LCx Artery Research Articles

Evaluating coronary artery disease in type 2 diabetes mellitus and Other Risk Factors by angiographic study

Background: Diabetes mellitus (DM) is a metabolic and vascular illness associated with two to four times coronary artery disease (CAD) events and mortality which correlate well with fasting, postprandial plasma glucose and HbA1c level. Other factors such as aging, gender, smoking, dyslipidaemia and hypertension also play an important role in diabetic micro- and macro-vascular complications. Type 2 DM is reported now to be CAD equivalent.Patients and Methods: A cross sectional study of 118 patients including 90 males and 28 females being 63 diabetics and 55 non-diabetics over the period from March-November 2007 in Iraqi center for cardiac diseases who were underwent coronary angiographic study.Results: By angiographic study CAD was present in 92.1% of diabetic versus 89.1% in non diabetic patients. Single, double and triple vessels diseases were found in 15.9%, 22.2%, and42.9% of diabetics versus 16.4%, 21.8%, 34.5% in non diabetics respectively. DM and dyslipidaemias were proved to be independent risk factors for left circumflex artery (LCX) disease predilection (p value <0.05).Conclusion: Type 2 DM and female gender were reported to be independent risk factors for LCX and left main stem coronary arteries respectively while age, smoking, and dyslipidaemia were independent risk factors for coronary atherosclerotic . Hypertension and family history were proven to be dependent atherosclerotic risk factors and this may suggest that risk factors for the presence of CAD may differ from those affecting angiographic extent and severity. CAD was more extensive and severe in post menopausal women in this study.

Determination of ventricular isovolemic contraction solely by means of pulse contour analysis

It has been shown that the heart influences the arterial pulse contour before the aortic valve opens and aortic systole starts. In earlier work we suggested that the start of the isovolemic contraction period could be identified in the aortic and carotid arterial pressure waveform as the start of a temporary pre-systolic pressure increase (ADICS, aortic determined isovolemic contraction start), and presented the coronary retrograde flow as the most likely origin. In our current work we have shown that in 11 pigs this ADICS occurs significantly later than left ventricular systolic foot (LV systolic foot: 31.9±22.9ms, ADICS: 47.2±26.1, both relative to R-top ECG, difference inter-animal mean ± SD: 15.3 ± 6.3ms, p<0.001). Minimum pre-systolic coronary flow occurred 90.1±23.1ms after the R-top of the ECG, indicating that this flow is not the cause of the pre-systolic pressure increase, as aortic valve opening occurred shortly after this minimum flow (96.2±22.7 ms after the R-top of the ECG). Indeed, despite briefly occluding LAD, LCX and RCA coronary arteries, the pre-systolic pressure increase remained present in the aortic pressure waveform. For 8 pigs, an early peak in LV dP/dt coincided with the ADICS. Combining this observation with the LV pressure at which ADICS occurs (29.3±7.9mmHg), we propose that the abrupt closure of the mitral and tricuspid valve causes the pre-systolic aortic pressure increase.

OCT Assessment of Thin-Cap Fibroatheroma Distribution in Native Coronary Arteries

We evaluated the geographic distribution of thin-cap fibroatheromas (TCFAs) in the coronary arteries using optical coherence tomography (OCT), a high-resolution imaging modality. Plaque rupture is the most frequent cause of acute myocardial infarction (AMI). It has been recognized that TCFA is the primary plaque type at the site of plaque rupture. We performed 3-vessel OCT examinations in 55 patients: 35 AMI and 20 stable angina pectoris patients. The criteria for TCFA in an OCT image was a lipid-rich plaque with fibrotic cap thickness <65 microm. The distance between each TCFA location and the respective coronary artery ostium was measured with motorized OCT imaging pullback. The total length of all 3 coronary arteries imaged by OCT pullbacks was 82 +/- 21 mm in the left anterior descending coronary artery (LAD), 67 +/- 26 mm in the left circumflex coronary artery (LCx), and 104 +/- 32 mm in the right coronary artery (RCA). OCT detected 94 TCFAs in 165 coronary arteries. The minimum fibrous-cap thickness of TCFAs was 57.4 +/- 5.4 microm in AMI patients, and 55.9 +/- 7.3 microm in stable angina pectoris patients (p = 0.4). Of the total of 94 TCFAs, 28 were detected in the LAD, 18 in the LCx, and 48 in the RCA. Most LAD TCFAs were located between 0 and 30 mm from the LAD ostium (76%). Conversely, LCx and RCA TCFAs were evenly distributed throughout the entire coronary length. The clustering of the TCFAs was similar in culprit segments as compared with nonculprit segments. In AMI patients, most LAD TCFAs were distributed near side branches, mainly positioned opposite the side branch bifurcation. Three-vessel OCT imaging showed that TCFAs tend to cluster in predictable spots within the proximal segment of the LAD, but develop relatively evenly in the LCx and RCA arteries.

