Pacemaker therapy in sino-atrial block complicated by paroxysmal tachycardia.

تأثیــر نیکــل بر مسدود کردن جریان یونــی گذرای کلسیمــی سلولهای گــره سینوسی ـ دهلیزی دست نخورده و سالم قلب خرگوش

The mammalian sino-atrial node is not a uniform tissue in histological and electrophysiological terms. The differences in ionic currents underlying the regional differences in electrial activity are only just beginning to be understood. One of the ionic currents it is thought to play a role in the center of sino-atrial node for action potential upstroke should be transient Ca+2 current ...

Paroxysmal atrioventricular block precipitated by an atrial premature beat. What is the mechanism?

A 65 year-old woman presented with two episodes of syncope. She developed paroxysmal atrioventricular (AV) block when an ECG was being recorded (Fig. 1). She developed at least one other similar episode. Then, she developed complete AV block with a stable escape ventricular rhythm of about 30 bpm during which an atrial premature beat was conducted (Fig. 2). Isoproterenol was administered which ...

Pacing mode selection in patients with sick sinus syndrome.

INTRODUCTION SICK SINUS SYNDROME The sinus node is composed of a collection of specialised pacemaker cells embedded in a fibrous matrix that lies in the sulcus terminalis between the superior vena cava and the right atrial appendage. The sinus node serves as the primary cardiac pacemaker and controls the heart rate in normal individuals. Recent research indicates, that the sinus node is a heter...

Comparison of Hyperpolarization-Activiated Current “if ” on the Rate of Spontaneous Activity and Cycle Length before and after Cutting of Atrial Muscle away from Intact Sinoatrial Node of Rabbit

It has been shown that the hyperpolarization-activated current “if” that is blocked by 2 mM Cs+ plays a minor role on pacemaker activity of the center and a major role on activity of the periphery of rabbit intact sino-atrial node. On the other hand some investigations showed that if the atrial muscle, surrounding the sino-atrial node, is cut away there is a shift in leading pacemaker site from...

Paroxysmal Atrial Tachycardia with Block around the Ectopic Pacemaker. Report of a Case.