Paroxysmal supraventricular trachycardia (PSVT):
(Paroxysmal atrial tachycardia) - PSVT
-QRS normal, but frequent, P and T wave may be superimposed because of high heart rate
What clinical symptoms are associated with PSVT?
Low bp, dizziness
Sinus Node Dysfunction/Arrest:
SA node stops firing (can be for fraction of second (slight lengthening bw P and T wave) or full seconds of delay
What is a conduction/heart block?
Delay or complete block of the electrical impulse as it travels from the sinus node to the ventricles.
- Level of block or delay may occur in AV node or HIS-Purkinje system
- Heart beat may be irregular
First degree block:
Slow conduction
- Abnormally long PR interval (>.2 sec)
- ECG otherwise normal
Second degree block:
Some atrial impulses transmit through AV node, not all do, due to slower than normal conduction
-Some but not all P waves are associated with a QRS & T wave
Third degree block:
No impulses transmitted through AV node - Atrial and ventricular rates independent
- P waves and QRS are totally dissociated in ECG
- Ventricular rate likely slower than normal because of alternate pacemaker –> often slow enough to impair cardiac output
Premature atrial contractions (PACs):
Early extra beats that originate in the atria.
- Normal complex w/o typical delay. It comes too early and butts up on the previous T wave
- Bc it came early, there is also a longer space before the next wave; all else is normal
Accessory Pathway Tachycardias:
- Rapid heart rhythm due to an extra abnormal pathway or connection between the atria and the ventricles
- Impulses travel through the extra pathways (short cuts) as well as normal AV-HIS Purkinje system
- Shortcuts allow the impulses to travel around the heart very quickly, causing the heart to beat unusually fast
- -Characteristic DELTA WAVE - slurred upstroke of QRS complex
AV Nodal Re-entrant Tachycardia (AVNRT):
Rapid HR due to more than one pathway through the AV node
Atrial tachycardia
Rapid heart rate originating in the atria
Atrial fibrillation
Very common irregular heart rhythm
- Many impulses begin and spread thru the atria, competing for a chance to enter the AV node
- Resulting rhythm is disorganized, rapid, irregular.
- No P waves appear on ECG
- Ventricular rate irregular (irregular time between R waves)
Atrial flutter:
Atrial arrhythmia caused by one or more rapid circuits in the atrium.
- Usually more organized and regular than atrial fibrillation
- “Sawtooth” pattern- looks like blade
What do atrial contractions play little role in?
Ventricular filling
-So atrial fibrillation may be well tolerated by most patients as long as ventricular rate is sufficient to maintain cardiac output
Normal but frequent R waves:
Supraventricular tachycardia
Normal but long PR interval:
First degree heart block
Some independent P
Second degree heart block
P, QRS not in sync
Third degree heart block
No P, QRS irregular
Atrial fibrillation
Bundle Branch Block
(aka hemiblocks)
- Often due to MI
- One part of purkinje system is blocks and doesn’t depolarize in sync with rest of ventricle
- Widening of QRS (>.12 sec)
- Splitting of R-wave (left and right ventricles depolarize separately)
- looks like “bunny ears” 0 forked R wave
Premature ventricular contractions (PVCs):
- Extra beats, beginning in ventricles, feels like heart “skipped a beat”
- Common, tend to be asymptomatic and not need treatment
- Stress, caffeine, exercise
- Cells that normally have pacemaker functions spontaneously depolarize and bring their neighbors with them
- Ventricles depolarize early, followed by missing a beat
- Sometimes caused by heart disease or electrolyte imbalance
- Shapes are variable
Ventricular Tachycardia (V-tach):
Rapid rhythm originating from lower chambers of heart.
- Rapid rate prevents heart from filling adequately – less blood pumped through body
- May have severe symptoms, especially in people with heart disease
- VERY SERIOUS CONDITION
- OFTEN prededes VENTRICULAR FIBRILLATION
Long QT Syndrome
QT = time required for heart muscle to contract and then recover
-When QT is longer, it increases risk of Torsade de points, life threatening tachycardia
Normal: QT should be half or less of total time between R waves
What can Torsades de pointes rapidly become?
Ventricular fibrillation
