/- 7 days), an LCCA occlusion produced no reduction in segment shortening and negligible reactive hyperemia. The total number of LCCA occlusions needed for adequate collateral development (the rate of collateralization) correlated well with the severity of myocardial ischemia during the first occlusion, which was determined mainly by the extent of postsurgical initial collateral circulation. On the other hand, the response to the ischemic stimulus in the later stage of collateral development was independent of the extent of development of the initial postsurgical collaterals. It is concluded that the overall rate of collateral development is slower in dogs with initially poorer collaterals; however, the response of each dog to the ischemic stimulus in the later stage of collateral development was similar among dogs regardless of the extent of the initial collaterals.     

Functional significance of coronary collateral vessels in patients with previous 'Q' wave infarction: relation to aneurysm, left ventricular end diastolic pressure and ejection fraction

The importance of coronary collateral circulation in relation to the left ventricular function, aneurysm formation and size was investigated in 100 patients with previous 'Q' wave myocardial infarction who underwent coronary angiography. Aneurysms were present in 20% of patients. The majority of these (80%) patients had severe or total occlusion of the left anterior descending artery. Thirty four percent of patients without aneurysm had significant collaterals whereas 25% of patients with aneurysms had collaterals (P > 0.05). However, the size of the aneurysm was smaller when adequate collateral circulation was present (Collateral Index 2 or above). The incidence of hypertension and diabetes was similar in both groups. Collateral circulation was more frequently seen in the anterior (60%) as compared to inferior myocardial infarction (40%), but Collateral Index was higher in right coronary artery disease. The number of patients with an elevated left ventricular end-diastolic pressure (> 12) or poor ejection fraction was similar in the two groups with and without collaterals. Thus, there was no beneficial effect of collateral circulation on left ventricular function. The incidence of aneurysm was not significantly lower, although the size of the aneurysm was significantly smaller in the presence of collateral circulation.     

Pathophysiology of coronary collateral circulation in the human

The functional relevance of coronary collaterals in humans has yet to be fully explored. Several studies demonstrated a protective role of collaterals in patients with coronary artery disease. On the other hand, negative aspects of well-developed coronary collaterals have been reported, e.g. a higher rate of restenosis following coronary angioplasty, or a redistribution of blood via collaterals away from the myocardial area in need towards normally perfused areas (coronary steal). In the past, the coronary collateral circulation has been assessed only qualitatively, using visual angiographic or nuclear imaging methods. With the recent advent of intracoronary Doppler and pressure-transducers, quantitative assessment of functional parameters of the coronary circulation has become feasible. This article reviews ongoing research in the field of coronary collaterals in humans, concerning their exact determination, the positive and negative aspects of their structure as well as their functional aspects.     

Abnormal coronary flow dynamics at rest and during tachycardia associated with impaired left ventricular relaxation in humans: implication for tachycardia-induced myocardial ischemia

OBJECTIVES: This study attempted to clarify the effect of ventricular relaxation abnormalities on coronary flow dynamics at rest and during tachycardia in humans. BACKGROUND: Ventricular relaxation abnormality has been demonstrated in animals to have an adverse impact on early diastolic coronary flow dynamics. However, this relation has not been established in humans. Even if the adverse effect were latent at rest, it might become evident during tachycardia because tachycardia reduces coronary flow reserve and facilitates the production of myocardial ischemia. METHODS: Doppler phasic left coronary flow velocity pattern was obtained at rest and during tachycardia in 23 patients without coronary stenosis. The time constant of left ventricular isovolumic pressure (tau) was used to assess ventricular relaxation. RESULTS: The time to peak flow velocity of the diastolic coronary flow wave was longer, and the fraction of the first third of diastolic coronary flow was smaller, in patients with a longer tau (r = 0.58, p < 0.01; r = -0.44, p < 0.05), indicating a close relation between early diastolic coronary flow dynamics and ventricular relaxation. Although rapid atrial pacing yielded an increase in the coronary flow velocity integral per minute in all patients, diastolic coronary flow velocity integral per minute increased in 9 patients with a normal (< or = 40 ms) tau at rest but decreased in 14 patients with a longer (> 40 ms) tau at rest. CONCLUSIONS: Impaired left ventricular relaxation was associated with decreased coronary flow in early diastole at rest and decreased coronary flow throughout diastole during tachycardia in patients without coronary stenosis. These findings may provide more insight into the mechanism of tachycardia-induced subendocardial ischemia in patients with impaired ventricular relaxation but without concomitant coronary stenosis.     

Evaluation of functional importance of coronary artery stenosis by intracoronary Doppler blood flow velocity measurement

Intracoronary doppler blood flow velocity measurements supply important information for clinical decision making during angioplasty, especially with regard to stenoses of ambiguous severity. In the presence of an intermediate stenosis of unknown physiological impact (40-60%), determination of normal flow parameters (coronary flow reserve: CFR, diastolic to systolic velocity ratio: DSVR and proximal to distal velocity ratio: P/D) will make deferment of treatment acceptable. Post-angioplasty success can be based on restoral of normal flowparameters. The inability to achieve normal CFR immediately after angioplasty does not indicate an unsuccessful procedure, it remains to be shown whether a lack of normalization of DSVR and/or P/D does so. Continuous post-lesional flow monitoring can show and quantify the existence of collateral flow.