Phenylephrine exerted a positive chronotropic and inotropic effect on isolated, spontaneously beating, atria of reserpinised rabbits. Addition of phenoxybenzamine and phentolamine resulted in a depression of control contractile amplitude. Practolol, however, was devoid of this effect. The positive inotropic response to phenylephrine was significantly antagonised by all the three blockers used, ...

The effects of tetrodotoxin on sinus node activity were studied by direct perfusion through its nutrient artery. Tetrodotoxin suppresses action potentials by blocking sodium entry into the cell. In the open-chest anesthetized dog, direct perfusion of the sinus node artery with tetrodotoxin, 1.0 /xg/ml, caused immediate sinus slowing lasting 12 to 60 minutes. This slowing was not affected by int...

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Chronotropic incompetence (CI) is sometimes observed during exercise training cardiac rehabilitation in patients who underwent surgery, however, little known which factors affect to the incidence CI and capacity those patients. Purpose Because possibility exists that sympathetic nerves might be impaired by surgical pr...

The original goal of implantable pacemakers was to prevent syncope and death due to prolonged periods of asystole from Stokes-Adams attacks and complete heart block (1). Subsequently, devices that were increasingly complex were developed to maintain atrioventricular (AV) sequential activation and to provide a better chronotropic response to exercise. Atrial based pacing (either AAI or DDD) has ...

Appropriately substituted benzylamine (BZA) derivatives, fragmented derivatives of tetrahydroisoquinolines, were found to be directly acting adrenergic beta-stimulants, exhibiting tracheal relaxing, positive chronotropic and free fatty acid (FFA) releasing activities. The chemical structures essential for manifestation of the beta-action were i) 3,4-dihydroxybenzylamine, ii) arylmethyl group at...

In some cases of complete A-V block the curve of the duration of P-P intervals showed a sudden dip with a gradual return, during or after the T wave. This positive chronotropic (accelerating) effect of ventricular systole is probably caused by the traction exerted on the right auricle by the contracting ventricle. Other cases showed a sudden rise in the curve of P-P intervals late in diastole, ...