Systolic coronary flow reversal and abnormal diastolic flow patterns in patients with aortic stenosis: assessment with an intracoronary Doppler catheter

Dynamic Changes in Coronary Flow Pattern During Transcatheter Aortic Valve Replacement in Severe Aortic Stenosis

Coronary flow reserve in patients with severe aortic stenosis decreases even in the absence of coronary stenosis. In this case, the dynamic changes in the coronary flow pattern around transcatheter aortic valve replacement were observed by periprocedural transesophageal echocardiography. (Level of Difficulty: Intermediate.).

Predominant location of coronary artery atherosclerosis in the left anterior descending artery. The impact of septal perforators and the myocardial bridging effect

Introduction

Coronary artery atherosclerosis presents characteristic patterns of plaque distribution despite systemic exposure to risk factors. We hypothesized that local hemodynamic forces induced by the systolic compression of intramuscular septal perforators could be involved in atherosclerotic processes in the left anterior descending artery (LAD) adjacent to the septal perforators’ origin. Therefore we studied the spatial distribution of atherosclerosis in coronary arteries, especially in relation to the septal perforators’ origin.

Material and methods

64-slice computed tomography angiography was performed in 309 consecutive patients (92 male and 217 female) with a mean age of 59.9 years. Spatial plaque distribution in the LAD was analyzed in relation to the septal perforators’ origin. Additionally, plaque distribution throughout the coronary artery tree is discussed.

Results

The coronary calcium score (CCS) was positive in 164 patients (53.1%). In subjects with a CCS > 0, calcifications were more frequent in the LAD (n = 150, 91.5%) compared with the right coronary artery (RCA) (n = 94, 57.3%), circumflex branch (CX) (n = 76, 46.3%) or the left main stem (n = 42, 25.6%) (p < 0.001). Total CCS was higher in the LAD at 46.1 (IQR: 104.2) and RCA at 34.1 (IQR: 90.7) than in the CX at 16.8 (IQR: 61.3) (p = 0.007). In patients with calcifications restricted to a single vessel (n = 54), the most frequently affected artery was the LAD (n = 42, 77.8%). In patients with lesions limited to the LAD, the plaque was located mostly (n = 37, 88.1%) adjacent to the septal perforators’ origin.

Conclusions

We demonstrated that coronary calcifications are most frequently located in the LAD in proximity to the septal branch origin. A possible explanation for this phenomenon could be the dynamic compression of the tunneled septal branches, which may result in disturbed blood flow in the adjacent LAD segment (milking effect).

The role of septal perforators and "myocardial bridging effect" in atherosclerotic plaque distribution in the coronary artery disease

The distribution of atherosclerotic plaque burden in the human coronary arteries is not uniform. Plaques are located mostly in the left anterior descending artery (LAD), then in the right coronary artery (RCA), circumflex branch (LCx) and the left main coronary artery (LM) in a decreasing order of frequency. In the LAD and LCx, plaques tend to cluster within the proximal segment, while in the RCA their distribution is more uniform. Several factors have been involved in this phenomenon, particularly flow patterns in the left and right coronary artery. Nevertheless, it does not explain the difference in lesion frequency between the LAD and the LCx as these are both parts of the left coronary artery. Branching points are considered to be the risk points of atherosclerosis. In the LCx, the number of side branches is lower than in the LAD or RCA and there are no septal perforators with intramuscular courses like in the proximal third of the LAD and the posterior descending artery (PDA). We hypothesized that septal branches generate disturbed flow in the LAD and PDA in a similar fashion to the myocardial bridge (myocardial bridging effect). This coronary architecture determines the non-uniform plaque distribution in coronary arteries and LAD predisposition to plaque formation.

[Coronary microvascular dysfunction and aortic stenosis: an update]

The coronary microcirculatory impairment is a key feature of the pathophysiology of aortic stenosis (AS), the most operated valvular disease over the world. Several studies showed this coronary microcirculatory impairment in AS, using different tools and protocols, in various patient population of AS. This article will review the impairment of the coronary microcirculation in AS underlining its multifactorial origin, its functional part related to the hemodynamic consequences of AS, its complex relationship with left ventricular hypertrophy, and its potential diagnostic and prognostic value.

Acceleration time of systolic coronary flow velocity to diagnose coronary stenosis in patients with microvascular dysfunction

BACKGROUND

The aim of this study was to test whether acceleration time of systolic coronary flow velocity could contribute to the diagnosis of coronary stenosis in patients with microvascular dysfunction, on the basis of the hypothesis that systolic coronary flow is less influenced by microvascular function because of compressed myocardium.

