Anterior Descending Coronary Artery Research Articles

Adenosine concentration in the porcine coronary artery wall and A2A receptor involvement in hypoxia‐induced vasodilatation

We tested whether hypoxia-induced coronary artery dilatation could be mediated by an increase in adenosine concentration within the coronary artery wall or by an increase in adenosine sensitivity. Porcine left anterior descendent coronary arteries, precontracted with prostaglandin F(2alpha) (10(-5) M), were mounted in a pressure myograph and microdialysis catheters were inserted into the tunica media. Dialysate adenosine concentrations were analysed by HPLC. Glucose, lactate and pyruvate were measured by an automated spectrophotometric kinetic enzymatic analyser. The exchange fraction of [(14)C]adenosine over the microdialysis membrane increased from 0.32 +/- 0.02 to 0.46 +/- 0.02 (n = 4, P < 0.01) during the study period. At baseline, interstitial adenosine was in the region of 10 nM which is significantly less than previously found myocardial concentrations. Hypoxia (P(O(2)) 30 mmHg for 60 min, n = 5) increased coronary diameters by 20.0 +/- 2.6% (versus continuous oxygenation -3.1 +/- 2.4%, n = 6, P < 0.001) but interstitial adenosine concentration fell. Blockade of adenosine deaminase (with erythro-9-(2-hydroxy-3-nonyl-)-adenine, 5 microM), adenosine kinase (with iodotubericidine, 10 microM) and adenosine transport (with n-nitrobenzylthioinosine, 1 microM) increased interstitial adenosine but the increase was unrelated to hypoxia or diameter. A coronary dilatation similar to that during hypoxia could be obtained with 30 microM of adenosine in the organ bath and the resulting interstitial adenosine concentrations (n = 5) were 20 times higher than the adenosine concentration measured during hypoxia. Adenosine concentration-response experiments showed vasodilatation to be more pronounced during hypoxia (n = 9) than during normoxia (n = 9, P < 0.001) and the A(2A) receptor antagonist ZM241385 (20 nM, n = 5), attenuated hypoxia-induced vasodilatation while the selective A(2B) receptor antagonist MRS1754 (20 nM, n = 4), had no effect. The lactate/pyruvate ratio was significantly increased in hypoxic arteries but did not correlate with adenosine concentration. We conclude that hypoxia-induced coronary artery dilatation is not mediated by increased adenosine produced within the artery wall but might be facilitated by increased adenosine sensitivity at the A(2A) receptor level.

Coronary Artery Atherosclerosis Is Related to Reduced Regional Left Ventricular Function in Individuals Without History of Clinical Cardiovascular Disease

We investigated whether regional coronary calcium score by computed tomography is related to regional left ventricular systolic function measured by MRI tagging in participants of the Multiethnic Study of Atherosclerosis. The Multiethnic Study of Atherosclerosis is a prospective observational study of men and women without a history of previous heart disease from 4 ethnic groups. Calcium scores were measured separately for the left anterior descendent (LAD), left circumflex (LCX), and right (RCA) coronary arteries. Left ventricular strain and strain rate were determined by tagged MRI in the corresponding vascular territories of the coronary vessels in 509 participants. Greater coronary calcification in the LAD, LCX, and right RCA coronary arteries were related to worse function in their respective perfusion. Anterior wall strain rate was -1.37+/-0.41 when LAD calcium was zero versus -1.17+/-0.24 1/s in the highest quartile of calcium score (P<0.001). Similar relationships were evident in the LCX and RCA regions. Participants with 1- and 2-vessel coronary artery calcium had better myocardial function in the remote area compared with the territory supplied by the diseased artery. High-local calcium score is related to regional dysfunction in the corresponding coronary territory among individuals without a history of previous heart disease. These results indicate a link between atherosclerosis and subclinical regional left ventricular dysfunction.

