1,721,024 research outputs found
PET measurement of the coronary flow reserve and microcirculatory function
No full textThis review article discusses some of the potentially beneficial effects of calcium antagonists on the coronary microcirculation. These include their vasodilating action on coronary resistance vessels as well as their effects on extravascular resistance (i.e. intramyocardial pressure). Examples are presented of how the non-invasive measurement of myocardial blood flow and flow reserve by means of positron emission tomography (PET) can contribute to the understanding of the effects of drug treatment on the coronary microcirculation. The action of calcium antagonists on the coronary microcirculation can contribute to explain the efficacy of these drugs against ischemia and ischemia-reperfusion damage
Myocardial hibernation vs repetitive stunning in patients.
No full textMyocardial hibernation is a state of persistently impaired left ventricular function in patients with coronary artery disease that was thought to be caused by a chronic reduction in resting myocardial blood flow in a segment subtended by a diseased coronary artery. However, recent studies using positron emission tomography have demonstrated that absolute myocardial blood flow (ml/min/g) to hibernating myocardium is within normal limits in most patients. If resting flow is not reduced, one must therefore suspect an alternative "trigger" for hibernation that is still a consequence of coronary artery disease and ischemia. We suspect that hibernating myocardium may be the result of repetitive myocardial stunning. Myocardial stunning is the reversible contractile dysfunction occurring after a period of myocardial ischemia that persists for a period of time despite the return of blood flow to normal. Myocardial stunning has been demonstrated in humans in the setting of thrombolysis, coronary angioplasty, coronary artery bypass surgery, and coronary artery spasm. Furthermore, stunning has been demonstrated after exercise in patients with coronary artery disease, and recent studies have provided evidence that repetitive episodes of exercise-induced ischemia can lead to cumulative and prolonged left ventricular dysfunction
Blood flow in myocardial hibernation
No full textMyocardial hibernation is a state of persistently impaired left ventricular function in patients with coronary artery disease that improves after revascularization. it was thought to be caused by a chronic reduction in resting myocardial blood flow in a segment subtended by a diseased coronary artery. However, recent studies using positron emission tomography have demonstrated that absolute myocardial blood flow (mL/min/g) to hibernating myocardium is within normal limits in most patients. The authors hypothesize that hibernating myocardium may be the result of repetitive myocardial stunning, that is, the reversible contractile dysfunction occurring after an episode of myocardial ischemia despite the return of blood flow to normal. Myocardial stunning has been demonstrated in humans in different clinical settings, and recent studies have provided evidence that repetitive episodes of exercise induced ischemia can lead to cumulative and prolonged left ventricular dysfunction akin to that observed in hibernating myocardium
Assessing baroreflex gain from spontaneous variability in conscious dogs: role of causality and respiration
No full textBasal and hyperaemic myocardial blood flow in regionally denervated canine hearts: an in vivo study with positron emission tomography
No full textNicotine addiction and coronary artery disease: Impact of cessation interventions
No full textCigarette smoking is the leading preventable cause of death worldwide, and a considerable proportion of smoking-related fatalities are attributable to coronary artery disease (CAD). The detrimental effects of smoking span all stages in the development of CAD ranging from the early functional alterations in the endothelium and the microcirculation to the late clinicopathological manifestations of atherosclerotic plaques. Smoking results in the generation of free radicals and increased oxidative stress which plays a central role in the pathogenetic mechanisms leading to atherosclerotic disease. It causes reduced nitric oxide bioavailability and lipid peroxidation which are crucial initial steps of plaque formation. Furthermore, smoking enhances leukocyte and platelet activation and promotes local and systemic inflammation, which contribute to plaque progression and maturation. Finally, alterations in fibrinolytic and prothrombotic factors create a pro-thrombogenic environment which harbours the risk of plaque rupture and thrombosis. In smokers, the cessation of smoking is the most important intervention for cardiovascular risk reduction. Total mortality can be reduced by 36% which is comparable to established modern secondary preventive therapies. Nonetheless, non-aided cessation attempts are notoriously poor with a success rate of less than 10%. Patient counselling and pharmacological therapies are important aides for smoking cessation and can improve success rates by two to threefold. However, there is still need for improved strategies of smoking cessation to reduce the high socioeconomic impact of smoking. © 2010 Bentham Science Publishers Ltd
Sympathetic activation during treadmill exercise in the conscious dog: assessment with spectral analysis of heart period and systolic pressure variabilities.
No full textHeterogeneity of resting and hyperemic myocardial blood flow in healthy humans
No full textObjective: Absolute myocardial blood flow (MBF) is not well-defined in large normal populations, and appears to be heterogeneous in both humans and animals. These factors contribute to the difficulties in defining resting MBF to hibernating myocardium. We therefore assessed absolute baseline and hyperemic MBF in a large population of normal humans. Methods: MBF was quantified by positron emission tomography with oxygen-15-labeled water at baseline and during hyperemia induced by either adenosine or dipyridamole in 131 men and 38 women, aged 21-86 (mean 46+/-12) years. MBF was corrected for workload using the rate-pressure product (RPP). Results: Uncorrected baseline MBF ranged from 0.590 to 2.050 (mean 0.985+/-0.230) ml/min/g (coefficient of variation=27%), and corrected MBF from 0.736 to 2.428 (mean 1.330+/-0.316) ml/min/g (coefficient of variation=24%). MBF in the inferior region was significantly (P<0.0001) lower than either the anterior or lateral regions. Baseline MBF in females was significantly (P<0.001) higher than in males. Conclusions: These results confirm the heterogeneity of MBF in normals and highlight the difficulty in establishing the lower limit of normal MBF. (C) 2001 Elsevier Science B.V. All rights reserved
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