T. Cardiac Dysrhythmias Flashcards
Dysrhythmias
Abnormal cardiac rhythms
Automaticity
ability and initiation of an impulse
the property of cardiac cells to generate spontaneous action potentials.
Contractility
the way the heart responds to the impulse by contracting
Conductivity
how the impulse is transmitted
Excitability
the way it’s electrically stimulated
Autonomic Nervous System
• controls rate, speed of conduction, strength of contraction
Parasympathetic Nervous System
- decrease rate, slow conduction and decrease force of contraction
- Stimulation of the vagus nerve causes a decreased rate of firing of the SA node and slowed impulse conduction of the AV node
Sympathetic Nervous System
- increase rate and force of contraction
* Stimulation of the sympathetic nerves increases SA node firing, AV node impulse conduction, and cardiac contractility
Electrocardiogram
Measure the heart’s electrical activity as waveforms.
Each beat is seen through one wave
PQRST = 1 heart beat
Depolarization/
Repolarization
Depolarization makes the inside of the cell + due to movement of Na
Repolarization makes the inside negative again
12 Lead EKG
- Six leads measure electrical forces in the frontal plane.
* Six leads measure electrical forces in the horizontal plane (precordial leads).
Normal Sinus Rhythm
- the rhythm of a healthy heart
- Sinus node fires 60–100 bpm.
- Follows normal conduction pattern
QT interval
- Represents total time required for ventricular depolarization and repolarization
- represents the absence of electrical activity in heart
P wave
Atrial depolarization
• defects often due to atria enlargement
PR Segment
Electrical impulse traveling through atrioventricular (AV) node
QRS complex
Ventricular depolarization
T wave
Ventricular repolarization
• inverted T wave in myocardial damage
Sinus Bradycardia
Cardiac Arrhythmias
- Slow but regular heart rate because sinus node discharges at rate <60 beats per minutes
- Can be normal, especially in athletes
- Hypothyroidism also causes SB
- The PR interval is normal, and the QRS complex has a normal shape and duration.
Treatment
Atropine (muscle relaxant)
Pacemaker may be required
Sinus Tachycardia
Cardiac Arrhythmias
- Fast but regular heart rate because sinus node discharges at rate >100 beats per minutes
- Normal in response to stress, exercise, fever, pain, anxiety.ª«
- The PR interval is normal, and the QRS complex has a normal shape and duration.
Treatment
- Determined by underlying cause
- ß-adrenergic blockers to reduce HR and myocardial oxygen consumption
- Antipyretics to treat fever
- Analgesics to treat pain
Arrhythmias
a problem with the rate or rhythm of your heartbeat. It means that your heart beats too quickly, too slowly, or with an irregular pattern.
Atrial Flutter
Cardiac Dysrythmias
- Atria of heart contracting rapidly in characteristic flutter waves
- 1 ventrible beat for evey 4 atrial
- Atria rate is 250 -350 beats/minute. The ventricular rate varies according to the conduction rate.
- Seldom normal
- Saw tooth waves are regular.
Treatment
• Primary goal is to slow ventricular response by increasing AV block
- High ventricular rates (>100) and loss of the atrial “kick” can decrease CO and precipitate HF, angina
- Risk for stroke due to risk of thrombus formation in the atria
Atrial Fibrillation
Cardiac Dysrhythmias
- Total disorganization of atrial electrical activity due to multiple ectopic foci, resulting in loss of effective atrial contraction
- Can result in decrease in CO due to ineffective atrial contractions (loss of atrial kick) and rapid ventricular response
- Thrombi may form in the atria as a result of blood stasis.
Tr4eatment:
- Decrease ventricular rate.
- Prevent cerebral embolic events.
Junctional Dysrhythmias
Dysrhythmias that originate in area of AV node
SA node has failed to fire, or impulse has been blocked at the AV node.
Premature Ventricular Contractions
• Contraction originating in ectopic focus of the ventricles
• Premature occurrence of a wide and distorted QRS complex
• Can be Multifocal, unifocal, ventricular bigeminy, ventricular trigeminy, couples, triplets, R-on-T phenomena
> Multifocal – happen may time in a row
> Unifocal – happen evey now and then
> Ventricular bigeminy – have 2 in a row
> Ventricular trigeminy – have 3 in a row
> Couples – always happen in pairs of 2
> Triplets – always happens in pairs of 3