Idiopathic giant aneurysm of left atrial appendage

appendage, extending up to the apex of the left ventricle(Fig. 2). The aneurysm was compressing the obtuseborder of the heart, which made the lateral wall of theleft ventricle concave; the left anterior descendingcoronary artery followed a course along an abnormalacute anterior margin; the wall of the aneurysm wasthin and noncontractile, in the caudal part of theaneurysm, there was a tiny appendage, which wasfibrillating. The aneurysm itself was opened, there wasno thrombus inside it and was communicated with theleft atrial body through a wide neck, about 4.5 cm indiameter. The neck of the sac was in front of the leftpulmonary veins, which were in their normal location.The aneurysm was resected and the opening wassutured in two raws partially supplemented withmechanical staples. Deairing was done through the leftventricular apex and aortic root; the heart spontaneouslydefibrillated to sinus rhythm; weaning the patient frombypass was easy. The postoperative course wasueventual and the patient was discharged in 10

1151-143 Regional wall motion abnormalities during dobutamine stress echocardiography in patients with systemic sclerosis

Background : Systemic sclerosis (SSc) is a chronic connective tissue disorder of unknown etiology, characterized by cutaneous and visceral involvement.The pathogenesis of the cardiac lesion in SSc is controversial, but the primary disorder of microvasculature with diffuse arteriolar and capillary lesions could precede any fibrosis, thus causing ischemic disorder to the heart. Dobutamine stress echocardiography (DSE) is a sensitive predictor of coronary artery disease. This study was performed to assess the value of DSE for noninvasive diagnosis of cardiac involvement in patients with SSc without clinical evidence of heart disease and to determine if abnormal responses to dobutamine can be explained by a decreased coronary flow velocity reserve (CFVR). Methods : We studied 27 patients with SSc without clinical evidence of heart disease, (15 with diffuse form and 12 with localized form of SSc), age 54±12. All patients underwent high dose DSE testing (5-40 mcg/kg/min) and evaluation of CFVR in the left anterior descending coronary artery with contrast transthoracic Doppler during adenosine infusion (140 µg/Kg/min in 5 minutes). Patients were divided into two groups based on the absence (group A; n=15) or presence ( group B; n=13) of regional wall motion abnormalities (RWMA) on DSE. Results : In 13 out of 28 pts (46%) with SSc, we found RWMA during DSE with patchy distribution. Both groups showed normal CFVR values (group A, 2.76±0.7; group B, 2.26±0.4), but CFVR in group B was statistically reduced compared to group A (p=0.03). Conclusion : This study showed that many patients with SSc, without clinical evidence of heart disease, have inducibile RWMA during DSE with patchy distribution. Furthemore, CFVR reduction suggests the role of a partial coronary microvascular dysfunction in these group of patients.

Beat-to-beat repolarization variability measured by T wave spectral variance index in chronic infarcted animals.

Recent experimental and clinical studies have shown that beat-to-beat variability of repolarization morphology is associated with an increased risk for developing malignant ventricular arrhythmias. However, few data exist on the relationship between beat-to-beat repolarization variability and myocardial infarction itself. In the present work we tested the algorithm of T wave spectral variance (TWSV) using the two dimension fast Fourier transform, in an animal model of myocardial infarction to extend the evidences that support the existence of beat-to-beat alteration in repolarization during the chronic stage of myocardial infarction. Thirty-four New Zealand rabbits were included in the study and divided in two groups. Group I (N = 24) exposed to surgical ligation of the left anterior descendent coronary artery. Group II (N = 10) sham operated animals. The TWSV index was calculated before and after 15 and 45 days of surgery. Both groups showed significant increments in TWSV after 15 days postsurgery. However, while the sham animals return to its control value, the infarcted group exhibited values of the TWSV index that remains significantly high after 45 days of surgery, with a mean increment of 28.7% (P < 0.05 against sham). Moreover, when the infarcted group was qualitatively divided in three subgroups, according to its infarction areas, a trend was found in the correlation between the magnitude of the infarcted area and the TWSV index. This noninvasive measure confirms the presence of temporal repolarization variability associated with chronic myocardial infarction and further contributes to identify the infarcted animals.

Comunicación interventricular apical postinfarto inferior y origen anómalo de coronaria izquierda

Rev Esp Cardiol 2002;55(1):67 67 The patient was a 63-year-old woman with a history of high blood pressure, obesity, and stable effort angina. She was admitted for uncomplicated acute inferior myocardial infarction. On day 3, clinical signs of progressive heart failure appeared, with a harsh pansystolic murmur in the mitral focus irradiated to the right sternal edge. She developed cardiogenic shock and required inotropic medication and intra-aortic balloon counterpulsation. Transesophageal echocardiography disclosed left ventricular (LV) inferior akinesia, right ventricular (RV) dilation with severely impaired systolic function, and a large ventricular septal defect (VSD) in the apical septum. Left ventriculography (left oblique anterior view) confirmed the existence of an apical VSD and its dimensions (Figure 1). Coronariography and aortography ( Figures 2 and 3) detected the anomalous origin of the left coronary artery trunk (LCT) on the proximal segment of the right coronary artery (RC). The anterior descending (AD) and circumflex (CX) coronary arteries were poorly developed. The AD, posterior interventricular (PIV), and posterolateral coronary arteries were stenotic. The patient underwent emergency surgery to close the VSD with a Teflon patch and coronary bypass with the internal mammary artery to the first diagonal. The postoperative evolution was satisfactory and at 5 months she was asymptomatic. The association of an apical VSD and inferior infarction is uncommon. In this patient, this association was due to the poor development of the anomalous left coronary artery, with a small anterior descending coronary artery and septal branches. As a result, the septal vessels dependent on the PIV irrigated the septum.

