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At least 145 records · Page 8Linked to original sources
PubMed1995

The role of nitric oxide in the initiation and in the duration of some vasodilator responses in the coronary circulation.

In the coronary bed vasodilation can be mediated by several mechanisms including endothelium-produced nitric oxide. To examine the contribution of nitric oxide, three different techniques to cause vasodilation in the coronary vessels were used in the anaesthetized dog: intracoronary injection of 1 microgram acetylcholine, sudden reduction of the aortic blood pressure inducing a myogenic response and transient occlusion followed by release of the left circumflex coronary artery causing reactive hyperaemia. Each manoeuvre was performed before and after intracoronary administration of 100 mg N-nitro-L-arginine, an inhibitor of the synthesis of nitric oxide. In contrast to previous investigations, the inhibition of nitric oxide synthesis was prevented from causing an increase in blood pressure by the use of a blood-pressure-compensating device. The results observed during each of the three techniques, suggest that the initial cause of the vasodilatation is not the result of the increase of the production of nitric oxide. However, subsequent to the initiation of vasodilation, an increase in the shear stress can result in an increase in the release of nitric oxide from the vascular endothelium, thus prolonging the vasodilatation obtained using each technique.

Acetylcholine↗
PubMed1987

[Coronary reserve: a dynamic evaluation of coronary circulation].

Measuring the coronary reserve is a way of evaluating pathologies of the large coronary vessels as well as of coronary microcirculation. In man, measurement of the coronary sinus blood flow by the thermodilution method can be used to determine the increase in flow induced by selective injection of a contrast medium into the left coronary artery or by intravenous injection of dipyridamole. Such measurements have been performed in subjects with normal coronary blood flow and left ventricular function, in patients with cardiac or systemic diseases likely to alter coronary perfusion (e.g. atheromatous coronary disease, dilated cardiomyopathy, scleroderma, sarcoidosis) and in patients who had undergone heart transplantation. Flow and resistance reserves have been calculated from the maximal/basal coronary flows ratio and from the minimal/basal coronary resistance ratio. The results obtained provided information on the repercussions of coronary stenosis on myocardial perfusion and on alterations of coronary microcirculation in pathologies respecting the main coronary arteries. In addition, changes in coronary reserve induced by some pharmacological agents may be used to evaluate the effects of certain cardiovascular therapies.

Cardiomyopathy, Dilated↗
PubMed1993

[Doppler microprobe allows evaluation of local coronary circulation].

The local coronary flow in 42 patients (mean age: 59 +/- 9 years) with ischemic heart disease was assessed by means of an 0.018" intracoronary Doppler guidewire. Study population was divided into two groups: group I--"normal vessels" (diameter stenosis < 30%) and group II--"stenosis vessels" (diameter stenosis > 60%). Measurements of: averaged peak velocity (APV), diastolic-systolic velocity ratio (DSVR) were performed in proximal segments of normal vessels and proximally to stenosis in group II. APV and DSVR were recorded at rest (bas) and during papaverine induced hyperemia. Coronary flow reserve (CFR) was calculated as ratio hyperemic and resting values of APV. Mean value of APV at rest was highest for left main stem, lowest for venous by-passes (SVBG) but did not differ among three coronary arteries (LAD, LCX, RCA). CFR value was significantly higher for group I then for group II (2.75-3.3 vs 1.8-2.0) but did not differ significantly among particular arteries in both groups. Mean value of DSVRbas in both examined groups was lowest for right coronary artery and for SVBG (ca. 1.0) and did not change significantly during hyperemia. This value was significantly higher (ca. 2.0) for left coronary arteries (LAD, LCX) then for RCA and SVBG and significantly decreased after administration of papaverine.

Aged↗
PubMed2005

Retained percutaneous transluminal coronary angioplasty guidewire in coronary circulation.

Percutaneous coronary interventions have been a widely accepted method as a treatment option in patients with coronary artery disease. Unfortunately, the rare procedure-related complications pose a potential risk for patients, either during catheterization or afterwards. We present a case, in which we found of a retained guidewire segment in the right coronary artery.

Angioplasty, Balloon, Coronary↗
PubMed1995

[The effects of sevoflurane on the coronary circulation in the instrumented dog with or without coronary stenosis].

