Can myocardial contrast echo determine coronary flow reserve?

OBJECTIVE: The aim was to evaluate the applicability of myocardial contrast echocardiography in the measurement of coronary flow reserve. METHODS: Eleven anaesthetised open chest pigs were studied, in which coronary atherosclerosis had been induced by abrasion of the left anterior descending coronary artery at one month, followed by an atherogenic diet for eight months. Coronary flow reserve was determined by electromagnetic flow measurement and contrast echocardiography before and after partial occlusion of the left anterior descending coronary artery, using papaverine as a coronary vasodilator. Coronary blood flow was reduced by tightening a clamp placed around the coronary artery. Systemic haemodynamics and myocardial wall thickness (epicardial ultrasound 5 MHz transducer) were recorded simultaneously. Echocardiograms were recorded on VHS tape and analysed by digitised videodensitometry off line for construction of the time v videointensity curve (time-intensity curves). From these curves washout time (T50), area under the curve, peak contrast intensity, and time to peak intensity were calculated. RESULTS: Following papaverine, coronary blood flow increased significantly from 47 (SD 23) ml.min-1 at baseline to 88(39) ml.min-1 (p less than 0.05). During the stenosis, flow decreased to 19(16) ml.min-1 (p less than 0.01), and increased to 38(29) ml.min-1 (p less than 0.05 v stenosis) after administration of papaverine. Correlations between coronary blood flow and indices calculated from the quantitative videodensitometric analysis were poor, varying between r = 0.03 for area at control flow to r = 0.62 for T50 during stenosis. The same was true for coronary flow reserve: r = 0.09 for peak to r = 0.75 (p less than 0.05) for time to peak without the stenosis. CONCLUSIONS: Current limitations in injection, imaging, and analysis techniques cause variability in data from time-intensity curves, which precludes accurate quantification of coronary flow (reserve) by myocardial contrast echocardiography.     

Broad old anteroseptal myocardial infarction with coronary aneurysm showing marked improvement of myocardial perfusion by intravenous myocardial contrast echocardiography after successful coronary angioplasty: a case report

A 56-year-old man with old anteroseptal myocardial infarction was admitted to treat a gradually expanding coronary aneurysm. Coronary angiography demonstrated the aneurysm and delayed flow in the left coronary descending artery. The aneurysm was successfully treated with stenting. Technetium-99m-sestamibi single photon emission computed tomography (SPECT) showed a persistent defect in the anterior infarcted area after stenting. Myocardial contrast echocardiography was performed using SystemFIVE and EchoPAC. Levovist was injected (1 ml, 1.5 ml/sec; bolus + 1 ml/sec; continuous infusion) by Pulsar. Myocardial reperfusion was observed by B-mode and anatomical M-mode before and after intervention. Time-intensity curves from the region of interest positioned within the interventricular septum showed the mean value at plateau increased from 10.8 to 25.1 dB. The persistent defect area demonstrated by SPECT was enhanced by myocardial contrast echocardiography after intervention. Myocardial contrast echocardiography is useful for the assessment of outcome after intervention and evaluation of improved coronary blood flow.     

Heat production by the human left ventricle: measurement by a thermodilution technique

STUDY OBJECTIVE - The aim was to study the feasibility of measuring heat production by the human left ventricle with a view to using this variable as an index of left ventricular mechanical efficiency. DESIGN - The transcoronary temperature difference was derived from catheter mounted thermistors placed percutaneously in the aortic root and coronary sinus. Left ventricular blood flow was measured by continuous thermodilution in the coronary sinus, and heat removal by coronary venous blood was calculated from blood flow and the transcoronary temperature difference. Diffusional heat loss was measured using temperature/time curves recorded in aorta and coronary sinus after a bolus injection of cold saline into pulmonary artery. The heat loss from the system into the endothermic reactions of haemoglobin was calculated from left ventricular oxygen extraction using an assumed respiratory quotient. The energy released by left ventricular myocardial metabolism (EEO2, calculated from oxygen extraction), was compared to measured left ventricular heat production, and the mechanical efficiency of the left ventricle was calculated by the formula: Efficiency = (EEO2 - HLV)/EEO2. PATIENTS - Fifteen conscious patients with anginal chest pain were studied at the time of cardiac catherisation and coronary arteriography. MAIN RESULTS - The transcoronary temperature difference was in the range 0.10-0.32 (mean 0.21) degrees C. Total left ventricular heat production, equal to the sum of heat removed by the blood stream, diffusional loss and endothermic reactions (HLV) was in the range 1.5-4.6 (mean 2.7) watts. The values of EEO2 obtained were in the range 2.4-6.5 (mean 4.0) watts, and the calculated mechanical efficiency of the left ventricle was 0.24-0.55 (mean 0.34). CONCLUSIONS - The measurement of heat production by the human left ventricle is safe and practical. This technique promises to be of value in the clinical investigation of the relationship between myocardial function and energy utilisation.     