METHODS

Coronary flow velocity was assessed in the left anterior descending coronary artery during hyperemia with intravenous adenosine by echocardiography in 502 patients who were scheduled for coronary angiography because of coronary artery disease and significant valvular disease. Coronary flow velocity reserve (CFVR) and the percentage acceleration time (%AT), as the percentage of the time from the beginning to the peak of systolic coronary flow over systolic time during hyperemia, were calculated. The diagnostic ability of CFVR and %AT for angiographic coronary artery stenosis was then analyzed. As invasive substudies, fractional flow reserve and %AT by a dual-sensor (pressure and Doppler velocity) guidewire were measured simultaneously with %AT on transthoracic echocardiography (n = 14).

RESULTS

Patients with coronary stenosis had significantly lower CFVR (1.7 ± 0.4) and greater %AT (65 ± 9%) compared with those without stenosis (2.6 ± 0.6 and 50 ± 13%, respectively). Percentage acceleration time by Doppler echocardiography was in good agreement with %AT (r = 0.98) and fractional flow reserve (r = 0.74) invasively measured by dual-sensor guidewire. Cutoff values of CFVR and %AT were determined as 2.0 and 60% in receiver operating characteristic curve analysis. The sensitivity, specificity, and accuracy of CFVR to detect coronary stenosis were 71.1%, 77.3%, and 75.4%, while those of %AT were 83.4%, 71.8%, and 75.4%, respectively. In addition, %AT provided high accuracy to detect coronary stenosis, especially in patients with previous myocardial infarctions, valvular disease, and left ventricular hypertrophy (81.1%, 84.1%, and 73.4%, respectively).

CONCLUSIONS

The %AT of systolic coronary flow velocity is a promising marker to diagnose coronary stenosis in patients with microvascular dysfunction.

Standard method for ultrasound imaging of coronary artery in children

The Child Coronary Arterial Diameter Reference Study Group of the Japan Kawasaki Disease Society recommends ultrasound imaging as the standard method for measuring the diameter of the coronary artery in children. The patient is examined in a supine or right decubitus position by using a sector probe (≥ 5 MHz). The coronary arterial diameter measured at the minimum gain setting is the distance between the internal echo edge and the internal echo edge. The diameter is measured during the early diastolic phase at the end of the T wave. The left main coronary artery and the proximal right coronary artery are approached from the precordial short axis at the level of the aortic valve. The proximal and mid-right coronary arteries are observed on the atrioventricular groove, anterior to the tricuspid valve ring. The right coronary artery of the acute margin of the heart runs along the right side of the tricuspid valve ring. The distal right coronary artery is observed on the posterior atrioventricular groove, and the posterior descending branch of the right coronary artery is observed on the posterior interventricular groove. The right coronary artery is also well observed from the right sternal border in the right decubitus position. Proximal and mid-anterior descending arteries are observed on the anterior interventricular groove. The proximal left circumflex coronary artery is observed in the atrioventricular groove, anterior to the mitral valve ring.

In Vitro Investigation of the Impact of Aortic Valve Stenosis Severity on Left Coronary Artery Flow

Patients with aortic valve stenosis (AS) may experience angina pectoris even if they have angiographically normal coronary arteries. Angina is associated with a marked increase in the risk of sudden death in AS patients. Only a few in vitro models describing the interaction between the left ventricular and aortic pressures, and the coronary circulation have been reported. These models were designed for specific research studies and they need to be improved or modified when other specific studies are required. Consequently, we have developed an in vitro model that is able to mimic the coronary circulation in presence of aortic stenosis. First, we have validated the model under physiological conditions. Then, we have examined and quantified the hemodynamic effects of different degrees of AS (from normal to severe AS) on the coronary flow using a model of the normal left coronary artery. In the coronary in vitro model without AS (normal valve), the amplitude and shape of coronary flow were similar to those observed in in vivo measurements obtained under physiological conditions, as described by Hozumi et al. (1998, “Noninvasive Assessment of Significant Left Anterior Descending Coronary Artery Stenosis by Coronary Flow Velocity Reserve With Transthoracic Color Doppler Echocardiography,” Circulation, 97, pp. 1557–1562). The presence of an AS induced an increase in the maximum and mean coronary flow rates (97% and 73%, respectively, for a very severe AS). Furthermore, when AS was very severe, a retrograde flow occurred during systole. This study allowed us to validate our coronary in vitro model under physiological conditions, both in the absence and presence of AS. These changes could explain the fact that even if patients have angiographically normal epicardial coronary arteries, we can observe the occurrence of angina pectoris in these patients in the presence of an AS.

