ectopic - 'in abnormal place or position' from the Greek 'ektopos' which means "out of place". An ectopic beat occurs from an abnormal site (called an ectopic focus) before the expected time of the next contraction. Ectopic beats (also called extrasystoles or premature contractions) may originate in the atria, the AV junction or the ventricles. There are numerous possible causes of ectopics including local ischaemia, drugs (caffeine is a good example), calcified plaques and physical contact (such as contact of the heart with catheters or surgical instruments).
It is important to be able to identify the origin of ectopic beats, since some forms of ectopics can indicate a predisposition to life-threatening conditions.
This is where things get REALLY interesting!

PVC

This ventricular ectopic - or premature ventricular contraction (PVC) - has had an effect on all three traces in the above diagram: The ECG

	QRS earlier than expected (premature) i.e. shorter RR interval than normal
	QRS wider than normal
	QRS voltage higher than normal
	inverted T wave
	obscured P wave
	next RR interval longer than normal

The arterial pressure

	ejection earlier than expected
	low systolic pressure generated

The CVP

	large a wave
	a wave at expected time(not premature)

Characteristics of (most) PVCs

	wide and bizarre QRS, often with a high voltage and inverted T wave
	reduced or no left ventricular ejection
	large CVP a wave
	fully compensatory pause

PAC

The effect of this atrial ectopic - or premature atrial contraction (PAC) -is different from the effect of a PVC:The EKG

	QRS earlier than expected (premature) i.e. shorter RR interval than normal
	QRS normal shape and magnitude
	normal T wave
	obscured P wave
	next RR interval no longer than normal

The Arterial Pressure

	ejection earlier than expected
	slightly lower systolic pressure generated

The CVP

	large a wave
	a wave before expected time (premature)

Characteristics of (most) PACs

	P wave may be abnormal
	normal QRS complex
	there may or may not be a large CVP a wave
	not a fully compensatory pause

PJC

This junctional ectopic - or premature junctional contraction - has different features from both PVCs and PACs The ECG

	obscured P wave
	QRS earlier than expected (premature) i.e. shorter RR interval than normal
	QRS normal shape and size
	normal T wave
	next RR interval longer than normal

The arterial pressure

	ejection earlier than expected
	lower systolic pressure generated

The CVP

large a wave after the start of the QRS complex (in the ECG)

PJCs are very similar to PACs except for the timing of the a wave, which occurs later than in the case of a PAC, due to the decreased PR interval. The compensatory pause depends on the timing of the PJC with respect to the next firing of the SA node. If the SA node fires before being reset by the ectopic depolarisation, then the pause will be fully compensatory. In most instances the pause will not be fully compensatory.
Characteristics of (most) PJCs

	Decreased PR interval - P waves may not be evident
	normal QRS complex
	there usually will be a large CVP a wave
	may or may not be a fully compensatory pause

PAROXYSMAL TACHYCARDIAS

Paroxysmal...which means "coming in a fit" is the perfect way to describe this sudden onset of tachycardia. They may last only a few seconds or minutes, but sometimes longer, and will usually end as suddenly as it started. Paroxysmal tachycardias are believed to originate in an irritable focus which is repeatedly re-excited, resulting in a rapid heart rate. As with ectopic beats, paroxysmal tachycardias may be classified as ventricular (originating from a ventricle) or supraventricular (originating above the ventricle).

SUPRAVENTRICULAR TACHYCARDIA

This is a sudden onset of tachycardia which results in a decreased mean arterial pressure (due to decreased filling time) Also note that the QRS complexes are not abnormal in shape, indicating a supraventricular irritable focus.

VENTRICULAR TACHYCARDIA

(aka...V-TACH.....my personal favorite!!!!)

See the wide and bizarre QRS complexes, indicating a ventricular origin?

VENTRICULAR FIBRILLATION

Ventricular fibrillation is analogous to atrial fibrillation and similar phenomena are believed to give rise to it. However ventricular fibrillation is a very serious condition because the uncoordinated contractions of ventricular myocardium result in ineffective pumping. If immediate action is not taken the results are fatal.
The following features can be seen in the above diagram :

	random, unrelated waves in the ECG
	lack of significant pulse pressure
	a waves in the CVP trace due to normal atrial contraction

In a person with ventricular fibrillation unconsciousness occurs rapidly, and CPR should be instituted without delay. Electrical defibrillation, by passage of current at high voltage, may be successful in restoration of a normal rhythm.

PACEMAKERS

The heart can be paced electronically via electrodes placed within the chambers of the heart (in the case of chronically implanted pacemakers for patients with a defect in their cardiac conduction system) or attached to the surface of the heart (in the case of short-term pacing following cardiac surgery ). The pacemaker initiates an action potential via the electrodes, and may pace just the atria, just the ventricles or both the atria and the ventricles.
This EKG was recorded just as pacing was started....
Do you see the following?

	normal P, QRS and T waves prior to pacing
	pacing spikes caused by electrical discharge through the right atrium via the pacemaker electrodes
	normal QRS and T waves during pacing, since conduction takes place along the usual pathways

If there is a problem with AV node conduction, then both the atria and the ventricles may be paced. You can see this in the following.....

Do you see the following?

	pacing spikes before both P and QRS waves
	a wide QRS and T complex

In the case of ventricular pacing, the QRS complex may be wide and bizarre, and the T wave may be inverted, as in the case of PVCs. The pacing spikes may not always be obvious, depending on the voltage and the orientation of the pacing electrodes and the ECG leads.

Well, kiddies, that's all TIMONE and I have for you right now!! I promise you I'll keep updating these pages, and info becomes avaiable!!!

If you want to go back to the first ARRYTHMIA page,
then you know what you have to do!!!

Resource Credits:
Nurse-Beat
Hemodynamic Physiology
The Virtual Cardiac Cath Lab