Effect of nitroglycerin on regional myocardial blood flow following an experimental coronary spasm

This study was designed to evaluate the effect of nitroglycerin (30 micrograms given as an i.v. bolus) on regional distribution of myocardial blood flow in conscious dogs, following an acute coronary occlusion similar to a coronary spasm. The left anterior descending (LAD) coronary artery was acutely occluded with a balloon cuff occluder. The distribution of blood flow between the endocardium and the epicardium of both the normal and ischemic area of the left ventricle was determined by means of the radioactive microsphere technique. Acute occlusion of the left anterior descending coronary artery produced a significant decrease of blood flow reaching the area irrigated by this artery; this decrease was of a lesser magnitude after administration of nitroglycerin. In addition, ischemia produced a disproportionate decrease in endocardial blood flow. This decrement was also of a lesser magnitude following administration of nitroglycerin. Blood perfusion to the non-ischemic myocardium was not altered. These results indicate that an intravenous bolus of nitroglycerin, given after a brief coronary occlusion simulating a coronary spasm, increases blood flow to the ischemic myocardium, induces a favorable redistribution of blood flow toward the ischemic endocardium and does not produce any decrement of blood perfusion to the non-ischemic myocardium.     

Quantitative assessment of myocardial perfusion during graded coronary artery stenoses by intravenous myocardial contrast echocardiography

OBJECTIVES: The purpose of this study was to examine whether coronary stenoses of variable severity could be quantitatively assessed by analysis of myocardial perfusion as determined by intravenous (IV) myocardial contrast echocardiography. BACKGROUND: Recently, new contrast agents and imaging technology have been developed that may enable improved assessment of myocardial perfusion by IV contrast injection. METHODS: Variable obstruction of the left anterior descending (LAD) coronary artery in dogs was produced by a screw occluder. Coronary artery flow was measured with a transit time flowmeter during baseline, pharmacological vasodilation, a non-flow-limiting stenosis at rest in conjunction with vasodilation, a flow-limiting stenosis, and total occlusion. Myocardial contrast echocardiography was performed after IV injection of the contrast agent NC 100100. Time-intensity curves were obtained off-line for the LAD risk area and the adjacent left circumflex (LCx) territory, and peak background-subtracted video intensity was determined. Fluorescent microspheres were injected at each intervention for determination of regional myocardial blood flow. RESULTS: During non-flow-limiting stenosis, flow limiting stenosis and total occlusion, LAD/LCx ratios of peak myocardial videointensity and blood flow decreased proportionately. Both LAD/LCx ratios of video intensity and blood flow identified the non-flow-limiting and the flow-limiting stenoses as well as total occlusion of the LAD artery. A significant correlation between LAD/LCx video intensity and blood flow ratios was observed (r = 0.83, p < 0.0001). CONCLUSIONS: The degree of blood flow mismatch between ischemic and normal myocardial regions during graded coronary stenoses can be estimated in the dog by quantitative assessment of myocardial perfusion produced by IV myocardial contrast echocardiography.     

Value of coronary blood flow pattern as a predictor of functional recovery and short-term left ventricular remodeling after primary coronary angioplasty. A transthoracic Doppler study