Distal left circumflex coronary artery flow reserve recorded by transthoracic Doppler echocardiography: a comparison with Doppler-wire

BackgroundCoronary flow reserve (CFR) recording by means of transthoracic echocardiography (TTDE) in all the main distal coronary arteries is a challenge for advanced echocardiography. Validation studies of TTDE versus Doppler-wire (DW) recordings are available for Left Anterior Descending artery (LAD) and the Posterior Descending coronary artery (PD), but lacking for the more technically challenging Left Circumflex coronary artery (LCx).AimTo evaluate the reliability of TTDE in assessing CFR in LCx when compared to the intracoronary Doppler flow-wire gold standard.Methodswe evaluated 5 patients (age = 60 ± 9 years, 5 males) on LCx by TTDE and invasive CFR assessment. TTDE recording was performed using a low-frequency probe, with a four-chamber as a guiding 2D view. The 2 tests were performed on different days and in random order within 48 hours in a blind fashion. Vasodilator stimulus was adenosine, intravenously (140 γ/kg/min × 3–6 min) for TTDE and intracoronary (40 γ bolus) for DW recordings.ResultsCFR values on LCx ranged from 1.9 to 2.8 for DW, and from 2.0 to 3.0 for TTDE, with an overall correlation of R = 0,85 (p = 0,06); normal (CFR > 2.5) or abnormal (CFR < 2.5) value was concordantly identified by the 2 techniques in 4 out 5 cases (80%).ConclusionCFR of LCx artery can be obtained noninvasively with TTDE.

&lt;b&gt;Comparison of the Effect of the ATP-Sensitive Potassium Channel Opener YM934 With That of Nitroglycerin on Impaired Coronary Circulation in Dogs&lt;/b&gt;

We compared the effect of an ATP-sensitive potassium channel opener, YM934, with that of nitroglycerin (NTG) on impaired coronary circulation in dogs. Coronary stenosis was produced in 7 dogs by placing a hydraulic occluder around the proximal left circumflex coronary (LCx) artery and abolishing reactive hyperemia to compromise the LCx flow. The following parameters were measured: the aortic pressure, LCx flow velocity, LCx vessel diameter, LCx peripheral pressure, and segment length in the LCx area. Subsequently, we occluded the LCx artery for 15 seconds and measured the recovery-interval (time required for the segment shortening to return to the preocclusion value). The measurements were recorded under three study conditions: (1) at baseline without LCx stenosis; (2) with LCx stenosis under NTG infusion (3 microg/Kg/min); and (3) with LCx stenosis after intravenous administration of YM934 (0.3 microg/kg). The heart rate and aortic pressure were similar under the three study conditions. Mean LCx flow velocity and segment shortening did not significantly change either. However, LCx peripheral pressure decreased after the induction of stenosis (P < 0.05) and showed no response to either NTG or YM934. YM934 administration significantly increased LCx flow in the presence of LCx stenosis, (P < 0.05), whereas NTG infusion did not. YM934 significantly shortened the recovery-interval of the segment shortening after 15-sec LCx occlusion (P < 0.05), whereas NTG did not. These findings suggest that YM934 improves coronary blood flow and prevents myocardial ischemic damage in severely impaired coronary circulation.

Exercise training restores adenosine-induced relaxation in coronary arteries distal to chronic occlusion.