The effects of sevoflurane on the coronary circulation were investigated in the instrumented dogs with or without coronary stenosis. A-V block was produced by injection of formalin into A-V node to control heart rate at 120 beats.min-1 by pacing and mean systemic blood pressure was held constant at 65 mmHg with the pressurized blood reservoir. Left anterior descending coronary artery was cannulated with stainless steel tube supplied from the femoral artery. Total coronary flow was measured with an electromagnetic flow probe and the regional myocardial blood flow was calculated using color microsphere technique. Coronary resistance was reduced with the increasing end-tidal concentrations of sevoflurane up to 1.2 MAC. An adjustable screw clamp was used to reduce the coronary flow down to 50% of control value. Inner/outer ratio of regional myocardial blood flow decreased with stenosis, but was unaffected with 1.2 MAC of sevoflurane. We concluded that 1.2 MAC of sevoflurane was not strong enough to dilate the coronary artery to produce the transmural steal phenomenon in the dog with coronary stenosis. Further investigations are needed to clarify how hemodynamic factors influence the transmural steal phenomenon in myocardium.

Anesthetics↗
PubMed1981

[Acute myocardial infarct: the importance of the coronary circulation type in the atherosclerotic lesion of the coronary arteries, the development of thromboses, the localization of the acute infarcts and their evolution].

Analysis was made to 270 deceased with acute myocardial infarction. The signs discussed were: type of coronary circulation, sex and age, nosological belonging, atherosclerosis affection and allocation of thrombosis in coronary arteries. The acute infarction lesions were characterized according to site, layers involved, left ventricular mass engaged mural thrombosis and acute aneurysms ruptures. Consideration was given to myocardiosclerosis, postinfarction cicatrices and chronic aneurysms, hypertrophic rate, duration of recent infarction, thromboembolic complications and death causes. Essential discrepancies were found for the separate coronary types as regards stenosis distribution, predominating affection of separate coronary vessels, site of coronary thrombosis, infarction, resp., infarction extent (layer and mass), rupture incidence, acute aneurysms and postinfarction cicatrices. The study revealed that left coronary type was the most unfavourable terrain for acute myocardial infarction.

Adult↗
PubMedDate not supplied

[Coronary circulation study of a pilot in flight].

Coronary circulation was examined in pilots of transport aircraft during 14 flights by Doppler cardiography (with respect to changes in the integrated level of the reflected signal in systole). At certain flight stages the coronary circulation efficiency varied substantially. It is concluded that coronary circulation should be monitored during pilot training and aircraft testing in order to standardize flight loads.

Aerospace Medicine↗
PubMedDate not supplied

[Influence of electrical stimulation of the heart on coronary circulation (author's transl)].

Coronary perfusion was measured in anaesthetized dogs under sinus rhythm, after creation of an acute AV-block, and during pacing of the heart at frequencies of 60 to 150 min-1. With increased heart rate coronary perfusion was enhanced. The close relation between heart rate and coronary perfusion is not influenced by artificial stimulation. The improvement in coronary circulation under pacing after creating of the A-Vblock is due exclusively to the rise in heart rate.

Animals↗
PubMed1990

[Effect of the calcium antagonist nisoldipine on coronary circulation and myocardial ischemia in temporary coronary occlusion].

Sixteen patients undergoing PTCA of a significant lesion of the left anterior descending coronary artery received either 0.3 mg nisoldipine or placebo intravenously. Immediately before and during balloon inflation the following parameters were measured: aortic pressure, post-stenotic pressure, coronary occlusion pressure, diastolic pulmonary artery pressure, coronary sinus flow (thermodilution), and intracoronary ECG. After placebo there were no statistically significant changes. Nisoldipine led to a decrease in aortic pressure from 109 +/- 12 to 93 +/- 11 mm Hg (p less than 0.05) before, and from 103 +/- 14 to 92 +/- 8 mm Hg (NS) during balloon inflation. In contrast, coronary occlusion pressure remained unchanged. Heart rate increased from 80 +/- 13 to 96 +/- 16/min before (p less than 0.05), and from 87 +/- 18 to 97 +/- 17/min during balloon inflation (NS). Coronary sinus flow was increased from 95 +/- 16 to 116 +/- 13 ml/min before balloon inflation (p less than 0.01), and from 70 +/- 25 to 86 +/- 26 ml/min during balloon inflation (NS). ST-segment depression or elevation, severity of angina pectoris, and the diastolic pulmonary artery pressure remained unchanged. Thus, 0.3 mg nisoldipine led to a peripheral vasodilatation. While the aortic pressure decreased, coronary occlusion pressure remained unaffected. This could be explained by a marked dilatation of collateral vessels due to nisoldipine. However, myocardial ischemia remained unaffected as a result of the constant coronary occlusion pressure.