INTRODUCTION AND OBJECTIVES: Coronary blood flow measurement using a Doppler guidewire is the most sensitive way of detecting the no-reflow phenomenon following reperfusion of a myocardial infarction (MI). New high-frequency Doppler probes enable coronary blood flow velocity to be measured noninvasively. Our aims were to study the different patterns of left anterior coronary artery blood flow observed by transthoracic Doppler echocardiography, and to describe their association with functional recovery following reperfusion of an anterior MI. METHODS: The study included 57 patients with a mean age of 60 years (range 30-85 years). An abnormal coronary blo:d flow pattern was defined as one in which there was a high peak diastolic velocity and a short deceleration time (i.e., < or = 500 ms). We compared the regional contractility, ventricular volumes, and left ventricular ejection fraction (LVEF) measured after 72 hours with those measured 1 month after MI. RESULTS: Overall, 31 patients (54%) had a normal coronary blood flow pattern (Group 1) and 26 (46%), an abnormal pattern (Group 2). After one month, regional contractility improved in Group-1 patients, as did LVEF, from 46.8 (8.6) to 52.6 (8.8)% (P=.002). In these patients, left ventricular volumes were unchanged. In contrast, regional contractility and LVEF remained unchanged in Group-2 patients whereas ventricular volumes increased, from 55.8 (12.9) to 62.9 (16.8) ml/m2 (P=.05), and from 32.2 (9.5) to 37.1 (14.9) ml/m2 (P< .05). Coronary blood flow pattern was the most important independent predictor of left ventricular remodeling, odds ratio =6.14 (95% CI, 1.56-24.17). CONCLUSIONS: Transthoracic Doppler echocardiographic assessment of coronary blood flow following reperfusion of an anterior myocardial infarction can be used to identify patients with microvascular damage who are progressing towards ventricular dilatation without recovery of myocardial function.     

Evaluation of coronary flow reserve using Doppler guide wire in patients with ampulla cardiomyopathy: three case reports

Coronary flow velocity recordings were obtained in three patients with ampulla (Takotsubo) cardiomyopathy using Doppler guide wire. Immediately after admission, coronary angiography demonstrated no significant stenosis and normal coronary flow in the epicardial coronary artery. Left ventriculography showed abnormal wall motion of the left ventricle mimicking ampulla shape in all patients. The coronary flow velocity pattern was normal, but coronary flow reserve of the left anterior descending coronary artery was decreased by adenosine administration in all patients. The coronary flow reserve in the left circumflex and right coronary artery also decreased. Cardiac catheterization was performed during the follow-up period in two patients. Left ventriculography revealed almost normal wall motion of the left ventricle. The coronary flow reserve normalized in one patient.     

Alpha-adrenergic regulation of the coronary circulation in the conscious dog

To examine the role of neural and humoral factors in the control of coronary vasoactivity in conscious animals in which the complicating effects of general anesthesia and recent surgery were absent, dogs were instrumented with miniature pressure gauges in the aorta and left ventricle to measure aortic and left ventricular pressures and with flow probes in the left circumflex coronary artery to measure coronary blood flow. Several weeks after recovery from operation, experiments were conducted in the conscious dogs. Stimulation of the carotid chemoreceptor reflex elicted a biphasic response; initially striking reflex coronary vasodilation was observed: Coronary blood flow tripled even after changes in metabolic factors were minimized by pretreatment with propranolol. The chemoreceptor reflex coronary vasodilation was mediated both by cholinergic activation and withdrawal of alpha-adrenergic tone. The second phase of the response involved an increase in coronary vascular resistance, associated with elevated arterial pressure and an absolute reduction in coronary blood flow and coronary sinus oxygen content. The later period of coronary vasoconstriction was abolished by alpha-adrenergic blockade. Intravenous infusion of the alpha-adrenergic agonist methoxamine increased mean arterial pressure by 65 ± 5% and total coronary vascular resistance by 92 ± 14%. To determine whether the large coronary arteries were also under autonomic control, the dogs were instrumented with a pair of ultrasonic crystals on opposing surfaces of the left circumflex coronary artery to measure its diameter directly and continuously. Methoxamine reduced coronary cross-sectional area substantially, thereby constricting large coronary arteries and resistance coronary vessels. Thus, while the coronary arteries are regulated by changes in myocardial metabolic demands, they are also responsive to changes in neural stimuli. The most striking changes were observed with augmentation and withdrawal of alpha-adrenergic constrictor tone, which appear to be important in the control of large as well as small coronary vessels.     

Coronary collateral circulation in the pig: correlation of collateral flow with coronary bed size

Summary Coronary bed sizes were measured in pigs. The left anterior descending bed occupies about 31% of the heart, the right coronary bed about 38% of the heart and the left circumflex bed about 31% of the heart is (including atria). The right coronary artery supplies about 81% of the right ventricle and 23% of the left ventricle with its blood supply. The remaining portion of the right ventricle is supplied by the LAD.The collateral circulation was measured in each of the 3 coronary beds using tracer microspheres. Measurements, are in ml/min/100g. Transmural collateral flow in the LC is 5.6, the LAD 1.0, the RC in LV 3.7 and the RC in RV 4.3.Our experiments showed that the coronary bed sizes were relatively uniform in pigs, but that collateral flow was significantly different between the beds.With 4 tablesThis work was supported in part by the Specialized Center on Ischemic Heart Disease, Grant 17682 from NHLBI and USPHS Grant HL 20190.     

