Coronary artery diameter can be assessed reliably with transthoracic echocardiography

We studied whether diameters of coronary arteries can be measured accurately with the use of transthoracic echocardiography (TTE). By knowing the anatomic diameter of the coronary artery together with coronary flow velocity it is possible to measure coronary flow volume more precisely by TTE. However, the suitability of TTE for measurement of diameters of all main epicardial coronary arteries has not been systematically validated. We measured the diameters of the left main (LM), left anterior descending (LAD), left circumflex (LCX), and right coronary arteries (RCA) with the use of TTE [manual two-dimensional (2D), color-Doppler, and automated 2D analysis] in 30 patients who had normal coronary anatomy. We compared these diameters to those measured with quantitative coronary angiography (QCA). We could measure diameters of LM, LAD, LCX, and RCA by TTE in up to 37%, 63%, 7%, and 60% of patients, respectively. The overall correlation coefficients between TTE and QCA measurements were 0.83 (P < 0.01) with manual 2D analysis, 0.82 (P < 0.01) with automated 2D analysis, and 0.94 (P < 0.01) with a color-Doppler-based analysis. Interobserver variability of TTE measurements was low (coefficient of variation 5.4 +/- 4.6-7.5 +/- 8.8%). TTE is an accurate method to evaluate coronary artery diameter in patients with healthy coronary arteries.     

Altered calcium sensitivity contributes to enhanced contractility of collateral-dependent coronary arteries.

Coronary arteries distal to chronic occlusion exhibit enhanced vasoconstriction and impaired relaxation compared with nonoccluded arteries. In this study, we tested the hypotheses that an increase in peak Ca(2+) channel current density and/or increased Ca(2+) sensitivity contributes to altered contractility in collateral-dependent coronary arteries. Ameroid occluders were surgically placed around the proximal left circumflex coronary artery (LCX) of female miniature swine. Segments of epicardial arteries ( approximately 1 mm luminal diameter) were isolated from the LCX and nonoccluded left anterior descending (LAD) arteries 24 wk after Ameroid placement. Contractile responses to depolarization (10-100 mM KCl) were significantly enhanced in LCX compared with size-matched LAD arterial rings [concentration of KCl causing 50% of the maximal contractile response (EC(50)); LAD = 41.7 +/- 2.3, LCX = 34.3 +/- 2.7 mM]. However, peak Ca(2+) channel current was not altered in isolated smooth muscle cells from LCX compared with LAD (-5.29 +/- 0.42 vs. -5.68 +/- 0.55 pA/pF, respectively). Furthermore, whereas half-maximal activation of Ca(2+) channel current occurred at nearly the same membrane potential in LAD and LCX, half-maximal inactivation was shifted to a more positive membrane potential in LCX cells. Simultaneous measures of contractile tension and intracellular free Ca(2+) (fura 2) levels in arterial rings revealed that significantly more tension was produced per unit change in fura 2 ratio in LCX compared with LAD in response to KCl but not during receptor-agonist stimulation with endothelin-1. Taken together, our data indicate that coronary arteries distal to chronic occlusion display increased Ca(2+) sensitivity in response to high KCl-induced depolarization, independent of changes in whole cell peak Ca(2+) channel current. Unaltered Ca(2+) sensitivity in endothelin-stimulated arteries suggests more than one mechanism regulating Ca(2+) sensitization in coronary smooth muscle.     

Pronounced HR variability after exercise in inferior ischemia: evidence that the cardioinhibitory vagal reflex is invoked by exercise-induced inferior ischemia

