When sinus node fails to produce an impulse, another focus in the heart takesover the duty and the ensueing rhyhtm is now called escape rhythm.

  Many different foci in the heart can produce regular impulses to depolarize the ventricles in order to sustain a stable cardiac rhythm.

  The focus with the highest frequency will be the dominant focus.

  In a normal heart, sinus node is the dominant pacemaker and sinus rhythm is the dominant rhythm since sinus node produces impulses with the highest frequency.

  The disease process resulting in escape rhythm is more important than the escape rhythm itself.



Escape rhythms

  Atrial escape rhythm: Every P wave is followed by a QRS complex but shape of the P wave is different than that of the sinus beat. QRS complex is narrow and the heart rate is generally > 60/minute.

  Atrioventricular (AV) nodal rhythm
: No P wave is expected to preceed QRS complex. QRS complexes are narrow. Heart rate is between 40-60/minute.

  Ventricular escape rhythm (idioventricular rhythm)
: Since QRS complexes originate from the ventricles, they are wide, with no preceding P waves. Heart rate is 25-40/minute.





ECG 1. Above is the Holter tracing from a patient with Sick Sinus Syndrome (SSS). There is
nodal escape rhythm . When
P waves originating from the sinus node
does not come at the expected time, nodal rhythm ensues with QRS complexes
lacking
P waves before the QRS complexes .
984 miliseconds (time interval between two sinus beats) < 1375 miliseconds (time interval between two nodal beats):
Nodal escape rhythm is (should be) slower than the sinus rhythm.

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ECG 2. The ECG above belongs to a 9 years-old girl who had previously undergone closure of the atrial septal defect (ASD).
The first four beats from the left are sinus beats .
When the sinus node fails to give impulse in the expected time period
the ectopic atrial focus takes over: atrial escape rhythm .

Pediatric Cardiologist Dr. Mahmut Gokdemir has donated the above ECG to our website.

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ECG 3.
Third degree (complete) AV block and idioventricular rhythm (ventricular escape rhythm) in a 68 years-old woman with Systemic Sclerosis (Scleroderma). Multidetector CT coronary angiography showed normal coronary arteries.

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The ECG above has been used with the permission of Anatolian Journal of Cardiology and AVES Publishing.





ECG 4. Above ECG is from a 81 years-old woman with recent cerebrovascular accident. Complete AV block and idioventricular rhythm (with a ventricular rate of 41/minute) is seen. This ECG has a calibration of
5 mm/mV. P waves may be hard to notice, at first glance. ECG computer inadvertently diagnosed the rhythm as atrial fibrillation. U waves are prominent. This patient was not taking Digoxin.

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ECG 5a. The ECG above belongs to a 95 years-old woman with right bundle branch block. The basic rhythm is atrial fibrillation . Idioventricular rhythm emerged after developing complete AV block. Ventricular rate is 43/minute. P waves are lacking and baseline is oscillating due to atrial fibrillation. However, heart rate is regular since it is determined by the (regular) idioventricular rhythm. This ECG has a standard 10 mm/mV calibration.

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ECG 5b. The above ECG belongs to the same woman. This time its calibration is
20 mm/mV. Now, atrial fibrillation is seen clearly. This ECG shows atrial fibrillation, complete AV block and idioventricular rhythm

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ECG 6a. Above is a 3-channel rhythm tracing from a 87 years-old woman with mild renal impairment. She has been on Digoxin and Metoprolol (beta blocker) therapy for atrial fibrillation. She was consulted to Cardiology because of "bradycardia". At first glance, it may look as if there are P waves with a prolonged PR interval. But the basic rhythm is atrial fibrillation and there are no P waves.
Seemingly P waves are QRS complexes. While monitoring this rhythm, a monitor may sense only the VPCs and may give "bradycardia" alarm. QRS complexes with different morphologies are bidirectional VPCs. If you observe bidirectional VPCs on the ECG of a patient under Digoxin therapy, remember the possibility of Digoxin intoxication. This ECG was recorded at a standard paper speed (25mm/s) and calibration (10 mm/mV).

Dr. Sirli Bulut has donated the above ECG to our website.

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ECG 6b. The above 3-channel ECG tracing belongs to the same patient. It was recorded immediately after the ECG 6a. This ECG also has a calibration of
20 mm/mV at a paper speed of 25mm/s. VPCs with different morphologies are seen. Digoxin increases excitability of myocardial cells (positive bathmotrop). When a patient under Digoxin treatment shows multifocal VPCs and atrial fibrillation with a slow ventricular rate, the possibility of Digoxin intoxication must be remembered. When AV block increases, ventricular escape beats (not ventricular premature beats) start to appear.

Dr. Sirli Bulut has donated the above ECG to our website.

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ECG 6c. The above 3-channel ECG tracing belongs to the same patient. It was recorded immediately after the ECG 6b. Short-lasting idioventricular rhythm emerges due to complete AV block.

Dr. Sirli Bulut has donated the above ECG to our website.

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