Síndrome antifosfolípido con infarto de miocardio y afectación valvular aórtica

The primary antiphospholipid syndrome is a disorder which is characterized by: arterial and/or venous thrombosis, thrombocytopenia, recurrent fetal loss and high plasma levels of antiphospholipid antibodies. Valvular involvement is associated with arterial thrombosis and the most frequent manifestation is regurgitation. We report the case of a young male with primary antiphospholipid syndrome and previous cerebrovascular thrombosis hospitalized for subacute myocardial infarction. Coronary angiography revealed right and left anterior descendent coronary artery stenosis, the latter being successfully recanalized by direct percutaneous transluminal coronary angioplasty. Transthoracic echocardiography demonstrated aortic valve involvement with predominant regurgitation and transesophageal echocardiography detected valve excrescences on the aortic leaflets. Laboratory study demonstrated thrombocytopenia, prolonged activated partial thromboplastin time and high titers of anticardiolipin antibodies. Oral anticoagulation therapy was started. Thrombotic events have not recurred after three months of follow-up.

The influence of transmural pressure and longitudinal stretch on K+- and Ca2+-induced coronary artery constriction.

The aim of the study was to investigate transmural pressure and longitudinal stretch modulation of K+- and Ca2+-induced constriction of porcine conductance coronary arteries. In a pressure myograph set-up, left anterior descendent coronary arteries from 70 to 90 kg pigs were investigated at pressures from 20 to 120 mmHg. Longitudinal extension ratio (lambda = L/L0(-1), where L0 is the in situ length and L the examination length) varied between 0.9 and 1.1. Two protocols were carried out: (1) Outer diameter response to maximal depolarization by K+ 125 mM at 20-120 mmHg and lambda at 0.90-1.10. (2) Concentration-response curves with K+ (4.7-125 mM) and Ca2+ (0.05-4.0 mM) at four combinations of P and lambda (P = 100 mmHg, lambda = 0.9; P = 100 mmHg, lambda = 1.1; P = 40 mmHg, lambda = 0.9; p = 40 mmHg, lambda = 1.1). Endothelial function was preserved. A slight (<5% diameter reduction) basal tone and no myogenic response was found. Protocol 1: the constriction to K+ 125 mM was maximal in a wide pressure range from 40 to 120 mmHg. Despite the fact that K+-induced diameter changes were statistically insignificant between 40 and 120 mmHg, there was a linear trend towards smaller diameter changes in this pressure range (r = -0.54, P < 0.01). Stretch influenced constriction at 20 mmHg because lambda = 0.90 and 0.95 resulted in smaller diameter-reductions than lambda = 1.00-1.10 (P < 0.05 for all). Contrastingly, at 120 mmHg the constriction at lambda = 1.10 was smaller than the responses at lambda = 0.90-1.05 (P < 0.05 for all). Protocol 2: EC50 and EC10 values for K+- and Ca2+ were generally higher (more sensitive) at 40 compared with 100 mmHg. Stretch was of no significant importance for EC50 and EC10 at 40 and 100 mmHg. It is concluded that porcine coronary artery constriction to non-metabolized agonists is maximal at 40 mmHg with a trend towards smaller diameter changes with higher pressures. Longitudinal stretch affects responsiveness at pressure extremes.