Potent cardioinhibitory vagal reflex resulting in bradycardia and hypotension has been observed under particular conditions of transmural inferior ischemia and its reperfusion, such as those observed with acute infarction. However, whether exercise-induced ischemia with ST depressions that is subendocardial and that might be recurrently experienced in daily activities can evoke this reflex remains unknown. In patients with exercise-induced ST depressions due to either inferior [right coronary artery stenosis (RCA), n = 52] or anterior ischemia [left anterior descending artery stenosis (LAD), n = 51], we evaluated post exercise vagal activity (from 0 to 6 min) by the time constant of heart rate (HR) decay and HR variability by 30-s averages of the absolute values of successive RR interval differences (DeltaRR). Exercise parameters were similar between groups. The time constant was slightly but significantly shorter in RCA than LAD patients (79 +/- 24 vs. 93 +/- 29 s, P < 0.01). More significantly, DeltaRR early after exercise (0.5-2.5 min) was approximately twofold greater in RCA than LAD patients (from +76 to +118%, P < 0.001), indicating pronounced vagal activity stimulated by inferior ischemia. Revascularization prolonged the time constant (P < 0.05) and attenuated recovery DeltaRR in RCA patients (P < 0.05, n = 10) but did not change both parameters in LAD patients (n = 12). As well as acute inferior infarction, exercise-induced inferior subendocardial ischemia, which might recurrently occur in daily activities, activates the cardioinhibitory reflex. These new findings must be taken into account in interpreting vagal activity in patients with coronary artery disease.     

Assessment of collateral artery function and growth in a pig model of stepwise coronary occlusion

Therapeutic stimulation of collateral artery growth is a promising approach for treatment of cardiovascular diseases. Unfortunately, translation into clinical practice yet remains cumbersome. Cardiovascular physiology and anatomy are major determinants of vascular growth processes. Hence, large-animal models are needed to improve clinical translatability of preclinical research. Furthermore, acute complete occlusions are mostly applied in experimental research, whereas stepwise occlusions are more often observed in human disease. We developed a model of coronary collateral artery growth in which 1) the artery is occluded in a step wise approach, and 2) effects of local treatment can be measured individually for each supplying coronary vessel. A hemodynamically relevant stenosis was created by implantation of a tapered stent at day 0 (d0) in the left circumflex artery (LCX), followed by complete arterial occlusion at day 14 (d14). Fluorescent microspheres were injected for demarcation of perfusion territories at each time point. Three and four weeks after induction of stenosis, collateral conductance measurements were performed for each coronary artery separately using differently labeled fluorescent microspheres. Postmortem angiography after acute LCX occlusion confirmed the presence of preexistent coronary anastomoses in the pig. The tapered stent created a hemodynamically significant stenosis immediately postplacement (fractional flow reserve, 0.70 ± 0.03). Between day 21 and 28, collateral conductance significantly increased in both the left anterior descending (LAD) and the right coronary artery (RCA)-supplied, collateral-dependent territories (LAD d21, 0.77 ± 0.14; LAD d28, 1.35 ± 0.12; RCA d21, 0.88 ± 0.29; RCA d28, 1.70 ± 0.16 ml · min(-1) · g(-1) · 100 mmHg(-1)), indicating collateral artery growth. We here describe a new translational minimally invasive model of coronary collateral artery growth in pigs, according to a defined protocol of LCX-stenosis and subsequent occlusion, allowing preclinical evaluation of arteriogenic therapies.     

Coronary artery embolization in closed-chest canines using flexible radiopaque plugs

A new technique induces localized myocardial infarction in closed-chest dogs by placing discrete plugs in coronary arteries without using cumbersome coaxial catheters or guide wires. Flexible plugs, essential to this method, are formed by extruding a dental impression polymer, rendered radiopaque with sodium iodide, into spaghetti-like strands. Segments of these strands can be injected through a catheter into a selected coronary artery. Contact with blood or saline causes plugs to swell. The mean increase in plug diameter due to swelling was 27 +/- 20%. Eight anesthetized dogs were embolized via carotid approach [6 left anterior descending (LAD), 1 left circumflex (LCX), and 1 LAD and LCX]. Plug positions were monitored fluoroscopically. One animal died at 2 days postembolization. The remaining seven dogs were killed after 14-37 days. Autopsies showed complete vessel occlusion and localized infarction. Infarcts resulting from coronary artery occlusion with one, two, or three plugs involved 2-26% of the left ventricular mass.     

