Nursing Implications in Dysrhythmias

Comprehensive flashcards covering cardiac anatomy, physiology, electrophysiology, EKG monitoring components, and the interpretation of various rhythm strips.

Endocardium

The innermost of the three layers of the heart muscle.

Myocardium

The middle layer of the heart muscle.

Epicardium

The outermost layer of the heart muscle.

Interatrial septum

The portion of the septum that divides the right and left atria.

Interventricular septum

The portion of the septum that divides the right and left ventricles.

Cardiac output (CO)

The amount of blood pumped out of the left ventricle in $1 \text{ minute}$, with a normal range of $4 \text{ to } 8 \text{ liters per minute}$. It is calculated as $CO = SV \times HR$.

Stroke volume (SV)

The amount of blood pumped from the left ventricle with each contraction, which is approximately $70 \text{ ml}$.

Automaticity

A unique characteristic of cardiac muscle allowing it to respond to and generate its own electrical stimulus.

Excitability

The characteristic of cardiac cells that enables them to respond to an electrical stimulus.

Conductivity

The ability of cardiac cells to transmit an electrical impulse.

Contractility

The ability of cardiac cells to shorten, resulting in muscle contraction.

Sinoatrial node (SA node)

The primary pacemaker site of the heart with an intrinsic rate of $60-100 \text{ bpm}$.

Atrioventricular node (AV node)

A pacemaker site of the heart with an intrinsic rate of $40-60 \text{ bpm}$.

Ventricular muscle pacemaker rate

The intrinsic pacemaker rate of the ventricular muscle, which is $20-40 \text{ bpm}$.

Standard ECG Small Square

On ECG graph paper, one small square equals $0.04 \text{ second}$ in time and $0.1 \text{ millivolt (mV)}$ in voltage/amplitude.

Standard ECG Large Square

On ECG graph paper, one large square (5 small squares) equals $0.20 \text{ second}$.

P wave

The component of the cardiac cycle that represents atrial depolarization.

PR interval

The time it takes an electrical impulse to be conducted from the SA node to the AV node, normally measuring $0.12 – 0.20 \text{ seconds}$.

QRS complex

The component representing ventricular depolarization, with a normal duration of $0.04 – 0.12 \text{ seconds}$.

ST segment

The interval between depolarization and repolarization of the ventricles.

T wave

The component of the EKG that represents the repolarization of the ventricles.

QT interval

Shows the depolarization and repolarization of the ventricles; it is considered prolonged if it is more than half of the R-R interval or $> 0.44 \text{ secs}$.

Absolute refractory period

The time during which cardiac cells cannot be stimulated to conduct an impulse, measured from the beginning of the QRS complex to halfway through the T wave.

Relative refractory period

The time when cardiac cells have repolarized enough that some can be stimulated by a strong impulse, measured from halfway through the T wave to the end of the T wave.

6 second strip method

A rate calculation method where the number of R waves in a 6-second strip (30 large squares) is multiplied by 10.

Sinus bradycardia

A regular rhythm with a heart rate below 60 (example given is $47 \text{ bpm}$). Treatment may involve assessing the client and administering Atropine.

Atrial fibrillation

An irregular rhythm with atrial fibrillation waves occurring at a rate of $> 300$ and a varying ventricular rate.

Atrial flutter with 3:1 block

A regular rhythm with absent P waves and flutter waves at a rate of $300$, with a ventricular rate of $95 \text{ bpm}$.

2 degree AVB Type I (Wenkebach)

An irregular rhythm where the PR interval varies (e.g., $0.22-0.36$) and some atrial impulses are not conducted to the ventricles.

3 degree AVB

A regular rhythm where P waves are present but asynchronous with QRS complexes; treatment includes Pacemaker and potentially an Epi drip.

Ventricular tachycardia

A regular rhythm with absent P waves and wide QRS complexes, typically with a high rate (example given as $215 \text{ bpm}$); requires CPR and defibrillation.