Adult↗
PubMed1989

[The effect of pancuronium and norcuron on hemodynamics, coronary circulation and myocardial oxygen consumption in coronary surgery patients].

The effects of the non-depolarizing muscle relaxants pancuronium (Pancuronium) and vecuronium (Norcuron) (0.1 mg/kg) on myocardial blood flow, myocardial oxygen consumption, myocardial lactate balance, cardiovascular dynamics and electrocardiogram were studied in two groups of eight patients undergoing coronary artery bypass surgery. After an introduction of anaesthesia with 0.015-0.02 mg/kg rohypnol, isoflurane (0.5 Vol%) and N2O/O2 neuromuscular blockade was induced with pancuronium or vecuronium combined with a single dose of 0.005 mg/kg fentanyl. Measurements and electrocardiogram were performed before anaesthesia, in steady state of anaesthesia and after relaxation with pancuronium or vecuronium, combined with fentanyl. The measurements consisted of heart rate (HR), cardiac index (CI), stroke volume index (SVI), mean arterial pressure (AP), total peripheral resistance (TPR), pulmonary arterial pressure (PAP), pulmonary capillary wedge pressure (PCWP), right atrium pressure (RAP), myocardial blood flow (MBF), coronary vascular resistance (CVR), myocardial oxygen consumption (MVO2), coronary ateriomixed venous oxygen content difference (AVDO2cor), myocardial lactate extraction (LE) and rate pressure product (RPP). In the vecuronium group heart rate (HR) decreased significantly greater (21%) than in the pancuronium group (9%). Therefore myocardial oxygen consumption (MVO2) and coronary blood flow (CBF) diminished more in the vecuronium (48% resp. 35%) than in the pancuronium group (31% resp. 18%). The higher metabolic demand in the pancuronium group induced a significantly lower coronary vascular resistance (CVR). All the other hemodynamic parameters did not differ significantly in both patients groups. In all the patients we could not observe ST-segment depressions or elevations in the ECG, increases of PCWP or myocardial lactate productions.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed2005

Perfusion of the isolated trout heart coronary circulation with red blood cells: effects of oxygen supply and nitrite on coronary flow and myocardial oxygen consumption.

A method for perfusion of the isolated trout heart coronary circulation with red blood cells (RBCs) was developed. The method was used to analyse the influence of RBC perfusion on myocardial O(2) supply and O(2) consumption and to test the hypothesis that nitrite is converted to vasoactive nitric oxide in the RBC-perfused coronary circulation. Perfusion with RBCs significantly increased myocardial O(2) supply and O(2) consumption by increasing the incoming O(2) concentration and the O(2) extraction. Coronary flow did not differ between RBC perfusion and saline perfusion, but RBC perfusion established a strong linear increase in myocardial O(2) consumption with coronary flow. Nitric oxide was measured in the atrial effluent of the preparation. Perfusion with saline under hypoxic conditions was associated with NO production. The nitric oxide synthase inhibitor L-NA obliterated this NO production and significantly decreased coronary flow, showing that the NO was vasoactive and probably of endothelial origin. RBC perfusion at low P(O(2)) similarly caused an L-NA-inhibitable NO production. The change in NO production upon subsequent nitrite addition, by contrast, was not inhibited by L-NA. Nitrite entered trout erythrocytes independent of degree of oxygenation, but the O(2) saturation of RBCs showed a major decrease in the coronary circulation, and [NO(2)(-)] decreased while methaemoglobin rose, suggesting that deoxyHb-mediated reduction of nitrite to NO may have occurred. However, other possibilities (e.g. NO(2)(-)-->NO conversion in myocardial cells) cannot be excluded. The NO formation associated with nitrite had no effect on coronary flow, possibly because NO was produced after the resistance vessels.

Analysis of Variance↗