Differential Effects on Left Atrial Function of Pacing-induced Ischemia in Patients With Diseased Proximal Left Anterior Descending and Proximal Left Circumflex Coronary Artery

Differential Effects on Left Atrial Function of Pacing-induced Ischemia in Patients With Diseased Proximal Left Anterior Descending and Proximal Left Circumflex Coronary Artery

Porcine coronary artery pharmacodynamics in vitro evaluated by a new intravascular technique: Relation to axial stretch

A new intravascular balloon catheter-based technique, impedance planimetry and the wire-mounted isometric tension technique commonly employed to study vessel pharmacodynamics in vitro, were compared. Porcine left anterior descendent coronary artery reactivity to nifedipine was assessed and the influence of 20% axial stretch was investigated. There were no histological differences between segments where the impedance planimetry balloon had been inflated and untouched segments. EC 50 values differed significantly between the three procedures applied: The isometric method ( n = 7): 2.54 ± 0.44 · 10 −9 M; nonstretched arteries by the impedance planimetric method ( n = 7): 1.99 ± 0.40 · 10 −8 M; arteries 20% axially stretched ( n = 7): 2.00 ± 1.36 · 10 −7 M (isometric and nonstretched: p < 0.05; isometric and stretched: p < 0.001; nonstretched and stretched: p < 0.05). Maximal relaxant responses to nifedipine were 91.8 ± 2.1% (isometric method), 105.1 ± 2.3% (nonstretched), and 104.9 ± 7.7% (stretched) (ANOVA, p = 0.11). In stretched arteries, the initial 12-min response to an increased dose of nifedipine was more rapid than the response of nonstretched arteries at a concentration of 1 · 10 −7 M ( p = 0.038) and had a nonsignificant tendeney toward a more rapid response at other concentrations. Resting tone could not be demonstrated and time control experiments showed no change in the maximal vessel response to potassium with any of the three methods. A new method in the evaluation of artery pharmacodynamics in vitro was presented. The study demonstrated that axial stretching of an artery has impact on the pharmacodynamic reactivity to nifedipine in porcine coronary arteries. Further studies are needed to evaluated the impact of the method on endothelial function.

Mechanics of porcine coronary arteries ex vivo employing impedance planimetry: a new intravascular technique.

Our objective was to evaluate methodological aspects of impedance planimetry, a new balloon catheter-based technique, for the investigation of coronary artery mechanical wall properties. We used a four ring-electrode electrical impedance measuring system that was located inside a balloon. Two of the electrodes were used for excitation and connected to a generator producing a constant alternating current of 250 mA at 5 kHz. The other two electrodes for detection were placed midway between the excitation electrodes. The balloon was distended with electrically conducting fluid through an infusion channel. The vessel cross-sectional area (CSA) was measured according to the field gradient principle by measuring the impedance of the fluid inside the balloon. Impedance planimetry was applied in the three major branches of the coronary arteries of seven extracted porcine hearts to assess luminal CSAs in response to internal pressurization. The biomechanical wall properties were evaluated by computing the strain [(r - r0) x r0(-1), where r is the vessels inner radius computed as (CSA x pi-1)1/2 and r0 is the radius of the vessel at a minimal distension pressure], the tension [(r x dP), where dP is the transmural pressure difference], and the pressure elastic modulus (delta P x r x delta r-1). We found that in vitro testing demonstrated that impedance planimetry was accurate and reproducible. The technique has controllable sources of error. Measurements were performed with consecutively increasing pressures in the range 1-25 kPa (8-188 mmHg, 0.01-0.25 atm). The CSAs increased nonlinearly and were significantly larger in the left anterior descendent coronary artery (LAD) (1 kPa, mean 5.0 mm2; 25 kPa, mean 21.8 mm2) than in both the left circumflex (Cx) (4.5-16.0 mm2) and the right coronary artery (RCA) (2.8-15.6 mm2) (analysis of variance, P < 0.001 for both). The circumferential wall tension-strain relation showed exponential behavior. For a given strain, tension values for LAD were significantly lower than those of Cx (P < 0.01). The pressure elastic modulus-strain relation also was exponential, and values for Cx were significantly lower than values for LAD (P < 0.001) and RCA (P < 0.05). Impedance planimetry was applied to the study of coronary artery biomechanics ex vivo. The LAD had the largest CSA, and the Cx was the least compliant. Methodological aspects of an in vivo introduction of the method require additional evaluation.