Impairment of coronary flow reserve in aortic stenosis

Coronary flow reserve (CFR) is markedly reduced in patients with severe aortic valve stenosis (AS), but the exact mechanisms underlying this impairment of CFR in AS remain unclear. Reduced CFR is the key mechanism leading to myocardial ischemia symptoms and adverse outcomes in AS patients. The objective of this study was to develop an explicit mathematical model formulated with a limited number of parameters that describes the effect of AS on left coronary inflow patterns and CFR. We combined the mathematical V3 (ventricular-valvular-vascular) model with a new lumped-parameter model of coronary inflow. One thousand Monte-Carlo computational simulations with AS graded from mild up to very severe were performed within a wide range of physiological conditions. There was a good agreement between the CFR values computed with this new model and those measured in 24 patients with isolated AS ( r = 0.77, P < 10−4). A global sensitivity analysis showed that the valve effective orifice area (EOA) was the major physiological determinant of CFR (total sensitivity index = 0.87). CFR was markedly reduced when AS became severe, i.e., when EOA was <1.0 cm2, and was generally exhausted when the EOA was <0.5–0.6 cm2. The reduction of CFR that is associated with AS can be explained by the concomitance of 1) reduced myocardial supply as a result of decreased coronary perfusion pressure, and 2) increased myocardial metabolic demand as a result of increased left ventricular workload.

Echocardiographic and hemodynamic determinants of right coronary artery flow reserve and phasic flow pattern in advanced non-ischemic cardiomyopathy

Background

In patients with advanced non-ischemic cardiomyopathy (NIC), right-sided cardiac disturbances has prognostic implications. Right coronary artery (RCA) flow pattern and flow reserve (CFR) are not well known in this setting. The purpose of this study was to assess, in human advanced NIC, the RCA phasic flow pattern and CFR, also under right-sided cardiac disturbances, and compare with left coronary circulation. As well as to investigate any correlation between the cardiac structural, mechanical and hemodynamic parameters with RCA phasic flow pattern or CFR.

Methods

Twenty four patients with dilated severe NIC were evaluated non-invasively, even by echocardiography, and also by cardiac catheterization, inclusive with Swan-Ganz catheter. Intracoronary Doppler (Flowire) data was obtained in RCA and left anterior descendent coronary artery (LAD) before and after adenosine. Resting RCA phasic pattern (diastolic/systolic) was compared between subgroups with and without pulmonary hypertension, and with and without right ventricular (RV) dysfunction; and also with LAD. RCA-CFR was compared with LAD, as well as in those subgroups. Pearson's correlation analysis was accomplished among echocardiographic (including LV fractional shortening, mass index, end systolic wall stress) more hemodynamic parameters with RCA phasic flow pattern or RCA-CFR.

Results

LV fractional shortening and end diastolic diameter were 15.3 ± 3.5 % and 69.4 ± 12.2 mm. Resting RCA phasic pattern had no difference comparing subgroups with vs. without pulmonary hypertension (1.45 vs. 1.29, p = NS) either with vs. without RV dysfunction (1.47 vs. 1.23, p = NS); RCA vs. LAD was 1.35 vs. 2.85 (p < 0.001). It had no significant correlation among any cardiac mechanical or hemodynamic parameter with RCA-CFR or RCA flow pattern. RCA-CFR had no difference compared with LAD (3.38 vs. 3.34, p = NS), as well as in pulmonary hypertension (3.09 vs. 3.10, p = NS) either in RV dysfunction (3.06 vs. 3.22, p = NS) subgroups.

Conclusion

In patients with chronic advanced NIC, RCA phasic flow pattern has a mild diastolic predominance, less marked than in LAD, with no effects from pulmonary artery hypertension or RV dysfunction. There is no significant correlation between any cardiac mechanical-structural or hemodynamic parameter with RCA-CFR or RCA phasic flow pattern. RCA flow reserve is still similar to LAD, independently of those right-sided cardiac disturbances.

ASSESSMENT OF THE REPEATABILITY OF FELINE ECHOCARDIOGRAPHY USING CONVENTIONAL ECHOCARDIOGRAPHY AND SPECTRAL PULSE-WAVE DOPPLER TISSUE IMAGING TECHNIQUES

The objective of this study was to determine the intraoperator, intraobserver, and interobserver repeatability in a series of conventional echocardiographic parameters and in some of the newer measurements of diastolic function, including color M-mode flow propagation velocity, isovolumic relaxation time and pulsed-wave Doppler tissue imaging velocities. Four healthy cats were each scanned five times over a 3-day period. The repeatability of these echocardiographic analyses was compared using Bland-Altman analysis (intraoperator repeatability). After a minimum of 5 weeks, one scan was randomly selected from each cat, and was remeasured by the original observer and the results compared using a standard paired Student's t-test (intraobserver repeatability). One scan from each cat was then randomly selected and two observers, with similar levels of experience, measured each of these scans. The repeatability of these echocardiographic analyses was compared using Bland-Altman analysis (interobserver repeatability). The conventional two-dimensional (2D), M-mode and spectral Doppler measurements were repeatable in both their acquisition and measurement by a single investigator; there was a greater degree of variation between the two observers. The predominant (S', E', and A') pulsed-wave Doppler tissue imaging velocities from the left apical four-chambered view, generally had a coefficient of variation of approximately 20% (range 9.62-34.08%). However, with pulsed-wave Doppler tissue imaging, velocities recorded during the isovolumic phases, the velocity of the tricuspid annulus, and the radial fiber velocity within the interventricular septum, frequently had coefficients of variation in excess of 20% and should therefore be interpreted with caution.

