monitoring and analyzing electrocardiograms

Cardiac Conduction System

generates and coordinates your heartbeat through the distribution of the electrical impulses.

Automaticity/autorhythmicity

Cardiocytes to contract on its own

Sinoatrial (SA) node

The conduction pathway begins with an action potential generated by the internal pacemaker

Pacemaker cells

Comprising the SA node establishes the rate at which the heart contracts

Atrioventricular (AV) node

receives impulses from the sinoatrial node and transmits them to the atrioventricular bundle

Purkinje fibers

distribute the stimulus throughout the myocardium of the ventricles

Sinus rhythm

normal heart rhythm

Ectopic focus

spontaneous signals created in any area other than the SA node

Nodal rhythm

This results a normal but slower heart rate

Arrhythmia

any abnormal cardiac rhythm

occurs when electrical signals for the cardiac conduction system are blocked or delayed

electrocardiogram

record of the electrical activity of the heart

p wave

depolarization of the atria

qrs complex

depolarization of hearts ventricle

t wave

repolarization of ventricles before ventricular diastole

segments and intervals

period between waves

Segment - Extend from one wave end to another

Interval - More variable and include at least one wave

PR interval

represents the period of time from the start of atrial depolarization to the start ventricular depolarization. (start of P wave to start to QRS)

QT interval

represents the period of time required for the ventricles to depolarize and depolarize in a single cycle (start of QRS to end of T)

PQ segment

indicates the length of time for an impulse to spread from the SA node to the AV node (end of P wave to start of QRS)

ST segment

represents the ventricles in a depolarized state prior repolarization (end of QRS to start of T wave)

Atrioventricular bundle

* **a bundle of modified heart muscle that transmits the cardiac impulse from the atrioventricular node to the ventricles causing them to contract**

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* receives a signal from AV node and splits into left and right bundles and impulses along the interventricular septum towards the apex

steps of cardiac conduction system

1. sa node fires
2. excitation spreads through myocardium across atria
3. av node fires
4. excitation spreads down av bundle
5. subendocardial conducting network distributes excitation through ventricular myocardium

heart rate bpm

1/cyclic time x 60

ventricular diastole

QT interval - cyclic time

myocardial infraction

disorder of heart such as abnormal slowing, speeding, irregular rhythms, injury and death of muscle tissue

Maximum heart rate equals

60 / average QT interval

an absent of P wave or QRS complex

indicates the electrical impulse was blocked before it reached the ventricles

short interval

reflects an impulse which followed a shorter route

long interval

reveals that an impulse has been slowed or has taken a longer route

What happens when cardiac cells are damaged?

they no longer are able to conduct electrical impluses that flow through them