Dynamics of human coronary arterial motion and its potential role in coronary atherogenesis

Mechanical forces have been widely recognized to play an important role in the pathogenesis of atherosclerosis. Since coronary arterial motion modulates both vessel wall mechanics and fluid dynamics, it is hypothesized that certain motion patterns might be atherogenic by generating adverse wall mechanical forces or fluid dynamic environments. To characterize the dynamics of coronary arterial motion and explore its implications in atherogenesis, a system was developed to track the motion of coronary arteries in vivo, and employed to quantify the dynamics of four right coronary arteries (RCA) and eight left anterior descending (LAD) coronary arteries. The analysis shows that: (a) The motion parameters vary among individuals, with coefficients of variation ranging from 0.25 to 0.59 for axially and temporally averaged values of the parameters; (b) the motion parameters of individual vessels vary widely along the vessel axis, with coefficients of variation as high as 2.28; (c) the LAD exhibits a greater axial variability in torsion, a measure of curve "helicity," than the RCA; (d) in comparison with the RCA, the LAD experiences less displacement (p = 0.009), but higher torsion (p = 0.03). These results suggest that: (i) the variability of certain motion parameters, particularly those that exhibit large axial variations, might be related to variations in susceptibility to atherosclerosis among different individuals and vascular regions; and (ii) differences in motion parameters between the RCA and LAD might relate to differences in their susceptibility to atherosclerosis.     

False-negative myocardial scintigraphy in balanced three-vessel disease,revealed by coronary pressure measurement

In nuclear perfusion imaging of the myocardium, a false-negative test result in patients with balanced three-vessel disease is a well-known pitfall. This paper describes a patient with typical chest pain and a negative myocardial perfusion scintigram. At coronary angiography, intermediate stenoses in the left anterior descending (LAD), left circumflex (LCX), and right coronary (RCA) arteries were present. Fractional flow reserve, measured by coronary pressure measurement, was 0.54, 0.56, and 0.66 respectively for the LAD, LCX, and RCA, unequivocally demonstrating the presence of balanced three-vessel disease. The patient underwent successful bypass surgery and remained event-free thereafter.     

Exercise training improves endothelium-mediated vasorelaxation after chronic coronary occlusion.

The present study evaluated combined effects of chronic coronary occlusion and exercise training on endothelial function. Gradual occlusion was produced by placement of an ameroid constrictor around the proximal left circumflex (LCX) coronary artery of female swine. Two months after placement of the ameroid, animals were restricted to their pens or exercise trained for 16 wk. Epicardial arteries (>500 microm ID) were isolated from the collateral-dependent LCX coronary artery distal to the occlusion and the nonoccluded left anterior descending (LAD) coronary artery. Bradykinin- and ADP-mediated relaxation of LCX and LAD coronary arteries was enhanced after exercise training. Inhibition of nitric oxide synthase with N(G)-nitro-L-arginine methyl ester decreased bradykinin- and ADP-mediated relaxation in LCX and LAD myocardial regions. Importantly, combined inhibition of effects of endothelium-derived hyperpolarizing factor with increased extracellular K(+) (20-30 mM) and nitric oxide synthase completely abolished coronary LAD and LCX relaxation to bradykinin. Our data indicate that exercise training improves endothelium-mediated relaxation of arteries isolated after chronic coronary artery occlusion, likely as a result of enhanced production of nitric oxide and endothelium-derived hyperpolarizing factor.     

Coronary artery flow measurement using navigator echo gated phase contrast magnetic resonance velocity mapping at 3.0 T

A validation study and early results for non-invasive, in vivo measurement of coronary artery blood flow using phase contrast magnetic resonance imaging (PC-MRI) at 3.0T is presented. Accuracy of coronary artery blood flow measurements by phase contrast MRI is limited by heart and respiratory motion as well as the small size of the coronary arteries. In this study, a navigator echo gated, cine phase velocity mapping technique is described to obtain time-resolved velocity and flow waveforms of small diameter vessels at 3.0T. Phantom experiments using steady, laminar flow are presented to validate the technique and show flow rates measured by 3.0T phase contrast MRI to be accurate within 15% of true flow rates. Subsequently, in vivo scans on healthy volunteers yield velocity measurements for blood flow in the right, left anterior descending, and left circumflex arteries. Measurements of average, cross-sectional velocity were obtainable in 224/243 (92%) of the cardiac phases. Time-averaged, cross-sectional velocity of the blood flow was 6.8+/-4.3cm/s in the LAD, 8.0+/-3.8cm/s in the LCX, and 6.0+/-1.6cm/s in the RCA.     