Cross-Talk Between Cardiac Muscle and Coronary Vasculature

The cardiac muscle and the coronary vasculature are in close proximity to each other, and a two-way interaction, called cross-talk, exists. Here we focus on the mechanical aspects of cross-talk including the role of the extracellular matrix. Cardiac muscle affects the coronary vasculature. In diastole, the effect of the cardiac muscle on the coronary vasculature depends on the (changes in) muscle length but appears to be small. In systole, coronary artery inflow is impeded, or even reversed, and venous outflow is augmented. These systolic effects are explained by two mechanisms. The waterfall model and the intramyocardial pump model are based on an intramyocardial pressure, assumed to be proportional to ventricular pressure. They explain the global effects of contraction on coronary flow and the effects of contraction in the layers of the heart wall. The varying elastance model, the muscle shortening and thickening model, and the vascular deformation model are based on direct contact between muscles and vessels. They predict global effects as well as differences on flow in layers and flow heterogeneity due to contraction. The relative contributions of these two mechanisms depend on the wall layer (epi- or endocardial) and type of contraction (isovolumic or shortening). Intramyocardial pressure results from (local) muscle contraction and to what extent the interstitial cavity contracts isovolumically. This explains why small arterioles and venules do not collapse in systole. Coronary vasculature affects the cardiac muscle. In diastole, at physiological ventricular volumes, an increase in coronary perfusion pressure increases ventricular stiffness, but the effect is small. In systole, there are two mechanisms by which coronary perfusion affects cardiac contractility. Increased perfusion pressure increases microvascular volume, thereby opening stretch-activated ion channels, resulting in an increased intracellular Ca2+transient, which is followed by an increase in Ca2+sensitivity and higher muscle contractility (Gregg effect). Thickening of the shortening cardiac muscle takes place at the expense of the vascular volume, which causes build-up of intracellular pressure. The intracellular pressure counteracts the tension generated by the contractile apparatus, leading to lower net force. Therefore, cardiac muscle contraction is augmented when vascular emptying is facilitated. During autoregulation, the microvasculature is protected against volume changes, and the Gregg effect is negligible. However, the effect is present in the right ventricle, as well as in pathological conditions with ineffective autoregulation. The beneficial effect of vascular emptying may be reduced in the presence of a stenosis. Thus cardiac contraction affects vascular diameters thereby reducing coronary inflow and enhancing venous outflow. Emptying of the vasculature, however, enhances muscle contraction. The extracellular matrix exerts its effect mainly on cardiac properties rather than on the cross-talk between cardiac muscle and coronary circulation.

Ultrasonographic assessment of basal coronary flow as a screening tool to exclude significant left anterior descending coronary artery stenosis

OBJECTIVE

Coronary blood flow exhibits a biphasic pattern at rest with a higher diastolic and a smaller systolic component. In the present investigation, we evaluated whether a decreased diastolic to systolic velocity ratio of basal coronary flow may be useful in the identification of subjects with significant left anterior descending coronary artery (LAD) stenosis.

METHODS

One hundred and twenty-nine consecutive patients (62 with unstable angina, 25 with acute myocardial infarction and 42 with chronic coronary artery disease) were included in the study. Blood flow velocities were recorded in the mid-distal portion of the LAD using an ATL 5000 CV HDI ultrasound system. All patients underwent coronary angiography and were divided into two groups according to the absence (group 1) or the presence (group 2) of significant LAD stenosis (lumen narrowing > or = 70%). In 60 of the 129 patients, coronary flow reserve was evaluated non-invasively.

RESULTS

Adequate Doppler recordings in the LAD were obtained by transthoracic echocardiography in 113 patients. There were no differences between groups with regard to sex, cardiovascular risk factors, left ventricular mass and volumes, ejection fraction, whereas the diastolic to systolic velocity ratio of basal coronary flow was significantly lower in group 2 patients (1.41 +/- 4.7 vs. 2.08 +/- 0.64, P < 0.00001). The receiver operating characteristic curve showed that a diastolic to systolic velocity ratio < 1.6 had a sensitivity of 77%, a specificity of 91%, a positive predictive value of 77%, a negative predictive value of 97%, and a diagnostic accuracy of 84% for the presence of significant LAD stenosis. In 55/60 patients, results of basal coronary flow and coronary flow reserve were concordant. On multivariate logistic regression analysis, the diastolic to systolic velocity ratio was a strong independent predictor of LAD stenosis > or = 70% (odds ratio 4.90, 95% confidence interval 1.65-7.30).