We previously reported that canine collateral-dependent coronary arteries exhibit impaired relaxation to adenosine but not sodium nitroprusside. In contrast, exercise training enhances adenosine sensitivity of normal porcine coronary arteries. These results stimulated the hypothesis that chronic coronary occlusion and exercise training produce differential effects on cAMP- versus cGMP-mediated relaxation. To test this hypothesis, Ameroid occluders were surgically placed around the proximal left circumflex coronary artery (LCx) of female Yucatan miniature swine 8 wk before initiating sedentary or exercise training (treadmill run, 16 wk) protocols. Relaxation to the cAMP-dependent vasodilators adenosine (10(-7) to 10(-3) M) and isoproterenol (3 x 10(-8) to 3 x 10(-5) M) were impaired in collateral-dependent LCx versus nonoccluded left anterior descending (LAD) arterial rings isolated from sedentary but not exercise-trained pigs. Furthermore, adenosine-mediated reductions in simultaneous tension and myoplasmic free Ca(2+) were impaired in LCx versus LAD arteries isolated from sedentary but not exercise-trained pigs. In contrast, relaxation in response to the cAMP-dependent vasodilator forskolin (10(-9) to 10(-5) M) and the cGMP-dependent vasodilator sodium nitroprusside (10(-9) to 10(-4) M) was not different in LCx versus LAD arteries of sedentary or exercise-trained animals. These data suggest that chronic occlusion impairs receptor-dependent, cAMP-mediated relaxation; receptor-independent cAMP- and cGMP-mediated relaxation were unimpaired. Importantly, exercise training restores cAMP-mediated relaxation of collateral-dependent coronary arteries.

Identification of the Occluded Artery in Patients with Myocardial Ischemia Induced by Prolonged Percutaneous Transluminal Coronary Angioplasty Using Traditional vs Transformed ECG-Based Indexes

We have studied the spatial properties of ischemic changes as induced by prolonged angioplasty and how the changes are related to different ECG indexes. Indexes based on measurements at specific points in time (ST level at J + 60 ms point, maximal T wave amplitude and position, QT interval, and QRS duration) and global indexes (based on the Karhunen–Loève transform and applied to the QRS complex, ST–T complex, ST segment, and T wave), considering both repolarization and depolarization information, were analyzed. The changes during the occlusion period of the different indexes were used as variables in a multivariate discriminant analysis to determine which indexes showed the best discrimination of the three major occlusion sites (corresponding to LAD, RCA, and LCX coronary arteries). Occlusions in LCX artery were the most difficult to classify. With three local indexes (ST60 level measured in lead V3, T wave amplitude in I, and ST60 in III) it was possible to correctly classify 76% of patients by the occlusion site, and with three KLT-derived indexes (first-order KLT index for ST-T complex in I and for QRS in leads V3 and I) 83% of correct classification was obtained. Using six indexes for local and KLT-derived indexes the correct classification was increased to 85 and 90% of patients, respectively. The use of different ECG indexes (from different intervals) on quasiorthogonal leads permitted the identification of the occluded artery in patients undergoing PTCA and may be extended to more general use.

Does use of intravascular ultrasound accelerate arteriopathy in heart transplant recipients?

Background Intravascular ultrasound (IVUS) is a sensitive method for assessing allograft vasculopathy in heart transplant recipients, but it is not known whether this instrumentation traumatizes the transplanted arteries and affects progression of arteriopathy. Methods and Results Yearly coronary angiograms were obtained in 86 patients who underwent heart transplantation between January 1991 and May 1995. Patients were divided into 3 groups: (1) no IVUS performed after transplantation (group 1, n = 47); (2) IVUS of the left anterior descending artery (LAD) performed only at year 1 (group 2, n = 13); and (3) IVUS of the LAD performed at both baseline (within 2 months after transplantation) and year 1 after transplantation (group 3, n = 26). Coronary angiography measurements of lumen diameter were performed at 5 segments along the length of the LAD and left circumflex artery (LCX) from baseline through the second-year studies except in group 2, which did not receive a baseline angiogram; IVUS measurements were obtained at 10 cross sections from each artery. At baseline, there was no significant difference in vessel diameter for either the LAD or the LCX artery between the IVUS (group 3) and no IVUS (group 1) groups. Within each group, the lumen of both the LAD and LCX narrowed from baseline to year 1 (group 1: 3.3 ± 0.6 mm to 2.8 ± 0.5 mm in LAD, P = .001; 3.3 ± 0.6 mm to 3.0 ± 0.5 mm in LCX, P = .006; group 3: 3.5 ± 0.7 mm to 3.1 ± 0.6 mm in LAD, P = .01; 3.1 ± 0.6 mm to 2.8 ± 0.5 mm in LCX, P = 0.07), but there were no significant differences between the instrumented artery (LAD) and control artery (LCX) or further changes observed at year 2. There were also no significant differences in the percent reductions at year 1 and year 2 between arteries or between groups. By IVUS, from baseline to year 1 in group 3, the plaque cross-sectional area (CSA) increased (1.6 ± 1.9 to 2.3 ± 1.7 mm 2, P < .0001), the lumen CSA decreased (12.7 ± 3.7 to 11.7 ± 3.3 mm 2, P = .04), and the maximum lumen diameter decreased (4.2 ± 0.6 to 4.0 ± 0.6 mm, P = .04). Conclusions The use of IVUS is not associated with acceleration of arteriopathy in heart transplantation recipients. Luminal narrowing occurs predominantly during the first year after transplantation. There was no significant change in lumen dimensions during the second year. (Am Heart J 1999;138:358-63.)