全数字化血管造影机应用探讨

目的探讨应用全数字化血管造影机检查的图像质量及X射线剂量。方法500人次冠状动脉造影检查,常规拍摄左前斜位加头位或足位,右前斜位加头位或足位,必要时加摄蜘蛛位。结果采取支架植入治疗左前降支狭窄92例,左回旋支狭窄28例及右冠状动脉狭窄45例,冠状动脉微细血管显示佳,管腔内血栓、血管内膜撕裂、支架等显示清晰。结论全数字化血管造影机采集的图像佳,X线剂量较低。     

Catecholamine release and ventricular arrhythmias during coronary occlusion and reperfusion in the dog

In anesthetized dogs, 60-min occlusions of either the proximal (n = 14), distal (n = 8) left circumflex (LCX), or left anterior descending (LAD, n = 10) arteries were followed by reperfusion. Coronary sinus and aortic norepinephrine and epinephrine plasma concentrations were measured. The ventricular arrhythmias were ventricular premature depolarizations (VPDs), unsustained ventricular tachycardia (VT) (greater than or equal to 3 and less than 20 VPDs), sustained VT (greater than or equal to 20 VPDs), and ventricular fibrillation (VF). A gradual twofold increase (p less than 0.05) in myocardial norepinephrine overflow followed occlusion in all three groups. The increases in the amounts of norepinephrine released in the coronary sinus blood during reperfusion were significant and proportional to the size of the occluded area: proximal LCX, from 0.236 +/- 0.038 to 1.528 +/- 0.490 ng/mL of plasma (p less than 0.001); LAD, from 0.180 +/- 0.027 to 0.795 +/- 0.286 ng/mL (p less than 0.05); distal LCX, from 0.215 +/- 0.039 to 0.404 +/- 0.110 ng/mL (p less than 0.05). Aortic epinephrine concentrations were significantly increased only by LAD occlusion; at 15 min, the value had increased to 0.187 +/- 0.053 ng/mL from an initial value of 0.069 +/- 0.029 ng/mL (p less than 0.001). Two phases of ventricular arrhythmias followed both occlusion and reperfusion. Phase 1 postocclusion was characterized by VPDs and phase 2 by VPDs and unsustained VT. Sustained VT was seen only in phase 1 postreperfusion, whereas unsustained VT was seen in phase 2. VF was seen in 50, 35, and 25% of the dogs with proximal LCX, LAD, and distal LCX occlusion and reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Measurement of the flow in coronary artery bypass grafts

The aim of our study was to measure the flow in coronary artery bypass grafts and to compare the flow between two groups of patients. In group A the arterial revascularization was performed with both internal thoracic arteries using as a Y graft and in group B conventional revascularization using left internal thoracic artery (ITA) attached to the left anterior descending artery (LAD) and venous grafts to the other branches of the left coronary artery was performed. The flow in all grafts was measured at six time points during the operation. The cumulative flow at the end of the operation in the group A (arterial Y graft) was 51.8 +/- 24.5 ml/min and in group B (conventional technique) it was 96.8 +/- 41.1 ml/min (p < 0.05). The flow in left ITA to LAD was similar in both groups (27.3 +/- 15.9 ml/min and 26.3 +/- 16.1 ml/min in group A and B). The flow in right ITA (25.2 +/- 18.4 ml/min) was significantly lower than in venous grafts (72.5 +/- 45.5 ml/min). The calculated flow reserve was 2.2 in group A and 2.1 in group B. We found that the cumulative flow in arterial Y graft was lower in comparison with conventional revascularization. This is due to the lower flow in the right ITA branch of the Y graft compared to venous grafts. However based on clinical results, we can postulate that the flow in the Y graft is sufficient to meet the demand of the myocardium originally supplied by the left coronary artery.     