CONCLUSIONS

The present findings suggest that assessment of basal coronary flow in the LAD may be useful to rule out the presence of significant stenosis.

Transthoracic echocardiographic evaluation of coronary flow reserve in patients with hypertrophic cardiomyopathy

Recently, it has become possible to measure coronary flow reserve (CFR) non-invasively with transthoracic echocardiography (TTE). Twenty-one hypertrophic cardiomyopathy (HCMP) patients with asymmetric septal hypertrophy who had either not started medication or had stopped medication for at least 24 h were enrolled, along with 29 normal subjects. Mean diastolic coronary flow velocity (CFmv) and time velocity integral of diastolic coronary flow velocity (CFtvi) were measured at the distal left anterior descending artery with a 7 MHz transducer at the baseline and after dipyridamole infusion at a dose of 0.56 mg/kg. CFR was defined as the ratio of CFmv after dipyridamole over CFmv before dipyridamole. The baseline values for CFmv and CFtvi were significantly higher (0.40+/-0.09 vs. 0.31+/-0.06 m/s, p<0.001, 0.25+/-0.07 vs. 0.16+/-0.04 m, p<0.001, respectively), while that for CFR was significantly lower (2.01+/-0.42 vs. 3.06+/-0.39 m/s, p<0.001) in the HCMP patients, compared to the normal subjects. In the HCMP patients, CFR showed a moderate negative correlation with both baseline CFmv (r=-0.522, p=0.015) and baseline CFtvi (r=-0.495, p=0.034). Treadmill test was performed in 14 patients with Bruce protocol. CFR, baseline CFmv and baseline CFtvi did not correlate with maximal exercise time. In seven patients, the CFR measured after verapamil treatment was not significantly different from that measured before treatment. In conclusion, in patients with HCMP, CFR is probably reduced due to the recruitment of vasodilatory capacity at the resting state and this reduction is not directly related to reduced exercise capacity. Also, CFR is not affected by treatment with calcium antagonist.

Coronary flow velocity pattern immediately after percutaneous coronary intervention as a predictor of complications and in-hospital survival after acute myocardial infarction

BACKGROUND

Recently, it was reported that the degree of microvascular injury and left ventricular functional recovery during the chronic period can be predicted after treatment of the infarct-related artery based on the coronary flow velocity (CFV) pattern assessed using a Doppler guidewire. The aim of this prospective study was to examine whether the CFV pattern may predict complications and in-hospital survival after acute myocardial infarction (AMI).

METHODS AND RESULTS

The study population consisted of 169 consecutive patients with a first anterior AMI successfully treated with percutaneous coronary intervention (PCI). We examined the CFV pattern immediately after PCI using a Doppler guidewire. In accordance with previous findings, we defined severe microvascular injury as a diastolic deceleration time < or =600 ms and the presence of systolic flow reversal. Patients were divided into two groups: those without severe microvascular injury (n=118; group 1) and those with severe microvascular injury (n=51; group 2). All of the patients who had cardiac rupture were in group 2. Congestive heart failure (CHF) was observed more frequently in group 2 than in group 1 (53% versus 8%, P<0.001). The in-hospital cardiac mortality rate was significantly higher in group 2 than in group 1 (18% versus 0%, P<0.001). Nine patients in group 2 died, 5 patients because of CHF and 4 patients because of cardiac rupture.

CONCLUSIONS

These findings suggest that the CFV pattern is an accurate predictor of the presence or absence of complications and of in-hospital survival after AMI.

Coronary flow reserve improves after aortic valve replacement for aortic stenosis: an adenosine transthoracic echocardiography study

OBJECTIVES

The goal of this study was to assess coronary flow reserve (CFR) before and after aortic valve replacement (AVR).

BACKGROUND

Coronary flow reserve is impaired under conditions of left ventricular (LV) hypertrophy. It is not known whether CFR improves with regression of LV hypertrophy in humans.

METHODS

We investigated 35 patients with pure aortic stenosis, LV hypertrophy and normal coronary arteriograms. Patients underwent adenosine transthoracic echocardiography on two occasions--immediately before AVR and six months postoperatively. Left ventricular mass, distal left anterior descending coronary artery (LAD) diameter, flow and CFR were assessed on each occasion.