Intravascular ultrasound (IVUS) examination reverses therapeutic decision from percutaneous intervention to a surgical approach in patients with alterations of the left main stem.

Intravascular ultrasound (IVUS) represents a new method to assess vessel lumen and wall morphology. To prospectively evaluate the usefulness of IVUS for further therapeutic decisions in left main stem (LM) lesions with unclear angiographic definition, this study was launched. We studied 56 patients with significant stenosis of the LAD and/or LCX arteries and questionable LM morphology. 30-MHz IVUS catheters with 2.9 or 3.2 F outer diameters were used. A significant luminal reduction of the left main stem was defined as an area stenosis greater than 50% or a minimal luminal diameter smaller than 3 mm as determined by IVUS. 36 of 56 patients (61%) fulfilled these criteria. Additionally, 12 patients showed a ruptured plaque within the LM. 30 of these 36 patients were originally thought to be candidates for angioplasty. After positive IVUS 34 of these 36 patients were sent to surgery. No perioperative ischemic complications occurred. In angiographically unclear left main stem findings. IVUS establishes a definitive diagnosis. After IVUS confirmation of significant left main stem pathology operative management should be the preferred approach as compared to transluminal coronary interventions. However, prospective randomized studies are needed to define the most efficient approach.

Basic fibroblast growth factor improves myocardial function in chronically ischemic porcine hearts.

The effect of basic fibroblast growth factor (bFGF) administration on regional myocardial function and blood flow in chronically ischemic hearts was studied in 26 pigs instrumented with proximal circumflex coronary artery (LCX) ameroid constrictors. In 13 animals bFGF was administered extraluminally to the proximal left anterior descending (LAD) and LCX arteries with heparin-alginate beads and 13 other animal served as controls. bFGF-treated pigs showed a fourfold reduction in left ventricular infarct size compared to untreated controls (infarct size: 1.2 +/- 0.4% vs. 5.1 +/- 1.3% of LV mass, mean +/- SEM, P < 0.05). Percent fractional shortening (% FS) in the LCX area at rest was reduced compared with the LAD region in both bFGF and control pigs. However, there was better recovery in the LCX area after rapid pacing in bFGF-treated pigs (% FSLCX/% FSLAD, 22.9 +/- 7.3%-->30.5 +/- 8.5%, P < 0.05 vs. prepacing) than in controls (16.0 +/- 7.8%-->14.3 +/- 7.0%, P = NS). Furthermore, LV end-diastolic pressure rise with rapid pacing was less in bFGF-treated than control pigs (pre-pacing; pacing; post-pacing, 10 +/- 1; 17 +/- 3; 11 +/- 1* mmHg vs 10 +/- 1; 24 +/- 4; 15 +/- 1 mmHg, *P < 0.05 vs. control). Coronary blood flow in the LCX territory (normalized for LAD flow) was also better during pacing in bFGF-treated pigs than in controls. Thus, periadventitial administration of bFGF in a gradual coronary occlusion model in pigs results in improvement of coronary flow and reduction in infarct size in the compromised territory as well as in prevention of pacing-induced hemodynamic deterioration.

Coronary artery occlusion extends perfusion territory boundaries through microvascular collaterals.