A single center experience with the newly designed R Stent in small coronary vessels

BACKGROUND: Over the past 10 years stents have been used more frequently for the treatment of de novo coronary artery stenosis. Initally these devices were used primarily in coronary arteries with diameters ranging from 3.0 to 4.0 mm. Traditionally, coronary arteries less than 3.0 mm in diameter were treated with only balloon angioplasty, due to the unavailablity of flexible, low profile, small diameter stents. In the past three years, many stents have been designed to be implanted in small coronary arteries. OBJECTIVE: The objective of this study was to evaluate the safety and feasiblity of the R Stent in patients with coronary lesions located in coronary arteries with a reference diameter 2.5-3.0 mm. METHODS AND RESULTS: Between November 1998 and September 1999, 32 patients with stable (37%) and unstable (63%) angina treated with the R Stent were included in this study. The treated lesions were in the right coronary artery (RCA) (n = 13), left cirumflex coronary artery (LCX) (n = 10), and left anterior descending coronary artery (LAD) (n = 9). Of these lesions thirteen were anatomically complex. Stent deployment was successful in 97% with one crossing failure in a patient with a vessel tortuosity of greater than 75 degrees of the circumflex artery. No post-procedual major adverse cardiac and cerebrovascular event (MACCE) occurred within 30 days of stent implantation. After the procedure, patients were scheduled for a two-week telephone follow-up and a one-month clinical evaluation. At 30 days, only one patient (3%) experienced the recurrence of angina Canadian cardiovascular society classification ((CCS) Class 2). All other patients were event and angina free. CONCLUSION: This first clinical experience in patients with small vessel disease shows that the use of the R stent is safe and feasible with low rates of acute stent thrombosis.     

Diameter-dependent axial prestretch of porcine coronary arteries and veins

The pressure-diameter relation (PDR) and the wall strain of coronary blood vessels have important implications for coronary blood flow and arthrosclerosis, respectively. Previous studies have shown that these mechanical quantities are significantly affected by the axial stretch of the vessels. The objective of this study was to measure the physiological axial stretch in the coronary vasculature; i.e., from left anterior descending (LAD) artery tree to coronary sinus vein and to determine its effect on the PDR and hence wall stiffness. Silicone elastomer was perfused through the LAD artery and coronary sinus trees to cast the vessels at the physiologic pressure. The results show that the physiological axial stretch exists for orders 4 to 11 (> 24 μm in diameter) arteries and orders -4 to -12 (>38 μm in diameter) veins but vanishes for the smaller vessels. Statistically, the axial stretch is higher for larger vessels and is higher for arteries than veins. The axial stretch λ(z) shows a linear variation with the order number (n) as: λ(z) = 0.062n + 0.75 (R(2) = 0.99) for artery and λ(z) = -0.029n + 0.89 (R(2) = 0.99) for vein. The mechanical analysis shows that the axial stretch significantly affects the PDR of the larger vessels. The circumferential stretch/strain was found to be significantly higher for the epicardial arteries (orders 9-11), which are free of myocardium constraint, than the intramyocardial arteries (orders 4-8). These findings have fundamental implications for coronary blood vessel mechanics.     

Coronary endothelial dysfunction from ischemia and reperfusion: effect of reactive oxygen metabolite scavengers

Using anesthetized mongrel dogs exposed to 60 min of ligation of the left anterior descending coronary artery followed by 60 min of reperfusion, we examined the effect of superoxide dismutase (SOD) and dimethylthiourea (DMTU) on evidence of endothelial injury in coronary rings studied in vitro. In 13 dogs treated with saline rings from the normal left circumflex coronary artery (LCF) relaxed by 98 +/- 4% when exposed to 10(-5) M acetylcholine whereas rings from the left anterior descending coronary artery (LAD) relaxed by 79 +/- 7% (p less than 0.05). In the same rings maximum relaxation with the ionophore A23187 was 107 +/- 5% versus 87 +/- 8% (p less than 0.05) for the LCF and the LAD, respectively. Comparisons of concentration-response curves through a range of doses of both acetylcholine and A23187 revealed significant differences for both vasodilators between the LCF and the LAD (p less than 0.01 for each). Nine dogs were treated with bovine SOD infused in the left atrium the last 20 min of ligation and throughout reperfusion (140 units/kg/min) and six other dogs were treated with DMTU 500 mg/kg i.v. given the last 30 min of the ligation period. Neither SOD nor DMTU prevented endothelial injury in the LAD. Despite pretreatment with these agents, there were significant reductions in maximum relaxation and in total concentration-response curves in the LAD as compared with the results in rings from the LCF with both acetylcholine and A23187. There were normal responses to nitroprusside in both the LCF and LAD in all three experimental groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Electrotonic remodeling following myocardial infarction in dogs susceptible and resistant to sudden cardiac death.