RESULTS

Distal LAD diameter was successfully imaged in 30 patients (86%), and blood flow was successfully imaged in 27 (77%). Paired data were subsequently available in 24 patients, of whom 14 were men, mean age 68.1+/-12.5 years, body mass index 24.5+/-2.0 kg/m2, aortic valve gradient 93+/-32 mm Hg. Pre- to post-AVR a significant decrease was seen in LV mass (271+/-38 vs. 236+/-32g, p<0.01) and LV mass index (154+/-21 vs. 134+/-21 g/m2, p< 0.01). Distal LAD diameter fell from 2.27+/-0.37 to 2.23+/-0.35 mm, p = 0.08). Pre- to post-AVR there was no significant change in resting parameters of peak diastolic velocity (0.43+/-0.16 vs. 0.41+/-0.11 m/s), distal LAD flow 23.3+/-10.1 vs. 20.9+/-5.2 ml/min or distal LAD flow scaled for LV mass (8.7+/-3.8 vs. 9.0+/-2.5 ml/min/100 g LV mass), but there was significant increase in hyperemic peak diastolic velocity (0.71+/-0.26 vs. 1.08+/-0.24 m/s; p<0.01), distal LAD flow (37.8+/-11.3 vs. 53.5+/-16.1 ml/min; p<0.01) and distal LAD flow scaled for LV mass (14.3+/-5.0 vs. 23.3+/-8.5 ml/min/100 g LV mass; p<0.01). Coronary flow reserve, therefore, increased from 1.76+/-0.5 to 2.61+/-0.7.

CONCLUSIONS

Coronary flow reserve increases after AVR for aortic stenosis. This increase occurs in tandem with regression of LV hypertrophy.

Demonstration of penetrating intramyocardial coronary arteries with high-frequency transthoracic echocardiography and Doppler in human subjects

Characterization of intramyocardial coronary artery flow may offer insight into the spectrum of coronary physiology. The purposes of this study were to test the feasibility of detection and measurement of intramyocardial coronary artery flow by using high-frequency transthoracic ultrasound and to evaluate the hemodynamic and morphologic differences in intramyocardial coronary arteries between patients with echocardiographically normal myocardium and patients with diseased myocardium. In 116 subjects (age 58 +/- 19 years; male:female 67:49; 58 normal [control subjects], 40 with left ventricular hypertrophy [LVH], 18 with systolic left ventricular dysfunction [cardiomyopathy, CM]), we examined the myocardium just beneath the apical impulse window at a depth of 3 to 5 cm by using a 6- or 7-MHz centerline frequency transducer. For color Doppler examination, a special preset coronary program with a low Nyquist limit (12 to 20 cm) was used. After obtaining linear color signals, the width and length, peak and mean diastolic pulsed Doppler flow velocities, diastolic velocity time integrals, and percent duration of diastolic Doppler flow were measured. The number of linear color flow signals per square centimeter was counted in 520 different cardiac cycles, and the angles formed by their inner curvature was measured with a graduated protractor. We identified color flow Doppler signals within the myocardium having a mean width of 1.1 +/- 0.4 mm and flow direction from epicardium to endocardium in 104 (89. 7%) subjects and spectral Doppler signals in 74 (63.8%) subjects. In 33 (45.8%) subjects, only diastolic flow was detected and in 39 (54. 2%) subjects, diastolic flow was predominant with systolic reversal. Peak and mean diastolic flow velocities and velocity time integrals of spectral Doppler signal in control subjects were 26.2 +/- 8.6 cm/s, 19.0 +/- 6.3 cm/s, and 9.5 +/- 2.7 cm, respectively. There were no significant differences in width and density of linear color flow signals among the 3 groups. The color flow signals in the LVH and CM groups had a narrower angle of inner curvature (P <.005 for LVH, P <.05 for CM, respectively), and their spectral Doppler signals showed significantly higher diastolic velocities and shorter diastolic flow duration (P <.005 for LVH, P <.05 for CM, respectively) than those of the control subjects. Detection and measurement of flow signals consistent with penetrating intramyocardial coronary arteries are feasible in a high percentage of subjects by use of high-frequency transthoracic ultrasound. The findings in patients with LVH and CM suggest that there are distinct hemodynamic and morphologic departures from those with normal left ventricles that may be a consequence of disordered myocardial perfusion in diseased myocardium.

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.

