ECG Leads Quiz

Pressure Calculation and Units

• Pressure is calculated using the equation: Pressure = Force / Area.
• Common units for measuring pressure include Pascals (Pa), mmHg, and atm (atmospheres).

Blood Movement Forces

• The study of forces affecting blood movement is known as hemodynamics.

Vascular Beds Arrangement

• In a parallel arrangement of vascular beds, each bed receives a fraction of the total blood flow, allowing for independent control of blood distribution.

Cardiac Conduction System

• The cardiac conduction system regulates the heart's rhythm by conducting electrical impulses, initiating contractions.

Cardiac Action Potential

• The cardiac action potential includes phases of depolarization and repolarization, critical for heartbeats.
• Sodium channels facilitate the rapid initiation of the cardiac action potential.

Impulse Conduction Factors

• Impulse conduction in the heart is mainly determined by cell membrane properties and the type of ion channels present.

Fast Impulse Conduction

• Gap junctions allow for fast impulse conduction due to direct electrical connections between cardiac cells.

Refractory Period Determinants

• The refractory period of the cardiac impulse is significantly influenced by potassium ion dynamics.

Parasympathetic Nervous System Effects

• The parasympathetic nervous system primarily decreases heart rate by acting on the sinoatrial node.

Ventricular Fibrillation Characteristics

• Ventricular fibrillation (v-fib) is characterized by erratic electrical activity in the heart, leading to ineffective pumping and lack of blood flow.

Pre-excitation Syndrome and High Ventricular Rates

• High ventricular rates in pre-excitation syndrome can be caused by re-entry circuits due to accessory pathways.

3rd Degree AV Node Block

• In 3rd degree AV node block, there is complete dissociation between atrial and ventricular activity, causing a slower ventricular escape rhythm.

Hydrostatic Pressure Changes

• Moving from supine to standing position increases hydrostatic pressure in the feet due to gravitational effects.

Blood Flow in Capillaries

• When transitioning to a standing position, blood flow through the capillaries in the feet may decrease initially due to pooling of blood while muscles adjust.

Ohm's Law and Blood Flow

• Ohm's law for blood flow is represented as: Flow = Pressure Difference / Resistance.

Flow Rate Relationships

• The relationship between flow rate, pressure difference, and vessel radius is described by Poiseuille's law.

ECG Standard Leads

• A standard bipolar limb lead in an ECG is Lead I, which compares the potential difference between the left arm and right arm.

Heart Rate Calculation

• The formula to determine heart rate in beats per minute (BPM) from the R-R interval is: HR = 60 / R-R interval (in seconds).

Arrhythmias Characteristics

• Atrial fibrillation is characterized by an irregular baseline and undiscernable P waves, with irregular R-R intervals.
• Ventricular tachycardia features wide QRS complexes with rapid firing from a single ectopic ventricular focus.

Cardiac Pacemakers

• Cardiac pacemakers, primarily located in the sinoatrial node, are responsible for initiating heartbeats and maintaining the regular rhythm.

Effective Refractory Period Extension

• The most effective way to extend the effective refractory period (ERP) in the ventricle is by increasing potassium channel activity.

Autonomic Regulation of Cardiac Electrophysiology

• Autonomic regulation plays a critical role in cardiac electrophysiology, influencing heart rate and conduction velocity through sympathetic and parasympathetic effects.

Automaticity Initiation

• Impulse initiation (automaticity) in the heart is primarily driven by pacemaker cells in the sinoatrial node.