Passive electrical remodeling following myocardial infarction (MI) is well established. These changes can alter electrotonic loading and trigger the remodeling of repolarization currents, a potential mechanism for ventricular fibrillation (VF). However, little is known about the role of passive electrical markers as tools to identify VF susceptibility post-MI. This study investigated electrotonic remodeling in the post-MI ventricle, as measured by myocardial electrical impedance (MEI), in animals prone to and resistant to VF. MI was induced in dogs by a two-stage left anterior descending (LAD) coronary artery ligation. Before infarction, MEI electrodes were placed in remote (left circumflex, LCX) and infarcted (LAD) myocardium. MEI was measured in awake animals 1, 2, 7, and 21 days post-MI. Subsequently, VF susceptibility was tested by a 2-min LCX occlusion during exercise; 12 animals developed VF (susceptible, S) and 12 did not (resistant, R). The healing infarct had lower MEI than the normal myocardium. This difference was stable by day 2 post-MI (287 +/- 32 Omega vs. 425 +/- 62 Omega, P < 0.05). Significant differences were observed between resistant and susceptible animals 7 days post-MI; susceptible dogs had a wider electrotonic gradient between remote and infarcted myocardium (R: 89 +/- 60 Omega vs. S: 180 +/- 37 Omega). This difference increased over time in susceptible animals (252 +/- 53 Omega at 21 days) due to post-MI impedance changes on the remote myocardium. These data suggest that early electrotonic changes post-MI could be used to assess later arrhythmia susceptibility. In addition, passive-electrical changes could be a mechanism driving active-electrical remodeling post-MI, thereby facilitating the induction of arrhythmias.     

ST段抬高性和非ST 段抬高性急性心肌梗死患者的冠状动脉病变特点比较

目的:比较ST段抬高性和非ST段抬高性急性心肌梗死患者的冠状动脉病变特点。方法:选取100例在我院接受24h动态心电图和冠状动脉造影检查的急性心肌梗死患者,根据心电图结果分为观察组和对照组各50例。对照组为ST段抬高性心肌梗死(STEMI)患者,观察组为非ST段抬高性心肌梗死(NSTEMI)患者,比较两组患者冠状动脉病变的差异。结果:对照组LAD(左前降支)闭塞血管比例(52.00%)显著高于观察组(18.00%),差异具有统计学意义(P0.05)。对照组LCX(回旋支)闭塞血管比例(8.00%)显著低于观察组(50.00%),差异具有统计学意义(P0.05)。对照组RCA(右冠脉主干)闭塞血管比例(40.00%)和观察组(30.00%)比较,差异无统计学意义(P0.05)。对照组单支病变比例(46.00%)明显高于观察组(12.00%),对照组三支病变比例(20.00%)明显低于观察组(48.00%)比较,差异均具有统计学意义(P0.05)。对照组二支及正常血管比例与观察组比较,差异均无统计学意义(P0.05)。对照组罪犯血管狭窄程度在76%-90%、91%-99%及完全闭塞的比例与观察组比较差异均具有统计学意义(P0.05)。罪犯血管狭窄程度在50%及50%-75%时,两组差异无统计学意义(P0.05)。两组并发症发生情况比较,差异无统计学意义(P0.05)。结论:1NSTEMI罪犯血管闭塞以LCX多见,STEMI罪犯血管闭塞以LAD多见;2NSTEMI以三支血管病变较多见,STEMI以单支病变较多见。     

A nonsurgical porcine model of left ventricular dysfunction. Validation of myocardial viability using dobutamine stress echocardiography and positron emission tomography