Transthoracic Doppler echocardiography of normally originating coronary arteries in children

Transthoracic Doppler color flow and spectral velocity patterns of normal coronary arteries in children have not been well studied. We designed this study to evaluate coronary artery flow velocity characteristics in normal and hypertrophied hearts. Sixty-eight children with optimal two-dimensional echocardiographic images of the left coronary artery (LCA) and right coronary artery (RCA) were prospectively studied. The heart was normal in 45 children, and 23 had left and/or right ventricular hypertrophy assessed by echocardiography (mean age 5.8 versus 5.2 years, p = NS). Color flow signals were detected in the LCA in 63(92%) of the 68 children studied, and pulsed Doppler spectral waveforms were recorded in 47 (69%). The latter were recorded in 26 (58%) of 45 normal children and in 21 (91%) of 23 children with left ventricular hypertrophy. Diastolic RCA flow signals were detected mostly in those with right ventricular hypertrophy (10 of 10). Higher levels of LCA maximum diastolic velocity (42 +/- 23 versus 24 +/- 6 cm/sec, p = 0.0004), increased diastolic flow (16 +/- 15 versus 6 +/- 4 ml/min, p = 0.01), and delayed time to peak diastolic velocity expressed as a percentage of diastolic spectral duration (38% +/- 14% versus 20% +/- 8%, p = 0.0001) were observed in children with left ventricular hypertrophy than in those in normal children. A strong correlation was present between Doppler-derived LCA flow and left ventricular mass/m2 (r = 0.7, p = 0.001). In normal hearts, LCA spectral velocity pattern did not change with increasing age, but the time velocity integral became progressively larger, resulting in a strong correlation with weight (p < 0.001, r = 0.78). This study demonstrates (1) LCA flow signals can be detected and quantitated in the majority of children with and those without left ventricular hypertrophy. (2) Left ventricular hypertrophy is associated with increased LCA flow, higher diastolic velocity, and delayed peak diastolic velocity. (3) RCA flow signals are mostly detected when there is right ventricular hypertrophy. Studies on larger groups of patients are needed to further confirm our observations and to enhance understanding of coronary artery flow reserve.

Phasic coronary flow characteristics in patients with constrictive pericarditis: comparison with restrictive cardiomyopathy

BACKGROUND

Phasic coronary flow characteristics have been reported in patients with aortic valve disease and hypertrophic cardiomyopathy. The purpose of this study was to assess the differences in coronary flow characteristics between patients with constrictive pericarditis and those with restrictive cardiomyopathy.

METHODS AND RESULTS

The study populations consisted of 7 case patients with constrictive pericarditis, 8 with restrictive cardiomyopathy, and 11 control subjects with chest pain and normal coronary arteries. Five minutes after injection of 3 mg of isosorbide dinitrate, phasic coronary flow velocity patterns were analyzed in the proximal segment of the angiographically normal left anterior descending coronary artery at rest using a 0.014-in, 15-MHz Doppler guidewire. Coronary flow reserve was obtained from the ratio of adenosine-induced (0.14 mg x kg(-1) x min(-1) I.V.) hyperemic/baseline time-averaged peak velocity. Although in case patients with constrictive pericarditis and restrictive cardiomyopathy maximal hyperemic time-averaged peak velocity (21+/-8 and 31+/-17 versus 60+/-19 cm/s, respectively; P<.001) and coronary flow reserve (1.3+/-0.4 and 1.6+/-0.6 versus 3.6+/-0.4, respectively, P<.001) were significantly lower than in control subjects, there were no significant differences in these indexes between the two groups of case patients. Velocity half-time of diastolic flow velocity corrected by square root(RR), which indicates deceleration of diastolic flow, in the groups of case patients with constrictive pericarditis and restrictive cardiomyopathy was significantly less than that in control subjects (6.2+/-2.6 and 10.6+/-1.5 versus 16.9+/-2.7, respectively; P<.001); this was also significantly smaller in constrictive pericarditis than restrictive cardiomyopathy (P<.001). This index <9.5 could distinguish constrictive pericarditis from restrictive cardiomyopathy with a sensitivity of 86% and a specificity of 88%. Furthermore, time from the beginning of diastole to diastolic peak velocity corrected by square root(RR) indicating acceleration of diastolic flow velocity in constrictive pericarditis was significantly less than that in restrictive cardiomyopathy and control subjects (2.8+/-1.2 versus 4.8+/-0.8 and 4.4+/-0.6, respectively; P<.001).

CONCLUSIONS

Although coronary flow reserve is limited in both constrictive pericarditis and restrictive cardiomyopathy because of restriction of hyperemic response, rapid acceleration and more rapid deceleration of diastolic flow velocity are more characteristic in constrictive pericarditis than in restrictive cardiomyopathy.

Effect of aortic valve replacement on coronary flow velocity during metabolic stress in a patient with aortic stenosis

The effect of aortic valve replacement on coronary flow velocity during atrial pacing and papaverine-induced-resistance vessel dilatation was tested in a patient with aortic stenosis. Although systolic flow reversal disappeared early after the valve replacement, rapid atrial pacing caused myocardial ischemia with lactate production. The coronary flow reserve also remained depressed. These results suggest that the alteration in the coronary flow profile early after the aortic valve replacement does not reflect an improvement in the flow increase during metabolic stress in a patient with aortic stenosis.