Myocardial oxygen supply in left ventricular hypertrophy and coronary heart disease.

Coronary arteriolar dilation adjusts blood flow according to local fluctuating metabolic needs of the myocardium. Because of high extravascular compression during systole, the subendocardial layer of the left ventricle is especially dependent on the duration and the perfusion pressure of the diastolic period. In patients with obstructive coronary artery disease, regional arteriolar dilation is utilized to compensate for focal arterial stenoses. Coronary blood flow may be compensated with the patient at rest, but loss of reserve arteriolar dilation limits further adjustment to superimposed transient increases in metabolic needs. Subendocardial perfusion in the region supplied by the stenosed artery is especially vulnerable to shortened diastolic time during tachycardia. In patients with chronic aortic valve disease, the metabolic rate of the left ventricle is increased in proportion to the increases in myocardial mass and work. Coronary blood flow and metabolic rate per gram of the hypertrophied myocardium are normal when the patient is at rest, at the expense of diminished coronary arteriolar reserve. High tissue pressure relative to the diastolic perfusion pressure probably contributes to the diffuse subendocardial ischemia that occurs in these patients during tachycardia.     

The effect of coronary artery lesions on the relationship between coronary perfusion pressure and myocardial blood flow during cardiopulmonary resuscitation in pigs

In subjects without coronary disease, coronary perfusion pressure generated with closed-chest cardiopulmonary resuscitation (CPR) bears a direct relationship to myocardial blood flow. The effect of coronary lesions on this relationship was studied in an experimental porcine model not requiring thoracotomy. Coronary stenoses (a 50% reduction in coronary cross-sectional area) or total coronary occlusions were created by percutaneous, transarterial catheter placement of a Teflon cylinder in the left anterior descending artery of 21 swine (30 to 60 kg). Coronary perfusion pressure, defined as the aortic diastolic pressure minus right atrial diastolic pressure, was correlated with myocardial blood flow measured with nonradioactive, colored microspheres during external chest compression CPR. Complete occlusion of the left anterior coronary artery resulted in essentially no CPR-generated blood flow to the anterior myocardium distal to the site of occlusion. Coronary perfusion pressure showed a positive correlation with myocardial blood flow above the area of occlusion (r = 0.783; p less than 0.01) but did not correlate with myocardial blood flow below the occlusion site (r = 0.239). In the presence of a patent coronary artery stenosis, coronary perfusion pressure correlated with myocardial blood flow both above (r = 0.841; p less than 0.001) and below (r = 0.508; p less than 0.05) the stenosis. During closed-chest CPR producing coronary perfusion pressures between 30 and 60 mm Hg, anterior myocardial blood flow was 109 +/- 16 ml/min/100 gm above a patent stenosis and 66 +/- 13 ml/min/100 gm below the stenosis (p less than 0.005). Over a wide range of coronary perfusion pressures, myocardial blood flow below a coronary lesion was significantly less than that above the lesion. Coronary occlusions and stenoses can substantially affect the amount of CPR-generated coronary perfusion pressure needed to produce distal myocardial blood flow.     

New noninvasive diagnosis of myocardial ischemia of the left circumflex coronary artery using coronary flow reserve measurement by transthoracic Doppler echocardiography: comparison with thallium-201 single photon emission computed tomography

OBJECTIVES: The usefulness of coronary flow reserve measurement in the left circumflex coronary artery by transthoracic Doppler echocardiography to detect myocardial ischemia was compared with exercise thallium-201 single photon emission computed tomography (SPECT). METHODS: Transthoracic Doppler echocardiography was performed in 110 patients with suspected coronary artery disease. Color Doppler signals of the left circumflex coronary artery flow in the apical four-chamber view were identified, and the velocities at rest and during hyperemia recorded for calculation of coronary flow reserve by the pulsed Doppler method. All patients underwent SPECT within 1 week of the transthoracic Doppler echocardiographic study. RESULTS: Coronary flow reserve in the left circumflex coronary artery was measured in 79 (72%) of 110 patients. SPECT revealed reversible perfusion defect in the left circumflex coronary artery territories in 12 of 69 patients excluding those with multivessel disease. Coronary flow reserve < 2.0 had a sensitivity of 92% and specificity of 96% for reversible perfusion defect detected by SPECT. CONCLUSIONS: Noninvasive coronary flow reserve measurement in the left circumflex coronary artery by transthoracic Doppler echocardiography can estimate myocardial ischemia in the left ventricular lateral regions.     

