Property of automaticity of SA nodes is because of spontaneous depolarization in –
Spontaneous phase 4 diastolic depolarization underlies the property of automaticity characteristic of pacemaker cells in the SA and atrioventricular (AV) nodes, His-Purkinje system, coronary sinus, and pulmonary veins.
All of the following are stages in the generation of an action potential in a pacemaker cell –
There are 3 main stages in the generation of an action potential in a pacemaker cell.
There is just phases 0, 3, and 4.
Resting potential of a pacemaker cell –
Pacemaker cell -maintains a resting membrane potential of -70 mV
What is the threshold potential for the initiation of a new Action Potential event in SA Node:
Resting membrane potential is: -70 mV.
Increase in membrane potential reach the threshold potential and consequently fire the next action potential.
Increased Ca2+ load is a feature in induction of –
DADs - induced by presence of an increased Ca2+ load in the cytosol and sarcoplasmic reticulum.
All of the following are likely to potentiate Delayed afterdepolarizations EXCEPT –
Antiarrhythmics with class IA and III action produce action potential and QT prolongation intended to be therapeutic but frequently causing arrhythmias due to early afterdepolarizations.
Ashman phenomenon is typically seen in –
Ashman phenomenon- type of wide QRS complex which is typically seen in atrial fibrillation.
wide QRS complex that follow a short R-R interval preceded by a long R-R interval.
This short QRS complex typically has a right bundle branch block morphology.
Most common mechanism of arrhythmia is -
Most common arrhythmia mechanism - re-entry resulting from abnormal electrical impulse conduction.
Head-up tilt (HUT) testing is useful in the evaluation of patients With –
Head-up tilt (HUT) testing is useful in the evaluation of patients with syncope in whom exaggerated vagal tone or vasodepression is suspected.
HUT is a useful Test in the diagnosis of all of the following cases EXCEPT –
HUT is relatively contraindicated in following conditions -
1. Severe CAD
2. Severe cerebrovascular disease
3. Severe mitral stenosis
4. Obstruction to left ventricular outflow -aortic stenosis
The time needed for activation of the atria and the AVN delay is represented in ECG as –
The time needed for activation of the atria and the AVN delay is represented as the PR interval of the ECG