Myocardial stimulation

Theophylline. Is a smooth muscle relaxant, diuretic, and a myocardial stimulant (not psychoactive stimulant). It is undesirable because it may cause nausea and dizziness and should therefore be removed. 

Coronary artery disease - Myocardial stimulation produced by hydralazine can cause anginal attacks and EGG changes of myocardial ischemia. The drug has been implicated in the production of Ml. Use with caution in patients with suspected coronary artery disease. 

Labetalol administration may precipitate or aggravate CHF because of decreased myocardial stimulation. 

I 85. Angina pectoris I 86. Myocardial stimulation I 87. Bronchial asthma... 

Another study of the effects of I on the cardiovascular systemic concluded that, in dogs anesthetized with sodium pentobarbital, the response of blood pressure to intravenous administration of I is a resultant of two separate effects a direct myocardial stimulation that was stopped with dichlorolsoproterenol and a stimulation of vascular smooth muscle that results in a slight increase in renal arterial pressure and a slight decrease in renal arterial flow. Neither atropine nor dichlorolsoproterenol affected these vascular effects. Injections of 1 into a jugular vein or a renal artery had no consistent effect on catecholamine concentrations in plasma taken from a femoral artery or a renal vein. In seven experiments in which I at 21-35 mg/kg was injected into a jugular vein, the mean blood pressure increased from 176/125 + 22/11... 

Alangium chinense (Lour.) Harms. a Jiao Feng (root) dl-Anabasine.33 Cause myocardial stimulation, increase contractility, may cause fibrillation and increase blood pressure. 

The pressor response to ephedrine is due in part to peripheral constriction and in part to myocardial stimulation. Vasoconstriction can be demonstrated by intra-arterial injection, but compared to epinephrine, ephedrine is only about one thousandth as active. This would imply that the cardiac effect is predominant in increasing the arterial pressure. This, however, is difficult to demonstrate. In perfused hearts, ephedrine produces only minor stimulation and cardiac depression appears if the drug is repeated. 

Seed RF, Chamberlain JH. Myocardial stimulation by pancuronium bromide. Br J Anaesth 1977 49(5) 401-7. 

In medicine too these compounds are of interest and a variety of pharmaceutical products are based on heterocyclic thioxo compounds containing nitrogen atoms in the ring. Among these are diuretics, aiiti-malarials, antitumors, cytostatica, coronary vasodilators, myocardial stimulants, products with antimitotic activity or with dermatological and disinfectant properties. 

Methyphenidate (releases NE peripherally NE, DA, 5-HT centrally) Myocardial stimulation Obesity (rarely) Insomnia Anxiety Tachycardia Hypertension Cardiac arrhythmias Chronic use leads to dependence Can result in hemorrhagic stroke in patients with underlying disease Long-term use can cause paranoid schizophrenia... 

Dohhna ML, et al. Myocardial stimulation threshold in patients with cardiac pacemakers effect of physiologic variables, pharmacologic agents, and lead electrodes. Cardiol Clin 1985 3 527. 

Failure to Capture. The absence of myocardial depolarization despite appropriate stimulus delivery from the pulse generator defines failure to capture. Failure to capture is usually diagnosed fiom the ECG by the occurrence of visible pacing artifact without resultant paced P-waves or QRS complexes (Fig. 16.2). Failure to capture can, however, result in no visible stimulus artifact despite stimulus output from the generator when there is complete lead fracture (see above). Failure to capture results from lead failure, lead-tissue interface problems, and increases in myocardial stimulation threshold (Fig. 16.3). 

A detailed study has been made of the unique combination of properties exhibited by the hypotensive imidazolidine (XXXVI, Ro 7 2956). In dogs, a direct peripheral vasodilation is combined with a non-adrenergic myocardial stimulant activity reminiscent of theophylline. ... 

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