Assessment of regional myocardial blood flow with myocardial contrast two-dimensional echocardiography

It was hypothesized that regional myocardial blood flow could be measured using myocardial contrast echocardiography. Accordingly, arterial blood was perfused into the coronary circulation in 16 dogs. In Group 1 dogs (n = 8), blood flow to the cannulated left circumflex artery was controlled with use of a roller pump, whereas in Group 2 dogs (n = 8) blood flow to the left anterior descending coronary artery was controlled by a hydraulic occluder placed around it. Sonicated microbubbles (mean size 4 microns) were used as the contrast agent. In Group 1 dogs the microbubbles were injected subselectively into the left circumflex artery, whereas in Group 2 dogs they were injected selectively into the left main coronary artery and two-dimensional echocardiographic images were recorded. Computer-generated time-intensity curves were derived from these images and variables of these curves correlated with transmural blood flow measured with radiolabeled microspheres. A gamma-variate function (y = Ate-alpha t) best described the curves, and alpha (a variable of curve width) correlated well with transmural blood flow at different flow rates in all Group 1 and Group 2 dogs (mean r = 0.81 and 0.97, respectively). Other variables of the curve width also correlated well with myocardial blood flow, but peak intensity had a poor correlation with myocardial blood flow in both groups of dogs (r = 0.39 and r = 0.63, respectively). When data from all dogs were pooled, Group 1 dogs still showed good correlation between variables of curve width and myocardial blood flow (r = 0.81); Group 2 dogs did not (r = 0.45). The difference between the two sets of dogs was related to the site of contrast agent injection. It is concluded that measurement of the transit time of microbubbles through the myocardium with two-dimensional echocardiography accurately reflects regional myocardial blood flow. Although injection of contrast agent selectively into the left main coronary artery only allows measurement of relative flow, it may be feasible to measure absolute flow by injecting contrast agent subselectively into a coronary artery. Myocardial contrast echocardiography may, therefore, offer the unique opportunity of simultaneously assessing regional myocardial perfusion and function in vivo.     

Severe diffuse coronary artery spasm in the early phase of cardiogenic shock

Coronary artery vasospasm rarely appears as a diffuse phenomenon that involves all the coronary tree. We present a clinical case of acute myocardial infarction complicated by ventricular fibrillation and cardiogenic shock. Urgent coronary angiography showed occlusion of proximal Circumflex coronary artery and a TIMI I flow in the left anterior descending artery due to severe, diffuse coronary vasospasm. Patient was successfully treated with intra-aortic balloon pump and intracoronary bolus of nitroglycerin with restoration of flow in left coronary branches and complete resolution of shock.     

The role of transesophageal dopplerographical assessment of coronary reserve in coronary sinus in diagnosis of hemodynamically significant left coronary artery stenoses

AIM: To assess the role of estimation of coronary reserve in coronary sinus by transesophageal doppler during dipyridamole stress test for diagnosis of hemodynamically significant left coronary artery stenoses. MATERIAL: Patients with angiographically proven left coronary artery stenoses (n=29) and 25 healthy volunteers. METHODS: Coronary reserve was calculated as 1) ratio of peak to basal diastolic coronary flow velocity (V(p)CR), and 2) ratio of volume coronary blood flow velocity before and during hyperemia (VBF CR). Coronary reserve <2 was considered decreased. RESULTS: Compared with healthy subjects patients with coronary heart desease had significantly lower V(p)CR (1.67+/-0.44 and 2.56+/-0.87, respectively, p<0.001) and VBF CR (2.42+/-1.37 and 5.53+/-3.65, respectively, p<0.001). Sensitivity and specificity of coronary reserve below 2 for diagnosis of left coronary artery stenoses was 72 and 72%, respectively, for V(p)CR, and 49 and 96%, respectively, for VBF CR. VBF CR below 2 was a marker of severe double vessel left coronary artery disease. V(p)CR <2 was associated with single vessel stenoses within left coronary artery system. CONCLUSION: The use of evaluation of coronary reserve by transesophageal dopplerography for diagnosis of left coronary artery stenoses is methodologically correct. Level of coronary reserve in coronary sinus can be considered an integral parameter characterizing total left coronary artery atherosclerotic damage.     