Simultaneous in vivo infusions of two different colored 10 microns microsphere suspensions into the left anterior descending (LAD; red spheres) and left circumflex (LCx; blue spheres) coronary arteries of nine anesthetized dogs identified a specific region of canine myocardium perfused by both arterial branches. Subsequently, the LAD was ligated and a third (green) set of micropheres was infused into the patent LCx artery. Analysis of 40 microns serial sections of tissue revealed interface zones with capillaries perfused by both arteries. The first zone, defined as the Interface Transistion Zone (ITZ) was formed by an intermingling of microvessels supplied by the parent arteries of the adjacent perfusion territories; it separated tissue containing only one or the other colored microspheres. Another zone, defined as the Boundary Watershed Zone was located within the ITZ and had capillaries containing both red and blue microspheres. The width of ITZ was 53377 +/- 817 microns (mean +/- SD), and the width of the BWZ was 3358 +/- 618 microns. Green microspheres, infused into the LCx following coronary occlusion were also found in the ITZ and BWZ. Furthermore, capillaries perfused exclusively by the LAD before occlusion (tissue with red but not blue microspheres) adjacent to the perfusion interface contained green microspheres as well as red/green aggregates, indicating lateral extension of the LCx perfusion territory. This extension of the LCx territory was quantitated by comparing the location at which densities of green microspheres or green/red aggregates decreased abruptly compared to the location of the original ITZ and BWZ boundaries, respectively. Results showed that LAD occlusion caused a 24% expansion of the ITZ and a 48% expansion of the BWZ. In addition, all expansions were significantly greater in subepicardial compared to subendocardial regions (p < 0.001). These results clearly demonstrate the capability of microvascular anastomoses in providing blood flow to the periphery of an ischemic region. Furthermore, the perfusion interface is labile and might be amenable to manipulation.

Functional significance of alpha-adrenergic receptors in mature coronary collateral circulation of dogs.

There is little information on the functional significance of alpha-adrenergic receptors in the dog's coronary collateral circulation. Accordingly, we investigated the effects of infusion of either norepinephrine (NE) or B-HT 920 (BHT), an alpha 2-adrenergic agonist, on vascular resistance of coronary collaterals in chloralose-anesthetized dogs 2-3 mo after placement of an Ameroid constrictor around the left circumflex coronary (LCX) artery. To accomplish this, the vagotomized left ventricle was autoperfused through the left main coronary ostium using a servo-controlled constant-pressure pump. Pressures of the left anterior descending (LAD) and peripheral LCX arteries were measured, and regional blood flow in LAD and LCX regions were determined with radioactive microspheres before and during NE infusion in the unblocked condition, following beta-adrenergic and beta + alpha 1-adrenergic blockade with the use of propranolol and prazosin, respectively. The same parameters were also measured before and during BHT infusion following beta-adrenergic and beta + alpha 2-adrenergic blockade with the use of propranolol and idazoxan, respectively. In the unblocked condition, NE reduced LAD, LCX, and collateral resistance by 43, 50, and 31%, respectively. After beta-adrenergic blockade, NE increased LAD resistance (29%) but did not alter LCX or collateral resistance. The increase in LAD resistance was abolished following alpha 1-adrenergic blockade. BHT increased vascular resistance in LAD, LCX, and collateral circulations by 35, 29, and 45%, respectively. Selective alpha 2-adrenergic blockade significantly attenuated the vasoconstrictor response to BHT.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous angina during serial resting thallium-201 myocardial scintigraphy

severely narrowed by an atherosclerotic plaque. These investigators suggested that the significance of such stenosis of the “right main” coronary artery was equivalent to that of critical narrowing of the LMCA in patients with normal coronary artery anatomy, and termed this lesion “the true left main equivalent.” To our knowledge, antemortem diagnosis and treatment of right main coronary artery stenosis has not previously been reported. In our patient, the LCX artery was small; indeed, much of the left ventricular myocardium normally supplied by the LCX was supplied by the unusually large RCA rather than by the anomalous LCX itself. It is evident that the superiority of surgical over medical therapy for right main coronary artery disease will not be demonstrated by a randomized, controlled study, as it has for LMCA disease4; we feel, nevertheless, that the analogy with LMCA disease is compelling enough to warrant coronary artery bypass surgery in patients with significant right main coronary artery stenosis.