Myocardial ultrasonic backscatter for characterization of ischemia and reperfusion: relationship to wall motion

We have previously shown that cardiac cycle-dependent variation of integrated backscatter occurs in normal myocardium. To determine whether myocardial ischemia and reperfusion can be distinguished by real-time integrated backscatter imaging we performed 10 min balloon occlusion of the Left Anterior Descending (LAD) coronary artery followed by reperfusion in 10 closed-chest anesthetized dogs. Images were obtained at baseline, during occlusion, and up to 120 min after reperfusion. We measured the magnitude and delay of cyclic variation of integrated backscatter in segments with and without asynergy. Radiolabeled microspheres were used to verify both ischemia and reperfusion. Ischemic segments exhibited decreased magnitude and increased normalized delay of cyclic variation of integrated backscatter (from 3.3± 0.3 dB to 1.4 ± 0.2 dB, mean ± SE; and from 0.95 ± 0.03 to 1.67 ± 0.15, respectively, all p ≤ 0.001). Reperfusion promptly restored the magnitude of cyclic variation toward normal. However, the delay of the cyclic variation was restored only partially. Wall motion analysis of the ischemic sites revealed persistent abnormalities throughout the reperfusion interval despite return to normal of the magnitude and delay of cyclic variation. Thus, real-time integrated backscatter imaging permits detection and differentiation of changes in myocardial acoustic properties indicative of ischemia and of subsequent reperfusion.

Free Internal Mammary Artery as Canine Coronary Artery Bypass Graft

From 8 dogs both internal mam mary arteries (IMA) were harvested: the right IMA as a naked artery with out surrounding tissue and the left IMA with 2-cm-wide surrounding tis sue. Both free IMA grafts were anas tomosed to the proximal end of the left IMA one after another and then to the left anterior descending coro nary artery. At six months the free IMA grafts were harvested and stud ied by light microscopy and scanning electron microscopy (SEM). Six dogs lived the period of six months and all free IMA grafts were patent at that time. In the histologic study 3 grafts were graded as normal and intimal thickening was seen in 8 cases. The endothelial cells were covering the lu minal surface of every free IMA graft in SEM, although some degeneration was seen. This study showed that free IMA grafts maintain their patency well and the method of the dissection of the IMAs did not have any effect on the results.

IMPORTANCE OF "RECIPROCAL" ELECTROCARDIOGRAPHIC CHANGES DURING OCCLUSION OF LEFT ANTERIOR DESCENDING CORONARY ARTERY: Studies during Percutaneous Transluminal Coronary Angioplasty

ST-segment depression remote from the region of acute myocardial infarction was investigated in three groups of patients undergoing left anterior descending coronary angioplasty. Ten patients had single-vessel disease, nine concomitant stenoses in one or more other major coronary arteries, and two myocardial infarction after occlusion during angioplasty. Continuous surface electrocardiograms were recorded from leads I, II, III, v2, and v5, before, during, and after coronary angioplasty and ST-segment changes were measured to 0·1 mm. All ten patients with single-vessel disease had ST-segment elevation in lead V2 and nine also had changes in lead III. All nine patients with multivessel disease had ST-segment changes in lead v2; eight of them had concomitant changes in lead III. Both patients with myocardial infarction had elevation in lead v2 and depression in lead III. ST-segment changes began simultaneously in all leads where they occurred. Most (70%) patients with single-vessel disease who had inferior ST-segment depression had a right-dominant coronary circulation. Therefore, the presence of inferior ST-segment depression during left anterior descending coronary artery occlusion does not indicate the presence or absence of multivessel disease. Furthermore, it is unlikely that this change always represents ischaemia remote from the site of infarction; it is merely an electrical phenomenon.

Evidence for a depressor reflex elicited from left ventricular receptors during occlusion of one coronary artery in the cat.

AbstractCirculatory responses to shortlasting occlusions of one coronary artery (left anterior descendent or right coronary artery) were studied in chloralose‐anesthetized cats. — When the carotid sinus baroreceptors were left functionally intact, coronary occlusion induced moderate reflex reductions of heart rate and blood pressure and slight increases of resistance and capacitance vessel tone in the calf muscles. When the buffering influences from the baroreceptors were largely eliminated by bilateral carotid occlusion, the reflex fall of blood pressure and heart rate became more pronounced and a clearcut vasodilatation was now observed. After cold block of the cervical vagi, the blood pressure fall upon coronary obstruction was markedly diminished, the heart rate response was reversed to a slight tachycardia and a marked peripheral vasocon‐striction ensued. After i.v. administration of local anesthetics (lidocaine 3–4 mg/kg b.wt.) the reflex response to coronary obstruction and to shortlasting occlusions of the ascending aorta were almost completely eliminated. — It is concluded that acute occlusions of one coronary artery induce a reflex bradycardia and vasodilatation, in all probability due to activation of left ventricular mechanoreceptors. The vascular responses in this inhibitory reflex seem to be significantly moderated by influences from the arterial baroreceptors.