Effects of atrial natriuretic peptide on the coronary arterial vasculature in humans

The effects of the synthetic 28-amino-acid alpha-human atrial natriuretic peptide (ANP) on the proximal coronary arteries and coronary blood flow were evaluated in 17 patients. Proximal coronary dimension was quantitated by digital angiography, and coronary flow was quantitated with 3F Doppler flow catheters. ANP, when given as a 2.5-micrograms/kg bolus in the left ventricle, caused sustained significant proximal coronary dilations from 3.49 +/- 0.57 to 4.09 +/- 0.76 mm, lasting more than 30 minutes. The proximal coronary diameter did not increase further after intracoronary injection of 0.3 mg nitroglycerin (4.08 +/- 0.79 mm). Coronary flow (resistance coronary dilation) was not significantly increased at 5 minutes after ANP (87 +/- 55 to 102 +/- 54 vol flow units), indicating that the proximal coronary dilations were not flow dependent. The persistent proximal coronary dilations were associated with minor and transient decreases in aortic pressure and left ventricular end-diastolic pressure and with minor and transient increases in heart rate, cardiac output, and left ventricular contractility. Plasma ANP level increased significantly by more than sixfold from 39.8 +/- 8.8 to 245.8 +/- 168.5 pg/ml. The time course of proximal coronary dilations was related more closely to the time course of increase in plasma cyclic guanosine monophosphate than that of plasma ANP. This study demonstrates that bolus injection of ANP (2.5 micrograms/kg), an endogenous vasodilator, caused marked sustained preferential proximal coronary dilations and brief minor changes in cardiac and systemic hemodynamics. Although additional studies are needed to assess its clinical efficacy as a coronary dilator in the treatment of coronary artery disease, these data suggest a potential of ANP in the therapy of ischemia.     

Measuring blood flow velocity in the coronary sinus with Doppler catheters]

Measurements of the coronary sinus blood flow velocity with Doppler catheters (Medtronic Floscan; Millar DC201) were performed to assess coronary flow reserve and significance of coronary artery stenosis. In seven patients with normal coronary angiogram coronary sinus blood flow velocity (Doppler catheters) and coronary sinus blood flow volume (thermodilution) were simultaneously recorded. Coronary flow reserve was calculated as the quotient of the peak flow velocity (peak flow volume) and resting flow velocity (resting flow volume) after infusion of 0.5 mg/kg dipyridamole intravenously. The correlation coefficient was r = 0.88. Coronary sinus blood flow velocity was measured in 31 patients at resting conditions and after injection of contrast media during coronary angiography. At resting conditions blood flow velocity was 3.6 +/- 1.5 cm/s (n = 31), 3.5 +/- 1.8 cm/s (n = 9; controls), and 3.6 +/- 1.1 cm/s (n = 9; significant stenosis of the left anterior descending; not significant). After injection of contrast media flow velocity amounted to 2.2-fold resting flow in controls and to 1.5-fold resting flow in patients with stenoses of the left anterior descending artery (p less than 0.01). Measurement of coronary sinus blood flow velocity with Doppler catheters is a valuable adjunct for determination of coronary flow reserve and for assessment of stenosis severity of the left anterior descending artery. Continuous on-line monitoring of phasic flow velocity provides important information of the myocardial perfusion, e.g., during angioplasty.     

Complete proximal occlusion of all three main coronary arteries complicated with a left main coronary aneurysm: a case report

A 68-year-old woman with recurrent chest pain was referred to our institution. Coronary angiography showed 100% obstruction of the left main trunk, the proximal right coronary artery with good collaterals to the left anterior descending artery and left circumflex artery along the conus artery. Emergency surgical revascularization was undertaken with two saphenous vein grafts. The saphenous vein grafts were placed in the left anterior descending artery, obtuse marginal branch and the posterolateral and posterior descending coronary arteries with excellent flow. The postoperative course was uneventful and follow-up angiography was obtained 20 days after the surgery. Coronary angiography demonstrated a saccular aneurysm (10 x 9 mm) originating at the distal segment of the left main coronary artery with 90% stenosis, and excellent patency of both saphenous vein grafts. Follow-up angiography was performed 1 and 3 years after the surgery. The size of the left main coronary aneurysm remained unchanged at both examinations. The patient did well with no further cardiac symptoms after 5 years.     