Influences of aortic pressure gradient and ventricular septal thickness with systolic coronary flow in aortic valve stenosis

This study evaluates flow patterns of the left anterior descending and circumflex coronary arteries by multiplane transesophageal echocardiography in 25 patients with aortic valve stenosis, and assesses the relation between coronary flow characteristics and anatomic and hemodynamic parameters.

Comparison of relation of systolic flow of the right coronary artery to pulmonary artery pressure in patients with and without pulmonary hypertension

Systolic flow velocity is relatively predominant over diastolic velocity in the proximal right coronary artery and right ventricular branch in patients with normal systolic pulmonary artery pressure. The amount of systolic flow velocity reduction in the proximal right coronary artery and right ventricular branch is inversely related to the level of pulmonary hypertension.

Relation between symptoms and profiles of coronary artery blood flow velocities in patients with aortic valve stenosis: a study using transoesophageal Doppler echocardiography

OBJECTIVE

To analyse profiles of coronary artery flow velocity at rest in patients with aortic stenosis and to determine whether changes of the coronary artery flow velocities are related to symptoms in patients with aortic stenosis.

DESIGN

A prospective study investigating the significance of aortic valve area, pressure gradient across the aortic valve, systolic left ventricular wall stress index, ejection fraction, and left ventricular mass index in the coronary flow velocity profile of aortic stenosis; and comparing flow velocity profiles between symptomatic and asymptomatic patients with aortic stenosis using transoesophageal Doppler echocardiography to obtain coronary artery flow velocities of the left anterior descending coronary artery.

SETTING

Tertiary referral cardiac centre.

PATIENTS

Fifty eight patients with aortic stenosis and 15 controls with normal coronary arteries.

RESULTS

Adequate recordings of the profile of coronary artery flow velocities were obtained in 46 patients (79%). Left ventricular wall stress was the only significant haemodynamic variable for determining peak systolic velocity (r = -0.83, F = 88.5, P < 0.001). The pressure gradient across the aortic valve was the only contributor for explaining peak diastolic velocity (r = 0.56, F = 20.9, P < 0.001). Controls and asymptomatic patients with aortic stenosis (n = 12) did not differ for peak systolic velocity [32.8 (SEM 9.7) v 27.0 (8.7) cm/s, NS] and peak diastolic velocity [58.3 (18.7) v 61.9 (13.5) cm/s, NS]. In contrast, patients with angina (n = 12) or syncope (n = 8) had lower peak systolic velocities and higher peak diastolic velocities than asymptomatic patients (P < 0.01). Peak systolic and diastolic velocities were -7.7 (22.5) cm/s and 81.7 (17.6) cm/s for patients with angina, and -19.5 (22.3) cm/s and 94.0 (20.9) cm/s for patients with syncope. Asymptomatic patients and patients with dyspnoea (n = 14) did not differ.

CONCLUSIONS

Increased pressure gradient across the aortic valve and enhanced systolic wall stress result in characteristic changes of the profile of coronary flow velocities in patients with aortic stenosis. Decreased or reversed systolic flow velocities are compensated by enhanced diastolic flow velocities, particularly in patients with angina and syncope. This characteristic pattern of the profile of coronary artery flow velocities in patients with angina or syncope may be useful for differentiating those patients from asymptomatic patients.

Dipyridamole thallium-201 single-photon emission tomography in aortic stenosis: gender differences

Dipyridamole single-photon emission tomography (SPET) is used for the detection of coronary artery disease (CAD) and the method has also been applied in patients with aortic stenosis. This study was undertaken to establish the gender-specific normal limits of thallium-201 distribution in patients with aortic stenosis and to apply these normal limits in a larger group of patients with aortic stenosis to obtain the sensitivity and specificity for coexisting CAD. A low-dose dipyridamole protocol was used (0.56 mg/kg during 4 min). Thallium was injected 2 min later and tomographic imaging was performed. Following image reconstruction a basal, a midventricular and an apical short-axis slice were selected. The highest activity in each 6 degree segment was normalised to the maximal activity of each slice. The normal uptake for patients with aortic stenosis was obtained from ten men and ten women with aortic stenosis and a normal coronary angiography. Eighty-nine patients were prospectively evaluated. An area reduction of at least 75% in a coronary artery was considered to be a significant coronary lesion and was found in 57 (64%) patients. With gender-specific curves (-2.5 SD) sensitivity for detecting CAD was 100% and specificity was 75% in men, while sensitivity was 61% and specificity 64% in women. It is concluded that the gender-specific normal distribution of 201Tl uptake in patients with aortic stenosis, using dipyridamole SPET, yields a high sensitivity and specificity for coronary artery lesions in men but a lower sensitivity and specificity in women with aortic stenosis.