BACKGROUND: Although several short-term animal models of stunning and hibernation have been studied extensively, it has been difficult to produce a consistent animal model of chronic hibernation. The aim of the present study was to develop a nonsurgical porcine stent model of coronary stenosis in order to investigate the relationship between chronic dysfunctional myocardium and viability using 2D-echo, dobutamine stress echo (DSE) and positron emission tomography (PET). METHODS AND RESULTS: Focal progressive coronary stenosis was induced by implantation of an oversized stent in the left anterior descending (LAD) and/or circumflex (LCX) coronary artery in a total of 115 pigs, according to various experimental protocols: copper stent in the LAD (group I, n = 5); noncoated stainless steel stent in the LAD combined with balloon overstretch (group II, n = 7); poly(organo)phosphazene-coated stent in the LAD (group III, n = 77); and poly(organo)phosphazene-coated stent in both the LAD and the LCX (group IV, n = 26). Occurrence of left ventricular dysfunction was evaluated weekly by 2D-echo. At the time of left ventricular dysfunction the presence of viable myocardium within the dysfunctional region was investigated with DSE and PET, and confirmed by histology. The degree of coronary artery stenosis was measured by quantitative coronary angiography and morphometry. Severe coronary artery stenosis in the presence of dysfunctional, but viable, myocardium was induced in groups III and IV (47% and 11% of the animals, respectively). CONCLUSIONS: The authors developed a nonsurgical porcine stent model of progressive coronary stenosis using an oversized polymer-coated stent resulting in chronically decreased myocardial function, with residual inotropic reserve and viable myocardium. This condition may arise from repetitive periods of ischemia, or from sustained hypoperfusion, or a combination of these processes eventually leading to myocardial hibernation.     

Bilateral coronary fistulae to pulmonic valve in presence of severe three-vessel coronary artery disease

A 62-year-old man was admitted to the coronary care unit due to anginal pain and palpitations--coronary angiography revealed three-vessel coronary artery disease. The unexpected finding was the presence of coronary to pulmonary artery fistulae bilaterally, from both the proximal RCA and the proximal LAD. Right heart catheterization revealed normal right ventricular and pulmonary artery pressure and absence of hemodynamically significant left to right shunt. The patient underwent a triple coronary bypass including the closure of bilateral fistulae, which were draining into the left sinus of the pulmonary valve. One month after the operation he was in good health and had no complaints. Bilateral coronary artery fistulae is a rare anomaly diagnosed in 0.002-0.0013% of adult coronary angiograms. (Int J Cardiovasc Intervent 1999; 2: 249-251).     

Effect of passive myocardium on the compliance of porcine coronary arteries

The objective of this study was to determine the effect of passive myocardium on the coronary arteries under distension and compression. To simulate distension and compression, we placed a diastolic-arrested heart in a Lucite box, where both the intravascular pressure and external (box) pressure were varied independently and expressed as a pressure difference (DeltaP = intravascular pressure - box pressure). The DeltaP-cross-sectional area relationship of the first several generations of porcine coronary arteries and the DeltaP-volume relationship of the coronary arterial tree (vessels >0.5 mm in diameter) were determined using a video densitometric technique in the range of +150 to -150 mmHg. The vasodilated left anterior descending (LAD) coronary artery of six KCl-arrested hearts were perfused with iodine and 3% Cab-O-Sil. The intravascular pressure was varied in a triangular pattern, whereas the absolute cross-sectional area of each vessel and the total arterial volume were calculated using video densitometry under different box pressures (0, 50, 100, and 150 mmHg). In the range of positive DeltaP, we found that the compliance of the proximal LAD artery in situ (4.85 +/- 3.8 x 10-3 mm2/mmHg) is smaller than that of the same artery in vitro (16.5 +/- 6 x 10-3 mm2/mmHg; P = 0.009). Hence, the myocardium restricts the compliance of the epicardial artery under distension. In the negative DeltaP range, the LAD artery does not collapse, whereas the same vessel readily collapses when tested in vitro. Hence, we conclude that myocardial tethering prevents collapse of large blood vessel under compression.