Activation of the carotid body increases directly recorded cardiac sympathetic nerve activity and coronary blood flow in conscious sheep

Activation of the carotid body (CB) using intracarotid potassium cyanide (KCN) injection increases coronary blood flow (CoBF). This increase in CoBF is considered to be mediated by co-activation of both the sympathetic and parasympathetic nerves to the heart. However, whether cardiac sympathetic nerve activity (cardiac SNA) actually increases during CB activation has not been determined previously. We hypothesized that activation of the CB would increase directly recorded cardiac SNA, which would cause coronary vasodilatation. Experiments were conducted in conscious sheep implanted with electrodes to record cardiac SNA and diaphragmatic electromyography (dEMG), flow probes to record CoBF and cardiac output and a catheter to record arterial pressure. Intracarotid KCN injection was used to activate the CB. To eliminate the contribution of metabolic demand on coronary flow, the heart was paced at a constant rate during CB chemoreflex stimulation. Intra-carotid KCN injection resulted in a significant increase in directly recorded cardiac SNA frequency (from 24±2 to 40±4 bursts/minute; p<0.05) as well as a dose-dependent increase in mean arterial pressure (79±15 to 88±14 mmHg; p<0.01) and CoBF (75±37 Vs 86±42 mL/min; p<0.05). The increase in CoBF and coronary vascular conductance to intracarotid KCN injection was abolished after propranolol infusion, suggesting that the increased cardiac SNA mediates coronary vasodilatation. The pressor response to activation of the CB was abolished by pre-treatment with intravenous atropine but there was no change in the coronary flow response. Our results indicate that CB activation increases directly recorded cardiac SNA which mediates vasodilatation of the coronary vasculature.

Vasospastic Angina and its Relationship with the Coronary Microcirculation

Vasospastic angina is an important cause of chest pain due to coronary artery vasospasm that is related to poor quality of life and can lead to myocardial infarction, arrhythmias and death. Since its first description as “Prinzmetal or variant angina” which was believed to be a focal spam that occurred in non-obstructed epicardial coronary arteries, physician and researchers were gradually confronted with the clinical reality and came to the conclusion that the coronary artery vasospasm was considerably more polymorphic than initially described. Although mechanism leading to vasospastic angina is not completely understood, nowadays the medical community acknowledges that it exhibits a large variability in clinical practice ranging from focal to diffuse epicardial vasospasm. Main proposed mechanisms are impairment of parasympathetic activity, coronary vascular and microvascular dysfunction due to blunted response to nitric oxide endothelium-dependent coronary vasodilatation, increased release of vasoconstricts, and oxidative stress.

Myocardial Infarction in a Premenopausal Woman on Leuprolide Therapy

Premenopausal women with chest pain syndrome may have nonatherosclerotic coronary arteries with abnormal coronary flow. Estrogens have cardioprotective effect improving coronary vasodilatation. This case report discusses the consequences of leuprolide use by decreasing estrogen levels which led to acute myocardial infarction.

Cardiovascular Activity of Labdane Diterpenes fromAndrographis paniculatain Isolated Rat Hearts

The dichloromethane (DCM) extract ofAndrographis paniculataNees was tested for cardiovascular activity. The extract significantly reduced coronary perfusion pressure by up to24.5±3.0 mm Hg at a 3 mg dose and also reduced heart rate by up to49.5±11.4 beats/minute at this dose. Five labdane diterpenes, 14-deoxy-12-hydroxyandrographolide (1), 14-deoxy-11,12-didehydroandrographolide (2), 14-deoxyandrographolide (3), andrographolide (4), and neoandrographolide (5), were isolated from the aerial parts of this medicinal plant. Bioassay-guided studies using animal model showed that compounds, (2) and (3) were responsible for the coronary vasodilatation. This study also showed that andrographolide (4), the major labdane diterpene in this plant, has minimal effects on the heart.