Coronary flow reserve in angiographically normal coronary arteries with one-vessel coronary artery disease without traditional risk factors.

AIMS: Reduced coronary flow reserve has been reported in patients with traditional risk factors, in particular hyperlipidaemia, despite angiographically normal coronary arteries. However, it is recognized that traditional risk factors do not explain the presence of coronary atherosclerosis in a large proportion of patients. The aim of this study was to assess whether coronary flow reserve is preserved in the myocardium supplied by normal coronary arteries in patients with one-vessel coronary artery disease without traditional risk factors. METHODS AND RESULTS: Positron emission tomography using [13N]ammonia was performed at baseline and after intravenous dipyridamole administration (0.56 mg x dl(-1)over 4 min) in 30 subjects: six patients with ischaemia on effort, no myocardial infarction, and isolated left anterior descending coronary artery stenosis without traditional risk factors (coronary artery disease patients without risk factors, aged 59+/-13), five patients with ischaemia on effort, no myocardial infarction, and isolated left anterior descending coronary artery stenosis with multiple risk factors (coronary artery disease patients with risk factors, aged 69+/-7), 11 age-matched controls (aged 58+/-6), and eight healthy young volunteers (aged 34+/-4). Myocardial blood flow calculated in the myocardium supplied by normal coronary arteries in the coronary artery disease patients was compared with those of the two control groups. Coronary flow reserve was defined as the ratio of hyperaemic blood flow after dipyridamole infusion to baseline blood flow. Although coronary flow reserve in the coronary artery disease patients with risk factors was significantly lower than that in the age-matched controls (1.62+/-0.37, 2.58+/-0.71, P=0.0428), coronary flow reserve in the coronary artery disease patients without risk factors was similar to that in the age-matched controls (2.54+/-0.17 vs 2.58+/-0.71, P=ns). CONCLUSION: Coronary flow reserve is preserved in regions supplied by angiographically normal coronary arteries with one-vessel coronary artery disease without traditional risk factors.     

Streptokinase improves reperfusion blood flow after coronary artery occlusion

Streptokinase is an effective thrombolytic agent which, with early restoration of coronary blood flow, has the potential for limiting infarct size. Distinct from thrombolysis, we studied the effects of streptokinase on reperfusion coronary blood flow and infarct size. Open-chest anesthetized canines underwent a 90 minute snare occlusion of the left circumflex coronary artery followed by release and reperfusion through a critical stenosis for 6 hours. The animals were assigned randomly to two groups. Intracoronary streptokinase [group 1 (n = 8): 6000 IU/kg in 3 ml of saline] or saline [group 2 (n = 8): 3 ml of saline] was infused at 0.05 ml/min for 60 minutes beginning 30 minutes before reperfusion. Coronary blood flow was stable in group 1 during reperfusion, while in group 2 it fell during 6 hours of reperfusion (30 +/- 4 ml/min to 18 +/- 2 ml/min, P = 0.05). The ST-segment elevation on the limb lead II electrocardiogram 15 minutes after coronary artery occlusion was similar in both groups (group 1: 3.9 +/- 0.6 mV, group 2: 2.3 +/- 0.5 mV), suggesting the extent of myocardial ischemia was also similar in both groups. The infarct sizes were similar when expressed both as a percent of the total left ventricular mass [(IZ/LV) group 1: 17 +/- 2.5%, group 2: 17.5 +/- 2.5%] or as a percent of the area at risk of infarction [(IZ/AR) group 1: 39 +/- 6%, group 2: 39 +/- 5%]. In both groups, the mass of left ventricle dependent on the blood flow distribution of the left circumflex coronary artery was similar when compared to total left ventricular mass [(AR/LV) group 1: 41 +/- 3%, group 2: 44 +/- 4%]. These results demonstrate that streptokinase maintains reperfusion coronary blood flow through a critical stenosis at a rate similar to baseline levels. Despite the fact that coronary blood flow remained stable with streptokinase during reperfusion, infarct size was not limited after 90 minutes of fixed coronary artery occlusion in this canine model of myocardial injury.